ROTORCRAFT FLYINGHANDBOOK

2000

U.S. DEPARTMENT OF TRANSPORTATIONFEDERAL AVIATION ADMINISTRATION

Flight Standards Service

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PREFACEThe Rotorcraft Flying Handbook is designed as a technical manual for applicants who are preparing fortheir private, commercial, or flight instructor pilot certificates with a helicopter or gyroplane class rating.Certificated flight instructors may find this handbook a valuable training aid, since detailed coverage ofaerodynamics, flight controls, systems, performance, flight maneuvers, emergencies, and aeronauticaldecision making is included. Topics, such as weather, navigation, radio navigation and communications,use of flight information publications, and regulations are available in other Federal AviationAdministration (FAA) publications.

This handbook conforms to pilot training and certification concepts established by the FAA. There aredifferent ways of teaching, as well as performing flight procedures and maneuvers, and many variationsin the explanations of aerodynamic theories and principles. This handbook adopts a selective methodand concept to flying helicopters and gyroplanes. The discussion and explanations reflect the most com-monly used practices and principles. Occasionally, the word “must” or similar language is used wherethe desired action is deemed critical. The use of such language is not intended to add to, interpret, orrelieve a duty imposed by Title 14 of the Code of Federal Regulations (14 CFR). This handbook is divid-ed into two parts. The first part, chapters 1 through 14, covers helicopters, and the second part, chapters 15 through 22, covers gyroplanes. The glossary and indexapply to both parts.

It is essential for persons using this handbook to also become familiar with and apply the pertinent partsof 14 CFR and the Aeronautical Information Manual (AIM). Performance standards for demonstratingcompetence required for pilot certification are prescribed in the appropriate rotorcraft practical test stan-dard.

This handbook supersedes Advisory Circular (AC) 61-13B, Basic Helicopter Handbook, dated 1978. Inaddition, all or part of the information contained in the following advisory circulars are included in thishandbook: AC 90-87, Helicopter Dynamic Rollover; AC 90-95, Unanticipated Right Yaw in Helicopters;AC 91-32B, Safety in and around Helicopters; and AC 91-42D, Hazards of Rotating Propeller andHelicopter Rotor Blades.

This publication may be purchased from the Superintendent of Documents, U.S. Government PrintingOffice (GPO), Washington, DC 20402-9325, or from U.S. Government Bookstores located in major citiesthroughout the United States.

The current Flight Standards Service airman training and testing material and subject matter knowledge codes for all airman certificates and ratings can be obtained from the Flight Standards Services web sitea thttp://av-info.faa.gov.

Comments regarding this handbook should be sent to U.S. Department of Transportation, FederalAviation Administration, Airman Testing Standards Branch, AFS-630, P.O. Box 25082, Oklahoma City,OK 73125.

AC 00-2, Advisory Circular Checklist, transmits the current status of FAA advisory circulars and otherflight information publications. This checklist is free of charge and may be obtained by sending a requestto U.S. Department of Transportation, Subsequent Distribution Office, SVC-121.23, Ardmore EastBusiness Center, 3341 Q 75th Avenue, Landover, MD 20785.

AC00-2 also is available on the Internet at http://www.faa.gov/abc/ac-chklst/actoc.htm.

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Autorotation (Forward Flight).....................3-11

Chapter 4—Helicopter Flight ControlsCollective Pitch Control ...................................4-1Throttle Control................................................4-1Collective Pitch / Throttle Coordination ...........4-2Correlator / Governor ......................................4-2Cyclic Pitch Control .........................................4-2Antitorque Pedals ............................................4-3

Heading Control ..........................................4-3

Chapter 5—Helicopter SystemsEngines ...........................................................5-1

Reciprocating Engine ..................................5-1Turbine Engine ............................................5-1

Compressor.............................................5-2Combustion Chamber .............................5-2Turbine ....................................................5-2

Transmission System......................................5-3Main Rotor Transmission ............................5-3Tail Rotor Drive System ..............................5-3Clutch ..........................................................5-4

Centrifugal Clutch....................................5-4Belt Drive Clutch .....................................5-4Freewheeling Unit ...................................5-4

Main Rotor System..........................................5-4Fully Articulated Rotor System....................5-4Semirigid Rotor System ..............................5-5Rigid Rotor System.....................................5-5Combination Rotor Systems .......................5-5Swash Plate Assembly................................5-5

Fuel Systems...................................................5-6Fuel Supply System ....................................5-6Engine Fuel Control System .......................5-6

Reciprocating Engines ............................5-7Carburetor ...........................................5-7Carburetor Ice .....................................5-7Fuel Injection .......................................5-8

Turbine Engines ......................................5-8Electrical Systems ...........................................5-8Hydraulics .............................................................5-9Stability Augmentations Systems ..................5-10Autopilot ........................................................5-10Environmental Systems.................................5-10Anti-Icing Systems.........................................5-11

Chapter 6—Rotorcraft Flight Manual (Helicopter)Preliminary Pages ................................................6-1General Information.........................................6-1

HELICOPTERChapter 1—Introduction to the HelicopterThe Main Rotor System ..................................1-1

Fully Articulated Rotor System....................1-1Semirigid Rotor System ..............................1-2Rigid Rotor System .....................................1-2

Antitorque Systems .........................................1-2Tail Rotor .....................................................1-2Fenestron ....................................................1-2NOTAR® .....................................................1-2

Landing Gear...................................................1-2Powerplant............................................................1-3Flight Controls .................................................1-3

Chapter 2—General AerodynamicsAirfoil ...............................................................2-1

Relative Wind ..............................................2-2Blade Pitch Angle ........................................2-2Angle of Attack ............................................2-2

Lift....................................................................2-3Magnus Effect .............................................2-3Bernoulli’s Principle .....................................2-3Newton’s Third Law of Motion .....................2-4

Weight .............................................................2-4Thrust ..............................................................2-5Drag.................................................................2-5

Profile Drag .................................................2-5Induced Drag...............................................2-5Parasite Drag ..............................................2-6Total Drag....................................................2-6

Chapter 3—Aerodynamics of FlightPowered Flight ................................................3-1Hovering Flight ................................................3-1

Translating Tendency or Drift ......................3-1Pendular Action ...........................................3-2Coning .........................................................3-2Coriolis Effect (Law of Conservation of Angular Momentum) ....................................3-2Ground Effect ..............................................3-3Gyroscopic Precession ...............................3-4

Vertical Flight...................................................3-4Forward Flight .................................................3-5

Translational Lift ..........................................3-5Induced Flow ...............................................3-6Transverse Flow Effect................................3-6Dissymmetry of Lift......................................3-6

Sideward Flight................................................3-8Rearward Flight ...............................................3-8Turning Flight ..................................................3-8Autorotation .....................................................3-8

Autorotation (Vertical Flight)........................3-9

CONTENTS

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Operating Limitations ......................................6-1Airspeed Limitation......................................6-1Altitude Limitations ......................................6-2Rotor Limitations .........................................6-2Powerplant Limitations ................................6-2Weight and Loading Distribution .................6-2Flight Limitations .........................................6-3Placards............................................................

6-3Emergency Procedures ...................................6-3Normal Procedures .........................................6-3Performance ....................................................6-3Weight and Balance ........................................6-4Aircraft and Systems Description ....................6-4Handling, Servicing, and Maintenance............6-4Supplements ...................................................6-4Safety and Operational Tips ............................6-4

Chapter 7—Weight and BalanceWeight .............................................................7-1

Basic Empty Weight ....................................7-1Useful Load .................................................7-1Payload.............................................................

7-1Gross Weight...............................................7-1Maximum Gross Weight ..............................7-1Weight Limitations .......................................7-1Determining Empty Weight .........................7-1

Balance.................................................................7-2

Center of Gravity .........................................7-2CG Forward of Forward Limit .................7-2CG Aft of Aft Limit....................................7-2

Lateral Balance ...........................................7-3Weight and Balance Calculations ...................7-3

Reference Datum........................................7-3Arm..............................................................7-4Moment.............................................................

7-4Center of Gravity Computation ...................7-4

Weight and Balance Methods .........................7-4Computational Method ................................7-4Loading Chart Method.................................7-5

Sample Problem 1 ..................................7-5Sample Problem 2 ..................................7-5Sample Problem 3 ..................................7-6

Combination Method ...................................7-6Calculating Lateral CG................................7-7

Chapter 8—PerformanceFactors Affecting Performance ........................8-1

Density Altitude ...........................................8-1Atmospheric Pressure.................................8-1Altitude ........................................................8-2Temperature ................................................8-2

Moisture (Humidity) .....................................8-2High and Low Density Altitude Conditions ..8-2Weight .........................................................8-2Winds ..........................................................8-2

Performance Charts ........................................8-3Hovering Performance ................................8-3

Sample Problem 1 ..................................8-4Sample Problem 2 ..................................8-4

Takeoff Performance ...................................8-5Sample Problem 3 ..................................8-5

Climb Performance .....................................8-5Sample Problem 4 ..................................8-6

Chapter 9—Basic Flight ManeuversPreflight ...........................................................9-1

Minimum Equipment Lists (MELS) andOperations With Inoperative Equipment .....9-1

Engine Start and Rotor Engagement ..............9-2Rotor Safety Considerations .......................9-2Safety In and Around Helicopters ...............9-3

Ramp Attendants and Aircraft Servicing Personnel ................................9-3Aircraft Servicing .....................................9-3External-Load Riggers ............................9-3Pilot at the Flight Controls.......................9-3External-Load Hookup Personnel ...........9-3Passengers .............................................9-4

Vertical Takeoff to a Hover ..............................9-5Technique ....................................................9-5Common Errors...........................................9-5

Hovering ..........................................................9-5Technique ....................................................9-5Common Errors...........................................9-5

Hovering Turn..................................................9-6Technique ....................................................9-6Common Errors...........................................9-7

Hovering—Forward Flight ...............................9-7Technique ....................................................9-7Common Errors...........................................9-7

Hovering—Sideward Flight..............................9-7Technique ....................................................9-7Common Errors...........................................9-8

Hovering—Rearward Flight .............................9-8Technique ....................................................9-8Common Errors...........................................9-8

Taxiing .............................................................9-8Hover Taxi ...................................................9-9Air Taxi.........................................................9-9

Technique ................................................9-9Common Errors.......................................9-9

Surface Taxi.................................................9-9Technique ................................................9-9Common Errors.....................................9-10

Normal Takeoff From a Hover .......................9-10

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Technique ..................................................9-10Common Errors.........................................9-10

Normal Takeoff From the Surface .................9-11Technique ..................................................9-11Common Errors .........................................9-11Crosswind ConsiderationsDuring Takeoffs..........................................9-11

Straight-and-Level Flight ...............................9-12Technique ..................................................9-12Common Errors.........................................9-12

Turns .............................................................9-12Technique ..................................................9-12Slips ...........................................................9-13Skids .................................................................

9-13Common Errors.........................................9-13

Normal Climb.................................................9-13Technique ..................................................9-13Common Errors.........................................9-14

Normal Descent.............................................9-14Technique ..................................................9-14Common Errors.........................................9-14

Ground Reference Maneuvers......................9-14Rectangular Course ..................................9-14S-Turns .............................................................

9-16Turns Around a Point ................................9-17Common Errors During Ground Reference Maneuvers ...............................9-18

Traffic Patterns ..............................................9-18Approaches ...................................................9-19

Normal Approach to a Hover.....................9-19Technique ..............................................9-19Common Errors.....................................9-19

Normal Approach to the Surface...............9-20Technique ..............................................9-20Common Errors.....................................9-20

Crosswind During Approaches..................9-20Go-Around .....................................................9-20After Landing and Securing...........................9-20Noise Abatement Procedures .......................9-20

Chapter 10—Advanced ManeuversReconnaissance Procedures ........................10-1

High Reconnaissance ...............................10-1Low Reconnaissance ................................10-1Ground Reconnaissance...........................10-1

Maximum Performance Takeoff.....................10-2Technique ..................................................10-2Common Errors.........................................10-2

Running/Rolling Takeoff ................................10-2Technique ..................................................10-3Common Errors.........................................10-3

Rapid Deceleration (Quick Stop)...................10-3Technique ..................................................10-3

Common Errors.........................................10-4Steep Approach to a Hover ...........................10-4

Technique ..................................................10-4Common Errors.........................................10-5

Shallow Approach and Running/Roll-On Landing.................................................................10-5

Technique ..................................................10-5Common Errors.........................................10-5

Slope Operations...........................................10-6Slope Landing ...........................................10-6

Technique .............................................10-6Common Errors ....................................10-6

Slope Takeoff .............................................10-6Technique .............................................10-7Common Errors ....................................10-7

Confined Area Operations.............................10-7Approach...................................................10-7Takeoff.......................................................10-8Common Errors.........................................10-8

Pinnacle and Ridgeline Operations...............10-8Approach and Landing..............................10-8Takeoff.......................................................10-9Common Errors.........................................10-9

Chapter 11—Helicopter EmergenciesAutorotation ...................................................11-1

Straight-in Autorotation ..............................11-2Technique..............................................11-2Common Errors.....................................11-3

Power Recovery From Practice Autorotation ...............................................11-3

Technique..............................................11-3Common Errors.....................................11-3

Autorotation With Turns .............................11-3Technique..............................................11-3

Power Failure in a Hover...........................11-4Technique..............................................11-4Common Errors.....................................11-4

Height/Velocity Diagram ................................11-4The Effect of Weight Versus Density Altitude..........................................11-5

Vortex Ring State (Settling With Power)........11-5Retreating Blade Stall ....................................11-6Ground Resonance .......................................11-7Dynamic Rollover ..........................................11-7

Critical Conditions......................................11-8Cyclic Trim.................................................11-8Normal Takeoffs and Landings..................11-8Slope Takeoffs and Landings ....................11-8Use of Collective .......................................11-9Precautions................................................11-9

Low G Conditions and Mast Bumping.........11-10Low Rotor RPM and Blade Stall..................11-10Recovery From Low Rotor RPM .................11-10

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Systems Malfunctions..................................11-11Antitorque System Failure .......................11-11

Landing—Stuck Left Pedal..................11-11Landing—Stuck Neutral or Right Pedal..........................................11-12

Unanticipated Yaw / Loss of Tail RotorEffectiveness (LTE) .................................11-12Main Rotor Disc Interference (285-315°)................................................11-12Weathercock Stability(120-240°)................................................11-13Tail Rotor Vortex Ring State (210-330°)................................................11-13

LTE at Altitude.....................................11-13Reducing the Onset of LTE.................11-13Recovery Technique ...........................11-14

Main Drive Shaft Failure..........................11-14Hydraulic Failures ....................................11-14Governor Failure .....................................11-14Abnormal Vibrations ................................11-14

Low Frequency Vibrations ..................11-15Medium and High Frequency Vibrations.............................................11-15Tracking and Balance .........................11-15

Flight Diversion............................................11-15Lost Procedures ..........................................11-16Emergency Equipment and Survival Gear ..11-16

Chapter 12—Attitude Instrument FlyingFlight Instruments .................................................12-1

Pitot-Static Instruments .............................12-1Airspeed Indicator.................................12-1Instrument Check..................................12-1Altimeter................................................12-2

Instrument Check..............................12-2Vertical Speed Indicator ............................12-2

Instrument Check..................................12-2System Errors .......................................12-2

Gyroscopic Instruments ............................12-3Attitude Indicator ...................................12-3Heading Indicator..................................12-3Turn Indicators ......................................12-4Instrument Check..................................12-4

Magnetic Compass ...................................12-4Compass Errors ....................................12-4Magnetic Variation ................................12-4

Compass Deviation...........................12-5Magnetic Dip .....................................12-5Instrument Check..............................12-5

Instrument Flight............................................12-5Instrument Cross-Check ...........................12-5Instrument Interpretation ...........................12-6Aircraft Control ..........................................12-7

Straight-and-Level Flight ...........................12-7Pitch Control .........................................12-7

Attitude Indicator ...............................12-8Altimeter............................................12-8Vertical Speed Indicator ....................12-8Airspeed Indicator .............................12-9

Bank Control .........................................12-9Attitude Indicator ...............................12-9Heading Indicator............................12-10Turn Indicator ..................................12-10

Common Errors During Straight-and-Level Flight .....................12-10Power Control During Straight-and-Level Flight .....................12-11Common Errors During Airspeed Changes...............................12-11

Straight Climbs (Constant Airspeed and Constant Rate) .................................12-11

Entry ...................................................12-12Leveloff ...............................................12-14

Straight Descents (Constant Airspeed and Constant Rate) ........................................12-14

Entry ...................................................12-14Leveloff ...............................................12-15Common Errors During Straight Climbs and Descents .............12-15

Turns .......................................................12-15Turns to a Predetermined Heading ....12-16Timed Turns ........................................12-16

Change of Airspeed in Turns ..........12-1630° Bank Turn .....................................12-17Climbing and Descending Turns.........12-17Compass Turns...................................12-17Common Errors During Turns.............12-18

Unusual Attitudes ....................................12-18Common Errors During Unusual Attitude Recoveries .............................12-18

Emergencies ...............................................12-18Autorotations ...........................................12-19

Common Errors During Autorotations .......................................12-19

Servo Failure ...........................................12-19Instrument Takeoff .......................................12-19

Common Errors During Instrument Takeoffs .................................12-20

Chapter 13—Night OperationsNight Flight Physiology..................................13-1

Vision in Flight...........................................13-1The Eye ............................................................

13-1Cones ........................................................13-1Rods .................................................................

13-2

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Night Vision ...............................................13-2Night Scanning..........................................13-2Aircraft Lighting .........................................13-3Visual Illusions ..........................................13-3

Autokinesis ...........................................13-3Night Myopia.........................................13-3False Horizon........................................13-3Landing Illusions ...................................13-4

Night Flight ....................................................13-4Preflight .....................................................13-4Engine Starting and Rotor Engagement ...13-4Taxi Technique ..........................................13-4Takeoff.......................................................13-4En route Procedures .................................13-5Collision Avoidance at Night .....................13-5Approach and Landing ..............................13-5

Chapter 14—Aeronautical Decision MakingOrigins of ADM Training ................................14-2The Decision-Making Process ......................14-3

Defining the Problem.................................14-3Choosing a Course of Action ....................14-3Implementing the Decision and Evaluating the Outcome............................14-3

Risk Management .........................................14-4Assessing Risk..........................................14-4

Factors Affecting Decision Making ................14-5Pilot Self-Assessment ...............................14-5Recognizing Hazardous Attitudes .............14-5Stress management ..................................14-6Use of Resources......................................14-6

Internal Resources ................................14-7External Resources...............................14-7

Workload Management .............................14-7Situational Awareness ...............................14-8

Obstacles to Maintaining Situational Awareness ...........................14-8Operational Pitfalls ................................14-8

GYROPLANEChapter 15—Introduction to the GyroplaneTypes of Gyroplanes .....................................15-1Components ..................................................15-2

Airframe.....................................................15-2Powerplant ................................................15-2Rotor System ............................................15-2Tail Surfaces..............................................15-2Landing Gear ............................................15-3Wings ........................................................15-3

Chapter 16—Aerodynamics of the Gyroplane

Autorotation ...................................................16-1Vertical Autorotation ..................................16-1Rotor Disc Regions ...................................16-2Autorotation in Forward Flight ...................16-2

Reverse Flow ........................................16-3Retreating Blade Stall ...........................16-3

Rotor Force ...................................................16-3Rotor Lift....................................................16-4Rotor Drag.................................................16-4

Thrust ............................................................16-4Stability .................................................................16-5

Horizontal Stabilizer...................................16-5Fuselage Drag (Center of Pressure).........16-5Pitch Inertia ...............................................16-5Propeller Thrust Line.................................16-5Rotor Force ...............................................16-6Trimmed Condition ....................................16-6

Chapter 17—Gyroplane Flight ControlsCyclic Control ................................................17-1Throttle ..........................................................17-1Rudder...........................................................17-2Horizontal Tail Surfaces.................................17-2Collective Control ..........................................17-2

Chapter 18—Gyroplane SystemsPropulsion Systems.......................................18-1Rotor Systems...............................................18-1

Semirigid Rotor System ............................18-1Fully Articulated Rotor System..................18-1

Prerotator ......................................................18-2Mechanical Prerotator ...............................18-2Hydraulic Prerotator ..................................18-2Electric Prerotator .....................................18-3Tip Jets .............................................................

18-3Instrumentation..............................................18-3

Engine Instruments ...................................18-3Rotor Tachometer......................................18-3Slip/Skid Indicator .....................................18-4Airspeed Indicator .....................................18-4Altimeter ....................................................18-4IFR Flight Instrumentation.........................18-4

Ground Handling ...........................................18-4

Chapter 19—Rotorcraft Flight Manual(Gyroplane)

Using the Flight Manual ................................19-1Weight and Balance Section.....................19-1

Sample Problem....................................19-1Performance Section .................................19-2

Sample Problem....................................19-2Height/Velocity Diagram........................19-3

Emergency Section ...................................19-3

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Hang Test ......................................................19-4

Chapter 20—Flight OperationsPreflight .........................................................20-1

Cockpit Management ................................20-1Engine Starting ..............................................20-1Taxiing ...........................................................20-1

Blade Flap .................................................20-1Before Takeoff ...............................................20-2

Prerotation .................................................20-2Takeoff ...........................................................20-3

Normal Takeoff ..........................................20-3Crosswind Takeoff .....................................20-4Common Errors for Normal and Crosswind Takeoffs ...................................20-4Short-Field Takeoff ....................................20-4

Common Errors.....................................20-4High-Altitude Takeoff .............................20-4

Soft-Field Takeoff ......................................20-5Common Errors.....................................20-5Jump Takeoff.........................................20-5

Basic Flight Maneuvers.................................20-6Straight-and-Level Flight ...........................20-6Climbs .......................................................20-6Descents ...................................................20-7Turns .........................................................20-7

Slips ......................................................20-7Skids.............................................................

20-7Common Errors During Basic

Flight Maneuvers.......................................20-8Steep Turns ...............................................20-8

Common Errors.....................................20-8Ground Reference Maneuvers......................20-8

Rectangular Course ..................................20-8S-Turns .............................................................

20-10Turns Around a Point...............................20-11Common Errors During Ground Reference Maneuvers ................20-11

Flight at Slow Airspeeds..............................20-12Common Errors.......................................20-12

High Rate of Descent ..................................20-12Common Errors.......................................20-13

Landings......................................................20-13Normal Landing.......................................20-13Short-Field Landing.................................20-13Soft-Field Landing ...................................20-14Crosswind Landing..................................20-14High-Altitude Landing ..............................20-14Common Errors During Landing .............20-15

Go-Around ...................................................20-15Common Errors.......................................20-15

After Landing and Securing.........................20-15

Chapter 21—Gyroplane EmergenciesAborted Takeoff .............................................21-1

Accelerate/Stop Distance ..........................21-1Lift-off at Low Airspeed andHigh Angle of Attack ......................................21-1

Common Errors.........................................21-2Pilot-Induced Oscillation (PIO) ......................21-2Buntover (Power Pushover) ..........................21-3Ground Resonance .......................................21-3Emergency Approach and Landing...............21-3Emergency Equipment and Survival Gear ....21-4

Chapter 22—Gyroplane Aeronautical DecisionMaking

Impulsivity......................................................22-1Invulnerability ................................................22-1Macho............................................................22-2Resignation ...................................................22-2Anti-Authority.................................................22-3

Glossary .........................................................G-1

Index .................................................................I-1

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Helicopters come in many sizes and shapes, butmost share the same major components. Thesecomponents include a cabin where the payloadand crew are carried; an airframe, which housesthe various components, or where componentsare attached; a powerplant or engine; and a trans-mission, which, among other things, takes thepower from the engine and transmits it to the mainrotor, which provides the aerodynamic forces thatmake the helicopter fly. Then, to keep the helicop-ter from turning due to torque, there must be sometype of antitorque system. Finally there is the land-ing gear, which could be skids, wheels, skis, or

floats. This chapter is an introduction to thesecomponents. [Figure 1-1]

THE MAIN ROTOR SYSTEMThe rotor system found on helicopters can consistof a single main rotor or dual rotors. With mostdual rotors, the rotors turn in opposite directionsso the torque from one rotor is opposed by thetorque of the other. This cancels the turningtendencies. [Figure 1-2]

In general, a rotor system can be classified aseither fully articulated, semirigid, or rigid. Thereare variations and combinations of these systems,which will be discussed in greater detail in Chapter5—Helicopter Systems.

FULLY ARTICULATED ROTOR SYSTEMA fully articulated rotor system usually consists ofthree or more rotor blades. The blades areallowed to flap, feather, and lead or lag independ-ently of each other. Each rotor blade is attached tothe rotor hub by a horizontal hinge, called the flap-ping hinge, which permits the blades to flap upand down. Each blade can move up and down

Payload—The term used for pas-sengers, baggage, and cargo.

Torque—In helicopters with a sin-gle, main rotor system, the ten-dency of the helicopter to turn inthe opposite direction of the mainrotor rotation.

Blade Flap—The upward ordownward movement of the rotorblades during rotation.

Blade Feather or Feathering—The rotation of the blade aroundthe spanwise (pitch change) axis.

Blade Lead or Lag—The foreand aft movement of the blade inthe plane of rotation. It is some-times called hunting or dragging.

Figure 1-2. Helicopters can have a single main rotor or a dual rotor system.

Figure 1-1. The major components of a helicopter are the cabin,airframe, landing gear, powerplant, transmission, main rotor sys-tem, and tail rotor system.

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independently of the others. The flapping hingemay be located at varying distances from the rotorhub, and there may be more than one. The posi-tion is chosen by each manufacturer, primarilywith regard to stability and control.

Each rotor blade is also attached to the hub by avertical hinge, called a drag or lag hinge, that per-mits each blade, independently of the others, tomove back and forth in the plane of the rotor disc.Dampers are normally incorporated in the designof this type of rotor system to prevent excessivemotion about the drag hinge. The purpose of thedrag hinge and dampers is to absorb the acceler-ation and deceleration of the rotor blades.

The blades of a fully articulated rotor can also befeathered, or rotated about their spanwise axis. Toput it more simply, feathering means the changingof the pitch angle of the rotor blades.

SEMIRIGID ROTOR SYSTEMA semirigid rotor system allows for two differentmovements, flapping and feathering. This systemis normally comprised of two blades, which arerigidly attached to the rotor hub. The hub is thenattached to the rotor mast by a trunnion bearing orteetering hinge. This allows the blades to see-sawor flap together. As one blade flaps down, theother flaps up. Feathering is accomplished by thefeathering hinge, which changes the pitch angle ofthe blade.

RIGID ROTOR SYSTEMThe rigid rotor system is mechanically simple, butstructurally complex because operating loadsmust be absorbed in bending rather than throughhinges. In this system, the blades cannot flap orlead and lag, but they can be feathered.

ANTITORQUE SYSTEMSTAIL ROTORMost helicopters with a single, main rotor systemrequire a separate rotor to overcome torque. This isaccomplished through a variable pitch, antitorquerotor or tail rotor. [Figure 1-3]. You will need to varythe thrust of the antitorque system to maintaindirectional control whenever the main rotor torquechanges, or to make heading changes while hov-ering.

FENESTRONAnother form of antitorque rotor is the fenestron or“fan-in-tail” design. This system uses a series ofrotating blades shrouded within a vertical tail.Because the blades are located within a circularduct, they are less likely to come into contact withpeople or objects. [Figure 1-4]

NOTAR®The NOTAR® system is an alternative to the anti-torque rotor. The system uses low-pressure airthat is forced into the tailboom by a fan mountedwithin the helicopter. The air is then fed throughhorizontal slots, located on the right side of thetailboom, and to a controllable rotating nozzle toprovide antitorque and directional control. Thelow-pressure air coming from the horizontal slots,in conjunction with the downwash from the mainrotor, creates a phenomenon called “CoandaEffect,” which produces a lifting force on the rightside of the tailboom. [Figure 1-5]

LANDING GEARThe most common landing gear is a skid typegear, which is suitable for landing on various typesof surfaces. Some types of skid gear are equippedwith dampers so touchdown shocks or jolts are nottransmitted to the main rotor system. Other types

Figure 1-3. The antitorque rotor produces thrust to oppose torqueand helps prevent the helicopter from turning in the oppositedirection of the main rotor.

Figure 1-4. Compared to an unprotected tail rotor, the fenestronantitorque system provides an improved margin of safety duringground operations.

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absorb the shocks by the bending of the skidattachment arms. Landing skids may be fitted withreplaceable heavy-duty skid shoes to protectthem from excessive wear and tear.

Helicopters can also be equipped with floats forwater operations, or skis for landing on snow orsoft terrain. Wheels are another type of landinggear. They may be in a tricycle or four point con-figuration. Normally, the nose or tail gear is free toswivel as the helicopter is taxied on the ground.

POWERPLANTA typical small helicopter has a reciprocatingengine, which is mounted on the airframe. Theengine can be mounted horizontally or verticallywith the transmission supplying the power to thevertical main rotor shaft. [Figure 1-6]

Another engine type is the gas turbine. Thisengine is used in most medium to heavy lift heli-copters due to its large horsepower output. Theengine drives the main transmission, which thentransfers power directly to the main rotor system,as well as the tail rotor.

Figure 1-5. While in a hover, Coanda Effect supplies approxi-mately two-thirds of the lift necessary to maintain directional con-trol. The rest is created by directing the thrust from the controllablerotating nozzle.

Figure 1-6. Typically, the engine drives the main rotor through atransmission and belt drive or centrifugal clutch system. The anti-torque rotor is driven from the transmission.

Figure 1-7. Location of flight controls.

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FLIGHT CONTROLSWhen you begin flying a helicopter, you will usefour basic flight controls. They are the cyclic pitchcontrol; the collective pitch control; the throttle,which is usually a twist grip control located onthe end of the collective lever; and the anti -torque pedals. The collective and cyclic controlsthe pitch of the main rotor blades. The function ofthese controls will be explained in detail inChapter 4—Flight Controls. [Figure 1-7]

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There are four forces acting on a helicopter inflight. They are lift, weight, thrust, and drag.[Figure 2-1] Lift is the upward force created by theeffect of airflow as it passes around an airfoil.Weight opposes lift and is caused by the down-ward pull of gravity. Thrust is the force that propelsthe helicopter through the air. Opposing lift andthrust is drag, which is the retarding force created

by development of lift and the movement of anobject through the air.

AIRFOILBefore beginning the discussion of lift, you needto be aware of certain aerodynamic terms thatdescribe an airfoil and the interaction of the air-flow around it.

An airfoil is any surface, such as an airplane wingor a helicopter rotor blade, which provides aerody-namic force when it interacts with a moving streamof air. Although there are many different rotorblade airfoil designs, in most helicopter flight con-ditions, all airfoils perform in the same manner.

Engineers of the first helicopters designed rela-tively thick airfoils for their structural characteris-tics. Because the rotor blades were very long andslender, it was necessary to incorporate morestructural rigidity into them. This prevented exces-

sive blade droop when the rotor system was idle,and minimized blade twisting while in flight. Theairfoils were also designed to be symmetrical,which means they had the same camber (curva-ture) on both the upper and lower surfaces.Symmetrical blades are very stable, which helpskeep blade twisting and flight control loads to aminimum. [Figure 2-2] This stability is achievedby keeping the center of pressure virtuallyunchanged as the angle of attack changes. Centerof pressure is the imaginary point on the chord linewhere the resultant of all aerodynamic forces areconsidered to be concentrated.

Today, designers use thinner airfoils and obtain therequired rigidity by using composite materials. Inaddition, airfoils are asymmetrical in design, mean-ing the upper and lower surface do not have thesame camber. Normally these airfoils would not beas stable, but this can be corrected by bending thetrailing edge to produce the same characteristicsas symmetrical airfoils. This is called “reflexing.”Using this type of rotor blade allows the rotor sys-tem to operate at higher forward speeds.

One of the reasons an asymmetrical rotor blade isnot as stable is that the center of pressurechanges with changes in angle of attack. Whenthe center of pressure lifting force is behind thepivot point on a rotor blade, it tends to cause therotor disc to pitch up. As the angle of attackincreases, the center of pressure moves forward.If it moves ahead of the pivot point, the pitch of the

Figure 2-2. The upper and lower curvatures are the same on asymmetrical airfoil and vary on an asymmetrical airfoil.

Figure 2-1. Four forces acting on a helicopter in forward flight.

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rotor disc decreases. Since the angle of attack ofthe rotor blades is constantly changing duringeach cycle of rotation, the blades tend to flap,feather, lead, and lag to a greater degree.

When referring to an airfoil, the span is the dis-tance from the rotor hub to the blade tip. Bladetwist refers to a changing chord line from the bladeroot to the tip. Twisting a rotor blade causes it toproduce a more even amount of lift along its span.This is necessary because rotational velocityincreases toward the blade tip. The leading edgeis the first part of the airfoil to meet the oncomingair. [Figure 2-3] The trailing edge is the aft portionwhere the airflow over the upper surface joins theairflow under the lower surface. The chord line isan imaginary straight line drawn from the leadingto the trailing edge. The camber is the curvature ofthe airfoil’s upper and lower surfaces. The relativewind is the wind moving past the airfoil. The direc-tion of this wind is relative to the attitude, or posi-tion, of the airfoil and is always parallel, equal, andopposite in direction to the flight path of the airfoil.The angle of attack is the angle between the bladechord line and the direction of the relative wind.

RELATIVE WINDRelative wind is created by the motion of an airfoilthrough the air, by the motion of air past an airfoil,or by a combination of the two. Relative wind maybe affected by several factors, including the rota-tion of the rotor blades, horizontal movement of thehelicopter, flapping of the rotor blades, and windspeed and direction.

For a helicopter, the relative wind is the flow of airwith respect to the rotor blades. If the rotor isstopped, wind blowing over the blades creates arelative wind. When the helicopter is hovering in ano-wind condition, relative wind is created by themotion of the rotor blades through the air. If thehelicopter is hovering in a wind, the relative windis a combination of the wind and the motion of therotor blades through the air. When the helicopteris in forward flight, the relative wind is a combina-tion of the rotation of the rotor blades and the for-ward speed of the helicopter.

BLADE PITCH ANGLEThe pitch angle of a rotor blade is the angle betweenits chord line and the reference plane containing therotor hub. [Figure 2-4] You control the pitch angle ofthe blades with the flight controls. The collectivepitch changes each rotor blade an equal amount ofpitch no matter where it is located in the plane ofrotation (rotor disc) and is used to change rotorthrust. The cyclic pitch control changes the pitch ofeach blade as a function of where it is in the plane ofrotation. This allows for trimming the helicopter inpitch and roll during forward flight and for maneu-vering in all flight conditions.

ANGLE OF ATTACKWhen the angle of attack is increased, air flowingover the airfoil is diverted over a greater distance,resulting in an increase of air velocity and morelift. As angle of attack is increased further, itbecomes more difficult for air to flow smoothlyacross the top of the airfoil. At this point the airflowbegins to separate from the airfoil and enters aburbling or turbulent pattern. The turbulence

Axis-of-Rotation—The imaginaryline about which the rotor rotates.It is represented by a line drawnthrough the center of, and per-pendicular to, the tip-path plane.

Tip-Path Plane—The imaginarycircular plane outlined by therotor blade tips as they make acycle of rotation.

Aircraft Pitch—When referencedto a helicopter, is the movementof the helicopter about its lateral,or side to side axis. Movement ofthe cyclic forward or aft causes

the nose of the helicopter tomove up or down.

Aircraft Roll—Is the movement ofthe helicopter about its longitudi-nal, or nose to tail axis.

Figure 2-3. Aerodynamic terms of an airfoil.

Figure 2-4. Do not confuse the axis of rotation with the rotor mast.The only time they coincide is when the tip-path plane is perpen-dicular to the rotor mast.

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results in a large increase in drag and loss of lift inthe area where it is taking place. Increasing theangle of attack increases lift until the critical angleof attack is reached. Any increase in the angle ofattack beyond this point produces a stall and arapid decrease in lift. [Figure 2-5]

Angle of attack should not be confused with pitchangle. Pitch angle is determined by the directionof the relative wind. You can, however, change theangle of attack by changing the pitch anglethrough the use of the flight controls. If the pitchangle is increased, the angle of attack isincreased, if the pitch angle is reduced, the angleof attack is reduced. [Figure 2-6]

LIFTMAGNUS EFFECTThe explanation of lift can best be explained bylooking at a cylinder rotating in an airstream. Thelocal velocity near the cylinder is composed of theairstream velocity and the cylinder’s rotationalvelocity, which decreases with distance from thecylinder. On a cylinder, which is rotating in such away that the top surface area is rotating in the samedirection as the airflow, the local velocity at the sur-face is high on top and low on the bottom.

As shown in figure 2-7, at point “A,” a stagnationpoint exists where the airstream line that impingeson the surface splits; some air goes over andsome under. Another stagnation point exists at

“B,” where the two air streams rejoin and resumeat identical velocities. We now have upwashahead of the rotating cylinder and downwash atthe rear.

Figure 2-6. Angle of attack may be greater than, less than, or thesame as the pitch angle.

Figure 2-5. As the angle of attack is increased, the separationpoint starts near the trailing edge of the airfoil and progresses for-ward. Finally, the airfoil loses its lift and a stall condition occurs.

Figure 2-7. Magnus Effect is a lifting force produced when a rotat-ing cylinder produces a pressure differential. This is the sameeffect that makes a baseball curve or a golf ball slice.

Figure 2-8. Air circulation around an airfoil occurs when the frontstagnation point is below the leading edge and the aft stagnationpoint is beyond the trailing edge.

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Steady-State Flight—A conditionwhen an aircraft is in straight-and-level, unaccelerated flight,and all forces are in balance.

the airfoil causes an increase in the speed of theairflow. The increased speed of airflow results ina decrease in pressure on the upper surface ofthe airfoil. At the same time, air flows along thelower surface of the airfoil, building up pressure.The combination of decreased pressure on theupper surface and increased pressure on thelower surface results in an upward force. [Figure2-10]

As angle of attack is increased, the production oflift is increased. More upwash is created ahead ofthe airfoil as the leading edge stagnation pointmoves under the leading edge, and more down-wash is created aft of the trailing edge. Total liftnow being produced is perpendicular to relativewind. In summary, the production of lift is basedupon the airfoil creating circulation in theairstream (Magnus Effect) and creating differentialpressure on the airfoil (Bernoulli’s Principle).

NEWTON’S THIRD LAW OF MOTIONAdditional lift is provided by the rotor blade’s lowersurface as air striking the underside is deflecteddownward. According to Newton’s Third Law ofMotion, “for every action there is an equal andopposite reaction,” the air that is deflected down-ward also produces an upward (lifting) reaction.

Since air is much like water, the explanation forthis source of lift may be compared to the planingeffect of skis on water. The lift which supports thewater skis (and the skier) is the force caused bythe impact pressure and the deflection of waterfrom the lower surfaces of the skis.

Under most flying conditions, the impact pressureand the deflection of air from the lower surface ofthe rotor blade provides a comparatively smallpercentage of the total lift. The majority of lift is theresult of decreased pressure above the blade,rather than the increased pressure below it.

WEIGHTNormally, weight is thought of as being a known,fixed value, such as the weight of the helicopter,fuel, and occupants. To lift the helicopter off theground vertically, the rotor system must generateenough lift to overcome or offset the total weightof the helicopter and its occupants. This is accom-plished by increasing the pitch angle of the mainrotor blades.

The difference in surface velocity accounts for adifference in pressure, with the pressure beinglower on the top than the bottom. This low pres-sure area produces an upward force known as the“Magnus Effect.” This mechanically induced circu-lation illustrates the relationship between circula-tion and lift.

An airfoil with a positive angle of attack developsair circulation as its sharp trailing edge forces therear stagnation point to be aft of the trailing edge,while the front stagnation point is below the lead-ing edge. [Figure 2-8]

BERNOULLI’S PRINCIPLEAir flowing over the top surface accelerates. Theairfoil is now subjected to Bernoulli’s Principle orthe “venturi effect.” As air velocity increases throughthe constricted portion of a venturi tube, the pres-sure decreases. Compare the upper surface of anairfoil with the constriction in a venturi tube that isnarrower in the middle than at the ends. [Figure 2-9]

The upper half of the venturi tube can be replacedby layers of undisturbed air. Thus, as air flowsover the upper surface of an airfoil, the camber of

Figure 2-10. Lift is produced when there is decreased pressureabove and increased pressure below an airfoil.

Figure 2-9. The upper surface of an airfoil is similar to the con-striction in a venturi tube.

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of one rotor blade as the radius of a circle andthen determining the area the blades encompassduring a complete rotation. As the helicopter ismaneuvered, disc loading changes. The higherthe loading, the more power you need to maintainrotor speed.

THRUSTThrust, like lift, is generated by the rotation of themain rotor system. In a helicopter, thrust can beforward, rearward, sideward, or vertical. Theresultant of lift and thrust determines the directionof movement of the helicopter.

The solidity ratio is the ratio of the total rotor bladearea, which is the combined area of all the mainrotor blades, to the total rotor disc area. This ratioprovides a means to measure the potential for arotor system to provide thrust.

The tail rotor also produces thrust. The amount ofthrust is variable through the use of the antitorquepedals and is used to control the helicopter’s yaw.

DRAGThe force that resists the movement of a helicop-ter through the air and is produced when lift isdeveloped is called drag. Drag always acts paral-lel to the relative wind. Total drag is composed ofthree types of drag: profile, induced, and parasite.

PROFILE DRAGProfile drag develops from the frictional resistanceof the blades passing through the air. It does notchange significantly with the airfoil’s angle ofattack, but increases moderately when airspeed

Aircraft Yaw—The movement ofthe helicopter about its verticalaxis.

The weight of the helicopter can also be influ-enced by aerodynamic loads. When you bank ahelicopter while maintaining a constant altitude,the “G” load or load factor increases. Load factoris the ratio of the load supported by the main rotorsystem to the actual weight of the helicopter andits contents. In steady-state flight, the helicopterhas a load factor of one, which means the mainrotor system is supporting the actual total weightof the helicopter. If you increase the bank angle to60°, while still maintaining a constant altitude, theload factor increases to two. In this case, the mainrotor system has to support twice the weight of thehelicopter and its contents. [Figure 2-11]

Disc loading of a helicopter is the ratio of weight tothe total main rotor disc area, and is determinedby dividing the total helicopter weight by the rotordisc area, which is the area swept by the blades ofa rotor. Disc area can be found by using the span

Figure 2-11. The load factor diagram allows you to calculate theamount of “G” loading exerted with various angle of bank.

Figure 2-12. It is easy to visualize the creation of form drag by examining the airflow around a flat plate. Streamlining decreases form dragby reducing the airflow separation.

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increases. Profile drag is composed of form dragand skin friction.

Form drag results from the turbulent wake causedby the separation of airflow from the surface of astructure. The amount of drag is related to boththe size and shape of the structure that protrudesinto the relative wind. [Figure 2-12]

Skin friction is caused by surface roughness.Even though the surface appears smooth, it maybe quite rough when viewed under a microscope.A thin layer of air clings to the rough surface andcreates small eddies that contribute to drag.

INDUCED DRAGInduced drag is generated by the airflow circula-tion around the rotor blade as it creates lift. Thehigh-pressure area beneath the blade joins the

low-pressure air above the blade at the trailingedge and at the rotor tips. This causes a spiral, orvortex, which trails behind each blade wheneverlift is being produced. These vortices deflect theairstream downward in the vicinity of the blade,creating an increase in downwash. Therefore, theblade operates in an average relative wind that isinclined downward and rearward near the blade.Because the lift produced by the blade is perpen-dicular to the relative wind, the lift is inclined aft bythe same amount. The component of lift that isacting in a rearward direction is induced drag.[Figure 2-13]

As the air pressure differential increases with anincrease in angle of attack, stronger vortices form,and induced drag increases. Since the blade’sangle of attack is usually lower at higher air-speeds, and higher at low speeds, induced drag

decreases as airspeed increases and increasesas airspeed decreases. Induced drag is the majorcause of drag at lower airspeeds.

PARASITE DRAGParasite drag is present any time the helicopter ismoving through the air. This type of drag increaseswith airspeed. Nonlifting components of the helicop-ter, such as the cabin, rotor mast, tail, and landing

Figure 2-14. The total drag curve represents the combined forcesof parasite, profile, and induced drag; and is plotted against air-speed.

L/Dmax—The maximum ratiobetween total lift (L) and the totaldrag (D). This point provides thebest glide speed. Any deviationfrom best glide speed increasesdrag and reduces the distanceyou can glide.

Figure 2-13. The formation of induced drag is associated with thedownward deflection of the airstream near the rotor blade.

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Once a helicopter leaves the ground, it is actedupon by the four aerodynamic forces. In this chap-ter, we will examine these forces as they relate toflight maneuvers.

POWERED FLIGHTIn powered flight (hovering, vertical, forward, side-ward, or rearward), the total lift and thrust forcesof a rotor are perpendicular to the tip-path planeor plane of rotation of the rotor.

HOVERING FLIGHTFor standardization purposes, this discussionassumes a stationary hover in a no-wind condi-tion. During hovering flight, a helicopter maintainsa constant position over a selected point, usuallya few feet above the ground. For a helicopter tohover, the lift and thrust produced by the rotor sys-tem act straight up and must equal the weight anddrag, which act straight down. While hovering, youcan change the amount of main rotor thrust tomaintain the desired hovering altitude. This isdone by changing the angle of attack of the mainrotor blades and by varying power, as needed. In

this case, thrust acts in the same vertical directionas lift. [Figure 3-1]

The weight that must be supported is the total weightof the helicopter and its occupants. If the amount ofthrust is greater than the actual weight, the helicoptergains altitude; if thrust is less than weight, the heli-copter loses altitude.

The drag of a hovering helicopter is mainly induceddrag incurred while the blades are producing lift.There is, however, some profile drag on the bladesas they rotate through the air. Throughout the restof this discussion, the term “drag” includes bothinduced and profile drag.

An important consequence of producing thrust istorque. As stated before, for every action there isan equal and opposite reaction. Therefore, as theengine turns the main rotor system in a counter-clockwise direction, the helicopter fuselage turnsclockwise. The amount of torque is directly relatedto the amount of engine power being used to turnthe main rotor system. Remember, as powerchanges, torque changes.

To counteract this torque-induced turning ten-dency, an antitorque rotor or tail rotor is incorpo-rated into most helicopter designs. You can varythe amount of thrust produced by the tail rotor inrelation to the amount of torque produced by theengine. As the engine supplies more power, the

Figure 3-1. To maintain a hover at a constant altitude, enough liftand thrust must be generated to equal the weight of the helicopterand the drag produced by the rotor blades.

Figure 3-2. A tail rotor is designed to produce thrust in a directionopposite torque. The thrust produced by the tail rotor is sufficientto move the helicopter laterally.

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should be smooth and not exaggerated. [Figure 3-3]

CONINGIn order for a helicopter to generate lift, the rotorblades must be turning. This creates a relativewind that is opposite the direction of rotor systemrotation. The rotation of the rotor system creates centrifugalforce (inertia), which tends to pull the bladesstraight outward from the main rotor hub. Thefaster the rotation, the greater the centrifugalforce. This force gives the rotor blades their rigid-ity and, in turn, the strength to support the weight

of the helicopter. The centrifugal force generateddetermines the maximum operating rotor r.p.m.due to structural limitations on the main rotor sys-tem.

As a vertical takeoff is made, two major forces areacting at the same time—centrifugal force actingoutward and perpendicular to the rotor mast, andlift acting upward and parallel to the mast. Theresult of these two forces is that the bladesassume a conical path instead of remaining in theplane perpendicular to the mast. [Figure 3-4]

Figure 3-4. Rotor blade coning occurs as the rotor blades begin tolift the weight of the helicopter. In a semirigid and rigid rotor sys-tem, coning results in blade bending. In an articulated rotor sys-tem, the blades assume an upward angle through movementabout the flapping hinges.

Centrifugal Force—The apparentforce that an object moving alonga circular path exerts on the bodyconstraining the obect and thatacts outwardy away from thecenter of rotation.

tail rotor must produce more thrust. This is donethrough the use of antitorque pedals.

TRANSLATING TENDENCY OR DRIFTDuring hovering flight, a single main rotor helicoptertends to drift in the same direction as antitorque rotorthrust. This drifting tendency is called translating ten-dency. [Figure 3-2]

To counteract this drift, one or more of the follow-ing features may be used:

• The main transmission is mounted so that therotor mast is rigged for the tip-path plane tohave a built-in tilt opposite tail thrust, thus pro-ducing a small sideward thrust.

• Flight control rigging is designed so that therotor disc is tilted slightly opposite tail rotorthrust when the cyclic is centered.

• The cyclic pitch control system is designed sothat the rotor disc tilts slightly opposite tailrotor thrust when in a hover.

Counteracting translating tendency, in a helicopterwith a counterclockwise main rotor system, causesthe left skid to hang lower while hovering. The oppo-site is true for rotor systems turning clockwise whenviewed from above.

PENDULAR ACTIONSince the fuselage of the helicopter, with a singlemain rotor, is suspended from a single point andhas considerable mass, it is free to oscillate eitherlongitudinally or laterally in the same way as a pen-dulum. This pendular action can be exaggerated byover controlling; therefore, control movements

Figure 3-3. Because the helicopter’s body has mass and is sus-pended from a single point (the rotor mast head), it tends to actmuch like a pendulum.

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CORIOLIS EFFECT (LAW OF CONSERVATION OF ANGULAR MOMENTUM)Coriolis Effect, which is sometimes referred to asconservation of angular momentum, might becompared to spinning skaters. When they extendtheir arms, their rotation slows down because thecenter of mass moves farther from the axis of rota-

tion. When their arms are retracted, the rotationspeeds up because the center of mass movescloser to the axis of rotation.

When a rotor blade flaps upward, the center ofmass of that blade moves closer to the axis of rota-tion and blade acceleration takes place in order toconserve angular momentum. Conversely, when

that blade flaps downward, its center of massmoves further from the axis of rotation and bladedeceleration takes place. [Figure 3-5] Keep in mind

that due to coning, a rotor blade will not flap belowa plane passing through the rotor hub and perpen-dicular to the axis of rotation. The acceleration anddeceleration actions of the rotor blades areabsorbed by either dampers or the blade structureitself, depending upon the design of the rotor sys-tem.

Two-bladed rotor systems are normally subject toCoriolis Effect to a much lesser degree than arearticulated rotor systems since the blades aregenerally “underslung” with respect to the rotorhub, and the change in the distance of the centerof mass from the axis of rotation is small. [Figure3-6] The hunting action is absorbed by the blades

Figure 3-5. The tendency of a rotor blade to increase or decreaseits velocity in its plane of rotation due to mass movement is knownas Coriolis Effect, named for the mathematician who made stud-ies of forces generated by radial movements of mass on a rotatingdisc.

Figure 3-7. Air circulation patterns change when hovering out of ground effect (OGE) and when hovering in ground effect (IGE).

Figure 3-6. Because of the underslung rotor, the center of massremains approximately the same distance from the mast after therotor is tilted.

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through bending. If a two-bladed rotor system isnot “underslung,” it will be subject to CoriolisEffect comparable to that of a fully articulated sys-tem.

GROUND EFFECTWhen hovering near the ground, a phenomenonknown as ground effect takes place. [Figure 3-7]This effect usually occurs less than one rotordiameter above the surface. As the induced air-flow through the rotor disc is reduced by the sur-face friction, the lift vector increases. This allows alower rotor blade angle for the same amount of lift,which reduces induced drag. Ground effect alsorestricts the generation of blade tip vortices due tothe downward and outward airflow making a largerportion of the blade produce lift. When the helicop-ter gains altitude vertically, with no forward air-speed, induced airflow is no longer restricted, andthe blade tip vortices increase with the decrease inoutward airflow. As a result, drag increases whichmeans a higher pitch angle, and more power isneeded to move the air down through the rotor.

Ground effect is at its maximum in a no-wind con-dition over a firm, smooth surface. Tall grass,rough terrain, revetments, and water surfacesalter the airflow pattern, causing an increase inrotor tip vortices.

GYROSCOPIC PRECESSIONThe spinning main rotor of a helicopter acts like agyroscope. As such, it has the properties of gyro-scopic action, one of which is precession.Gyroscopic precession is the resultant action ordeflection of a spinning object when a force is

applied to this object. This action occurs approxi-mately 90° in the direction of rotation from thepoint where the force is applied. [Figure 3-8]

Let us look at a two-bladed rotor system to seehow gyroscopic precession affects the movementof the tip-path plane. Moving the cyclic pitch con-trol increases the angle of attack of one rotorblade with the result that a greater lifting force isapplied at that point in the plane of rotation. Thissame control movement simultaneouslydecreases the angle of attack of the other bladethe same amount, thus decreasing the lifting force

Figure 3-8. Gyroscopic precession principle—when a force is applied to a spinning gyro, the maximum reaction occurs approximately 90°later in the direction of rotation.

Figure 3-9. With a counterclockwise main rotor blade rotation, aseach blade passes the 90° position on the left, the maximumincrease in angle of attack occurs. As each blade passes the 90°position to the right, the maximum decrease in angle of attackoccurs. Maximum deflection takes place 90° later—maximumupward deflection at the rear and maximum downward deflectionat the front—and the tip-path plane tips forward.

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flap up; the blade with the decreased angle ofattack tends to flap down. Because the rotor disk

acts like a gyro, the blades reach maximumdeflection at a point approximately 90° later in theplane of rotation. As shown in figure 3-9, theretreating blade angle of attack is increased andthe advancing blade angle of attack is decreasedresulting in a tipping forward of the tip-path plane,since maximum deflection takes place 90° laterwhen the blades are at the rear and front, respec-tively. In a rotor system using three or more

blades, the movement of the cyclic pitch controlchanges the angle of attack of each blade anappropriate amount so that the end result is thesame.

VERTICAL FLIGHTHovering is actually an element of vertical flight.Increasing the angle of attack of the rotor blades(pitch) while their velocity remains constant gen-erates additional vertical lift and thrust and the hel-icopter ascends. Decreasing the pitch causes thehelicopter to descend. In a no wind conditionwhen lift and thrust are less than weight and drag,the helicopter descends vertically. If lift and thrustare greater than weight and drag, the helicopterascends vertically. [Figure 3-10]

FORWARD FLIGHTIn or during forward flight, the tip-path plane is tiltedforward, thus tilting the total lift-thrust force forwardfrom the vertical. This resultant lift-thrust force canbe resolved into two components—lift acting verti-cally upward and thrust acting horizontally in thedirection of flight. In addition to lift and thrust, thereis weight (the downward acting force) and drag (therearward acting or retarding force of inertia and windresistance). [Figure 3-11]

In straight-and-level, unaccelerated forward flight,lift equals weight and thrust equals drag (straight-and-level flight is flight with a constant headingand at a constant altitude). If lift exceeds weight,the helicopter climbs; if lift is less than weight, thehelicopter descends. If thrust exceeds drag, thehelicopter speeds up; if thrust is less than drag, itslows down.

As the helicopter moves forward, it begins to losealtitude because of the lift that is lost as thrust is

Figure 3-11. To transition into forward flight, some of the verticalthrust must be vectored horizontally. You initiate this by forwardmovement of the cyclic control.

Figure 3-12. Effective translational lift is easily recognized inactual flight by a transient induced aerodynamic vibration andincreased performance of the helicopter.

Figure 3-10. To ascend vertically, more lift and thrust must be gen-

erated to overcome the forces of weight and the drag.

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diverted forward. However, as the helicopterbegins to accelerate, the rotor system becomesmore efficient due to the increased airflow. Theresult is excess power over that which is requiredto hover. Continued acceleration causes an evenlarger increase in airflow through the rotor discand more excess power.

TRANSLATIONAL LIFTTranslational lift is present with any horizontal flowof air across the rotor. This increased flow is mostnoticeable when the airspeed reaches approxi-mately 16 to 24 knots. As the helicopter acceler-ates through this speed, the rotor moves out of itsvortices and is in relatively undisturbed air. Theairflow is also now more horizontal, which reducesinduced flow and drag with a correspondingincrease in angle of attack and lift. The additional liftavailable at this speed is referred to as “effectivetranslational lift” (ETL). [Figure 3-12]

When a single-rotor helicopter flies through transla-tional lift, the air flowing through the main rotor andover the tail rotor becomes less turbulent and moreaerodynamically efficient. As the tail rotor efficiencyimproves, more thrust is produced causing the air-craft to yaw left in a counterclockwise rotor system.It will be necessary to use right torque pedal to cor-rect for this tendency on takeoff. Also, if no correc-tions are made, the nose rises or pitches up, androlls to the right. This is caused by combined effectsof dissymmetry of lift and transverse flow effect, andis corrected with cyclic control.

Translational lift is also present in a stationary hoverif the wind speed is approximately 16 to 24 knots. Innormal operations, always utilize the benefit oftranslational lift, especially if maximum perform-ance is needed.

INDUCED FLOWAs the rotor blades rotate they generate what iscalled rotational relative wind. This airflow is char-acterized as flowing parallel and opposite therotor’s plane of rotation and striking perpendicularto the rotor blade’s leading edge. This rotationalrelative wind is used to generate lift. As rotorblades produce lift, air is accelerated over the foiland projected downward. Anytime a helicopter isproducing lift, it moves large masses of air verti-cally and down through the rotor system. Thisdownwash or induced flow can significantlychange the efficiency of the rotor system.Rotational relative wind combines with inducedflow to form the resultant relative wind. As inducedflow increases, resultant relative wind becomesless horizontal. Since angle of attack is deter-mined by measuring the difference between thechord line and the resultant relative wind, as theresultant relative wind becomes less horizontal,angle of attack decreases. [Figure 3-13]

TRANSVERSE FLOW EFFECTAs the helicopter accelerates in forward flight,induced flow drops to near zero at the forward discarea and increases at the aft disc area. Thisincreases the angle of attack at the front disc areacausing the rotor blade to flap up, and reducesangle of attack at the aft disc area causing therotor blade to flap down. Because the rotor acts

Figure 3-13. A helicopter in forward flight, or hovering with a headwind or crosswind, has more molecules of air entering the aft portion ofthe rotor blade. Therefore, the angle of attack is less and the induced flow is greater at the rear of the rotor disc.

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like a gyro, maximum displacement occurs 90° inthe direction of rotation. The result is a tendencyfor the helicopter to roll slightly to the right as itaccelerates through approximately 20 knots or ifthe headwind is approximately 20 knots.

You can recognize transverse flow effect becauseof increased vibrations of the helicopter at air-speeds just below effective translational lift ontakeoff and after passing through effective transla-tional lift during landing. To counteract transverseflow effect, a cyclic input needs to be made.

DISSYMMETRY OF LIFTWhen the helicopter moves through the air, therelative airflow through the main rotor disc is dif-ferent on the advancing side than on the retreat-ing side. The relative wind encountered by theadvancing blade is increased by the forwardspeed of the helicopter, while the relative windspeed acting on the retreating blade is reduced bythe helicopter’s forward airspeed. Therefore, as aresult of the relative wind speed, the advancingblade side of the rotor disc produces more lift thanthe retreating blade side. This situation is definedas dissymmetry of lift. [Figure 3-14]

Figure 3-14. The blade tip speed of this helicopter is approxi-mately 300 knots. If the helicopter is moving forward at 100 knots,the relative wind speed on the advancing side is 400 knots. Onthe retreating side, it is only 200 knots. This difference in speedcauses a dissymmetry of lift.

Figure 3-15. The combined upward flapping (reduced lift) of the advancing blade and downward flapping (increased lift) of the retreatingblade equalizes lift across the main rotor disc counteracting dissymmetry of lift.

VNE —The speed beyond which an aircraft should never beoperated. VNE can change with altitude, density altitude, andweight.

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angle between the chord line and the resultant rel-ative wind increases. This increases the angle of

attack and thus the amount of lift produced by theblade.

The combination of blade flapping and slow relativewind acting on the retreating blade normally limitsthe maximum forward speed of a helicopter. At a highforward speed, the retreating blade stalls because ofa high angle of attack and slow relative wind speed.This situation is called retreating blade stall and isevidenced by a nose pitch up, vibration, and a rollingtendency—usually to the left in helicopters withcounterclockwise blade rotation.

You can avoid retreating blade stall by not exceed-ing the never-exceed speed. This speed is desig-nated VNE and is usually indicated on a placardand marked on the airspeed indicator by a red line.

During aerodynamic flapping of the rotor blades asthey compensate for dissymmetry of lift, the advanc-ing blade achieves maximum upflapping displace-ment over the nose and maximum downflappingdisplacement over the tail. This causes the tip-pathplane to tilt to the rear and is referred to as blow-back. Figure 3-16 shows how the rotor disc wasoriginally oriented with the front down following theinitial cyclic input, but as airspeed is gained and flap-

Centripetal Force—The forceopposite centrifugal force andattracts a body toward its axis ofrotation.

Figure 3-18. Forces acting on the helicopter during rearward flight.

If this condition was allowed to exist, a helicopterwith a counterclockwise main rotor blade rotationwould roll to the left because of the difference inlift. In reality, the main rotor blades flap and featherautomatically to equalize lift across the rotor disc.Articulated rotor systems, usually with three ormore blades, incorporate a horizontal hinge (flap-ping hinge) to allow the individual rotor blades tomove, or flap up and down as they rotate. A semi-rigid rotor system (two blades) utilizes a teetering

hinge, which allows the blades to flap as a unit.When one blade flaps up, the other flaps down.

As shown in figure 3-15, as the rotor bladereaches the advancing side of the rotor disc (A), itreaches its maximum upflap velocity. When theblade flaps upward, the angle between the chordline and the resultant relative wind decreases.

This decreases the angle of attack, which reducesthe amount of lift produced by the blade. At posi-tion (C) the rotor blade is now at its maximumdownflapping velocity. Due to downflapping, the

Figure 3-17. Forces acting on the helicopter during sidewardflight.

Figure 3-16. To compensate for blowback, you must move thecyclic forward. Blowback is more pronounced with higher air-speeds.

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ping eliminates dissymmetry of lift, the front of thedisc comes up, and the back of the disc goes down.This reorientation of the rotor disc changes thedirection in which total rotor thrust acts so that thehelicopter’s forward speed slows, but can be cor-rected with cyclic input.

SIDEWARD FLIGHTIn sideward flight, the tip-path plane is tilted in thedirection that flight is desired. This tilts the total lift-thrust vector sideward. In this case, the vertical orlift component is still straight up and weight straightdown, but the horizontal or thrust component nowacts sideward with drag acting to the opposite side.[Figure 3-17]

REARWARD FLIGHTFor rearward flight, the tip-path plane is tilted rear-ward, which, in turn, tilts the lift-thrust vector rear-ward. Drag now acts forward with the liftcomponent straight up and weight straight down.[Figure 3-18]

Figure 3-20. During an autorotation, the upward flow of relative wind permits the main rotor blades to rotate at their normal speed. Ineffect, the blades are “gliding” in their rotational plane.

Figure 3-21. Blade regions in vertical autorotation descent.

Figure 3-19. The horizontal component of lift accelerates the heli-copter toward the center of the turn.

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TURNING FLIGHTIn forward flight, the rotor disc is tilted forward,which also tilts the total lift-thrust force of the rotordisc forward. When the helicopter is banked, therotor disc is tilted sideward resulting in lift beingseparated into two components. Lift acting upwardand opposing weight is called the vertical compo-

nent of lift. Lift acting horizontally and opposinginertia (centrifugal force) is the horizontal compo-nent of lift (centripetal force). [Figure 3-19]

As the angle of bank increases, the total lift force istilted more toward the horizontal, thus causing therate of turn to increase because more lift is acting

Figure 3-22. Force vectors in vertical autorotation descent.

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horizontally. Since the resultant lifting force actsmore horizontally, the effect of lift acting verticallyis deceased. To compensate for this decreasedvertical lift, the angle of attack of the rotor bladesmust be increased in order to maintain altitude.The steeper the angle of bank, the greater theangle of attack of the rotor blades required to main-tain altitude. Thus, with an increase in bank and agreater angle of attack, the resultant lifting forceincreases and the rate of turn is faster.

AUTOROTATIONAutorotation is the state of flight where the mainrotor system is being turned by the action of rela-tive wind rather than engine power. It is the meansby which a helicopter can be landed safely in theevent of an engine failure. In this case, you areusing altitude as potential energy and converting itto kinetic energy during the descent and touch-down. All helicopters must have this capability inorder to be certified. Autorotation is permittedmechanically because of a freewheeling unit,which allows the main rotor to continue turningeven if the engine is not running. In normal pow-ered flight, air is drawn into the main rotor systemfrom above and exhausted downward. Duringautorotation, airflow enters the rotor disc frombelow as the helicopter descends. [Figure 3-20]

AUTOROTATION (VERTICAL FLIGHT)Most autorotations are performed with forwardspeed. For simplicity, the following aerodynamicexplanation is based on a vertical autorotativedescent (no forward speed) in still air. Under theseconditions, the forces that cause the blades to turnare similar for all blades regardless of their posi-tion in the plane of rotation. Therefore, dissymme-try of lift resulting from helicopter airspeed is not afactor.

During vertical autorotation, the rotor disc isdivided into three regions as illustrated in figure 3-21—the driven region, the driving region, and thestall region. Figure 3-22 shows four blade sections

that illustrate force vectors. Part A is the drivenregion, B and D are points of equilibrium, part C isthe driving region, and part E is the stall region.Force vectors are different in each region becauserotational relative wind is slower near the bladeroot and increases continually toward the bladetip. Also, blade twist gives a more positive angle ofattack in the driving region than in the drivenregion. The combination of the inflow up throughthe rotor with rotational relative wind produces dif-ferent combinations of aerodynamic force at everypoint along the blade.

The driven region, also called the propeller region,is nearest the blade tips. Normally, it consists ofabout 30 percent of the radius. In the drivenregion, part A of figure 3-22, the total aerodynamicforce acts behind the axis of rotation, resulting in aoverall drag force. The driven region producessome lift, but that lift is offset by drag. The overallresult is a deceleration in the rotation of the blade.The size of this region varies with the blade pitch,rate of descent, and rotor r.p.m. When changing

autorotative r.p.m., blade pitch, or rate of descent,the size of the driven region in relation to the otherregions also changes.

There are two points of equilibrium on the blade—one between the driven region and the drivingregion, and one between the driving region andthe stall region. At points of equilibrium, total aero-dynamic force is aligned with the axis of rotation.Lift and drag are produced, but the total effect pro-duces neither acceleration nor deceleration.

Figure 3-23. Blade regions in forward autorotation descent.

