Army Aviation Digest - Oct 1955

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LIBRARY USAARUIT RUCI E ALA

ARMY AVIATION SCHOOLC MP RUCKER ALABAMA

OCTOBER 955 VOLUME NUMBER 9


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ARMY AVIATION SCHOOL

COMMANDANTBrigadier General Carl I. Hutton USA

ASSISTANT COMMANDANTColonel Jules E. Gonseth Jr.

DIRECTOR OF INSTRUCTIONLieutenant Colonel James W. Hill Jr.


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VOLUME 1

ARMY AVIATIONIGESTOCTOBER 955

CONTENTS

NUMBER 9

THE COMMANDANT S COLUMN... . . . . . . . . . 3Brigadier General Carl I. Hutton USAPROBLEMS IN HELICOPTER PILOT TRAINING. . . . . . . . 5Major Hubert D. Gr:ddis ArtilleryHELICOPTER INSTRUMENT PILOT TRAINING. . . . . . . . . 9Captain Richard W. Kohlbrand InfantryRETREATING BLADE STALL.. . . . . . . . . . . . . . . . 17Private First Class Stephen D. RemingtonROTOR LIGHTING SYSTEM. . . . . . . . . . . . . . . . . . . . . . . . . . . 23UR HIGHLIGHTS 25Captain Fred R Reed Transporation CorpsBOOKS FOR THE ARMY AVIATOR... . 26GR Y HA I R 29

COVER: The steep climb of this L20 graphically illustrates theBeaver's capability of getting off short runways. The tail wheel clears

a 50foot barrier set up at the end of a 200yard runway.

This copy is not for sale. It is intended for more than one reader.PLEASE READ IT AND PASS IT ALONG


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EDITOR IN CHIEFCaptain Weyrnan S. CarverASSISTANT EDITOR IN CHIEF

Captain Richard W KohlbrandEDITOR

LeGene Lott

The printing of this publication has been approved by theDirector of the Bureau of the Budget 13 August 1954.

The RMY VI TION DIGEST is an official publication of the Department of the rmy published monthly underthe supervision of the Commandant rmy Aviation School.The mission of the RMY VI TION DIGEST is to provideinformation of an operational or functional nature concerningsafety and aircraft accident prevention training maintenanceoperations research and development aviation medicine andother related data.

Manuscripts photographs and other illustrations pertaining to the above subjects of interest to personnel concernedwith A rmy aviation are invited. Direct communication sauthorized to: Editor-in-Chief AOMY VI TION DIGESTrmy Aviation School Camp Rucker Alabama.

Unless otherwise indicated material in the RMYVI TION DIGEST may be reprinted provided credit isgiven to the RMY VI TION DIGEST and to the author.


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TH COMMANDANT S COLUMNBrigadier General Carl I. HuHon US

The views expressed in this article are the author's and are notnecessarily those 0 the Department of the Army.- The Editor

Civilian and rmy viationFortunately it (Army Aviation) is a branch of military aviation in which civilian pilots have not only an interest but, you mightsay, a background. -Leighton Collins: Editorial, Anny Aviation,

Air Facts, April 1955.Military aviation has numerous points of contact with civilianaviation operations. Some of the obvious ones are the Reserve Programs, the National Guard, contract training, contracted troop move

ments, and the potential use of the airlines to supplement MATS intime of emergency. The Army participates to a limited extent in thesecontacts, but it would appear that much more could be done to establish closer relationship with civilian flying. This is an area which allservices have overlooked, but the oversight is more serious to theArmy because of the similarity of much of civilian flying to Annyflying.The civilian flying here referred to is that which centers aroundthe fixed-base operators. t includes airplane owners, private andcommercial pilots, flying fanners, crop dusters, and perhaps therapidly expanding group of corporation pilots. These are the peoplewhose flying experience gives them a background in Army Aviation.Some specific projects have been tried. Several years agoarrangements were made for Reserve Anny aviators to maintain


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4 ARMY AVIATION DIGESTtheir flying proficiency by contract with fixed-base operators. Thisattempt was not successful and it may have discouraged additionalexperiments. .A draftee coming into the Army gets no recognition for his pilotexperience. There is no way for him to come into Army Aviationbesides the basic training-OCS-flying school cycle which would takea minimum of 8 weeks of his service if he could move promptlyfrom one phase to the next. Of course this would be improbable.A member of the Reserve National Guard or Civil Air Patrolwho wishes. to become qualified in Army Aviation must now come onactive duty for the period of the course of instruction. Many find thisto be impossible.The ROTC would appear to offer an opportunity to combineadvanced military training with aviation training.These are simply a few areas in which something could be doneto establish closer contact with civilian aviators. Each area is a fairlycomplicated subject and most of them have a history of previousattempts. The fact that the attempts have been unsuccessful shouldnot deter further efforts. The rewards to the Army would be verygreat indeed if we could take advantage of the neglect which has leftthe field of civilian aviation relatively unexploited in NationalDefense.

This is the seventh in a series of columns written by BrigadierGeneral Carl I. Hutton Commandant of the Army Aviation Schoolfor the ARMY AVIATION DIGEST. The Editor


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PROBLEMS IN HELICOPTERPILOT TR INING

M aior Hubert D. Gaddis rtill ry

The views expressed in this article are the author s and are not ne ssarily thoseof the Department 0 the rmy or 0 The rmy Aviation School.- The Editor

How important is fixed-wing experience to the training of helicopter pilots? The Army was confronted with this problem in 1952when it became necessary to graduate helicopter pilots as quickly aspossible to fill the demand for personnel in the then relatively newcargo helicopter battalions.The time element was a critical factor, and the question theArmy had to answer was: What advantage is prior flying experiencefrom the standpoint of safety, economy, ease of instruction, andrequired time in the training of helicopter pilots?

Late in 1950 tables of organization and equipment for cargohelicopter battalions and companies were established in the Transportation Corps. These new TOE s created a requirement whichnecessitated the immediate training of individuals as cargo helicopter pilots. In January 1951, the Army Cargo Helicopter PilotsCourse (ACHPC) was established at the Army Aviation School.At the time of the introduction of the cargo helicopter into Armyoperations, helicopter pilot training was confined to rated Armyaviators who, for the most part, had extensive flying experience. Inline with this policy, the ACHPC program was originally opened toformerly rated military and civilian pilots who were on active dutyas enlisted men. They were to receive officer-candidate-type training.in conjunction with flying training and graduate as warrant officerpilots in the Transportation Corps. Those selected for the first four


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ARMY AVIATION DIGEST Octoberclasses had fixed-wing experience ranging from 60 ~ o 8,000 flyinghours and, in aircraft, from J 3 Cubs to B-29 s.Aptitudes and progress displayed by individual students were.varied, but the average student soloed the helicopter with 8 to 12hours instruction. Students in the first class were given approximately75 hours total flight instruction. As training experience and datawere gained during the first three classes, total flying time in thecourse was progressively increased. The fourth class was given 110hours in order to meet the higher standards established throughdevelopment of the cargo helicopter program. Instructor personnelto support the ACHPC were selected from each class.Beginning with the fifth c l s s ~ transition training in the utilitytype helicopter (H-19 and H-25) was included, along with additionalground school subjects, thus lengthening the ACHPC course ofinstruction to 22 weeks and approximately 150 hours of total flyingtime. This 22-week course is still in effect.

During 1952 applicants for cargo helicopter pilot training whohad previous fixed-wing experience dwindled. In order to fill theneeds of the cargo helicopter battalions and companies, prerequisiteswere modified to permit individuals without flying experience toenter training.