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The driving region, or autorotative region, nor-mally lies between 25 to 70 percent of the bladeradius. Part C of figure 3-22 shows the drivingregion of the blade, which produces the forcesneeded to turn the blades during autorotation.Total aerodynamic force in the driving region isinclined slightly forward of the axis of rotation, pro-ducing a continual acceleration force. This inclina-tion supplies thrust, which tends to accelerate therotation of the blade. Driving region size varieswith blade pitch setting, rate of descent, and rotorr.p.m.

By controlling the size of this region you canadjust autorotative r.p.m. For example, if the col-lective pitch is raised, the pitch angle increases inall regions. This causes the point of equilibrium tomove inboard along the blade’s span, thusincreasing the size of the driven region. The stallregion also becomes larger while the drivingregion becomes smaller. Reducing the size of thedriving region causes the acceleration force of thedriving region and r.p.m. to decrease.

The inner 25 percent of the rotor blade is referredto as the stall region and operates above its maxi-mum angle of attack (stall angle) causing dragwhich tends to slow rotation of the blade. Part E offigure 3-22 depicts the stall region.

A constant rotor r.p.m. is achieved by adjusting thecollective pitch so blade acceleration forces fromthe driving region are balanced with the decelera-tion forces from the driven and stall regions.

AUTOROTATION (FORWARD FLIGHT)Autorotative force in forward flight is produced inexactly the same manner as when the helicopteris descending vertically in still air. However,because forward speed changes the inflow of airup through the rotor disc, all three regions moveoutboard along the blade span on the retreatingside of the disc where angle of attack is larger, asshown in figure 3-23. With lower angles of attackon the advancing side blade, more of that bladefalls in the driven region. On the retreating side,

more of the blade is in the stall region. A small sec-tion near the root experiences a reversed flow,therefore the size of the driven region on theretreating side is reduced.

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Note: In this chapter, it is assumed that the helicop-ter has a counterclockwise main rotor blade rotationas viewed from above. If flying a helicopter with aclockwise rotation, you will need to reverse left andright references, particularly in the areas of rotorblade pitch change, antitorque pedal movement,and tail rotor thrust.

There are four basic controls used during flight.They are the collective pitch control, the throttle,the cyclic pitch control, and the antitorque pedals.

COLLECTIVE PITCH CONTROLThe collective pitch control, located on the left sideof the pilot’s seat, changes the pitch angle of allmain rotor blades simultaneously, or collectively,as the name implies. As the collective pitch con-trol is raised, there is a simultaneous and equalincrease in pitch angle of all main rotor blades; asit is lowered, there is a simultaneous and equaldecrease in pitch angle. This is done through aseries of mechanical linkages and the amount ofmovement in the collective lever determines the

amount of blade pitch change. [Figure 4-1] Anadjustable friction control helps prevent inadver-tent collective pitch movement.

Changing the pitch angle on the bladeschanges the angle of attack on each blade. Witha change in angle of attack comes a change indrag, which affects the speed or r.p.m. of themain rotor. As the pitch angle increases, angleof attack increases, drag increases, and rotorr.p.m. decreases. Decreasing pitch angledecreases both angle of attack and drag, whilerotor r.p.m. increases. In order to maintain aconstant rotor r.p.m., which is essential in heli -copter operations, a proportionate change inpower is required to compensate for the changein drag. This is accomplished with the throttlecontrol or a correlator and/or governor, whichautomatically adjusts engine power.

Figure 4-1. Raising the collective pitch control increases the pitch angle the same amount on all blades.

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THROTTLE CONTROLThe function of the throttle is to regulate enginer.p.m. If the correlator or governor system doesnot maintain the desired r.p.m. when the collectiveis raised or lowered, or if those systems are notinstalled, the throttle has to be moved manuallywith the twist grip in order to maintain r.p.m.Twisting the throttle outboard increases r.p.m.;twisting it inboard decreases r.p.m. [Figure 4-2]

COLLECTIVE PITCH / THROTTLECOORDINATIONWhen the collective pitch is raised, the load onthe engine is increased in order to maintaindesired r.p.m. The load is measured by a mani-fold pressure gauge in piston helicopters or by atorque gauge in turbine helicopters.

In piston helicopters, the collective pitch is the pri-mary control for manifold pressure, and the throt-tle is the primary control for r.p.m. However, thecollective pitch control also influences r.p.m., andthe throttle also influences manifold pressure;

therefore, each is considered to be a secondarycontrol of the other’s function. Both the tachome-ter (r.p.m. indicator) and the manifold pressuregauge must be analyzed to determine which con-trol to use. Figure 4-3 illustrates this relationship.

CORRELATOR / GOVERNORA correlator is a mechanical connection betweenthe collective lever and the engine throttle. Whenthe collective lever is raised, power is automati-cally increased and when lowered, power isdecreased. This system maintains r.p.m. close tothe desired value, but still requires adjustment ofthe throttle for fine tuning.

A governor is a sensing device that senses rotor andengine r.p.m. and makes the necessary adjust-ments in order to keep rotor r.p.m. constant. In nor-mal operations, once the rotor r.p.m. is set, thegovernor keeps the r.p.m. constant, and there is noneed to make any throttle adjustments. Governorsare common on all turbine helicopters and used onsome piston powered helicopters.

Some helicopters do not have correlators or gov-ernors and require coordination of all collectiveand throttle movements. When the collective israised, the throttle must be increased; when thecollective is lowered, the throttle must bedecreased. As with any aircraft control, largeadjustments of either collective pitch or throttle

Figure 4-2. A twist grip throttle is usually mounted on the end ofthe collective lever. Some turbine helicopters have the throttlesmounted on the overhead panel or on the floor in the cockpit.

Figure 4-3. Relationship between manifold pressure, r.p.m., col-lective, and throttle.

Figure 4-4. The cyclic pitch control may be mounted verticallybetween the pilot’s knees or on a teetering bar from a single cycliclocated in the center of the helicopter. The cyclic can pivot in alldirections.

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should be avoided. All corrections should be madethrough the use of smooth pressure.

CYCLIC PITCH CONTROLThe cyclic pitch control tilts the main rotor disc bychanging the pitch angle of the rotor blades intheir cycle of rotation. When the main rotor disc istilted, the horizontal component of lift moves thehelicopter in the direction of tilt. [Figure 4-4]

The rotor disc tilts in the direction that pressure isapplied to the cyclic pitch control. If the cyclic ismoved forward, the rotor disc tilts forward; if thecyclic is moved aft, the disc tilts aft, and so on.Because the rotor disc acts like a gyro, the mechan-ical linkages for the cyclic control rods are rigged insuch a way that they decrease the pitch angle of therotor blade approximately 90° before it reaches thedirection of cyclic displacement, and increase thepitch angle of the rotor blade approximately 90° afterit passes the direction of displacement. An increasein pitch angle increases angle of attack; a decreasein pitch angle decreases angle of attack. For exam-ple, if the cyclic is moved forward, the angle of attackdecreases as the rotor blade passes the right sideof the helicopter and increases on the left side. Thisresults in maximum downward deflection of the rotorblade in front of the helicopter and maximum

upward deflection behind it, causing the rotor disc totilt forward.

ANTITORQUE PEDALSThe antitorque pedals, located on the cabin floorby the pilot’s feet, control the pitch, and thereforethe thrust, of the tail rotor blades. [Figure 4-5] .The main purpose of the tail rotor is to counteractthe torque effect of the main rotor. Since torquevaries with changes in power, the tail rotor thrustmust also be varied. The pedals are connected tothe pitch change mechanism on the tail rotor gear-box and allow the pitch angle on the tail rotorblades to be increased or decreased.

HEADING CONTROLBesides counteracting torque of the main rotor, thetail rotor is also used to control the heading of thehelicopter while hovering or when making hoveringturns. Hovering turns are commonly referred to as“pedal turns.”

In forward flight, the antitorque pedals are not usedto control the heading of the helicopter, except dur-ing portions of crosswind takeoffs and approaches.Instead they are used to compensate for torque toput the helicopter in longitudinal trim so that coordi-nated flight can be maintained. The cyclic control isused to change heading by making a turn to thedesired direction.

The thrust of the tail rotor depends on the pitch angleof the tail rotor blades. This pitch angle can be posi-tive, negative, or zero. A positive pitch angle tends tomove the tail to the right. A negative pitch anglemoves the tail to the left, while no thrust is producedwith a zero pitch angle.

With the right pedal moved forward of the neutralposition, the tail rotor either has a negative pitchangle or a small positive pitch angle. The farther itis forward, the larger the negative pitch angle. Thenearer it is to neutral, the more positive the pitchangle, and somewhere in between, it has a zeropitch angle. As the left pedal is moved forward of

Figure 4-5. Antitorque pedals compensate for changes in torqueand control heading in a hover.

Figure 4-6. Tail rotor pitch angle and thrust in relation to pedal positions during cruising flight.

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the neutral position, the positive pitch angle of thetail rotor increases until it becomes maximum withfull forward displacement of the left pedal.

If the tail rotor has a negative pitch angle, tail rotorthrust is working in the same direction as thetorque of the main rotor. With a small positive pitchangle, the tail rotor does not produce sufficientthrust to overcome the torque effect of the mainrotor during cruise flight. Therefore, if the rightpedal is displaced forward of neutral during cruis-ing flight, the tail rotor thrust does not overcome

the torque effect, and the nose yaws to the right.[Figure 4-6]

With the antitorque pedals in the neutral position,the tail rotor has a medium positive pitch angle. Inmedium positive pitch, the tail rotor thrust approxi-mately equals the torque of the main rotor duringcruise flight, so the helicopter maintains a constantheading in level flight.

If the left pedal is in a forward position, the tailrotor has a high positive pitch position. In this posi-tion, tail rotor thrust exceeds the thrust needed to

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By knowing the various systems on a helicopter,you will be able to more easily recognize potentialproblems, and if a problem arises, you will have abetter understanding of what to do to correct thesituation.

ENGINESThe two most common types of engines used inhelicopters are the reciprocating engine and theturbine engine. Reciprocating engines, also calledpiston engines, are generally used in smaller heli-copters. Most training helicopters use reciprocat-ing engines because they are relatively simpleand inexpensive to operate. Turbine engines aremore powerful and are used in a wide variety ofhelicopters. They produce a tremendous amountof power for their size but are generally moreexpensive to operate.

RECIPROCATING ENGINEThe reciprocating engine consists of a series ofpistons connected to a rotating crankshaft. As thepistons move up and down, the crankshaft rotates.The reciprocating engine gets its name from theback-and-forth movement of its internal parts. Thefour-stroke engine is the most common type, andrefers to the four different cycles the engine under-goes to produce power. [Figure 5-1]

When the piston moves away from the cylinderhead on the intake stroke, the intake valve opensand a mixture of fuel and air is drawn into the com-bustion chamber. As the cylinder moves backtowards the cylinder head, the intake valve closes,and the fuel/air mixture is compressed. Whencompression is nearly complete, the spark plugsfire and the compressed mixture is ignited to beginthe power stroke. The rapidly expanding gasesfrom the controlled burning of the fuel/air mixturedrive the piston away from the cylinder head, thusproviding power to rotate the crankshaft. The pis-ton then moves back toward the cylinder head onthe exhaust stroke where the burned gasses areexpelled through the opened exhaust valve.

Even when the engine is operated at a fairly lowspeed, the four-stroke cycle takes place several

hundred times each minute. In a four-cylinderengine, each cylinder operates on a differentstroke. Continuous rotation of a crankshaft ismaintained by the precise timing of the powerstrokes in each cylinder.

TURBINE ENGINEThe gas turbine engine mounted on most helicop-ters is made up of a compressor, combustionchamber, turbine, and gearbox assembly. Thecompressor compresses the air, which is then fed

Figure 5-1. The arrows in this illustration indicate the direction ofmotion of the crankshaft and piston during the four-stroke cycle.

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into the combustion chamber where atomizedfuel is injected into it. The fuel/air mixture isignited and allowed to expand. This combustiongas is then forced through a series of turbinewheels causing them to turn. These turbinewheels provide power to both the engine com-pressor and the main rotor system through anoutput shaft. The combustion gas is finallyexpelled through an exhaust outlet. [Figure 5-2]

COMPRESSORThe compressor may consist of an axial com-pressor, a centrifugal compressor, or both. Anaxial compressor consists of two main elements,the rotor and the stator. The rotor consists of anumber of blades fixed on a rotating spindle andresembles a fan. As the rotor turns, air is drawnrearwards. Stator vanes are arranged in fixedrows between the rotor blades and act as a dif-fuser at each stage to decrease air velocity andincrease air pressure. There may be a number ofrows of rotor blades and stator vanes. Each rowconstitutes a pressure stage, and the number ofstages depends on the amount of air and pres-sure rise required for the particular engine.

A centrifugal compressor consists of an impeller,diffuser, and a manifold. The impeller, which is a

forged disc with integral blades, rotates at a highspeed to draw air in and expel it at an acceleratedrate. The air then passes through the diffuserwhich slows the air down. When the velocity ofthe air is slowed, static pressure increases,resulting in compressed, high-pressure air. Thehigh pressure air then passes through the com-pressor manifold where it is distributed to thecombustion chamber.

COMBUSTION CHAMBERUnlike a piston engine, the combustion in a tur-bine engine is continuous. An igniter plug servesonly to ignite the fuel/air mixture when starting theengine. Once the fuel/air mixture is ignited, it willcontinue to burn as long as the fuel/air mixturecontinues to be present. If there is an interruptionof fuel, air, or both, combustion ceases. This isknown as a “flame-out,” and the engine has to berestarted or re-lit. Some helicopters are equippedwith auto-relight, which automatically activates theigniters to start combustion if the engine flamesout.

TURBINEThe turbine section consists of a series of turbinewheels that are used to drive the compressor

Figure 5-2. Many helicopters use a turboshaft engine to drive the main transmission and rotor systems. The main difference between aturboshaft and a turbojet engine is that most of the energy produced by the expanding gases is used to drive a turbine rather than pro-ducing thrust through the expulsion of exhaust gases.

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section and the rotor system. The first stage,which is usually referred to as the gas produceror N1 may consist of one or more turbine wheels.This stage drives the components necessary tocomplete the turbine cycle making the engineself-sustaining. Common components driven bythe N1 stage are the compressor, oil pump, andfuel pump. The second stage, which may alsoconsist of one or more wheels, is dedicated todriving the main rotor system and accessoriesfrom the engine gearbox. This is referred to asthe power turbine (N2 or Nr).

If the first and second stage turbines are mechani-cally coupled to each other, the system is said to bea direct-drive engine or fixed turbine. These enginesshare a common shaft, which means the first andsecond stage turbines, and thus the compressor andoutput shaft, are connected.

On most turbine assemblies used in helicopters,the first stage and second stage turbines are notmechanically connected to each other. Rather,they are mounted on independent shafts and canturn freely with respect to each other. This isreferred to as a “free turbine.” When the engine isrunning, the combustion gases pass through thefirst stage turbine to drive the compressor rotor,and then past the independent second stage tur-bine, which turns the gearbox to drive the outputshaft.

TRANSMISSION SYSTEMThe transmission system transfers power from theengine to the main rotor, tail rotor, and other acces-sories. The main components of the transmissionsystem are the main rotor transmission, tail rotordrive system, clutch, and freewheeling unit.Helicopter transmissions are normally lubricatedand cooled with their own oil supply. A sight gaugeis provided to check the oil level. Some transmis-sions have chip detectors located in the sump.These detectors are wired to warning lightslocated on the pilot’s instrument panel that illumi-nate in the event of an internal problem.

Chip Detector—A chip detector isa warning device that alerts youto any abnormal wear in a trans-mission or engine. It consists of amagnetic plug located within thetransmission. The magnetattracts any ferrous metal parti-cles that have come loose fromthe bearings or other transmis -sion parts. Most chip detectorssend a signal to lights located onthe instrument panel that illumi-

nate when ferrous metal particlesare picked up.

MAIN ROTOR TRANSMISSIONThe primary purpose of the main rotor transmis-sion is to reduce engine output r.p.m. to opti-mum rotor r.p.m. This reduction is different forthe various helicopters, but as an example, sup-pose the engine r.p.m. of a specific helicopter is2,700. To achieve a rotor speed of 450 r.p.m. wouldrequire a 6 to 1 reduction. A 9 to 1 reduct ionwould mean the rotor would turn at 300r.p.m.

Most helicopters use a dual-needle tachometer toshow both engine and rotor r.p.m. or a percentageof engine and rotor r.p.m. The rotor r.p.m. needlenormally is used only during clutch engagement tomonitor rotor acceleration, and in autorotation to

Figure 5-3. There are various types of dual-needle tachometers,however, when the needles are superimposed or married, the ratioof the engine r.p.m. is the same as the gear reduction ratio.

Figure 5-4. The typical components of a tail rotor drive systemare shown here.

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maintain r.p.m. within prescribed limits. [Figure 5-3]

In helicopters with horizontally mounted engines,another purpose of the main rotor transmission isto change the axis of rotation from the horizontalaxis of the engine to the vertical axis of the rotorshaft.

TAIL ROTOR DRIVE SYSTEMThe tail rotor drive system consists of a tail rotordrive shaft powered from the main transmissionand a tail rotor transmission mounted at the end ofthe tail boom. The drive shaft may consist of onelong shaft or a series of shorter shafts connectedat both ends with flexible couplings. This allowsthe drive shaft to flex with the tail boom. The tailrotor transmission provides a right angle drive forthe tail rotor and may also include gearing toadjust the output to optimum tail rotor r.p.m.[Figure 5-4]

CLUTCHIn a conventional airplane, the engine and pro-peller are permanently connected. However, in ahelicopter there is a different relationship betweenthe engine and the rotor. Because of the greaterweight of a rotor in relation to the power of theengine, as compared to the weight of a propellerand the power in an airplane, the rotor must bedisconnected from the engine when you engagethe starter. A clutch allows the engine to be startedand then gradually pick up the load of the rotor.

On free turbine engines, no clutch is required, asthe gas producer turbine is essentially discon-nected from the power turbine. When the engineis started, there is little resistance from the powerturbine. This enables the gas producer turbine toaccelerate to normal idle speed without the loadof the transmission and rotor system dragging itdown. As the gas pressure increases through thepower turbine, the rotor blades begin to turn,slowly at first and then gradually accelerate to nor-mal operating r.p.m.

On reciprocating helicopters, the two main types ofclutches are the centrifugal clutch and the belt driveclutch.

CENTRIFUGAL CLUTCHThe centrifugal clutch is made up of an innerassembly and a outer drum. The inner assembly,which is connected to the engine driveshaft, con-sists of shoes lined with material similar to auto-motive brake linings. At low engine speeds,springs hold the shoes in, so there is no contactwith the outer drum, which is attached to the trans-

mission input shaft. As engine speed increases,centrifugal force causes the clutch shoes to moveoutward and begin sliding against the outer drum.The transmission input shaft begins to rotate, caus-ing the rotor to turn, slowly at first, but increasing asthe friction increases between the clutch shoes andtransmission drum. As rotor speed increases, therotor tachometer needle shows an increase bymoving toward the engine tachometer needle.When the two needles are superimposed, theengine and the rotor are synchronized, indicat-ing the clutch is fully engaged and there is nofurther slippage of the clutch shoes.

BELT DRIVE CLUTCHSome helicopters utilize a belt drive to transmitpower from the engine to the transmission. A beltdrive consists of a lower pulley attached to theengine, an upper pulley attached to the transmis-sion input shaft, a belt or a series of V-belts, andsome means of applying tension to the belts. Thebelts fit loosely over the upper and lower pulleywhen there is no tension on the belts. This allowsthe engine to be started without any load fromthe transmission. Once the engine is running,tension on the belts is gradually increased. Whenthe rotor and engine tachometer needles aresuperimposed, the rotor and the engine are syn-chronized, and the clutch is then fully engaged.Advantages of this system include vibration iso-lation, simple maintenance, and the ability tostart and warm up the engine without engagingthe rotor.

FREEWHEELING UNITSince lift in a helicopter is provided by rotating air-foils, these airfoils must be free to rotate if the enginefails. The freewheeling unit automatically disen-gages the engine from the main rotor when enginer.p.m. is less than main rotor r.p.m. This allows the

Figure 5-5. Each blade of a fully articulated rotor system can flap,drag, and feather independently of the other blades.

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main rotor to continue turning at normal in-flightspeeds. The most common freewheeling unitassembly consists of a one-way sprag clutchlocated between the engine and main rotor trans-mission. This is usually in the upper pulley in a pis-ton helicopter or mounted on the engine gearbox ina turbine helicopter. When the engine is driving therotor, inclined surfaces in the spray clutch forcerollers against an outer drum. This prevents theengine from exceeding transmission r.p.m. If theengine fails, the rollers move inward, allowing theouter drum to exceed the speed of the inner portion.The transmission can then exceed the speed of theengine. In this condition, engine speed is less thanthat of the drive system, and the helicopter is in anautorotative state.

MAIN ROTOR SYSTEMMain rotor systems are classified according tohow the main rotor blades move relative to themain rotor hub. As was described in Chapter 1—Introduction to the Helicopter, there are threebasic classifications: fully articulated, semirigid, orrigid. Some modern rotor systems use a combina-tion of these types.

FULLY ARTICULATED ROTOR SYSTEMIn a fully articulated rotor system, each rotor bladeis attached to the rotor hub through a series ofhinges, which allow the blade to move independ-

ently of the others. These rotor systems usuallyhave three or more blades. [Figure 5-5]

The horizontal hinge, called the flapping hinge,allows the blade to move up and down. Thismovement is called flapping and is designed tocompensate for dissymetry of lift. The flappinghinge may be located at varying distances fromthe rotor hub, and there may be more than onehinge.

The vertical hinge, called the lead-lag or draghinge, allows the blade to move back and forth.This movement is called lead-lag, dragging, orhunting. Dampers are usually used to preventexcess back and forth movement around thedrag hinge. The purpose of the drag hinge anddampers is to compensate for the accelerationand deceleration caused by Coriolis Effect.

Each blade can also be feathered, that is, rotatedaround its spanwise axis. Feathering the blade

means changing the pitch angle of the blade. Bychanging the pitch angle of the blades you cancontrol the thrust and direction of the main rotordisc.

Figure 5-6. On a semirigid rotor system, a teetering hinge allowsthe rotor hub and blades to flap as a unit. A static flapping stoplocated above the hub prevents excess rocking when the bladesare stopped. As the blades begin to turn, centrifugal force pullsthe static stops out of the way.

Figure 5-7. Rotor systems, such as Eurocopter’s Starflex or Bell’ssoft-in-plane, use composite material and elastomeric bearings toreduce complexity and maintenance and, thereby, increase relia -bility.

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SEMIRIGID ROTOR SYSTEMA semirigid rotor system is usually composed oftwo blades which are rigidly mounted to the mainrotor hub. The main rotor hub is free to tilt withrespect to the main rotor shaft on what is knownas a teetering hinge. This allows the blades toflap together as a unit. As one blade flaps up,the other flaps down. Since there is no verticaldrag hinge, lead-lag forces are absorbedthrough blade bending. [Figure 5-6]

RIGID ROTOR SYSTEMIn a rigid rotor system, the blades, hub, and mastare rigid with respect to each other. There are novertical or horizontal hinges so the blades cannotflap or drag, but they can be feathered. Flappingand lead/lag forces are absorbed by blade bend-ing.

COMBINATION ROTOR SYSTEMSModern rotor systems may use the combinedprinciples of the rotor systems mentioned above.Some rotor hubs incorporate a flexible hub,which allows for blade bending (flexing) withoutthe need for bearings or hinges. These systems,called flextures, are usually constructed fromcomposite material. Elastomeric bearings mayalso be used in place of conventional roller bear-ings. Elastomeric bearings are bearings con-structed from a rubber type material and havelimited movement that is perfectly suited for heli-copter applications. Flextures and elastomericbearings require no lubrication and, therefore,require less maintenance. They also absorbvibration, which means less fatigue and longerservice life for the helicopter components.[Figure 5-7]

SWASH PLATE ASSEMBLYThe purpose of the swash plate is to transmit con-trol inputs from the collective and cyclic controls tothe main rotor blades. It consists of two main parts:the stationary swash plate and the rotating swashplate. [Figure 5-8] The stationary swash plate ismounted around the main rotor mast and con-nected to the cyclic and collective controls by aseries of pushrods. It is restrained from rotating butis able to tilt in all directions and move vertically. Therotating swash plate is mounted to the stationaryswash plate by means of a bearing and is allowedto rotate with the main rotor mast. Both swashplates tilt and slide up and down as one unit. Therotating swash plate is connected to the pitchhorns by the pitch links.

FUEL SYSTEMSThe fuel system in a helicopter is made up of twogroups of components: the fuel supply system andthe engine fuel control system.

FUEL SUPPLY SYSTEMThe supply system consists of a fuel tank or tanks,fuel quantity gauges, a shut-off valve, fuel filter, afuel line to the engine, and possibly a primer andfuel pumps. [Figure 5-9]

The fuel tanks are usually mounted to the airframeas close as possible to the center of gravity. This

Figure 5-9. A typical gravity feed fuel system, in a helicopter witha reciprocating engine, contains the components shown here.Figure 5-8. Collective and cyclic control inputs are transmitted to

the stationary swash plate by control rods causing it to tilt or toslide vertically. The pitch links attached from the rotating swashplate to the pitch horns on the rotor hub transmit these move-ments to the blades.

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way, as fuel is burned off, there is a negligibleeffect on the center of gravity. A drain valvelocated on the bottom of the fuel tank allows thepilot to drain water and sediment that may havecollected in the tank. A fuel vent prevents the for-mation of a vacuum in the tank, and an overflowdrain allows for fuel to expand without rupturingthe tank. A fuel quantity gauge located on thepilot’s instrument panel shows the amount of fuelmeasured by a sensing unit inside the tank. Somegauges show tank capacity in both gallons andpounds.

The fuel travels from the fuel tank through a shut-off valve, which provides a means to completelystop fuel flow to the engine in the event of anemergency or fire. The shut-off valve remains inthe open position for all normal operations.

Most non-gravity feed fuel systems contain bothan electric pump and a mechanical engine drivenpump. The electrical pump is used to maintainpositive fuel pressure to the engine pump and alsoserves as a backup in the event of mechanicalpump failure. The electrical pump is controlled bya switch in the cockpit. The engine driven pump isthe primary pump that supplies fuel to the engineand operates any time the engine is running.

A fuel filter removes moisture and other sedimentfrom the fuel before it reaches the engine. Thesecontaminants are usually heavier than fuel andsettle to the bottom of the fuel filter sump wherethey can be drained out by the pilot.

Some fuel systems contain a small hand-operatedpump called a primer. A primer allows fuel to bepumped directly into the intake port of the cylindersprior to engine start. The primer is useful in coldweather when fuel in the carburetor is difficult tovaporize.

ENGINE FUEL CONTROL SYSTEMThe purpose of the fuel control system is to bringoutside air into the engine, mix it with fuel in theproper proportion, and deliver it to the combustionchamber.

RECIPROCATING ENGINESFuel is delivered to the cylinders by either a car-buretor or fuel injection system.

CARBURETORIn a carburetor system, air is mixed with vaporizedfuel as it passes through a venturi in the carburetor.The metered fuel/air mixture is then delivered to thecylinder intake.

Carburetors are calibrated at sea level, and thecorrect fuel-to-air mixture ratio is established atthat altitude with the mixture control set in theFULL RICH position. However, as altitudeincreases, the density of air entering the carbure-tor decreases while the density of the fuel remainsthe same. This means that at higher altitudes, themixture becomes progressively richer. To maintainthe correct fuel/air mixture, you must be able to

adjust the amount of fuel that is mixed with theincoming air. This is the function of the mixturecontrol. This adjustment, often referred to as“leaning the mixture,” varies from one aircraft toanother. Refer to the FAA-Approved RotocraftFlight Manual (RFM) to determine specific proce-dures for your helicopter. Note that most manufac-turers do not recommend leaning helicoptersin-flight.

Most mixture adjustments are required duringchanges of altitude or during operations at airportswith field elevations well above sea level. A mixturethat is too rich can result in engine roughness andreduced power. The roughness normally is due tospark plug fouling from excessive carbon buildupon the plugs. This occurs because the excessivelyrich mixture lowers the temperature inside the cylin-der, inhibiting complete combustion of the fuel. This

Figure 5-10. Carburetor ice reduces the size of the air passageto the engine. This restricts the flow of the fuel/air mixture, andreduces power.

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condition may occur during the pretakeoff runup athigh elevation airports and during climbs or cruise

flight at high altitudes. Usually, you can correct theproblem by leaning the mixture according to RFMinstructions.

If you fail to enrich the mixture during a descentfrom high altitude, it normally becomes too lean.High engine temperatures can cause excessiveengine wear or even failure. The best way to avoidthis type of situation is to monitor the engine tem-perature gauges regularly and follow the manu-facturer’s guidelines for maintaining the propermixture.

CARBURETOR ICEThe effect of fuel vaporization and decreasing airpressure in the venturi causes a sharp drop intemperature in the carburetor. If the air is moist,the water vapor in the air may condense. Whenthe temperature in the carburetor is at or belowfreezing, carburetor ice may form on internal sur-faces, including the throttle valve. [Figure 5-10]Because of the sudden cooling that takes place inthe carburetor, icing can occur even on warm dayswith temperatures as high as 38°C (100°F) andthe humidity as low as 50 percent. However, it ismore likely to occur when temperatures are below21°C (70°F) and the relative humidity is above 80percent. The likelihood of icing increases as tem-perature decreases down to 0°C (32°F), and asrelative humidity increases. Below freezing, thepossibility of carburetor icing decreases withdecreasing temperatures.

Although carburetor ice can occur during anyphase of flight, it is particularly dangerous whenyou are using reduced power, such as during adescent. You may not notice it during the descentuntil you try to add power.

Indications of carburetor icing are a decrease inengine r.p.m. or manifold pressure, the carburetorair temperature gauge indicating a temperatureoutside the safe operating range, and engineroughness. Since changes in r.p.m. or manifold

pressure can occur for a number of reasons, it isbest to closely check the carburetor air tempera-ture gauge when in possible carburetor icing con-ditions. Carburetor air temperature gauges aremarked with a yellow caution arc or green operat-ing arcs. You should refer to the FAA-ApprovedRotorcraft Flight Manual for the specific procedureas to when and how to apply carburetor heat.However, in most cases, you should keep the nee-dle out of the yellow arc or in the green arc. This isaccomplished by using a carburetor heat system,which eliminates the ice by routing air across a heat source, such as an

Figure 5-12. An electrical system scematic like this sample isincluded in most POHs. Notice that the various bus bar acces-sories are protected by circuit breakers. However, you should stillmake sure all electrical equipment is turned off before you startthe engine. This protects sensitive components, particularly theradios, from damage which may be caused by random voltagesgenerated during the starting process.

Figure 5-11. When you turn the carburetor heat ON, normal airflow is blocked, and heated air from an alternate source flowsthrough the filter to the carburetor.

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exhaust manifold, before it enters the carburetor.[Figure 5-11].

FUEL INJECTIONIn a fuel injection system, fuel and air aremetered at the fuel control unit but are not mixed.The fuel is injected directly into the intake port ofthe cylinder where it is mixed with the air justbefore entering the cylinder. This systemensures a more even fuel distribution in the cylin-ders and better vaporization, which in turn, pro-motes more efficient use of fuel. Also, the fuelinjection system eliminates the problem of car-buretor icing and the need for a carburetor heatsystem.

TURBINE ENGINESThe fuel control system on the turbine engine isfairly complex, as it monitors and adjusts manydifferent parameters on the engine. These adjust-ments are done automatically and no action isrequired of the pilot other than starting and shut-ting down. No mixture adjustment is necessary,and operation is fairly simple as far as the pilot isconcerned. New generation fuel controls incorpo-rate the use of a full authority digital engine control(FADEC) computer to control the engine’s fuelrequirements. The FADEC systems increase effi-ciency, reduce engine wear, and also reduce pilot

workload. The FADEC usually incorporates back-up systems in the event of computer failure.

ELECTRICAL SYSTEMSThe electrical systems, in most helicopters, reflectthe increased use of sophisticated avionics andother electrical accessories. More and more oper-ations in today’s flight environment are dependenton the aircraft’s electrical system; however, all hel-icopters can be safely flown without any electricalpower in the event of an electrical malfunction oremergency.

Helicopters have either a 14- or 28-volt, direct-current electrical system. On small, piston pow-e r e dhelicopters, electrical energy is supplied by anengine-driven alternator. These alternators haveadvantages over older style generators as theyare lighter in weight, require lower maintenance,and maintain a uniform electrical output even atlow engine r.p.m. [Figure 5-12]

Turbine powered helicopters use a starter/genera-tor system. The starter/generator is permanentlycoupled to the engine gearbox. When starting theengine, electrical power from the battery is sup-plied to the starter/generator, which turns theengine over. Once the engine is running, the

Figure 5-13. A typical hydraulic system for helicopters in the light to medium range is shown here.

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still exists. In this case, the circuit breaker contin-ues to pop, indicating an electrical malfunction. Afuse simply burns out when it is overloaded andneeds to be replaced. Manufacturers usually pro-vide a holder for spare fuses in the event one hasto be replaced in flight. Caution lights on theinstrument panel may be installed to show themalfunction of an electrical component.

HYDRAULICSMost helicopters, other than smaller piston pow-ered helicopters, incorporate the use of hydraulicactuators to overcome high control forces. [Figure5-13] A typical hydraulic system consists of actua-tors, also called servos, on each flight control, apump which is usually driven by the main rotorgearbox, and a reservoir to store the hydraulicfluid. A switch in the cockpit can turn the systemoff, although it is left on under normal conditions.A pressure indicator in the cockpit may also beinstalled to monitor the system.

When you make a control input, the servo is acti-vated and provides an assisting force to move therespective flight control, thus lightening the forcerequired by the pilot. These boosted flight controlsease pilot workload and fatigue. In the event ofhydraulic system failure, you are still able to con-trol the helicopter, but the control forces will bevery heavy.

In those helicopters where the control forces areso high that they cannot be moved withouthydraulic assistance, two or more independenthydraulic systems may be installed. Some heli-copters use hydraulic accumulators to store pres-sure, which can be used for a short period of timein an emergency if the hydraulic pump fails. Thisgives you enough time to land the helicopter withnormal control

STABILITY AUGMENTATIONS SYSTEMS

starter/generator is driven by the engine and isthen used as a generator.

Current from the alternator or generator is deliv-ered through a voltage regulator to a bus bar. Thevoltage regulator maintains the constant voltagerequired by the electrical system by regulating theoutput of the alternator or generator. An over-volt-age control may be incorporated to prevent exces-sive voltage, which may damage the electricalcomponents. The bus bar serves to distribute thecurrent to the various electrical components of thehelicopter.

A battery is mainly used for starting the engine. Inaddition, it permits limited operation of electricalcomponents, such as radios and lights, withoutthe engine running. The battery is also a valu-able source of standby or emergency electricalpower in the event of alternator or generator fail-ure.

An ammeter or loadmeter is used to monitor theelectrical current within the system. The amme-ter reflects current flowing to and from the bat-tery. A charging ammeter indicates that thebattery is being charged. This is normal after anengine start since the battery power used instarting is being replaced. After the battery ischarged, the ammeter should stabilize nearzero since the alternator or generator is supply-ing the electrical needs of the system. A dis -charging ammeter means the electrical load isexceeding the output of the alternator or gener-ator, and the battery is helping to supply electri-cal power. This may mean the alternator orgenerator is malfunctioning, or the electricalload is excessive. A loadmeter displays the loadplaced on the alternator or generator by theelectrical equipment. The RFM for a particularhelicopter shows the normal load to expect.Loss of the alternator or generator causes theloadmeter to indicate zero.

Electrical switches are used to select electricalcomponents. Power may be supplied directly to thecomponent or to a relay, which in turn providespower to the component. Relays are used when high currentand/or heavy electrical cables are required for aparticular component, which may exceed thecapacity of the switch.

Circuit breakers or fuses are used to protect vari-ous electrical components from overload. A circuitbreaker pops out when its respective componentis overloaded. The circuit breaker may be reset by

VOR—Ground-based navigation system consisting of very high fre-quency omnidirectional range (VOR) stations which provide courseguidance.

ILS (Instrument Landing System)—A precision instrument approachsystem, which normally consists of the following electronic compo-nents and visual aids: localizer, glide slope, outer marker, andapproach lights.

GPS (Global Positioning System)—A satellite-based radio position-ing, navigation, and time-transfer system.

IFR (Instrument Flight Rules)—Rules that govern the procedure forconducting flight in weather conditions below VFR weather mini-mums. The term IFR also is used to define weather conditions andthe type of flight plan under which an aircraft is operating.

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Some helicopters incorporate stabilityaugmentations systems (SAS) to aid in stabilizingthe helicopter in flight and in a hover. The simplestof these systems is a force trim system, whichuses a magnetic clutch and springs to hold thecyclic control in the position where it wasreleased. More advanced systems use electricservos that actually move the flight controls.These servos receive control commands from acomputer that senses helicopter attitude. Otherinputs, such as heading, speed, altitude, andnavigation information may be supplied to thecomputer to form a complete autopilot system.The SAS may be overridden or disconnected bythe pilot at any time.

Stability augmentation systems reduce pilot work-load by improving basic aircraft control harmonyand decreasing disturbances. These systems are

very useful when you are required to performother duties, such as sling loading and search andrescue operations.

AUTOPILOTHelicopter autopilot systems are similar to stabilityaugmentations systems except they haveadditional features. An autopilot can actually flythe helicopter and perform certain functionsselected by the pilot. These functions depend onthe type of autopilot and systems installed in thehelicopter.

The most common functions are altitude and head-ing hold. Some more advanced systems include avertical speed or indicated airspeed (IAS) holdmode, where a constant rate of climb/descent orindicated airspeed is maintained by the autopilot.Some autopilots have navigation capabilities,such as VOR, ILS, and GPS intercept andtracking, which is especially useful in IFR con-ditions. The most advanced autopilots can flyan instrument approach to a hover without anyadditional pilot input once the initial functionshave been selected.

The autopilot system consists of electric actuatorsor servos connected to the flight controls. Thenumber and location of these servos depends onthe type of system installed. A two-axis autopilotcontrols the helicopter in pitch and roll; one servocontrols fore and aft cyclic, and another controlsleft and right cyclic. A three-axis autopilot has anadditional servo connected to the antitorque ped-als and controls the helicopter in yaw. A four-axissystem uses a fourth servo which controls the col-lective. These servos move the respective flightcontrols when they receive control commandsfrom a central computer. This computer receivesdata input from the flight instruments for attitudereference and from the navigation equipment fornavigation and tracking reference. An autopilothas a control panel in the cockpit that allows youto select the desired functions, as well as engagethe autopilot.

For safety purposes, an automatic disengage fea-ture is usually included which automatically dis-connects the autopilot in heavy turbulence orwhen extreme flight attitudes are reached. Eventhough all autopilots can be overridden by thepilot, there is also an autopilot disengage buttonlocated on the cyclic or collective which allows youto completely disengage the autopilot withoutremoving your hands from the controls. Becauseautopilot systems and installations differ from onehelicopter to another, it is very important that you

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refer to the autopilot operating procedures locatedin the Rotorcraft Flight Manual.

ENVIRONMENTAL SYSTEMSHeating and cooling for the helicopter cabin canbe provided in different ways. The simplest formof cooling is ram air cooling. Air ducts in the frontor sides of the helicopter are opened or closed bythe pilot to let ram air into the cabin. This systemis limited as it requires forward airspeed to pro-vide airflow and also depends on the temperatureof the outside air. Air conditioning provides bettercooling but it is more complex and weighs morethan a ram air system.

Piston powered helicopters use a heat exchangershroud around the exhaust manifold to providecabin heat. Outside air is piped to the shroud andthe hot exhaust manifold heats the air, which isthen blown into the cockpit. This warm air isheated by the exhaust manifold but is not exhaustgas. Turbine helicopters use a bleed air systemfor heat. Bleed air is hot, compressed, dischargeair from the engine compressor. Hot air is ductedfrom the compressor to the helicopter cabinthrough a pilot-controlled, bleed air valve.

ANTI-ICING SYSTEMSMost anti-icing equipment installed on small helicop-ters is limited to engine intake anti-ice and pitot heatsystems. The anti-icing system found on most tur-bine-powered helicopters uses engine bleed air.The bleed air flows through the inlet guide vanes toprevent ice formation on the hollow vanes. A pilot-controlled, electrically operated valve on the com-pressor controls the air flow. The pitot heat systemuses an electrical element to heat the pitot tube,thus melting or preventing ice formation.

Airframe and rotor anti-icing may be found onsome larger helicopters, but it is not common dueto the complexity, expense, and weight of such systems.The leading edges of rotors may be heated withbleed air or electrical elements to prevent ice for-mation. Balance and control problems might arise ifice is allowed to form unevenly on the blades.Research is being done on lightweight ice-phobic (anti-icing) materials or coat-ings. These materials placed in strategic areascould significantly reduce ice formation andimprove performance.

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Title 14 of the Code of Federal Regulations (14CFR) part 91 requires that pilots comply with theoperating limitations specified in approved rotor-craft flight manuals, markings, and placards.Originally, flight manuals were often character-ized by a lack of essential information and fol-lowed whatever format and content themanufacturer felt was appropriate. This changedwith the acceptance of the General AviationManufacturers Association’s (GAMA)Specification for Pilot’s Operating Handbook,which established a standardized format for allgeneral aviation airplane and rotorcraft flight man-uals. The term “Pilot’s Operating Handbook (POH)”is often used in place of “Rotorcraft Flight Manual(RFM).” However, if “Pilot’s Operating Handbook” isused as the main title instead of “Rotorcraft FlightManual,” a statement must be included on the title

page indicating that the document is the FAA-Approved Rotorcraft Flight Manual. [Figure 6-1]

Besides the preliminary pages, an FAA-ApprovedRotorcraft Flight Manual may contain as many asten sections. These sections are: GeneralInformation; Operating Limitations; EmergencyProcedures; Normal Procedures; Performance;Weight and Balance; Aircraft and SystemsDescription; Handling, Servicing, and Maintenance;and Supplements. Manufacturers have the option ofincluding a tenth section on Safety and Operational

Tips and an alphabetical index at the end of the hand-book.

PRELIMINARY PAGESWhile rotorcraft flight manuals may appear similarfor the same make and model of aircraft, eachflight manual is unique since it contains specificinformation about a particular aircraft, such as theequipment installed, and weight and balance infor-mation. Therefore, manufacturers are required toinclude the serial number and registration on thetitle page to identify the aircraft to which the flightmanual belongs. If a flight manual does not indi-cate a specific aircraft registration and serial num-ber, it is limited to general study purposes only.

Most manufacturers include a table of contents,which identifies the order of the entire manual bysection number and title. Usually, each sectionalso contains its own table of contents. Page num-bers reflect the section you are reading, 1-1, 2-1,3-1, and so on. If the flight manual is published inlooseleaf form, each section is usually marked witha divider tab indicating the section number or title,or both. The Emergency Procedures section mayhave a red tab for quick identification and refer-ence.

GENERAL INFORMATIONThe General Information section provides thebasic descriptive information on the rotorcraft andthe powerplant. In some manuals there is a three-view drawing of the rotorcraft that provides thedimensions of various components, including theoverall length and width, and the diameter of therotor systems. This is a good place to quickly famil-iarize yourself with the aircraft.

You can find definitions, abbreviations, explana-tions of symbology, and some of the terminologyused in the manual at the end of this section. Atthe option of the manufacturer, metric and otherconversion tables may also be included.

OPERATING LIMITATIONSThe Operating Limitations section contains onlythose limitations required by regulation or that arenecessary for the safe operation of the rotorcraft,powerplant, systems, and equipment. It includes

Figure 6-1. The Rotorcraft Flight Manual is a regulatory documentin terms of the maneuvers, procedures, and operating limitationsdescribed therein.

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operating limitations, instrument markings, colorcoding, and basic placards. Some of the areasincluded are: airspeed, altitude, rotor, and power-plant limitations, including fuel and oil require-ments; weight and loading distribution; and flightlimitations.

AIRSPEED LIMITATIONSAirspeed limitations are shown on the airspeedindicator by color coding and on placards orgraphs in the aircraft. A red line on the airspeedindicator shows the airspeed limit beyond whichstructural damage could occur. This is called thenever exceed speed, or VNE. The normal operatingspeed range is depicted by a green arc. A blue lineis sometimes added to show the maximum safeautorotation speed. [Figure 6-2]

ALTITUDE LIMITATIONSIf the rotorcraft has a maximum operating densityaltitude, it is indicated in this section of the flightmanual. Sometimes the maximum altitude variesbased on different gross weights.

ROTOR LIMITATIONSLow rotor r.p.m. does not produce sufficient lift,and high r.p.m. may cause structural damage,therefore rotor r.p.m. limitations have minimumand maximum values. A green arc depicts the nor-mal operating range with red lines showing theminimum and maximum limits. [Figure 6-3]

There are two different rotor r.p.m. limitations:power-on and power-off. Power-on limitations applyanytime the engine is turning the rotor and isdepicted by a fairly narrow green band. A yellow arcmay be included to show a transition range, whichmeans that operation within this range is limited.Power-off limitations apply anytime the engine is notturning the rotor, such as when in an autorotation. Inthis case, the green arc is wider than the power-onarc, indicating a larger operating range.

POWERPLANT LIMITATIONSThe Powerplant Limitations area describes oper-ating limitations on the rotorcraft’s engine includ-ing such items as r.p.m. range, power limitations,operating temperatures, and fuel and oil require-ments. Most turbine engines and some recipro-cating engines have a maximum power and amaximum continuous power rating. The “maxi-mum power” rating is the maximum power theengine can generate and is usually limited bytime. The maximum power range is depicted by ayellow arc on the engine power instruments, witha red line indicating the maximum power that mustnot be exceeded. “Maximum continuous power” isthe maximum power the engine can generate con-

Figure 6-2. Typical airspeed indicator limitations and markings.

Figure 6-3. Markings on a typical dual-needle tachometer in areciprocating-engine helicopter. The outer band shows the limitsof the superimposed needles when the engine is turning the rotor.The inner band indicates the power-off limits.

Figure 6-4. Torque and turbine outlet temperature (TOT) gaugesare commonly used with turbine-powered aircraft.

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tinually, and is depicted by a green arc. [Figure 6-4]

Like on a torque and turbine outlet temperaturegauge, the red line on a manifold pressure gaugeindicates the maximum amount of power. A yellowarc on the gauge warns of pressures approachingthe limit of rated power. A placard near the gaugelists the maximum readings for specific conditions.[Figure 6-5]

WEIGHT AND LOADING DISTRIBUTIONThe Weight and Loading Distribution area containsthe maximum certificated weights, as well as thecenter of gravity (CG) range. The location of the ref-erence datum used in balance computations shouldalso be included in this section. Weight and balancecomputations are not provided here, but rather inthe Weight and Balance Section of the FAA-Approved Rotocraft Flight Manual.

FLIGHT LIMITATIONSThis area lists any maneuvers which are prohib-ited, such as acrobatic flight or flight into knownicing conditions. If the rotorcraft can only beflown in VFR conditions, it will be noted in thisarea. Also included are the minimum crewrequirements, and the pilot seat location, if appli-cable, where solo flights must be conducted.

PLACARDSAll rotorcraft generally have one or more placardsdisplayed that have a direct and important bearingon the safe operation of the rotorcraft. These plac-ards are located in a conspicuous place within thecabin and normally appear in the LimitationsSection. Since VNE changes with altitude, thisplacard can be found in all helicopters. [Figure 6-6]

EMERGENCY PROCEDURESConcise checklists describing the recommendedprocedures and airspeeds for coping with varioustypes of emergencies or critical situations can befound in this section. Some of the emergenciescovered include: engine failure in a hover and ataltitude, tail rotor failures, fires, and systems fail-ures. The procedures for restarting an engine andfor ditching in the water might also be included.

Manufacturers may first show the emergencieschecklists in an abbreviated form with the order ofitems reflecting the sequence of action. This is fol-lowed by amplified checklists providing additionalinformation to help you understand the procedure.To be prepared for an abnormal or emergency sit-uation, memorize the first steps of each checklist,if not all the steps. If time permits, you can thenrefer to the checklist to make sure all items havebeen covered. (For more information on emergen-cies, refer to Chapter 11—Helicopter Emergenciesand Chapter 21—Gyroplane Emergencies.)

Manufacturers also are encouraged to include anoptional area titled “Abnormal Procedures,” whichdescribes recommended procedures for handlingmalfunctions that are not considered to be emer-gencies. This information would most likely be foundin larger helicopters.

Figure 6-5. A manifold pressure gauge is commonly used with pis-ton-powered aircraft.

Figure 6-6. Various VNE placards.

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PERFORMANCEThe Performance Section contains all the infor-mation required by the regulations, and any addi-tional performance information the manufacturerfeels may enhance your ability to safely operatethe rotorcraft. These charts, graphs, and tablesvary in style but all contain the same basic infor-mation. Some examples of the performanceinformation that can be found in most flight man-uals include a calibrated versus indicated air-speed conversion graph, hovering ceiling versusgross weight charts, and a height-velocity dia-gram. [Figure 6-7] For information on how to usethe charts, graphs, and tables, refer to Chapter8—Performance.

WEIGHT AND BALANCEThe Weight and Balance section should containall the information required by the FAA that is nec-essary to calculate weight and balance. To helpyou correctly compute the proper data, most man-ufacturers include sample problems. (Weight andbalance is further discussed in Chapter 7—Weightand Balance.)

AIRCRAFT AND SYSTEMSDESCRIPTIONThe Aircraft and Systems Description section isan excellent place to study and familiarize your-self with all the systems found on your aircraft.The manufacturers should describe the systemsin a manner that is understandable to most pilots.For larger, more complex rotorcraft, the manufac-turer may assume a higher degree of knowledge.(For more information on rotorcraft systems, referto Chapter 5—Helicopter Systems and Chapter18—Gyroplane Systems.)

HANDLING, SERVICING, ANDMAINTENANCEThe Handling, Servicing, and Maintenance sec-tion describes the maintenance and inspectionsrecommended by the manufacturer, as well asthose required by the regulations, andAirworthiness Directive (AD) compliance proce-dures. There are also suggestions on how theAirworthiness Directive (AD)—Aregulatory notice that is sent outby the FAA to the registered own-ers of aircraft informing them ofthe discovery of a condition thatkeeps their aircraft from continu-ing to meet its conditions for air-worthiness. AirworthinessDirectives must be complied withwithin the required time limit, andthe fact of compliance, the dateof compliance, and the method ofcompliance must be recorded inthe aircraft maintenance records.

NORMAL PROCEDURESThe Normal Procedures is the section you willprobably use the most. It usually begins with alisting of the airspeeds, which may enhance thesafety of normal operations. It is a good idea tomemorize the airspeeds that are used for normalflight operations. The next part of the sectionincludes several checklists, which take youthrough the preflight inspection, before starting

procedure, how to start the engine, rotor engage-ment, ground checks, takeoff, approach, landing,and shutdown. Some manufacturers also includethe procedures for practice autorotations. To avoidskipping an important step, you should always usea checklist when one is available. (More informa-tion on maneuvers can be found in Chapter 9—Basic Maneuvers, Chapter 10—AdvancedManeuvers, and Chapter 20—Gyroplane FlightOperations.)

Figure 6-7. One of the performance charts in the PerformanceSection is the “In Ground Effect Hover Ceiling versus GrossWeight” chart. This chart allows you to determine how muchweight you can carry and still operate at a specific pressure alti-tude, or if you are carrying a specific weight, what is your altitudelimitation.

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It is vital to comply with weight and balance limitsestablished for helicopters. Operating above themaximum weight limitation compromises thestructural integrity of the helicopter and adverselyaffects performance. Balance is also criticalbecause on some fully loaded helicopters, centerof gravity deviations as small as three inches candramatically change a helicopter’s handling char-acteristics. Taking off in a helicopter that is notwithin the weight and balance limitations isunsafe.

WEIGHTWhen determining if your helicopter is within theweight limits, you must consider the weight of thebasic helicopter, crew, passengers, cargo, andfuel. Although the effective weight (load factor)varies during maneuvering flight, this chapter pri-marily considers the weight of the loaded helicop-ter while at rest.

The following terms are used when computing ahelicopter’s weight.

BASIC EMPTY WEIGHT—The starting point forweight computations is the basic empty weight,which is the weight of the standard helicopter,optional equipment, unusable fuel, and fulloperating fluids including full engine oil. Somehelicopters might use the term “licensed emptyweight,” which is nearly the same as basic emptyweight, except that it does not include full engineoil, just undrainable oil. If you fly a helicopter thatlists a licensed empty weight, be sure to add theweight of the oil to your computations.

USEFUL LOAD—The difference between thegross weight and the basic empty weight isreferred to as useful load. It includes the flightcrew, usable fuel, drainable oil, if applicable, andpayload.

PAYLOAD—The weight of the passengers, cargo,and baggage.

GROSS WEIGHT—The sum of the basic emptyweight and useful load.

MAXIMUM GROSS WEIGHT— The maximumweight of the helicopter. Most helicopters have an

internal maximum gross weight, which refers to theweight within the helicopter structure and an exter-nal maximum gross weight, which refers to theweight of the helicopter with an external load.

WEIGHT LIMITATIONSWeight limitations are necessary to guarantee thestructural integrity of the helicopter, as well asenabling you to predict helicopter performanceaccurately. Although aircraft manufacturers buildin safety factors, you should never intentionallyexceed the load limits for which a helicopter is cer-tificated. Operating above a maximum weightcould result in structural deformation or failureduring flight if you encounter excessive load fac-tors, strong wind gusts, or turbulence. Operatingbelow a minimum weight could adversely affectthe handling characteristics of the helicopter.During single-pilot operations in some helicopters,you may have to use a large amount of forwardcyclic in order to maintain a hover. By adding bal-last to the helicopter, the cyclic will be closer to thecenter, which gives you a greater range of controlmotion in every direction. Additional weight alsoimproves autorotational characteristics since theautorotational descent can be established sooner.In addition, operating below minimum weightcould prevent you from achieving the desirablerotor r.p.m. during autorotations.

Although a helicopter is certificated for a specifiedmaximum gross weight, it is not safe to take offwith this load under all conditions. Anything thatadversely affects takeoff, climb, hovering, andlanding performance may require off-loading offuel, passengers, or baggage to some weight lessthan the published maximum. Factors which canaffect performance include high altitude, high tem-perature, and high humidity conditions, whichresult in a high density altitude.

DETERMINING EMPTY WEIGHTA helicopter’s weight and balance records containessential data, including a complete list of allinstalled optional equipment. Use these records todetermine the weight and balance condition of theempty helicopter.

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When a helicopter is delivered from the factory, thebasic empty weight, empty weight center of gravity(CG), and useful load are recorded on a weight andbalance data sheet included in the FAA-ApprovedRotocraft Flight Manual. The basic empty weightcan vary even in the same model of helicopterbecause of differences in installed equipment. Ifthe owner or operator of a helicopter has equip-ment removed, replaced, or additional equipmentinstalled, these changes must be reflected in theweight and balance records. In addition, majorrepairs or alterations must be recorded by a certi-fied mechanic. When the revised weight andmoment are recorded on a new form, the oldrecord is marked with the word “superseded” anddated with the effective date of the new record.This makes it easy to determine which weight andbalance form is the latest version. You must usethe latest weight and balance data for computingall loading problems.

BALANCEHelicopter performance is not only affected bygross weight, but also by the position of that weight.It is essential to load the aircraft within the allow-able center-of-gravity range specified in the rotor-craft flight manual’s weight and balance limitations.

CENTER OF GRAVITY (CG)The center of gravity is defined as the theoreticalpoint where all of the aircraft’s weight is consideredto be concentrated. If a helicopter was suspendedby a cable attached to the center-of-gravity point, itwould balance like a teeter-totter. For helicopterswith a single main rotor, the CG is usually close tothe main rotor mast.

Improper balance of a helicopter’s load can resultin serious control problems. The allowable rangein which the CG may fall is called the “CG range.”The exact CG location and range are specified inthe rotorcraft flight manual for each helicopter. Inaddition to making a helicopter difficult to control,an out-of-balance loading condition alsodecreases maneuverability since cyclic control is

less effective in the direction opposite to the CGlocation.

Ideally, you should try to perfectly balance a heli-copter so that the fuselage remains horizontal inhovering flight, with no cyclic pitch control neededexcept for wind correction. Since the fuselage actsas a pendulum suspended from the rotor, chang-ing the center of gravity changes the angle atwhich the aircraft hangs from the rotor. When thecenter of gravity is directly under the rotor mast,the helicopter hangs horizontal; if the CG is too farforward of the mast, the helicopter hangs with itsnose tilted down; if the CG is too far aft of themast, the nose tilts up. [Figure 7-1]

CG FORWARD OF FORWARD LIMITA forward CG may occur when a heavy pilot andpassenger take off without baggage or proper bal-last located aft of the rotor mast. This situationbecomes worse if the fuel tanks are located aft ofthe rotor mast because as fuel burns the weightlocated aft of the rotor mast becomes less.

You can recognize this condition when coming to ahover following a vertical takeoff. The helicopter willhave a nose-low attitude, and you will need exces-sive rearward displacement of the cyclic control tomaintain a hover in a no-wind condition. You shouldnot continue flight in this condition, since you couldrapidly run out of rearward cyclic control as youconsume fuel. You also may find it impossible todecelerate sufficiently to bring the helicopter to astop. In the event of engine failure and the resultingautorotation, you may not have enough cyclic con-trol to flare properly for the landing.

A forward CG will not be as obvious when hoveringinto a strong wind, since less rearward cyclic dis-placement is required than when hovering with nowind. When determining whether a critical balancecondition exists, it is essential to consider the windvelocity and its relation to the rearward displace-ment of the cyclic control.

Figure 7-1. The location of the center of gravity strongly influences how the helicopter handles.

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CG AFT OF AFT LIMITWithout proper ballast in the cockpit, exceedingthe aft CG may occur when:

• A lightweight pilot takes off solo with a fullload of fuel located aft of the rotor mast.

• A lightweight pilot takes off with maximumbaggage allowed in a baggage compartmentlocated aft of the rotor mast.

• A lightweight pilot takes off with a combina-tion of baggage and substantial fuel whereboth are aft of the rotor mast.

You can recognize the aft CG condition whencoming to a hover following a vertical takeoff.The helicopter will have a tail-low attitude, andyou will need excessive forward displacement ofcyclic control to maintain a hover in a no-windcondition. If there is a wind, you need evengreater forward cyclic.

If flight is continued in this condition, you may findit impossible to fly in the upper allowable airspeedrange due to inadequate forward cyclic authority tomaintain a nose-low attitude. In addition, with anextreme aft CG, gusty or rough air could acceleratethe helicopter to a speed faster than that producedwith full forward cyclic control. In this case, dissym-metry of lift and blade flapping could cause therotor disc to tilt aft. With full forward cyclic controlalready applied, you might not be able to lower therotor disc, resulting in possible loss of control, orthe rotor blades striking the tailboom.

LATERAL BALANCEFor most helicopters, it is usually not necessaryto determine the lateral CG for normal flightinstruction and passenger flights. This isbecause helicopter cabins are relatively narrowand most optional equipment is located near thecenter line. However, some helicopter manualsspecify the seat from which you must conductsolo flight. In addition, if there is an unusual sit-uation, such as a heavy pilot and a full load offuel on one side of the helicopter, which couldaffect the lateral CG, its position should bechecked against the CG envelope. If carryingexternal loads in a position that requires largelateral cyclic control displacement to maintainlevel flight, fore and aft cyclic effectivenesscould be dramatically limited.

WEIGHT AND BALANCECALCULATIONSWhen determining whether your helicopter isproperly loaded, you must answer two questions:

1. Is the gross weight less than or equal to themaximum allowable gross weight?

2. Is the center of gravity within the allowableCG range, and will it stay within the allowablerange as fuel is burned off?

To answer the first question, just add the weight ofthe items comprising the useful load (pilot, pas-sengers, fuel, oil, if applicable, cargo, and bag-gage) to the basic empty weight of the helicopter.Check that the total weight does not exceed the max-imum allowable gross weight.

To answer the second question, you need to use CGor moment information from loading charts, tables,or graphs in the rotorcraft flight manual. Then usingone of the methods described below, calculate theloaded moment and/or loaded CG and verify that itfalls within the allowable CG range shown in therotorcraft flight manual.

Figure 7-2. When making weight and balance computations,always use actual weights if they are available, especially if thehelicopter is loaded near the weight and balance limits.

Figure 7-3. While the horizontal reference datum can be any-where the manufacturer chooses, most small training helicoptershave the horizontal reference datum 100 inches forward of themain rotor shaft centerline. This is to keep all the computed val-ues positive.

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It is important to note that any weight and balancecomputation is only as accurate as the informationprovided. Therefore, you should ask passengerswhat they weigh and add a few pounds to cover theadditional weight of clothing, especially during the

winter months. The baggage weight should bedetermined by the use of a scale, if practical. If ascale is not available, be conservative and overesti-mate the weight. Figure 7-2 indicates the standardweights for specific operating fluids.

The following terms are used when computing ahelicopter’s balance.

REFERENCE DATUM—Balance is determined bythe location of the CG, which is usually describedas a given number of inches from the referencedatum. The horizontal reference datum is animaginary vertical plane or point, arbitrarily fixedsomewhere along the longitudinal axis of the heli-copter, from which all horizontal distances aremeasured for weight and balance purposes.There is no fixed rule for its location. It may belocated at the rotor mast, the nose of the helicop-

ter, or even at a point in space ahead of the heli-copter. [Figure 7-3]

The lateral reference datum, is usually located atthe center of the helicopter. The location of thereference datums is established by the manufac-turer and is defined in the rotorcraft flight manual.[Figure 7-4]

ARM—The horizontal distance from the datum toany component of the helicopter or to any objectlocated within the helicopter is called the arm.Another term that can be used interchangeablywith arm is station. If the component or object islocated to the rear of the datum, it is measuredas a positive number and usually is referred toas inches aft of the datum. Conversely, if thecomponent or object is located forward of thedatum, it is indicated as a negative number andis usually referred to as inches forward of thedatum.

MOMENT—If the weight of an object is multipliedby its arm, the result is known as its moment. Youmay think of moment as a force that results froman object’s weight acting at a distance. Moment isalso referred to as the tendency of an object torotate or pivot about a point. The farther an objectis from a pivotal point, the greater its force.

CENTER OF GRAVITY COMPUTATION—By totaling theweights and moments of all components andobjects carried, you can determine the point wherea loaded helicopter would balance. This point isknown as the center of gravity.

Figure 7-4. The lateral reference datum is located longitudinallythrough the center of the helicopter; therefore, there are positiveand negative values.

Figure 7-5. In this example, the helicopter’s weight of 1,700pounds is recorded in the first column, its CG or arm of 116.5inches in the second, and its moment of 198,050 pound-inches inthe last. Notice that the weight of the helicopter, multiplied by itsCG, equals its moment.

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WEIGHT AND BALANCE METHODSSince weight and balance is so critical to the safeoperation of a helicopter, it is important to knowhow to check this condition for each loadingarrangement. Most helicopter manufacturers useone of two methods, or a combination of the meth-ods, to check weight and balance conditions.

COMPUTATIONAL METHODWith the computational method, you use simplemathematics to solve weight and balance prob-lems. The first step is to look up the basic emptyweight and total moment for the particular helicop-ter you fly. If the center of gravity is given, it shouldalso be noted. The empty weight CG can be con-sidered the arm of the empty helicopter. Thisshould be the first item recorded on the weightand balance form. [Figure 7-5]

Next, the weights of the oil, if required, pilot, pas-sengers, baggage, and fuel are recorded. Usecare in recording the weight of each passengerand baggage. Recording each weight in its properlocation is extremely important to the accurate cal-culation of a CG. Once you have recorded all ofthe weights, add them together to determine thetotal weight of the loaded helicopter.

Now, check to see that the total weight does notexceed the maximum allowable weight underexisting conditions. In this case, the total weight ofthe helicopter is under the maximum gross weightof 3,200 pounds.

Once you are satisfied that the total weight iswithin prescribed limits, multiply each individualweight by its associated arm to determine its

moment. Then, add the moments together toarrive at the total moment for the helicopter. Yourfinal computation is to find the center of gravity ofthe loaded helicopter by dividing the total momentby the total weight.

After determining the helicopter’s weight andcenter of gravity location, you need to deter-mine if the CG is within acceptable limits. In thisexample, the allowable range is between 106.0inches and 114.2 inches. Therefore, the CGlocation is within the acceptable range. If theCG falls outside the acceptable limits, you willhave to adjust the loading of the helicopter.

LOADING CHART METHODYou can determine if a helicopter is within weightand CG limits using a loading chart similar to theone in figure 7-6. To use this chart, first subtotalthe empty weight, pilot, and passengers. This isthe weight at which you enter the chart on the left.The next step is to follow the upsloping lines forbaggage and then for fuel to arrive at your finalweight and CG. Any value on or inside the enve-lope is within the range.

SAMPLE PROBLEM 1Determine if the gross weight and center of grav-ity are within allowable limits under the followingloading conditions for a helicopter based on theloading chart in figure 7-6.

To use the loading chart for the helicopter in thisexample, you must add up the items in a certainorder. The maximum allowable gross weight is1,600 pounds.

ITEM POUNDSBasic empty weight 1,040Pilot 135Passenger 200Subtotal 1,375 (point A)Baggage compartment load 25Subtotal 1,400 (pointB)Fuel load (30 gallons) 180Total weight 1,580 (pointC)

1. Follow the green arrows in figure 7-6. Enterthe graph on the left side at 1,375 lb., thesubtotal of the empty weight and the passen-ger weight. Move right to the yellow line.(point A)

Figure 7-6. Loading chart illustrating the solution to sample prob-lems 1 and 2.

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2. Move up and to the right, parallel to the bag-gage compartment loading lines to 1,400 lb.(Point B)

3. Continue up and to the right, this time paral-lel to the fuel loading lines, to the total weightof 1,580 lb. (Point C).

Point C is within allowable weight and CG limits.

SAMPLE PROBLEM 2Assume that the pilot in sample problem 1 dis-charges the passenger after using only 20 poundsof fuel.

ITEM POUNDSBasic empty weight 1,040Pilot 135Subtotal 1,175 (pointD)Baggage compartment load 25Subtotal 1,200 (pointE)Fuel load 160

Total weight 1,360 (point F)

Follow the blue arrows in figure 7-6, starting at1,175 lb. on the left side of the graph, then to pointD, E, and F. Although the total weight of the heli-copter is well below the maximum allowable gross

weight, point F falls outside the aft allowable CGlimit.

As you can see, it is important to reevaluate the bal-ance in a helicopter whenever you change the load-ing. Unlike most airplanes, where discharging apassenger is unlikely to adversely affect the CG,off-loading a passenger from a helicopter couldmake the aircraft unsafe to fly. Another differencebetween helicopter and airplane loading is thatmost small airplanes carry fuel in the wings very

near the center of gravity. Burning off fuel has littleeffect on the loaded CG. However, helicopter fueltanks are often significantly behind the center ofgravity. Consuming fuel from a tank aft of the rotormast causes the loaded helicopter CG to move for-ward. As standard practice, you should computethe weight and balance with zero fuel to verify thatyour helicopter remains within the acceptable limitsas fuel is used.

SAMPLE PROBLEM 3The loading chart used in the sample problems 1and 2 is designed to graphically calculate theloaded center of gravity and show whether it iswithin limits, all on a single chart. Another type ofloading chart calculates moments for each station.

Figure 7-7. Moments for fuel, pilot, and passenger.

Figure 7-8. CG/Moment Chart.

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You must then add up these moments and consultanother graph to determine whether the total iswithin limits. Although this method has moresteps, the charts are sometimes easier to use.

To begin, record the basic empty weight of the hel-icopter, along with its total moment. Remember touse the actual weight and moment of the helicop-ter you are flying. Next, record the weights of thepilot, passengers, fuel, and baggage on a weightand balance worksheet. Then, determine the totalweight of the helicopter. Once you have deter-mined the weight to be within prescribed limits,compute the moment for each weight and for theloaded helicopter. Do this with a loading graphprovided by the manufacturer. Use figure 7-7 todetermine the moments for a pilot and passengerweighing 340 pounds and for 211 pounds of fuel.

Start at the bottom scale labeled LOAD WEIGHT.Draw a line from 211 pounds up to the line labeled“FUEL @ STA108.5.” Draw your line to the left tointersect the MOMENT scale and read the fuelmoment (22.9 thousand lb.-inches). Do the samefor the pilot/passenger moment. Draw a line from aweight of 340 pounds up to the line labeled “PILOT& PASSENGER @STA. 83.2.” Go left and read the

Figure 7-9. Use the longitudinal CG envelope along with the computed CGs to determine if the helicopter is loaded properly.

Figure 7-10. Computed Lateral CG.

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pilot/passenger moment (28.3 thousand lb.-inches).

Reduction factors are often used to reduce thesize of large numbers to manageable levels. In fig-ure 7-7, the scale on the loading graph gives youmoments in thousands of pound-inches. In mostcases, when using this type of chart, you need notbe concerned with reduction factors because the

Figure 7-11. Use the lateral CG envelope to determine if the heli-copter is properly loaded.

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Your ability to predict the performance of a heli-copter is extremely important. It allows you todetermine how much weight the helicopter cancarry before takeoff, if your helicopter can safelyhover at a specific altitude and temperature, howfar it will take to climb above obstacles, and whatyour maximum climb rate will be.

FACTORS AFFECTING PERFORMANCEA helicopter’s performance is dependent on thepower output of the engine and the lift productionof the rotors, whether it is the main rotor(s) or tailrotor. Any factor that affects engine and rotor effi-ciency affects performance. The three major fac-tors that affect performance are density altitude,weight, and wind.

DENSITY ALTITUDEThe density of the air directly affects the perform-ance of the helicopter. As the density of the airincreases, engine power output, rotor efficiency,and aerodynamic lift all increase. Density altitudeis the altitude above mean sea level at which agiven atmospheric density occurs in the standardatmosphere. It can also be interpreted as pres-sure altitude corrected for nonstandard tempera-ture differences.

Pressure altitude is displayed as the height abovea standard datum plane, which, in this case, is atheoretical plane where air pressure is equal to29.92 in. Hg. Pressure altitude is the indicatedheight value on the altimeter when the altimetersetting is adjusted to 29.92 in. Hg. Pressure alti-tude, as opposed to true altitude, is an important

value for calculating performance as it moreaccurately represents the air content at a particu-lar level. The difference between true altitude andpressure altitude must be clearly understood.True altitude means the vertical height abovemean sea level and is displayed on the altimeterwhen the altimeter is correctly adjusted to thelocal setting.

For example, if the local altimeter setting is 30.12in. Hg., and the altimeter is adjusted to this value,the altimeter indicates exact height above sealevel. However, this does not reflect conditionsfound at this height under standard conditions.Since the altimeter setting is more than 29.92 in.Hg., the air in this example has a higher pressure,and is more compressed, indicative of the airfound at a lower altitude. Therefore, the pressurealtitude is lower than the actual height abovemean sea level.

To calculate pressure altitude without the use ofan altimeter, remember that the pressuredecreases approximately 1 inch of mercury forevery 1,000-foot increase in altitude. For exam-ple, if the current local altimeter setting at a 4,000-foot elevation is 30.42, the pressure altitude wouldbe 3,500 feet. (30.42 – 29.92 = .50 in. Hg. 3 1,000feet = 500 feet. Subtracting 500 feet from 4,000equals 3,500 feet).

The four factors that most affect density altitudeare: atmospheric pressure, altitude, temperature,and the moisture content of the air.

Density Altitude—Pressure altitude corrected for nonstandard tem -perature variations. Performance charts for many older aircraft arebased on this value.

Standard Atmosphere—At sea level, the standard atmosphere con-sists of a barometric pressure of 29.92 inches of mercury (in. Hg.) or1013.2 millibars, and a temperature of 15°C (59°F). Pressure andtemperature normally decrease as altitude increases. The standardlapse rate in the lower atmosphere for each 1,000 feet of altitude isapproximately 1 in. Hg. and 2°C (3.5°F). For example, the standardpressure and temperature at 3,000 feet mean sea level (MSL) is26.92 in. Hg. (29.92 – 3) and 9°C (15°C – 6°C).

Pressure Altitude—The height above the standard pressure level of29.92 in. Hg. It is obtained by setting 29.92 in the barometric pres-sure window and reading the altimeter.

True Altitude—The actual height of an object above mean sea level.

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ATMOSPHERIC PRESSUREDue to changing weather conditions, atmosphericpressure at a given location changes from day today. If the pressure is lower, the air is less dense.This means a higher density altitude and less hel-icopter performance.

ALTITUDEAs altitude increases, the air becomes thinner orless dense. This is because the atmospheric pres-sure acting on a given volume of air is less, allow-ing the air molecules to move further apart. Denseair contains more air molecules spaced closelytogether, while thin air contains less air moleculesbecause they are spaced further apart. As altitudeincreases, density altitude increases.

TEMPERATURETemperature changes have a large affect on den-sity altitude. As warm air expands, the air mole-cules move further apart, creating less dense air.Since cool air contracts, the air molecules movecloser together, creating denser air. High temper-atures cause even low elevations to have highdensity altitudes.

MOISTURE (HUMIDITY)The water content of the air also changes air den-sity because water vapor weighs less than dry air.Therefore, as the water content of the airincreases, the air becomes less dense, increasingdensity altitude and decreasing performance.

Humidity, also called “relative humidity,” refers tothe amount of water vapor contained in the atmos-phere, and is expressed as a percentage of themaximum amount of water vapor the air can hold.This amount varies with temperature; warm aircan hold more water vapor, while colder air canhold less. Perfectly dry air that contains no watervapor has a relative humidity of 0 percent, whilesaturated air that cannot hold any more watervapor, has a relative humidity of 100 percent.

Humidity alone is usually not considered animportant factor in calculating density altitude andhelicopter performance; however, it does con-tribute. There are no rules-of-thumb or chartsused to compute the effects of humidity on densityaltitude, so you need to take this into considera-tion by expecting a decrease in hovering and take-off performance in high humidity conditions.

HIGH AND LOW DENSITY ALTITUDE CONDITIONSYou need to thoroughly understand the terms“high density altitude” and “low density altitude.” Ingeneral, high density altitude refers to thin air,while low density altitude refers to dense air.Those conditions that result in a high density alti-tude (thin air) are high elevations, low atmos-pheric pressure, high temperatures, high humidity,or some combination thereof. Lower elevations,high atmospheric pressure, low temperatures,and low humidity are more indicative of low den-sity altitude (dense air). However, high densityaltitudes may be present at lower elevations onhot days, so it is important to calculate the den-sity altitude and determine performance before aflight.

One of the ways you can determine density alti-tude is through the use of charts designed for thatpurpose. [Figure 8-1]. For example, assume youare planning to depart an airport where the fieldelevation is 1,165 feet MSL, the altimeter settingis 30.10, and the temperature is 70°F. What is thedensity altitude? First, correct for nonstandardpressure (30.10) by referring to the right side ofthe chart, and subtracting 165 feet from the fieldelevation. The result is a pressure altitude of1,000 feet. Then, enter the chart at the bottom,just above the temperature of 70°F (21°C).Proceed up the chart vertically until you interceptthe diagonal 1,000-foot pressure altitude line,then move horizontally to the left and read thedensity altitude of approximately 2,000 feet. Thismeans your helicopter will perform as if it were at2,000 feet MSL on a standard day.

Most performance charts do not require you tocompute density altitude. Instead, the computa-tion is built into the performance chart itself. Allyou have to do is enter the chart with the correctpressure altitude and the temperature.

WEIGHTLift is the force that opposes weight. As weightincreases, the power required to produce the liftneeded to compensate for the added weight mustalso increase. Most performance charts includeweight as one of the variables. By reducing theweight of the helicopter, you may find that you areable to safely take off or land at a location that oth-erwise would be impossible. However, if you areever in doubt about whether you can safely per-form a takeoff or landing, you should delay yourtakeoff until more favorable density altitude condi-tions exist. If airborne, try to land at a location thathas more favorable conditions, or one where youcan make a landing that does not require a hover.

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In addition, at higher gross weights, the increasedpower required to hover produces more torque,which means more antitorque thrust is required. Insome helicopters, during high altitude operations,the maximum antitorque produced by the tail rotorduring a hover may not be sufficient to overcometorque even if the gross weight is within limits.

WINDSWind direction and velocity also affect hovering,takeoff, and climb performance. Translational liftoccurs anytime there is relative airflow over therotor disc. This occurs whether the relative airflowis caused by helicopter movement or by the wind.As wind speed increases, translational liftincreases, resulting in less power required tohover.

The wind direction is also an important considera-tion. Headwinds are the most desirable as theycontribute to the most increase in performance.Strong crosswinds and tailwinds may require theuse of more tail rotor thrust to maintain directionalcontrol. This increased tail rotor thrust absorbspower from the engine, which means there is lesspower available to the main rotor for the produc-tion of lift. Some helicopters even have a criticalwind azimuth or maximum safe relative wind

chart. Operating the helicopter beyond these lim-its could cause loss of tail rotor effectiveness.

Takeoff and climb performance is greatly affectedby wind. When taking off into a headwind, effec-tive translational lift is achieved earlier, resulting inmore lift and a steeper climb angle. When takingoff with a tailwind, more distance is required toaccelerate through translation lift.

PERFORMANCE CHARTSIn developing performance charts, aircraft manu-facturers make certain assumptions about thecondition of the helicopter and the ability of thepilot. It is assumed that the helicopter is in goodoperating condition and the engine is developingits rated power. The pilot is assumed to be follow-ing normal operating procedures and to haveaverage flying abilities. Average means a pilot

Figure 8-1. Density Altitude Chart.

In Ground Effect (IGE) Hover—Hovering close to the surface (usuallyless than one rotor diameter above the surface) under the influenceof ground effect.

Out of Ground Effect (OGE) Hover—Hovering greater than one rotordiameter distance above the surface. Because induced drag isgreater while hovering out of ground effect, it takes more power toachieve a hover. See Chapter 3—Aerodynamics of Flight for moredetails on IGE and OGE hover.

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As density altitude increases, more power isrequired to hover. At some point, the powerrequired is equal to the power available. Thisestablishes the hovering ceiling under the existingconditions. Any adjustment to the gross weight byvarying fuel, payload, or both, affects the hoveringceiling. The heavier the gross weight, the lowerthe hovering ceiling. As gross weight isdecreased, the hover ceiling increases.

SAMPLE PROBLEM 1You are to fly a photographer to a remote locationto take pictures of the local wildlife. Using figure 8-2, can you safely hover in ground effect at yourdeparture point with the following conditions?

Pressure Altitude ..........................8,000 feetTemperature .......................................+15°CTakeoff Gross Weight .............1,250 poundsR.P.M...................................................104%

First enter the chart at 8,000 feet pressure altitude(point A), then move right until reaching a pointmidway between the +10°C and +20°C lines

Figure 8-3. Out of Ground Effect Hover Ceiling versus GrossWeight Chart.

capable of doing each of the required tasks cor-rectly and at the appropriate times.

Using these assumptions, the manufacturerdevelops performance data for the helicopterbased on actual flight tests. However, they donot test the helicopter under each and everycondition shown on a performance chart.Instead, they evaluate specific data and math-ematically derive the remaining data.

HOVERING PERFORMANCEHelicopter performance revolves around whetheror not the helicopter can be hovered. More poweris required during the hover than in any other flightregime. Obstructions aside, if a hover can be main-tained, a takeoff can be made, especially with theadditional benefit of translational lift. Hover chartsare provided for in ground effect (IGE) hover andout of ground effect (OGE) hover under variousconditions of gross weight, altitude, temperature,and power. The “in ground effect” hover ceiling isusually higher than the “out of ground effect” hoverceiling because of the added lift benefit producedby ground effect.

Figure 8-2. In Ground Effect Hover Ceiling versus Gross WeightChart.

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(point B). From that point, proceed down to findthe maximum gross weight where a 2 foot hovercan be achieved. In this case, it is approximately1,280 pounds (point C). Since the gross weight ofyour helicopter is less than this, you can safelyhover with these conditions.

SAMPLE PROBLEM 2Once you reach the remote location in the previ-ous problem, you will need to hover out of groundeffect for some of the pictures. The pressure alti-tude at the remote site is 9,000 feet, and you willuse 50 pounds of fuel getting there. (The newgross weight is now 1,200 pounds.) The tempera-ture will remain at +15°C. Using figure 8-3, canyou accomplish the mission?

Enter the chart at 9,000 feet (point A) and proceedto point B (+15°C). From there determine that themaximum gross weight to hover out of groundeffect is approximately 1,130 pounds (point C).Since your gross weight is higher than this value,you will not be able to hover with these conditions.To accomplish the mission, you will have toremove approximately 70 pounds before youbegin the flight.

These two sample problems emphasize the impor-tance of determining the gross weight and hover ceil-ing throughout the entire flight operation. Being ableto hover at the takeoff location with a certain grossweight does not ensure the same performance at the

landing point. If the destination point is at a higherdensity altitude because of higher elevation, temper-ature, and/or relative humidity, more power isrequired to hover. You should be able to predictwhether hovering power will be available at the desti-nation by knowing the temperature and wind condi-tions, using the performance charts in the helicopterflight manual, and making certain power checks dur-ing hover and in flight prior to commencing theapproach and landing.

TAKEOFF PERFORMANCEIf takeoff charts are included in the rotorcraft flightmanual, they usually indicate the distance it takes toclear a 50-foot obstacle based on various conditionsof weight, pressure altitude, and temperature. Inaddition, the values computed in the takeoff chartsusually assume that the flight profile is per the appli-cable height-velocity diagram.

SAMPLE PROBLEM 3In this example, determine the distance to clear a50-foot obstacle with the following conditions:

Pressure Altitude ..........................5,000 feetTakeoff Gross Weight .............2,850 poundsTemperature..........................................95°F

Using figure 8-4, locate 2,850 pounds in the firstcolumn. Since the pressure altitude of 5,000 feetis not one of the choices in column two, you haveto interpolate between the values from the 4,000-and 6,000-foot lines. Follow each of these rows

Figure 8-4. Takeoff Distance Chart.

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out to the column headed by 95°F. The values are1,102 feet and 1,538 feet. Since 5,000 is halfwaybetween 4,000 and 6,000, the interpolated valueshould be halfway between these two values or1,320 feet ([1,102 + 1,538] 4 2 = 1,320).

CLIMB PERFORMANCEMost of the factors affecting hover and takeoff per-formance also affect climb performance. In addi-tion, turbulent air, pilot techniques, and overallcondition of the helicopter can cause climb per-formance to vary.

A helicopter flown at the “best rate-of-climb”speed will obtain the greatest gain in altitudeover a given period of time. This speed is nor-mally used during the climb after all obstacleshave been cleared and is usually maintaineduntil reaching cruise altitude. Rate of climb mustnot be confused with angle of climb. Angle ofclimb is a function of altitude gained over a givendistance. The best rate-of-climb speed results inthe highest climb rate, but not the steepest climbangle and may not be sufficient to clear obstruc-tions. The “best angle-of-climb” speed dependsupon the power available. If there is a surplus ofpower available, the helicopter can climb verti-cally, so the best angle-of-climb speed is zero.

Wind direction and speed have an effect on climbperformance, but it is often misunderstood.Airspeed is the speed at which the helicopter ismoving through the atmosphere and is unaffectedby wind. Atmospheric wind affects only the

Figure 8-5. Maximum Rate-of-Climb Chart.

Figure 8-6. This chart uses density altitude in determining maxi-mum rate of climb.

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From the previous chapters, it should be apparentthat no two helicopters perform the same way.Even when flying the same model of helicopter,wind, temperature, humidity, weight, and equip-ment make it difficult to predict just how the heli-copter will perform. Therefore, this chapterpresents the basic flight maneuvers in a way thatwould apply to a majority of the helicopters. Inmost cases, the techniques described apply tosmall training helicopters with:

• A single, main rotor rotating in a counter-clockwise direction (looking downward onthe rotor).

• An antitorque system.

Where a technique differs, it will be noted. Forexample, a power increase on a helicopter with aclockwise rotor system requires right antitorquepedal pressure instead of left pedal pressure. Inmany cases, the terminology “apply proper pedalpressure” is used to indicate both types of rotor sys-tems. However, when discussing throttle coordina-tion to maintain proper r.p.m., there will be nodifferentiation between those helicopters with agovernor and those without. In a sense, the gover-nor is doing the work for you. In addition, instead ofusing the terms collective pitch control and thecyclic pitch control throughout the chapter, thesecontrols are referred to as just collective and cyclic.

Because helicopter performance varies with dif-ferent weather conditions and aircraft loading,specific nose attitudes and power settings will notbe discussed. In addition, this chapter does notdetail each and every attitude of a helicopter inthe various flight maneuvers, nor each and everymove you must make in order to perform a givenmaneuver.

When a maneuver is presented, there will be abrief description, followed by the technique toaccomplish the maneuver. In most cases, there isa list of common errors at the end of the discus-sion.

PREFLIGHTBefore any flight, you must ensure the helicopteris airworthy by inspecting it according to the rotor-craft flight manual, pilot’s operating handbook, orother information supplied either by the operatoror the manufacturer. Remember that as pilot incommand, it is your responsibility to ensure theaircraft is in an airworthy condition.

In preparation for flight, the use of a checklist isimportant so that no item is overlooked. Follow themanufacturer’s suggested outline for both theinside and outside inspection. This ensures that allthe items the manufacturer feels are important arechecked. Obviously, if there are other items youfeel might need attention, inspect them as well.

MINIMUM EQUIPMENT LISTS (MELS) ANDOPERATIONS WITH INOPERATIVEEQUIPMENTThe Code of Federal Regulations (CFRs) requiresthat all aircraft instruments and installed equip-ment be operative prior to each departure.However, when the FAA adopted the minimumequipment list (MEL) concept for 14 CFR part 91operations, flights were allowed with inoperativeitems, as long as the inoperative items were deter-mined to be nonessential for safe flight. At thesame time, it allowed part 91 operators, withoutan MEL, to defer repairs on nonessential equip-ment within the guidelines of part 91.

There are two primary methods of deferring mainte-nance on rotorcraft operating under part 91. Theyare the deferral provision of 14 CFR part 91, section91.213(d) and an FAA-approved MEL.

The deferral provision of section 91.213(d) iswidely used by most pilot/operators. Its popularityis due to simplicity and minimal paperwork. When

Minimum Equipment List (MEL)—An inventory of instruments andequipment that may legally be inoperative, with the specific condi-tions under which an aircraft may be flown with such items inopera-

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inoperative equipment is found during preflight orprior to departure, the decision should be to cancelthe flight, obtain maintenance prior to flight, or todefer the item or equipment.

Maintenance deferrals are not used for in-flight dis-crepancies. The manufacturer's RFM/POH proce-dures are to be used in those situations. Thediscussion that follows assumes that the pilot wishes to defermaintenance that would ordinarily be required priorto flight.

Using the deferral provision of section 91.213(d),the pilot determines whether the inoperative equip-ment is required by type design, the CFRs, or ADs.If the inoperative item is not required, and the heli-copter can be safely operated without it, the defer-ral may be made. The inoperative item shall bedeactivated or removed and an INOPERATIVEplacard placed near the appropriate switch, control,or indicator. If deactivation or removal involvesmaintenance (removal always will), it must beaccomplished by certificated maintenance person-nel.

For example, if the position lights (installed equip-ment) were discovered to be inoperative prior to adaytime flight, the pilot would follow the require-ments of section 91.213(d).

The deactivation may be a process as simple asthe pilot positioning a circuit breaker to the OFFposition, or as complex as rendering instrumentsor equipment totally inoperable. Complex mainte-nance tasks require a certificated and appropri-ately rated maintenance person to perform thedeactivation. In all cases, the item or equipmentmust be placarded INOPERATIVE.

All rotorcraft operated under part 91 are eligible touse the maintenance deferral provisions of section91.213(d). However, once an operator requests anMEL, and a Letter of Authorization (LOA) is issuedby the FAA, then the use of the MEL becomesmandatory for that helicopter. All maintenancedeferrals must be accomplished in accordance withthe terms and conditions of the MEL and the opera-tor-generated procedures document.

The use of an MEL for rotorcraft operated underpart 91 also allows for the deferral of inoperativeitems or equipment. The primary guidancebecomes the FAA-approved MEL issued to thatspecific operator and N-numbered helicopter.

The FAA has developed master minimum equip-ment lists (MMELs) for rotorcraft in current use.Upon written request by a rotorcraft operator, thelocal FAA Flight Standards District Office (FSDO)may issue the appropriate make and modelMMEL, along with an LOA, and the preamble. Theoperator then develops operations and mainte-nance (O&M) procedures from the MMEL. ThisMMEL with O&M procedures now becomes theoperator's MEL. The MEL, LOA, preamble, andprocedures document developed by the operatormust be on board the helicopter when it is oper-ated.

The FAA considers an approved MEL to be a sup-plemental type certificate (STC) issued to an air-craft by serial number and registration number. Ittherefore becomes the authority to operate that air-craft in a condition other than originally type certifi-cated.

With an approved MEL, if the position lights werediscovered inoperative prior to a daytime flight, thepilot would make an entry in the maintenance recordor discrepancy record provided for that purpose.The item is then either repaired or deferred in accor-dance with the MEL. Upon confirming that daytimeflight with inoperative position lights is acceptable inaccordance with the provisions of the MEL, the pilotwould leave the position lights switch OFF, open thecircuit breaker (or whatever action is called for in theprocedures document), and placard the positionlight switch as INOPERATIVE.

There are exceptions to the use of the MEL fordeferral. For example, should a component fail thatis not listed in the MEL as deferrable (the rotortachometer, engine tachometer, or cyclic trim, forexample), then repairs are required to be per-formed prior to departure. If maintenance or partsare not readily available at that location, a special flight permit can be obtainedfrom the nearest FSDO. This permit allows the hel-icopter to be flown to another location for mainte-nance. This allows an aircraft that may notcurrently meet applicable airworthiness require-ments, but is capable of safe flight, to be operatedunder the restrictive special terms and conditionsattached to the special flight permit.

Deferral of maintenance is not to be taken lightly,and due consideration should be given to the effectan inoperative component may have on the opera-tion of a helicopter, particularly if other items are inopera-tive. Further information regarding MELs and oper-ations with inoperative equipment can be found in

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AC 91-67, Minimum Equipment Requirements forGeneral Aviation Operations Under FAR Part 91.

ENGINE START AND ROTOR ENGAGEMENTDuring the engine start, rotor engagement, andsystems ground check, use the manufacturer’schecklists. If a problem arises, have it checkedbefore continuing. Prior to performing thesetasks, however, make sure the area near thehelicopter is clear of personnel and equipment.Helicopters are safe and efficient flyingmachines as long as they are operated withinthe parameters established by the manufacturer.

ROTOR SAFETY CONSIDERATIONSThe exposed nature of the main and tail rotorsdeserve special caution. You must exerciseextreme care when taxiing near hangars orobstructions since the distance between the rotorblade tips and obstructions is very difficult tojudge. [Figure 9-1] In addition, you cannot see thetail rotor of some helicopters from the cabin.Therefore, when hovering backwards or turning inthose helicopters, allow plenty of room for tail rotorclearance. It is a good practice to glance over yourshoulder to maintain this clearance.

Another rotor safety consideration is the thrust ahelicopter generates. The main rotor system iscapable of blowing sand, dust, snow, ice, andwater at high velocities for a significant distancecausing injury to nearby people and damage tobuildings, automobiles, and other aircraft. Loosesnow, can severely reduce visibility and obscureoutside visual references. Any airborne debris nearthe helicopter can be ingested into the engine airintake or struck by the main and tail rotor blades.

SAFETY IN AND AROUND HELICOPTERSPeople have been injured, some fatally, in helicop-ter accidents that would not have occurred had

they been informed of the proper method ofboarding or deplaning. A properly briefed passen-ger should never be endangered by a spinningrotor. The simplest method of avoiding accidentsof this sort is to stop the rotors before passengersare boarded or allowed to depart. Because thisaction is not always practicable, and to realize thevast and unique capabilities of the helicopter, it isoften necessary to take on passengers or todeplane them while the engine and rotors areturning. To avoid accidents, it is essential that allpersons associated with helicopter operations,including passengers, be made aware of all possi-ble hazards and instructed as to how they can beavoided.

Persons directly involved with boarding or deplan-ing passengers, aircraft servicing, rigging, orhooking up external loads, etc., should beinstructed as to their duties. It would be difficult, ifnot impossible, to cover each and every type ofoperation related to helicopters. A few of the moreobvious and common ones are covered below.

RAMP ATTENDANTS AND AIRCRAFT SERVICINGPERSONNEL—These personnel should beinstructed as to their specific duties, and theproper method of fulfilling them. In addition, theramp attendant should be taught to:

1. keep passengers and unauthorized personsout of the helicopter landing and takeoff area.

2. brief passengers on the best way toapproach and board a helicopter with itsrotors turning.

AIRCRAFT SERVICING—The helicopter rotorblades should be stopped, and both the aircraftand the refueling unit properly grounded prior toany refueling operation. You, as the pilot, shouldensure that the proper grade of fuel and theproper additives, when required, are being dis-pensed.

Refueling the aircraft, while the blades are turn-ing, known as "hot refueling," may be practical forcertain types of operation. However, this can behazardous if not properly conducted. Pilots shouldremain at the flight controls; and refueling person-nel should be knowledgeable about the properrefueling procedures and properly briefed for spe-cific helicopter makes and models.

Refueling units should be positioned to ensureadequate rotor blade clearance. Persons not

Figure 9-1. Exercise extreme caution when hovering near build-ings or other aircraft.

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involved with the refueling operation should keepclear of the area.

Smoking must be prohibited in and around the air-craft during all refueling operations.

EXTERNAL-LOAD RIGGERS—Rigger training ispossibly one of the most difficult and continuallychanging problems of the helicopter external-loadoperator. A poorly rigged cargo net, light standard,or load pallet could result in a serious and costlyaccident. It is imperative that all riggers be thor-oughly trained to meet the needs of each individ-ual external-load operation. Since riggingrequirements may vary several times in a singleday, proper training is of the utmost importance tosafe operations.

PILOT AT THE FLIGHT CONTROLS—Many heli-copter operators have been lured into a "quickturnaround" ground operation to avoid delays atairport terminals and to minimize stop/start cyclesof the engine. As part of this quick turnaround, thepilot might leave the cockpit with the engine androtors turning. Such an operation can beextremely hazardous if a gust of wind disturbs therotor disc, or the collective flight control movescausing lift to be generated by the rotor system.Either occurrence may cause the helicopter to rollor pitch, resulting in a rotor blade striking the tail-boom or the ground. Good operating proceduresdictate that pilots remain at the flight controlswhenever the engine is running and the rotors areturning.

EXTERNAL-LOAD HOOKUP PERSONNEL—There are several areas in which these personnelshould be knowledgeable. First, they shouldknow the lifting capability of the helicoptersinvolved. Since some operators have helicoptermodels with almost identical physical characteris-tics but different lifting capabilities, this knowl-edge is essential. For example, a hookup personmay be working with a turbocharged helicopteron a high altitude project when a non-tur-bocharged helicopter, which looks exactly thesame to the ground crew, comes to pick up aload. If the hookup person attaches a load greaterthan the non-turbocharged helicopter can handle, a poten-tially dangerous situation could exist.

Second, know the pilots. The safest plan is tostandardize all pilots in the manner in which slingloads are picked up and released. Without pilotstandardization, the operation could be haz-ardous. The operator should standardize the

pilots on operations while personnel are beneath the helicopter.

Third, know the cargo. Many items carried viasling are very fragile, others can take a beating.The hookup person should always know when ahazardous article is involved and the nature of thehazard, such as explosives, radioactive materials,and toxic chemicals. In addition to knowing this,the hookup person should be familiar with thetypes of protective gear or clothing and the actionsnecessary to protect their own safety and that ofthe operation.

Fourth, know appropriate hand signals. Whendirect radio communications between ground andflight personnel are not used, the specific mean-ing of hand signals should be coordinated prior to operations.

Fifth, know emergency procedures. Ground andflight personnel should fully agree to and under-stand the actions to be taken by all participants inthe event of emergencies. This prior planning isessential to avoid injuries to all concerned.

PASSENGERS—All persons who board a helicop-ter while its rotors are turning should be instructedin the safest means of doing so. Naturally, if youare at the controls, you may not be able to con-duct a boarding briefing. Therefore, the individualwho arranged for the passengers' flight or isassigned as the ramp attendant should accom-plish this task. The exact procedures may varyslightly from one helicopter model to another, butin general the following should suffice.

When boarding—

1. stay away from the rear of the helicopter.

2. approach or leave the helicopter in a crouch-ing manner.

3. approach from the side or front, but never outof the pilot's line of vision.

4. carry tools horizontally, below waist level,never upright or over the shoulder.

5. hold firmly to hats and loose articles.

6. never reach up or dart after a hat or otherobject that might be blown off or away.

7. protect eyes by shielding them with a handor by squinting.

8. if suddenly blinded by dust or a blowingobject, stop and crouch lower; or better yet,sit down and wait for help.

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9. never grope or feel your way toward or awayfrom the helicopter.

Since few helicopters carry cabin attendants, you,as the pilot, will have to conduct the pre-takeoffand pre-landing briefings. The type of operationdictates what sort of briefing is necessary. All brief-ings should include the following:

1. The use and operation of seatbelts for take-off, en route, and landing.

2. For overwater flights, the location and use offlotation gear and other survival equipmentthat might be on board. You should alsoinclude how and when to abandon the heli-copter should a ditching be necessary.

3. For flights over rough or isolated terrain, alloccupants should be told where maps andsurvival gear are located.

4. Passengers should be instructed as to whatactions and precautions to take in the eventof an emergency, such as the body positionfor best spinal protection against a high verti-cal impact landing (erect with back firmlyagainst the seat back); and when and how toexit after landing. Ensure that passengersare aware of the location of the fire extin-guisher and survival equipment.

5. Smoking should not be permitted within 50feet of an aircraft on the ground. Smokingcould be permitted, at the discretion of thepilot, except under the following conditions:

• during all ground operations.

• during, takeoff or landing.

• when carrying flammable or hazardous materials.

When passengers are approaching or leaving ahelicopter that is sitting on a slope with the rotorsturning, they should approach and depart down-hill. This affords the greatest distance between therotor blades and the ground. If this involves walk-ing around the helicopter, they should always goaround the front, never the rear.

VERTICAL TAKEOFF TO A HOVERA vertical takeoff, or takeoff to a hover, is amaneuver in which the helicopter is raised verti-cally from the surface to the normal hovering alti-tude (2 to 5 feet) with a minimum of lateral orlongitudinal movement.

TECHNIQUEPrior to any takeoff or maneuver, you shouldensure that the area is clear of other traffic. Then,head the helicopter into the wind, if possible.Place the cyclic in the neutral position, with thecollective in the full down position. Increase thethrottle smoothly to obtain and maintain properr.p.m., then raise the collective. Use smooth, con-tinuous movement, coordinating the throttle tomaintain proper r.p.m. As you increase the collec-tive, the helicopter becomes light on the skids,and torque tends to cause the nose to swing oryaw to the right unless sufficient left antitorquepedal is used to maintain the heading. (On heli-copters with a clockwise main rotor system, theyaw is to the left and right pedal must be applied.)

As the helicopter becomes light on the skids,make necessary cyclic pitch control adjustmentsto maintain a level attitude. When airborne, usethe antitorque pedals to maintain heading and thecollective to ensure continuous vertical assent tothe normal hovering altitude. When hovering alti-tude is reached, use the throttle and collective tocontrol altitude, and the cyclic to maintain a sta-tionary hover. Use the antitorque pedals to main-tain heading. When a stabilized hover is achieved,check the engine instruments and note the powerrequired to hover. You should also note the posi-tion of the cyclic. Cyclic position varies with windand the amount and distribution of the load.

Excessive movement of any flight control requiresa change in the other flight controls. For example,if while hovering, you drift to one side, you natu-rally move the cyclic in the opposite direction.When you do this, part of the vertical thrust isdiverted, resulting in a loss of altitude. To maintainaltitude, you must increase the collective. Thisincreases drag on the blades and tends to slowthem down. To counteract the drag and maintainr.p.m., you need to increase the throttle. Increasedthrottle means increased torque, so you must addmore pedal pressure to maintain the heading. Thiscan easily lead to overcontrolling the helicopter.However, as your level of proficiency increases,problems associated with overcontrollingdecrease.

COMMON ERRORS1. Failing to ascend vertically as the helicopter

becomes airborne.

2. Pulling through on the collective after becom-ing airborne, causing the helicopter to gaintoo much altitude.

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3. Overcontrolling the antitorque pedals, whichnot only changes the handling of the helicop-ter, but also changes the r.p.m.

4. Reducing throttle rapidly in situations whereproper r.p.m. has been exceeded. This usu-ally results in exaggerated heading changesand loss of lift, resulting in loss of altitude.

HOVERINGHovering is a maneuver in which the helicopter ismaintained in a nearly motionless flight over a ref-erence point at a constant altitude and on a con-stant heading. The maneuver requires a highdegree of concentration and coordination.

TECHNIQUETo maintain a hover over a point, you should lookfor small changes in the helicopter’s attitude andaltitude. When you note these changes, make thenecessary control inputs before the helicopterstarts to move from the point. To detect small vari-ations in altitude or position, your main area ofvisual attention needs to be some distance fromthe aircraft, using various points on the helicopteror the tip-path plane as a reference. Looking tooclose or looking down leads to overcontrolling.Obviously, in order to remain over a certain point,you should know where the point is, but yourattention should not be focused there.

As with a takeoff, you control altitude with the col-lective and maintain a constant r.p.m. with thethrottle. Use the cyclic to maintain the helicopter’sposition and the pedals to control heading. Tomaintain the helicopter in a stabilized hover, make small,smooth, coordinated corrections. As the desiredeffect occurs, remove the correction in order tostop the helicopter’s movement. For example, ifthe helicopter begins to move rearward, you needto apply a small amount of forward cyclic pres-sure. However, neutralize this pressure just beforethe helicopter comes to a stop, or it will begin tomove forward.

After you gain experience, you will develop a cer-tain “feel” for the helicopter. You will feel and seesmall deviations, so you can make the correctionsbefore the helicopter actually moves. A certainrelaxed looseness develops, and controlling thehelicopter becomes second nature, rather than amechanical response.

COMMON ERRORS1. Tenseness and slow reactions to movements

of the helicopter.

2. Failure to allow for lag in cyclic and collectivepitch, which leads to overcontrolling.

Figure 9-2. Left turns in helicopters with a counterclockwise rotating main rotor are more difficult to execute because the tail rotordemands more power. This requires that you compensate with additional collective pitch and increased throttle. You might want to refer tothis graphic throughout the remainder of the discussion on a hovering turn to the left.

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3. Confusing attitude changes for altitudechanges, which result in improper use of thecontrols.

4. Hovering too high, creating a hazardousflight condition.

5. Hovering too low, resulting in occasionaltouchdown.

HOVERING TURNA hovering turn is a maneuver performed at hov-ering altitude in which the nose of the helicopter isrotated either left or right while maintaining posi-tion over a reference point on the surface. Themaneuver requires the coordination of all flightcontrols and demands precise control near thesurface. You should maintain a constant altitude,rate of turn, and r.p.m.

TECHNIQUEInitiate the turn in either direction by applying anti-torque pedal pressure toward the desired direc-tion. It should be noted that during a turn to theleft, you need to add more power because leftpedal pressure increases the pitch angle of the tailrotor, which, in turn, requires additional powerfrom the engine. A turn to the right requires lesspower. (On helicopters with a clockwise rotatingmain rotor, right pedal increases the pitch angleand, therefore, requires more power.)

As the turn begins, use the cyclic as necessary(usually into the wind) to keep the helicopter overthe desired spot. To continue the turn, you need toadd more and more pedal pressure as the heli-copter turns to the crosswind position. This isbecause the wind is striking the tail surface andtail rotor area, making it more difficult for the tail toturn into the wind. As pedal pressures increasedue to crosswind forces, you must increase thecyclic pressure into the wind to maintain position.Use the collective with the throttle to maintain aconstant altitude and r.p.m. [Figure 9-2]

After the 90° portion of the turn, you need todecrease pedal pressure slightly to maintain thesame rate of turn. Approaching the 180°, ordownwind, portion, you need to anticipate oppo-site pedal pressure due to the tail moving from anupwind position to a downwind position. At thispoint, the rate of turn has a tendency to increaseat a rapid rate due to the weathervaning tendencyof the tail surfaces. Because of the tailwind condi-tion, you need to hold rearward cyclic pressure tokeep the helicopter over the same spot.

Because of the helicopter’s tendency to weather-vane, maintaining the same rate of turn from the180° position actually requires some pedal pres-sure opposite the direction of turn. If you do notapply opposite pedal pressure, the helicoptertends to turn at a faster rate. The amount of pedalpressure and cyclic deflection throughout theturn depends on the wind velocity. As you finishthe turn on the upwind heading, apply oppositepedal pressure to stop the turn. Gradually applyforward cyclic pressure to keep the helicopterfrom drifting.

Control pressures and direction of applicationchange continuously throughout the turn. Themost dramatic change is the pedal pressure (andcorresponding power requirement) necessary tocontrol the rate of turn as the helicopter movesthrough the downwind portion of the maneuver.

Turns can be made in either direction; however,in a high wind condition, the tail rotor may not beable to produce enough thrust, which means youwill not be able to control a turn to the right in acounterclockwise rotor system. Therefore, if con-trol is ever questionable, you should first attemptto make a 90° turn to the left. If sufficient tail rotorthrust exists to turn the helicopter crosswind ina left turn, a right turn can be successfully con-trolled. The opposite applies to helicopters withclockwise rotor systems. In this case, youshould start your turn to the right. Hoveringturns should be avoided in winds strong

Figure 9-3. To maintain a straight ground track, use two referencepoints in line and at some distance in front of the helicopter.

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enough to preclude sufficient aft cyclic con-trol to maintain the helicopter on the selectedsurface reference point when headed down-

wind. Check the fl ight manual for the manu -facturer’s recommendations for thislimitation.

COMMON ERRORS1. Failing to maintain a slow, constant rate of

turn.

2. Failing to maintain position over the refer-ence point.

3. Failing to maintain r.p.m. within normalrange.

4. Failing to maintain constant altitude.

5. Failing to use the antitorque pedals properly.

HOVERING—FORWARD FLIGHTYou normally use forward hovering flight to move a helicopter to a specific location, and it is usuallybegun from a stationary hover. During the maneu-ver, constant groundspeed, altitude, and headingshould be maintained.

TECHNIQUEBefore starting, pick out two references directly infront and in line with the helicopter. These refer-

ence points should be kept in line throughout themaneuver. [Figure 9-3]

Begin the maneuver from a normal hovering alti-tude by applying forward pressure on the cyclic. Asmovement begins, return the cyclic toward theneutral position to keep the groundspeed at a slowrate—no faster than a brisk walk. Throughout themaneuver, maintain a constant groundspeedand path over the ground with the cyclic, a con-stant heading with the antitorque pedals, alti-tude with the collective, and the proper r.p.m. withthe throttle.

To stop the forward movement, apply rewardcyclic pressure until the helicopter stops. As for-ward motion stops, return the cyclic to the neutralposition to prevent rearward movement. Forwardmovement can also be stopped by simply apply-ing rearward pressure to level the helicopter andlet it drift to a stop.

COMMON ERRORS1. Exaggerated movement of the cyclic, result-

ing in erratic movement over the surface.

2. Failure to use the antitorque pedals properly,resulting is excessive heading changes.

3. Failure to maintain desired hovering altitude.

4. Failure to maintain proper r.p.m.

HOVERING—SIDEWARD FLIGHTSideward hovering flight may be necessary tomove the helicopter to a specific area when con-ditions make it impossible to use forward flight.During the maneuver, a constant groundspeed,altitude, and heading should be maintained.

TECHNIQUEBefore starting sideward hovering flight, makesure the area you are going to hover into is clear.Then pick two points of reference in a line in thedirection of sideward hovering flight to help youmaintain the proper ground track. These referencepoints should be kept in line throughout themaneuver. [Figure 9-4]

Begin the maneuver from a normal hovering alti-tude by applying cyclic toward the side in whichthe movement is desired. As the movementbegins, return the cyclic toward the neutral posi-tion to keep the groundspeed at a slow rate—nofaster than a brisk walk. Throughout the maneu-ver, maintain a constant groundspeed andground track with cyclic. Maintain heading,

Figure 9-4. The key to hovering sideward is establishing at leasttwo reference points that help you maintain a straight track overthe ground while keeping a constant heading.

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ground track, with the antitorque pedals, and aconstant altitude with the collective. Use thethrottle to maintain the proper operating r.p.m.

To stop the sideward movement, apply cyclicpressure in the direction opposite to that ofmovement and hold it until the helicopterstops. As motion stops, return the cyclic to theneutral position to prevent movement in theopposite direction. Applying sufficient oppositecyclic pressure to level the helicopter may also

stop sideward movement. The helicopter thendrifts to a stop.

COMMON ERRORS1. Exaggerated movement of the cyclic, result-

ing in overcontrolling and erratic movementover the surface.

2. Failure to use proper antitorque pedal con-trol, resulting in excessive heading change.

3. Failure to maintain desired hovering altitude.

4. Failure to maintain proper r.p.m.

5. Failure to make sure the area is clear prior tostarting the maneuver.

HOVERING—REARWARD FLIGHTRearward hovering flight may be necessary tomove the helicopter to a specific area when the sit-uation is such that forward or sideward hoveringflight cannot be used. During the maneuver, main-tain a constant groundspeed, altitude, and head-ing. Due to the limited visibility behind a helicopter,it is important that you make sure that the areabehind the helicopter is cleared before beginningthe maneuver. Use of ground personnel is recom-mended.

TECHNIQUEBefore starting rearward hovering flight, pick outtwo reference points in front of, and in line with thehelicopter just like you would if you were hoveringforward. [Figure 9-3] The movement of the heli-copter should be such that these points remain inline.

Begin the maneuver from a normal hovering alti-tude by applying rearward pressure on the cyclic.After the movement has begun, position the cyclicto maintain a slow groundspeed (no faster than abrisk walk). Throughout the maneuver, maintainconstant groundspeed and ground track with thecyclic, a constant heading with the antitorque ped-als, constant altitude with the collective, and theproper r.p.m. with the throttle.

To stop the rearward movement, apply forwardcyclic and hold it until the helicopter stops. As the

motion stops, return the cyclic to the neutral posi-tion. Also, as in the case of forward and sidewardhovering flight, opposite cyclic can be used tolevel the helicopter and let it drift to a stop.

Figure 9-5. Hover taxi.

Figure 9-6. Air taxi.

Figure 9-7. Surface taxi.

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COMMON ERRORS1. Exaggerated movement of the cyclic result-

ing in overcontrolling and an uneven move-ment over the surface.

2. Failure to use the antitorque pedals properly,resulting in excessive heading change.

3. Failure to maintain desired hovering altitude.

4. Failure to maintain proper r.p.m.

5. Failure to make sure the area is clear prior tostarting the maneuver.

TAXIINGTaxiing refers to operations on, or near the sur-face of taxiways or other prescribed routes. In hel-icopters, there are three different types of taxiing.

HOVER TAXIA "hover taxi" is used when operating below 25feet AGL. [Figure 9-5] Since hover taxi is just likeforward, sideward, or rearward hovering flight, thetechnique to perform it will not be presented here.

AIR TAXIAn "air taxi" is preferred when movements requiregreater distances within an airport or heliportboundary. [Figure 9-6] In this case, you basicallyfly to your new location; however, you areexpected to remain below 100 feet AGL, and toavoid overflight of other aircraft, vehicles, and per-sonnel.

TECHNIQUEBefore starting, determine the appropriate air-speed and altitude combination to remain out ofthe cross-hatched or shaded areas of the height-

velocity diagram. Additionally, be aware of cross-wind conditions that could lead to loss of tail rotoreffectiveness. Pick out two references directly infront of the helicopter for the ground path desired.These reference points should be kept in linethroughout the maneuver.

Begin the maneuver from a normal hovering alti-tude by applying forward pressure on the cyclic.As movement begins, attain the desired airspeedwith the cyclic. Control the desired altitude withthe collective, and r.p.m. with the throttle.Throughout the maneuver, maintain a desiredgroundspeed and ground track with the cyclic, aconstant heading with antitorque pedals, thedesired altitude with the collective, and properoperating r.p.m. with the throttle.

To stop the forward movement, apply aft cyclicpressure to reduce forward speed. Simultaneouslylower the collective to initiate a descent to hover alti-tude. As forward motion stops, return the cyclic to the neutralposition to prevent rearward movement. When at theproper hover altitude, increase the collective as nec-essary.

COMMON ERRORS1. Erratic movement of the cyclic, resulting in

improper airspeed control and erratic move-ment over the surface.

2. Failure to use antitorque pedals properly,resulting in excessive heading changes.

3. Failure to maintain desired altitude.

4. Failure to maintain proper r.p.m.

Figure 9-8. The helicopter takes several positions during a normal takeoff from a hover. The numbered positions in the text refer to thenumbers in this illustration.

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5. Overflying parked aircraft causing possibledamage from rotor downwash.

6. Flying in the cross-hatched or shaded areaof the height-velocity diagram.

7. Flying in a crosswind that could lead to lossof tail rotor effectiveness.

SURFACE TAXIA "surface taxi," for those helicopters with wheels,is used whenever you wish to minimize the effectsof rotor downwash. [Figure 9-7]

TECHNIQUEThe helicopter should be in a stationary positionon the surface with the collective full down and ther.p.m. the same as that used for a hover. Thisr.p.m. should be maintained throughout themaneuver. Then, move the cyclic slightly forwardand apply gradual upward pressure on the collec-tive to move the helicopter forward along the sur-face. Use the antitorque pedals to maintainheading and the cyclic to maintain ground track.The collective controls starting, stopping, andspeed while taxiing. The higher the collectivepitch, the faster the taxi speed; however, youshould not taxi faster than a brisk walk. If your hel-icopter is equipped with brakes, use them to helpyou slow down. Do not use the cyclic to controlgroundspeed.

During a crosswind taxi, hold the cyclic into thewind a sufficient amount to eliminate any driftingmovement.

COMMON ERRORS1. Improper use of cyclic.

2. Failure to use antitorque pedals for heading control.

3. Improper use of the controls during cross-wind operations.

4. Failure to maintain proper r.p.m.

NORMAL TAKEOFF FROM A HOVERA normal takeoff from a hover is an orderly transi-tion to forward flight and is executed to increasealtitude safely and expeditiously. During the take-off, fly a profile that avoids the cross-hatched orshaded areas of the height-velocity diagram.

TECHNIQUERefer to figure 9-8 (position 1). Bring the helicop-ter to a hover and make a performance check,

which includes power, balance, and flight controls.The power check should include an evaluation ofthe amount of excess power available; that is, thedifference between the power being used to hoverand the power available at the existing altitudeand temperature conditions. The balance condi-tion of the helicopter is indicated by the position ofthe cyclic when maintaining a stationary hover.Wind will necessitate some cyclic deflection, butthere should not be an extreme deviation from

neutral. Flight controls must move freely, and thehelicopter should respond normally. Then visu-ally clear the area all around.

Start the helicopter moving by smoothly and slowlyeasing the cyclic forward (position 2). As the heli-copter starts to move forward, increase the collec-

Figure 9-9. During a slip, the rotor disc is tilted into the wind.

Figure 9-10. To compensate for wind drift at altitude, crab the hel-icopter into the wind.

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tive, as necessary, to prevent the helicopter fromsinking and adjust the throttle to maintain r.p.m.The increase in power requires an increase in theproper antitorque pedal to maintain heading.Maintain a straight takeoff path throughout thetakeoff. As you accelerate through effective trans-lational lift (position 3), the helicopter begins toclimb and the nose tends to rise due to increasedlift. At this point adjust the collective to obtain nor-mal climb power and apply enough forward cyclicto overcome the tendency of the nose to rise. Atposition 4, hold an attitude that allows a smoothacceleration toward climbing airspeed and a com-mensurate gain in altitude so that the takeoff pro-file does not take you through any of thecross-hatched or shaded areas of the height-v e l o c i t y

diagram. As airspeed increases (position 5), thestreamlining of the fuselage reduces engine torqueeffect, requiring a gradual reduction of antitorquep e d a lpressure. As the helicopter continues to climb andaccelerate to best rate of climb, apply aft cyclicpressure to raise the nose smoothly to the normalclimb attitude.

COMMON ERRORS1. Failing to use sufficient collective pitch to

prevent loss of altitude prior to attainingtranslational lift.

2. Adding power too rapidly at the beginning of thetransition from hovering to forward flight withoutforward cyclic compensation, causing the heli-copter to gain excessive altitude before acquir-ing airspeed.

3. Assuming an extreme nose-down attitudenear the surface in the transition from hov-ering to forward flight.

4. Failing to maintain a straight flight path overthe surface (ground track).

5. Failing to maintain proper airspeed duringthe climb.

6. Failing to adjust the throttle to maintainproper r.p.m.

NORMAL TAKEOFF FROM THESURFACENormal takeoff from the surface is used to movethe helicopter from a position on the surface intoeffective translational lift and a normal climb usinga minimum amount of power. If the surface isdusty or covered with loose snow, this techniqueprovides the most favorable visibility conditionsand reduces the possibility of debris beingingested by the engine.

TECHNIQUEPlace the helicopter in a stationary position on thesurface. Lower the collective to the full down posi-tion, and reduce the r.p.m. below operating r.p.m.Visually clear the area and select terrain features,or other objects, to aid in maintaining the desiredtrack during takeoff and climb out. Increase thethrottle to the proper r.p.m. and raise the collec-tive slowly until the helicopter is light on the skids.Hesitate momentarily and adjust the cyclic andantitorque pedals, as necessary, to prevent anysurface movement. Continue to apply upward col-lective and, as the helicopter breaks ground, usethe cyclic, as necessary, to begin forward move-ment as altitude is gained. Continue to acceler-ate, and as effective translational lift is attained,the helicopter begins to climb. Adjust attitude andpower, if necessary, to climb in the same manneras a takeoff from a hover.

COMMOM ERRORS1. Departing the surface in an attitude that is

too nose-low. This situation requires the useof excessive power to initiate a climb.

Figure 9-11. You can maintain a straight-and-level attitude bykeeping the tip-path plane parallel to and a constant distanceabove or below the natural horizon. For any given airspeed, thisdistance remains the same as long as you sit in the same positionin the same type of aircraft.

Figure 9-12. During a level, coordinated turn, the rate of turn iscommensurate with the angle of bank used, and inertia and hori-zontal component of lift (HCL) are equal.

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2. Using excessive power combined with alevel attitude, which causes a vertical climb.

3. Too abrupt application of the collective whendeparting the surface, causing r.p.m. andheading control errors.

CROSSWIND CONSIDERATIONS DURING TAKEOFFSIf the takeoff is made during crosswind conditions,the helicopter is flown in a slip during the earlystages of the maneuver. [Figure 9-9] The cyclic isheld into the wind a sufficient amount to maintainthe desired ground track for the takeoff. The head-ing is maintained with the use of the antitorquepedals. In other words, the rotor is tilted into thewind so that the sideward movement of the heli-copter is just enough to counteract the crosswindeffect. To prevent the nose from turning in thedirection of the rotor tilt, it is necessary toincrease the antitorque pedal pressure on theside opposite the rotor tilt.

After approximately 50 feet of altitude is gained,make a coordinated turn into the wind to maintainthe desired ground track. This is called crabbinginto the wind. The stronger the crosswind, themore you have to turn the helicopter into the windto maintain the desired ground track. [Figure 9-10]

STRAIGHT-AND-LEVEL FLIGHTStraight-and-level flight is flight in which a constantaltitude and heading are maintained. The attitudeof the helicopter determines the airspeed and is

controlled by the cyclic. Altitude is primarily con-trolled by use of the collective.

TECHNIQUETo maintain forward flight, the rotor tip-path planemust be tilted forward to obtain the necessary hor-izontal thrust component from the main rotor. Thisgenerally results in a nose-low attitude. The lowerthe nose, the greater the power required to main-tain altitude, and the higher the resulting airspeed.Conversely, the greater the power used, the lowerthe nose must be to maintain altitude. [Figure 9-11]

When in straight-and-level flight, any increase inthe collective, while holding airspeed constant,causes the helicopter to climb. A decrease in thecollective, while holding airspeed constant,causes the helicopter to descend. A change in thecollective requires a coordinated change of thethrottle to maintain a constant r.p.m. Additionally,the antitorque pedals need to be adjusted to main-tain heading and to keep the helicopter in longitu-dinal trim.

To increase airspeed in straight-and-level flight,apply forward pressure on the cyclic and raise thecollective as necessary to maintain altitude. Todecrease airspeed, apply rearward pressure onthe cyclic and lower the collective, as necessary,to maintain altitude.

Although the cyclic is sensitive, there is a slightdelay in control reaction, and it will be necessaryto anticipate actual movement of the helicopter.When making cyclic inputs to control the altitudeor airspeed of a helicopter, take care not to over-control. If the nose of the helicopter rises abovethe level-flight attitude, apply forward pressure tothe cyclic to bring the nose down. If this correctionis held too long, the nose drops too low. Since thehelicopter continues to change attitude momen-tarily after the controls reach neutral, return thecyclic to neutral slightly before the desired attitude

Figure 9-13. During a slip, the rate of turn is too slow for the angleof bank used, and the horizontal component of lift (HCL) exceedsinertia.

Figure 9-14. During a skid, the rate of turn is too fast for the angleof bank used, and inertia exceeds the horizontal component of lift(HCL).

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is reached. This principal holds true for any cyclicinput.

Since helicopters are inherently unstable, if a gustor turbulence causes the nose to drop, the nosetends to continue to drop instead of returning to astraight-and-level attitude as would a fixed-wingaircraft. Therefore, you must remain alert andFLY the helicopter at all times.

COMMON ERRORS1. Failure to properly trim the helicopter, tending

to hold antitorque pedal pressure and oppo-site cyclic. This is commonly called cross-controlling.

2. Failure to maintain desired airspeed.

3. Failure to hold proper control position tomaintain desired ground track.

TURNSA turn is a maneuver used to change the headingof the helicopter. The aerodynamics of a turn werepreviously discussed in Chapter 3—Aerodynamics of Flight.

TECHNIQUEBefore beginning any turn, the area in the direc-tion of the turn must be cleared not only at the heli-copter’s altitude, but also above and below. Toenter a turn from straight-and-level flight, applysideward pressure on the cyclic in the directionthe turn is to be made. This is the only controlmovement needed to start the turn. Do not use thepedals to assist the turn. Use the pedals only tocompensate for torque to keep the helicopter inlongitudinal trim. [Figure 9-12]

How fast the helicopter banks depends on howmuch lateral cyclic pressure you apply. How farthe helicopter banks (the steepness of the bank)depends on how long you displace the cyclic. Afterestablishing the proper bank angle, return thecyclic toward the neutral position. Increase thecollective and throttle to maintain altitude andr.p.m. As the torque increases, increase theproper antitorque pedal pressure to maintain lon-gitudinal trim. Depending on the degree of bank,additional forward cyclic pressure may berequired to maintain airspeed.

Rolling out of the turn to straight-and-level flight isthe same as the entry into the turn except thatpressure on the cyclic is applied in the oppositedirection. Since the helicopter continues to turn as

long as there is any bank, start the rollout beforereaching the desired heading.

The discussion on level turns is equally applica-ble to making turns while climbing or descend-ing. The only difference being that the helicopteris in a climbing or descending attitude rather thanthat of level flight. If a simultaneous entry isdesired, merely combine the techniques of bothmaneuvers—climb or descent entry and turnentry. When recovering from a climbing ordescending turn, the desired heading and altitudeare rarely reached at the same time. If the head-ing is reached first, stop the turn and maintainthe climb or descent until reaching the desiredaltitude. On the other hand, if the altitude isreached first, establish the level flight attitudeand continue the turn to the desired heading.

SLIPSA slip occurs when the helicopter slides sidewaystoward the center of the turn. [Figure 9-13] It iscaused by an insufficient amount of antitorquepedal in the direction of the turn, or too much in thedirection opposite the turn, in relation to theamount of power used. In other words, if you holdimproper antitorque pedal pressure, which keepsthe nose from following the turn, the helicopterslips sideways toward the center of the turn.

SKIDSA skid occurs when the helicopter slides sidewaysaway from the center of the turn. [Figure 9-14] Itis caused by too much antitorque pedal pressurein the direction of the turn, or by too little in thedirection opposite the turn in relation to theamount of power used. If the helicopter is forcedto turn faster with increased pedal pressureinstead of by increasing the degree of the bank, itskids sideways away from the center of the turninstead of flying in its normal curved pattern.

In summary, a skid occurs when the rate of turn istoo fast for the amount of bank being used, and aslip occurs when the rate of turn is too slow for theamount of bank being used.

COMMON ERRORS1. Using antitorque pedal pressures for turns.

This is usually not necessary for small heli-copters.

2. Slipping or skidding in the turn.

NORMAL CLIMBThe entry into a climb from a hover has alreadybeen discussed under “Normal Takeoff from a

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Hover;” therefore, this discussion is limited to aclimb entry from cruising flight.

TECHNIQUETo enter a climb from cruising flight, apply aft cyclicto obtain the approximate climb attitude.Simultaneously increase the collective and throttleto obtain climb power and maintain r.p.m. In acounterclockwise rotor system, increase the leftantitorque pedal pressure to compensate for theincreased torque. As the airspeed approaches nor-mal climb airspeed, adjust the cyclic to hold thisairspeed. Throughout the maneuver, maintainclimb attitude, heading, and airspeed with thecyclic; climb power and r.p.m. with the collectiveand throttle; and longitudinal trim with the anti-torque pedals.

To level off from a climb, start adjusting the attitude tothe level flight attitude a few feet prior to reaching thedesired altitude. The amount of lead depends on therate of climb at the time of level-off (the higher therate of climb, the more the lead). Generally, the leadis 10 percent of the climb rate. For example, if yourclimb rate is 500 feet per minute, you should lead thelevel-off by 50 feet.

To begin the level-off, apply forward cyclic toadjust and maintain a level flight attitude, which isslightly nose low. You should maintain climb poweruntil the airspeed approaches the desired cruisingairspeed, then lower the collective to obtain cruis-ing power and adjust the throttle to obtain andmaintain cruising r.p.m. Throughout the level-off,maintain longitudinal trim and heading with theantitorque pedals.

COMMON ERRORS1. Failure to maintain proper power and air-

speed.

2. Holding too much or too little antitorquepedal.

3. In the level-off, decreasing power before low-ering the nose to cruising attitude.

NORMAL DESCENTA normal descent is a maneuver in which the hel-icopter loses altitude at a controlled rate in a con-trolled attitude.

Figure 9-15. Rectangular course. The numbered positions in the text refer to the numbers in this illustration.

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TECHNIQUETo establish a normal descent from straight-and-level flight at cruising airspeed, lower the collec-tive to obtain proper power, adjust the throttle tomaintain r.p.m., and increase right antitorquepedal pressure to maintain heading in a counter-clockwise rotor system, or left pedal pressure in aclockwise system. If cruising airspeed is the same as, or slightly above descend-ing airspeed, simultaneously apply the necessaryc y c l i cpressure to obtain the approximate descending atti-tude. If cruising speed is well above descendingairspeed, you can maintain a level flight attitudeuntil the airspeed approaches the descending air-speed, then lower the nose to the descending atti-tude. Throughout the maneuver, maintaindescending attitude and airspeed with the cyclic;descending power and r.p.m. with the collectiveand throttle; and heading with the antitorque ped-als.

To level off from the descent, lead the desired alti-tude by approximately 10 percent of the rate ofdescent. For example, a 500 feet per minute rate ofdescent would require a 50 foot lead. At this point,increase the collective to obtain cruising power,adjust the throttle to maintain r.p.m., and increase leftantitorque pedal pressure to maintain heading (rightpedal pressure in a clockwise rotor system). Adjustthe cyclic to obtain cruising airspeed and a level flightattitude as the desired altitude is reached.

COMMON ERRORS1. Failure to maintain constant angle of decent

during training.

2. Failure to lead the level-off sufficiently, whichresults in recovery below the desired altitude.

3. Failure to adjust antitorque pedal pressuresfor changes in power.

GROUND REFERENCE MANEUVERSGround reference maneuvers are training exer-cises flown to help you develop a division of atten-tion between the flight path and groundreferences, while controlling the helicopter andwatching for other aircraft in the vicinity. Prior toeach maneuver, a clearing turn should be accom-plished to ensure the practice area is free of con-flicting traffic.

RECTANGULAR COURSEThe rectangular course is a training maneuver inwhich the ground track of the helicopter is equidis-tant from all sides of a selected rectangular areaon the ground. While performing the maneuver,

the altitude and airspeed should be held constant.The rectangular course helps you to develop arecognition of a drift toward or away from a lineparallel to the intended ground track. This is help-ful in recognizing drift toward or from an airportrunway during the various legs of the airport trafficpattern.

For this maneuver, pick a square or rectangularfield, or an area bounded on four sides by sec-tion lines or roads, where the sides are approxi-mately a mile in length. The area selectedshould be well away from other air traffic. Fly themaneuver approximately 600 to 1,000 feetabove the ground, which is the altitude usuallyrequired for an airport traffic pattern. You shouldfly the helicopter parallel to and at a uniform dis-tance, about one-fourth to one-half mile, fromthe field boundaries, not above the boundaries.For best results, position your flight path outsidethe field boundaries just far enough away thatthey may be easily observed from either pilotseat by looking out the side of the helicopter. Ifan attempt is made to fly directly above theedges of the field, you will have no usable refer-ence points to start and complete the turns. Inaddition, the closer the track of the helicopter isto the field boundaries, the steeper the banknecessary at the turning points. Also, you shouldbe able to see the edges of the selected fieldwhile seated in a normal position and looking outthe side of the helicopter during either a left-hand or right-hand course. The distance of theground track from the edges of the field shouldbe the same regardless of whether the course isflown to the left or right. All turns should bestarted when your helicopter is abeam the cor-ners of the field boundaries. The bank normallyshould not exceed 30°.

Although the rectangular course may be enteredfrom any direction, this discussion assumes entry

Figure 9-16. S-turns across a road.

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on a downwind heading. [Figure 9-15] As you approachthe field boundary on the downwind leg, youshould begin planning for your turn to the cross-wind leg. Since you have a tailwind on the down-wind leg, the helicopter's groundspeed isincreased (position 1). During the turn onto thecrosswind leg, which is the equivalent of the baseleg in a traffic pattern, the wind causes the heli-copter to drift away from the field. To counteractthis effect, the roll-in should be made at a fairlyfast rate with a relatively steep bank (position 2).

As the turn progresses, the tailwind componentdecreases, which decreases the groundspeed.Consequently, the bank angle and rate of turnmust be reduced gradually to ensure that uponcompletion of the turn, the crosswind ground trackcontinues to be the same distance from the edgeof the field. Upon completion of the turn, the heli-copter should be level and aligned with the down-wind corner of the field. However, since thecrosswind is now pushing you away from the field,you must establish the proper drift correction byflying slightly into the wind. Therefore, the turn tocrosswind should be greater than a 90° change inheading (position 3). If the turn has been made

properly, the field boundary again appears to beone-fourth to one-half mile away. While on thecrosswind leg, the wind correction should beadjusted, as necessary, to maintain a uniform dis-tance from the field boundary (position 4).

As the next field boundary is being approached(position 5), plan the turn onto the upwind leg.Since a wind correction angle is being held intothe wind and toward the field while on the cross-wind leg, this next turn requires a turn of less than90°. Since the crosswind becomes a headwind,causing the groundspeed to decrease during thisturn, the bank initially must be medium and pro-gressively decreased as the turn proceeds. Tocomplete the turn, time the rollout so that the heli-copter becomes level at a point aligned with thecorner of the field just as the longitudinal axis ofthe helicopter again becomes parallel to the fieldboundary (position 6). The distance from the fieldboundary should be the same as on the othersides of the field.

On the upwind leg, the wind is a headwind, whichresults in an decreased groundspeed (position 7).Consequently, enter the turn onto the next leg witha fairly slow rate of roll-in, and a relatively shallowbank (position 8). As the turn progresses, gradu-ally increase the bank angle because the head-wind component is diminishing, resulting in anincreasing groundspeed. During and after the turnonto this leg, the wind tends to drift the helicoptertoward the field boundary. To compensate for thedrift, the amount of turn must be less than 90°(position 9).