Fixed Wing TrainingThe helicopter, because of its complexity of control, is moredifficult to learn to fly, coordination-wise, than the fixed-wing air-

Major Hubert D. Gaddis is the Assistant Director of theDepartment of Rotary Win,g Training, Army Aviation School, CampRucker, Ala. He received his pilot training in the Air TrainingDetachment, Fort Sill, Okla., in 1942. Additionally, he is a graduateof the Bell Aircraft Corporations Helicopter Mechanics (1946) andHelicopter Pilots (1947) Courses, and of.Southern Airways FlightInstructor Training Course 1951). During World War II h wasassigned to the 28th Infantry Division s a pilot, and in the KoreanWar he served s Commanding Officer of both the 8191st HelicopterAmbulance Evacuation Army Unit and the First Helicopter Ambulance Company. He is instrument rated, qualified in all Army fixedand rotary-wing aircraft, and has logged over 4 100 hours pilottime.-The Editor


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1955 PROBLEMS IN HELICOPTER PILOT TRAINING 7craft, and not as forgiving of mistakes. Numerous problems wereencountered by experienced fixed-wing pilots while undergoing transition to the helicopter, and it was believed by many authorities thatindividuals not familiar with fixed-wing flight would find rotarywing training extremely difficult_ On the other hand, some authoritiesthought it possible that the difficulties would be reduced with nonflying personnel since fixed-wing habits would not have been established.So the question arose: Would familiarization training in thefixed-wing, because of its comparative stability and ease of control,better prepare the student for learning to fly the helicopter?Expense and time were primary considerations_ A helicoptercosts 32,000 and a fixed-wing trainer, 11,000. Flight trainingwould run approximately 90 per hour in the helicopter as comparedto 35 per fixed-wing hour.Minor accidents in a fixed-wing, such as a hard landing, groundloops, damage to a wing tip or prop, are easily repaired and range inthe 50 to 350 class. In the helicopter, b e c ~ s e of the high cost ofparts, it is virtually impossible to have a minor accident. As anexample, damage to a rotor blade tip can necessitate the replacementof a 1,553 pair of blades, while slight damage to a fixed-wing aircraft wing tip would cost approximately 13. Initial cost, plus costof operation, pointed to giving as much training as possible in fixedwing aircraft._

The amount of time needed to produce a qualified cargo helicopter pilot was equally important. Would fixed-wing trainingshorten this time?Experimental lasses

To answer these questions, the Army Aviation School designated four classes composed of personnel without flying experienceas experimental. Each class was divided into two groups, one groupreceiving all their training in helicopters and the second receivingfixed-wing training prior to beginning the helicopter course.The fixed-wing sections of the four classes-were given 20,30,40,and 80 hours respectively in the L-19. Results of the first two classesshowed that a small amount of fixed-wing time lent confusion to thestudents during the helicopter transitioning period. For example,with approximately 30 to 40 hours a student's knowledge of flying


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8 ARMY AVIATION DIGESTwas limited. However, during this time he was forming a foundationof fixed-wing flying theory, methods, and aerodynamics. Transferring at this particular time proved prior fixed-wing training anobstacle because students found nomenclature, aerodynamics, terms,flight characteristics, and methods of control too different.Controls were confusing in that the student was accustomed tocoordinating with equal pressure and movement of the stick and rudder in the fixed-wing when making turns; whereas in the helicoptercyclic stick alone is used to execute a coordinated level tum, andpedals are used strictly as an antitorque control. Further, since students were accustomed to the relatively fast control response of thefixed-wing, they found the time delay between the instant the controlis applied until it becomes effective in the rotor system extremelydifficult to take into account. Additionally, there were several students who were able to solo an L-19 but could not solo a elicopter.