Again, the rollout from this turn must be such thatas the helicopter becomes level, the nose of thehelicopter is turned slightly away the field and intothe wind to correct for drift. The helicopter shouldagain be the same distance from the field bound-ary and at the same altitude, as on other legs.Continue the crosswind leg until the downwind legboundary is approached (position 10). Once moreyou should anticipate drift and turning radius.Since drift correction was held on the crosswindleg, it is necessary to turn greater than 90° to alignthe helicopter parallel to the downwind leg bound-ary. Start this turn with a medium bank angle,gradually increasing it to a steeper bank as theturn progresses. Time the rollout to assure paral-leling the boundary of the field as the helicopterbecomes level (position 11).

If you have a direct headwind or tailwind on theupwind and downwind leg, drift should not beencountered. However, it may be difficult to find asituation where the wind is blowing exactly paral-lel to the field boundaries. This makes it neces-sary to use a slight wind correction angle on allthe legs. It is important to anticipate the turns tocompensate for groundspeed, drift, and turningradius. When the wind is behind the helicopter, theturn is faster and steeper; when it is ahead of the

Figure 9-17. Turns around a point.

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helicopter, the turn is slower and shallower. These same techniques apply while fly-ing in an airport traffic pattern.

S-TURNSAnother training maneuver you might use is the S-turn, which helps you correct for wind drift in turns.This maneuver requires turns to the left and right.The reference line used, whether a road, railroad,or fence, should be straight for a considerable dis-tance and should extend as nearly perpendicularto the wind as possible.

The object of S-turns is to fly a pattern of two halfcircles of equal size on opposite sides of the refer-ence line. [Figure 9-16] The maneuver should beperformed at a constant altitude between 600 and1,000 feet above the terrain. S-turns may bestarted at any point; however, during early trainingit may be beneficial to start on a downwind head-ing. Entering downwind permits the immediateselection of the steepest bank that is desiredthroughout the maneuver. The discussion that fol-lows is based on choosing a reference line that isperpendicular to the wind and starting the maneu-ver on a downwind heading.

As the helicopter crosses the reference line,immediately establish a bank. This initial bank isthe steepest used throughout the maneuver sincethe helicopter is headed directly downwind andthe groundspeed is at its highest. Graduallyreduce the bank, as necessary, to describe aground track of a half circle. Time the turn so thatas the rollout is completed, the helicopter is cross-ing the reference line perpendicular to it and head-ing directly upwind. Immediately enter a bank inthe opposite direction to begin the second half ofthe “S.” Since the helicopter is now on an upwindheading, this bank (and the one just completedbefore crossing the reference line) is the shallow-est in the maneuver. Gradually increase the bank,as necessary, to describe a ground track that is ahalf circle identical in size to the one previouslycompleted on the other side of the reference line.The steepest bank in this turn should be attainedjust prior to rollout when the helicopter isapproaching the reference line nearest the down-wind heading. Time the turn so that as the rolloutis complete, the helicopter is perpendicular to thereference line and is again heading directly down-wind.

In summary, the angle of bank required at anygiven point in the maneuver is dependent on thegroundspeed. The faster the groundspeed, thesteeper the bank; the slower the groundspeed, thes h a l l o w e r

the bank. To express it another way, the morenearly the helicopter is to a downwind heading,the steeper the bank; the more nearly it is to anupwind heading, the shallower the bank. In addition to varying theangle of bank to correct for drift in order to main-tain the proper radius of turn, the helicopter mustalso be flown with a drift correction angle (crab) inrelation to its ground track; except of course, whenit is on direct upwind or downwind headings or thereis no wind. One would normally think of the fore andaft axis of the helicopter as being tangent to theground track pattern at each point. However, this isnot the case. During the turn on the upwind side ofthe reference line (side from which the wind isblowing), crab the nose of the helicopter towardthe outside of the circle. During the turn on thedownwind side of the reference line (side of thereference line opposite to the direction from whichthe wind is blowing), crab the nose of the helicop-ter toward the inside of the circle. In either case, itis obvious that the helicopter is being crabbed intothe wind just as it is when trying to maintain astraight ground track. The amount of crabdepends upon the wind velocity and how nearlythe helicopter is to a crosswind position. Thestronger the wind, the greater the crab angle atany given position for a turn of a given radius. Themore nearly the helicopter is to a crosswind posi-tion, the greater the crab angle. The maximumcrab angle should be at the point of each half cir-cle farthest from the reference line.

A standard radius for S-turns cannot be specified,since the radius depends on the airspeed of thehelicopter, the velocity of the wind, and the initialbank chosen for entry.

Figure 9-18. A standard traffic pattern has turns to left and fivedesignated legs.

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TURNS AROUND A POINTThis training maneuver requires you to fly con-stant radius turns around a preselected point onthe ground using a bank of approximately 30°,while maintaining a constant altitude. [Figure 9-17] Your objective, as in other ground referencemaneuvers, is to develop the ability to subcon-sciously control the helicopter while dividing atten-tion between the flight path and groundreferences, while still watching for other air trafficin the vicinity.

The factors and principles of drift correction thatare involved in S-turns are also applicable in thismaneuver. As in other ground track maneuvers,a constant radius around a point will, if any windexists, require a constantly changing angle ofbank and angles of wind correction. The closerthe helicopter is to a direct downwind headingwhere the groundspeed is greatest, the steeperthe bank, and the faster the rate of turn requiredto establish the proper wind correction angle.The more nearly it is to a direct upwind headingwhere the groundspeed is least, the shallowerthe bank, and the slower the rate of turn requiredto establish the proper wind correction angle. Itfollows, then, that throughout the maneuver, thebank and rate of turn must be gradually varied inproportion to the groundspeed.

The point selected for turns around a point shouldbe prominent and easily distinguishable, yet smallenough to present a precise reference. Isolatedtrees, crossroads, or other similar small landmarksare usually suitable. The point should be in an areaaway from communities, livestock, or groups ofpeople on the ground to prevent possible annoy-ance or hazard to others. Since the maneuver isperformed between 600 and 1,000 feet AGL, thearea selected should also afford an opportunity fora safe emergency autorotation in the event itbecomes necessary.

To enter turns around a point, fly the helicopteron a downwind heading to one side of theselected point at a distance equal to the desiredradius of turn. When any significant wind exists,it is necessary to roll into the initial bank at arapid rate so that the steepest bank is attainedabeam the point when the helicopter is headeddirectly downwind. By entering the maneuverwhile heading directly downwind, the steepestbank can be attained immediately. Thus, if abank of 30° is desired, the initial bank is 30° ifthe helicopter is at the correct distance from thepoint. Thereafter, the bank is gradually shal -lowed until the point is reached where the heli-copter is headed directly upwind. At this point,

est bank is again attained when heading down-wind at the initial point of entry.

Just as S-turns require that the helicopter beturned into the wind in addition to varying thebank, so do turns around a point. During thedownwind half of the circle, the helicopter’s nosemust be progressively turned toward the insideof the circle; during the upwind half, the nosemust be progressively turned toward the outside.The downwind half of the turn around the pointmay be compared to the downwind side of the S-turn, while the upwind half of the turn around apoint may be compared to the upwind side of theS-turn.

As you become experienced in performing turnsaround a point and have a good understandingof the effects of wind drift and varying of thebank angle and wind correction angle asrequired, entry into the maneuver may be fromany point. When entering this maneuver at anypoint, the radius of the turn must be carefullyselected, taking into account the wind velocity

Figure 9-19. Plan the turn to final so the helicopter rolls out onan imaginary extension of the centerline for the final approachpath. This path should neither angle to the landing area, asshown by the helicopter on the left, nor require an S-turn, asshown by the helicopter on the right.

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and groundspeed so that an excessive bank isnot required later on to maintain the properground track.

COMMON ERRORS DURING GROUNDREFERENCE MANEUVERS1. Faulty entry technique.

2. Poor planning, orientation, or division of attention.

3. Uncoordinated flight control application.

4. Improper correction for wind drift.

5. An unsymmetrical ground track during S-Turns Across a Road.

6. Failure to maintain selected altitude or air-speed.

7. Selection of a ground reference where thereis no suitable emergency landing area withingliding distance.

TRAFFIC PATTERNSA traffic pattern is useful to control the flow of traffic,particularly at airports without operating control tow-ers. It affords a measure of safety, separation, pro-tection, and administrative control over arriving,departing, and circling aircraft. Due to specializedoperating characteristics, airplanes and helicoptersdo not mix well in the same traffic environment. Atmultiple-use airports, you routinely must avoidthe flow of fixed-wing traffic. To do this, youneed to be familiar with the patterns typically flown by airplanes. In addition,you should learn how to fly these patterns incase air traffic control (ATC) requests that youfly a fixed-wing traffic pattern.

A normal traffic pattern is rectangular, has fivenamed legs, and a designated altitude, usually600 to 1,000 feet AGL. A pattern in which all turnsare to the left is called a standard pattern. [Figure9-18] The takeoff leg (item 1) normally consists ofthe aircraft’s flight path after takeoff. This leg isalso called the upwind leg. You should turn to thecrosswind leg (item 2), after passing the departureend of the runway when you are at a safe altitude.

Fly the downwind leg (item 3) parallel to the run-way at the designated traffic pattern altitude anddistance from the runway. Begin the base leg(item 4) at a point selected according to other traf-fic and wind conditions. If the wind is very strong,begin the turn sooner than normal. If the wind islight, delay the turn to base. The final approach(item 5) is the path the aircraft flies immediatelyprior to touchdown.

You may find variations at different localities andat airports with operating control towers. Forexample, a right-hand pattern may be designatedto expedite the flow of traffic when obstacles orhighly populated areas make the use of a left-hand pattern undesirable.

When approaching an airport with an operatingcontrol tower in a helicopter, it is possible to expe-dite traffic by stating your intentions, for example:

1. (Call sign of helicopter) Robinson 8340J.

2. (Position) 10 miles west.

3. (Request) for landing and hover to...

In order to avoid the flow of fixed-wing traffic,the tower will often clear you direct to anapproach point or to a particular runway inter-section nearest your destination point. Atuncontrolled airports, if at all possible, youshould adhere to standard practices and pat-terns.

Traffic pattern entry procedures at airports with anoperating control tower are specified by the con-troller. At uncontrolled airports, traffic pattern alti-tudes and entry procedures may vary according toestablished local procedures. The general proce-dure is for you to enter the pattern at a 45° angleto the downwind leg abeam the midpoint of therunway. For information concerning traffic patternand landing direction, you should utilize airportadvisory service or UNICOM, when available.

The standard departure procedure when using thefixed-wing traffic pattern is usually straight-out,downwind, or a right-hand departure. When a con-trol tower is in operation, you can request the typeof departure you desire. In most cases, helicopterdepartures are made into the wind unless obsta-cles or traffic dictate otherwise. At airports withoutan operating control tower, you must comply withthe departure procedures established for that air-port.

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The maneuvers presented in this chapter requiremore finesse and understanding of the helicopterand the surrounding environment. When performing thesemaneuvers, you will probably be taking your heli-copter to the edge of the safe operating envelope.Therefore, if you are ever in doubt about the out-come of the maneuver, you should abort the mis-sion entirely or wait for more favorable conditions.

RECONNAISSANCE PROCEDURESAnytime you are planning to land or takeoff at anunfamiliar site, you should gather as much infor-mation as you can about the area.Reconnaissance techniques are ways of gather-ing this information.

HIGH RECONNAISSANCEThe purpose of a high reconnaissance is to deter-mine the wind direction and speed, a point fortouchdown, the suitability of the landing area, theapproach and departure axes, obstacles and theireffect on wind patterns, and the most suitableflight paths into and out of the area. When con-ducting a high reconnaissance, give particularconsideration to forced landing areas in case ofan emergency.

Altitude, airspeed, and flight pattern for a highreconnaissance are governed by wind and terrainfeatures. You must strike a balance between areconnaissance conducted too high and one toolow. It should not be flown so low that you have todivide your attention between studying the areaand avoiding obstructions to flight. A high recon-naissance should be flown at an altitude of 300 to500 feet above the surface. A general rule to fol-low is to ensure that sufficient altitude is availableat all times to land into the wind in case of enginefailure. In addition, a 45° angle of observation gen-erally allows the best estimate of the height of bar-riers, the presence of obstacles, the size of thearea, and the slope of the terrain. Always maintainsafe altitudes and airspeeds, and keep a forcedlanding area within reach whenever possible.

LOW RECONNAISSANCEA low reconnaissance is accomplished during theapproach to the landing area. When flying theapproach, verify what was observed in the highreconnaissance, and check for anything new thatmay have been missed at a higher altitude, suchas wires, slopes, and small crevices. If everythingis alright, you can complete the approach to alanding. However, you must make the decision toland or go-around before effective translational liftis lost.

If a decision is made to complete the approach,terminate it in a hover, so you can carefully checkt h elanding point before lowering the helicopter to the surface. Under certain conditions, it may be desir-able to continue the approach to the surface.Once the helicopter is on the ground, maintainoperating r.p.m. until you have checked the stabil-ity of the helicopter to be sure it is in a secure andsafe position.

GROUND RECONNAISSANCEPrior to departing an unfamiliar location, make adetailed analysis of the area. There are severalfactors to consider during this evaluation. Besidesdetermining the best departure path, you mustselect a route that will get your helicopter from itspresent position to the takeoff point.

Some things to consider while formulating a take-off plan are the aircraft load, height of obstacles,the shape of the area, and direction of the wind. Ifthe helicopter is heavily loaded, you must deter-mine if there is sufficient power to clear the obsta-cles. Sometimes it is better to pick a path overshorter obstacles than to take off directly into thewind. You should also evaluate the shape of thearea so that you can pick a path that will give youthe most room to maneuver and abort the takeoff ifnecessary. Wind analysis also helps determine theroute of takeoff. The prevailing wind can be alteredby obstructions on the departure path, and can sig-nificantly affect aircraft performance. One way todetermine the wind direction is to drop some dustor grass, and observe which way it is blowing.Keep in mind that if the main rotor is turning, youwill need to be a sufficient distance from the heli-

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copter to ensure that the downwash of the bladesdoes not give you a false indication.

If possible, you should walk the route from the hel-icopter to the takeoff position. Evaluate obstaclesthat could be hazardous and ensure that you willhave adequate rotor clearance. Once at the down-wind end of the available area, mark a position fortakeoff so that the tail and main rotors have suffi-cient clearance from any obstructions behind thehelicopter. Use a sturdy marker, such as a heavystone or log, so it does not blow away.

MAXIMUM PERFORMANCE TAKEOFFA maximum performance takeoff is used to climbat a steep angle to clear barriers in the flight path.It can be used when taking off from small areassurrounded by high obstacles. Before attemptinga maximum performance takeoff, you must know thoroughlythe capabilities and limitations of your equipment.You must also consider the wind velocity, temper-ature, altitude, gross weight, center-of-gravitylocation, and other factors affecting your tech-nique and the performance of the helicopter.

To safely accomplish this type of takeoff, theremust be enough power to hover, in order to pre-vent the helicopter from sinking back to the surfaceafter becoming airborne. This hover power check can be used todetermine if there is sufficient power available toaccomplish this maneuver.

The angle of climb for a maximum performancetakeoff depends on existing conditions. The morecritical the conditions, such as high density alti-tudes, calm winds, and high gross weights, theshallower the angle of climb. In light or no windconditions, it might be necessary to operate in thecrosshatched or shaded areas of the height/veloc-ity diagram during the beginning of this maneuver.Therefore, be aware of the

calculated risk when operating in these areas. Anengine failure at a low altitude and airspeed couldplace the helicopter in a dangerous position,requiring a high degree of skill in making a safeautorotative landing.

TECHNIQUEBefore attempting a maximum performance take-off, bring the helicopter to a hover, and determinethe excess power available by noting the differ-ence between the power available and thatrequired to hover. You should also perform a bal-ance and flight control check and note the positionof the cyclic. Then position the helicopter into thewind and return the helicopter to the surface.Normally, this maneuver is initiated from the sur-face. After checking the area for obstacles andother aircraft, select reference points along thetakeoff path to maintain ground track. You shouldalso consider alternate routes in case you are notable to complete the maneuver. [Figure 10-1]

Begin the takeoff by getting the helicopter light on theskids (position 1). Pause and neutralize all aircraftmovement. Slowly increase the collective and posi-tion the cyclic so as to break ground in a 40 knot atti-tude. This is approximately the same attitude aswhen the helicopter is light on the skids. Continue toslowly increase the collective until the maximumpower available is reached. This large collectivemovement requires a substantial increase in pedalpressure to maintain heading (position 2). Use thecyclic, as necessary, to control movement toward thedesired flight path and, therefore, climb angle duringthe maneuver (position 3). Maintain rotor r.p.m. at itsmaximum, and do not allow it to decrease since youwould probably have to lower the collective to regainit. Maintain these inputs until the helicopter clears theobstacle, or until reaching 50 feet for demonstrationpurposes (position 4). Then, establish a normal climbattitude and reduce power (position 5). As in anymaximum performance maneuver, the techniquesyou use affect the actual results. Smooth, coordi-nated inputs coupled with precise control allow thehelicopter to attain its maximum performance.

COMMON ERRORS1. Failure to consider performance data, includ-

ing height/velocity diagram.

2. Nose too low initially, causing horizontal flightrather than more vertical flight.

3. Failure to maintain maximum permissibler.p.m.

4. Abrupt control movements.

5. Failure to resume normal climb power andairspeed after clearing the obstacle.

RUNNING/ROLLING TAKEOFFFigure 10-1. Maximum performance takeoff.

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times used when conditions of load and/or densityaltitude prevent a sustained hover at normal hov-ering altitude. However, you should not attemptthis maneuver if you do not have sufficient powerto hover, at least momentarily. If the helicoptercannot be hovered, its performance is unpre-dictable. If the helicopter cannot be raised off the surface at all, sufficient power might not be avail-able to safely accomplish the maneuver. If youcannot momentarily hover the helicopter, youmust wait for conditions to improve or off-loadsome of the weight.

To accomplish a safe running or rolling takeoff, thesurface area must be of sufficient length andsmoothness, and there cannot be any barriers inthe flight path to interfere with a shallow climb.

For wheeled helicopters, a rolling takeoff is some-times used to minimize the downwash createdduring a takeoff from a hover.

TECHNIQUERefer to figure 10-2. To begin the maneuver, firstalign the helicopter to the takeoff path. Next,increase the throttle to obtain takeoff r.p.m., andincrease the collective smoothly until the helicop-ter becomes light on the skids or landing gear(position 1). Then, move the cyclic slightly forward

of the neutral hovering position, and apply addi-tional collective to start the forward movement(position 2). To simulate a reduced power condi-tion during practice, use one to two inches lessmanifold pressure, or three to five percent lesstorque, than that required to hover.

Maintain a straight ground track with lateral cyclicand heading with antitorque pedals until a climb isestablished. As effective translational lift is gained,the helicopter becomes airborne in a fairly level atti-tude with little or no pitching (position 3). Maintain analtitude to take advantage of ground effect, and allowthe airspeed to increase toward normal climb speed.Then, follow a climb profile that takes you throughthe clear area of the height/velocity diagram (posi-tion 4). During practice maneuvers, after you haveclimbed to an altitude of 50 feet, establish the normalclimb power setting and attitude.

COMMON ERRORS

1. Failing to align heading and ground track tokeep surface friction to a minimum.

2. Attempting to become airborne beforeobtaining effective translational lift.

3. Using too much forward cyclic during the sur-face run.

4. Lowering the nose too much after becomingairborne, resulting in the helicopter settlingback to the surface.

5. Failing to remain below the recommendedaltitude until airspeed approaches normalclimb speed.

RAPID DECELERATION (QUICK STOP)In normal operations, use the rapid deceleration orquick stop maneuver to slow the helicopter rapidlyand bring it to a stationary hover. The maneuverrequires a high degree of coordination of all con-

Figure 10-2. Running/rolling takeoff.

Figure 10-3. Rapid deceleration or quick stop.

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trols. It is practiced at an altitude that permits asafe clearance between the tail rotor and the sur-face throughout the maneuver, especially at thepoint where the pitch attitude is highest. The alti-tude at completion should be no higher than themaximum safe hovering altitude prescribed by themanufacturer. In selecting an altitude at which tobegin the maneuver, you should take into accountthe overall length of the helicopter and theheight/velocity diagram. Even though the maneu-ver is called a rapid deceleration or quick stop, it isperformed slowly and smoothly with the primaryemphasis on coordination.

TECHNIQUEDuring training always perform this maneuver intothe wind. [Figure 10-3, position 1] After leveling offat an altitude between 25 and 40 feet, dependingon the manufacturer’s recommendations, acceler-ate to the desired entry speed, which is approxi-mately 45 knots for most training helicopters(position 2). The altitude you choose should behigh enough to avoid danger to the tail rotor dur-ing the flare, but low enough to stay out of thecrosshatched or shaded areas of the height/veloc-ity diagram throughout the maneuver. In addition,t h i saltitude should be low enough that you can bringthe helicopter to a hover during the recovery.

At position 3, initiate the deceleration by applyingaft cyclic to reduce forward speed.Simultaneously, lower the collective, as neces-sary, to counteract any climbing tendency. Thetiming must be exact. If you apply too little downcollective for the amount of aft cyclic applied, aclimb results. If you apply too much down collec-tive, a descent results. A rapid application of aftcyclic requires an equally rapid application ofdown collective. As collective pitch is lowered,apply proper antitorque pedal pressure to main-tain heading, and adjust the throttle to maintainr.p.m.

After attaining the desired speed (position 4), initi-ate the recovery by lowering the nose and allow-ing the helicopter to descend to a normal hoveringaltitude in level flight and zero groundspeed (posi-tion 5). During the recovery, increase collectivepitch, as necessary, to stop the helicopter at nor-

mal hovering altitude, adjust the throttle to main-tain r.p.m., and apply proper pedal pressure, asnecessary, to maintain heading.

COMMON ERRORS1. Initiating the maneuver by applying down

collective.

2. Initially applying aft cyclic stick too rapidly,causing the helicopter to balloon.

3. Failing to effectively control the rate of decel-eration to accomplish the desired results.

4. Allowing the helicopter to stop forwardmotion in a tail-low attitude.

5. Failing to maintain proper r.p.m.

6. Waiting too long to apply collective pitch(power) during the recovery, resulting inexcessive manifold pressure or an over-torque situation when collective pitch isapplied rapidly.

7. Failing to maintain a safe clearance over the terrain.

8. Improper use of antitorque pedals resultingin erratic heading changes.

STEEP APPROACH TO A HOVERA steep approach is used primarily when there areobstacles in the approach path that are too high toallow a normal approach. A steep approach per -mits entry into most confined areas and is some-times used to avoid areas of turbulence around apinnacle. An approach angle of approximately 15°is considered a steep approach. [Figure 10-4]

Figure 10-4. Steep approach to a hover.

Balloon—Gaining an excessive amount of altitude as a result of anabrupt flare.

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TECHNIQUEOn final approach, head your helicopter into thewind and align it with the intended touchdownpoint at the recommended approach airspeed(position 1). When you intercept an approachangle of 15°, begin the approach by lowering thecollective sufficiently to start the helicopterdescending down the approach path and decel-erating (position 2). Use the proper antitorquepedal for trim. Since this angle is steeper than anormal approach angle, you need to reduce thecollective more than that required for a normalapproach. Continue to decelerate with slight aftcyclic, and smoothly lower the collective to main-tain the approach angle. As in a normala p p r o a c h ,reference the touchdown point on the windshieldto determine changes in approach angle. Thispoint is in a lower position than a normalapproach. Aft cyclic is required to deceleratesooner than a normal approach, and the rate ofclosure becomes apparent at a higher altitude.Maintain the approach angle and rate of descentwith the collective, rate of closure with the cyclic,and trim with antitorque pedals. Use a crababove 50 feet and a slip below 50 feet for anycrosswind that might be present.

Loss of effective translational lift occurs higher ina steep approach (position 3), requiring anincrease in the collective to prevent settling, andmore forward cyclic to achieve the proper rate ofclosure. Terminate the approach at hovering alti-tude above the intended landing point with zerogroundspeed (position 4). If power has been prop-erly applied during the final portion of theapproach, very little additional power is required inthe hover.

COMMON ERRORS

1. Failing to maintain proper r.p.m. during theentire approach.

2. Improper use of collective in maintaining theselected angle of descent.

3. Failing to make antitorque pedal correctionsto compensate for collective pitch changesduring the approach.

4. Slowing airspeed excessively in order toremain on the proper angle of descent.

5. Inability to determine when effective transla-tional lift is lost.

6. Failing to arrive at hovering altitude and atti-tude, and zero groundspeed almost simulta-neously.

7. Low r.p.m. in transition to the hover at theend of the approach.

8. Using too much aft cyclic close to the sur-face, which may result in the tail rotor strikingthe surface.

SHALLOW APPROACH ANDRUNNING/ROLL-ON LANDINGUse a shallow approach and running landingwhen a high-density altitude or a high grossweight condition, or some combination thereof, issuch that a normal or steep approach cannot bemade because of insufficient power to hover.[Figure 10-5] To compensate for this lack of power,a shallow approach and running landing makesuse of translational lift until surface contact ismade. If flying a wheeled helicopter, you can alsouse a roll-on landing to minimize the effect ofdownwash. The glide angle for a shallowapproach is approximately 5°. Since the helicop-ter will be sliding or rolling to a stop during thismaneuver, the landing area must be smooth andlong enough to accomplish this task.

TECHNIQUEA shallow approach is initiated in the same manneras the normal approach except that a shallowerangle of descent is maintained. The power reduc-tion to initiate the desired angle of descent is lessthan that for a normal approach since the angle ofdescent is less (position 1).

As you lower the collective, maintain heading withproper antitorque pedal pressure, and r.p.m. with

Figure 10-5. Shallow approach and running landing.

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the throttle. Maintain approach airspeed until theapparent rate of closure appears to be increasing.Then, begin to slow the helicopter with aft cyclic(position 2).

As in normal and steep approaches, the primarycontrol for the angle and rate of descent is the col-lective, while the cyclic primarily controls thegroundspeed. However, there must be a coordi-nation of all the controls for the maneuver to beaccomplished successfully. The helicopter shouldarrive at the point of touchdown at or slightlyabove effective translational lift. Since transla-tional lift diminishes rapidly at slow airspeeds, thedeceleration must be smoothly coordinated, at thesame time keeping enough lift to prevent the heli-copter from settling abruptly.

Just prior to touchdown, place the helicopter in alevel attitude with the cyclic, and maintain headingwith the antitorque pedals. Use the cyclic to keepthe heading and ground track identical (position3). Allow the helicopter to descend gently to the surface in astraight-and-level attitude, cushioning the landingwith the collective. After surface contact, move the cyclicslightly forward to ensure clearance between the tailboom and the rotor disc. You should also usethe cyclic to maintain the surface track. (position4). You normally hold the collective stationary untilthe helicopter stops; however, if you want morebraking action, you can lower the collective slightly.Keep in mind that due to the increased ground fric-tion when you lower the collective, the helicopter’snose might pitch forward. Exercise caution not tocorrect this pitching movement with aft cyclic sincethis movement could result in the rotor makingcontact with the tailboom. During the landing,maintain normal r.p.m. with the throttle and direc-tional control with the antitorque pedals.

For wheeled helicopters, use the same techniqueexcept after landing, lower the collective, neutral-ize the controls, and apply the brakes, as necessary, toslow the helicopter. Do not use aft cyclic whenbringing the helicopter to a stop.

COMMON ERRORS1. Assuming excessive nose-high attitude to

slow the helicopter near the surface.

2. Insufficient collective and throttle to cushionlanding.

3. Failing to add proper antitorque pedal as col-lective is added to cushion landing, resultingin a touchdown while the helicopter is mov-ing sideward.

4. Failing to maintain a speed that takes advan-tage of effective translational lift.

5. Touching down at an excessive ground-speed for the existing conditions. (Some hel-icopters have maximum touchdowngroundspeeds.)

6. Failing to touch down in a level attitude.

7. Failing to maintain proper r.p.m. during andafter touchdown.

8. Poor directional control during touchdown.

SLOPE OPERATIONSPrior to conducting any slope operations, youshould be thoroughly familiar with the characteris-tics of dynamic rollover and mast bumping, whichare discussed in Chapter 11—HelicopterEmergencies. The approach to a slope is similarto the approach to any other landing area. Duringslope operations, make allowances for wind, bar-riers, and forced landing sites in case of enginefailure. Since the slope may constitute an obstruc-tion to wind passage, you should anticipate turbu-lence and downdrafts.

Figure 10-6. Slope landing.

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SLOPE LANDINGYou usually land a helicopter across the sloperather than with the slope. Landing with the heli-copter facing down the slope or downhill is notrecommended because of the possibility of strik-ing the tail rotor on the surface.

TECHNIQUERefer to figure 10-6. At the termination of theapproach, move the helicopter slowly toward theslope, being careful not to turn the tail upslope.Position the helicopter across the slope at a stabi-lized hover headed into the wind over the spot ofintended landing (frame 1). Downward pressure on the collectivestarts the helicopter descending. As the upslopeskid touches the ground, hesitate momentarily ina level attitude, then apply lateral cyclic in thedirection of the slope (frame 2). This holds the skidagainst the slope while you continue lowering thedownslope skid with the collective. As you lowerthe collective, continue to move the cyclic towardthe slope to maintain a fixed position (frame 3).The slope must be shallow enough so you canhold the helicopter against it with the cyclic duringthe entire landing. A slope of 5° is consideredmaximum for normal operation of most helicop-ters.

You should be aware of any abnormal vibration ormast bumping that signals maximum cyclic deflec-tion. If this occurs, abandon the landing becausethe slope is too steep. In most helicopters with acounterclockwise rotor system, landings can bemade on steeper slopes when you are holding thecyclic to the right. When landing on slopes usingleft cyclic, some cyclic input must be used to over-come the translating tendency. If wind is not a fac-tor, you should consider the drifting tendencywhen determining landing direction.

After the downslope skid is on the surface, reducethe collective to full down, and neutralize the cyclicand pedals (frame 4). Normal operating r.p.m.

should be maintained until the full weight of thehelicopter is on the landing gear. This ensuresadequate r.p.m. for immediate takeoff in case thehelicopter starts sliding down the slope. Use anti-torque pedals as necessary throughout the land-ing for heading control. Before reducing the r.p.m.,move the cyclic control as necessary to check thatthe helicopter is firmly on the ground.

COMMON ERRORS

1. Failure to consider wind effects during theapproach and landing.

2. Failure to maintain proper r.p.m. throughoutthe entire maneuver.

3. Turning the tail of the helicopter into theslope.

4. Lowering the downslope skid or wheel toorapidly.

5. Applying excessive cyclic control into theslope, causing mast bumping.

SLOPE TAKEOFFA slope takeoff is basically the reverse of a slopelanding. [Figure 10-7] Conditions that may be

Figure 10-7. Slope takeoff.

Figure 10-8. If the wind velocity is 10 knots or greater, you shouldexpect updrafts on the windward side and downdrafts on the leeside of obstacles. You should plan the approach with these factorsin mind, but be ready to alter your plans if the wind speed or direc-tion changes.

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associated with the slope, such as turbulence andobstacles, must be considered during the takeoff.Planning should include suitable forced landingareas.

TECHNIQUEBegin the takeoff by increasing r.p.m. to the nor-mal range with the collective full down. Then,move the cyclic toward the slope (frame 1).Holding cyclic toward the slope causes thedownslope skid to rise as you slowly raise the col-lective (frame 2). As the skid comes up, move thecyclic toward the neutral position. If properly coor-dinated, the helicopter should attain a level atti-tude as the cyclic reaches the neutral position. Atthe same time, use antitorque pedal pressure tomaintain heading and throttle to maintain r.p.m.With the helicopter level and the cyclic centered,pause momentarily to verify everything is correct,and then gradually raise the collective to completethe liftoff (frame 3).

After reaching a hover, take care to avoid hittingthe ground with the tail rotor. If an upslope windexists, execute a crosswind takeoff and then makea turn into the wind after clearing the ground withthe tail rotor.

COMMON ERRORS

1. Failure to adjust cyclic control to keep thehelicopter from sliding downslope.

2. Failure to maintain proper r.p.m.

3. Holding excessive cyclic into the slope as thedownslope skid is raised.

4. Turning the tail of the helicopter into theslope during takeoff.

CONFINED AREA OPERATIONSA confined area is an area where the flight of thehelicopter is limited in some direction by terrain orthe presence of obstructions, natural or man-made. For example, a clearing in the woods, a citystreet, a road, a building roof, etc., can each beregarded as a confined area. Generally, takeoffsand landings should be made into the wind toobtain maximum airspeed with minimum ground-speed.

There are several things to consider when operat-ing in confined areas. One of the most important ismaintaining a clearance between the rotors andobstacles forming the confined area. The tail rotordeserves special consideration because, in somehelicopters, you cannot always see it from thecabin. This not only applies while making theapproach, but while hovering as well. Another con-sideration is that wires are especially difficult to see; however, their supporting devices, such as poles or towers, serve as an indication of their presence andapproximate height. If any wind is present, youshould also expect some turbulence. [Figure 10-8]

Something else for you to consider is the avail -ability of forced landing areas during the plannedapproach. You should think about the possibility offlying from one alternate landing area to anotherthroughout the approach, while avoiding unfavor-able areas. Always leave yourself a way out incase the landing cannot be completed or a go-around is necessary.

APPROACHA high reconnaissance should be completedbefore initiating the confined area approach. Startthe approach phase using the wind and speed tothe best possible advantage. Keep in mind areassuitable for forced landing. It may be necessary tochoose between an approach that is crosswind,but over an open area, and one directly into thewind, but over heavily wooded or extremely roughterrain where a safe forced landing would beimpossible. If these conditions exist, consider thepossibility of making the initial phase of theapproach crosswind over the open area and thenturning into the wind for the final portion of theapproach.

Always operate the helicopter as close to its nor-mal capabilities as possible, taking into considera-tion the situation at hand. In all confined areaoperations, with the exception of the pinnacleoperation, the angle of descent should be nosteeper than necessary to clear any barrier in theapproach path and still land on the selected spot.The angle of climb on takeoff should be normal, ornot steeper than necessary to clear any barrier.Clearing a barrier by a few feet and maintainingnormal operating r.p.m., with perhaps a reserve ofpower, is better than clearing a barrier by a widemargin but with a dangerously low r.p.m. and nopower reserve.

Always make the landing to a specific point andnot to some general area. This point should belocated well forward, away from the approach endof the area. The more confined the area, the more

Altitude over Airspeed—In this type of maneuver, it is more importantto gain altitude than airspeed. However, unless operational consider-ations dictate otherwise, the crosshatched or shaded areas of theheight/velocity diagram should be avoided.

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essential it is that you land the helicopter preciselyat a definite point. Keep this point in sight duringthe entire final approach.

When flying a helicopter near obstructions, alwaysconsider the tail rotor. A safe angle of descent overbarriers must be established to ensure tail rotorclearance of all obstructions. After coming to ahover, take care to avoid turning the tail intoobstructions.

TAKEOFFA confined area takeoff is considered an altitudeover airspeed maneuver. Before takeoff, make a

ground reconnaissance to determine the type oftakeoff to be performed, to determine the pointfrom which the takeoff should be initiated toensure the maximum amount of available area,and finally, how to best maneuver the helicopterfrom the landing point to the proposed takeoffposition.

If wind conditions and available area permit, thehelicopter should be brought to a hover, turnedaround, and hovered forward from the landingposition to the takeoff position. Under certain con-ditions, sideward flight to the takeoff position maybe necessary. If rearward flight is required toreach the takeoff position, place reference mark-ers in front of the helicopter in such a way that aground track can be safely followed to the takeoffposition. In addition, the takeoff marker should belocated so that it can be seen without hoveringbeyond it.

When planning the takeoff, consider the directionof the wind, obstructions, and forced landingareas. To help you fly up and over an obstacle,you should form an imaginary line from a point onthe leading edge of the helicopter to the highestobstacle to be cleared. Fly this line of ascent withenough power to clear the obstacle by a safe distance. After clearing theobstacle, maintain the power setting and acceler-ate to the normal climb speed. Then, reducepower to the normal climb power setting.

COMMON ERRORS1. Failure to perform, or improper performance

of, a high or low reconnaissance.

2. Flying the approach angle at too steep or tooshallow an approach for the existing condi-tions.

3. Failing to maintain proper r.p.m.

4. Failure to consider emergency landingareas.

5. Failure to select a specific landing spot.

6. Failure to consider how wind and turbulencecould affect the approach.

Figure 10-9. When flying an approach to a pinnacle or ridgeline,avoid the areas where downdrafts are present, especially whenexcess power is limited. If you encounter downdrafts, it maybecome necessary to make an immediate turn away from the pin-nacle to avoid being forced into the rising terrain.

Airspeed over Altitude—This means that in this maneuver, obstaclesare not a factor, and it is more important to gain airspeed than alti-tude.

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7. Improper takeoff and climb technique forexisting conditions.

PINNACLE AND RIDGELINEOPERATIONSA pinnacle is an area from which the surface dropsaway steeply on all sides. A ridgeline is a longarea from which the surface drops away steeplyon one or two sides, such as a bluff or precipice.The absence of obstacles does not necessarilylessen the difficulty of pinnacle or ridgeline opera-tions. Updrafts, downdrafts, and turbulence,together with unsuitable terrain in which to make aforced landing, may still present extreme hazards.

APPROACH AND LANDINGIf you need to climb to a pinnacle or ridgeline, do iton the upwind side, when practicable, to takeadvantage of any updrafts. The approach flightpath should be parallel to the ridgeline and intothe wind as much as possible. [Figure 10-9]

Load, altitude, wind conditions, and terrain fea-tures determine the angle to use in the final part ofan approach. As a general rule, the greater thewinds, the steeper the approach needs to be toavoid turbulent air and downdrafts. Groundspeedduring the approach is more difficult to judgebecause visual references are farther away thanduring approaches over trees or flat terrain. If acrosswind exists, remain clear of downdrafts onthe leeward or downwind side of the ridgeline. If the wind velocity makes the crosswindlanding hazardous, you may be able to make alow, coordinated turn into the wind just prior to ter-minating the approach. When making anapproach to a pinnacle, avoid leeward turbulenceand keep the helicopter within reach of a forcedlanding area as long as possible.

On landing, take advantage of the long axis of thearea when wind conditions permit. Touchdownshould be made in the forward portion of the area.Always perform a stability check, prior to reducingr.p.m., to ensure the landing gear is on firm terrainthat can safely support the weight of the helicop-ter.

TAKEOFFA pinnacle takeoff is an airspeed over altitudemaneuver made from the ground or from a hover.S i n c epinnacles and ridgelines are generally higher thanthe immediate surrounding terrain, gaining air-speed on the takeoff is more important than gain-ing altitude. The higher the airspeed, the more

rapid the departure from slopes of the pinnacle. Inaddition to covering unfavorable terrain rapidly, ahigher airspeed affords a more favorable glideangle and thus contributes to the chances ofreaching a safe area in the event of a forced land-ing. If a suitable forced landing area is not avail-able, a higher airspeed also permits a moreeffective flare prior to making an autorotative land-ing.

On takeoff, as the helicopter moves out of groundeffect, maintain altitude and accelerate to normalclimb airspeed. When normal climb speed isattained, establish a normal climb attitude. Neverdive the helicopter down the slope after clearingthe pinnacle.

COMMON ERRORS

1. Failure to perform, or improper performanceof, a high or low reconnaissance.

2. Flying the approach angle at too steep or tooshallow an approach for the existing condi-tions.

3. Failure to maintain proper r.p.m.

4. Failure to consider emergency landingareas.

5. Failure to consider how wind and turbulencecould affect the approach and takeoff.

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Today helicopters are quite reliable. However emergencies do occur, whether a result ofmechanical failure or pilot error. By having a thor-ough knowledge of the helicopter and its systems,you will be able to more readily handle the situ-ation. In addition, by knowing the conditions thatcan lead to an emergency, many potential accidents can beavoided.

AUTOROTATIONIn a helicopter, an autorotation is a descendingmaneuver where the engine is disengaged fromthe main rotor system and the rotor blades aredriven solely by the upward flow of air through therotor. In other words, the engine is no longer sup-plying power to the main rotor.

The most common reason for an autorotation isan engine failure, but autorotations can also beperformed in the event of a complete tail rotor fail-ure, since there is virtually no torque produced inan autorotation. If altitude permits, they can alsobe used to recover from settling with power. If theengine fails, the freewheeling unit automaticallydisengages the engine from the main rotor allow-ing the main rotor to rotate freely. Essentially, thefreewheeling unit disengages anytime the enginer.p.m. is less than the rotor r.p.m.

At the instant of engine failure, the main rotorblades are producing lift and thrust from their angleof attack and velocity. By immediately lowering col-lective pitch, which must be done in case of anengine failure, lift and drag are reduced, and thehelicopter begins an immediate descent, thus pro-ducing an upward flow of air through the rotor sys-tem. This upward flow of air through the rotorprovides sufficient thrust to maintain rotor r.p.m.throughout the descent. Since the tail rotor isdriven by the main rotor transmission duringautorotation, heading control is maintained as innormal flight.

Several factors affect the rate of descent inautorotation; density altitude, gross weight, rotorr.p.m., and airspeed. Your primary control of therate of descent is airspeed. Higher or lower air-speeds are obtained with the cyclic pitch control

just as in normal flight. In theory, you have a choice in the angle ofdescent varying from a vertical descent to maxi-mum range, which is the minimum angle ofdescent. Rate of descent is high at zero airspeedand decreases to a minimum at approximately 50to 60 knots, depending upon the particular heli-copter and the factors just mentioned. As the air-speed increases beyond that which givesminimum rate of descent, the rate of descentincreases again.

When landing from an autorotation, the energystored in the rotating blades is used to decreasethe rate of descent and make a soft landing. Agreater amount of rotor energy is required to stopa helicopter with a high rate of descent than isrequired to stop a helicopter that is descendingmore slowly. Therefore, autorotative descents atvery low or very high airspeeds are more criticalthan those performed at the minimum rate ofdescent airspeed.

Each type of helicopter has a specific airspeed atwhich a power-off glide is most efficient. The bestairspeed is the one which combines the greatestglide range with the slowest rate of descent. Thespecific airspeed is somewhat different for eachtype of helicopter, yet certain factors affect all configurations in the samemanner. For specific autorotation airspeeds for aparticular helicopter, refer to the FAA-approvedrotorcraft flight manual.

The specific airspeed for autorotations is estab-lished for each type of helicopter on the basis ofaverage weather and wind conditions and normalloading. When the helicopter is operated withheavy loads in high density altitude or gusty windconditions, best performance is achieved from a slightly increasedairspeed in the descent. For autorotations at lowdensity altitude and light loading, best perform-ance is achieved from a slight decrease in normalairspeed. Following this general procedure of fit-ting airspeed to existing conditions, you canachieve approximately the same glide angle in

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any set of circumstances and estimate the touch-down point.

When making turns during an autorotation, gener-ally use cyclic control only. Use of antitorque ped-als to assist or speed the turn causes loss ofairspeed and downward pitching of the nose.When an autorotation is initiated, sufficient anti-torque pedal pressure should be used to maintainstraight flight and prevent yawing. This pressureshould not be changed to assist the turn.

Use collective pitch control to manage rotor r.p.m.If rotor r.p.m. builds too high during an autorota-tion, raise the collective sufficiently to decreaser.p.m. back to the normal operating range. If ther.p.m. begins decreasing, you have to again lowerthe collective. Always keep the rotor r.p.m. withinthe established range for your helicopter. During aturn, rotor r.p.m. increases due to the increasedback cyclic control pressure, which induces agreater airflow through the rotor system. Ther.p.m. builds rapidly and can easily exceed themaximum limit if not controlled by use of collective.The tighter the turn and the heavier the grossweight, the higher the r.p.m.

To initiate an autorotation, other than in a lowhover, lower the collective pitch control. Thisholds true whether performing a practice autoro-tation or in the event of an in-flight engine fail-ure. This reduces the pitch of the main rotorblades and allows them to continue turning atnormal r.p.m. During practice autorotations,maintain the r.p.m. in the green arc with thethrottle while lowering collective. Once the col-lective is fully lowered, reduce engine r.p.m. bydecreasing the throttle. This causes a split of theengine and rotor r.p.m. needles.

STRAIGHT-IN AUTOROTATIONA straight-in autorotation implies an autorotationfrom altitude with no turns. The speed at touch-down and the resulting ground run depends on therate and amount of flare. The greater the degreeof flare and the longer it is held, the slower thetouchdown speed and the shorter the ground run.The slower the speed desired at touchdown, themore accurate the timing and speed of the flaremust be, especially in helicopters with low inertiarotor systems.

TECHNIQUERefer to figure 11-1 (position 1). From level flightat the manufacturer’s recommended airspeed,between 500 to 700 feet AGL, and heading intothe wind, smoothly, but firmly lower the collectivepitch control to the full down position, maintaining

r.p.m. in the green arc with throttle. Coordinate thecollective movement with proper antitorque pedalfor trim, and apply aft cyclic control to maintainproper airspeed. Once the collective is fully low-ered, decrease throttle to ensure a clean split ofthe needles. After splitting the needles, readjustthe throttle to keep engine r.p.m. above normal idling speed, but not high enough to causerejoining of the needles. The manufacturer often recommends the proper r.p.m.

At position 2, adjust attitude with cyclic control toobtain the manufacturer’s recommended autoro-tation or best gliding speed. Adjust collective pitchcontrol, as necessary, to maintain rotor r.p.m. inthe green arc. Aft cyclic movements cause anincrease in rotor r.p.m., which is then controlled bya small increase in collective pitch control. Avoid alarge collective pitch increase, which results in arapid decay of rotor r.p.m., and leads to “chasingthe r.p.m.” Avoid looking straight down in front ofthe aircraft. Continually cross-check attitude, trim,rotor r.p.m., and airspeed.

At approximately 40 to 100 feet above the surface,or at the altitude recommended by the manufac-turer (position 3), begin the flare with aft cycliccontrol to reduce forward airspeed and decreasethe rate of descent. Maintain heading with the anti-torque pedals. Care must be taken in the execu-tion of the flare so that the cyclic control is notmoved rearward so abruptly as to cause the heli-copter to climb, nor should it be moved so slowlyas to not arrest the descent, which may allow thehelicopter to settle so rapidly that the tail rotorstrikes the ground. When forward motion

Figure 11-1. Straight-in autorotation.

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decreases to the desired groundspeed, which isusually the slowest possible speed (position 4),move the cyclic control forward to place the heli-copter in the proper attitude for landing.

The altitude at this time should be approximately8 to 15 feet AGL, depending on the altitude rec-ommended by the manufacturer. Extreme cautionshould be used to avoid an excessive nose highand tail low attitude below 10 feet. At this point, if afull touchdown landing is to be made, allow thehelicopter to descend vertically (position 5).Increase collective pitch, as necessary, to checkthe descent and cushion the landing. Additionalantitorque pedal is required to maintain headingas collective pitch is raised due to the reduction inrotor r.p.m. and the resulting reduced effect of thetail rotor. Touch down in a level flight attitude.

A power recovery can be made during training inlieu of a full touchdown landing. Refer to the sec-tion on power recoveries for the correct technique.

After touchdown and after the helicopter has cometo a complete stop, lower the collective pitch to thefull-down position. Do not try to stop the forwardground run with aft cyclic, as the main rotor bladescan strike the tail boom. Rather, by lowering thecollective slightly during the ground run, moreweight is placed on the undercarriage, slowing thehelicopter.

COMMON ERRORS

1. Failing to use sufficient antitorque pedalwhen power is reduced.

2. Lowering the nose too abruptly when poweris reduced, thus placing the helicopter in adive.

3. Failing to maintain proper rotor r.p.m. during the descent.

4. Application of up-collective pitch at an exces-sive altitude resulting in a hard landing, losso fheading control, and possible damage to thetail rotor and to the main rotor blade stops.

5. Failing to level the helicopter.

POWER RECOVERY FROM PRACTICEAUTOROTATIONA power recovery is used to terminate practiceautorotations at a point prior to actual touch-down. After the power recovery, a landing canbe made or a go-around initiated.

TECHNIQUEAt approximately 8 to 15 feet above the ground,depending upon the helicopter being used, beginto level the helicopter with forward cyclic control.Avoid excessive nose high, tail low attitude below10 feet. Just prior to achieving level attitude, withthe nose still slightly up, coordinate upward collec-tive pitch control with an increase in the throttle tojoin the needles at operating r.p.m. The throttleand collective pitch must be coordinated properly.If the throttle is increased too fast or too much, anengine overspeed can occur; if throttle isincreased too slowly or too little in proportion tothe increase in collective pitch, a loss of rotorr.p.m. results. Use sufficient collective pitch to stopthe descent and coordinate proper antitorquep e d a lpressure to maintain heading. When a landing isto be made following the power recovery, bring thehelicopter to a hover at normal hovering altitudeand then descend to a landing.

If a go-around is to be made, the cyclic controlshould be moved forward to resume forward flight.In transitioning from a practice autorotation to ago-around, exercise care to avoid an altitude-air-speed combination that would place the helicopterin an unsafe area of its height-velocity diagram.

COMMON ERRORS

1. Initiating recovery too late, requiring a rapidapplication of controls, resulting in overcon-trolling.

2. Failing to obtain and maintain a level attitudenear the surface.

3. Failing to coordinate throttle and collectivepitch properly, resulting in either an engineoverspeed or a loss of r.p.m.

4. Failing to coordinate proper antitorque pedalwith the increase in power

AUTOROTATIONS WITH TURNSA turn, or a series of turns, can be made during anautorotation in order to land into the wind or avoidobstacles. The turn is usually made early so thatthe remainder of the autorotation is the same as astraight in autorotation. The most common typesare 90° and 180° autorotations. The techniquebelow describes a 180° autorotation.

TECHNIQUEEstablish the aircraft on downwind at recom-m e n d e dairspeed at 700 feet AGL, parallel to the touchdownarea. In a no wind or headwind condition, establish

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the ground track approximately 200 feet away fromthe touchdown point. If a strong crosswind exists, itwill be necessary to move your downwind legcloser or farther out. When abeam the intendedtouchdown point, reduce collective, and then split the needles. Apply proper antitorque pedal and cyclic to maintain proper atti-tude. Cross check attitude, trim, rotor r.p.m., andairspeed.

After the descent and airspeed is established, rollinto a 180° turn. For training, you should initiallyroll into a bank of a least 30°, but no more than40°. Check your airspeed and rotor r.p.m.Throughout the turn, it is important to maintain theproper airspeed and keep the aircraft in trim.Changes in the aircraft’s attitude and the angle ofbank cause a corresponding change in rotor r.p.m.Adjust the collective, as necessary, in the turn tomaintain rotor r.p.m. in the green arc.

At the 90° point, check the progress of your turn byglancing toward your landing area. Plan the second 90 degrees of turn to roll out on the centerline. If youare too close, decrease the bank angle; if too far out,increase the bank angle. Keep the helicopter in trimwith antitorque pedals.

The turn should be completed and the helicopteraligned with the intended touchdown area prior topassing through 100 feet AGL. If the collectivepitch was increased to control the r.p.m., it mayhave to be lowered on roll out to prevent a decay in r.p.m.Make an immediate power recovery if the aircraftis not aligned with the touchdown point, and if therotor r.p.m. and/or airspeed is not within properlimits.

From this point, complete the procedure as if itwere a straight-in autorotation.

POWER FAILURE IN A HOVERPower failures in a hover, also called hoveringautorotations, are practiced so that you automati-cally make the correct response when confrontedwith engine stoppage or certain other emergencies while hov-ering. The techniques discussed in this sectionrefer to helicopters with a counter-clockwise rotorsystem and an antitorque rotor.

TECHNIQUETo practice hovering autorotations, establish anormal hovering altitude for the particular helicop-ter being used, considering load and atmosphericconditions. Keep the helicopter headed into thewind and hold maximum allowable r.p.m.

To simulate a power failure, firmly roll the throttleinto the spring loaded override position, if applica-ble. This disengages the driving force of theengine from the rotor, thus eliminating torqueeffect. As the throttle is closed, apply proper anti-torque pedal to maintain heading. Usually, a slightamount of right cyclic control is necessary to keepthe helicopter from drifting to the left, to compen-sate for the loss of tail rotor thrust. However, usecyclic control, as required, to ensure a verticaldescent and a level attitude. Leave the collectivepitch where it is on entry.

Helicopters with low inertia rotor systems willbegin to settle immediately. Keep a level attitudeand ensure a vertical descent with cyclic controlwhile maintaining heading with the pedals. Atapproximately 1 foot above the surface, applyupward collective pitch control, as necessary, toslow the descent and cushion the landing. Usuallythe full amount of collective pitch is required. Asupward collective pitch control is applied, thethrottle has to be held in the closed position to pre-vent the rotor from re-engaging.

Helicopters with high inertia rotor systems willmaintain altitude momentarily after the throttle isclosed. Then, as the rotor r.p.m. decreases, the hel-icopter starts to settle. When the helicopter has set-tled to approximately 1 foot above the surface,apply upward collective pitch control while holdingthe throttle in the closed position to slow thedescent and cushion the landing. The timing of col-lective pitch control application, and the rate atwhich it is applied, depends upon the particular hel-icopter being used, its gross weight, and the exist-ing atmospheric conditions. Cyclic control is usedto maintain a level attitude and to ensure a verticaldescent. Maintain heading with antitorque pedals.

When the weight of the helicopter is entirely onthe skids, cease the application of upward collec-tive. When the helicopter has come to a completestop, lower the collective pitch to the full downposition.

The timing of the collective pitch is a most impor-tant consideration. If it is applied too soon, theremaining r.p.m. may not be sufficient to make asoft landing. On the other hand, if collective pitchcontrol is applied too late, surface contact may bemade before sufficient blade pitch is available tocushion the landing.

COMMON ERRORS

1. Failing to use sufficient proper antitorquepedal when power is reduced.

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2. Failing to stop all sideward or backwardmovement prior to touchdown.

3. Failing to apply up-collective pitch properly,resulting in a hard touchdown.

4. Failing to touch down in a level attitude.

5. Not rolling the throttle completely to idle.

HEIGHT/VELOCITY DIAGRAMA height/velocity (H/V) diagram, published by themanufacturer for each model of helicopter, depictsthe critical combinations of airspeed and altitudeshould an engine failure occur. Operating at thealtitudes and airspeeds shown within the cross-hatched or shaded areas of the H/V diagram maynot allow enough time for the critical transitionfrom powered flight to autorotation. [Figure 11-2]

An engine failure in a climb after takeoff occurringin section A of the diagram is most critical. Duringa climb, a helicopter is operating at higher powersettings and blade angle of attack. An engine fail-ure at this point causes a rapid rotor r.p.m. decaybecause the upward movement of the helicoptermust be stopped, then a descent established inorder to drive the rotor. Time is also needed to sta-

bilize, then increase the r.p.m. to the normal oper-ating range. The rate of descent must reach avalue that is normal for the airspeed at themoment. Since altitude is insufficient for thissequence, you end up with decaying r.p.m., anincreasing sink rate, no deceleration lift, littletranslational lift, and little response to the applica-tion of collective pitch to cushion the landing.

It should be noted that, once a steady stateautorotation has been established, the H/V dia-gram no longer applies. An engine failure whiledescending through section A of the diagram, isless critical, provided a safe landing area is avail-able.

You should avoid the low altitude, high airspeed por-tion of the diagram (section B), because your recog-nition of an engine failure will most likely coincidewith, or shortly occur after, ground contact. Even ifyou detect an engine failure, there may not be suffi-cient time to rotate the helicopter from a nose low, high airspeed attitude toone suitable for slowing, then landing. Additionally,t h ealtitude loss that occurs during recognition of enginefailure and rotation to a landing attitude, may notleave enough altitude to prevent the tail skid from hit-ting the ground during the landing maneuver.

Basically, if the helicopter represented by this H/Vdiagram is above 445 feet AGL, you have enoughtime and altitude to enter a steady state autorota-tion, regardless of your airspeed. If the helicopteris hovering at 5 feet AGL (or less) in normal condi-tions and the engine fails, a safe hovering autoro-tation can be made. Between approximately 5 feetand 445 feet AGL, however, the transition toautorotation depends on the altitude and airspeed

Figure 11-2. By carefully studying the height/velocity diagram, you will be able to avoid the combinations of altitude andairspeed that may not allow you sufficient time or altitude to entera stabilized autorotative descent. You might want to refer to thisdiagram during the remainder of the discussion on the height/velocity diagram.

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of the helicopter. Therefore, you should always befamiliar with the height/velocity diagram for theparticular model of helicopter you are flying.

THE EFFECT OF WEIGHT VERSUSDENSITY ALTITUDEThe height/velocity diagram depicts altitude andairspeed situations from which a successfulautorotation can be made. The time required, andtherefore, altitude necessary to attain a steadystate autorotative descent, is dependent on theweight of the helicopter and the density altitude.For this reason, the H/V diagram for some heli-copter models is valid only when the helicopter isoperated in accordance with the gross weight vs.density altitude chart. Where appropriate, thischart is found in the rotorcraft flight manual for theparticular helicopter. [Figure 11-3]

Figure 11-3. Assuming a density altitude of 5,500 feet, theheight/velocity diagram in figure 11-2 would be valid up to a grossweight of approximately 1,700 pounds. This is found by entering thegraph at a density altitude of 5,500 feet (point A), then moving hori-zontally to the solid line (point B). Moving vertically to the bottom ofthe graph (point C), you find that with the existing density altitude, themaximum gross weight under which the height/velocity diagram isapplicable is 1,700 pounds.

The gross weight vs. density altitude chart is notintended as a restriction to gross weight, but as anadvisory to the autorotative capability of the heli-c o p t e rduring takeoff and climb. You must realize, how-ever, that at gross weights above those recom-

mended by the gross weight vs. density altitudechart, the H/V diagram is not restrictive enough.

VORTEX RING STATE (SETTLING WITHPOWER)Vortex ring state describes an aerodynamic condi-tion where a helicopter may be in a verticaldescent with up to maximum power applied, andlittle or no cyclic authority. The term “settling withpower” comes from the fact that helicopter keepssettling even though full engine power is applied.

In a normal out-of-ground-effect hover, the heli-copter is able to remain stationary by propelling alarge mass of air down through the main rotor.Some of the air is recirculated near the tips of theblades, curling up from the bottom of the rotor sys-tem and rejoining the air entering the rotor fromthe top. This phenomenon is common to all airfoilsand is known as tip vortices. Tip vortices consumeengine power but produce no useful lift. As longas the tip vortices are small, their only effect is asmall loss in rotor efficiency. However, when thehelicopter begins to descend vertically, it settlesinto its own downwash, which greatly enlarges thetip vortices. In this vortex ring state, most of thepower developed by the engine is wasted in accel-erating the air in a doughnut pattern around therotor.

In addition, the helicopter may descend at a ratethat exceeds the normal downward induced-flowrate of the inner blade sections. As a result, theairflow of the inner blade sections is upward rela-tive to the disc. This produces a secondary vortexring in addition to the normal tip-vortices. The sec-ondary vortex ring is generated about the point onthe blade where the airflow changes from up todown. The result is an unsteady turbulent flowover a large area of the disc. Rotor efficiency islost even though power is still being supplied fromthe engine. [Figure 11-4]A fully developed vortex ring state is characterizedby an unstable condition where the helicopterexperiences uncommanded pitch and roll oscilla-tions, has little or no cyclic authority, and achievesa descent rate, which, if allowed to develop, mayapproach 6,000 feet per minute. It is accompaniedby increased levels of vibration.

A vortex ring state may be entered during anymaneuver that places the main rotor in a conditionof high upflow and low forward airspeed. This con-dition is sometimes seen during quick-stop type maneu-vers or during recoveries from autorotations. The

Figure 11-4. Vortex ring state.

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following combination of conditions are likely tocause settling in a vortex ring state:

1. A vertical or nearly vertical descent of at least300 feet per minute. (Actual critical ratedepends on the gross weight, r.p.m., densityaltitude, and other pertinent factors.)

2. The rotor system must be using some of theavailable engine power (from 20 to 100 per-cent).

3. The horizontal velocity must be slower thaneffective translational lift.

Some of the situations that are conducive to a set-tling with power condition are: attempting to hoverout of ground effect at altitudes above the hover-ing ceiling of the helicopter; attempting to hoverout of ground effect without maintaining precisealtitude control; or downwind and steep powerapproaches in which airspeed is permitted to dropto nearly zero.

When recovering from a settling with power condi-tion, the tendency on the part of the pilot is to firsttry to stop the descent by increasing collectivepitch. However, this only results in increasing thestalled area of the rotor, thus increasing the rate ofdescent. Since inboard portions of the blades arestalled, cyclic control is limited. Recovery is accomplished by increasing forward speed, and/or partially lowering collectivepitch. In a fully developed vortex ring state, theonly recovery may be to enter autorotation tobreak the vortex ring state. When cyclic authority isregained, you can then increase forward airspeed.

For settling with power demonstrations and train-ing in recognition of vortex ring state conditions,all maneuvers should be performed at an eleva-tion of at least 1,500 feet AGL.

To enter the maneuver, reduce power belowhover power. Hold altitude with aft cyclic untilt h eairspeed approaches 20 knots. Then allow thesink rate to increase to 300 feet per minute ormore as the attitude is adjusted to obtain an air-speed of less than 10 knots. When the aircraftbegins to shudder, the application of additionalup collective increases the vibration and sinkrate.

Recovery should be initiated at the first sign ofvortex ring state by applying forward cyclic toincrease airspeed and simultaneously reducing

collective. The recovery is complete when theaircraft passes through effective translational liftand a normal climb is established.

RETREATING BLADE STALLIn forward flight, the relative airflow through themain rotor disc is different on the advancing andretreating side. The relative airflow over theadvancing side is higher due to the forwardspeed of the helicopter, while the relative airflow on theretreating side is lower. This dissymmetry of liftincreases as forward speed increases.

To generate the same amount of lift across therotor disc, the advancing blade flaps up whilethe retreating blade flaps down. This causes theangle of attack to decrease on the advancingblade, which reduces lift, and increase on theretreating blade, which increases lift. As the for-ward speed increases, at some point the lowblade speed on the retreating blade, togetherwith its high angle of attack, causes a loss of lift(stall).

Retreating blade stall is a major factor in limit-ing a helicopter’s top forward speed (VNE) andcan be felt developing by a low frequency vibra-tion, pitching up of the nose, and a roll in thedirection of the retreating blade. High weight,low rotor r.p.m., high density altitude, turbu-lence and/or steep, abrupt turns are all con-ducive to retreating blade stall at high forwardairspeeds. As altitude is increased, higher bladeangles are required to maintain lift at a givenairspeed. Thus, retreating blade stall is encoun-tered at a lower forward airspeed at altitude.Most manufacturers publish charts and graphsshowing a VNE decrease with altitude.

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When recovering from a retreating blade stallcondition, moving the cyclic aft only worsensthe stall as aft cyclic produces a flare effect, thusincreasing angles of attack. Pushing forward onthe cyclic also deepens the stall as the angle of attack onthe retreating blade is increased. Correct recov-ery from retreating blade stall requires the col-lective to be lowered first, which reduces bladeangles and thus angle of attack. Aft cyclic canthen be used to slow the helicopter.

GROUND RESONANCEGround resonance is an aerodynamic phenom-enon associated with fully-articulated rotor sys-tems. It develops when the rotor blades moveout of phase with each other and cause therotor disc to become unbalanced. This condi -tion can cause a helicopter to self-destruct in a matter of seconds. However,for this condition to occur, the helicopter mustbe in contact with the ground.

If you allow your helicopter to touch down firmlyon one corner (wheel type landing gear is most conducive for this) the shock is transmitted tothe main rotor system. This may cause theblades to move out of their normal relationshipwith each other. This movement occurs alongthe drag hinge. [Figure 11-5]

Figure 11-5. Hard contact with the ground can send a shock waveto the main rotor head, resulting in the blades of a three-bladedrotor system moving from their normal 120° relationship to eachother. This could result in something like 122°, 122°, and 116°between blades. When one of the other landing gear strikes the surface, the unbalanced condition couldbe further aggravated.

If the r.p.m. is low, the corrective action to stopground resonance is to close the throttle immediatelyand fully lower the collective to place the blades inlow pitch. If the r.p.m. is in the normal operatingrange, you should fly the helicopter off the ground,and allow the blades to automatically realign them-selves. You can then make a normal touchdown. Ifyou lift off and allow the helicopter to firmly re-contactthe surface before the blades are realigned, a sec-ond shock could move the blades again and aggra-vate the already unbalanced condition. This couldlead to a violent, uncontrollable oscillation.

This situation does not occur in rigid or semirigidrotor systems, because there is no drag hinge. Inaddition, skid type landing gear are not as proneto ground resonance as wheel type gear.

DYNAMIC ROLLOVERA helicopter is susceptible to a lateral rolling ten-dency, called dynamic rollover, when lifting off thesurface. For dynamic rollover to occur, some fac-tor has to first cause the helicopter to roll or pivotaround a skid, or landing gear wheel, until its criti-cal rollover angle is reached. Then, beyond thispoint, main rotor thrust continues the roll andrecovery is impossible. If the critical rollover angleis exceeded, the helicopter rolls on its side regard-less of the cyclic corrections made.

Dynamic rollover begins when the helicopterstarts to pivot around its skid or wheel. This canoccur for a variety of reasons, including the failure

Figure 11-6. Forces acting on a helicopter with right skid on theground. Figure 11-7. Upslope rolling motion.

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to remove a tiedown or skid securing device, or ifthe skid or wheel contacts a fixed object while hov-ering sideward, or if the gear is stuck in ice, softasphalt, or mud. Dynamic rollover may also occurif you do not use the proper landing or takeofftechnique or while performing slope operations.Whatever the cause, if the gear or skid becomes apivot point, dynamic rollover is possible if you donot use the proper corrective technique.

Once started, dynamic rollover cannot be stoppedby application of opposite cyclic control alone. Forexample, the right skid contacts an object andbecomes the pivot point while the helicopter startsrolling to the right. Even with full left cyclic applied,the main rotor thrust vector and its moment fol-lows the aircraft as it continues rolling to the right.Quickly applying down collective is the most effec-tive way to stop dynamic rollover from developing.Dynamic rollover can occur in both skid and wheelequipped helicopters, and all types of rotor sys-tems.

CRITICAL CONDITIONSCertain conditions reduce the critical rolloverangle, thus increasing the possibility for dynamicrollover and reducing the chance for recovery. Therate of rolling motion is also a consideration,because as the roll rate increases, the critical

rollover angle at which recovery is still possible, isreduced. Other critical conditions include operat-ing at high gross weights with thrust (lift) approxi-mately equal to the weight.

Refer to figure 11-6. The following conditions aremost critical for helicopters with counter-clock-wise rotor rotation:

1. right side skid/wheel down, since translatingtendency adds to the rollover force.

2. right lateral center of gravity.

3. crosswinds from the left.

4. left yaw inputs.

For helicopters with clockwise rotor rotation, theopposite would be true.

CYCLIC TRIMWhen maneuvering with one skid or wheel on theground, care must be taken to keep the helicoptercyclic control properly trimmed. For example, if aslow takeoff is attempted and the cyclic is not posi-tioned and trimmed to account for translating ten-dency, the critical recovery angle may beexceeded in less than two seconds. Control canbe maintained if you maintain proper cyclic posi-tion and trim, and not allow the helicopter’s rolland pitch rates to become too great. You shouldfly your helicopter into the air smoothly whilekeeping movements of pitch, roll, and yaw small,and not allow any untrimmed cyclic pressures.

NORMAL TAKEOFFS AND LANDINGSDynamic rollover is possible even during normaltakeoffs and landings on relative level ground, ifone wheel or skid is on the ground and thrust (lift)is approximately equal to the weight of the heli-copter. If the takeoff or landing is not performed properly, a rollrate could develop around the wheel or skid that ison the ground. When taking off or landing, performthe maneuver smoothly and trim the cyclic so thatno pitch or roll movement rates build up, espe-cially the roll rate. If the bank angle starts toincrease to an angle of approximately 5 to 8°, andfull corrective cyclic does not reduce the angle,the collective should be reduced to diminish theunstable rolling condition.

SLOPE TAKEOFFS AND LANDINGSDuring slope operations, excessive application ofcyclic control into the slope, together with exces-sive collective pitch control, can result in the downs-lope skid rising sufficiently to exceed lateral cyclic control limits,and an upslope rolling motion can occur. [Figure11-7]

When performing slope takeoff and landingmaneuvers, follow the published procedures andkeep the roll rates small. Slowly raise the downs-

Figure 11-8. Downslope rolling motion.

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lope skid or wheel to bring the helicopter level,and then lift off. During landing, first touch downon the upslope skid or wheel, then slowly lowerthe downslope skid or wheel using combinedmovements of cyclic and collective. If the helicop-ter rolls approximately 5 to 8° to the upslope side,decrease collective to correct the bank angle andreturn to level attitude, then start the landing pro-cedure again.

USE OF COLLECTIVEThe collective is more effective in controlling therolling motion than lateral cyclic, because it reducesthe main rotor thrust (lift). A smooth, moderate col-lective reduction, at a rate less than approximatelyfull up to full down in two seconds, is adequate tostop the rolling motion. Take care, however, not todump collective at too high a rate, as this maycause a main rotor blade to strike the fuselage.Additionally, if the helicopter is on a slope and theroll starts to the upslope side, reducing collectivetoo fast may create a high roll rate in the oppositedirection. When the upslope skid/wheel hits theground, the dynamics of the motion can cause thehelicopter to bounce off the upslope skid/wheel,and the inertia can cause the helicopter to roll aboutthe downslope ground contact point and over on itsside. [Figure 11-8]

The collective should not be pulled suddenly toget airborne, as a large and abrupt rolling momentin the opposite direction could occur. Excessiveapplication of collective can result in the upslopeskid rising sufficiently to exceed lateral cyclic con-

trol limits. This movement may be uncontrollable.If the helicopter develops a roll rate with oneskid/wheel on the ground, the helicopter can rollover on its side.

PRECAUTIONSThe following lists several areas to help you avoiddynamic rollover.

1. Always practice hovering autorotations intothe wind, but never when the wind is gusty orover 10 knots.

2. When hovering close to fences, sprinklers,bushes, runway/taxi lights, or other obstaclesthat could catch a skid, use extreme caution.

3. Always use a two-step liftoff. Pull in justenough collective pitch control to be light onthe skids and feel for equilibrium, then gentlylift the helicopter into the air.

4. When practicing hovering maneuvers closeto the ground, make sure you hover highenough to have adequate skid clearancewith any obstacles, especially when practic-ing sideways or rearward flight.

5. When the wind is coming from the upslopedirection, less lateral cyclic control will beavailable.

6. Tailwind conditions should be avoided when conducting slope operations.

7. When the left skid/wheel is upslope, less lat-eral cyclic control is available due to thetranslating tendency of the tail rotor. (This istrue for counter-rotating rotor systems)

8. If passengers or cargo are loaded orunloaded, the lateral cyclic requirementchanges.

9. If the helicopter utilizes interconnecting fuellines that allow fuel to automatically transferfrom one side of the helicopter to the other,the gravitational flow of fuel to the downslopetank could change the center of gravity, result-ing in a different amount of cyclic control appli-cation to obtain the same lateral result.

10. Do not allow the cyclic limits to be reached. Ifthe cyclic control limit is reached, further low-ering of the collective may cause mast bump-ing. If this occurs, return to a hover and selecta landing point with a lesser degree of slope.

11. During a takeoff from a slope, if the upslopeskid/wheel starts to leave the ground beforethe downslope skid/wheel, smoothly and

Figure 11-9. In a low G condition, improper corrective action couldlead to the main rotor hub contacting the rotor mast. The contactwith the mast becomes more violent with each successive flap-ping motion. This, in turn, creates a greater flapping displacement.The result could be a severely damaged rotor mast, or the main rotor system could separatefrom the helicopter.

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gently lower the collective and check to seeif the downslope skid/wheel is caught onsomething. Under these conditions verticalascent is the only acceptable method ofliftoff.

12. During flight operations on a floating platform, ifthe platform is pitching/rolling while attemptingto land or takeoff, the result could be dynamicrollover.

LOW G CONDITIONS AND MASTBUMPINGFor cyclic control, small helicopters depend pri-marily on tilting the main rotor thrust vector to pro-d u c econtrol moments about the aircraft center of grav-ity (CG), causing the helicopter to roll or pitch inthe desired direction. Pushing the cyclic controlforward abruptly from either straight-and-levelflight or after a climb can put the helicopter into alow G (weightless) flight condition. In forwardflight, when a push-over isperformed, the angle of attack and thrust of therotor is reduced, causing a low G or weightlessflight condition. During the low G condition, the lat-eral cyclic has little, if any, effect because the rotorthrust has been reduced. Also, in a counter-clock-wise rotor system (a clockwise system would bethe reverse), there is no main rotor thrust compo-nent to the left to counteract the tail rotor thrust tothe right, and since the tail rotor is above the CG,the tail rotor thrust causes the helicopter to rollrapidly to the right, If you attempt to stop the rightroll by applying full left cyclic before regainingmain rotor thrust, the rotor can exceed its flappinglimits and cause structural failure of the rotor shaftdue to mast bumping, or it may allow a blade tocontact the airframe. [Figure 11-9]

Since a low G condition could have disastrousresults, the best way to prevent it from happening isto avoid the conditions where it might occur. Thismeans avoiding turbulence as much as possible.If you do encounter turbulence, slow your forwardairspeed and make small control inputs. If turbu-lence becomes excessive, consider making a precautionary landing. To helpprevent turbulence induced inputs, make sureyour cyclic arm is properly supported. One way toaccomplish this is to brace your arm against yourleg. Even if you are not in turbulent conditions, youshould avoid abrupt movement of the cyclic andcollective.

If you do find yourself in a low G condition, which can be recognized by a feeling of weightlessness

and an uncontrolled roll to the right, you shouldimmediately and smoothly apply aft cyclic. Do notattempt to correct the rolling action with lateralcyclic. By applying aft cyclic, you will load the rotorsystem, which in turn produces thrust. Once thrustis restored, left cyclic control becomes effective,and you can roll the helicopter to a level attitude.

LOW ROTOR RPM AND BLADE STALLAs mentioned earlier, low rotor r.p.m. during anautorotation might result in a less than successfulmaneuver. However, if you let rotor r.p.m. decayto the point where all the rotor blades stall, theresult is usually fatal, especially when it occurs ataltitude. The danger of low rotor r.p.m. and bladestall is greatest in small helicopters with low bladeinertia. It can occur in a number of ways, such assimply rolling the throttle the wrong way, pullingmore collective pitch than power available, orwhen operating at a high density altitude.

When the rotor r.p.m. drops, the blades try tomaintain the same amount of lift by increasingpitch. As the pitch increases, drag increases,which requires more power to keep the bladesturning at the proper r.p.m. When power is nolonger available to maintain r.p.m., and thereforelift, the helicopter begins to descend. Thischanges the relative wind and further increasesthe angle of attack. At some point the blades willstall unless r.p.m. is restored. If all blades stall, itis almost impossible to get smooth air flowingacross the blades.

Even though there is a safety factor built into mosthelicopters, anytime your rotor r.p.m. falls belowthe green arc, and you have power, simultane-ously add throttle and lower the collective. If youare in forward flight, gently applying aft cyclicloads up the rotor system and helps increase rotorr.p.m. If you are without power,immediately lower the collective and apply aftcyclic.

RECOVERY FROM LOW ROTOR RPMUnder certain conditions of high weight, high tem-perature, or high density altitude, you might getinto a situation where the r.p.m. is low even though youare using maximum throttle. This is usually theresult of the main rotor blades having an angle ofattack that has created so much drag that enginepower is not sufficient to maintain or attain normaloperating r.p.m.

If you are in a low r.p.m. situation, the lifting power ofthe main rotor blades can be greatly diminished. As

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soon as you detect a low r.p.m. condition, immedi-ately apply additional throttle, if available, whileslightly lowering the collective. This reduces mainrotor pitch and drag. As the helicopter begins to set-tle, smoothly raise the collective to stop the descent.At hovering altitude you may have to repeat thistechnique several times to regain normal operatingr.p.m. This technique is sometimes called “milkingthe collective.” When operating at altitude, the col-lective may have to be lowered only once to regainrotor speed. The amount the collective can be low-ered depends on altitude. When hovering near thesurface, make sure the helicopter does not contactthe ground as the collective is lowered.

Since the tail rotor is geared to the main rotor, lowmain rotor r.p.m. may prevent the tail rotor from pro-ducing enough thrust to maintain directional con-trol. If pedal control is lost and the altitude is lowenough that a landing can be accomplished before the turningrate increases dangerously, slowly decrease col-lective pitch, maintain a level attitude with cycliccontrol, and land.

SYSTEM MALFUNCTIONSThe reliability and dependability record of modernhelicopters is very impressive. By following the manufacturer’s recommendations regarding peri-o d i cmaintenance and inspections, you can eliminatemost systems and equipment failures. Most mal-functions or failures can be traced to some erroron the part of the pilot; therefore, most emergen-cies can be averted before they happen. An actualemergency is a rare occurrence.

ANTITORQUE SYSTEM FAILUREAntitorque failures usually fall into two categories.One focuses on failure of the power drive portionof the tail rotor system resulting in a complete lossof antitorque. The other category covers mechan-ical control failures where the pilot is unable tochange or control tail rotor thrust even though thetail rotor may still be providing antitorque thrust.

Tail rotor drive system failures include driveshaftfailures, tail rotor gearbox failures, or a completeloss of the tail rotor itself. In any of these cases,the loss of antitorque normally results in an imme-diate yawing of the helicopter’s nose. The helicop-ter yaws to the right in a counter-clockwise rotorsystem and to the left in a clockwise system. Thisdiscussion assumes a helicopter with a counter-clockwise rotor system.The severity of the yaw is proportionate to theamount of power being used and the airspeed. Ana n t i t o r q u e

failure with a high power setting at a low airspeedresults in a severe yawing to the right. At lowpower settings and high airspeeds, the yaw is lesssevere. High airspeeds tend to streamline the hel-icopter and keep it from spinning.

If a tail rotor failure occurs, power has to be reducedin order to reduce main rotor torque. The tech-n i q u e sdiffer depending on whether the helicopter is inf l i g h tor in a hover, but will ultimately require an autorota-tion. If a complete tail rotor failure occurs while hov-ering, enter a hovering autorotation by rolling off the throttle. If the failure occurs in forward flight, enter a normal autorotation by lowering the collec-t i v eand rolling off the throttle. If the helicopter has enough forward airspeed (close to cruising speed)when the failure occurs, and depending on the hel-icopter design, the vertical stabilizer may provideenough directional control to allow you to maneu-ver the helicopter to a more desirable landing sight.Some of the yaw may be compensated for byapplying slight cyclic control opposite the directionof yaw. This helps in directional control, but also increases drag. Care must betaken not to lose too much forward airspeedbecause the streamlining effect diminishes as air-speed is reduced. Also, more altitude is required toaccelerate to the correct airspeed if an autorotation is entered into ata low airspeed.

A mechanical control failure limits or preventscontrol of tail rotor thrust and is usually causedby a stuck or broken control rod or cable. Whilethe tail rotor is still producing antitorque thrust,

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it cannot be controlled by the pilot. The amountof antitorque depends on the position where thecontrols jam or fail. Once again, the techniquesdiffer depending on the amount of tail rotorthrust, but an autorotation is generally notrequired.

LANDING—STUCK LEFT PEDALBe sure to follow the procedures and techniques outlined in the FAA-approved rotorcraft flightmanual for the helicopter you are flying. A stuckleft pedal, such as might be experienced duringtakeoff or climb conditions, results in the heli -

copter’s nose yawing to the left when power isreduced. Rolling off the throttle and entering anautorotation only makes matters worse. Thelanding profile for a stuck left pedal is bestdescribed as a normal approach to a momentaryhover at three to four feet above the surface. Following an analysis, make the land-ing. If the helicopter is not turning, simply lowert h ehelicopter to the surface. If the helicopter is turn-ing to the right, roll the throttle toward flight idlethe amount necessary to stop the turn as youland. If the helicopter is beginning to turn left,you should be able to make the landing prior tothe turn rate becoming excessive. However, if the turn ratebecomes excessive prior to the landing, simply execute a takeoff and return for another landing.

LANDING—STUCK NEUTRAL OR RIGHT PEDALThe landing profile for a stuck neutral or a stuckright pedal is a low power approach or descentwith a running or roll-on landing. The approach profilecan best be described as a steep approach with a

flare at the bottom to slow the helicopter. Thepower should be low enough to establish a leftyaw during the descent. The left yaw allows a mar-

gin of safety due to the fact that the helicopter willturn to the right when power is applied. This allowsthe momentary use of power at the bottom of theapproach. As you apply power, the helicopterrotates to the right and becomes aligned with thelanding area. At this point, roll the throttle to flightidle and make the landing. The momentary use ofpower helps stop the descent and allows addi-tional time for you to level the helicopter prior toclosing the throttle.

If the helicopter is not yawed to the left at the con-clusion of the flare, roll the throttle to flight idle anduse the collective to cushion the touchdown. As with any running or roll-on landing, use the cyclic to maintainthe ground track. This technique results in a longerground run or roll than if the helicopter was yawedto the left.

UNANTICIPATED YAW / LOSS OF TAILROTOR EFFECTIVENESS (LTE)Unanticipated yaw is the occurrence of an uncom-manded yaw rate that does not subside of its ownaccord and, which, if not corrected, can result inthe loss of helicopter control. This uncommandedyaw rate is referred to as loss of tail rotor effec-tiveness (LTE) and occurs to the right in helicop-ters with a counter-clockwise rotating main rotorand to the left in helicopters with a clockwise mainrotor rotation. Again, this discussion covers a helicopter with a counter-clockwise rotor system and an antitorque rotor.

LTE is not related to an equipment or maintenancemalfunction and may occur in all single-rotor heli-

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copters at airspeeds less than 30 knots. It is theresult of the tail rotor not providing adequate thrustto maintain directional control, and is usuallycaused by either certain wind azimuths (direc-tions) while hovering, or by an insufficient tail rotorthrust for a given power setting at higher altitudes.

For any given main rotor torque setting in perfectlysteady air, there is an exact amount of tail rotorthrust required to prevent the helicopter from yaw-ing either left or right. This is known as tail rotortrim thrust. In order to maintain a constant headingwhile hovering, you should maintain tail rotor thrustequal to trim thrust.

The required tail rotor thrust is modified by theeffects of the wind. The wind can cause anuncommanded yaw by changing tail rotor effectivethrust. Certain relative wind directions are morelikely to cause tail rotor thrust variations than oth-ers. Flight and wind tunnel tests have identifiedthree relative wind azimuth regions that can eithersingularly, or in combination, create an LTE con-ducive environment. These regions can overlap,and thrust variations may be more pronounced.Also, flight testing has determined that the tailrotor does not actually stall during the period.When operating in these areas at less than 30knots, pilot workload increases dramatically.

MAIN ROTOR DISC INTERFERENCE (285-315°)Refer to figure 11-10. Winds at velocities of 10 to30 knots from the left front cause the main rotor vortex to be blown into the tail rotor by the relativewind. The effect of this main rotor disc vortexcauses the tail rotor to operated in an extremelyturbulent environment. During a right turn, the tailrotor experiences a reduction of thrust as it comesinto the area of the main rotor disc vortex. Thereduction in tail rotor thrust comes from the airflowchanges experienced at the tail rotor as the mainrotor disc vortex moves across the tail rotor disc.The effect of the main rotor disc vortex initially increases the angle of attack of the tailrotor blades, thus increasing tail rotor thrust. Theincrease in the angle of attack requires that rightpedal pressure be added to reduce tail rotor thrustin order to maintain the same rate of turn. As themain rotor vortex passes the tail rotor, the tail rotorangle of attack is reduced. The reduction in theangle of attack causes a reduction in thrust and aright yaw acceleration begins. This accelerationcan be surprising, since you were previouslyadding right pedal to maintain the right turn rate.This thrust reduction occurs suddenly, and ifuncorrected, develops into an uncontrollable rapidrotation about the mast. When operating within

this region, be aware that the reduction in tail rotorthrust can happen quite suddenly, and be prepared to react quickly tocounter this reduction with additional left pedalinput.Figure 11-10. Main rotor disc vortex interference.

WEATHERCOCK STABILITY (120-240°)In this region, the helicopter attempts to weather-vane its nose into the relative wind. [Figure 11-11]Unless a resisting pedal input is made, the heli-copter starts a slow, uncommanded turn either tothe right or left depending upon the wind direction.If the pilot allows a right yaw rate to develop andthe tail of the helicopter moves into this region, theyaw rate can accelerate rapidly. In order to avoid the onset of LTE in this downwind condition, it is imperative to maintainpositive control of the yaw rate and devote fullattention to flying the helicopter. Figure 11-11. Weathercock stability.

TAIL ROTOR VORTEX RING STATE (210-330°)Winds within this region cause a tail rotor vortexring state to develop. [Figure 11-12] The result is anon-uniform, unsteady flow into the tail rotor. Thevortex ring state causes tail rotor thrust variations,which result in yaw deviations. The net effect ofthe unsteady flow is an oscillation of tail rotorthrust. Rapid and continuous pedal movementsare necessary to compensate for the rapidchanges in tail rotor thrust when hovering in a leftcrosswind. Maintaining a precise heading in thisregion is difficult, but this characteristic presentsno significant problem unless corrective action isdelayed. However, high pedal workload, lack ofconcentration and overcontrolling can all lead toLTE.

When the tail rotor thrust being generated is lessthan the thrust required, the helicopter yaws to theright. When hovering in left crosswinds, you mustconcentrated on smooth pedal coordination andnot allow an uncontrolled right yaw to develop. If aright yaw rate is allowed to build, the helicopter can rotate intothe wind azimuth region where weathercock sta-bility then accelerates the right turn rate. Pilot workload dur-ing a tail rotor vortex ring state is high. Do notallow a right yaw rate to increase.Figure 11-12. Tail rotor vortex ring state.

LTE AT ALTITUDEAt higher altitudes, where the air is thinner, tailrotor thrust and efficiency is reduced. When oper-

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ating at high altitudes and high gross weights,especially while hovering, the tail rotor thrust maynot be sufficient to maintain directional control andLTE can occur. In this case, the hovering ceiling islimited by tail rotor thrust and not necessarilypower available. In these conditions gross weightsneed to be reduced and/or operations need to be limited to lower density alti-tudes.

REDUCING THE ONSET OF LTETo help reduce the onset of loss of tail rotor effec-tiveness, there are some steps you can follow.

1. Maintain maximum power-on rotor r.p.m. If themain rotor r.p.m. is allowed to decrease, theantitorque thrust available is decreased pro-portionally.

2. Avoid tailwinds below an airspeed of 30knots. If loss of translational lift occurs, itresults in an increased power demand andadditional antitorque pressures.

3. Avoid out of ground effect (OGE) operationsand high power demand situations below anairspeed of 30 knots.

4. Be especially aware of wind direction andvelocity when hovering in winds of about 8-12knots. There are no strong indicators thattranslational lift has been reduced. A loss oftranslational lift results in an unexpected highpower demand and an increased antitorquerequirement.

5. Be aware that if a considerable amount of leftpedal is being maintained, a sufficientamount of left pedal may not be available tocounteract an unanticipated right yaw.

6. Be alert to changing wind conditions, whichmay be experienced when flying along ridgelines and around buildings.

RECOVERY TECHNIQUEIf a sudden unanticipated right yaw occurs, the fol-lowing recovery technique should be performed.Apply full left pedal while simultaneously movingcyclic control forward to increase speed. If altitudepermits, reduce power. As recovery is effected,adjust controls for normal forward flight.

Collective pitch reduction aids in arresting the yawrate but may cause an excessive rate of descent.Any large, rapid increase in collective to preventground or

and decrease rotor r.p.m. The decision to reducecollective must be based on your assessment ofthe altitude available for recovery.

If the rotation cannot be stopped and ground con-tact is imminent, an autorotation may be the bestcourse of action. Maintain full left pedal until therotation stops, then adjust to maintain heading.

MAIN DRIVE SHAFT FAILUREThe main drive shaft, located between the engineand the main rotor gearbox, transmits enginepower to the main rotor gearbox. In some helicop-ters, particularly those with piston engines, a drivebelt is used instead of a drive shaft. A failure of thedrive shaft or belt has the same effect as anengine failure, because power is no longer pro-vided to the main rotor, and an autorotation has tobe initiated. There are a few differences, however, that need to be taken into consideration.If the drive shaft or belt breaks, the lack of anyload on the engine results in an overspeed. In thiscase, the throttle must be closed in order to pre-vent any further damage. In some helicopters, thetail rotor drive system continues to be powered by the engine even if themain drive shaft breaks. In this case, when theengine unloads, a tail rotor overspeed can result.If this happens, close the throttle immediately andenter an autorotation.

HYDRAULIC FAILURESMost helicopters, other than smaller piston pow-ered helicopters, incorporate the use of hydraulicactuators to overcome high control forces. Ahydraulic system consists of actuators, also calledservos, on each flight control; a pump, which isusually driven by the main rotor gearbox; and areservoir to store the hydraulic fluid. A switch inthe cockpit can turn the system off, although it isleft on under normal conditions. A pressure indicator in the cockpit may be installedto monitor the system.

An impending hydraulic failure can be recognizedby a grinding or howling noise from the pump oractuators, increased control forces and feedback,and limited control movement. The corrective action requiredis stated in detail in the appropriate rotorcraft flight manual. However, in most cases, airspeed needsto be reduced in order to reduce control forces.The hydraulic switch and circuit breaker should bechecked and recycled. If hydraulic power is not restored, makea shallow approach to a running or roll-on landing.This technique is used because it requires less

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control force and pilot workload. Additionally, thehydraulic system should be disabled, by eitherpulling the circuit breaker and/or placing theswitch in the off position. The reason for this is to prevent an inadvertentrestoration of hydraulic power, which may lead toovercontrolling near the ground.

In those helicopters where the control forces areso high that they cannot be moved withouthydraulic assistance, two or more independenthydraulic systems may be installed. Some heli-copters use hydraulic accumulators to store pres-sure that can be used for a short time while in anemergency if the hydraulic pump fails. This givesyou enough time to land the helicopter with nor-mal control.

GOVERNOR FAILUREGovernors automatically adjust engine power tomaintain rotor r.p.m. when the collective pitch ischanged. If the governor fails, any change in col-lective pitch requires you to manually adjust thethrottle to maintain correct r.p.m. In the event of ahigh side governor failure, the engine and rotor r.p.m. try to increaseabove the normal range. If the r.p.m. cannot bereduced and controlled with the throttle, close thethrottle and enter an autorotation. If the governorfails on the low side, normal r.p.m. may not beattainable, even if the throttle is manually con-trolled. In this case, the collective has to be low-ered to maintain r.p.m. A running or roll-on landingmay be performed if the engine can maintain suf-ficient rotor r.p.m. If there is insufficient power,enter an autorotation.

ABNORMAL VIBRATIONSWith the many rotating parts found in helicopters,some vibration is inherent. You need to under-stand the cause and effect of helicopter vibrationsbecause abnormal vibrations cause prematurecomponent wear and may even result in structuralfailure. With experience, you learn what vibrationsare normal versus those that are abnormal andcan then decide whether continued flight is safe ornot. Helicopter vibrations are categorized into low,medium, or high frequency.

LOW FREQUENCY VIBRATIONSLow frequency vibrations (100-500 cycles perminute) usually originate from the main rotor sys-tem. The vibration may be felt through the con-trols, the airframe, or a combination of both.Furthermore, the vibration may have a definitedirection of push or thrust. It may be vertical, lat-eral, horizontal, or even a combination. Normally,the direction of the vibration can be determined by

concentrating on the feel of the vibration, whichmay push you up and down, backwards and forwards, or from side to side. The direction of thevibration and whether it is felt in the controls or the airframe is an important means for the mechanic to troubleshoot the source. Some possible causes could be that the main rotor blades are out of trackor balance, damaged blades, worn bearings,dampers out of adjustment, or worn parts.

MEDIUM AND HIGH FREQUENCY VIBRATIONSMedium frequency vibrations (1,000 - 2,000cycles per minute) and high frequency vibrations(2,000 cycles per minute or higher) are normallyassociated with out-of-balance components thatrotate at a high r.p.m., such as the tail rotor,engine, cooling fans, and components of the drivetrain, including transmissions, drive shafts, bear-ings, pulleys, and belts. Most tail rotor vibrationscan be felt through the tail rotor pedals as long asthere are no hydraulic actuators, which usuallydampen out the vibration. Any imbalance in thetail rotor system is very harmful, as it can causecracks to develop and rivets to work loose. Piston engines usually pro-duce a normal amount of high frequency vibration,which is aggravated by engine malfunctions suchas spark plug fouling, incorrect magneto timing,carburetor icing and/or incorrect fuel/air mixture.Vibrations in turbine engines are often difficult todetect as these engines operate at a very highr.p.m.

TRACKING AND BALANCEModern equipment used for tracking and balanc-ing the main and tail rotor blades can also be usedto detect other vibrations in the helicopter. Thesesystems use accelerometers mounted around thehelicopter to detect the direction, frequency, andintensity of the vibration. The built-in software canthen analyze the information, pinpoint the origin ofthe vibration, and suggest the corrective action.

FLIGHT DIVERSIONThere will probably come a time in your flight careerwhen you will not be able to make it to your destina-tion. This can be the result of unpredictable weatherconditions, a system malfunction, or poor preflightplanning. In any case, you will need to be able tosafely and efficiently divert to an alternate destina-tion. Before any cross-country flight, check the charts for airports or suitablelanding areas along or near your route of flight. Also,check for navaids that can be used during a diver-sion.

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Attitude instrument flying in helicopters is essen-tially visual flying with the flight instruments substi-tuted for the various reference points on thehelicopter and the natural horizon. Controlchanges, required to produce a given attitude byreference to instruments, are identical to thoseused in helicopter VFR flight, and your thoughtprocesses are the same. Basic instrument trainingis intended as a building block towards attainingan instrument rating. It will also enable you to do a180° turn in case of inadvertent incursion intoinstrument meteorological conditions (IMC).

FLIGHT INSTRUMENTSWhen flying a helicopter with reference to the flightinstruments, proper instrument interpretation is thebasis for aircraft control. Your skill, in part, dependson your understanding of how a particular instru-ment or system functions, including its indicationsand limitations. With this knowledge, you canquickly determine what an instrument is telling youand translate that information into a controlresponse.

PITOT-STATIC INSTRUMENTSThe pitot-static instruments, which include the air-speed indicator, altimeter, and vertical speed indi-cator, operate on the principle of differential airpressure. Pitot pressure, also called impact, ram,or dynamic pressure, is directed only to the air-speed indicator, while static pressure, or ambientpressure, is directed to all three instruments. Analternate static source may be included allowingyou to select an alternate source of ambient pres-sure in the event the main port becomes blocked.[Figure 12-1]

AIRSPEED INDICATORThe airspeed indicator displays the speed of thehelicopter through the air by comparing ram airpressure from the pitot tube with static air pres-sure from the static port—the greater the differen-tial, the greater the speed. The instrumentdisplays the result of this pressure differential asindicated airspeed (IAS). Manufacturers use thisspeed as the basis for determining helicopter per-formance, and it may be displayed in knots, miles

per hour, or both. [Figure 12-2] When an indicatedairspeed is given for a particular situation, you nor-mally use that speed without making a correctionfor altitude or temperature. The reason no correc-tion is needed is that an airspeed indicator and air-

craft performance are affected equally by changesin air density. An indicated airspeed always yieldsthe same performance because the indicator has, in fact,compensated for the change in the environment.

Figure 12-1. Ram air pressure is supplied only to the airspeedindicator, while static pressure is used by all three instruments.Electrical heating elements may be installed to prevent ice fromforming on the pitot tube. A drain opening to remove moisture isnormally included.

Figure 12-2. Ram air pressure from the pitot tube is directed to adiaphragm inside the airspeed indicator. The airtight case isvented to the static port. As the diaphragm expands or contracts,a mechanical linkage moves the needle on the face of the indica-tor.

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INSTRUMENT CHECK—During the preflight, ensurethat the pitot tube, drain hole, and static ports areunobstructed. Before liftoff, make sure the air-speed indicator is reading zero. If there is a strongwind blowing directly at the helicopter, the airspeedindicator may read higher than zero, dependingon the wind speed and direction. As you beginyour takeoff, make sure the airspeed indicator isincreasing at an appropriate rate. Keep in mind,however, that the airspeed indication might be

unreliable below a certain airspeed due to rotordownwash.

ALTIMETERThe altimeter displays altitude in feet by sensingpressure changes in the atmosphere. There is anadjustable barometric scale to compensate forchanges in atmospheric pressure. [Figure 12-3]

The basis for altimeter calibration is theInternational Standard Atmosphere (ISA), wherepressure, temperature, and lapse rates have stan-dard values. However, actual atmospheric condi-tions seldom match the standard values. Inaddition, local pressure readings within a givenarea normally change over a period of time, andpressure frequently changes as you fly from onearea to another. As a result, altimeter indicationsare subject to errors, the extent of which dependson how much the pressure, temperature, andlapse rates deviate from standard, as well as how

recently you have set the altimeter. The best wayto minimize altimeter errors is to update the altime-ter setting frequently. In most cases, use the cur-rent altimeter setting of the nearest reportingstation along your route of flight per regulatoryrequirements.

INSTRUMENT CHECK—During the preflight, ensurethat the static ports are unobstructed. Before lift-off, set the altimeter to the current setting. If thealtimeter indicates within 75 feet of the actual ele-vation, the altimeter is generally consideredacceptable for use.

VERTICAL SPEED INDICATORThe vertical speed indicator (VSI) displays the rateof climb or descent in feet per minute (f.p.m.) bymeasuring how fast the ambient air pressureincreases or decreases as the helicopter changesaltitude. Since the VSI measures only the rate atwhich air pressure changes, air temperature hasno effect on this instrument. [Figure 12-4]There is a lag associated with the reading on theVSI, and it may take a few seconds to stabilizewhen showing rate of climb or descent. Roughcontrol technique and turbulence can furtherextend the lag period and cause erratic and unsta-ble rate indications. Some aircraft are equippedwith an instantaneous vertical speed indicator(IVSI), which incorporates accelerometers to com-pensate for the lag found in the typical VSI.

Figure 12-3. The main component of the altimeter is a stack of sealedaneroid wafers. They expand and contract as atmospheric pressurefrom the static source changes. The mechanical linkage translatesthese changes into pointer movements on the indicator.

Figure 12-4. Although the sealed case and diaphragm are bothconnected to the static port, the air inside the case is restrictedthrough a calibrated leak. When the pressures are equal, the nee-dle reads zero. As you climb or descend, the pressure inside thediaphragm instantly changes, and the needle registers a changein vertical direction. When the pressure differential stabilizes at adefinite ratio, the needle registers the rate of altitude change.

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INSTRUMENT CHECK—During the preflight, ensurethat the static ports are unobstructed. Check to seethat the VSI is indicating zero before lift-off. Duringtakeoff, check for a positive rate of climb indication.

SYSTEM ERRORSThe pitot-static system and associated instrumentsare usually very reliable. Errors are generallycaused when the pitot or static openings areblocked. This may be caused by dirt, ice formation,or insects. Check the pitot and static openings forobstructions during the preflight. It is also advisableto place covers on the pitot and static ports whenthe helicopter is parked on the ground.

The airspeed indicator is the only instrument affectedby a blocked pitot tube. The system can becomeclogged in two ways. If the ram air inlet is clogged,but the drain hole remains open, the airspeed indica-tor registers zero, regardless of airspeed. If both theram air inlet and the drain hole become blocked,pressure in the line is trapped, and the airspeed indi-cator reacts like an altimeter, showing an increase inairspeed with an increase in altitude, and a decreasein speed as altitude decreases. This occurs as longas the static port remains unobstructed.

If the static port alone becomes blocked, the air-speed indicator continues to function, but withincorrect readings. When you are operating abovethe altitude where the static port became clogged,the airspeed indicator reads lower than it should.Conversely, when operating below that altitude,the indicator reads higher than the correct value.The amount of error is proportional to the distancefrom the altitude where the static system becameblocked. The greater the difference, the greaterthe error. With a blocked static system, the altime-ter freezes at the last altitude and the VSI freezesat zero. Both instruments are then unusable.

Some helicopters are equipped with an alternatestatic source, which may be selected in the eventthat the main static system becomes blocked. Thealternate source generally vents into the cabin,where air pressures are slightly different than out-side pressures, so the airspeed and altimeter usu-ally read higher than normal. Correction charts maybe supplied in the flight manual.

GYROSCOPIC INSTRUMENTSThe three gyroscopic instruments that arerequired for instrument flight are the attitude indi-cator, heading indicator, and turn indicator. Wheninstalled in helicopters, these instruments are usu-ally electrically powered.

Gyros are affected by two principles—rigidity in spaceand precession. Rigidity in space means that once agyro is spinning, it tends to remain in a fixed positionand resists external forces applied to it. This principleallows a gyro to be used to measure changes in atti-tude or direction.

Precession is the tilting or turning of a gyro inresponse to pressure. The reaction to this pressuredoes not occur at the point where it was applied;rather, it occurs at a point that is 90° later in thedirection of rotation from where the pressure wasapplied. This principle allows the gyro to determine

Figure 12-5. The gyro in the attitude indicator spins in the hori-zontal plane. Two mountings, or gimbals, are used so that bothpitch and roll can be sensed simultaneously. Due to rigidity inspace, the gyro remains in a fixed position relative to the horizonas the case and helicopter rotate around it.

Figure 12-6. A heading indicator displays headings based on a360° azimuth, with the final zero omitted. For example, a 6 repre-sents 060°, while a 21 indicates 210°. The adjustment knob isused to align the heading indicator with the magnetic compass.

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a rate of turn by sensing the amount of pressurecreated by a change in direction. Precession canalso create some minor errors in some instruments.

ATTITUDE INDICATORThe attitude indicator provides a substitute for thenatural horizon. It is the only instrument that pro-vides an immediate and direct indication of thehelicopter’s pitch and bank attitude. Since mostattitude indicators installed in helicopters are elec-trically powered, there may be a separate powerswitch, as well as a warning flag within the instru-ment, that indicates a loss of power. A caging or“quick erect” knob may be included, so you canstabilize the spin axis if the gyro has tumbled.[Figure 12-5]

HEADING INDICATORThe heading indicator, which is sometimesreferred to as a directional gyro (DG), sensesmovement around the vertical axis and provides amore accurate heading reference compared to amagnetic compass, which has a number of turn-ing errors. [Figure 12-6].

Due to internal friction within the gyroscope, pre-cession is common in heading indicators.Precession causes the selected heading to driftfrom the set value. Some heading indicatorsreceive a magnetic north reference from a remotesource and generally need no adjustment.

Heading indicators that do not have this automaticnorth-seeking capability are often called “free”gyros, and require that you periodically adjustthem. You should align the heading indicator withthe magnetic compass before flight and check it at15-minute intervals during flight. When you do anin-flight alignment, be certain you are in straight-

and-level, unaccelerated flight, with the magneticcompass showing a steady indication.

TURN INDICATORSTurn indicators show the direction and the rate ofturn. A standard rate turn is 3° per second, and atthis rate you will complete a 360° turn in two min-utes. A half-standard rate turn is 1.5° per second.Two types of indicators are used to display thisinformation. The turn-and-slip indicator uses aneedle to indicate direction and turn rate. Whenthe needle is aligned with the white markings,called the turn index, you are in a standard rateturn. A half-standard rate turn is indicated whenthe needle is halfway between the indexes. Theturn-and-slip indicator does not indicate roll rate.The turn coordinator is similar to the turn-and-slipindicator, but the gyro is canted, which allows it tosense roll rate in addition to rate of turn. The turncoordinator uses a miniature aircraft to indicatedirection, as well as the turn and roll rate. [Figure12-7]

Another part of both the turn coordinator and theturn-and-slip indicator is the inclinometer. Theposition of the ball defines whether the turn iscoordinated or not. The helicopter is either slip-ping or skidding anytime the ball is not centered,and usually requires an adjustment of the anti -torque pedals or angle of bank to correct it.[Figure 12-8]

INSTRUMENT CHECK—During your preflight, checkto see that the inclinometer is full of fluid and has

Figure 12-7. The gyros in both the turn-and-slip indicator and theturn coordinator are mounted so that they rotate in a vertical plane.The gimbal in the turn coordinator is set at an angle, or canted, whichmeans precession allows the gyro to sense both rate of roll and rateof turn. The gimbal in the turn-and-slip indicator is horizontal. In thiscase, precession allows the gyro to sense only rate of turn. Whenthe needle or miniature aircraft is aligned with the turn index, you arein a standard-rate turn.

Figure 12-8. In a coordinated turn (instrument 1), the ball is cen-tered. In a skid (instrument 2), the rate of turn is too great for theangle of bank, and the ball moves to the outside of the turn.Conversely, in a slip (instrument 3), the rate of turn is too small forthe angle of bank, and the ball moves to the inside of the turn.

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no air bubbles. The ball should also be resting atits lowest point. Since almost all gyroscopic instru-ments installed in a helicopter are electricallydriven, check to see that the power indicators aredisplaying off indications. Turn the master switchon and listen to the gyros spool up. There shouldbe no abnormal sounds, such as a grindingsound, and the power out indicator flags shouldnot be displayed. After engine start and beforeliftoff, set the direction indicator to the magneticcompass. During hover turns, check the heading

indicator for proper operation and ensure that ithas not precessed significantly. The turn indicatorshould also indicate a turn in the correct direction.During takeoff, check the attitude indicator forproper indication and recheck it during the firstturn.

MAGNETIC COMPASSIn some helicopters, the magnetic compass is theonly direction seeking instrument. Although thecompass appears to move, it is actually mountedin such a way that the helicopter turns about thecompass card as the card maintains its alignmentwith magnetic north.

COMPASS ERRORSThe magnetic compass can only give you reliabledirectional information if you understand its limita-tions and inherent errors. These include magneticvariation, compass deviation, and magnetic dip.

MAGNETIC VARIATIONWhen you fly under visual flight rules, you ordi-narily navigate by referring to charts, which are

oriented to true north. Because the aircraft com-pass is oriented to magnetic north, you mustmake allowances for the difference betweenthese poles in order to navigate properly. You dothis by applying a correction called variation toconvert a true direction to a magnet direction.Variation at a given point is the angular differencebetween the true and magnetic poles. Theamount of variation depends on where you arelocated on the earth’s surface. Isogonic lines con-nect points where the variation is equal, while theagonic line defines the points where the variationis zero. [Figure 12-9]

COMPASS DEVIATIONBesides the magnetic fields generated by theearth, other magnetic fields are produced by metaland electrical accessories within the helicopter.These magnetic fields distort the earth’s magnetforce and cause the compass to swing away fromthe correct heading. Manufacturers often installcompensating magnets within the compass hous-ing to reduce the effects of deviation. These mag-nets are usually adjusted while the engine isrunning and all electrical equipment is operating.Deviation error, however, cannot be completelyeliminated; therefore, a compass correction card ismounted near the compass. The compass correc-tion card corrects for deviation that occurs fromone heading to the next as the lines of force inter-act at different angles.

MAGNETIC DIPMagnetic dip is the result of the vertical compo-nent of the earth’s magnetic field. This dip is virtu-ally non-existent at the magnetic equator, sincethe lines of force are parallel to the earth’s surfaceand the vertical component is minimal. As youmove a compass toward the poles, the verticalcomponent increases, and magnetic dip becomesmore apparent at these higher latitudes. Magneticdip is responsible for compass errors during accel-eration, deceleration, and turns.

Acceleration and deceleration errors are fluctua-tions in the compass during changes in speed. Inthe northern hemisphere, the compass swingstoward the north during acceleration and towardthe south during deceleration. When the speedstabilizes, the compass returns to an accurateindication. This error is most pronounced whenyou are flying on a heading of east or west, anddecreases gradually as you fly closer to a northor south heading. The error does not occur whenyou are flying directly north or south. The mem-ory aid, ANDS (Accelerate North, DecelerateSouth) may help you recall this error. In the

Figure 12-9. Variation at point A in the western United States is17°. Since the magnetic north pole is located to the east of thetrue north pole in relation to this point, the variation is easterly.When the magnetic pole falls to the west of the true north pole,variation is westerly.

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southern hemisphere, this error occurs in theopposite direction.

Turning errors are most apparent when you areturning to or from a heading of north or south. Thiserror increases as you near the poles as magneticdip becomes more apparent. There is no turningerror when flying near the magnetic equator. In thenorthern hemisphere, when you make a turn froma northerly heading, the compass gives an initialindication of a turn in the opposite direction. It thenbegins to show the turn in the proper direction, butlags behind the actual heading. The amount of lagdecreases as the turn continues, then disappearsas the helicopter reaches a heading of east orwest. When you make a turn from a southerlyheading, the compass gives an indication of a turnin the correct direction, but leads the actual head-ing. This error also disappears as the helicopterapproaches an east or west heading.

INSTRUMENT CHECK—Prior to flight, make surethat the compass is full of fluid. During hover turns,the compass should swing freely and indicateknown headings. Since that magnetic compass isrequired for all flight operations, the aircraft shouldnever be flown with a faulty compass.

INSTRUMENT FLIGHTTo achieve smooth, positive control of the heli-copter during instrument flight, you need todevelop three fundamental skills. They are instru-

ment cross-check, instrument interpretation, andaircraft control.

INSTRUMENT CROSS-CHECKCross-checking, sometimes referred to as scan-ning, is the continuous and logical observation ofinstruments for attitude and performance informa-tion. In attitude instrument flying, an attitude ismaintained by reference to the instruments, whichproduces the desired result in performance. Due tohuman error, instrument error, and helicopter per-formance differences in various atmospheric andloading conditions, it is difficult to establish an attitude and have performance remain constant for a long period of time. These variablesmake it necessary for you to constantly check theinstruments and make appropriate changes in thehelicopter’s attitude. The actual technique mayvary depending on what instruments are installedand where they are installed, as well as your expe-rience and proficiency level. For this discussion,we will concentrate on the six basic flight instru-ments discussed earlier. [Figure 12-10]

At first, you may have a tendency to cross-check rapidly, looking directly at the instruments withoutknowing exactly what information you are seek-ing. However, with familiarity and practice, theinstrument cross-check reveals definite trendsduring specific flight conditions. These trends helpyou control the

Figure 12-10. In most situations, the cross-check pattern includes the attitude indicator between the cross-check of each of the otherinstruments. A typical cross-check might progress as follows: attitude indicator, altimeter, attitude indicator, VSI, attitude indicator, head-ing indicator, attitude indicator, and so on.

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helicopter as it makes a transition from one flight condition to another.

If you apply your full concentration to a single instru-ment, you will encounter a problem called “fixation.”This results from a natural human inclination toobserve a specific instrument carefully and accurately,often to the exclusion of other instruments. Fixation ona single instrument usually results in poor control. Forexample, while performing a turn, you may have a ten-dency to watch only the turn-and-slip indicator insteadof including other instruments in your cross-check.This fixation on the turn-and-slip indicator often leadsto a loss of altitude through poor pitch and bank con-trol. You should look at each instrument only longenough to understand the information it presents, thencontinue on to the next one. Similarly, you may findyourself placing too much “emphasis” on a singleinstrument, instead of relying on a combination ofinstruments necessary for helicopter performanceinformation. This differs from fixation in that you areusing other instruments, but are giving too muchattention to a particular one.

During performance of a maneuver, you may some-times fail to anticipate significant instrument indi-cations following attitude changes. For example,during leveloff from a climb or descent, you mayconcentrate on pitch control, while forgettingabout heading or roll information. This error, called“omission,” results in erratic control of headingand bank.

In spite of these common errors, most pilots canadapt well to flight by instrument reference afterinstruction and practice. You may find that you cancontrol the helicopter more easily and precisely byinstruments.

INSTRUMENT INTERPRETATIONThe flight instruments together give a picture ofwhat is going on. No one instrument is moreimportant than the next; however, during certainmaneuvers or conditions, those instruments thatprovide the most pertinent and useful informationare termed primary instruments. Those whichback up and supplement the primary instrumentsare termed supporting instruments. For example,since the attitude indicator is the only instrumentthat provides instant and direct aircraft attitudeinformation, it should be considered primary dur-ing any change in pitch or bank attitude. After thenew attitude is established, other instrumentsbecome primary, and the attitude indicator usuallybecomes the supporting instrument.

AIRCRAFT CONTROL Controlling the helicopter is the result of accu-rately interpreting the flight instruments and trans-lating these readings into correct controlresponses. Aircraft control involves adjustment topitch, bank, power, and trim in order to achieve adesired flight path.

Figure 12-11. The flight instruments for pitch control are the airspeed indicator, attitude indicator, altimeter, and vertical speed indica-tor.

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Pitch attitude control is controlling the movementof the helicopter about its lateral axis. After inter-preting the helicopter’s pitch attitude by referenceto the pitch instruments (attitude indicator, altime-ter, airspeed indicator, and vertical speed indica-tor), cyclic control adjustments are made to affectthe desired pitch attitude. In this chapter, the pitchattitudes illustrated are approximate and will varywith different helicopters.

Bank attitude control is controlling the angle madeby the lateral tilt of the rotor and the natural hori-zon, or, the movement of the helicopter about itslongitudinal axis. After interpreting the helicopter’sbank instruments (attitude indicator, heading indi-cator, and turn indicator), cyclic control adjust-ments are made to attain the desired bankattitude.

Power control is the application of collective pitchwith corresponding throttle control, where applica-ble. In straight-and-level flight, changes of collec-tive pitch are made to correct for altitudedeviations if the error is more than 100 feet, or theairspeed is off by more than 10 knots. If the erroris less than that amount, use a slight cyclic climbor descent.

In order to fly a helicopter by reference to theinstruments, you should know the approximatepower settings required for your particular heli-copter in various load configurations and flightconditions.

Trim, in helicopters, refers to the use of the cycliccentering button, if the helicopter is so equipped, torelieve all possible cyclic pressures. Trim also refersto the use of pedal adjustment to center the ball ofthe turn indicator. Pedal trim is required during allpower changes.

The proper adjustment of collective pitch andcyclic friction helps you relax during instrumentflight. Friction should be adjusted to minimizeovercontrolling and to prevent creeping, but notapplied to such a degree that control movement islimited. In addition, many helicopters equipped forinstrument flight contain stability augmentationsystems or an autopilot to help relieve pilot work-load.

STRAIGHT-AND-LEVEL FLIGHTStraight-and-level unaccelerated flight consists ofmaintaining the desired altitude, heading, air-speed, and pedal trim.

PITCH CONTROLThe pitch attitude of a helicopter is the angularrelation of its longitudinal axis and the natural hori-zon. If available, the attitude indicator is used toestablish the desired pitch attitude. In level flight,pitch attitude varies with airspeed and center ofgravity. At a constant altitude and a stabilized air-speed, the pitch attitude is approximately level.[Figure 12-11]

ATTITUDE INDICATORThe attitude indicator gives a direct indication ofthe pitch attitude of the helicopter. In visual flight,you attain the desired pitch attitude by using thecyclic to raise and lower the nose of the helicopterin relation to the natural horizon. During instru-ment flight, you follow exactly the same procedurein raising or lowering the miniature aircraft in rela-tion to the horizon bar.

You may note some delay between control appli-cation and resultant instrument change. This is thenormal control lag in the helicopter and should notbe confused with instrument lag. The attitude indi-cator may show small misrepresentations of pitchattitude during maneuvers involving acceleration,deceleration, or turns. This precession error canbe detected quickly by cross-checking the otherpitch instruments.

If the miniature aircraft is properly adjusted on theground, it may not require readjustment in flight. Ifthe miniature aircraft is not on the horizon bar afterleveloff at normal cruising airspeed, adjust it asnecessary while maintaining level flight with theother pitch instruments. Once the miniature air-craft has been adjusted in level flight at normal

Figure 12-12. The initial pitch correction at normal cruise is onebar width.

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cruising airspeed, leave it unchanged so it willgive an accurate picture of pitch attitude at alltimes.

When making initial pitch attitude corrections tomaintain altitude, the changes of attitude shouldbe small and smoothly applied. The initial move-ment of the horizon bar should not exceed one barwidth high or low. [Figure 12-12] If a furtherchange is required, an additional correction ofone-half bar normally corrects any deviation fromthe desired altitude. This one and one-half bar cor-rection is normally the maximum pitch attitude cor-rection from level flight attitude. After you havemade the correction, cross-check the other pitchinstruments to determine whether the pitch atti-tude change is sufficient. If more correction isneeded to return to altitude, or if the airspeedvaries more than 10 knots from that desired,adjust the power.

ALTIMETERThe altimeter gives an indirect indication of thepitch attitude of the helicopter in straight-and-levelflight. Since the altitude should remain constant inlevel flight, deviation from the desired altitudeshows a need for a change in pitch attitude, and ifnecessary, power. When losing altitude, raise thepitch attitude and, if necessary, add power. Whengaining altitude, lower the pitch attitude and, ifnecessary, reduce power.

The rate at which the altimeter moves helps indetermining pitch attitude. A very slow movementof the altimeter indicates a small deviation fromthe desired pitch attitude, while a fast movementof the altimeter indicates a large deviation fromthe desired pitch attitude. Make any correctiveaction promptly, with small control changes. Also,remember that movement of the altimeter shouldalways be corrected by two distinct changes. Thefirst is a change of attitude to stop the altimeter;and the second, a change of attitude to returnsmoothly to the desired altitude. If the altitudeand airspeed are more than 100 feet and 10knots low, respectively, apply power along withan increase of pitch attitude. If the altitude andairspeed are high by more than 100 feet and 10knots, reduce power and lower the pitch attitude.

There is a small lag in the movement of the altime-ter; however, for all practical purposes, considerthat the altimeter gives an immediate indication ofa change, or a need for change in pitch attitude.

Since the altimeter provides the most pertinentinformation regarding pitch in level flight, it is con-sidered primary for pitch.

VERTICAL SPEED INDICATORThe vertical speed indicator gives an indirect indi-cation of the pitch attitude of the helicopter andshould be used in conjunction with the other pitchinstruments to attain a high degree of accuracy

Figure 12-13. The flight instruments used for bank control are the attitude, heading, and turn indicators.

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and precision. The instrument indicates zero whenin level flight. Any movement of the needle fromthe zero position shows a need for an immediatechange in pitch attitude to return it to zero. Alwaysuse the vertical speed indicator in conjunction withthe altimeter in level flight. If a movement of thevertical speed indicator is detected, immediatelyuse the proper corrective measures to return it tozero. If the correction is made promptly, there isusually little or no change in altitude. If you do notzero the needle of the vertical speed indicatorimmediately, the results will show on the altimeteras a gain or loss of altitude.

The initial movement of the vertical speed nee-dle is instantaneous and indicates the trend ofthe vertical movement of the helicopter. It mustbe realized that a period of time is necessary

for the vertical speed indicator to reach its max-imum point of deflection after a correction hasbeen made. This time element is commonlyreferred to as “lag.” The lag is directly propor-tional to the speed and magnitude of the pitchchange. If you employ smooth control tech-niques and make small adjustments in pitchattitude, lag is minimized, and the verticalspeed indicator is easy to interpret.Overcontrolling can be minimized by first neu-tralizing the controls and allowing the pitch atti-tude to stabilize; then readjusting the pitch

attitude by noting the indications of the otherpitch instruments.

Occasionally, the vertical speed indicator may beslightly out of calibration. This could result in theinstrument indicating a slight climb or descenteven when the helicopter is in level flight. If it can-not be readjusted properly, this error must betaken into consideration when using the verticalspeed indicator for pitch control. For example, ifthe vertical speed indicator showed a descent of100 f.p.m. when the helicopter was in level flight,you would have to use that indication as levelflight. Any deviation from that reading would indi-cate a change in attitude.

AIRSPEED INDICATORThe airspeed indicator gives an indirect indicationof helicopter pitch attitude. With a given powersetting and pitch attitude, the airspeed remainsconstant. If the airspeed increases, the nose is toolow and should be raised. If the airspeeddecreases, the nose is too high and should belowered. A rapid change in airspeed indicates alarge change in pitch attitude, and a slow changein airspeed indicates a small change in pitch atti-tude. There is very little lag in the indications ofthe airspeed indicator. If, while making attitudechanges, you notice some lag between controlapplication and change of airspeed, it is mostlikely due to cyclic control lag. Generally, a depar-ture from the desired airspeed, due to an inadver-tent pitch attitude change, also results in a changein altitude. For example, an increase in airspeeddue to a low pitch attitude results in a decrease inaltitude. A correction in the pitch attitude regainsboth airspeed and altitude.

BANK CONTROLThe bank attitude of a helicopter is the angularrelation of its lateral axis and the natural horizon.To maintain a straight course in visual flight, youmust keep the lateral axis of the helicopter level with the naturalhorizon. Assuming the helicopter is in coordinatedflight, any deviation from a laterally level attitudeproduces a turn. [Figure 12-13]

ATTITUDE INDICATORThe attitude indicator gives a direct indication ofthe bank attitude of the helicopter. For instrumentflight, the miniature aircraft and the horizon bar ofthe attitude indicator are substituted for the actualhelicopter and the natural horizon. Any change inbank attitude of the helicopter is indicated instantlyby the miniature aircraft. For proper interpretationsof this instrument, you should imagine being in theminiature aircraft. If the helicopter is properly

Figure 12-14. The banking scale at the top of the attitude indicatorindicates varying degrees of bank. In this example, the helicopteris banked a little over 10° to the right.

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trimmed and the rotor tilts, a turn begins. The turncan be stopped by leveling the miniature aircraft withthe horizon bar. The ball in the turn-and-slip indica-tor should always be kept centered through properpedal trim.

The angle of bank is indicated by the pointer onthe banking scale at the top of the instrument.[Figure 12-14] Small bank angles, which may notbe seen by observing the miniature aircraft, caneasily be determined by referring to the bankingscale pointer.

Pitch and bank attitudes can be determined simulta-neously on the attitude indicator. Even though theminiature aircraft is not level with the horizon bar,pitch attitude can be established by observing therelative position of the miniature aircraft and thehorizon bar.

The attitude indicator may show small misrepre-sentations of bank attitude during maneuversthat involve turns. This precession error can beimmediately detected by closely cross-checkingthe other bank instruments during these maneu-vers. Precession normally is noticed when rollingout of a turn. If, on the completion of a turn, theminiature aircraft is level and the helicopter is stillturning, make a small change of bank attitude tocenter the turn needle and stop the movement ofthe heading indicator.

HEADING INDICATORIn coordinated flight, the heading indicator givesan indirect indication of the helicopter’s bank atti-tude. When a helicopter is banked, it turns. Whenthe lateral axis of the helicopter is level, it fliesstraight. Therefore, in coordinated flight, when theheading indicator shows a constant heading, thehelicopter is level laterally. A deviation from thedesired heading indicates a bank in the directionthe helicopter is turning. A small angle of bank isindicated by a slow change of heading; a largeangle of bank is indicated by a rapid change ofheading. If a turn is noticed, apply opposite cyclicuntil the heading indicator indicates the desiredheading, simultaneously checking that the ball iscentered. When making the correction to thedesired heading, you should not use a bank anglegreater than that required to achieve a standardrate turn. In addition, if the number of degrees ofchange is small, limit the bank angle to the num-ber of degrees to be turned. Bank angles greaterthan these require more skill and precision inattaining the desired results. During straight-and-level flight, the heading indicator is the primaryreference for bank control.

TURN INDICATORDuring coordinated flight, the needle of the turn-and-slip indicator gives an indirect indication ofthe bank attitude of the helicopter. When theneedle is displaced from the vertical position,the helicopter is turning in the direction of thedisplacement. Thus, if the needle is displaced tothe left, the helicopter is turning left. Bringing theneedle back to the vertical position with thecyclic produces straight flight. A close observa-tion of the needle is necessary to accuratelyinterpret small deviations from the desired posi-tion.

Cross-check the ball of the turn-and-slip indicatorto determine that the helicopter is in coordinatedflight. If the rotor is laterally level and torque isproperly compensated for by pedal pressure, theball remains in the center. To center the ball, levelthe helicopter laterally by reference to the otherbank instruments, then center the ball with pedaltrim. Torque correction pressures vary as youmake power changes. Always check the ball fol-lowing such changes.

COMMON ERRORS DURING STRAIGHT-AND-LEVEL FLIGHT1. Failure to maintain altitude.2. Failure to maintain heading.3. Overcontrolling pitch and bank during correc-

tions.4. Failure to maintain proper pedal trim.5. Failure to cross-check all available instru-

ments.

POWER CONTROL DURING STRAIGHT-AND-LEVEL FLIGHTEstablishing specific power settings is accom-plished through collective pitch adjustments andt h r o t t l econtrol, where necessary. For reciprocating pow-ered helicopters, power indications are observedon the manifold pressure gauge. For turbine powered hel-icopters, power is observed on the torque gauge.(Since most IFR certified helicopters are turbinepowered, this discussion concentrates on this type of helicopter.)

At any given airspeed, a specific power settingdetermines whether the helicopter is in level flight,in a climb, or in a descent. For example, cruisingairspeed maintained with cruising power results inlevel flight. If you increase the power setting andhold the airspeed constant, the helicopter climbs.Conversely, if you decrease power and hold theairspeed constant, the helicopter descends. As arule of thumb, in a turbine-engine powered heli-

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copter, a 10 to 15 percent change in the torquevalue required to maintain level flight results in aclimb or descent of approximately 500 f.p.m., if theairspeed remains the same.

If the altitude is held constant, power determinesthe airspeed. For example, at a constant altitude,cruising power results in cruising airspeed. Anydeviation from the cruising power setting results in

a change of airspeed. When power is added toincrease airspeed, the nose of the helicopterpitches up and yaws to the right in a helicopterwith a counterclockwise main rotor blade rotation.When power is reduced to decrease airspeed, thenose pitches down and yaws to the left. The yaw-ing effect is most pronounced in single-rotor heli-copters, and is absent in helicopters withcounter-rotating rotors. To counteract the yawing

Figure 12-16. Flight instrument indications in straight-and-level flight with airspeed decreasing.

Figure 12-15. Flight instrument indications in straight-and-level flight at normal cruise speed.

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tendency of the helicopter, apply pedal trim duringpower changes.

To maintain a constant altitude and airspeed inlevel flight, coordinate pitch attitude and power

control. The relationship between altitude and air-speed determines the need for a change in powerand/or pitch attitude. If the altitude is constant andthe airspeed is high or low, change the power toobtain the desired airspeed. During the change in

Figure 12-17. Flight instrument indications during climb entry for a constant airspeed climb.

Figure 12-18. Flight instrument indications in a stabilized, constant airspeed climb.

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power, make an accurate interpretation of thealtimeter; then counteract any deviation from thedesired altitude by an appropriate change of pitchattitude. If the altitude is low and the airspeed ishigh, or vice versa, a change in pitch attitudealone may return the helicopter to the proper alti-tude and airspeed. If both airspeed and altitudeare low, or if both are high, a change in bothpower and pitch attitude is necessary.

To make power control easy when changing air-speed, it is necessary to know the approximatepower settings for the various airspeeds that will beflown. When the airspeed is to be changed anyappreciable amount, adjust the torque so that it isapproximately five percent over or under that settingnecessary to maintain the new airspeed. As thepower approaches the desired setting, include thetorque meter in the cross-check to determine whenthe proper adjustment has been accomplished. Asthe airspeed is changing, adjust the pitch attitude tomaintain a constant altitude. A constant headingshould be maintained throughout the change. As thedesired airspeed is approached, adjust power to thenew cruising power setting and further adjust pitchattitude to maintain altitude. Overpowering andunderpowering torque approximately five percentresults in a change of airspeed at a moderate rate,which allows ample time to adjust pitch and banksmoothly. The instrument indications for straight-and-level flight at normal cruise, and during the tran-sition from normal cruise to slow cruise areillustrated in figures 12-15 and 12-16 on the next

page. After the airspeed has stabilized at slowcruise, the attitude indicator shows an approximatelevel pitch attitude.

The altimeter is the primary pitch instrument dur-ing level flight, whether flying at a constant air-speed, or during a change in airspeed. Altitudeshould not change during airspeed transitions.The heading indicator remains the primary bankinstrument. Whenever the airspeed is changedany appreciable amount, the torque meter ismomentarily the primary instrument for powercontrol. When the airspeed approaches thatdesired, the airspeed indicator again becomes theprimary instrument for power control.

The cross-check of the pitch and bank instrumentsto produce straight-and-level flight should be com-bined with the power control instruments. With aconstant power setting, a normal cross-checkshould be satisfactory. When changing power, the speed ofthe cross-check must be increased to cover thepitch and bank instruments adequately. This isnecessary to counteract any deviations immediately.

COMMON ERRORS DURING AIRSPEED CHANGES1. Improper use of power.2. Overcontrolling pitch attitude.3. Failure to maintain heading.4. Failure to maintain altitude.5. Improper pedal trim.

Figure 12-19. Flight instrument indications in a stabilized constant rate climb.

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STRAIGHT CLIMBS (CONSTANT AIRSPEEDAND CONSTANT RATE)For any power setting and load condition, there isonly one airspeed that will give the most efficientrate of climb. To determine this, you should con-sult the climb data for the type of helicopter beingflown. The technique varies according to the air-speed on entry and whether you want to make aconstant airspeed or constant rate climb.

ENTRYTo enter a constant airspeed climb from cruise air-speed, when the climb speed is lower than cruisespeed, simultaneously increase power to theclimb power setting and adjust pitch attitude to theapproximate climb attitude. The increase in powercauses the helicopter to start climbing and onlyvery slight back cyclic pressure is needed to com-plete the change from level to climb attitude. Theattitude indicator should be used to accomplishthe pitch change. If the transition from level flightto a climb is smooth, the vertical speed indicatorshows an immediate upward trend and then stopsat a rate appropriate to the stabilized airspeed andattitude. Primary and supporting instruments forclimb entry are illustrated in figure 12-17.

When the helicopter stabilizes on a constant air-speed and attitude, the airspeed indicatorbecomes primary for pitch. The torque meter con-tinues to be primary for power and should be mon-itored closely to determine if the proper climbpower setting is being maintained. Primary and

supporting instruments for a stabilized constantairspeed climb are shown in figure 12-18.

The technique and procedures for entering a con-stant rate climb are very similar to those previ-ously described for a constant airspeed climb. Fortraining purposes, a constant rate climb is enteredfrom climb airspeed. The rate used is the one thatis appropriate for the particular helicopter beingflown. Normally, in helicopters with low climb rates,500 f.p.m. is appropriate, in helicopters capable ofhigh climb rates, use a rate of 1,000 f.p.m.

To enter a constant rate climb, increase power tothe approximate setting for the desired rate. Aspower is applied, the airspeed indicator is primaryfor pitch until the vertical speed approaches thedesired rate. At this time, the vertical speed indica-tor becomes primary for pitch. Change pitch atti-tude by reference to the attitude indicator tomaintain the desired vertical speed. When the VSIbecomes primary for pitch, the airspeed indicatorbecomes primary for power. Primary and support-ing instruments for a stabilized constant rate climbare illustrated in figure 12-19. Adjust power tomaintain desired airspeed. Pitch attitude andpower corrections should be closely coordinated.To illustrate this, if the vertical speed is correct butthe airspeed is low, add power. As power isincreased, it may be necessary to lower the pitchattitude slightly to avoid increasing the vertical rate.Adjust the pitch attitude smoothly to avoid over-controlling. Small power corrections usually will be

Figure 12-20. Flight instrument indications for a standard rate turn to the left.

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sufficient to bring the airspeed back to the desiredindication.

LEVELOFF The leveloff from a constant airspeed climb mustbe started before reaching the desired altitude.Although the amount of lead varies with the heli-copter being flown and your piloting technique, themost important factor is vertical speed. As a rule ofthumb, use 10 percent of the vertical velocity asyour lead point. For example, if the rate of climb is500 f.p.m., initiate the leveloff approximately 50 feetbefore the desired altitude. When the proper leadaltitude is reached, the altimeter becomes primaryfor pitch. Adjust the pitch attitude to the level flightattitude for that airspeed. Cross-check the altimeterand VSI to determine when level flight has beenattained at the desired altitude. To level off at cruiseairspeed, if this speed is higher than climb air-speed, leave the power at the climb power settinguntil the airspeed approaches cruise airspeed, thenreduce it to the cruise power setting.

The leveloff from a constant rate climb is accom-plished in the same manner as the leveloff from aconstant airspeed climb.

STRAIGHT DESCENTS (CONSTANTAIRSPEED AND CONSTANT RATE)A descent may be performed at any normal air-speed the helicopter is capable of, but the air-speed must be determined prior to entry. Thetechnique is determined by whether you want toperform a constant airspeed or a constant ratedescent.