Habits Carried OverStudents who received 80 hours in the L-19 did adapt them

selves more readily to instruction and the interpretation of instruments, but they had considerable difficulty in breaking fixed-winghabits which are unsafe in helicopter flying. For example, back stickwhen executing a landing (i.e., pulling the stick all the way 10 therear was the primary unsafe carry-over from fixed-wing training.When landing a fixed-wing, the student s instructor was constantlyreminding him to get the tail down. Helicopter running landings,running take-offs, and particularly touch-down autorotations aremaneuvers in which the fixed-wing habit of back stick is dangerous.As the helicopter must be in a level attitude upon contact with theground, forward pressure of the cyclic is necessary when collectivepitch is applied, or the nose will come up. A three-point attitudewould mean touching down on the rear of the skids and the tail rotorguard. The helicopter would then bounce forward on the skids,which, with back stick, would result in the tail boom s beingcut off by the main rotor. This back cyclic tendency showed upthroughout the basic phase of flying training, usually in an abnormalsituation.Overall, the students who received the 80 hours fixed-wing timerequired as much flying time to solo the helicopter and the sameamount of flying time to complete the course as those. who receivedall their training in helicopters. Continued on page 34


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1955 HELICOPTER INSTRUMENT PILOT TRAINING 11pilots becoming instrument qualified, the Army Aviation Schoolestablished a test project to determine whether instrument flight isfeasible, with currently available instrumentation, in the utility-typehelicopter (H-19 and H-25) and whether instrument flight techniquescould be integrated into present helicopter pilot training.

The test project proved that, within limitations, instrument flightis practicable in the utility-type helicopter. (See Helicopter Instrument Flying, ARMY AVIATION DIGEST, June 1955, for resultsof preliminary tests conducted in the project.) Recently, furtherexperiments have resulted in the development of instructional techniques, and recommendations have been made for practical helicopter instrument flight courses. In anticipation of approval of suchcourses, a program is now in effect at the Army Aviation School totrain instrument instructor pilots. In addition, future experimentswill include the instrumentation of an H-13 for instrument flightevaluation.

Instrument lightMany interesting aspects of helicopter instrument flight wererevealed during the test project and subsequent experiments. Peculiarities encountered can be best illustrated by first describing whathappens when a pilot, unfamiliar with the interpretation of instruments in the helicopter, enters actual instrument conditions, or whathappens during his first experience under the hood.Upon entering instrument conditions, the pilot may hold the air

craft steady for approximately 1 minute, in exceptional cases, for 2minutes. But normally he can hold the aircraft for only 30 seconds.Unusual sensations caused by the pendular action of the helicopter sfuselage cause him to make a correction, unnecessarily or in thewrong direction. Then he notices that the instruments are off in relation to the desired flight attitude. Because of the comparatively largemovement of the artificial horizon and oscillations of the tum needle,he attempts an equally large control correction. After the first fewcorrections are made, the pilot is helplessly overcontrolling. As thependular motion of the fuselage increases with overcontrolling, thepilot succumbs to vertigo. The pilot quickly loses control of the aircraft, but, unlike the diving spiral in the case of a fixed-wing aircraft,a typical path of descent cannot be predicted. In most instances, thepilot will hold a steep tum, but the tum might be climbing or diving.


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2 ARMY AVIATION DIGEST OctoberInstrument Peculiarities

The inherent instability of the helicopter, its slow cruIsIngspeeds, and the pendular action of the fuselage are the primarycauses of the peculiarities of helicopter instrument flying. The pendular action, or rolling and yawing tendencies, causes vertigo todevelop quickly. This action, coupled with the slow cruising speed,also causes heading changes which require training to interpret properly. In moderately turbulent air, the instruments will indicate relatively large attitude changes .and appear to be lagging, which in turncauses overcontrolling. The gyro horizon precesses in turns of 90or 180 degrees; and, prior to leveling out of such a tum, the artificialhorizon indicates a slight dive even though the helicopter is level. Ina 360-degree turn, however, the precession is, cancelled out. The tumneedle, under moderately turbulent air conditions, oscillates backand forth, requiring interpolation of an average reading. However,by using other instruments as a cross check, the pilot can discountthis difficulty with the tum needle. The absence of any feel of thecontrol stick, plus the characteristic instability of the aircraft, makeshelicopter instrument flying a s ~ i s of corrections. The pilot thenbecomes tense, and fatigue results.Vertigo was the most prevalent pilot-reaction problem encountered during the experimental classes. In the early stages of training, it was extremely difficult for students to overcome and continuedto occur throughout training, although in later training phases pilotswere able to control the sensation. Other pilot-reaction difficultiesincluded learning to interpolate the instruments, dividing attention,making immediate small corrections in response to relatively largedeviations of instrument indications, and relaxing. Fatigue presentedquite a problem, especially in the early stages of training.