ENTRYIf your airspeed is higher than descending air-speed, and you wish to make a constant airspeeddescent at the descending airspeed, reducepower to the descending power setting and main-tain a constant altitude using cyclic pitch control.When you approach the descending airspeed, theairspeed indicator becomes primary for pitch, andthe torque meter is primary for power. As you holdthe airspeed constant, the helicopter begins todescend. For a constant rate descent, reduce thepower to the approximate setting for the desiredrate. If the descent is started at the descendingairspeed, the airspeed indicator is primary forpitch until the VSI approaches the desired rate. Atthis time, the vertical speed indicator becomes pri-mary for pitch, and the airspeed indicator becomes primary for power.Coordinate power and pitch attitude control aswas described earlier for constant rate climbs.

LEVELOFFThe leveloff from a constant airspeed descentmay be made at descending airspeed or at cruiseairspeed, if this is higher than descending air-speed. As in a climb leveloff, the amount of leaddepends on the rate of descent and control tech-nique. For a leveloff at descending airspeed, thelead should be approximately 10 percent of thevertical speed. At the lead altitude, simultaneouslyincrease power to the setting necessary to main-tain descending airspeed in level flight. At thispoint, the altimeter becomes primary for pitch, andthe airspeed indicator becomes primary for power.

To level off at a higher airspeed than descendingairspeed, increase the power approximately 100 to150 feet prior to reaching the desired altitude. Thepower setting should be that which is necessary tomaintain the desired airspeed in level flight. Holdthe vertical speed constant until approximately 50feet above the desired altitude. At this point, thealtimeter becomes primary for pitch, and the air-speed indicator becomes primary for power. Theleveloff from a constant rate descent should beaccomplished in the same manner as the levelofffrom a constant airspeed descent.

COMMON ERRORS DURING STRAIGHT CLIMBSAND DESCENTS1. Failure to maintain heading.2. Improper use of power.3. Poor control of pitch attitude.4. Failure to maintain proper pedal trim.5. Failure to level off on desired altitude.

TURNSWhen making turns by reference to the flightinstruments, they should be made at a definiterate. Turns described in this chapter are those thatdo not exceed a standard rate of 3° per second asindicated on the turn-and-slip indicator. True air-speed determines the angle of bank necessary tomaintain a standard rate turn. A rule of thumb todetermine the approximate angle of bank requiredfor a standard rate turn is to divide your airspeedby 10 and add one-half the result. For example, at60 knots, approximately 9° of bank is required (60÷ 10 = 6 + 3 = 9); at 80 knots, approximately 12° ofbank is needed for a standard rate turn.

To enter a turn, apply lateral cyclic in the directionof the desired turn. The entry should be accom-plished smoothly, using the attitude indicator toestablish the approximate bank angle. When theturn indicator indicates a standard rate turn, itbecomes primary for bank. The attitude indicatornow becomes a supporting instrument. During levelturns, the altimeter is primary for pitch, and the air-

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speed indicator is primary for power. Primary andsupporting instruments for a stabilized standardrate turn are illustrated in figure 12-20. If anincrease in power is required to maintain airspeed,slight forward cyclic pressure may be requiredsince the helicopter tends to pitch up as collectivepitch angle is increased. Apply pedal trim, asrequired, to keep the ball centered.

To recover to straight-and-level flight, apply cyclicin the direction opposite the turn. The rate of roll-out should be the same as the rate used whenrolling into the turn. As you initiate the turnrecover, the attitude indicator becomes primary forbank. When the helicopter is approximately level,the heading indicator becomes primary for bankas in straight-and-level flight. Cross-check the air-speed indicator and ball closely to maintain thedesired airspeed and pedal trim.

TURNS TO A PREDETERMINED HEADINGA helicopter turns as long as its lateral axis is tilted;therefore, the recovery must start before the desiredheading is reached. The amount of lead varies withthe rate of turn and your piloting technique.

As a guide, when making a 3° per second rate ofturn, use a lead of one-half the bank angle. Forexample, if you are using a 12° bank angle, usehalf of that, or 6°, as the lead point prior to yourdesired heading. Use this lead until you are ableto determine the exact amount required by yourparticular technique. The bank angle should never

exceed the number of degrees to be turned. As inany standard rate turn, the rate of recovery shouldbe the same as the rate for entry. During turns topredetermined headings, cross-check the primaryand supporting pitch, bank, and power instru-ments closely.

TIMED TURNSA timed turn is a turn in which the clock and turn-and-slip indicator are used to change heading adefinite number of degrees in a given time. Forexample, using a standard rate turn, a helicopterturns 45° in 15 seconds. Using a half-standardrate turn, the helicopter turns 45° in 30 seconds.Timed turns can be used if your heading indicatorbecomes inoperative.

Prior to performing timed turns, the turn coordina-tor should be calibrated to determine the accuracyof its indications. To do this, establish a standardrate turn by referring to the turn-and-slip indicator.Then as the sweep second hand of the clockpasses a cardinal point (12, 3, 6, or 9), check theheading on the heading indicator. While holdingthe indicated rate of turn constant, note the head-ing changes at 10-second intervals. If the helicop-ter turns more or less than 30° in that interval, asmaller or larger deflection of the needle is neces-sary to produce a standard rate turn. When youhave calibrated the turn-and-slip indicator duringturns in each direction, note the corrected deflec-tions, if any, and apply them during all timed turns.

Figure 12-21. Flight instrument indications for a stabilized left climbing turn at a constant airspeed.

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Two methods of changing airspeed in turns maybe used. In the first method, airspeed is changedafter the turn is established. In the second method,the airspeed change is initiated simultaneouslywith the turn entry. The first method is easier, butregardless of the method used, the rate of cross-check must be increased as you reduce power. Asthe helicopter decelerates, check the altimeter andVSI for needed pitch changes, and the bank instru-ments for needed bank changes. If the needle ofthe turn-and-slip indicator shows a deviation fromthe desired deflection, change the bank. Adjustpitch attitude to maintain altitude. When the air-speed approaches that desired, the airspeed indi-cator becomes primary for power control. Adjustthe torque meter to maintain the desired airspeed.Use pedal trim to ensure the maneuver is coordi-nated.

Until your control technique is very smooth, fre-quently cross-check the attitude indicator to keepfrom overcontrolling and to provide approximatebank angles appropriate for the changing air-speeds.

30° BANK TURNA turn using 30° of bank is seldom necessary, oradvisable, in IMC, but it is an excellent maneuverto increase your ability to react quickly andsmoothly to rapid changes of attitude. Eventhough the entry and recovery technique are thesame as for any other turn, you will probably find itmore difficult to control pitch because of thedecrease in vertical lift as the bank increases.Also, because of the decrease in vertical lift, thereis a tendency to lose altitude and/or airspeed.Therefore, to maintain a constant altitude and air-speed, additional power is required. You shouldnot initiate a correction, however, until the instru-ments indicate the need for a correction. Duringthe maneuver, note the need for a correction onthe altimeter and vertical speed indicator, thencheck the indications on the attitude indicator, andmake the necessary adjustments. After you havemade this change, again check the altimeter andvertical speed indicator to determine whether ornot the correction was adequate.

You use the same cross-check and control tech-nique in making timed turns that you use to maketurns to a predetermined heading, except that yousubstitute the clock for the heading indicator. Theneedle of the turn-and-slip indicator is primary forbank control, the altimeter is primary for pitch con-trol, and the airspeed indicator is primary forpower control. Begin the roll-in when the clock’ssecond hand passes a cardinal point, hold the turnat the calibrated standard-rate indication, or half-standard-rate for small changes in heading, andbegin the roll-out when the computed number ofseconds has elapsed. If the roll-in and roll-outrates are the same, the time taken during entryand recovery need not be considered in the timecomputation.

If you practice timed turns with a full instrumentpanel, check the heading indicator for the accu-racy of your turns. If you execute the turns withoutthe heading indicator, use the magnetic compassat the completion of the turn to check turn accu-racy, taking compass deviation errors into consid-eration.

CHANGE OF AIRSPEED IN TURNSChanging airspeed in turns is an effective maneu-ver for increasing your proficiency in all threebasic instrument skills. Since the maneuverinvolves simultaneous changes in all componentsof control, proper execution requires a rapidcross-check and interpretation, as well as smoothcontrol. Proficiency in the maneuver also con-tributes to your confidence in the instruments dur-ing attitude and power changes involved in morecomplex maneuvers.

Pitch and power control techniques are the sameas those used during airspeed changes instraight-and-level flight. As discussed previously,the angle of bank necessary for a given rate ofturn is proportional to the true airspeed. Since theturns are executed at standard rate, the angle ofbank must be varied in direct proportion to theairspeed change in order to maintain a constantrate of turn. During a reduction of airspeed, youmust decrease the angle of bank and increasethe pitch attitude to maintain altitude and a stan-dard rate turn.

The altimeter and the needle on the turn indicatorshould remain constant throughout the turn. Thealtimeter is primary for pitch control, and the turnneedle is primary for bank control. The torquemeter is primary for power control while the air-speed is changing. As the airspeed approachesthe new indication, the airspeed indicatorbecomes primary for power control.

Land as soon as possible—Land without delay at the nearest suitablearea, such as an open field, at which a safe approach and landing isassured.

Land immediately—The urgency of the landing is paramount. The pri-mary consideration is to assure the survival of the occupants. Landing intrees, water, or other unsafe areas should be considered only as a lastresort.

Land as soon as practical—The landing site and duration of flight areat the discretion of the pilot. Extended flight beyond the nearestapproved landing area is not recommended.

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CLIMBING AND DESCENDING TURNSFor climbing and descending turns, the techniquesdescribed earlier for straight climbs and descentsand those for standard rate turns are combined.For practice, start the climb or descent and turnsimultaneously. The primary and supporting instru-ments for a stabilized constant airspeed left climb-ing turn are illustrated in figure 12-21. The levelofffrom a climbing or descending turn is the same asthe leveloff from a straight climb or descent. Torecover to straight-and-level flight, you may stopthe turn and then level off, level off and then stopthe turn, or simultaneously level off and stop theturn. During climbing and descending turns, keepthe ball of the turn indicator centered with pedaltrim.

COMPASS TURNSThe use of gyroscopic heading indicators makeheading control very easy. However, if the head-ing indicator fails or your helicopter does nothave one installed, you must use the magneticcompass for heading reference. When makingcompass-only turns, you need to adjust for thelead or lag created by acceleration and decelera-tion errors so that you roll out on the desiredheading. When turning to a heading of north, thelead for the roll-out must include the number ofdegrees of your latitude plus the lead you nor-mally use in recovery from turns. During a turn toa south heading, maintain the turn until the com-pass passes south the number of degrees of yourlatitude, minus your normal roll-out lead. Forexample, when turning from an easterly directionto north, where the latitude is 30°, start the roll-

out when the compass reads 037° (30° plus one-half the 15° angle of bank, or whatever amount isappropriate for your rate of roll-out). When turn-ing from an easterly direction to south, start theroll-out when the magnetic compass reads 203°(180° plus 30° minus one-half the angle of bank).When making similar turns from a westerly direc-tion, the appropriate points at which to begin yourroll-out would be 323° for a turn to north, and 157°for a turn to south.

COMMON ERRORS DURING TURNS1. Failure to maintain desired turn rate.2. Failure to maintain altitude in level turns.3. Failure to maintain desired airspeed.4. Variation in the rate of entry and recovery.5. Failure to use proper lead in turns to a head-

ing.6. Failure to properly compute time during timed

turns.7. Failure to use proper leads and lags during

the compass turns.8. Improper use of power.9. Failure to use proper pedal trim.

UNUSUAL ATTITUDESAny maneuver not required for normal helicopterinstrument flight is an unusual attitude and may becaused by any one or a combination of factors,such as turbulence, disorientation, instrument fail-ure, confusion, preoccupation with cockpit duties,carelessness in cross-checking, errors in instru-ment interpretation, or lack of proficiency in aircraftcontrol. Due to the instability characteristics of thehelicopter, unusual attitudes can be extremely criti-

Figure 12-22. Flight instrument indications during an instrument takeoff.

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cal. As soon as you detect an unusual attitude,make a recovery to straight-and-level flight as soonas possible with a minimum loss of altitude.

To recover from an unusual attitude, correct bankand pitch attitude, and adjust power as necessary.All components are changed almost simultane-ously, with little lead of one over the other. Youmust be able to perform this task with and withoutthe attitude indicator. If the helicopter is in a climb-

ing or descending turn, correct bank, pitch, andpower. The bank attitude should be corrected byreferring to the turn-and-slip indicator and attitudeindicator. Pitch attitude should be corrected by ref-erence to the altimeter, airspeed indicator, VSI,and attitude indicator. Adjust power by referring tothe airspeed indicator and torque meter.

Since the displacement of the controls used inrecoveries from unusual attitudes may be greaterthan those for normal flight, take care in making

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Flying at night can be a very pleasant experience.The air is generally cooler and smoother, resultingin better helicopter performance and a more com-fortable flight. You generally also experience lesstraffic and less radio congestion.

NIGHT FLIGHT PHYSIOLOGYBefore discussing night operations, it is importantyou understand how your vision is affected atnight and how to counteract the visual illusions,which you might encounter.

VISION IN FLIGHTVision is by far the most important sense that youhave, and flying is obviously impossible withoutit. Most of the things you perceive while flying arevisual or heavily supplemented by vision. Thevisual sense is especially important in collisionavoidance and depth perception. Your visionsensors are your eyes, even though they are notperfect in the way they function or see objects.Since your eyes are not always able to see allthings at all times, illusions and blindspots occur.The more you understand the eye and how itfunctions, the easier it is to compensate for theseillusions and blindspots.

THE EYEThe eye works in much the same way as a cam-era. Both have an aperture, lens, method of focus-ing, and a surface for registering images. [Figure13-1].

Vision is primarily the result of light striking a pho-tosensitive layer, called the retina, at the back ofthe eye. The retina is composed of light-sensitivecones and rods. The cones in your eye perceivean image best when the light is bright, while therods work best in low light. The pattern of light thatstrikes the cones and rods is transmitted as elec-trical impulses by the optic nerve to the brainwhere these signals are interpreted as an image.The area where the optic nerve meets the retinacontains no cones or rods, creating a blind spot invision. Normally, each eye compensates for theother’s blind spot. [Figure 13-2]

CONESCones are concentrated around the center of theretina. They gradually diminish in number as thedistance from the center increases. Cones allowyou to perceive color by sensing red, blue, and

Figure 13-1. A camera is able to focus on near and far objects bychanging the distance between the lens and the film. You can seeobjects clearly at various distances because the shape of your eye’slens is changed automatically by small muscles.

Figure 13-2. This illustration provides a dramatic example of theeye’s blind spot. Cover your right eye and hold this page at arm’slength. Focus your left eye on the X in the right side of the visual,and notice what happens to the aircraft as you slowly bring thepage closer to your eye.

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green light. Directly behind the lens, on theretina, is a small, notched area called the fovea.This area contains only a high concentration of

cone receptors. When you look directly at anobject, the image is focused mainly on thefovea. The cones, however, do not function wellin darkness, which explains why you cannot seecolor as vividly at night as you can during theday. [Figure 13-3]

RODSThe rods are our dim light and night receptors andare concentrated outside the fovea area. Thenumber of rods increases as the distance from thefovea increases. Rods sense images only in blackand white. Because the rods are not locateddirectly behind the pupil, they are responsible formuch of our peripheral vision. Images that moveare perceived more easily by the rod areas thanby the cones in the fovea. If you have ever seensomething move out of the corner of your eye, itwas most likely detected by your rod receptors.

Since the cones do not function well in the dark,you may not be able to see an object if you lookdirectly at it. The concentration of cones in thefovea can make a night blindspot at the center ofyour vision. To see an object clearly, you mustexpose the rods to the image. This is accom-plished by looking 5° to 10° off center of the objectyou want to see. You can try out this effect on adim light in a darkened room. When you lookdirectly at the light, it dims or disappears alto-gether. If you look slightly off center, it becomesclearer and brighter. [Figure 13-4]

How well you see at night is determined by therods in your eyes, as well as the amount of lightallowed into your eyes. The wider the pupil is openat night, the better your night vision becomes.

NIGHT VISIONThe cones in your eyes adapt quite rapidly tochanges in light intensities, but the rods do not. If youhave ever walked from bright sunlight into a darkmovie theater, you have experienced this dark adap-tation period. The rods can take approximately 30minutes to fully adapt to the dark. A bright light, how-ever, can completely destroy your night adaptationand severely restrict your visual acuity.

There are several things you can do to keep youreyes adapted to the dark. The first is obvious;avoid bright lights before and during the flight. For30 minutes before a night flight, avoid any brightlight sources, such as headlights, landing lights,strobe lights, or flashlights. If you encounter abright light, close one eye to keep it light sensitive.This allows you to see again once the light isgone. Light sensitivity also can be gained by usingsunglasses if you will be flying from daylight intoan area of increasing darkness.

Red cockpit lighting also helps preserve your nightvision, but red light severely distorts some colors,and completely washes out the color red. Thismakes reading an aeronautical chart difficult. Adim white light or carefully directed flashlight canenhance your night reading ability. While flying atnight, keep the instrument panel and interior lightsturned up no higher than necessary. This helpsyou see outside visual references more easily. Ifyour eyes become blurry, blinking more frequentlyoften helps.

Your diet and general physical health have animpact on how well you can see in the dark.Deficiencies in vitamins A and C have been shownto reduce night acuity. Other factors, such as car-bon monoxide poisoning, smoking, alcohol, cer-

Figure 13-3. The best vision in daylight is obtained by lookingdirectly at the object. This focuses the image on the fovea, wheredetail is best seen.

Figure 13-4. In low light, the cones lose much of their visual acu-ity, while rods become more receptive. The eye sacrifices sharp-ness for sensitivity. Your ability to see an object directly in front ofyou is reduced, and you lose much of your depth perception, aswell as your judgment of size.

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tain drugs, and a lack of oxygen also can greatlydecrease your night vision.

NIGHT SCANNINGGood night visual acuity is needed for collisionavoidance. Night scanning, like day scanning,uses a series of short, regularly spaced eye move-ments in 10° sectors. Unlike day scanning, how-ever, off-center viewing is used to focus objectson the rods rather than the fovea blindspot. Whenyou look at an object, avoid staring at it too long. Ifyou stare at an object without moving your eyes,the retina becomes accustomed to the light inten-sity and the image begins to fade. To keep itclearly visible, new areas in the retina must beexposed to the image. Small, circular eye move-ments help eliminate the fading. You also need tomove your eyes more slowly from sector to sectorthan during the day to prevent blurring.

AIRCRAFT LIGHTINGIn order to see other aircraft more clearly, regula-tions require that all aircraft operating during thenight hours have special lights and equipment.The requirements for operating at night are foundin Title 14 of the Code of Federal Regulations (14

CFR) part 91. In addition to aircraft lighting, theregulations also provide a definition of nighttime,currency requirements, fuel reserves, and neces-sary electrical systems.

Position lights enable you to locate another air-craft, as well as help you determine its direction offlight. The approved aircraft lights for night opera-tions are a green light on the right cabin side orwingtip, a red light on the left cabin side or wingtip,and a white position light on the tail. In addition,flashing aviation red or white anticollision lightsare required for night flights. These flashing lightscan be in a number of locations, but are mostcommonly found on the top and bottom of thecabin. [Figure 13-5]

VISUAL ILLUSIONSThere are many different types of visual illusionsthat you can experience at any time, day or night.The next few paragraphs cover some of the illu-sions that commonly occur at night.

AUTOKINESISAutokinesis is caused by staring at a single pointof light against a dark background, such as a

Figure 13-5. By interpreting the position lights on other aircraft, you can determine whether the aircraft is flying away from you or is on acollision course. If you see a red position light to the right of a green light, such as shown by aircraft number 1, it is flying toward you. Youshould watch this aircraft closely and be ready to change course. Aircraft number 2, on the other hand, is flying away from you, as indi-cated by the white position light.

Figure 13-6. You can place your helicopter in an extremely dan-gerous flight attitude if you align the helicopter with the wronglights. Here, the helicopter is aligned with a road and not the hori-zon.

Figure 13-7. In this illusion, the shoreline is mistaken for the hori-zon. In an attempt to correct for the apparent nose-high attitude, apilot may lower the collective and attempt to fly “beneath theshore.”

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ground light or bright star, for more than a fewseconds. After a few moments, the light appearsto move on its own. To prevent this illusion, youshould focus your eyes on objects at varying dis-tances and not fixate on one target, as well asmaintain a normal scan pattern.

NIGHT MYOPIAAnother problem associated with night flying isnight myopia, or night-induced nearsightedness.With nothing to focus on, your eyes automaticallyfocus on a point just slightly ahead of your aircraft.Searching out and focusing on distant lightsources, no matter how dim, helps prevent theonset of night myopia.

FALSE HORIZONA false horizon can occur when the natural hori-zon is obscured or not readily apparent. It can begenerated by confusing bright stars and city lights.[Figure 13-6] It can also occur while you are flyingtoward the shore of an ocean or a large lake.Because of the relative darkness of the water, thelights along the shoreline can be mistaken for thestars in the sky. [Figure 13-7]

LANDING ILLUSIONSLanding illusions occur in many forms. Above fea-tureless terrain at night, there is a natural ten-dency to fly a lower-than-normal approach.Elements that cause any type of visual obscura-tion, such as rain, haze, or a dark runway environ-ment also can cause low approaches. Brightlights, steep surrounding terrain, and a wide run-way can produce the illusion of being too low, witha tendency to fly a higher-than-normal approach.

NIGHT FLIGHTThe night flying environment and the techniquesyou use when flying at night, depend on outsideconditions. Flying on a bright, clear, moonlitevening when the visibility is good and the wind iscalm, is not much different from flying during theday. However, if you are flying on an overcastnight over a sparsely populated area, with little orno outside lights from the ground, the situation isquite different. Visibility is restricted so you haveto be more alert in steering clear of obstructionsand low clouds. Your options are also limited inthe event of an emergency, as it is more difficultto find a place to land and determine wind direc-tion and speed. At night, you have to rely moreheavily on the aircraft systems, such as lights,flight instruments, and navigation equipment. As aprecaution, if the visibility is limited or outside ref-erences are inadequate, you should strongly con-

sider delaying the flight until conditions improve,unless you have received training in instrumentflight and your helicopter has the appropriateinstrumentation and equipment.

PREFLIGHTThe preflight inspection is performed in the usualmanner, except it should be done in a well lit areaor with a flashlight. Careful attention must be paidto the aircraft electrical system. In helicoptersequipped with fuses, a spare set is required byregulation, and common sense, so make surethey are onboard. If the helicopter is equippedwith circuit breakers, check to see that they arenot tripped. A tripped circuit breaker may be anindication of an equipment malfunction. Reset itand check the associated equipment for properoperation.

Check all the interior lights, especially the instru-ment and panel lights. The panel lighting can usu-ally be controlled with a rheostat or dimmer switch,allowing you to adjust the intensity. If the lights aretoo bright, a glare may reflect off the windshieldcreating a distraction. Always carry a flashlightwith fresh batteries to provide an alternate sourceof light if the interior lights malfunction.

All aircraft operating between sunset and sunriseare required to have operable navigation lights.Turn these lights on during the preflight toinspect them visually for proper operation.Between sunset and sunrise, theses lights mustbe on any time the engine is running.

All recently manufactured aircraft certified for nightflight, must have an anticollision light that makesthe aircraft more visible to other pilots. This light iseither a red or white flashing light and may be inthe form of a rotating beacon or a strobe. Whileanticollision lights are required for night VFRflights, they may be turned off any time they cre-ate a distraction for the pilot.

One of the first steps in preparation for night flightis becoming thoroughly familiar with the heli -copter’s cockpit, instrumentation and control lay-out. It is recommended that you practice locatingeach instrument, control, and switch, both withand without cabin lights. Since the markings onsome switches and circuit breaker panels may behard to read at night, you should assure yourselfthat you are able to locate and use these devices,and read the markings in poor light conditions.Before you start the engine, make sure all neces-sary equipment and supplies needed for the flight,

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such as charts, notepads, and flashlights, areaccessible and ready for use.

ENGINE STARTING AND ROTORENGAGEMENTUse extra caution when starting the engine andengaging the rotors, especially in dark areas withlittle or no outside lights. In addition to the usualcall of “clear,” turn on the position and anticollisionlights. If conditions permit, you might also want toturn the landing light on momentarily to help warnothers that you are about to start the engine andengage the rotors.

TAXI TECHNIQUELanding lights usually cast a beam that is narrowand concentrated ahead of the helicopter, so illu-mination to the side is minimal. Therefore, youshould slow your taxi at night, especially in con-gested ramp and parking areas. Some helicoptershave a hover light in addition to a landing light,which illuminates a larger area under the helicop-ter.

When operating at an unfamiliar airport at night,you should ask for instructions or advice concern-ing local conditions, so as to avoid taxiing intoareas of construction, or unlighted, unmarkedobstructions. Ground controllers or UNICOMoperators are usually cooperative in furnishingyou with this type of information.

TAKEOFFBefore takeoff, make sure that you have a clear,unobstructed takeoff path. At airports, you mayaccomplish this by taking off over a runway or taxi-way, however, if you are operating off-airport, youmust pay more attention to the surroundings.Obstructions may also be difficult to see if you aretaking off from an unlighted area. Once you havechosen a suitable takeoff path, select a point downthe takeoff path to use for directional reference.During a night takeoff, you may notice a lack ofreliable outside visual references after you are air-borne. This is particularly true at small airports andoff-airport landing sites located in sparsely popu-lated areas. To compensate for the lack of outsidereferences, use the available flight instruments asan aid. Check the altimeter and the airspeed indi-cator to verify the proper climb attitude. An attitudeindicator, if installed, can enhance your attitudereference.

The first 500 feet of altitude after takeoff is con-sidered to be the most critical period in transition-ing from the comparatively well-lighted airport orheliport into what sometimes appears to be totaldarkness. A takeoff at night is usually an “altitudeover airspeed” maneuver, meaning you will mostlikely perform a nearly maximum performancetakeoff. This improves the chances for obstacleclearance and enhances safety. When perform-ing this maneuver, be sure to avoid the cross-hatched or shaded areas of the height-velocitydiagram.

EN ROUTE PROCEDURESIn order to provide a higher margin of safety, it isrecommended that you select a cruising altitudesomewhat higher than normal. There are severalreasons for this. First, a higher altitude gives youmore clearance between obstacles, especiallythose that are difficult to see at night, such as hightension wires and unlighted towers. Secondly, inthe event of an engine failure, you have more timeto set up for a landing and the gliding distance isgreater giving you more options in making a safelanding. Thirdly, radio reception is improved, par-ticularly if you are using radio aids for navigation.

During your preflight planning, it is recommendedthat you select a route of flight that keeps youwithin reach of an airport, or any safe landing site,as much of the time as possible. It is also recom-mended that you fly as close as possible to a pop-ulated or lighted area such as a highway or town.Not only does this offer more options in the eventof an emergency, but also makes navigation a loteasier. A course comprised of a series of slightzig-zags to stay close to suitable landing sites andwell lighted areas, only adds a little more time anddistance to an otherwise straight course.

In the event that you have to make a forced land-ing at night, use the same procedure recom-mended for daytime emergency landings. Ifavailable, turn on the landing light during the finaldescent to help in avoiding obstacles along yourapproach path.

COLLISION AVOIDANCE AT NIGHTAt night, the outside visual references are greatlyreduced especially when flying over a sparselypopulated area with little or no lights. The result isthat you tend to focus on a single point or instru-ment, making you less aware of the other trafficaround. You must make a special effort to devoteenough time to scan for traffic. You can determineanother aircraft’s direction of flight by interpretingthe position and anticollision lights.

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APPROACH AND LANDINGNight approaches and landings do have someadvantages over daytime approaches, as the airis generally smoother and the disruptive effects ofturbulence and excessive crosswinds are oftenabsent. However, there are a few special consid-erations and techniques that apply to approachesat night. For example, when landing at night,especially at an unfamiliar airport, make theapproach to a lighted runway and then use thetaxiways to avoid unlighted obstructions or equip-ment.

Carefully controlled studies have revealed thatpilots have a tendency to make lower approachesat night than during the day. This is potentiallydangerous as you have a greater chance of hittingan obstacle, such as an overhead wire or fence,which are difficult to see. It is good practice tomake steeper approaches at night, thus increas-ing any obstacle clearance. Monitor your altitudeand rate of descent using the altimeter.

Another tendency is to focus too much on thelanding area and not pay enough attention to air-speed. If too much airspeed is lost, a settling-with-power condition may result. Maintain the properattitude during the approach, and make sure youkeep some forward airspeed and movement untilclose to the ground. Outside visual reference forairspeed and rate of closure may not be available,especially when landing in an unlighted area, sopay special attention to the airspeed indicator

Although the landing light is a helpful aid whenmaking night approaches, there is an inherent dis-advantage. The portion of the landing area illumi-nated by the landing light seems higher than thedark area surrounding it. This effect can causeyou to terminate the approach at too high an alti-tude, resulting in a settling-with-power conditionand a hard landing.

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Aeronautical decision making (ADM) is a system-atic approach to the mental process used by pilotsto consistently determine the best course of actionin response to a given set of circumstances. Theimportance of learning effective ADM skills cannotbe overemphasized. While progress is continuallybeing made in the advancement of pilot trainingmethods, aircraft equipment and systems, andservices for pilots, accidents still occur. Despite allthe changes in technology to improve flight safety,one factor remains the same—the human factor. It is estimated thatapproximately 65 percent of the total rotorcraftaccidents are human factors related.

Historically, the term “pilot error” has been used todescribe the causes of these accidents. Pilot errormeans that an action or decision made by the pilotwas the cause of, or a contributing factor that leadto, the accident. This definition also includes thepilot’s failure to make a decision or take action.From a broader perspective, the phrase “humanfactors related” more aptly describes these acci-dents since it is usually not a single decision thatleads to an accident, but a chain of events trig-gered by a number of factors.

The poor judgment chain, sometimes referred toas the “error chain,” is a term used to describe thisconcept of contributing factors in a human factorsrelated accident. Breaking one link in the chainnormally is all that is necessary to change the out-

come of the sequence of events. The following isan example of the type of scenario illustrating thepoor judgment chain.

A helicopter pilot, with limited experience flying inadverse weather, wants to be back at his homeairport in time to attend an important social affair.He is already 30 minutes late. Therefore, hedecides not to refuel his helicopter, since heshould get back home with at least 20 minutes ofreserve. In addition, in spite of his inexperience,he decides to fly through an area of possible thun-derstorms in order to get back just before dark.Arriving in the thunderstorm area, he encounterslightning, turbulence, and heavy clouds. Night isapproaching, and the thick cloud cover makes itvery dark. With his limited fuel supply, he is notable to circumnavigate the thunderstorms. In thedarkness and turbulence, the pilot becomes spa-tially disoriented while attempting to continue fly-ing with visual reference to the ground instead ofusing what instruments he has to make a 180°turn. In the ensuing crash, the pilot is seriouslyinjured and the helicopter completely destroyed.

By discussing the events that led to this accident,we can understand how a series of judgmentale r r o r scontributed to the final outcome of this flight. Forexample, one of the first elements that affectedthe pilot’s flight was a decision regarding theweather. The pilot knew there were going to bethunderstorms in the area, but he had flown nearthunderstorms before and never had an accident.

Next, he let his desire to arrive at his destinationon time override his concern for a safe flight. Forone thing, in order to save time, he did not refuelthe helicopter, which might have allowed him theopportunity to circumnavigate the bad weather.Then he overestimated his flying abilities anddecided to use a route that took him through apotential area of thunderstorm activity. Next, thepilot pressed on into obviously deteriorating con-ditions instead of changing course or landing prior to his destination.

Human Factors—The study ofhow people interact with theirenvironments. In the case of gen-eral aviation, it is the study of howpilot performance is influenced bysuch issues as the design of cock-pits, the function of the organs ofthe body, the effects of emotions,and the interaction and communi-cation with the other participantsof the aviation community, such asother crew members and air trafficcontrol personnel.

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On numerous occasions during the flight, the pilotcould have made effective decisions that mayhave prevented this accident. However, as thechain of events unfolded, each poor decision lefthim with fewer and fewer options. Making sounddecisions is the key to preventing accidents.Traditional pilot training has emphasized flyingskills, knowledge of the aircraft, and familiaritywith regulations. ADM training focuses on thedecision-making process and the factors thataffect a pilot’s ability to make effective choices.

ORIGINS OF ADM TRAININGThe airlines developed some of the first trainingprograms that focused on improving aeronauticaldecision making. Human factors-related accidentsmotivated the airline industry to implement crew

resource management (CRM) training for flightcrews. The focus of CRM programs is the effec-tive use of all available resources; humanresources, hardware, and information. Humanresources include all groups routinely working withthe cockpit crew (or pilot) who are involved in deci-sions that are required to operate a flight safely.These groups include, but are not limited to:ground personnel, dispatchers, cabin crewmem-bers, maintenance personnel, external-load rig-gers, and air traffic controllers. Although the CRMconcept originated as airlines developed ways offacilitating crew cooperation to improve decisionmaking in the cockpit, CRM principles, such asworkload management, situational awareness,communication, the leadership role of the captain,and crewmember coordination have direct appli-

Figure 14-1. These terms are used in AC 60-22 to explain concepts used in ADM training.

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there was enough power for the hover check,you felt there was sufficient power to take off.

Even though the helicopter accelerated slowlyduring the takeoff, the distance between the heli-copter and the ground continued to increase.However, when you attempted to establish thebest rate of climb speed, the nose wanted to pitchup to a higher than normal attitude, and younoticed that the helicopter was not gaining enoughaltitude in relation to the canyon wall a couplehundred yards ahead.

CHOOSING A COURSE OF ACTIONAfter the problem has been identified, you mustevaluate the need to react to it and determine theactions that need to be taken to resolve the situa-tion in the time available. The expected outcomeof each possible action should be considered andthe risks assessed before you decide on aresponse to the situation.

Your first thought was to pull up on the collectiveand yank back on the cyclic, but after weighing theconsequences of possibly losing rotor r.p.m. andnot being able to maintain the climb rate suffi -ciently enough to clear the canyon wall, which isnow only a hundred yards away, you realize thatyour only course is to try to turn back to the land-ing zone on the canyon floor.

IMPLEMENTING THE DECISION ANDEVALUATING THE OUTCOMEAlthough a decision may be reached and a courseof action implemented, the decision-makingprocess is not complete. It is important to thinkahead and determine how the decision couldaffect other phases of the flight. As the flight pro-gresses, you must continue to evaluate the out-come of the decision to ensure that it is producingthe desired result.

cation to the general aviation cockpit. This alsoincludes single pilot operations since pilots ofsmall aircraft, as well as crews of larger aircraft,must make effective use of all availableresources—human resources, hardware, andinformation. You can also refer to AC 60-22,Aeronautical Decision Making, which providesbackground references, definitions, and other per-tinent information about ADM training in the gen-eral aviation environment. [Figure 14-1]

THE DECISION-MAKING PROCESSAn understanding of the decision-making processprovides you with a foundation for developingADM skills. Some situations, such as engine fail-ures, require you to respond immediately usingestablished procedures with little time for detailedanalysis. Traditionally, pilots have been welltrained to react to emergencies, but are not aswell prepared to make decisions that require amore reflective response. Typically during a flight,you have time to examine any changes that occur,gather information, and assess risk before reach-ing a decision. The steps leading to this conclu-s i o nconstitute the decision-making process.

DEFINING THE PROBLEMProblem definition is the first step in the decision-making process. Defining the problem begins withrecognizing that a change has occurred or that anexpected change did not occur. A problem is per-ceived first by the senses, then is distinguishedthrough insight and experience. These same abil-ities, as well as an objective analysis of all avail-able information, are used to determine the exactnature and severity of the problem.

While doing a hover check after picking up firefighters at the bottom of a canyon, you realizethat you are only 20 pounds under maximumgross weight. What you failed to realize is thatthey had stowed some of their heaviest gear inthe baggage compartment, which shifted the CGslightly behind the aft limits. Since weight andbalance had never created any problems for you in the past, you did not botherto calculate CG and power required. You did,however, try to estimate it by remembering thefigures from earlier in the morning at the basecamp. At a 5,000 foot density altitude and maximum gross weight, theperformance charts indicated you had plenty ofexcess power. Unfortunately, the temperaturewas 93°F and the pressure altitude at the pick uppoint was 6,200 feet (DA = 9,600 feet). Since

Figure 14-2. The DECIDE model can provide a framework foreffective decision making.

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As you make your turn to the downwind, the air-speed drops nearly to zero, and the helicopterbecomes very difficult to control. At this point, youmust increase airspeed in order to maintain trans-lational lift, but since the CG is aft of limits, youneed to apply more forward cyclic than usual. Asyou approach the landing zone with a high rate ofdescent, you realize that you are in a potential set-tling-with-power situation if you try to trade air-speed for altitude and lose ETL. Therefore, you willprobably not be able to terminate the approach ina hover. You decide to make as shallow of anapproach as possible and perform a run-on land-ing.

The decision making process normally consists ofseveral steps before you choose a course ofaction. To help you remember the elements of thedecision-making process, a six-step model hasbeen developed using the acronym “DECIDE.”[Figure 14-2]

RISK MANAGEMENTDuring each flight, decisions must be maderegarding events that involve interactions betweenthe four risk elements—the pilot in command, theaircraft, the environment, and the operation. Thedecision-making process involves an evaluationof each of these risk elements to achieve an accu-rate perception of the flight situation. [Figure 14-3]

One of the most important decisions that a pilot incommand must make is the go/no-go decision.Evaluating each of these risk elements can helpyou decide whether a flight should be conducted

Risk Elements—The four compo-nents of a flight that make up theoverall situation.

NTSB—National TransportationSafety Board.

or continued. Let us evaluate the four risk ele-ments and how they affect our decision makingregarding the following situations.

Pilot—As a pilot, you must continually make deci-sions about your own competency, condition ofhealth, mental and emotional state, level of fatigue,and many other variables. For example, you arecalled early in the morning to make a long flight.You have had only a few hours of sleep, and areconcerned that the congestion you feel could be theonset of a cold. Are you safe to fly?

Aircraft—You will frequently base decisions on yourevaluations of the aircraft, such as its powerplant,performance, equipment, fuel state, or airworthi-ness. Picture yourself in this situation: you are enroute to an oil rig an hour’s flight from shore, andyou have just passed the shoreline. Then you noticethe oil temperature at the high end of the cautionrange. Should you continue out to sea, or return tothe nearest suitable heliport/airport?

Environment—This encompasses many elementsnot pilot or aircraft related. It can include such fac-tors as weather, air traffic control, navaids, terrain,takeoff and landing areas, and surrounding obsta-cles. Weather is one element that can changedrastically over time and distance. Imagine youare ferrying a helicopter cross country andencounter unexpected low clouds and rain in anarea of rising terrain. Do you try to stay underthem and “scud run,” or turn around, stay in theclear, and obtain current weather information?

Operation—The interaction between you as thepilot, your aircraft, and the environment is greatlyinfluenced by the purpose of each flight operation.You must evaluate the three previous areas todecide on the desirability of undertaking or contin-uing the flight as planned. It is worth asking your-self why the flight is being made, how critical is itto maintain the schedule, and is the trip worth the

Figure 14-3. When situationally aware, you have an overview of the total operation and are not fixated on one perceived significant factor.

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risks? For instance, you are tasked to take sometechnicians into rugged mountains for a routinesurvey, and the weather is marginal. Would it bepreferable to wait for better conditions to ensure asafe flight? How would the priorities change if youwere tasked to search for cross-country skierswho had become lost in deep snow and radioedfor help?

ASSESSING RISKExamining NTSB reports and other accidentresearch can help you to assess risk more effec-tively. For example, the accident rate decreases bynearly 50 percent once a pilot obtains 100 hours,and continues to decrease until the 1,000 hourlevel. The data suggest that for the first 500 hours,pilots flying VFR at night should establish higherpersonal limitations than are required by the regu-lations and, if applicable, apply instrument flyingskills in this environment. [Figure 14-4]

Studies also indicate the types of flight activitiesthat are most likely to result in the most seriousaccidents. The majority of fatal general aviationaccident causes fall under the categories ofmaneuvering flight, approaches, takeoff/initialclimb, and weather. Delving deeper into accidentstatistics can provide some important details thatcan help you to understand the risks involved withspecific flying situations. For example, maneuver-ing flight is one of the largest single producers offatal accidents. Fatal accidents, which occur during approach, often happen at night or in IFRconditions. Takeoff/initial climb accidents fre-quently are due to the pilot’s lack of awareness ofthe effects of density altitude on aircraft perform-ance or other improper takeoff planning resultingin loss of control during, or shortly after takeoff.

The majority of weather-related accidents occurafter attempted VFR flight into IFR conditions.

FACTORS AFFECTING DECISIONMAKINGIt is important to point out the fact that being famil-iar with the decision-making process does notensure that you will have the good judgment tobe a safe pilot. The ability to make effective deci-sions as pilot in command depends on a number of factors. Some circumstances, such as the time available to

make a decision, may be beyond your control.However, you can learn to recognize those fac-tors that can be managed, and learn skills toimprove decision-making ability and judgment.

PILOT SELF-ASSESSMENTThe pilot in command of an aircraft is directlyresponsible for, and is the final authority as to, theoperation of that aircraft. In order to effectivelyexercise that responsibility and make effectivedecisions regarding the outcome of a flight, you must have an understand-ing of your limitations. Your performance during aflight is affected by many factors, such as health,recency of experience, knowledge, skill level, andattitude.

Figure 14-4. Statistical data can identify operations that havemore risk.

Figure 14-5. Prior to flight, you should assess your fitness, just asyou evaluate the aircraft’s airworthiness.

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Exercising good judgment begins prior to takingthe controls of an aircraft. Often, pilots thor-oughly check their aircraft to determine airworthi-ness, yet do not evaluate their own fitness forflight. Just as a checklist is used when preflight-ing an aircraft, a personal checklist based onsuch factors as experience, currency, and com-fort level can help determine if you are preparedfor a particular flight. Specifying when refreshertraining should be accomplished and designatingweather minimums, which may be higher thanthose listed in Title 14 of the Code of FederalRegulations (14 CFR) part 91, are elements thatmay be included on a personal checklist. In addi-tion to a review of personal limitations, youshould use the I’M SAFE Checklist to furtherevaluate your fitness for flight. [Figure 14-5]

RECOGNIZING HAZARDOUS ATTITUDESBeing fit to fly depends on more than just yourphysical condition and recency of experience. Forexample, attitude affects the quality of your deci-sions. Attitude can be defined as a personal moti-vational predisposition to respond to persons,situations, or events in a given manner. Studieshave identified five hazardous attitudes that caninterfere with your ability to make sound decisionsand exercise authority properly. [Figure 14-6]

Hazardous attitudes can lead to poor decisionmaking and actions that involve unnecessary risk.You must examine your decisions carefully toensure that your choices have not been influ-enced by hazardous attitudes, and you must be familiar with positive

Figure 14-6. You should examine your decisions carefully to ensure that your choices have not been influenced by a hazardous attitude.

Figure 14-7. You must be able to identify hazardous attitudes andapply the appropriate antidote when needed.

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alternatives to counteract the hazardous attitudes.These substitute attitudes are referred to as anti-dotes. During a flight operation, it is important tobe able to recognize a hazardous attitude, cor-rectly label the thought, and then recall its anti-dote. [Figure 14-7]

STRESS MANAGEMENTEveryone is stressed to some degree all the time.A certain amount of stress is good since it keeps aperson alert and prevents complacency. However,effects of stress are cumulative and, if not copedwith adequately, they eventually add up to an intol-erable burden. Performance generally increaseswith the onset of stress, peaks, and then begins tofall off rapidly as stress levels exceed a person’sability to cope. The ability to make effective deci-sions during flight can be impaired by stress.Factors, referred to as stressors, can increase apilot’s risk of error in the cockpit. [Figure 14-8]

There are several techniques to help manage theaccumulation of life stresses and prevent stressoverload. For example, including relaxation timein a busy schedule and maintaining a program ofphysical fitness can help reduce stress levels.Learning to manage time more effectively canhelp you avoid heavy pressures imposed by get-ting behind schedule and not meeting deadlines.Take an assessment of yourself to determine yourcapabilities and limitations and then set realisticgoals. In addition, avoiding stressful situationsand encounters can help you cope with stress.

USE OF RESOURCESTo make informed decisions during flight opera-tions, you must be aware of the resources foundboth inside and outside the cockpit. Since usefultools and sources of information may not alwaysbe readily apparent, learning to recognize these

resources is an essential part of ADM training.Resources must not only be identified, but youmust develop the skills to evaluate whether youhave the time to use a particular resource and theimpact that its use will have upon the safety offlight. For example, the assistance of ATC may bevery useful if you are lost. However, in an emer-gency situation when action needs be takenquickly, time may not be available to contact ATCimmediately.

INTERNAL RESOURCESInternal resources are found in the cockpit duringflight. Since some of the most valuable internalresources are ingenuity, knowledge, and skill, youcan expand cockpit resources immensely byimproving these capabilities. This can be accom-plished by frequently reviewing flight informationpublications, such as the CFRs and the AIM, aswell as by pursuing additional training.

A thorough understanding of all the equipmentand systems in the aircraft is necessary to fully uti-lize all resources. For example, advanced naviga-tion and autopilot systems are valuable resources.However, if pilots do not fully understand how touse this equipment, or they rely on it so much thatthey become complacent, it can become a detriment to safeflight.

Checklists are essential cockpit resources for ver-ifying that the aircraft instruments and systems arechecked, set, and operating properly, as well asensuring that the proper procedures are per-formed if there is a system malfunction or in-flightemergency. In addition, the FAA-approved rotor-craft flight manual, which is required to be carriedon board the aircraft, is essential for accurate flightplanning and for resolving in-flight equipment mal-

Figure 14-8. The three types of stressors that can affect a pilot’s performance.

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functions. Other valuable cockpit resourcesinclude current aeronautical charts, and publica-

tions, such as the Airport/Facility Directory.

Passengers can also be a valuable resource.Passengers can help watch for traffic and may beable to provide information in an irregular situa-tion, especially if they are familiar with flying. Astrange smell or sound may alert a passenger toa potential problem. As pilot in command, youshould brief passengers before the flight to makesure that they are comfortable voicing any con-cerns.

EXTERNAL RESOURCESPossibly the greatest external resources duringflight are air traffic controllers and flight servicespecialists. ATC can help decrease pilot workloadby providing traffic advisories, radar vectors, andassistance in emergency situations. Flight servicestations can provide updates on weather, answerquestions about airport conditions, and may offerdirection-finding assistance. The services pro-vided by ATC can be invaluable in enabling you tomake informed in-flight decisions.

WORKLOAD MANAGEMENTEffective workload management ensures thatessential operations are accomplished by plan-ning, prioritizing, and sequencing tasks to avoidwork overload. As experience is gained, youlearn to recognize future workload requirementsand can prepare for high workload periods dur-ing times of low workload. Reviewing the appro-priate chart and setting radio frequencies well inadvance of when they are needed helps reduce

workload as your flight nears the airport. In addi-tion, you should listen to ATIS, ASOS, or AWOS,if available, and then monitor the tower fre-quency or CTAF to get a good idea of what trafficconditions to expect. Checklists should be per-formed well in advance so there is time to focuson traffic and ATC instructions. These proce-dures are especially important prior to entering ahigh-density traffic area, such as Class B air -space.

To manage workload, items should be prioritized.For example, during any situation, and especiallyin an emergency, you should remember thephrase “aviate, navigate, and communicate.” Thismeans that the first thing you should do is makesure the helicopter is under control. Then beginflying to an acceptable landing area. Only after thefirst two items are assured, should you try to com-municate with anyone.

Another important part of managing workload isrecognizing a work overload situation. The firsteffect of high workload is that you begin to workfaster. As workload increases, attention cannot bedevoted to several tasks at one time, and you maybegin to focus on one item. When you becometask saturated, there is no awareness of inputsfrom various sources, so decisions may be madeon incomplete information, and the possibility oferror increases. [Figure 14-9]

When becoming overloaded, you should stop,think, slow down, and prioritize. It is important thatyou understand options that may be available todecrease workload. For example, tasks, such aslocating an item on a chart or setting a radio fre-quency, may be delegated to another pilot or pas-senger, an autopilot, if available, may be used, orATC may be enlisted to provide assistance.

SITUATIONAL AWARENESSSituational awareness is the accurate perceptionof the operational and environmental factors thataffect the aircraft, pilot, and passengers during aspecific period of time. Maintaining situationalawareness requires an understanding of the rel-ative significance of these factors and their futureimpact on the flight. When situationally aware,you have an overview of the total operation andare not fixated on one perceived significant fac-tor. Some of the elements inside the aircraft to beconsidered are the status of aircraft systems, youas the pilot, and passengers. In addition, anawareness of the environmental conditions of theflight, such as spatial orientation of the helicop-

Figure 14-9. Accidents often occur when flying task requirementsexceed pilot capabilities. The difference between these two fac-tors is called the margin of safety. Note that in this idealized exam-ple, the margin of safety is minimal during the approach andlanding. At this point, an emergency or distraction could overtaxpilot capabilities, causing an accident.

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ter, and its relationship to terrain, traffic, weather,and airspace must be maintained.

To maintain situational awareness, all of the skillsinvolved in aeronautical decision making areused. For example, an accurate perception ofyour fitness can be achieved through self-assess-ment and recognition of hazardous attitudes. Aclear assessment of the status of navigationequipment can be obtained through workloadmanagement, and establishing a productive relationship with ATC can be accomplished byeffective resource use.

OBSTACLES TO MAINTAINING SITUATIONALAWARENESSFatigue, stress, and work overload can cause youto fixate on a single perceived important itemrather than maintaining an overall awareness ofthe flight situation. A contributing factor in manyaccidents is a distraction that diverts the pilot’s attention frommonitoring the instruments or scanning outsidet h eaircraft. Many cockpit distractions begin as aminor problem, such as a gauge that is not read-ing correctly, but result in accidents as the pilotdiverts attention to the perceived problem andneglects to properly control the aircraft.

Complacency presents another obstacle to main-taining situational awareness. When activitiesbecome routine, you may have a tendency torelax and not put as much effort into performance.Like fatigue, complacency reduces your effective-ness in the cockpit. However, complacency isharder to recognize than fatigue, since everythingis perceived to be progressing smoothly. Forexample, you have just dropped off another groupof fire fighters for the fifth time that day. Withoutthinking, you hastily lift the helicopter off theground, not realizing that one of the skids is stuckbetween two rocks. The result is dynamic rolloverand a destroyed helicopter.

OPERATIONAL PITFALLSThere are a number of classic behavioral trapsinto which pilots have been known to fall. Pilots,particularly those with considerable experience,as a rule, always try to complete a flight asplanned, please passengers, and meet sched-ules. The basic drive to meet or exceed goals canhave an adverse effect on safety, and can imposean unrealistic assessment of piloting skills understressful conditions. These tendencies ultimatelymay bring about practices that are dangerous andoften illegal, and may lead to a mishap. You willdevelop awareness and learn to avoid many ofthese operational pitfalls through effective ADMtraining. [Figure 14-10]

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Figure 14-10. All experienced pilots have fallen prey to, or have been tempted by, one or more of these tendencies in their flying careers.

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craft have used the free spinning rotor to attainperformance not available in the pure helicopter.The “gyrodyne” is a hybrid rotorcraft that is capa-ble of hovering and yet cruises in autorotation.The first successful example of this type of aircraftwas the British Fairy Rotodyne, certificated to theTransport Category in 1958. During the 1960s and1970s, the popularity of gyroplanes increased withthe certification of the McCulloch J-2 andUmbaugh. The latter becoming the Air & Space18A.

There are several aircraft under developmentusing the free spinning rotor to achieve rotary wingtakeoff performance and fixed wing cruise speeds.The gyroplane offers inherent safety, simplicity ofoperation, and outstanding short field point-to-point capability.

TYPES OF GYROPLANESBecause the free spinning rotor does notrequire an antitorque device, a single rotor isthe predominate configuration. Counter-rotatingblades do not offer any particular advantage.The rotor system used in a gyroplane may haveany number of blades, but the most popular arethe two and three blade systems. Propulsion forgyroplanes may be either tractor or pusher,meaning the engine may be mounted on thefront and pull the aircraft, or in the rear, pushingit through the air. The powerplant itself may beeither reciprocating or turbine. Early gyroplaneswere often a derivative of tractor configured air-

January 9th, 1923, marked the first officiallyobserved flight of an autogyro. The aircraft,designed by Juan de la Cierva, introduced rotortechnology that made forward flight in a rotorcraftpossible. Until that time, rotary-wing aircraftdesigners were stymied by the problem of a rollingmoment that was encountered when the aircraftbegan to move forward. This rolling moment wasthe product of airflow over the rotor disc, causingan increase in lift of the advancing blade anddecrease in lift of the retreating blade. Cierva’ssuccessful design, the C.4, introduced the articu-lated rotor, on which the blades were hinged andallowed to flap. This solution allowed the advanc-ing blade to move upward, decreasing angle ofattack and lift, while the retreating blade wouldswing downward, increasing angle of attack andlift. The result was balanced lift across the rotordisc regardless of airflow. This breakthrough wasinstrumental in the success of the modern helicop-ter, which was developed over 15 years later. (Formore information on dissymmetry of lift, refer toChapter 3—Aerodynamics of Flight.) On April 2,1931, the Pitcairn PCA-2 autogyro was grantedType Certificate No. 410 and became the firstrotary wing aircraft to be certified in the UnitedStates. The term “autogyro” was used to describethis type of aircraft until the FAA later designatedthem “gyroplanes.”

By definition, the gyroplane is an aircraft thatachieves lift by a free spinning rotor. Several air-

Figure 15-1. The gyroplane may have wings, be either tractor or pusher configured, and could be turbine or propeller powered. Picturedare the Pitcairn PCA-2 Autogyro (left) and the Air & Space 18A gyroplane.

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planes with the rotor either replacing the wingor acting in conjunction with it. However, thepusher configuration is generally more maneu-verable due to the placement of the rudder inthe propeller slipstream, and also has theadvantage of better visibility for the pilot.[Figure 15-1]

When direct control of the rotor head was per-fected, the jump takeoff gyroplane was devel-oped. Under the proper conditions, thesegyroplanes have the ability to lift off vertically andtransition to forward flight. Later developmentshave included retaining the direct control rotorhead and utilizing a wing to unload the rotor,which results in increased forward speed.

COMPONENTSAlthough gyroplanes are designed in a variety ofconfigurations, for the most part the basic compo-nents are the same. The minimum componentsrequired for a functional gyroplane are an airframe,a powerplant, a rotor system, tail surfaces, and

Direct Control—The capacity forthe pilot to maneuver the aircraftby tilting the rotor disc and, onsome gyroplanes, affect changesin pitch to the rotor blades. Theseequate to cyclic and collectivecontrol, which were not availablein earlier autogyros.

Unload—To reduce the compo-nent of weight supported by therotor system.

Prerotate—Spinning a gyroplanerotor to sufficient r.p.m. prior toflight.

landing gear. [Figure 15-2] An optional componentis the wing, which is incorporated into somedesigns for specific performance objectives.

AIRFRAMEThe airframe provides the structure to which allother components are attached. Airframes may bewelded tube, sheet metal, composite, or simplytubes bolted together. A combination of construc-tion methods may also be employed. The air-frames with the greatest strength-to-weight ratiosare a carbon fiber material or the welded tubestructure, which has been in use for a number ofyears.

POWERPLANTThe powerplant provides the thrust necessary forforward flight, and is independent of the rotor sys-tem while in flight. While on the ground, the enginemay be used as a source of power to prerotatethe rotor system. Over the many years of gyro-plane development, a wide variety of enginetypes have been adapted to the gyroplane.Automotive, marine, ATV, and certificated aircraft engines have all been used in various gyroplane designs. Certificated gyroplanes arerequired to use FAA certificated engines. The costof a new certificated aircraft engine is greater thanthe cost of nearly any other new engine. Thisadded cost is the primary reason other types ofengines are selected for use in amateur built gyro-planes.

ROTOR SYSTEMThe rotor system provides lift and control for thegyroplane. The fully articulated and semi-rigid tee-tering rotor systems are the most common. Theseare explained in-depth in Chapter 5—Main RotorSystem. The teeter blade with hub tilt control ismost common in homebuilt gyroplanes. This sys-tem may also employ a collective control tochange the pitch of the rotor blades. With suffi -cient blade inertia and collective pitch change,jump takeoffs can be accomplished.

TAIL SURFACESThe tail surfaces provide stability and control in thepitch and yaw axes. These tail surfaces are similar

Figure 15-2. Gyroplanes typically consist of five major compo-nents. A sixth, the wing, is utilized on some designs.

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to an airplane empennage and may be comprisedof a fin and rudder, stabilizer and elevator. An aftmounted duct enclosing the propeller and rudderhas also been used. Many gyroplanes do not incor-porate a horizontal tail surface.

On some gyroplanes, especially those with anenclosed cockpit, the yaw stability is marginal dueto the large fuselage side area located ahead ofthe center of gravity. The additional vertical tailsurface necessary to compensate for this instabil-ity is difficult to achieve as the confines of the rotortilt and high landing pitch attitude limits the avail-able area. Some gyroplane designs incorporatemultiple vertical stabilizers and rudders to addadditional yaw stability.

LANDING GEARThe landing gear provides the mobility while on theground and may be either conventional or tricycle.

Conventional gear consists of two main wheels,and one under the tail. The tricycle configurationalso uses two mains, with the third wheel under thenose. Early autogyros, and several models of gyro-planes, use conventional gear, while most of thelater gyroplanes incorporate tricycle landing gear.As with fixed wing aircraft, the gyroplane landinggear provides the ground mobility not found inmost helicopters.

WINGSWings may or may not comprise a componentof the gyroplane. When used, they provideincreased performance, increased storagecapacity, and increased stability. Gyroplanesare under development with wings that arecapable of almost completely unloading therotor system and carrying the entire weight ofthe aircraft. This will allow rotary wing takeoffperformance with fixed wing cruise speeds.[Figure 15-3]

Figure 15-3. The CarterCopter uses wings to enhance per-formance.

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Helicopters and gyroplanes both achieve liftthrough the use of airfoils, and, therefore, many ofthe basic aerodynamic principles governing theproduction of lift apply to both aircraft. These con-cepts are explained in depth in Chapter 2—General Aerodynamics, and constitute thefoundation for discussing the aerodynamics of agyroplane.

AUTOROTATIONA fundamental difference between helicopters andgyroplanes is that in powered flight, a gyroplanerotor system operates in autorotation. This meansthe rotor spins freely as a result of air flowing upthrough the blades, rather than using enginepower to turn the blades and draw air from above.[Figure 16-1] Forces are created during autorota-tion that keep the rotor blades turning, as well ascreating lift to keep the aircraft aloft.Aerodynamically, the rotor system of a gyroplanein normal flight operates like a helicopter rotor dur-ing an engine-out forward autorotative descent.

VERTICAL AUTOROTATIONDuring a vertical autorotation, two basic compo-nents contribute to the relative wind striking therotor blades. [Figure 16-2] One component, the

upward flow of air through the rotor system,remains relatively constant for a given flight condi-tion. The other component is the rotational airflow,which is the wind velocity across the blades asthey spin. This component varies significantlybased upon how far from the rotor hub it is meas-ured. For example, consider a rotor disc that is 25feet in diameter operating at 300 r.p.m. At a pointone foot outboard from the rotor hub, the bladesare traveling in a circle with a circumference of 6.3feet. This equates to 31.4 feet per second (f.p.s.),or a rotational blade speed of 21 m.p.h. At the

Figure 16-1. Airflow through the rotor system on a gyroplane is reversed from that on a powered helicopter. This airflow is the mediumthrough which power is transferred from the gyroplane engine to the rotor system to keep it rotating.

Figure 16-2. In a vertical autorotation, the wind from the rotation of the blade combines with the upward airflow to producethe resultant relative wind striking the airfoil.

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blade tips, the circumference of the circleincreases to 78.5 feet. At the same operatingspeed of 300 r.p.m., this creates a blade tip speedof 393 feet per second, or 267 m.p.h. The result isa higher total relative wind, striking the blades at alower angle of attack. [Figure 16-3]

ROTOR DISC REGIONSAs with any airfoil, the lift that is created by rotorblades is perpendicular to the relative wind.Because the relative wind on rotor blades inautorotation shifts from a high angle of attackinboard to a lower angle of attack outboard, the liftgenerated has a higher forward component closerto the hub and a higher vertical component towardthe blade tips. This creates distinct regions of therotor disc that create the forces necessary forflight in autorotation. [Figure 16-4] The autorota-tive region, or driving region, creates a total aero-dynamic force with a forward component thatexceeds all rearward drag forces and keeps theblades spinning. The propeller region, or drivenregion, generates a total aerodynamic force witha higher vertical component that allows the gyro-plane to remain aloft. Near the center of the rotordisc is a stall region where the rotational compo-nent of the relative wind is so low that the result-ing angle of attack is beyond the stall limit of theairfoil. The stall region creates drag against thedirection of rotation that must be overcome by theforward acting forces generated by the drivingregion.

AUTOROTATION IN FORWARD FLIGHTAs discussed thus far, the aerodynamics ofautorotation apply to a gyroplane in a vertical

descent. Because gyroplanes are normally oper-ated in forward flight, the component of relative

Figure 16-3. Moving outboard on the rotor blade, the rotational velocity increasingly exceeds the upward component of airflow, resultingin a higher relative wind at a lower angle of attack.

Figure 16-4. The total aerodynamic force is aft of the axis of rota-tion in the driven region and forward of the axis of rotation in thedriving region. Drag is the major aerodynamic force in the stallregion. For a complete depiction of force vectors during a verticalautorotation, refer to Chapter 3—Aerodynamics of Flight(Helicopter), Figure 3-22.

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wind striking the rotor blades as a result of forwardspeed must also be considered. This componenthas no effect on the aerodynamic principles thatcause the blades to autorotate, but causes a shiftin the zones of the rotor disc.

As a gyroplane moves forward through the air, theforward speed of the aircraft is effectively addedto the relative wind striking the advancing blade,and subtracted from the relative wind striking theretreating blade. To prevent uneven lifting forceson the two sides of the rotor disc, the advancingblade teeters up, decreasing angle of attack andlift, while the retreating blade teeters down,increasing angle of attack and lift. (For a completediscussion on dissymmetry of lift, refer to Chapter

3—Aerodynamics of Flight.) The lower angles ofattack on the advancing blade cause more of theblade to fall in the driven region, while higherangles of attack on the retreating blade causemore of the blade to be stalled. The result is a shiftin the rotor regions toward the retreating side ofthe disc to a degree directly related to the forwardspeed of the aircraft. [Figure 16-5]

REVERSE FLOWOn a rotor system in forward flight, reverse flowoccurs near the rotor hub on the retreating side ofthe rotor disc. This is the result of the forwardspeed of the aircraft exceeding the rotationalspeed of the rotor blades. For example, two feetoutboard from the rotor hub, the blades travel in acircle with a circumference of 12.6 feet. At a rotorspeed of 300 r.p.m., the blade speed at the two-

foot station is 42 m.p.h. If the aircraft is being oper-ated at a forward speed of 42 m.p.h., the forwardspeed of the aircraft essentially negates the rota-tional velocity on the retreating blade at the two-foot station. Moving inboard from the two-footstation on the retreating blade, the forward speedof the aircraft increasingly exceeds the rotational

velocity of the blade. This causes the airflow toactually strike the trailing edge of the rotor blade,with velocity increasing toward the rotor hub.[Figure 16-6] The size of the area that experiencesreverse flow is dependent primarily on the forwardspeed of the aircraft, with higher speed creating alarger region of reverse flow. To some degree, theoperating speed of the rotor system also has aneffect on the size of the region, with systems oper-ating at lower r.p.m. being more susceptible toreverse flow and allowing a greater portion of theblade to experience the effect.

RETREATING BLADE STALLThe retreating blade stall in a gyroplane differsfrom that of a helicopter in that it occurs outboardfrom the rotor hub at the 20 to 40 percent positionrather than at the blade tip. Because the gyro-plane is operating in autorotation, in forward flightthere is an inherent stall region centered inboard

Figure 16-5. Rotor disc regions in forward autorotative flight.

Figure 16-6. An area of reverse flow forms on the retreating bladein forward flight as a result of aircraft speed exceeding blade rota-tional speed.

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given airfoil produces the most lift for the leastdrag. However, the airfoil of a rotor blade does notoperate at this efficient angle throughout the manychanges that occur in each revolution. Also, therotor system must remain in the autorotative (low)pitch range to continue turning in order to gener-ate lift.

Some gyroplanes use small wings for creating liftwhen operating at higher cruise speeds. The liftprovided by the wings can either supplement orentirely replace rotor lift while creating much lessinduced drag.

ROTOR DRAGTotal rotor drag is the summation of all the dragforces acting on the airfoil at each blade position.Each blade position contributes to the total dragaccording to the speed and angle of the airfoil atthat position. As the rotor blades turn, rapidchanges occur on the airfoils depending on posi-tion, rotor speed, and aircraft speed. A change inthe angle of attack of the rotor disc can effect arapid and substantial change in total rotor drag.

Rotor drag can be divided into components ofinduced drag and profile drag. The induced dragis a product of lift, while the profile drag is a func-tion of rotor r.p.m. Because induced drag is aresult of the rotor providing lift, profile drag can beconsidered the drag of the rotor when it is not pro-ducing lift. To visualize profile drag, consider thedrag that must be overcome to prerotate the rotor

on the retreating blade. [Refer to figure 16-5] Asforward speed increases, the angle of attack onthe retreating blade increases to prevent dissym-metry of lift and the stall region moves further outboard on the retreating blade. Because thestalled portion of the rotor disc is inboard ratherthan near the tip, as with a helicopter, less force iscreated about the aircraft center of gravity. Theresult is that you may feel a slight increase invibration, but you would not experience a largepitch or roll tendency.

ROTOR FORCEAs with any heavier than air aircraft, the fourforces acting on the gyroplane in flight are lift,weight, thrust and drag. The gyroplane derives liftfrom the rotor and thrust directly from the enginethrough a propeller. [Figure 16-7]

The force produced by the gyroplane rotor may bedivided into two components; rotor lift and rotordrag. The component of rotor force perpendicularto the flight path is rotor lift, and the component ofrotor force parallel to the flight path is rotor drag.To derive the total aircraft drag reaction, you mustalso add the drag of the fuselage to that of therotor.

ROTOR LIFTRotor lift can most easily be visualized as the liftrequired to support the weight of the aircraft.When an airfoil produces lift, induced drag is pro-duced. The most efficient angle of attack for a

Figure 16-7. Unlike a helicopter, in forward powered flight the resultant rotor force of a gyroplane acts in a rearward direction.

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system to flight r.p.m. while the blades are pro-ducing no lift. This can be achieved with a rotorsystem having a symmetrical airfoil and a pitchchange capability by setting the blades to a 0°angle of attack. A rotor system with an asymmetri-cal airfoil and a built in pitch angle, which includesmost amateur-built teeter-head rotor systems,cannot be prerotated without having to overcomethe induced drag created as well.

THRUSTThrust in a gyroplane is defined as the componentof total propeller force parallel to the relative wind.As with any force applied to an aircraft, thrust actsaround the center of gravity. Based upon wherethe thrust is applied in relation to the aircraft cen-ter of gravity, a relatively small component may beperpendicular to the relative wind and can be con-sidered to be additive to lift or weight.

Figure 16-8. Engine torque applied to the propeller has an equaland opposite reaction on the fuselage, deflecting it a few degreesout of the vertical plane in flight.

Pendular Action—The lateral orlongitudinal oscillation of thefuselage due to it being sus-pended from the rotor system. Itis similar to the action of a pen-dulum. Pendular action is furtherdiscussed in Chapter 3—Aerodynamics of Flight.

In flight, the fuselage of a gyroplane essentiallyacts as a plumb suspended from the rotor, and assuch, it is subject to pendular action in the sameway as a helicopter. Unlike a helicopter, however,thrust is applied directly to the airframe of a gyro-plane rather than being obtained through the rotorsystem. As a result, different forces act on a gyro-plane in flight than on a helicopter. Engine torque,for example, tends to roll the fuselage in the direc-tion opposite propeller rotation, causing it to bedeflected a few degrees out of the vertical plane.[Figure 16-8] This slight “out of vertical” conditionis usually negligible and not considered relevantfor most flight operations.

STABILITYStability is designed into aircraft to reduce pilotworkload and increase safety. A stable aircraft,such as a typical general aviation training air-plane, requires less attention from the pilot tomaintain the desired flight attitude, and will evencorrect itself if disturbed by a gust of wind or otheroutside forces. Conversely, an unstable aircraftrequires constant attention to maintain control ofthe aircraft.

There are several factors that contribute to thestability of a gyroplane. One is the location of theh o r i z o n t a lstabilizer. Another is the location of the fuselagedrag in relation to the center of gravity. A third ist h einertia moment around the pitch axis, while afourth is the relation of the propeller thrust line tothe vertical location of the center of gravity (CG).However, the one that is probably the most criticalis the relation of the rotor force line to the horizon-tal location of the center of gravity.

HORIZONTAL STABILIZERA horizontal stabilizer helps in longitudinal stabil-ity, with its efficiency greater the further it is fromt h ecenter of gravity. It is also more efficient at higher airspeeds because lift is proportional to the squareof the airspeed. Since the speed of a gyroplane isnot very high, manufacturers can achieve thedesired stability by varying the size of the horizon-tal stabilizer, changing the distance it is from thecenter of gravity, or by placing it in the propellerslipstream.

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FUSELAGE DRAG(CENTER OF PRESSURE)If the location, where the fuselage drag or centerof pressure forces are concentrated, is behindthe CG, the gyroplane is considered more stable.This is especially true of yaw stability around thevertical axis. However, to achieve this condition,there must be a sufficient vertical tail surface. Inaddition, the gyroplane needs to have a bal-anced longitudinal center of pressure so there issufficient cyclic movement toprevent the nose from tucking under or lifting, aspressure builds on the frontal area of the gyro-plane as airspeed increases.

PITCH INERTIAWithout changing the overall weight and center ofgravity of a gyroplane, the further weights areplaced from the CG, the more stable the gyro-plane. For example, if the pilot's seat could bemoved forward from the CG, and the enginemoved aft an amount, which keeps the center ofgravity in the same location, the gyroplanebecomes more stable. A tightrope walker appliesthis same principle when he uses a long pole tobalance himself.

PROPELLER THRUST LINEConsidering just the propeller thrust line by itself,if the thrust line is above the center of gravity, thegyroplane has a tendency to pitch nose downwhen power is applied, and to pitch nose up whenpower is removed. The opposite is true when thepropeller thrust line is below the CG. If the thrustline goes through the CG or nearly so there is notendency for the nose to pitch up or down. [Figure16-9]

ROTOR FORCEBecause some gyroplanes do not have horizontalstabilizers, and the propeller thrust lines are differ-ent, gyroplane manufacturers can achieve thedesired stability by placing the center of gravity infront of or behind the rotor force line. [Figure 16-10]

Suppose the CG is located behind the rotor forceline in forward flight. If a gust of wind increasesthe angle of attack, rotor force increases. There isalso an increase in the difference between the lift

Figure 16-9. A gyroplane which has the propeller thrust line above the center of gravity is often referred to as a low profile gyroplane. Onethat has the propeller thrust line below or at the CG is considered a high profile gyroplane.

Figure 16-10. If the CG is located in front of the rotor force line, the gyroplane is more stable than if the CG is located behind the rotorforce line.

Blade Flapping—The upward or downward movement of the rotor-blades during rotation.

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Due to rudimentary flight control systems, early gyro-planes suffered from limited maneuverability. As tech-nology improved, greater control of the rotorsystem and more effective control surfaces weredeveloped. The modern gyroplane, while continu-ing to maintain an element of simplicity, nowenjoys a high degree of maneuverability as aresult of these improvements.

CYCLIC CONTROLThe cyclic control provides the means wherebyyou are able to tilt the rotor system to provide thedesired results. Tilting the rotor system providesall control for climbing, descending, and bankingthe gyroplane. The most common method totransfer stick movement to the rotor head isthrough push-pull tubes or flex cables. [Figure 17-1] Some gyroplanes use a direct overhead stickattachment rather than a cyclic, where a rigid con-trol is attached to the rotor hub and descends overand in front of the pilot. [Figure 17-2] Becauseof the nature of the direct attachment, controlinputs with this system are reversed from thoseused with a cyclic. Pushing forward on the controlcauses the rotor disc to tilt back and the gyroplaneto climb, pulling back on the control initiates adescent. Bank commands are reversed in thesame way.

THROTTLEThe throttle is conventional to most powerplants,and provides the means for you to increase ordecrease engine power and thus, thrust.

Figure 17-1. A common method of transferring cyclic control inputs to the rotor head is through the use of push-pull tubes, locatedoutboard of the rotor mast pictured on the right.

Figure 17-2. The direct overhead stick attachment has beenused for control of the rotor disc on some gyroplanes.

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Depending on how the control is designed, con-trol movement may or may not be proportionalto engine power. With many gyroplane throttles,50 percent of the control travel may equate to 80or 90 percent of available power. This varyingdegree of sensitivity makes it necessary for you tobecome familiar with the unique throttle characteristics and engine responses for a particu-lar gyroplane.

RUDDERThe rudder is operated by foot pedals in the cock-p i tand provides a means to control yaw movementof the aircraft. [Figure 17-3] On a gyroplane, thiscontrol is achieved in a manner more similar to therudder of an airplane than to the antitorque pedalsof a helicopter. The rudder is used to maintaincoordinated flight, and at times may also requireinputs to compensate for propeller torque. Rudder sensitivity and effective-ness are directly proportional to the velocity of air-flow over the rudder surface. Consequently, manyg y r o p l a n e

rudders are located in the propeller slipstream and provide excellent control while the engine is devel-oping thrust. This type of rudder configuration,however, is less effective and requires greaterdeflection when the engine is idled or stopped.

HORIZONTAL TAIL SURFACESThe horizontal tail surfaces on most gyroplanesa r enot controllable by the pilot. These fixed sur-faces, or stabilizers, are incorporated into gyro-plane designs to increase the pitch stability of theaircraft. Some gyroplanes use very little, if any,horizontal surface. This translates into less stabil-ity, but a higher degree of maneuverability. Whenused, a moveable horizontal surface, or elevator,adds additional pitch control of the aircraft. Onearly tractor configured gyroplanes, the elevatorserved an additional function of deflecting the pro-peller slipstream up and through the rotor to assistin prerotation.

Figure 17-3. Foot pedals provide rudder control and operation is similar to that of an airplane.

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attachment to the rotor head by the teeter bolt.The rotor head is comprised of a bearing block inwhich the bearing is mounted and onto which thetower plates are attached. The spindle (com-monly, a vertically oriented bolt) attaches therotating portion of the head to the non-rotating

torque tube. The torque tube is mounted to theairframe through attachments allowing both lat-eral and longitudinal movement. This allows themovement through which control is achieved.

Coning Angle—An angulardeflection of the rotor bladesupward from the rotor hub.

Undersling—A design charac-teristic that prevents the dis-tance between the rotor mastaxis and the center of mass ofeach rotor blade from changingas the blades teeter. This pre-cludes Coriolis Effect from act-ing on the speed of the rotorsystem. Undersling is furtherexplained in Chapter 3—Aerodynamics of Flight, CoriolisEffect (Law of Conservation ofAngular Momentum).

Gyroplanes are available in a wide variety ofdesigns that range from amateur built to FAA-cer-tificated aircraft. Similarly, the complexity of thesystems integrated in gyroplane design cover abroad range. To ensure the airworthiness of youraircraft, it is important that you thoroughly under-stand the design and operation of each systememployed by your machine.

PROPULSION SYSTEMSMost of the gyroplanes flying today use a recipro-cating engine mounted in a pusher configurationthat drives either a fixed or constant speed propeller.The engines used in amateur-built gyroplanes arenormally proven powerplants adapted from automo-tive or other uses. Some amateur-built gyroplanesuse FAA-certificated aircraft engines and propellers.Auto engines, along with some of the other power-plants adapted to gyroplanes, operate at a highr.p.m., which requires the use of a reduction unit tolower the output to efficient propeller speeds.

Early autogyros used existing aircraft engines,which drove a propeller in the tractor configura-tion. Several amateur-built gyroplanes still usethis propulsion configuration, and may utilize acertificated or an uncertificated engine. Althoughnot in use today, turboprop and pure jet enginescould also be used for the propulsion of a gyro-plane.

ROTOR SYSTEMSSEMIRIGID ROTOR SYSTEMAny rotor system capable of autorotation may beutilized in a gyroplane. Because of its simplicity, themost widely used system is the semirigid, teeter-head system. This system is found in most ama-teur-built gyroplanes. [Figure 18-1] In this system,the rotor head is mounted on a spindle, whichmay be tilted for control. The rotor blades areattached to a hub bar that may or may not haveadjustments for varying the blade pitch. A coningangle, determined by projections of blade weight,rotor speed, and load to be carried, is built intothe hub bar. This minimizes hub bar bendingmoments and eliminates the need for a coninghinge, which is used in more complex rotor sys-tems. A tower block provides the undersling and

Figure 18-1. The semirigid, teeter-head system is found on mostamateur-built gyroplanes. The rotor hub bar and blades are per-mitted to tilt by the teeter bolt.

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FULLY ARTICULATED ROTOR SYSTEM The fully articulated rotor system is found on somegyroplanes. As with helicopter-type rotor systems,the articulated rotor system allows the manipula-tion of rotor blade pitch while in flight. This systemis significantly more complicated than the teeter-head, as it requires hinges that allow each rotorblade to flap, feather, and lead or lag independ-ently. [Figure 18-2] When used, the fully articulatedrotor system of a gyroplane is very similar to thoseused on helicopters, which is explained in depth inChapter 5—Helicopter Systems, Main RotorSystems. One major advantage of using a fully artic-ulated rotor in gyroplane design is that it usuallyallows jump takeoff capability. Rotor characteristics

required for a successful jump takeoff must includea method of collective pitch change, a blade withsufficient inertia, and a prerotation mechanismcapable of approximately 150 percent of rotor flightr.p.m.

Incorporating rotor blades with high inertia poten-tial is desirable in helicopter design and is essen-tial for jump takeoff gyroplanes. A rotor hub designallowing the rotor speed to exceed normal flightr.p.m. by over 50 percent is not found in helicopters, and predi-cates a rotor head design particular to the jumpt a k e o f fgyroplane, yet very similar to that of the helicop-ter.

PREROTATORPrior to takeoff, the gyroplane rotor must firstachieve a rotor speed sufficient to create thenecessary lift. This is accomplished on verybasic gyroplanes by initially spinning the bladesby hand. The aircraft is then taxied with the rotordisc tilted aft, allowing airflow through the system

to accelerate it to flight r.p.m. More advancedgyroplanes use a prerotator, which provides amechanical means to spin the rotor. Many pre-rotators are capable of only achieving a portionof the speed necessary for flight; the remainderis gained by taxiing or during the takeoff roll.Because of the wide variety of prerotation sys-

tems available, you need to become thoroughlyfamiliar with the characteristics and techniquesassociated with your particular system.

MECHANICAL PREROTATORMechanical prerotators typically have clutches orbelts for engagement, a drive train, and may use atransmission to transfer engine power to the rotor.Friction drives and flex cables are used in con-junction with an automotive type bendix and ringgear on many gyroplanes. [Figure 18-3]

The mechanical prerotator used on jump takeoffgyroplanes may be regarded as being similar to thehelicopter main rotor drive train, but only operateswhile the aircraft is firmly on the ground.Gyroplanes do not have an antitorque device like ahelicopter, and ground contact is necessary tocounteract the torque forces generated by the pre-rotation system. If jump takeoff capability isdesigned into a gyroplane, rotor r.p.m. prior toliftoff must be such that rotor energy will supportthe aircraft through the acceleration phase of

Figure 18-2. The fully articulated rotor system enables the pilot toeffect changes in pitch to the rotor blades, which is necessary forjump takeoff capability.

Figure 18-3. The mechanical prerotator used by many gyroplanesuses a friction drive at the propeller hub, and a flexible cable thatruns from the propeller hub to the rotor mast. When engaged, thebendix spins the ring gear located on the rotor hub.

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prerotator utilizes the transmission only while theaircraft is on the ground, allowing the transmis-sion to be disconnected from both the rotor andthe engine while in normal flight.

HYDRAULIC PREROTATORThe hydraulic prerotator found on gyroplanesuses engine power to drive a hydraulic pump,which in turn drives a hydraulic motor attached toan automotive type bendix and ring gear. [Figure18-4] This system also requires that some type of

clutch and pressure regulation be incorporatedinto the design.

ELECTRIC PREROTATORThe electric prerotator found on gyroplanes usesan automotive type starter with a bendix and ringgear mounted at the rotor head to impart torque tothe rotor system. [Figure 18-5] This system has theadvantage of simplicity and ease of operation, butis dependent on having electrical power available.Using a “soft start” device can alleviate the prob-lems associated with the high starting torque ini -tially required to get the rotor system turning. Thisdevice delivers electrical pulses to the starter forapproximately 10 seconds before connecting unin-terrupted voltage.

TIP JETSJets located at the rotor blade tips have been usedin several applications for prerotation, as well as forhover flight. This system has no requirement for atransmission or clutches. It also has the advantageof not imparting torque to the airframe, allowing therotor to be powered in flight to give increased climbrates and even the ability to hover. The major disad-vantage is the noise generated by the jets.Fortunately, tip jets may be shut down while operat-ing in the autorotative gyroplane mode.

INSTRUMENTATIONThe instrumentation required for flight is generallyrelated to the complexity of the gyroplane. Somegyroplanes using air-cooled and fuel/oil-lubricatedengines may have limited instrumentation.

Figure 18-4. This prerotator uses belts at the propeller hub to drive a hydraulic pump, which drives a hydraulic motor on the rotor mast.

Figure 18-5. The electric prerotator is simple and easy to use, butrequires the availability of electrical power.

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ENGINE INSTRUMENTSAll but the most basic engines require monitoringinstrumentation for safe operation. Coolant tem-perature, cylinder head temperatures, oil temper-ature, oil pressure, carburetor air temperature,and exhaust gas temperature are all direct indica-tions of engine operation and may be displayed.Engine power is normally indicated by engine

r.p.m., or by manifold pressure on gyroplanes witha constant speed propeller.

ROTOR TACHOMETERMost gyroplanes are equipped with a rotor r.p.m.indicator. Because the pilot does not normally haved i r e c tcontrol of rotor r.p.m. in flight, this instrument is

most useful on the takeoff roll to determine whenthere is sufficient rotor speed for liftoff. On gyro-planes not equipped with a rotor tachometer, addi-tional piloting skills are required to sense rotorr.p.m. prior to takeoff.

Certain gyroplane maneuvers require you to knowprecisely the speed of the rotor system.Performing a jump takeoff in a gyroplane with col-lective control is one example, as sufficient rotorenergy must be available for the successful out-come of the maneuver. When variable collectiveand a rotor tachometer are used, more efficientrotor operation may be accomplished by using thelowest practical rotor r.p.m. [Figure 18-6]

SLIP/SKID INDICATORA yaw string attached to the nose of the aircraft anda conventional inclinometer are often used in gyro-planes to assist in maintaining coordinated flight.[Figure 18-7]

AIRSPEED INDICATORAirspeed knowledge is essential and is mosteasily obtained by an airspeed indicator that isdesigned for accuracy at low airspeeds. Windspeed indicators have been adapted to manygyroplanes. When no airspeed indicator is used,as in some very basic amateur-built machines, you must have a veryacute sense of “q” (impact air pressure againstyour body).

ALTIMETERFor the average pilot, it becomes increasingly dif-ficult to judge altitude accurately when more thanseveral hundred feet above the ground. A con-

Figure 18-6. A rotor tachometer can be very useful to determinewhen rotor r.p.m. is sufficient for takeoff.

Figure 18-7. A string simply tied near the nose of the gyroplanethat can be viewed from the cockpit is often used to indicate rota-tion about the yaw axis. An inclinometer may also be used.

Figure 18-8. Depending on design, main wheel brakes can beoperated either independently or collectively. They are consider-ably more effective than nose wheel brakes.

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ventional altimeter may be used to provide an alti-tude reference when flying at higher altitudeswhere human perception degrades.

IFR FLIGHT INSTRUMENTATIONGyroplane flight into instrument meteorological con-ditions requires adequate flight instrumentation andnavigational systems, just as in any aircraft. Veryfew gyroplanes have been equipped for this type ofoperation. The majority of gyroplanes do not meetthe stability requirements for single-pilot IFR flight.As larger and more advanced gyroplanes are devel-oped, issues of IFR flight in these aircraft will haveto be addressed.

GROUND HANDLINGThe gyroplane is capable of ground taxiing in amanner similar to that of an airplane. A steerablenose wheel, which may be combined with inde-pendent main wheel brakes, provides the mostcommon method of control. [Figure 18-8] The useof independent main wheel brakes allows differ-ential braking, or applying more braking to onewheel than the other to achieve tight radius turns.On some gyroplanes, the steerable nose wheel isequipped with a foot-operated brake rather thanusing main wheel brakes. One limitation of thissystem is that the nose wheel normally supportsonly a fraction of the weight of the gyroplane,which greatly reduces braking effectiveness.Another drawback is the inability to use differentialbraking, which increases the radius of turns.

The rotor blades demand special considerationduring ground handling, as turning rotor bladescan be a hazard to those nearby. Many gyro-planes have a rotor brake that may be used toslow the rotor after landing, or to secure theblades while parked. A parked gyroplane shouldnever be left with unsecured blades, becauseeven a slight change in wind could cause theblades to turn or flap.

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As with most certificated aircraft manufacturedafter March 1979, FAA-certificated gyroplanes arerequired to have an approved flight manual. Theflight manual describes procedures and limitationsthat must be adhered to when operating the air-craft. Specification for Pilot’s OperatingHandbook, published by the General AviationManufacturers Association (GAMA), provides arecommended format that more recent gyroplaneflight manuals follow. [Figure 19-1]

This format is the same as that used by helicop-ters, which is explained in depth in Chapter 6—Rotorcraft Flight Manual (Helicopter).

Amateur-built gyroplanes may have operating limi-tations but are not normally required to have anapproved flight manual. One exception is anexemption granted by the FAA that allows the com-mercial use of two-place, amateur-built gyroplanes for instruc-tional purposes. One of the conditions of thisexemption is to have an approved flight manualfor the aircraft. This manual is to be used for train-ing purposes, and must be carried in the gyro-plane at all times.

USING THE FLIGHT MANUALThe flight manual is required to be on board theaircraft to guarantee that the information con-tained therein is readily available. For the informa-tion to be of value, you must be thoroughly familiarwith the manual and be able to read and properlyinterpret the various charts and tables.

WEIGHT AND BALANCE SECTIONThe weight and balance section of the flight man-ual contains information essential to the safe oper-ation of the gyroplane. Careful consideration mustbe given to the weight of the passengers, bag-gage, and fuel prior to each flight. In conductingweight and balance computations, many of theterms and procedures are similar to those used inhelicopters. These are further explained inChapter 7—Weight and Balance. In any aircraft,failure to adhere to the weight and balance limi-tations prescribed by the manufacturer can beextremely hazardous.

SAMPLE PROBLEMAs an example of a weight and balance computa-tion, assume a sightseeing flight in a two-seat,tandem-configured gyroplane with two peopleaboard. The pilot, seated in the front, weighs 175pounds while the rear seat passenger weighs 160

Figure 19-1. The FAA-approved flight manual may contain asmany as ten sections, as well as an optional alphabetical index.

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pounds. For the purposes of this example, therewill be no baggage carried. The basic emptyweight of the aircraft is 1,315 pounds with amoment, divided by 1,000, of 153.9 pound-inches.

Using the loading graph [Figure 19-2], themoment/1000 of the pilot is found to be 9.1 pound-inches, and the passenger has a moment/1000 of13.4 pound-inches.

Adding these figures, the total weight of the air-craft for this flight (without fuel) is determined tobe 1,650 pounds with a moment/1000 of 176.4pound-inches. [Figure 19-3]

The maximum gross weight for the sample aircraftis 1,800 pounds, which allows up to 150 poundsto be carried in fuel. For this flight, 18 gallons offuel is deemed sufficient. Allowing six pounds pergallon of fuel, the fuel weight on the aircraft totals108 pounds. Referring again to the loading graph[Figure 19-2], 108 pounds of fuel would have a

moment/1000 of 11.9 pound-inches. This is addedto the previous totals to obtain the total aircraftweight of 1,758 pounds and a moment/1000 of188.3. Locating this point on the center of gravityenvelope chart [Figure 19-4], shows that the load-ing is within the prescribed weight and balancelimits.

PERFORMANCE SECTIONThe performance section of the flight manual con-tains data derived from actual flight testing of theaircraft. Because the actual performance may dif-fer, it is prudent to maintain a margin of safetywhen planning operations using this data.

SAMPLE PROBLEMFor this example, a gyroplane at its maximumgross weight (1,800 lbs.) needs to perform a shortfield takeoff due to obstructions in the takeoff path.Present weather conditions are standard temper-ature at a pressure altitude of 2,000 feet, and thewind is calm. Referring to the appropriate per-formance chart [Figure 19-5], the takeoff distanceto clear a 50-foot obstacle is determined by enter-ing the chart from the left at the pressure altitudeof 2,000 feet. You then proceed horizontally to theright until intersecting the appropriate temperature

Figure 19-3. Loading of the sample aircraft, less fuel.

Figure 19-4. Center of gravity envelope chart.

Figure 19-2. A loading graph is used to determine the loadmoment for weights at various stations.

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reference line, which in this case is the dashedstandard temperature line. From this point,descend vertically to find the total takeoff distanceto clear a 50-foot obstacle. For the conditionsgiven, this particular gyroplane would require adistance of 940 feet for ground roll and the dis-tance needed to climb 50 feet above the surface.Notice that the data presented in this chart is pred-icated on certain conditions, such as a runningtakeoff to 30 m.p.h., a 50 m.p.h. climb speed, arotor prerotation speed of 370 r.p.m., and no wind.Variations from these conditions alter perform-ance, possibly to the point of jeopardizing the suc-cessful outcome of the maneuver.

HEIGHT/VELOCITY DIAGRAMLike helicopters, gyroplanes have a height/veloc-i t ydiagram that defines what speed and altitudecombinations allow for a safe landing in the eventof an engine failure. [Figure 19-6]

During an engine-out landing, the cyclic flare isused to arrest the vertical velocity of the aircraftand most of the forward velocity. On gyroplaneswith a manual collective control, increasing bladepitch just prior to touchdown can further reduceground roll. Typically, a gyroplane has a lower rotordisc loading than a helicopter, which provides a

slower rate of descent in autorotation. The powerrequired to turn the main transmission, tail rotortransmission, and tail rotor also add to the higher

Figure 19-5. Takeoff performance chart.

Figure 19-6. Operations within the shaded area of a height/veloc-ity diagram may not allow for a safe landing and are to be avoided.

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descent rate of a helicopter in autorotation as com-pared with that of a gyroplane.

EMERGENCY SECTIONBecause in-flight emergencies may not allowenough time to reference the flight manual, theemergency section should be reviewed periodi-cally to maintain familiarity with these procedures.

Many aircraft also use placards and instrumentmarkings in the cockpit, which provide importantinformation that may not be committed to mem-ory.

HANG TESTThe proper weight and balance of a gyroplanewithout a flight manual is normally determined byconducting a hang test of the aircraft. This isachieved by removing the rotor blades and sus-pending the aircraft by its teeter bolt, free fromcontact with the ground. A measurement is thentaken, either at the keel or the rotor mast, todetermine how many degrees from level the gyro-plane hangs. This number must be within therange specified by the manufacturer. For the testto reflect the true balance of the aircraft, it isimportant that it be conducted using the actualweight of the pilot and all gear normally carried inflight. Additionally, the measurement should betaken both with the fuel tank full and with it emptyto ensure that fuel burn does not affect the load-ing.

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The diversity of gyroplane designs available todayyields a wide variety of capability and perform-ance. For safe operation, you must be thoroughlyfamiliar with the procedures and limitations foryour particular aircraft along with other factors thatmay affect the safety of your flight.

PREFLIGHTAs pilot in command, you are the final authority indetermining the airworthiness of your aircraft.Adherence to a preflight checklist greatlyenhances your ability to evaluate the fitness ofyour gyroplane by ensuring that a complete andmethodical inspection of all components is per-formed. [Figure 20-1] For aircraft without a formalchecklist, it is prudent to create one that is specificto the aircraft to be sure that important items arenot overlooked. To determine the status of

required inspections, a preflight review of the air-craft records is also necessary.

COCKPIT MANAGEMENTAs in larger aircraft, cockpit management is animportant skill necessary for the safe operation of

a gyroplane. Intrinsic to these typically small aircraftis a limited amount of space that must be utilizedto its potential. The placement and accessibility ofcharts, writing materials, and other necessaryitems must be carefully considered. Gyroplaneswith open cockpits add the challenge of copingwith wind, which further increases the need forcreative and resourceful cockpit management foroptimum efficiency.

ENGINE STARTINGThe dissimilarity between the various types ofengines used for gyroplane propulsion necessi-tates the use of an engine start checklist. Again,when a checklist is not provided, it is advisable tocreate one for the safety of yourself and others,and to prevent inadvertent damage to the engineor propeller. Being inherently dangerous, the pro-peller demands special attention during enginestarting procedures. Always ensure that the pro-peller area is clear prior to starting. In addition toproviding an added degree of safety, being thor-oughly familiar with engine starting proceduresand characteristics can also be very helpful instarting an engine under various weather condi-tions.

TAXIINGThe ability of the gyroplane to be taxied greatlyenhances its utility. However, a gyroplane shouldnot be taxied in close proximity to people orobstructions while the rotor is turning. In addition,taxi speed should be limited to no faster than abrisk walk in ideal conditions, and adjusted appro-priately according to the circumstances.

BLADE FLAPOn a gyroplane with a semi-rigid, teeter-headrotor system, blade flap may develop if too muchairflow passes through the rotor system while it isoperating at low r.p.m. This is most often the resultof taxiing too fast for a given rotor speed. Unequallift acting on the advancing and retreating blades

Figure 20-1. A checklist is extremely useful in conducting a thor-ough preflight inspection.

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can cause the blades to teeter to the maximumallowed by the rotor head design. The blades thenhit the teeter stops, creating a vibration that maybe felt in the cyclic control. The frequency of thevibration corresponds to the speed of the rotor,with the blades hitting the stops twice during eachrevolution. If the flapping is not controlled, the sit-uation can grow worse as the blades begin to flex

and bend. Because the system is operating at lowr.p.m., there is not enough centrifugal force actingon the blades to keep them rigid. The shock of hit-ting the teeter stops combined with uneven liftalong the length of the blade causes an undula-tion to begin, which can increase in severity ifallowed to progress. In extreme cases, a rotorblade may strike the ground or propeller. [Figure20-2]

To avoid the onset of blade flap, always taxi thegyroplane at slow speeds when the rotor systemis at low r.p.m. Consideration must also be given

to wind speed and direction. If taxiing into a 10-knot headwind, for example, the airflow throughthe rotor will be 10 knots faster than the forwardspeed of the gyroplane, so the taxi speed shouldbe adjusted accordingly. When prerotating therotor by taxiing with the rotor disc tilted aft, allowthe rotor to accelerate slowly and smoothly. In theevent blade flap is encountered, apply forwardcyclic to reduce the rotor disc angle and slow thegyroplane by reducing throttle and applying thebrakes, if needed. [Figure 20-3]

BEFORE TAKEOFFFor the amateur-built gyroplane using single igni-tion and a fixed trim system, the before takeoffcheck is quite simple. The engine should be atnormal operating temperature, and the area mustbe clear for prerotation. Certificated gyroplanesusing conventional aircraft engines have a check-list that includes items specific to the powerplant.These normally include, but are not limited to,checks for magneto drop, carburetor heat, and, ifa constant speed propeller is installed, that it becycled for proper operation.

Following the engine run-up is the procedure foraccomplishing prerotation. This should bereviewed and committed to memory, as it typicallyrequires both hands to perform.

PREROTATIONPrerotation of the rotor can take many forms in a gyroplane. The most basic method is to turn therotor blades by hand. On a typical gyroplane witha counterclockwise rotating rotor, prerotation byhand is done on the right side of the rotor disk.This allows body movement to be directed away from the propellerto minimize the risk of injury. Other methods ofprerotation include using mechanical, electrical,or hydraulic means for the initial blade spin-up.

Figure 20-2. Taxiing too fast or gusting winds can cause bladeflap in a slow turning rotor. If not controlled, a rotor blade maystrike the ground.

Figure 20-3. Decreasing the rotor disc angle of attack with forward cyclic can reduce the excessive amount of airflow causing the bladeflap. This also allows greater clearance between the rotor blades and the surface behind the gyroplane, minimizing the chances of a bladestriking the ground.

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Many of these systems can achieve only a portion of the rotorspeed that is necessary for takeoff. After the pre-rotator is disengaged, taxi the gyroplane with the rotor disktilted aft to allow airflow through the rotor. Thisincreases rotor speed to flight r.p.m. In windy con-ditions, facing the gyroplane into the wind duringprerotation assists in achieving the highest possi-ble rotor speed from the prerotator. A factor oftenoverlooked that can negatively affect the prerota-tion speed is the cleanliness of the rotor blades.For maximum efficiency, it is recommended thatthe rotor blades be cleaned periodically. Byobtaining the maximum possible rotor speedthrough the use of proper prerotation techniques,you minimize the length of the ground roll that isrequired to get the gyroplane airborne.

The prerotators on certificated gyroplanes removethe possibility of blade flap during prerotation.Before the clutch can be engaged, the pitch mustbe removed from the blades. The rotor is then pre-rotated with a 0° angle of attack on the blades,which prevents lift from being produced and pre-cludes the possibility of flapping. When thedesired rotor speed is achieved, blade pitch isincreased for takeoff.

TAKEOFFTakeoffs are classified according to the takeoffsurface, obstructions, and atmospheric condi-tions. Each type of takeoff assumes that certainconditions exist. When conditions dictate, a com-bination of takeoff techniques can be used. Twoimportant speeds used for takeoff and initialclimbout are VX and V Y. VX is defined as the speedthat provides the best angle of climb, and will yieldthe maximum altitude gain over a given distance.This speed is normally used when obstacles onthe ground are a factor. Maintaining VY speedensures the aircraft will climb at its maximum rate,providing the most altitude gain for a given periodof time. [Figure 20-4] Prior to any takeoff or maneuver, youshould ensure that the area is clear of other traffic.

NORMAL TAKEOFFThe normal takeoff assumes that a prepared sur-face of adequate length is available and that thereare no high obstructions to be cleared within thetakeoff path. The normal takeoff for most amateur-built gyroplanes is accomplished by prerotating tosufficient rotor r.p.m. to prevent blade flapping andtilting the rotor back with cyclic control. Using aspeed of 20 to 30 m.p.h., allow the rotor to accel-

Figure 20-4. Best angle-of-climb (VX) speed is used when obstacles are a factor. VY provides the most altitude gain for a given amount oftime.

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COMMON ERRORS FOR NORMAL ANDCROSSWIND TAKEOFFS1. Failure to check rotor for proper operation,

track, and r.p.m. prior to takeoff.

2. Improper initial positioning of flight controls.

3. Improper application of power.

4. Poor directional control.

5. Failure to lift off at proper airspeed.

6. Failure to establish and maintain properclimb attitude and airspeed.

7. Drifting from the desired ground track duringthe climb.

SHORT-FIELD TAKEOFFShort-field takeoff and climb procedures may berequired when the usable takeoff surface is short,or when it is restricted by obstructions, such ast r e e s ,powerlines, or buildings, at the departure end. Thetechnique is identical to the normal takeoff, with performance being optimized during each phase.Using the help from wind and propwash, the max-imum rotor r.p.m. should be attained from the pre-rotator and full power applied as soon asappreciable lift is felt. VX climb speed should bemaintained until the obstruction is cleared.Familiarity with the rotor acceleration characteristics and proper technique are essentialfor optimum short-field performance.

If the prerotator is capable of spinning the rotor inexcess of normal flight r.p.m., the stored energymay be used to enhance short-field performance.Once maximum rotor r.p.m. is attained, disengagethe rotor drive, release the brakes, and applypower. As airspeed and rotor r.p.m. increase,apply additional power until full power is achieved.While remaining on the ground, accelerate thegyroplane to a speed just prior to VX. At that point,tilt the disk aft and increase the blade pitch to thenormal in-flight setting. The climb should be at aspeed just under VX until rotor r.p.m. has droppedto normal flight r.p.m. or the obstruction has beencleared. When the obstruction is no longer a fac-tor, increase the airspeed to VY.

COMMON ERRORS

1. Failure to position gyroplane for maximum utilization of available takeoff area.

erate and begin producing lift. As lift increases,move the cyclic forward to decrease the pitchangle on the rotor disc. When appreciable lift isbeing produced, the nose of the aircraft rises, andyou can feel an increase in drag. Using coordi-nated throttle and flight control inputs, balance thegyroplane on the main gear without the nosewheel or tail wheel in contact with the surface. Atthis point, smoothly increase power to full thrustand hold the nose at takeoff attitude with cyclicpressure. The gyroplane will lift off at or near theminimum power required speed for the aircraft. VXshould be used for the initial climb, then VY for theremainder of the climb phase.

A normal takeoff for certificated gyroplanes isaccomplished by prerotating to a rotor r.p.m.slightly above that required for flight and disen-gaging the rotor drive. The brakes are thenreleased and full power is applied. Lift off will notoccur until the blade pitch is increased to the nor-mal in-flight setting and the rotor disk tilted aft.This is normally accomplished at approximately30 to 40 m.p.h. The gyroplane should then beallowed to accelerate to VX for the initial climb, fol-lowed by VY for the remainder of the climb. On anytakeoff in a gyroplane, engine torque causes theaircraft to roll opposite the direction of propellerrotation, and adequate compensation must be made.

CROSSWIND TAKEOFFA crosswind takeoff is much like a normal takeoff,except that you have to use the flight controls to compensate for the crosswind component. Theterm crosswind component refers to that part ofthe wind which acts at right angles to the takeoffpath. Before attempting any crosswind takeoff,refer to the flight manual, if available, or the man-ufacturer’s recommendations for any limitations.

Begin the maneuver by aligning the gyroplane intothe wind as much as possible. At airports with wide runways, you might be able to angle your takeoffroll down the runway to take advantage of as muchheadwind as you can. As airspeed increases,gradually tilt the rotor into the wind and use rudderpressure to maintain runway heading. In most cases, youshould accelerate to a speed slightly faster than nor-mal liftoff speed. As you reach takeoff speed, thedownwind wheel lifts off the ground first, followed bythe upwind wheel. Once airborne, remove thecross-control inputs and establish a crab, if runwayheading is to be maintained. Due to the maneuver-ability of the gyroplane, an immediate turn into thewind after lift off can be safely executed, if this doesnot cause a conflict with existing traffic.

Normally Aspirated—An engine that does not compensate fordecreases in atmospheric pressure through turbocharging or othermeans.

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2. Failure to check rotor for proper operation,track, and r.p.m. prior to takeoff.

3. Improper initial positioning of flight controls.

4. Improper application of power.

5. Improper use of brakes.

6. Poor directional control.

7. Failure to lift off at proper airspeed.

8. Failure to establish and maintain properclimb attitude and airspeed.

9. Drifting from the desired ground track duringthe climb.

HIGH-ALTITUDE TAKEOFFA high-altitude takeoff is conducted in a mannervery similar to that of the short-field takeoff, whichachieves maximum performance from the aircraftduring each phase of the maneuver. One impor-tant consideration is that at higher altitudes, rotorr.p.m. is higher for a given blade pitch angle. Thishigher speed is a result of thinner air, and is nec-essary to produce the same amount of lift. Theinertia of the excess rotor speed should not beused in an attempt to enhance climb performance.Another important consideration is the effect ofaltitude on engine performance. As altitudeincreases, the amount of oxygen available forcombustion decreases. In normally aspiratedengines, it may be necessary to adjust the fuel/airmixture to achieve the best possible power output.This process is referred to as “leaning the mix-ture.” If you are considering a high-altitude take-off, and it appears that the climb performance limitof the gyroplane is being approached, do notattempt a takeoff until more favorable conditionsexist.

SOFT-FIELD TAKEOFFA soft field may be defined as any takeoff surfacethat measurably retards acceleration during thetakeoff roll. The objective of the soft-field takeoff isto transfer the weight of the aircraft from the land-ing gear to the rotor as quickly and smoothly aspossible to eliminate the drag caused by surfaces,such as tall grass, soft dirt, or snow. This takeoffrequires liftoff at a speed just above the minimumlevel flight speed for the aircraft. Due to design,many of the smaller gyroplanes have a limitedpitch attitude available, as tail contact with theground prevents high pitch attitudes until in flight.At minimum level flight speed, the pitch attitude isoften such that the tail wheel is lower than themain wheels. When performing a soft-field takeoff,these aircraft require slightly higher liftoff air-speeds to allow for proper tail clearance.

COMMON ERRORS

1. Failure to check rotor for proper operation,track, and r.p.m. prior to takeoff.

2. Improper initial positioning of flight controls.

3. Improper application of power.

4. Allowing gyroplane to lose momentum by slowing or stopping on takeoff surface priorto initiating takeoff.

5. Poor directional control.

6. Improper pitch attitude during lift-off.

7. Settling back to takeoff surface after becom-ing airborne.

8. Failure to establish and maintain properclimb attitude and airspeed.

9. Drifting from the desired ground track duringthe climb.

JUMP TAKEOFFGyroplanes with collective pitch change, and the ability to prerotate the rotor system to speedsapproximately 50 percent higher than thoserequired for normal flight, are capable of achieving extremelyshort takeoff rolls. Actual jump takeoffs can be per-

Figure 20-5. During a jump takeoff, excess rotor inertia is used tolift the gyroplane nearly vertical, where it is then acceleratedthrough minimum level flight speed.

Density Altitude—Pressure altitude corrected for nonstandard tem-perature. This is a theoretical value that is used in determining air-craft performance.

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formed under the proper conditions. A jump take-off requires no ground roll, making it the mosteffective soft-field and crosswind takeoff proce-dure. [Figure 20-5] A jump takeoff is possiblebecause the energy stored in the blades, as aresult of the higher rotor r.p.m., is used to keep thegyroplane airborne as it accelerates through mini-mum level flight speed. Failure to have sufficientrotor r.p.m. for a jump takeoff results in the gyro-p l a n esettling back to the ground. Before attempting ajump takeoff, it is essential that you first determineif it is possible given the existing conditions byconsulting the relevant performance chart. Shouldconditions of weight, altitude, temperature, orwind leave the successful outcome of the maneu-ver in doubt, it should not be attempted.

The prudent pilot may also use a “rule of thumb”for predicting performance before attempting ajump takeoff. As an example, suppose that a par-ticular gyroplane is known to be able to make ajump takeoff and remain airborne to accelerate toVX at a weight of 1,800 pounds and a density alti-tude of 2,000 feet. Since few takeoffs are madeunder these exact conditions, compensation mustbe made for variations in weight, wind, and den-

sity altitude. The “rule of thumb” being used forthis particular aircraft stipulates that 1,000 feet ofdensity altitude equates with 10 m.p.h. wind or100 pounds of gross weight. To use this equation,

you must first determine the density altitude. Thisis accomplished by setting your altimeter to the standard sea levelpressure setting of 29.92 inches of mercury andreading the pressure altitude. Next, you must cor-rect for nonstandard temperature. Standard tem-perature at sea level is 59°F (15°C) anddecreases 3.5°F (2°C) for every additional onethousand feet of pressure altitude. [Figure 20-6]Once you have determined the standard tempera-ture for your pressure altitude, compare it with theactual existing conditions. For every 10°F (5.5°C)the actual temperature is above standard, add 750feet to the pressure altitude to estimate the density altitude.If the density altitude is above 2,000 feet, a jumptakeoff in this aircraft should not be attemptedunless wind and/or a weight reduction would com-pensate for the decrease in performance. Usingthe equation, if the density altitude is 3,000 feet(1,000 feet above a satisfactory jump density altitude), a reduction of 100 pounds ingross weight or a 10 m.p.h. of wind would stillallow a satisfactory jump takeoff. Additionally, areduction of 50 pounds in weight combined with a5 m.p.h. wind would also allow a satisfactoryjump. If it is determined that a jump takeoff shouldnot be conducted because the weight cannot bereduced or an appropriate wind is not blowing,then consideration should be given to a rollingtakeoff. A takeoff roll of 10 m.p.h. is equivalent to awind speed of 10 m.p.h. or a reduction of 100pounds in gross weight. It is important to note thata jump takeoff is predicated on having achieved aspecific rotor r.p.m. If this r.p.m. has not been

attained, performance is unpredictable, and themaneuver should not be attempted.

Figure 20-7. The angle of the rotor disc decreases at higher cruisespeeds, which increases pitch control sensitivity.

Figure 20-6. Standard temperature chart.

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BASIC FLIGHT MANEUVERSConducting flight maneuvers in a gyroplane is dif-ferent than in most other aircraft. Because of thewide variety in designs, many gyroplanes haveonly basic instruments available, and the pilot isoften exposed to the airflow. In addition, the visualclues found on other aircraft, such as cowlings,wings, and windshields might not be part of yourgyroplane’s design. Therefore, much morereliance is placed on pilot interpretation of flight attitude and the “feel” of thegyroplane than in other types of aircraft. Acquiringthe skills to precisely control a gyroplane can be a challenging and rewarding experience, butrequires dedication and the direction of a compe-tent instructor.

STRAIGHT-AND-LEVEL FLIGHTStraight-and-level flight is conducted by maintain-ing a constant altitude and a constant heading. Inflight, a gyroplane essentially acts as a plumb sus-pended from the rotor. As such, torque forces fromthe engine cause the airframe to be deflected afew degrees out of the vertical plane. This veryslight “out of vertical” condition should be ignored and the aircraft flownto maintain a constant heading.

The throttle is used to control airspeed. In levelflight, when the airspeed of a gyroplane increases,the rotor disc angle of attack must be decreased.This causes pitch control to become increasinglymore sensitive. [Figure 20-7] As this disc anglebecomes very small, it is possible to overcontrol agyroplane when encountering turbulence. For thisreason, when extreme turbulence is encountered or expected, airspeedshould be decreased. Even in normal conditions,a gyroplane requires constant attention to main-tain straight-and-level flight. Although more stablethan helicopters, gyroplanes are less stable thanairplanes. When cyclic trim is available, it shouldbe used to relieve any stick forces required duringstabilized flight.

CLIMBS A climb is achieved by adding power in excess ofwhat is required for straight-and-level flight at aparticular airspeed. The amount of excess powerused is directly proportional to the climb rate. Formaneuvers when maximum performance isdesired, two important climb speeds are bestangle-of-climb speed and best rate-of-climbspeed.

Because a gyroplane cannot be stalled, it may betempting to increase the climb rate by decreasingairspeed. This practice, however, is self-defeating.

causes a diminishing rate of climb. In fact, if agyroplane is slowed to the minimum level flightspeed, it requires full power just to maintain alti-tude. Operating in this performance realm, some-times referred to as the “backside of the powercurve,” is desirable in some maneuvers, but canbe hazardous when maximum climb performanceis required. For further explanation of a gyroplanepower curve, see Flight at Slow Airspeeds, whichis discussed later in this chapter.

DESCENTS A descent is the result of using less power than thatrequired for straight-and-level flight at a particular airspeed. Varying engine power during a descentallows you to choose a variety of descent profiles. Ina power-off descent, the minimum descent rate isachieved by using the airspeed that would normallybe used for level flight at minimum power, which isalso very close to the speed used for the best angle

of climb. When distance is a factor during a power-off descent, maximum gliding distance can beachieved by maintaining a speed very close to thebest rate-of-climb airspeed. Because a gyroplanecan be safely flown down to zero airspeed, a com-mon error in this type of descent is attempting toextend the glide by raising the pitch attitude. The

Figure 20-8. During a slip, the rate of turn is too slow for the angleof bank used, and the horizontal component of lift (HCL) exceedsinertia. You can reestablish equilibrium by decreasing the angle ofbank, increasing the rate of turn by applying rudder pedal, or acombination of the two.

Figure 20-9. During a skid, inertia exceeds the HCL. To reestab-lish equilibrium, increase the bank angle or reduce the rate of turnby applying rudder pedal. You may also use a combination ofthese two corrections.

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result is a higher rate of descent and less distancebeing covered. For this reason, proper glide speedshould be adhered to closely. Should a strong head-wind exist, while attempting to achieve the maxi-mum distance during a glide, a rule of thumb toachieve the greatest distance is to increase the glidespeed by approximately 25 percent of the head-wind. The attitude of the gyroplane for best glideperformance is learned with experience, and slightpitch adjustments are made for the proper airspeed.If a descent is needed to lose excess altitude, slow-ing the gyroplane to below the best glide speedincreases the rate of descent. Typically, slowing tozero airspeed results in a descent rate twice that ofmaintaining the best glide speed.

TURNSTurns are made in a gyroplane by banking the rotordisc with cyclic control. Once the area, in the direc-tion of the turn, has been cleared for traffic, applysideward pressure on the cyclic until the desiredbank angle is achieved. The speed at which thegyroplane enters the bank is dependent on how farthe cyclic is displaced. When the desired bankangle is reached, return the cyclic to the neutralposition. The rudder pedals are used to keep thegyroplane in longitudinal trim throughout the turn,but not to assist in establishing the turn.

The bank angle used for a turn directly affects therate of turn. As the bank is steepened, the turnrate increases, but more power is required tomaintain altitude. A bank angle can be reachedwhere all available power is required, with any fur-ther increase in bank resulting in a loss of airspeedor altitude. Turns during a climb should be made atthe minimum angle of bank necessary, as higherbank angles would require more power that wouldotherwise be available for the climb. Turns whilegliding increase the rate of descent and may beused as an effective way of losing excess altitude.

SLIPSA slip occurs when the gyroplane slides sidewaystoward the center of the turn. [Figure 20-8] It iscaused by an insufficient amount of rudder pedalin the direction of the turn, or too much in thedirection opposite the turn. In other words, holdingimproper rudder pedal pressure keeps the nosefrom following the turn, the gyroplane slips side-ways toward the center of the turn.

SKIDSA skid occurs when the gyroplane slides sidewaysaway from the center of the turn. [Figure 20-9] It iscaused by too much rudder pedal pressure in thedirection of the turn, or by too little in the directionopposite the turn. If the gyroplane is forced to turn

faster with increased pedal pressure instead of byincreasing the degree of bank, it skids sidewaysaway from the center of the turn instead of flying inits normal curved pattern.

COMMON ERRORS DURING BASIC FLIGHTMANEUVERS

1. Improper coordination of flight controls.

2. Failure to cross-check and correctly interpret outside and instrument references.

3. Using faulty trim technique.

STEEP TURNSA steep turn is a performance maneuver used in training that consists of a turn in either direction ata bank angle of approximately 40°. The objectiveo fperforming steep turns is to develop smoothness,coordination, orientation, division of attention, andcontrol techniques.

Prior to initiating a steep turn, or any other flightmaneuver, first complete a clearing turn to checkthe area for traffic. To accomplish this, you mayexecute either one 180° turn or two 90° turns ino p p o s i t edirections. Once the area has been cleared, rollthe gyroplane into a 40° angle-of-bank turn whilesmoothly adding power and slowly moving thecyclic aft to maintain altitude. Maintain coordi-nated flight with proper rudder pedal pressure.Throughout the turn, cross-reference visual cuesoutside the gyroplane with the flight instruments, ifavailable, to maintain a constant altitude andangle of bank. Anticipate the roll-out by leadingthe roll-out heading by approximately 20°. Usingsection lines or prominent landmarks to aid in ori-entation can be helpful in rolling out on the properheading. During roll-out, gradually return thecyclic to the original position and reduce power tom a i n t a i naltitude and airspeed.

COMMON ERRORS

1. Improper bank and power coordination dur-ing entry and rollout.

2. Uncoordinated use of flight controls.

3. Exceeding manufacturer’s recommendedmaximum bank angle.

4. Improper technique in correcting altitude deviations.

5. Loss of orientation.

6. Excessive deviation from desired headingduring rollout.

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GROUND REFERENCE MANEUVERSGround reference maneuvers are training exer-cises flown to help you develop a division of atten-tion between the flight path and groundreferences, while controlling the gyroplane andwatching for other aircraft in the vicinity. Prior to each maneuver, aclearing turn should be accomplished to ensurethe practice area is free of conflicting traffic.

RECTANGULAR COURSEThe rectangular course is a training maneuver inwhich the ground track of the gyroplane is equi-distant from all sides of a selected rectangulararea on the ground. [Figure 20-10] While perform-ing the maneuver, the altitude and airspeedshould be held constant. The rectangular coursehelps you to develop a recognition of a drift towardor away from a line parallel to the intended groundtrack. This is helpful in recognizing drift toward orfrom an airport runway during the various legs ofthe airport traffic pattern.

For this maneuver, pick a square or rectangularfield, or an area bounded on four sides by sectionlines or roads, where the sides are approximatelya mile in length. The area selected should be well

away from other air traffic. Fly the maneuverapproximately 600 to 1,000 feet above theground, which is the altitude usually required foran airport traffic pattern. You should fly the gyroplane parallel to and at a uniform distance,about one-fourth to one-half mile, from the fieldboundaries, not above the boundaries. For bestresults, position your flight path outside the fieldboundaries just far enough away that they may beeasily observed. You should be able to see theedges of the selected field while seated in a nor-mal position and looking out the side of the gyro-plane during either a left-hand or right-handcourse. The distance of the ground track from theedges of the field should be the same regardlessof whether the course is flown to the left or right.All turns should be started when your gyroplane isabeam the corners of the field boundaries. Thebank normally should not exceed 30°.

Although the rectangular course may be enteredfrom any direction, this discussion assumes entryon a downwind heading. As you approach the fieldboundary on the downwind leg, you should beginplanning for your turn to the crosswind leg. Sinceyou have a tailwind on the downwind leg, thegyroplane’s groundspeed is increased (position

Figure 20-10. Rectangular course. The numbered positions in the text refer to the numbers in this illustration.

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1). During the turn onto the crosswind leg, whichis the equivalent of the base leg in a traffic pattern,the wind causes the gyroplane to drift away fromthe field. To counteract this effect, the roll-inshould be made at a fairly fast rate with a relativelysteep bank (position 2).

As the turn progresses, the tailwind componentdecreases, which decreases the groundspeed.Consequently, the bank angle and rate of turnmust be reduced gradually to ensure that uponcompletion of the turn, the crosswind ground trackcontinues to be the same distance from the edgeof the field. Upon completion of the turn, the gyro-plane should be level and aligned with the down-wind corner of the field. However, since thecrosswind is now pushing you away from the field,you must establish the proper drift correction byflying slightly into the wind. Therefore, the turn tocrosswind should be greater than a 90° change inheading (position 3). If the turn has been madeproperly, the field boundary again appears to beone-fourth to one-half mile away. While on thecrosswind leg, the wind correction should beadjusted, as necessary, to maintain a uniform dis-tance from the field boundary (position 4).

As the next field boundary is being approached(position 5), plan the turn onto the upwind leg.Since a wind correction angle is being held intothe wind and toward the field while on the cross-wind leg, this next turn requires a turn of less than90°. Since the crosswind becomes a headwind,

causing the groundspeed to decrease during thisturn, the bank initially must be medium and pro-gressively decreased as the turn proceeds. Tocomplete the turn, time the rollout so that the gyro-plane becomes level at a point aligned with thecorner of the field just as the longitudinal axis ofthe gyroplane again becomes parallel to the field

boundary (position 6). The distance from the fieldboundary should be the same as on the othersides of the field.

On the upwind leg, the wind is a headwind, whichresults in an decreased groundspeed (position 7).Consequently, enter the turn onto the next leg witha fairly slow rate of roll-in, and a relatively shallowbank (position 8). As the turn progresses, gradu-ally increase the bank angle because the head-wind component is diminishing, resulting in anincreasing groundspeed. During and after the turnonto this leg, the wind tends to drift the gyroplanetoward the field boundary. To compensate for thedrift, the amount of turn must be less than 90°(position 9).

Again, the rollout from this turn must be such thatas the gyroplane becomes level, the nose of thegyroplane is turned slightly away the field and intothe wind to correct for drift. The gyroplane shouldagain be the same distance from the field bound-ary and at the same altitude, as on other legs.Continue the crosswind leg until the downwind legboundary is approached (position 10). Once moreyou should anticipate drift and turning radius.Since drift correction was held on the crosswindleg, it is necessary to turn greater than 90° to alignthe gyroplane parallel to the downwind leg bound-ary. Start this turn with a medium bank angle,gradually increasing it to a steeper bank as theturn progresses. Time the rollout to assure paral-leling the boundary of the field as the gyroplanebecomes level (position 11).

If you have a direct headwind or tailwind on theupwind and downwind leg, drift should not beencountered. However, it may be difficult to find asituation where the wind is blowing exactly parallelto the field boundaries. This makes it necessary touse a slight wind correction angle on all the legs. It is important toanticipate the turns to compensate for ground-speed, drift, and turning radius. When the wind isbehind the gyroplane, the turn must be faster andsteeper; when it is ahead of the gyroplane, the turnmust be slower and shallower. These same tech-niques apply while flying in an airport traffic pat-tern.

S-TURNSAnother training maneuver you might use is the S-turn, which helps you correct for wind drift in turns.This maneuver requires turns to the left and right.The reference line used, whether a road, railroad,or fence, should be straight for a considerable dis-tance and should extend as nearly perpendicularto the wind as possible.

Figure 20-11. S-turns across a road.

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The object of S-turns is to fly a pattern of two half circles of equal size on opposite sides of the refer-ence line. [Figure 20-11] The maneuver should be performed at a constant altitude of 600 to 1,000feet above the terrain. S-turns may be started atany point; however, during early training it may bebeneficial to start on a downwind heading.Entering downwind permits the immediate selection of the steepestbank that is desired throughout the maneuver. Thediscussion that follows is based on choosing a ref-erence line that is perpendicular to the wind andstarting the maneuver on a downwind heading.

As the gyroplane crosses the reference line,immediately establish a bank. This initial bank isthe steepest used throughout the maneuver sincethe gyroplane is headed directly downwind andthe groundspeed is at its highest. Graduallyreduce the bank, as necessary, to describe aground track of a half circle. Time the turn so thatas the rollout is completed, the gyroplane is cross-ing the reference line perpendicular to it and head-ing directly upwind. Immediately enter a bank inthe opposite direction to begin the second half ofthe “S.” Since the gyroplane is now on an upwindheading, this bank (and the one just completedbefore crossing the reference line) is the shallow-est in the maneuver. Gradually increase the bank,as necessary, to describe a ground track that is ahalf circle identical in size to the one previouslycompleted on the other side of the reference line.The steepest bank in this turn should be attainedjust prior to rollout when the gyroplane is

approaching the reference line nearest the down-wind heading. Time the turn so that as the rolloutis complete, the gyroplane is perpendicular to thereference line and is again heading directly down-wind.

In summary, the angle of bank required at anygiven point in the maneuver is dependent on thegroundspeed. The faster the groundspeed, thesteeper the bank; the slower the groundspeed, thes h a l l o w e rthe bank. To express it another way, the morenearly the gyroplane is to a downwind heading,the steeper the bank; the more nearly it is to anupwind heading, the shallower the bank. In addi-tion to varying the angle of bank to correct for driftin order to maintain the proper radius of turn, thegyroplane must also be flown with a drift correc-tion angle (crab) in relation to its ground track;except of course, when it is on direct upwind ordownwind headings or there is no wind. Onewould normally think of the fore and aft axis of thegyroplane as being tangent to the ground trackpattern at each point. However, this is not thecase. During the turn on the upwind side of thereference line (side from which the wind is blow-ing), crab the nose of the gyroplane toward theoutside of the circle. During the turn on the down-wind side of the reference line (side of the refer-ence line opposite to the direction from which thewind is blowing), crab the nose of the gyroplanetoward the inside of the circle. In either case, it isobvious that the gyroplane is being crabbed intothe wind just as it is when trying to maintain astraight ground track. The amount of crabdepends upon the wind velocity and how nearlythe gyroplane is to a crosswind position. Thestronger the wind, the greater the crab angle atany given position for a turn of a given radius. Themore nearly the gyroplane is to a crosswind posi-tion, the greater the crab angle. The maximumcrab angle should be at the point of each half cir-cle farthest from the reference line.

A standard radius for S-turns cannot be specified,since the radius depends on the airspeed of thegyroplane, the velocity of the wind, and the initialbank chosen for entry.

TURNS AROUND A POINTThis training maneuver requires you to fly con-stant radius turns around a preselected point onthe ground using a maximum bank of approxi-mately 40°, while maintaining a constant altitude.[Figure 20-12] Your objective, as in other groundreference maneuvers, is to develop the ability tosubconsciously control the gyroplane while divid-

Figure 20-12. Turns around a point.

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ing attention between the flight path and groundreferences, while still watching for other air trafficin the vicinity.

The factors and principles of drift correction thatare involved in S-turns are also applicable in thismaneuver. As in other ground track maneuvers, aconstant radius around a point will, if any windexists, require a constantly changing angle ofbank and angles of wind correction. The closer thegyroplane is to a direct downwind heading wherethe groundspeed is greatest, the steeper thebank, and the faster the rate of turn required toestablish the proper wind correction angle. Themore nearly it is to a direct upwind heading wherethe groundspeed is least, the shallower the bank,and the slower the rate of turn required to estab-l i s hthe proper wind correction angle. It follows then, that throughout the maneuver, the bank and rateo fturn must be gradually varied in proportion to the groundspeed.

The point selected for turns around a point shouldbe prominent and easily distinguishable, yet smallenough to present a precise reference. Isolatedt r e e s ,crossroads, or other similar small landmarks areusually suitable. The point should be in an areaaway from communities, livestock, or groups ofpeople on the ground to prevent possible annoy-ance or hazard to others. Since the maneuver is performed between600 and 1,000 feet AGL, the area selected shouldalso afford an opportunity for a safe emergencylanding in the event it becomes necessary.

To enter turns around a point, fly the gyroplane ona downwind heading to one side of the selected

point at a distance equal to the desired radius ofturn. When any significant wind exists, it is neces-sary to roll into the initial bank at a rapid rate sothat the steepest bank is attained abeam the pointwhen the gyroplane is headed directly downwind.By entering the maneuver while heading directlydownwind, the steepest bank can be attainedimmediately. Thus, if a bank of 40° is desired, theinitial bank is 40° if the gyroplane is at the correctdistance from the point. Thereafter, the bank isgradually shallowed until the point is reachedwhere the gyroplane is headed directly upwind. Atthis point, the bank is gradually steepened untilthe steepest bank is again attained when headingdownwind at the initial point of entry.

Just as S-turns require that the gyroplane beturned into the wind, in addition to varying thebank, so do turns around a point. During thedownwind half of the circle, the gyroplane’s nosemust be progressively turned toward the inside ofthe circle; during the upwind half, the nose mustbe progressively turned toward the outside. Thedownwind half of the turn around the point may becompared to the downwind side of the S-turn,while the upwind half of the turn around a pointmay be compared to the upwind side of the S-turn.

As you become experienced in performing turnsaround a point and have a good understanding ofthe effects of wind drift and varying of the bankangle and wind correction angle, as required,entry into the maneuver may be from any point.When entering this maneuver at any point, theradius of the turn must be carefully selected, tak-ing into account the wind velocity and ground-speed, so that an excessive bank is not requiredlater on to maintain the proper ground track.

Figure 20-13. The low point on the power required curve is the speed that the gyroplane can fly while using the least amount of power,and is also the speed that will result in a minimum sink rate in a power-off glide.

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COMMON ERRORS DURING GROUNDREFERENCE MANEUVERS

1. Faulty entry technique.

2. Poor planning, orientation, or division of attention.

3. Uncoordinated flight control application.

4. Improper correction for wind drift.

5. An unsymmetrical ground track during S-turns across a road.

6. Failure to maintain selected altitude or air-speed.

7. Selection of a ground reference where thereis no suitable emergency landing site.

FLIGHT AT SLOW AIRSPEEDSThe purpose of maneuvering during slow flight isto help you develop a feel for controlling the gyro-plane at slow airspeeds, as well as gain an under-standing of how load factor, pitch attitude,airspeed, and altitude control relate to each other.

Like airplanes, gyroplanes have a specific amountof power that is required for flight at various air-speeds, and a fixed amount of power available fromthe engine. This data can be charted in a graph for-mat. [Figure 20-13] The lowest point of the powerrequired curve represents the speed at which thegyroplane will fly in level flight while using the leastamount of power. To fly faster than this speed, orslower, requires more power. While practicing slow flight in a gyroplane, you will likelybe operating in the performance realm on the chartthat is left of the minimum power required speed.This is often referred to as the “backside of thepower curve,” or flying “behind the power curve.” At these speeds,as pitch is increased to slow the gyroplane, moreand more power is required to maintain level flight.At the point where maximum power available isbeing used, no further reduction in airspeed is possible without ini-tiating a descent. This speed is referred to as theminimum level flight speed. Because there is noexcess power available for acceleration, recoveryfrom minimum level flight speed requires loweringthe nose of the gyroplane and using altitude toregain airspeed. For this reason, it is essential topractice slow flight at altitudes that allow sufficientheight for a safe recovery. Unintentionally flying a gyroplane on the backside of the powercurve during approach and landing can bee x t r e m e l yhazardous. Should a go-around become neces-s a r y ,

sufficient altitude to regain airspeed and initiate aclimb may not be available, and ground contactmay be unavoidable.

Flight at slow airspeeds is usually conducted atairspeeds 5 to 10 m.p.h. above the minimum levelflight airspeed. When flying at slow airspeeds, it isimportant that your control inputs be smooth andslow to prevent a rapid loss of airspeed due to thehigh drag increases with small changes in pitchattitude. In addition, turns should be limited toshallow bank angles. In order to prevent losingaltitude during turns, power must be added.Directional control remains very good while flyingat slow airspeeds, because of the high velocityslipstream produced by the increased enginepower.

Recovery to cruise flight speed is made by lower-ing the nose and increasing power. When thedesired speed is reached, reduce power to thenormal cruise power setting.

COMMON ERRORS

1. Improper entry technique.

2. Failure to establish and maintain an appro-priate airspeed.

3. Excessive variations of altitude and headingwhen a constant altitude and heading are specified.

4. Use of too steep a bank angle.

5. Rough or uncoordinated control technique.

HIGH RATE OF DESCENTA gyroplane will descend at a high rate when flownat very low forward airspeeds. This maneuver maybe entered intentionally when a steep descent isdesired, and can be performed with or withoutpower. An unintentional high rate of descent canalso occur as a result of failing to monitor andmaintain proper airspeed. In powered flight, if thegyroplane is flown below minimum level flightspeed, a descent results even though full enginepower is applied. Further reducing the airspeedwith aft cyclic increases the rate of descent. Forgyroplanes with a high thrust-to-weight ratio, thismaneuver creates a very high pitch attitude. Torecover, the nose of the gyroplane must loweredslightly to exchange altitude for an increase in air-speed.

When operating a gyroplane in an unpoweredglide, slowing to below the best glide speed canalso result in a high rate of descent. As airspeeddecreases, the rate of descent increases, reach-

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ing the highest rate as forward speed approacheszero. At slow airspeeds without the engine run-ning, there is very little airflow over the tail sur-faces and rudder effectiveness is greatly reduced.Rudder pedal inputs must be exaggerated tomaintain effective yaw control. To recover, addpower, if available, or lower the nose and allow thegyroplane to accelerate to the proper airspeed.This maneuver demonstrates the importance ofmaintaining the proper glide speed during anengine-out emergency landing. Attempting tostretch the glide by raising the nose results in ahigher rate of descent at a lower forward speed,leaving less distance available for the selection ofa landing site.

COMMON ERRORS

1. Improper entry technique.

2. Failure to recognize a high rate of descent.

3. Improper use of controls during recovery.

4. Initiation of recovery below minimum recov-ery altitude.

LANDINGSLandings may be classified according to the land-ing surface, obstructions, and atmospheric condi-tions. Each type of landing assumes that certainconditions exist. To meet the actual conditions, acombination of techniques may be necessary.

NORMAL LANDINGThe procedure for a normal landing in a gyroplaneis predicated on having a prepared landing sur-face and no significant obstructions in the immedi-ate area. After entering a traffic pattern thatconforms to established standards for the airportand avoids the flow of fixed wing traffic, a beforelanding checklist should be reviewed. The extentof the items on the checklist is dependent on thecomplexity of the gyroplane, and can include fuel,mixture, carburetor heat, propeller, engine instru-ments, and a check for traffic.