riIt FactorIn radio work, test students had a tendency to undercorrect fordrift. Because of the slow speed of the helicopter, large drift corrections are necessary to maintain a given tract in a cross-wind condi

tion. Under the hood, these corrections appear unusual to the pilot,and he tends to reduce them. The drift correction problem is especially critical in holding patterns. For example, in figuring the o r-rected heading for a 20-knot cross wind, the angle or degree of correction is doubled, and 40 degrees must be added to or subtracted


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1955 HELICOPTER INSTRUMENT PILOT TRAINING 3from the outbound heading. In cross winds complete lBO-degreeturns have been made within the cone of silence.Radio tuning presented still another problem. For the purposeof training the student pilot handled all his own radio tuning. It wasdiscovered that because of the constant watch required by the flightinstruments and because the pilot had no particular feel of the cyclicstick control was extremely difficult while diverting attention to theradios.

adio WorkPeculiarities of helicopter instrument flight presented severalproblems relative to radio work. In low frequency range orientationproblems the true-fade method proved to take an excessive amount

of time. In several instances the standard 15 minutes allowed for anapproach was exceeded and more time had to be requested. Underactual conditions the pilot could run out of fuel before completingthe procedure. To shorten the length of time required for a true fadeorientation the loop antenna was used to assist in quadrant identification by taking a wing-tip bearing. In ILS approaches bends in theapproach beam are more apparent causing a chasing of the deviationneedle. Establishing and holding a constant heading overcomes thispeculiarity. GCA approaches present no particular problem otherthan its being rather difficult to make the 2- and 3-degree correctionsrequested by the controller. Such corrections are impossible in turbulent air since the aircraft will yaw 10 degrees to either side of thedesired heading. Even under such conditions test students were ableto make very satisf


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14 ARMY AVIATION DIGESTinstrument locator system, and marker beacon. A dual set of instruments should be installed in the utility and cargo helicopters. Closecoordination with industry should be maintained to aid in the development of visual navigational equipment, a reliable attitude gyrodesigned specifically for helicopters, an autopilot for utility- andcargo-type helicopters, an airspeed indicator acurate from 0 to 15knots, and self-contained navigational equipment. To provide stability for the H-25 to facilitate its utilization as an instrument trainerthe differential delta-3 hinge stabilizing device should be installed.

In addition, personnel conducting the test project have recommended establishment, in the vicinity of the Army Aviation School,of a 100-mile airway consisting of a low frequency range, omni, ILS,and a GCA unit with homer and radar surveillance. It has been further recommended that use of this airway be restricted to helicoptertraining.

Threefold urposeOn the basis of conclusions drawn from the test project, which

included two experimental classes, Army Aviation School personnelhave proposed a long-range helicopter instrument training programwith a threefold purpose. At this writing the proposed program isdesigned to:1. Qualify helicopter pilots not now instrument trained._ Qualify selected helicopter pilots who are instrument rated to serve as instrument instructors and examiners

in the unit.3. Provide instrument training for future Army cargohelicopter pilots.

Qualification of helicopter pilots not now instrument trained isrecommended to be accomplished by special courses established inoperating units. Five weeks in duration, the course would include 50hours of hooded flight, 35 hours in the instrument flight simulator,and 75 hours of associated ground school subjects. Instructor personnel to conduct these courses would be trained at the Army AviationSchool to insure continuity of instruction in the helicopter units.t has also been recommended that rated pilots be instrumentqualified in fixed-wing aircraft prior to enrollment in primary helicopter training. Additionally, a 4-week extension of the advancedhelicopter course at the Army Aviation School has been recommended


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H-19 INSTRUMENT FLIGHT SIMULATOR- Above the instrument panelof a helicopter flight simulator recently delivered to the Instrument Div.Dept. of Fixed-Wing Training Army Aviation School Camp Rucker Ala.Below the trainer with side panels removed. Manufactured by Link AviationInc. the trainer was modified by Stanley Aviation Corp.


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6 ARMY AVIATION DIGESTto allow time for check-outs and an instrument familiarization program in the utility-type helicopter.

To provide instrument training for Army cargo helicopterpilots, it has been recommended that the present cargo course beextended 4 weeks. Students could then be given 30 hours of hoodedflight, plus 25 hours in the instrument flight trainer and additionalground school subjects.Personnel conducting tests and experiments at the Army A viation School believe the proposed training program will adequatelyprepare Army helicopter pilots for safe instrument flights at airspeeds above 35 knots per hour.

Experimental Classes onducted. Two experimental classes, conducted in accordance with theproposed program, have satisfactorily completed the training. In thebasic phase, students were given 22 2 hours of dual instruction

under the hood, 71/ 2 hours of buddy riding, and 2 hours in theLink trainer. The advanced phase consisted of 15 dual hood hours,5 hours of buddy riding, and 15 hours in the Link. Students attendedthe ground school portion of the Army Aviation School fixed-winginstrument course.The basic phase was designed to teach the student interpretationof instruments; unusual instrument positions; and A, 13 and vertical-Spatterns. It also included practice instrument GCA let-downs. Theadvance phase consisted chiefly of radio work, including omni orientation procedure and practice, holding patterns and low approaches,low frequency range orientation procedure and practice, holding patterns and let-downs; and homing with the manual loop. Instructionwas presented by lessons, with the student required to attain a certainproficiency before continuing to the next.

In conjunction with the test, Army Aviation School personnelare maintaining close liaison with the following installations in orderto correlate all available information pertaining to instrument flying:NACA, Langley Field, Va.; HMX Squadron, Quantico, Va.; NAS,Pensacola, Fla.; HELSON 2, Ream Field, San Diego, Calif.; PiaseckiAircraft Corporation, Morton, Pa.; Bell Aircraft Corporation, FortWorth, Tex.; and Los Angeles Airways, Los Angeles, Calif. Theseorganizations have been working with the development of helicopter instrumentation and radio navi- Continued on page 35


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RETRE TING BL DE ST LLrivate First Class Stephen D Remington

The views expressed in this article are the authors and are not necessarily thoseof the Department of the rmy or of The rmy Aviation School.- The Editor

Of all the aerodynamic peculiarities of the helicopter, retreating blade stall is perhaps the most interesting. Whereas, in the fixedwing type aircraft stalling is associated with low-speed flight characteristics, the maximum speed obtainable of the conventional helicopter is limited by retreating blade stall.How does blade stall occur? During forward flight, the helicopter rotor blade not only encounters the rotational velocity, butalso the forward flight velocity. The retreating blade will encounterlower velocities, whereas the advancing blade will be operating in ahigher relative velocity, since it has rotational velocity plus the forward velocity of the helicopter.

In order to balance the lift forces across the rotor disc, theretreating blade must operate at higher angles of attack as the forward speed increases. The change in angle of attack, w ith azimuthpositiort to correct for dissymmetry of lift, is taken care of automatically by flapping of the rotor system about its flapping hinges .As the advancing blade flaps upward due to its increase in lift fromthe forward flight velocity, its angle of attack is reduced. Conversely,the retreating blade will flap downward, increasing the angle ofattack of blade elements operating in that region and, therefore,increasing the lift to maintain lateral equilibrium of the rotor system. At some particular forward speed, the retreating blade willreach an angle of attack at which that airfoil will stall. t should benoted that the maximum force for upward flapping occurs on theadvancing side ; but, due to a phase lag of one-fourth cycle, the blade