Gyroplanes experience a slight lag between con-trol input and aircraft response. This lag becomesmore apparent during the sensitive maneuveringrequired for landing, and care must be taken toavoid overcorrecting for deviations from thedesired approach path. After the turn to final, theapproach airspeed appropriate for the gyroplaneshould be established. This speed is normally justbelow the minimum power required speed for thegyroplane in level flight. During the approach,maintain this airspeed by making adjustments tothe gyroplane’s pitch attitude, as necessary.Power is used to control the descent rate.

Approximately 10 to 20 feet above the runway,begin the flare by gradually increasing back pres-sure on the cyclic to reduce speed and decreasethe rate of descent. The gyroplane should reacha near-zero rate of descent approximately 1 footabove the runway with the power at idle. Low air-

Figure 20-14. The airspeed used on a short-field approach is slower than that for a normal approach, allowing a steeper approach pathand requiring less runway.

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speed combined with a minimum of propwashover the tail surfaces reduces rudder effectiveness during the flare. If a yaw moment isencountered, use whatever rudder control isrequired to maintain the desired heading. Thegyroplane should be kept laterally level and withthe longitudinal axis in the direction of groundtrack. Landing with sideward motion can damagethe landing gear and must be avoided. In a full-flare landing, attempt to hold the gyroplane justoff the runway by steadily increasing back pres-sure on the cyclic. This causes the gyroplane tosettle slowly to the runway in a slightly nose-highattitude as forward momentum dissipates.

Ground roll for a full-flare landing is typicallyunder 50 feet, and touchdown speed under 20m.p.h. If a 20 m.p.h. or greater headwind exists, itmay be necessary to decrease the length of theflare and allow the gyroplane to touch down at aslightly higher airspeed to prevent it from rollingbackward on landing. After touchdown, rotorr.p.m. decays rather rapidly. On landings wherebrakes are required immediately after touchdown,apply them lightly, as the rotor is still carryingmuch of the weight of the aircraft and too muchbraking causes the tires to skid.

SHORT-FIELD LANDING A short-field landing is necessary when you havea relatively short landing area or when anapproach must be made over obstacles that limitthe available landing area. When practicing short-field landings, assume you are making theapproach and landing over a 50-foot obstructionin the approach area.

To conduct a short-field approach and landing,follow normal procedures until you are estab-lished on the final approach segment. At thispoint, use aft cyclic to reduce airspeed below thespeed for minimum sink. By decreasing speed,sink rate increases and a steeper approach pathis achieved, minimizing the distance betweenclearing the obstacle and making contact with the surface. [Figure 20-14]The approach speed must remain fast enough,however, to allow the flare to arrest the forwardand vertical speed of the gyroplane. If theapproach speed is too low, the remaining verti-cal momentum will result in a hard landing. On ashort-field landing with a slight headwind, atouchdown with no ground roll is possible.Without wind, the ground roll is normally lessthan 50 feet.

SOFT-FIELD LANDINGUse the soft-field landing technique when thelanding surface presents high wheel drag, such asmud, snow, sand, tall grass or standing water. Theobjective is to transfer the weight of the gyroplanefrom the rotor to the landing gear as gently andslowly as possible. With a headwind close to thetouchdown speed of the gyroplane, a power approach can be made closeto the minimum level flight speed. As you increasethe nose pitch attitude just prior to touchdown, addadditional power to cushion the landing. However,power should be removed, just as the wheels areready to touch. This results is a very slow, gentletouchdown. In a strong headwind, avoid allowingthe gyroplane to roll rearward at touchdown. Aftertouchdown, smoothly and gently lower the nose-wheel to the ground. Minimize the use of brakes,and remain aware that the nosewheel could dig inthe soft surface.

When no wind exists, use a steep approach simi-lar to a short-field landing so that the forwardspeed can be dissipated during the flare. Use thethrottle to cushion the touchdown.

CROSSWIND LANDING Crosswind landing technique is normally used ingyroplanes when a crosswind of approximately 15m.p.h. or less exists. In conditions with highercrosswinds, it becomes very difficult, if not impos-sible, to maintain adequate compensation for thecrosswind. In these conditions, the slow touch-down speed of a gyroplane allows a much saferoption of turning directly into the wind and landingwith little or no ground roll. Deciding when to usethis technique, however, may be complicated by gusting winds or the characteris-tics of the particular landing area.

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On final approach, establish a crab angle into thewind to maintain a ground track that is aligned withthe extended centerline of the runway. Just before touchdown, remove the crab angle and bank the gyroplane slightly into the wind to prevent drift.Maintain longitudinal alignment with the runwayusing the rudder. In higher crosswinds, if full rud-der deflection is not sufficient to maintain align-ment with the runway, applying a slight amount ofpower can increase rudder effectiveness. Thelength of the flare should be reduced to allow aslightly higher touchdown speed than that used ina no-wind landing. Touchdown is made on theupwind main wheel first, with the other main wheelsettling to the runway as forward momentum islost. After landing, continue to keep the rotor tiltedinto the wind to maintain positive control during therollout.

HIGH-ALTITUDE LANDING A high-altitude landing assumes a density altitudenear the limit of what is considered good climbperformance for the gyroplane. When using thesame indicated airspeed as that used for a normal approach atlower altitude, a high density altitude results inhigher rotor r.p.m. and a slightly higher rate ofdescent. The greater vertical velocity is a result ofhigher true airspeed as compared with that at lowaltitudes. When practicing high-altitude landings,it is prudent to first learn normal landings with aflare and roll out. Full flare, no roll landings shouldnot be attempted until a good feel for aircraftresponse at higher altitudes has been acquired.As with high-altitude takeoffs, it is also importantto consider the effects of higher altitude on engine performance.

COMMON ERRORS DURING LANDING

1. Failure to establish and maintain a stabilizedapproach.

2. Improper technique in the use of power.

3. Improper technique during flare or touch-down.

4. Touchdown at too low an airspeed withstrong headwinds, causing a rearward roll.

5. Poor directional control after touchdown.

6. Improper use of brakes.

GO-AROUNDThe go-around is used to abort a landingapproach when unsafe factors for landing are rec-ognized. If the decision is made early in theapproach to go around, normal climb proceduresutilizing VX and VY should be used. A late decision

to go around, such as after the full flare has beeninitiated, may result in an airspeed where powerrequired is greater than power available. Whenthis occurs, a touchdown becomes unavoidableand it may be safer to proceed with the landingthan to sustain an extended ground roll that wouldbe required to go around. Also, the pitch attitudeof the gyroplane in the flare is high enough thatthe tail would be considerably lower than the maingear, and a touch down with power on wouldresult in a sudden pitch down and acceleration ofthe aircraft. Control of the gyroplane under thesecircumstances may be difficult. Consequently, thedecision to go around should be made as early aspossible, before the speed is reduced below thepoint that power required exceeds power avail -able.

COMMON ERRORS

1. Failure to recognize a situation where a go-around is necessary.

2. Improper application of power.

3. Failure to control pitch attitude.

4. Failure to maintain recommended airspeeds.

5. Failure to maintain proper track during climbout.

AFTER LANDING AND SECURING The after-landing checklist should include suchitems as the transponder, cowl flaps, fuel pumps,lights, and magneto checks, when so equipped.The rotor blades demand special considerationafter landing, as turning rotor blades can be haz-ardous to others. Never enter an area where peo-ple or obstructions are present with the rotorturning. To assist the rotor in slowing, tilt the cycliccontrol into the prevailing wind or face the gyro-plane downwind. When slowed to under approxi-mately 75 r.p.m., the rotor brake may be applied, ifavailable. Use caution as the rotor slows, asexcess taxi speed or high winds could causeblade flap to occur. The blades should bedepitched when taxiing if a collective control isavailable. When leaving the gyroplane, alwayssecure the blades with a tiedown or rotor brake.

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Gyroplanes are quite reliable, however emergen-cies do occur, whether a result of mechanical fail-ure or pilot error. By having a thorough knowledgeof the gyroplane and its systems, you will be able tomore readily handle the situation. In addition, byknowing the conditions which can lead to anemergency, many potential accidents can beavoided.

ABORTED TAKEOFFPrior to every takeoff, consideration must be givento a course of action should the takeoff becomeundesirable or unsafe. Mechanical failures,obstructions on the takeoff surface, and changingweather conditions are all factors that could com-promise the safety of a takeoff and constitute areason to abort. The decision to abort a takeoffshould be definitive and made as soon as anunsafe condition is recognized. By initiating theabort procedures early, more time and distancewill be available to bring the gyroplane to a stop. Alate decision to abort, or waiting to see if it will benecessary to abort, can result in a dangerous situ-ation with little time to respond and very fewoptions available.

When initiating the abort sequence prior to thegyroplane leaving the surface, the procedure isquite simple. Reduce the throttle to idle and allowt h egyroplane to decelerate, while slowly applying aftcyclic for aerodynamic braking. This techniqueprovides the most effective braking and slows theaircraft very quickly. If the gyroplane has left thesurface when the decision to abort is made,reduce the throttle until an appropriate descentrate is achieved. Once contact with the surface ismade, reduce the throttle to idle and apply aero-dynamic braking as before. The wheel brakes, ifthe gyroplane is so equipped, may be applied, asnecessary, to assist in slowing the aircraft.

ACCELERATE/STOP DISTANCEAn accelerate/stop distance is the length ofground roll an aircraft would require to accelerate

to takeoff speed and, assuming a decision to abortthe takeoff is made, bring the aircraft safely to astop. This value changes for a given aircraft basedon atmospheric conditions, the takeoff surface,aircraft weight, and other factors affecting per-formance. Knowing the accelerate/stop value foryour gyroplane can be helpful in planning a safetakeoff, but having this distance available does notnecessarily guarantee a safe aborted takeoff ispossible for every situation. If the decision to abortis made after liftoff, for example, the gyroplane willrequire considerably more distance to stop thanthe accelerate/stop figure, which only considersthe ground roll requirement. Planning a course ofaction for an abort decision at various stages ofthe takeoff is the best way to ensure the gyroplanecan be brought safely to a stop should the needarise.

For a gyroplane without a flight manual or otherpublished performance data, the accelerate/stopdistance can be reasonably estimated once youare familiar with the performance and takeoff char-acteristics of the aircraft. For a more accurate fig-ure, you can accelerate the gyroplane to takeoffspeed, then slow to a stop, and note the distanceused. Doing this several times gives you an aver-age accelerate/stop distance. When performancecharts for the aircraft are available, as in the flightmanual of a certificated gyroplane, accurateaccelerate/stop distances under various condi-tions can be determined by referring to the groundroll information contained in the charts.

LIFT-OFF AT LOW AIRSPEED AND HIGHANGLE OF ATTACKBecause of ground effect, your gyroplane mightbe able to become airborne at an airspeed lessthan minimum level flight speed. In this situation,the gyroplane is flying well behind the power curveand at such a high angle of attack that unless acorrection is made, there will be little or no accel-eration toward best climb speed. This condition isoften encountered in gyroplanes capable of jump takeoffs. Jumpingw i t h o u t

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sufficient rotor inertia to allow enough time toaccelerate through minimum level flight speed,usually results in your gyroplane touching downafter liftoff. If you do touch down after performing ajump takeoff, you should abort the takeoff.

During a rolling takeoff, if the gyroplane is forcedinto the air too early, you could get into the samesituation. It is important to recognize this situationand take immediate corrective action. You caneither abort the takeoff, if enough runway exists,or lower the nose and accelerate to the best climbspeed. If you choose to continue the takeoff, verifythat full power is applied, then, slowly lower thenose, making sure the gyroplane does not contactthe surface. While in ground effect, accelerate tothe best climb speed. Then, adjust the nose pitchattitude to maintain that airspeed.

COMMON ERRORSThe following errors might occur when practicinga lift-off at a low airspeed.

1. Failure to check rotor for proper operation,track, and r.p.m. prior to initiating takeoff.

2. Use of a power setting that does not simu-late a “behind the power curve” situation.

3. Poor directional control.

4. Rotation at a speed that is inappropriate forthe maneuver.

5. Poor judgement in determining whether toabort or continue takeoff.

6. Failure to establish and maintain properclimb attitude and airspeed, if takeoff is con-tinued.

7. Not maintaining the desired ground trackduring the climb.

PILOT-INDUCED OSCILLATION (PIO)Pilot-induced oscillation, sometimes referred to asporpoising, is an unintentional up-and-down oscil-lation of the gyroplane accompanied with alternat-ing climbs and descents of the aircraft. PIO isoften the result of an inexperienced pilot overcon-trolling the gyroplane, but this condition can alsobe induced by gusty wind conditions. While thiscondition is usually thought of as a longitudinalproblem, it can also happen laterally.

As with most other rotor-wing aircraft, gyroplanesexperience a slight delay between control inputand the reaction of the aircraft. This delay maycause an inexperienced pilot to apply more con-trol input than required, causing a greater aircraftresponse than was desired. Once the error hasbeen recognized, opposite control input is appliedto correct the flight attitude. Because of the natureof the delay in aircraft response, it is possible forthe corrections to be out of synchronization withthe movements of the aircraft and aggravate theundesired changes in attitude. The result is PIO,or unintentional oscillations that can grow rapidlyin magnitude. [Figure 21-1]

In gyroplanes with an open cockpit and limitedflight instruments, it can be difficult for an inexperi-enced pilot to recognize a level flight attitude dueto the lack of visual references. As a result, PIOcan develop as the pilot chases a level flight atti-tude and introduces climbing and descendingoscillations. PIO can also develop if a wind gustdisplaces the aircraft, and the control inputs made

Figure 21-1. Pilot-induced oscillation can result if the gyroplane’s reactions to control inputs are not anticipated and become out of phase.

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to correct the attitude are out of phase with the air-craft movements. Because the rotor disc angledecreases at higher speeds and cyclic controlbecomes more sensitive, PIO is more likely tooccur and can be more pronounced at high air-speeds. To minimize the possibility of PIO, avoidhigh-speed flight in gusty conditions, and makeonly small control inputs. After making a controlinput, wait briefly and observe the reaction of theaircraft before making another input. If PIO isencountered, reduce power and place the cyclic inthe position for a normal climb. Once the oscilla-tions have stopped, slowly return the throttle andcyclic to their normal positions. The likelihood ofencountering PIO decreases greatly as experi-ence is gained, and the ability to subconsciouslyanticipate the reactions of the gyroplane to controlinputs is developed.

BUNTOVER (POWER PUSHOVER)As you learned in Chapter 16—GyroplaneAerodynamics, the stability of a gyroplane isgreatly influenced by rotor force. If rotor force israpidly removed, some gyroplanes have a ten-dency to pitch forward abruptly. This is oftenreferred to as a forward tumble, buntover, orpower pushover. Removing the rotor force is oftenreferred to as unloading the rotor, and can occur ifpilot-induced oscillations become excessive, ifextremely turbulent conditions are encountered,or the nose of the gyroplane is pushed forwardrapidly after a steep climb.

A power pushover can occur on some gyroplanesthat have the propeller thrust line above the cen-ter of gravity and do not have an adequate hori-zontal stabilizer. In this case, when the rotor isunloaded, the propeller thrust magnifies the pitch-ing moment around the center of gravity. Unless acorrection is made, this nose pitching action could become self-sustaining andirreversible. An adequate horizontal stabilizerslows the pitching rate and allows time for recov-ery.

Since there is some disagreement between man-ufacturers as to the proper recovery procedure fort h i ssituation, you must check with the manufacturer ofyour gyroplane. In most cases, you need toremove power and load the rotor blades. Somemanufacturers, especially those with gyroplaneswhere the propeller thrust line is above the centerof gravity, recommend that you need to immediatelyremove power in order to prevent a powerpushover situation. Other manufacturers recom-mend that you first try to load the rotor blades. For

the proper positioning of the cyclic when loading upthe rotor blades, check with the manufacturer.

When compared to other aircraft, the gyroplane isjust as safe and very reliable. The most importantfactor, as in all aircraft, is pilot proficiency. Propertraining and flight experience helps prevent therisks associated with pilot-induced oscillation orbuntover.

GROUND RESONANCEGround resonance is a potentially damaging aero-dynamic phenomenon associated with articulatedrotor systems. It develops when the rotor bladesmove out of phase with each other and cause therotor disc to become unbalanced. If not corrected,ground resonance can cause serious damage in amatter of seconds.

Ground resonance can only occur while the gyro-plane is on the ground. If a shock is transmitted tothe rotor system, such as with a hard landing onone gear or when operating on rough terrain, oneor more of the blades could lag or lead and allowthe rotor system’s center of gravity to be displacedfrom the center of rotation. Subsequent shocks tothe other gear aggravate the imbalance causingthe rotor center of gravity to rotate around the hub.This phenomenon is not unlike an out-of-balancewashing machine. [Figure 21-2]

To reduce the chance of experiencing ground res-onance, every preflight should include a check forproper strut inflation, tire pressure, and lag-leaddamper operation. Improper strut or tire inflationcan change the vibration frequency of the air-frame, while improper damper settings change thevibration frequency of the rotor.

Figure 21-2. Taxiing on rough terrain can send a shock wave tothe rotor system, resulting in the blades of a three-bladed rotorsystem moving from their normal 120° relationship to each other.

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If you experience ground resonance, and the rotorr.p.m. is not yet sufficient for flight, apply the rotorbrake to maximum and stop the rotor as soon aspossible. If ground resonance occurs during take-off, when rotor r.p.m. is sufficient for flight, lift offimmediately. Ground resonance cannot occur inflight, and the rotor blades will automaticallyrealign themselves once the gyroplane is air-borne. When prerotating the rotor system prior totakeoff, a slight vibration may be felt that is a verymild form of ground resonance. Should this oscil-lation amplify, discontinue the prerotation andapply maximum rotor brake.

EMERGENCY APPROACH ANDLANDINGThe modern engines used for powering gyro-planes are generally very reliable, and an actualmechanical malfunction forcing a landing is not acommon occurrence. Failures are possible, whichnecessitates planning for and practicing emer-gency approaches and landings. The best way toensure that important items are not overlookedduring an emergency procedure is to use a check-list, if one is available and time permits. Most gyro-planes do not have complex electrical, hydraulic,or pneumatic systems that require lengthy check-lists. In these aircraft, the checklist can be easilycommitted to memory so that immediate action

can be taken if needed. In addition, you shouldalways maintain an awareness of your surround-ings and be constantly on the alert for suitableemergency landing sites.

When an engine failure occurs at altitude, the firstcourse of action is to adjust the gyroplane’s pitchattitude to achieve the best glide speed. Thisyields the most distance available for a given alti-tude, which in turn, allows for more possible land-ing sites. A common mistake when learningemergency procedures is attempting to stretch theglide by raising the nose, which instead results ina steep approach path at a slow airspeed and ahigh rate of descent. [Figure 21-3] Once you haveattained best glide speed, scan the area withingliding distance for a suitable landing site.Remember to look behind the aircraft, as well asin front, making gentle turns, if necessary, to seearound the airframe. When selecting a landingsite, you must consider the wind direction andspeed, the size of the landing site, obstructions tothe approach, and the condition of the surface. Asite that allows a landing into the wind and has afirm, smooth surface with no obstructions is themost desirable. When considering landing on aroad, be alert for powerlines, signs, and automo-bile traffic. In many cases, an ideal site will not beavailable, and it will be necessary for you to eval-uate your options and choose the best alternative.

For example, if a steady wind will allow a touch-down with no ground roll, it may be acceptable toland in a softer field or in a smaller area thanwould normally be considered. On landing, useshort or soft field technique, as appropriate, for thesite selected. A slightly higher-than-normalapproach airspeed may be required to maintainadequate airflow over the rudder for proper yawcontrol.

Figure 21-3. Any deviation from best glide speed will reduce the distance you can glide and may cause you to land short of a safe touch-down point.

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As with any aircraft, the ability to pilot a gyroplanesafely is largely dependent on the capacity of thepilot to make sound and informed decisions. Tothis end, techniques have been developed toensure that a pilot uses a systematic approach tomaking decisions, and that the course of actionselected is the most appropriate for the situation.In addition, it is essential that you learn to evalu-ate your own fitness, just as you evaluate the air-worthiness of your aircraft, to ensure that yourphysical and mental condition is compatible with asafe flight. The techniques for acquiring theseessential skills are explained in depth in Chapter14—Aeronautical Decision Making (Helicopter).

As explained in Chapter 14, one of the best meth-ods to develop your aeronautical decision makingis learning to recognize the five hazardous atti-tudes, and how to counteract these attitudes.[Figure 22-1] This chapter focuses on some exam-

ples of how these hazardous attitudes can applyto gyroplane operations.

IMPULSIVITYGyroplanes are a class of aircraft which can beacquired, constructed, and operated in ways unlikemost other aircraft. This inspires some of the most

exciting and rewarding aspects of flying, but it alsocreates a unique set of dangers to which a gyro-plane pilot must be alert. For example, a wide vari-ety of amateur-built gyroplanes are available,which can be purchased in kit form and assembledat home. This makes the airworthiness of thesegyroplanes ultimately dependent on the vigilanceof the one assembling and maintaining the aircraft.Consider the following scenario.

Jerry recently attended an airshow that had agyroplane flight demonstration and a number ofgyroplanes on display. Being somewhat mechani-cally inclined and retired with available spare time,Jerry decided that building a gyroplane would bean excellent project for him and ordered a kit thatday. When the kit arrived, Jerry unpacked it in hisgarage and immediately began the assembly. Asthe gyroplane neared completion, Jerry grewmore excited at the prospect of flying an aircraftthat he had built with his own hands. When thegyroplane was nearly complete, Jerry noticed thata rudder cable was missing from the kit, or per-haps lost during the assembly. Rather than con-tacting the manufacturer and ordering areplacement, which Jerry thought would be a has-sle and too time consuming, he went to his localhardware store and purchased some cable hethought would work. Upon returning home, he wasable to fashion a rudder cable that seemed func-tional and continued with the assembly.

Jerry is exhibiting “impulsivity.” Rather than takingthe time to properly build his gyroplane to thespecifications set forth by the manufacturer, Jerrylet his excitement allow him to cut corners by acting onimpulse, rather than taking the time to think thematter through. Although some enthusiasm is nor-mal during assembly, it should not be permitted tocompromise the airworthiness of the aircraft.Manufacturers often use high quality components,which are constructed and tested to standardsmuch higher than those found in hardware stores.This is particularly true in the area of cables, bolts,nuts, and other types of fasteners where strengthis essential. The proper course of action Jerryshould have taken would be to stop, think, andconsider the possible consequences of making an

Figure 22-1. To overcome hazardous attitudes, you must memo-rize the antidotes for each of them. You should know them so wellthat they will automatically come to mind when you need them.

Ch 22.qxd 7/15/2003 9:19 AM Page 22-1

impulsive decision. Had he realized that a broken rudder cable in flight could cause a loss of controlof the gyroplane, he likely would have taken thetime to contact the manufacturer and order a cablethat met the design specifications.

INVULNERABILITYAnother area that can often lead to trouble for agyroplane pilots is the failure to obtain adequateflight instruction to operate their gyroplane safely.This can be the result of people thinking thatbecause they can build the machine themselves,it must be simple enough to learn how to fly bythemselves. Other reasons that can lead to this problem can be sim-ply monetary, in not wanting to pay the money foradequate instruction, or feeling that because theyare qualified in another type of aircraft, flightinstruction is not necessary. In reality, gyroplaneoperations are quite unique, and there is no sub-stitute for adequate training by a competent andauthorized instructor. Consider the following scenario.

Jim recently met a coworker who is a certified pilotand owner of a two-seat gyroplane. In discussingthe gyroplane with his coworker, Jim was fasci-nated and reminded of his days in the military as ahelicopter pilot many years earlier. When offereda ride, Jim readily accepted. He met his coworkerat the airport the following weekend for a short flight and wasimmediately hooked. After spending severalweeks researching available designs, Jim decidedon a particular gyroplane and purchased a kit. He had it assem-bled in a few months, with the help and advice ofhis new friend and fellow gyroplane enthusiast.When the gyroplane was finally finished, Jimasked his friend to take him for a ride in his two-seater to teach him the basics of flying. The rest,he said, he would figure out while flying his own machine from a landing strip that hehad fashioned in a field behind his house.

Jim is unknowingly inviting disaster by allowinghimself to be influenced by the hazardous attitudeof “invulnerability.” Jim does not feel that it is pos-sible to have an accident, probably because of hispast experience in helicopters and from witness-ing the ease with which his coworker controlledthe gyroplane on their flight together. What Jim isfailing to consider, however, is the amount of timethat has passed since he was proficient in helicop-ters, and the significant differences between heli-copter and gyroplane operations. He is alsooverlooking the fact that his friend is a certificated

pilot, who has taken a considerable amount ofinstruction to reach his level of competence.Without adequate instruction and experience, Jimcould, for example, find himself in a pilot-inducedoscillation without knowing the proper techniquefor recovery, which could ultimately be disastrous.The antidote for an attitude of invulnerability is to realize that acci-dents can happen to anyone.

MACHODue to their unique design, gyroplanes are quiteresponsive and have distinct capabilities.Although gyroplanes are capable of incrediblemaneuvers, they do have limitations. As gyroplanepilots grow more comfortable with their machines,they might be tempted to operate progressivelycloser to the edge of the safe operating envelope.Consider the following scenario.

Pat has been flying gyroplanes for years and hasan excellent reputation as a skilled pilot. He hasrecently built a high performance gyroplane withan advanced rotor system. Pat was excited tomove into a more advanced aircraft because hehad seen the same design performing aerobaticsin an airshow earlier that year. He was amazed bythe capability of the machine. He had always feltthat his ability surpassed the capability of the air-craft he was flying. He had invested a largeamount of time and resources into the construc-tion of the aircraft, and, as he neared completionof the assembly, he was excited about the oppor-tunity of showing his friends and family his capa-bilities.

During the first few flights, Pat was not completelycomfortable in the new aircraft, but he felt that hewas progressing through the transition at a muchfaster pace than the average pilot. One morning,when he was with some of his fellow gyroplaneenthusiasts, Pat began to brag about the superiorhandling qualities of the machine he had built. Hisfriends were very excited, and Pat realized thatthey would be expecting quite a show on his nextflight. Not wanting to disappoint them, he decidedthat although it might be early, he would give thespectators on the ground a real show. On his firstpass he came down fairly steep and fast andrecovered from the dive with ease. Pat thendecided to make another pass only this time hewould come in much steeper. As he began torecover, the aircraft did not climb as he expectedand almost settled to the ground. Pat narrowlyescaped hitting the spectators as he was trying to recover from the dive.

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Pat had let the “macho” hazardous attitude influ-ence his decision making. He could have avoidedthe consequences of this attitude if he hadstopped to think that taking chances is foolish.

RESIGNATIONSome of the elements pilots face cannot be con-trolled. Although we cannot control the weather,we do have some very good tools to help predictwhat it will do, and how it can affect our ability tofly safely. Good pilots always make decisions thatwill keep their options open if an unexpectedevent occurs while flying. One of the greatest resources we have inthe cockpit is the ability to improvise and improvethe overall situation even when a risk elementjeopardizes the probability of a successful flight.Consider the following scenario.

Judi flies her gyroplane out of a small grass stripon her family’s ranch. Although the rugged land-scape of the ranch lends itself to the remarkablescenery, it leaves few places to safely land in theevent of an emergency. The only suitable place toland other than the grass strip is to the west on asmooth section of the road leading to the house.

During Judi’s training, her traffic patterns werealways made with left turns. Figuring this was howshe was to make all traffic patterns, she appliedthis to the grass strip at the ranch. In addition, shewas uncomfortable with making turns to the right.Since, the wind at the ranch was predominatelyfrom the south, this meant that the traffic patternwas to the east of the strip.

Judi’s hazardous attitude is “resignation.” She hasaccepted the fact that her only course of action isto fly east of the strip, and if an emergency hap-pens, there is not much she can do about it. Theantidote to this hazardous attitude is “I’m not helpless, I can makea difference.” Judi could easily modify her trafficpattern so that she is always within gliding distanceof a suitable landing area. In addition, if she wasuncomfortable with a maneuver, she could getadditional training.

ANTI-AUTHORITYRegulations are implemented to protect aviation personnel as well as the people who are notinvolved in aviation. Pilots who choose to operateoutside of the regulations, or on the ragged edge,eventually get caught, or even worse, they end uphaving an accident. Consider the following sce-nario.

Dick is planning to fly the following morning andrealizes that his medical certificate has expired.He knows that he will not have time to take a flightphysical before his morning flight. Dick thinks tohimself “The rules are too restrictive. Why should Ispend the time and money on a physical when Iwill be the only one at risk if I fly tomorrow?”

Dick decides to fly the next morning thinking thatno harm will come as long as no one finds out thathe is flying illegally. He pulls his gyroplane outfrom the hangar, does the preflight inspection, andis getting ready to start the engine when an FAAinspector walks up and greets him. The FAAinspector is conducting a random inspection andasks to see Dick’s pilot and medical certificates.

Dick subjected himself to the hazardous attitude of“anti-authority.” Now, he will be unable to fly, andhas invited an exhaustive review of his operation bythe FAA. Dick could have prevented this event ifhad taken the time to think, “Follow the rules. Theyare usually right.”

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ABSOLUTE ALTITUDE—The act-ual distance an object is above theground.

ADVANCING BLADE—The blademoving in the same direction asthe helicopter or gyroplane. Inrotorcraft that have counterclock-wise main rotor blade rotation asviewed from above, the advancingblade is in the right half of the rotordisc area during forward move-ment.

AIRFOIL—Any surface designedto obtain a useful reaction of lift, ornegative lift, as it moves throughthe air.

AGONIC LINE—A line alongwhich there is no magnetic varia-tion.

AIR DENSITY—The density of theair in terms of mass per unit vol-ume. Dense air has more mole-cules per unit volume than lessdense air. The density of airdecreases with altitude above thesurface of the earth and withincreasing temperature.

AIRCRAFT PITCH—When refer-enced to an aircraft, it is the move-ment about its lateral, or pitch axis.Movement of the cyclic forward oraft causes the nose of the helicop-ter or gyroplane to pitch up ordown.

AIRCRAFT ROLL—Is the move-ment of the aircraft about its longitudinal axis. Movement of thecyclic right or left causes the heli-copter or gyroplane to tilt in thatdirection.

AIRWORTHINESS DIRECTIVE—When an unsafe condition existswith an aircraft, the FAA issues anairworthiness directive to notify con-cerned parties of the condition andto describe the appropriate correc-

tive action.

ALTIMETER—An instrument thatindicates flight altitude by sensingpressure changes and displayingaltitude in feet or meters.

ANGLE OF ATTACK—The anglebetween the airfoil’s chord line andthe relative wind.

ANTITORQUE PEDAL—The pedalused to control the pitch of the tailrotor or air diffuser in a NOTAR®system.

ANTITORQUE ROTOR—See tailrotor.

ARTICULATED ROTOR—A rotorsystem in which each of the bladesis connected to the rotor hub insuch a way that it is free to changeits pitch angle, and move up anddown and fore and aft in its planeof rotation.

AUTOPILOT—Those units andcomponents that furnish a meansof automatically controlling the air-craft.

AUTOROTATION—The conditionof flight during which the mainrotor is driven only by aerodynam-ic forces with no power from theengine.

AXIS-OF-ROTATION—The imagi-nary line about which the rotorrotates. It is represented by a linedrawn through the center of, andperpendicular to, the tip-pathplane.

BASIC EMPTY WEIGHT—Theweight of the standard rotorcraft,operational equipment, unusablefuel, and full operating fluids,including full engine oil.

BLADE CONING—An upwardsweep of rotor blades as a result of

lift and centrifugal force.

BLADE DAMPER—A deviceattached to the drag hinge torestrain the fore and aft movementof the rotor blade.

BLADE FEATHER OR FEATHER-ING—The rotation of the bladearound the spanwise (pitchchange) axis.

BLADE FLAP—The ability of therotor blade to move in a verticaldirection. Blades may flap inde-pendently or in unison.

BLADE GRIP—The part of the hubassembly to which the rotor bladesare attached, sometimes referredto as blade forks.

BLADE LEAD OR LAG—The foreand aft movement of the blade inthe plane of rotation. It is some-times called hunting or dragging.

BLADE LOADING—The loadimposed on rotor blades, deter-mined by dividing the total weightof the helicopter by the combinedarea of all the rotor blades.

BLADE ROOT—The part of theblade that attaches to the bladegrip.

BLADE SPAN—The length of ablade from its tip to its root.

BLADE STALL—The condition ofthe rotor blade when it is operatingat an angle of attack greater thanthe maximum angle of lift.

BLADE TIP—The further most partof the blade from the hub of therotor.

BLADE TRACK—The relationshipof the blade tips in the plane ofrotation. Blades that are in trackwill move through the same planeof rotation.

GLOSSARY

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BLADE TRACKING—The mechan-ical procedure used to bring theblades of the rotor into a satisfacto-ry relationship with each otherunder dynamic conditions so thatall blades rotate on a commonplane.

BLADE TWIST—The variation inthe angle of incidence of a bladebetween the root and the tip.

BLOWBACK—The tendency ofthe rotor disc to tilt aft in forwardflight as a result of flapping.

BUNTOVER—The tendency of agyroplane to pitch forward whenrotor force is removed.

CALIBRATED AIRSPEED (CAS)—Indicated airspeed of an aircraft,corrected for installation andinstrumentation errors.

CENTER OF GRAVITY—The the-oretical point where the entireweight of the helicopter is consid-ered to be concentrated.

CENTER OF PRESSURE—Thepoint where the resultant of all theaerodynamic forces acting on anairfoil intersects the chord.

CENTRIFUGAL FORCE—Theapparent force that an object mov-ing along a circular path exerts onthe body constraining the objectand that acts outwardly away fromthe center of rotation.

CENTRIPETAL FORCE—Theforce that attracts a body toward itsaxis of rotation. It is opposite cen-trifugal force.

CHIP DETECTOR—A warningdevice that alerts you to anyabnormal wear in a transmissionor engine. It consists of a magnet-ic plug located within the transmis-sion. The magnet attracts anymetal particles that have comeloose from the bearings or othertransmission parts. Most chipdetectors have warning lights

located on the instrument panelthat illuminate when metal parti-cles are picked up.

CHORD—An imaginary straightline between the leading and trail-ing edges of an airfoil section.

CHORDWISE AXIS—A term usedin reference to semirigid rotorsdescribing the flapping or teeteringaxis of the rotor.

COAXIL ROTOR—A rotor systemutilizing two rotors turning in oppo-site directions on the same center-line. This system is used to elimi-nated the need for a tail rotor.

COLLECTIVE PITCHCONTROL—The control forchanging the pitch of all the rotorblades in the main rotor systemequally and simultaneously and,consequently, the amount of lift orthrust being generated.

CONING—See blade coning.

CORIOLIS EFFECT—The ten-dency of a rotor blade to increaseor decrease its velocity in its planeof rotation when the center ofmass moves closer or further fromthe axis of rotation.

CYCLIC FEATHERING—Themechanical change of the angle ofincidence, or pitch, of individualrotor blades independently of otherblades in the system.

CYCLIC PITCH CONTROL—Thecontrol for changing the pitch ofeach rotor blade individually as itrotates through one cycle to gov-ern the tilt of the rotor disc and,consequently, the direction andvelocity of horizontal movement.

DELTA HINGE—A flapping hingewith a skewed axis so that the flap-ping motion introduces a compo-nent of feathering that would resultin a restoring force in the flap-wisedirection.

DENSITY ALTITUDE—Pressurealtitude corrected for nonstandardtemperature variations.

DEVIATION—A compass errorcaused by magnetic disturbancesfrom the electrical and metal com-ponents in the aircraft. The correc-tion for this error is displayed on acompass correction card placenear the magnetic compass of theaircraft.

DIRECT CONTROL—The abilityto maneuver a rotorcraft by tiltingthe rotor disc and changing thepitch of the rotor blades.

DIRECT SHAFT TURBINE—Ashaft turbine engine in which thecompressor and power section aremounted on a common driveshaft.

DISC AREA—The area swept bythe blades of the rotor. It is a circlewith its center at the hub and has aradius of one blade length.

DISC LOADING—The total heli-copter weight divided by the rotordisc area.

DISSYMMETRY OF LIFT—Theunequal lift across the rotor discresulting from the difference in thevelocity of air over the advancingblade half and retreating blade halfof the rotor disc area.

DRAG—An aerodynamic force ona body acting parallel and oppositeto relative wind.

DUAL ROTOR—A rotor systemutilizing two main rotors.

DYNAMIC ROLLOVER—The ten-dency of a helicopter to continuerolling when the critical angle isexceeded, if one gear is on theground, and the helicopter is pivot-ing around that point.

FEATHERING—The action thatchanges the pitch angle of therotor blades by rotating themaround their feathering (spanwise)

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axis.

FEATHERING AXIS—The axisabout which the pitch angle of arotor blade is varied. Sometimesreferred to as the spanwise axis.

FEEDBACK—The transmittal offorces, which are initiated by aero-dynamic action on rotor blades, tothe cockpit controls.

FLAPPING HINGE—The hingethat permits the rotor blade to flapand thus balance the lift generatedby the advancing and retreatingblades.

FLAPPING—The vertical move-ment of a blade about a flappinghinge.

FLARE—A maneuver accom-plished prior to landing to slowdown a rotorcraft.

FREE TURBINE—A turboshaftengine with no physical connec-tion between the compressor andpower output shaft.

FREEWHEELING UNIT—A com-ponent of the transmission orpower train that automatically dis-connects the main rotor from theengine when the engine stops orslows below the equivalent rotorr.p.m.

FULLY ARTICULATED ROTORSYSTEM—See articulated rotorsystem.

GRAVITY—See weight.

GROSS WEIGHT—The sum ofthe basic empty weight and usefulload.

GROUND EFFECT—A usuallybeneficial influence on rotorcraftperformance that occurs while fly-ing close to the ground. It resultsfrom a reduction in upwash, down-wash, and bladetip vortices, whichprovide a corresponding decrease

in induced drag.

GROUND RESONANCE—Self-excited vibration occurring when-ever the frequency of oscillation ofthe blades about the lead-lag axisof an articulated rotor becomes thesame as the natural frequency ofthe fuselage.

GYROCOPTER—Trademarkapplied to gyroplanes designedand produced by the BensenAircraft Company.

GYROSCOPIC PRECESSION—An inherent quality of rotating bod-ies, which causes an applied forceto be manifested 90° in the direc-tion of rotation from the pointwhere the force is applied.

HUMAN FACTORS—The study ofhow people interact with their environment. In the case of gener-al aviation, it is the study of howpilot performance is influenced bysuch issues as the design of cock-pits, the function of the organs ofthe body, the effects of emotions,and the interaction and communi-cation with other participants in theaviation community, such as othercrew members and air traffic con-trol personnel.

HUNTING—Movement of a bladewith respect to the other blades inthe plane of rotation, sometimescalled leading or lagging.

INERTIA—The property of matterby which it will remain at rest or ina state of uniform motion in thesame direction unless acted uponby some external force.

IN GROUND EFFECT (IGE)HOVER—Hovering close to thesurface (usually less than onerotor diameter distance above thesurface) under the influence ofground effect.

INDUCED DRAG—That part ofthe total drag that is created by theproduction of lift.

INDUCED FLOW—The compo-nent of air flowing verticallythrough the rotor system resultingfrom the production of lift.

ISOGONIC LINES—Lines oncharts that connect points of equalmagnetic variation.

KNOT—A unit of speed equal toone nautical mile per hour.

L/DMAX—The maximum ratio

between total lift (L) and total drag(D). This point provides the bestglide speed. Any deviation fromthe best glide speed increasesdrag and reduces the distance youcan glide.

LATERIAL VIBRATION—A vibra-tion in which the movement is in alateral direction, such as imbalanceof the main rotor.

LEAD AND LAG—The fore (lead)and aft (lag) movement of the rotorblade in the plane of rotation.

LICENSED EMPTY WEIGHT—Basic empty weight not includingfull engine oil, just undrainable oil.

LIFT—One of the four main forcesacting on a rotorcraft. It acts per-pendicular to the relative wind.

LOAD FACTOR—The ratio of aspecified load to the total weight ofthe aircraft.

MARRIED NEEDLES—A termused when two hands of an instru-ment are superimposed over eachother, as on the engine/rotortachometer.

MAST—The component that sup-ports the main rotor.

MAST BUMPING—Action of therotor head striking the mast, occur-ring on underslung rotors only.

MINIMUM LEVEL FLIGHTSPEED—The speed below whicha gyroplane, the propeller of which

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is producing maximum thrust,loses altitude.

NAVIGATIONAL AID (NAVAID)—Any visual or electronic device,airborne or on the surface, thatprovides point-to-point guidanceinformation, or position data, to air-craft in flight.

NIGHT—The time between theend of evening civil twilight and thebeginning of morning civil twilight,as published in the American AirAlmanac.

NORMALLY ASPIRATED ENGINE—An engine that does not com-pensate for decreases in atmos-pheric pressure through tur-bocharging or other means.

ONE-TO-ONE VIBRATION—Alow frequency vibration having onebeat per revolution of the rotor.This vibration can be either lateral,vertical, or horizontal.

OUT OF GROUND EFFECT(OGE) HOVER—Hovering greaterthan one diameter distance abovethe surface. Because induceddrag is greater while hovering outof ground effect, it takes morepower to achieve a hover out ofground effect.

PARASITE DRAG—The part oftotal drag created by the form orshape of helicopter parts.

PAYLOAD—The term used forpassengers, baggage, and cargo.

PENDULAR ACTION—The lateralor longitudinal oscillation of thefuselage due to it being suspend-ed from the rotor system.

PITCH ANGLE—The anglebetween the chord line of the rotorblade and the reference plane ofthe main rotor hub or the rotorplane of rotation.

PREROTATION—In a gyroplane,

it is the spinning of the rotor to asufficient r.p.m. prior to flight.

PRESSURE ALTITUDE—Theheight above the standard pressurelevel of 29.92 in. Hg. It is obtainedby setting 29.92 in the barometricpressure window and reading thealtimeter.

PROFILE DRAG—Drag incurredfrom frictional or parasitic resist-ance of the blades passingthrough the air. It does not changesignificantly with the angle ofattack of the airfoil section, but itincreases moderately as airspeedincreases.

RESULTANT RELATIVE WIND—Airflow from rotation that is modifiedby induced flow.

RETREATING BLADE—Any blade,located in a semicircular part of therotor disc, where the blade directionis opposite to the direction of flight.

RETREATING BLADE STALL—Astall that begins at or near the tip ofa blade in a helicopter because ofthe high angles of attack requiredto compensate for dissymmetry oflift. In a gyroplane the stall occursat 20 to 40 percent outboard fromthe hub.

RIGID ROTOR—A rotor systempermitting blades to feather but notflap or hunt.

ROTATIONAL VELOCITY—Thecomponent of relative wind pro-duced by the rotation of the rotorblades.

ROTOR—A complete system ofrotating airfoils creating lift for ahelicopter or gyroplane.

ROTOR DISC AREA—See diskarea.

ROTOR BRAKE—A device usedto stop the rotor blades during

shutdown.

ROTOR FORCE—The force pro-duced by the rotor in a gyroplane.It is comprised of rotor lift and rotordrag.

SEMIRIGID ROTOR—A rotor sys-tem in which the blades are fixed tothe hub but are free to flap andfeather.

SETTLING WITH POWER—Seevortex ring state.

SHAFT TURBINE—A turbineengine used to drive an outputshaft commonly used in helicop-ters.

SKID—A flight condition in whichthe rate of turn is too great for theangle of bank.

SKID SHOES—Plates attached tothe bottom of skid landing gearprotecting the skid.

SLIP—A flight condition in whichthe rate of turn is too slow for theangle of bank.

SOLIDITY RATIO—The ratio ofthe total rotor blade area to totalrotor disc area.

SPAN—The dimension of a rotorblade or airfoil from root to tip.

SPLIT NEEDLES—A term used todescribe the position of the twoneedles on the engine/rotortachometer when the two needlesare not superimposed.

STANDARD ATMOSPHERE—Ahypothetical atmosphere based onaverages in which the surfacetemperature is 59°F (15°C), thesurface pressure is 29.92 in. Hg(1013.2 Mb) at sea level, and thetemperature lapse rate is approxi-mately 3.5°F (2°C) per 1,000 feet.

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STATIC STOP—A device used tolimit the blade flap, or rotor flap, atlow r.p.m. or when the rotor isstopped.

STEADY-STATE FLIGHT—A con-dition when a rotorcraft is instraight-and-level, unacceleratedflight, and all forces are in balance.

SYMMETRICAL AIRFOIL—An air-foil having the same shape on thetop and bottom.

TAIL ROTOR—A rotor turning in aplane perpendicular to that of themain rotor and parallel to the longi-tudinal axis of the fuselage. It isused to control the torque of themain rotor and to provide move-ment about the yaw axis of the hel-icopter.

TEETERING HINGE—A hinge

that permits the rotor blades of asemirigid rotor system to flap as aunit.

THRUST—The force developedby the rotor blades acting parallelto the relative wind and opposingthe forces of drag and weight.

TIP-PATH PLANE—The imaginarycircular plane outlined by the rotorblade tips as they make a cycle ofrotation.

TORQUE—In helicopters with asingle, main rotor system, the ten-dency of the helicopter to turn inthe opposite direction of the mainrotor rotation.

TRAILING EDGE—The rearmostedge of an airfoil.

TRANSLATING TENDENCY—

The tendency of the single-rotorhelicopter to move laterally duringhovering flight. Also called tail rotordrift.

TRANSLATIONAL LIFT—Theadditional lift obtained when enter-ing forward flight, due to theincreased efficiency of the rotorsystem.

TRANSVERSE-FLOW EFFECT—A condition of increased drag anddecreased lift in the aft portion ofthe rotor disc caused by the airhaving a greater induced velocityand angle in the aft portion of thedisc.

TRUE ALTITUDE—The actualheight of an object above meansea level.

TURBOSHAFT ENGINE—A tur-bine engine transmitting powerthrough a shaft as would be foundin a turbine helicopter.

TWIST GRIP—The power controlon the end of the collective control.

UNDERSLUNG—A rotor hub thatrotates below the top of the mast,as on semirigid rotor systems.

UNLOADED ROTOR—The stateof a rotor when rotor force has beenremoved, or when the rotor is oper-ating under a low or negative Gcondition.

USEFUL LOAD—The differencebetween the gross weight and thebasic empty weight. It includes theflight crew, usable fuel, drainableoil, if applicable, and payload.

VARIATION—The angular differ-ence between true north and mag-netic north; indicated on charts byisogonic lines.

VERTICAL VIBRATION—A vibra-tion in which the movement is upand down, or vertical, as in an out-of-track condition.

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VORTEX RING STATE—A tran-sient condition of downward flight(descending through air after justpreviously being accelerateddownward by the rotor) duringwhich an appreciable portion ofthe main rotor system is beingforced to operate at angles ofattack above maximum. Blade stallstarts near the hub and progressesoutward as the rate of descentincreases.

WEIGHT—One of the four mainforces acting on a rotorcraft.Equivalent to the actual weight ofthe rotorcraft. It acts downwardtoward the center of the earth.

YAW—The movement of a rotor-craft about its vertical axis.

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ABORTED TAKEOFF, GYROPLANE 21-1ACCELERATE/STOP DISTANCE 21-1AERODYNAMICS 2-1, 3-1, 16-1

autorotation, 3-8forward flight, 3-5general, 2-1gyroplane, 16-1helicopter, 3-1hovering flight, 3-1rearward flight, 3-8sideward flight, 3-8turning flight, 3-8vertical flight, 3-4, 16-1

AERONAUTICAL DECISION MAKING (ADM) 14-1, 22-1decision-making process, 14-3definitions, 14-2error chain, 14-1factors affecting decision making, 14-5hazardous attitudes, 14-6, 22-1operational pitfalls, 14-8origin, 14-2pilot error, 14-1risk management, 14-4situational awareness, 14-8stress management, 14-6use of resources, 14-6workload management, 14-7

AGONIC LINE 12-5AIRCRAFT LIGHTING 13-3AIRFOIL 2-1

angle of attack, 2-2camber, 2-2center of pressure, 2-1chord line, 2-2leading edge, 2-2pitch angle, 2-2relative wind, 2-2resultant relative wind, 3-6rotational relative wind, 3-6span, 2-1trailing edge, 2-2twist, 2-1

AIRSPEED INDICATOR 12-1, 18-4AIR TAXI 9-9AIRWORTHINESS DIRECTIVE 6-4ALTIMETER 12-2, 18-4ANGLE OF ATTACK 2-2ANTI-ICING SYSTEMS 5-11ANTITORQUE PEDALS 4-3ANTITORQUE SYSTEM FAILURE 11-11ANTITORQUE SYSTEMS 1-2

tail rotor, 1-2fenestron, 1-2NOTAR®, 1-2

APPROACHESconfined area, 10-7crosswind, 9-20night, 13-5

normal to a hover, 9-19normal to the surface, 9-20pinnacle, 10-8shallow approach, 10-5steep, 10-4

ARM 7-4ASYMMETRICAL AIRFOIL 2-1ATTITUDE INDICATOR 12-3ATTITUDE INSTRUMENT FLYING 12-1AUTOKINESIS 13-3AUTOPILOT 5-10AUTOROTATION 11-1

aerodynamics, 3-8, 16-1during instrument flight, 12-19from a hover, 11-4power recovery, 11-3straight-in, 11-2with turn, 11-3

AXIS OF ROTATION 2-2

BASIC EMPTY WEIGHT 7-1BERNOULLI’S PRINCIPLE 2-3BLADE

coning, 3-2driven region, 3-9, 16-2driving region, 3-9, 16-2feather, 1-1flap, 1-1, 16-6, 20-1lead/lag, 1-1reverse flow, 16-3stall, 11-10stall region, 3-9, 16-2

BLOWBACK 3-8BUNTOVER 21-3

CARBURETOR 5-7heat, 5-8ice, 5-7

CENTER OF GRAVITY 7-2aft CG, 7-2forward CG, 7-2lateral, 7-3, 7-7

CENTER OF PRESSURE 2-1, 16-5CENTRIFUGAL FORCE 3-2, 3-8CENTRIPETAL FORCE 3-8CLUTCH

belt drive, 5-4centrifugal, 5-4freewheeling unit, 5-4sprag, 5-4

COANDA EFFECT 1-3COCKPIT MANAGEMENT 20-1COLLECTIVE CONTROL, GYROPLANE 17-2COLLECTIVE PITCH CONTROL 4-1

INDEX

A

B

C

Index.qxd 7/15/2003 2:26 PM Page I-1

COLLECTIVE PITCH/THROTTLE COORDINATION 4-2COMPASS CORRECTION CARD 12-5COMPASS DEVIATION 12-5COMPASS ERRORS 12-4COMPASS TURNS 12-17CONFINED AREA OPERATIONS

approach, 10-7takeoff, 10-8

CONING 3-2CONING ANGLE 18-1CORIOLIS EFFECT 3-2CORRELATOR/GOVERNOR 4-2CREW RESOURCE MANAGEMENT 14-2CYCLIC CONTROL, GYROPLANE 17-1CYCLIC PITCH CONTROL 4-2

DATUM 7-3DECISION-MAKING PROCESS 14-3DENSITY ALTITUDE 8-1, 20-5DIRECT CONTROL 15-2DISC LOADING 2-4DISSYMMETRY OF LIFT 3-6, 16-3, 20-1DIVERSION 11-15DRAG 2-5

form, 2-5induced, 2-5parasite, 2-6profile, 2-5rotor, 16-4skin friction, 2-5total, 2-6

DUAL ROTOR SYSTEM 1-1DYNAMIC ROLLOVER 11-7

EFFECTIVE TRANSLATIONAL LIFT 3-5ELECTRICAL SYSTEMS 5-8EMERGENCIES

aborted takeoff, 21-1approach and landing, 21-3autorotation, 11-1buntover, 21-3dynamic rollover, 11-7ground resonance, 11-7, 21-3instrument flight, 12-18lift-off at low airspeeds and high angles of attack, 21-1lost procedures, 11-16low G conditions, 11-10low rotor r.p.m. and blade stall, 11-10mast bumping, 11-10pilot-induced oscillation, 21-2power pushover, 21-3retreating blade stall, 11-6settling with power, 11-5systems malfunction, 11-11vortex ring state, 11-5

EMERGENCY EQUIPMENT AND SURVIVAL GEAR 11-16,21-4ENGINE

reciprocating, 5-1, 18-1turbine, 5-1

ENGINE INSTRUMENTS 18-3ENGINE STARTING PROCEDURE 9-2, 20-1ENVIRONMENTAL SYSTEMS 5-10EYE 13-1

cones, 13-1

rods, 13-2FALSE HORIZON 13-3FENESTRON TAIL ROTOR 1-2FLIGHT AT SLOW AIRSPEEDS 20-12FLIGHT CONTROLS 1-3, 4-1

antitorque pedals, 4-3collective pitch, 4-1, 17-2cyclic pitch, 4-2, 17-1rudder, 17-2swash plate assembly, 5-5throttle, 4-1, 17-1

FLIGHT DIVERSION 11-15FLIGHT INSTRUMENTS 12-1

airspeed indicator, 12-1, 18-4altimeter, 12-2, 18-4attitude indicator, 12-3heading indicator, 12-3magnetic compass, 12-4turn-indicators, 12-4vertical speed indicator, 12-2

FLIGHT MANUAL (See rotorcraft flight manual)FORCES IN A TURN 3-8FOUR FORCES

drag, 2-5, 16-4lift, 2-3, 16-4thrust, 2-5, 16-4weight, 2-4

FREEWHEELING UNIT 5-4FUEL INJECTION 5-8FUEL SYSTEMS 5-6

FULLY ARTICULATED ROTOR 1-1, 5-4, 18-1

GO-AROUND 9-20, 20-15GOVERNOR 4-2

failure, 11-14GROSS WEIGHT 7-1GROUND EFFECT 3-3GROUND HANDLING 18-4GROUND REFERENCE MANEUVERS 9-14, 20-8

rectangular course, 9-14, 20-8s-turns, 9-16, 20-10turns around a point, 9-17, 20-11

GROUND RESONANCE 11-7, 21-3GYROPLANE

components, 15-2instruments, 18-3stability, 16-5types, 15-1

GYROSCOPIC INSTRUMENTS 12-3attitude indicator, 12-3

D

E

F

G

Index.qxd 7/15/2003 2:26 PM Page I-2

heading indicator, 12-3turn indicators, 12-4

GYROSCOPIC PRECESSION 3-4HANG TEST 19-4HAZARDOUS ATTITUDES 14-5

anti-authority, 14-6, 22-3impulsivity, 14-6, 22-1invulnerability, 14-6, 22-1macho, 14-6, 22-2resignation, 14-6, 22-2

HEADING INDICATOR 12-3HEIGHT/VELOCITY DIAGRAM 11-4, 19-3HELICOPTER SYSTEMS 5-1

anti-icing, 5-11autopilot, 5-10carburetor, 5-7clutch, 5-4electrical, 5-8engine, 5-1environmental, 5-10flight control, 4-1fuel, 5-6hydraulics, 5-9main rotor, 5-4pitot-static, 12-1stability augmentation system, 5-10swash plate assembly, 5-5tail rotor drive, 5-3transmission, 5-3

HIGH RATE OF DESCENT 20-12HINGES 5-5HOVERING

aerodynamics, 3-1flight, 9-5

HOVERING OPERATIONSautorotation, 11-4forward flight, 9-7rearward flight, 9-8sideward flight, 9-7turn, 9-6vertical takeoff, 9-5

HOVER TAXI 9-9HUMAN FACTORS 14-1

HYDRAULIC FAILURE 11-14

INDUCED DRAG 2-5INDUCED FLOW 3-6INSTRUMENT CROSS-CHECK 12-5INSTRUMENT FLIGHT 12-5

aircraft control, 12-7bank control, 12-9emergencies, 12-18straight-and-level flight, 12-7straight climbs, 12-11straight descents, 12-14takeoff, 12-19

turns, 12-15unusual attitudes, 12-18

INSTRUMENT INTERPRETATION 12-6INSTRUMENT TURNS 12-15

30° bank turn, 12-17 climbing and descending turns, 12-17compass turns, 12-17timed turns, 12-16turns to a predetermined heading, 12-16

ISOGONIC LINES 12-5LANDING

crosswind, 9-11, 20-14high-altitude, 20-14illusions, 13-4night, 13-5normal, 20-13running/roll-on, 10-5short-field, 20-13slope, 10-6soft-field, 20-14

LANDING GEAR 1-2, 15-3, 18-4LAW OF CONSERVATION OF ANGULAR MOMENTUM 3-2L/DMAX 2-6LIFT 2-3, 16-4

Bernoulli’s Principle, 2-3magnus effect, 2-3Newton’s Third Law of Motion, 2-4

LIFT-OFF AT LOW AIRSPEED AND HIGH ANGLE OFATTACK 21-1LIFT-TO-DRAG RATIO 2-6LOAD FACTOR 2-4LOSS OF TAIL ROTOR EFFECTIVENESS 11-12LOST PROCEDURES 11-16LOW G CONDITIONS 11-10

LOW ROTOR RPM 11-10LTE (See loss of tail rotor effectiveness)MAGNETIC COMPASS 12-4

acceleration/deceleration error, 12-5compass correction card, 12-5magnetic deviation, 12-5magnetic dip, 12-5turning error, 12-5variation, 12-4

MAGNUS EFFECT 2-3MAIN ROTOR SYSTEM 1-1, 5-4

combination, 5-5fully articulated, 1-1, 5-4rigid, 1-2, 5-5semirigid, 1-2, 5-5

MANEUVERS 9-1, 10-1, 20-1after landing and securing, 9-20, 20-15approaches, 9-19climb, 9-13, 20-6

I

L

M

H

Index.qxd 7/15/2003 2:26 PM Page I-3

confined area operations, 10-7crosswind landing, 9-20, 20-14crosswind takeoff, 9-11, 20-4descent, 9-14, 20-6engine start, 9-2, 20-1flight at slow airspeeds, 20-12go-around, 9-20, 20-15ground reference maneuvers, 9-14, 20-8high-altitude landing, 20-14high-altitude takeoff, 20-4high rate of descent, 20-12hovering, 9-5jump takeoff, 20-5maximum performance takeoff, 10-2normal landing, 20-13normal takeoff, 20-3pinnacle operations, 10-8preflight, 9-1, 20-1prerotation, 20-2quick stop, 10-3rapid deceleration, 10-3ridgeline operations, 10-8rotor engagement, 9-2running/rolling landing, 10-5running/rolling takeoff, 10-2shallow approach, 10-5short-field landing, 20-13short-field takeoff, 20-4slope operations, 10-6soft-field landing, 20-14soft-field takeoff, 20-5steep approach, 10-4straight-and-level flight, 9-12, 20-6takeoff from a hover, 9-10takeoff from the surface, 9-11taxiing, 9-8, 20-1traffic patterns, 9-18turns, 9-12, 20-7vertical takeoff, 9-5

MAST BUMPING 11-10MAXIMUM GROSS WEIGHT 7-1MAXIMUM PERFORMANCE TAKEOFF 10-2MEL (See minimum equipment list)MINIMUM EQUIPMENT LIST 9-1

MOMENT 7-4

NEVER EXCEED SPEED (VNE) 3-7, 6-2NEWTON’S THIRD LAW OF MOTION 2-4NIGHT APPROACH 13-5NIGHT FLIGHT 13-4

approach, 13-5collision avoidance, 13-5engine starting and rotor engagement, 13-4en route procedures, 13-5landing, 13-5preflight, 13-4takeoff, 13-4taxi technique, 13-4

NIGHT MYOPIA 13-3NIGHT OPERATIONS 13-1

NIGHT PHYSIOLOGY 13-1NIGHT SCANNING 13-2NIGHT VISION 13-2

NOISE ABATEMENT PROCEDURES 9-20

NO TAIL ROTOR 1-2OPERATIONAL PITFALLS 14-8PARASITE DRAG 2-6PAYLOAD 1-1, 7-1PENDULAR ACTION 3-2, 16-5PERFORMANCE CHARTS 8-3, 19-2

climb, 8-5hovering, 8-3takeoff, 8-5

PERFORMANCE FACTORS 8-1altitude, 8-2atmospheric pressure, 8-1density altitude, 8-1humidity, 8-2temperature, 8-2weight, 8-2winds, 8-2

PILOT ERROR 14-1PILOT-INDUCED OSCILLATION (PIO) 21-2PINNACLE OPERATIONS

approach, 10-8landing, 10-8takeoff, 10-9

PITCH, AIRCRAFT 2-2PITCH HORN 5-4PITOT-STATIC INSTRUMENTS 12-1

airspeed indicator, 12-1, 18-4altimeter, 12-2, 18-4errors, 12-2vertical speed indicator (VSI), 12-2

PLACARDS 6-3POH (See rotorcraft flight manual)POWERPLANT 1-3, 15-2POWER PUSHOVER 21-3PREFLIGHT INSPECTION 9-1, 20-1

night, 13-4PREROTATE 15-2, 18-2, 20-2PREROTATOR 18-2

electrical, 18-3hydraulic, 18-2mechanical, 18-2tip jets, 18-3

PRESSURE ALTITUDE, 8-1

PROFILE DRAG 2-5

P

Q

N

O

Index.qxd 7/15/2003 2:26 PM Page I-4

PROPELLER THRUST LINE 16-5QUICK STOP 10-3RAPID DECELERATION 10-3RECIPROCATING ENGINE 5-1RECONNAISSANCE PROCEDURES

ground, 10-1high, 10-1low, 10-1

RECTANGULAR COURSE 9-14, 20-8REFERENCE DATUM 7-3RELATIVE WIND 2-2RESULTANT RELATIVE WIND 3-6RETREATING BLADE STALL 11-6, 16-3REVERSE FLOW 16-3RIGID ROTOR 1-2, 5-5RISK ELEMENTS 14-4RISK MANAGEMENT 14-4ROLL, AIRCRAFT 2-2ROTATIONAL RELATIVE WIND 3-6ROTORCRAFT FLIGHT MANUAL 6-1, 19-1

aircraft systems and description, 6-4emergency procedures, 6-3, 19-3general information, 6-1gyroplane, 19-1handling, servicing, and maintenance, 6-4helicopter, 6-1normal procedures, 6-3operating limitations, 6-1performance, 6-3, 19-2safety and operational tips, 6-4supplements, 6-4weight and balance, 6-4, 19-1

ROTOR DRAG 16-4ROTOR ENGAGEMENT 9-2ROTOR FORCE 16-3ROTOR LIFT 16-4ROTOR SAFETY 9-2ROTOR SYSTEMS 5-4, 18-1

combination, 5-5fully articulated, 1-2, 5-4, 18-1semirigid, 1-2, 5-5, 18-1

rigid, 1-2, 5-5RUDDER 17-2

SAFETY CONSIDERATIONS 9-2SEMIRIGID ROTOR SYSTEM 1-2, 5-5, 18-1SETTLING WITH POWER 11-5SITUATIONAL AWARENESS 14-8SKID 9-13, 20-7SKIN FRICTION DRAG 2-5SLIP 9-13, 20-7SLIP/SKID INDICATOR 12-4, 18-4SLOPE OPERATIONS

landing, 10-6takeoff, 10-6

STABILITY AUGMENTATION SYSTEM (SAS) 5-10STABILITY, GYROPLANE 16-5

center of pressure, 16-5fuselage drag, 16-5horizontal stabilizer, 16-5pitch inertia, 16-5propeller thrust line, 16-5rotor force, 16-6trimmed condition, 16-6

STANDARD ATMOSPHERE 8-1STANDARD-RATE TURN 12-4STARTING PROCEDURE 9-2STATIC STOPS 5-5STEADY-STATE FLIGHT 2-4STEEP TURNS 20-8STRESS MANAGEMENT 14-6S-TURNS 9-16, 20-10SWASH PLATE ASSEMBLY 5-5SYMMETRICAL AIRFOIL 2-1SYSTEM MALFUNCTIONS 11-11

antitorque, 11-11governor, 11-14

hydraulic, 11-14main drive shaft, 11-14

TACHOMETER 5-3, 18-3TAIL ROTOR 1-2, 5-3TAIL ROTOR FAILURE 11-11TAIL SURFACES 15-2TAKEOFF

confined area, 10-8crosswind, 9-11, 20-4from a hover, 9-10from the surface, 9-11high altitude, 20-4jump, 20-5maximum performance, 10-2night, 13-4normal, 20-3pinnacle, 10-9running/rolling, 10-2short-field, 20-4slope, 10-6soft-field, 20-5to a hover, 9-5

TAXIING 9-8, 20-1air, 9-9hover, 9-9night, 13-4surface, 9-9

TEETER BOLT 18-1TEETERING HINGE 5-5THROTTLE 4-1, 17-1THRUST 2-5, 16-4TIP JETS 18-3TIP-PATH PLANE 2-2, 9-5TIP SPEED 3-7, 16-1TORQUE 1-1, 3-1TOTAL DRAG 2-6TOWER BLOCK 18-1TOWER PLATE 18-1TRAFFIC PATTERNS 9-18

R

S

T

Index.qxd 7/15/2003 2:26 PM Page I-5

TRANSLATING TENDENCY 3-1TRANSLATIONAL LIFT 3-5TRANSMISSION 5-3TRANSVERSE FLOW EFFECT 3-6TRUE ALTITUDE 8-1TURBINE ENGINE 5-1TURN COORDINATOR 12-4TURN-AND-SLIP INDICATOR 12-4TURNS 9-12, 12-15, 20-7

aerodynamics, 3-8TURNS AROUND A POINT 9-17, 20-11UNANTICIPATED YAW 11-12UNDERSLING ROTOR 3-3, 18-1UNLOADED ROTOR 21-3

UNUSUAL ATTITUDES 12-18USEFUL LOAD 7-1VENTURI EFFECT 2-3VERTICAL SPEED INDICATOR (VSI) 12-2VIBRATIONS 11-14

low frequency, 11-15medium and high frequency, 11-15

VISION IN FLIGHT 13-1night, 13-2

VISUAL ILLUSIONS 13-3autokinesis, 13-3false horizon, 13-3landing, 13-4night myopia, 13-3

VNE (See never exceed speed)VORTEX RING STATE 11-5VSI 12-2

VX 20-3VY 20-3

WEIGHT 2-4, 7-1limitations, 7-1

WEIGHT AND BALANCE 7-1, 19-1definitions, 7-1, 7-3, 7-4

WEIGHT AND BALANCE METHODS 7-4combination method, 7-6computational method, 7-4

loading-chart method, 7-5WINGS 15-3WORKLOAD MANAGEMENT 14-7YAW, AIRCRAFT 2-5

V

WU

Y

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