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18 ARMY AVIATIO DIGEST Octoberreaches its maximum upward displacement at a forward position.Also there are other effects such as coning w ~ i h cause flapping ofthe rotor system in other azimuth positions but they are secondary toflapping due to velocity differential.Experimentation has shown that retreating blade stall can occuron any portion of the retreating region depending on the aerodynamic characteristics of the rotor system and not necessarily occurat the tip only. The stalled region will cover an azimuth range fromabout 180 to 320 degrees.The root section of a retreating blade will experience a reversedflow and stall in forward flight at all times but its effect is insignificant to the pilot. Associated with blade stall will be a loss of lift onthe stalled portion of the blade and an increase in profile drag. Helicopter blade sections are usually symmetrical airfoils with near-zeropitching moments below the stall; but once the section is stalledlarge pitching moments occur which are undesirable from a controland vibration standpoint.

Design onsiderationsThe helicopter is primarily a machine designed to hover; andalthough high forward speed is desirable the designer must be care

ful not to sacrifice hovering ability appreciably to gain speed.For maximum efficiency the modem helicopter is designed tooperate in ranges where blade stalling begins to appear. Some stalling is tolerable the operational limit being 15 to 20 per cent of thedisc area Stalling in excess of this area will cause power requirements to increase 20 to 30 per cent. Control forces and vibration

become prohibitive under highly stalled conditions.Blade stalling cannot be eliminated entirely but there are

Private First lass Remington is assigned s a helicoptermechanic with Board No.6 CONARC, Camp Rucker, Ala. He t-tended the University of Minnesota and the University of Wichita,where h majored in aeronautical engineering. Prior to his entry toactive duty, he was employed s an aeronautical research engineer,Helicopter Division, Cessna Aircraft Co., where he did extensiveresearch on retreating blade stall. In addition to his engineeringtraining, he is a licensed pilot with approximately 150 hours pilottime.-The Editor


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1955 RETREATING BLADE STALL 19several methods by which stall can be delayed, allowing gains inforward speed.

One means used on most modern helicopters is to twist theblades, giving them a washout or lowered pitch of 6 to 8 degreestoward the tips. This reduces the high tip loadings; consequently theblade tip angles of attack are reduced, delaying stall.A reduction in fuselage and landing gear parasite drag willreduce the forward vector tilt of the rotor and the inflow, therebyreducing the mean lift coefficient and tip angles of attack. An aerodynamically clean helicopter fuselage will contribute much toward ,a higher forward speed. Several examples of clean helicopter designare presently flying. The Sikorsky XH-39, the first to have retractablelanding gear, set the world -speed record for helicopters at 156 mph.The Cessna CH-1 was designed for high performance with cleanaerodynamic lines and has the highest VNE (never-exceed velocity)of all CAA licensed helicopters. The streamlined version of the BellH-13G, the model 47H has an increased top speed, although thebasic components and engine are identical to the G-model except forthe streamlined fuselage and landing gear.

Unloaded RotorA reduction in blade loading will decrease blade angles ofattack. This can be accomplished in many ways, all of which are notefficient. An increase in solidity with the same rpm will increase thetop speed, but hovering efficiency will decrease. A two-speed rotorsystem can be operated at low speed and high angles of attack forefficient hovering and can be shifted to a higher rpm for forward

flight, but complexities of the system would be great. High tip speedsalso introduce another aerodynamic barrier to forward speed in theform of compressibility effects on the advancing blade.Fixed wings, to unload the rotor in forward flight, can -alsoincrease forward speed by reducing blade angles, but there is aweight penalty to be paid for the addition of the wings. It is only another step from the addition of the wings to the helicopter to therealm of the convertiplanes, which are in the research stage at present. The McDonnell XV-1 utilizes the unloaded rotor principle .

irfoil DesignAnother method of improving blade stall characteristics, and

perhaps the most important, is to improve the blade airfoil section.


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20 ARMY AVIATION DIGEST OctoberThis includes, first, the proper choice of high lift airfoils withouthigh drag and pitching moments. To utilize a good airfoil to its fullest, the proper blade structure material should be used to maintaintrue contour and to avoid any surface irregularities. Metal bladeshave proved to have good aerodynamic properties with high stallingangles and lower profile drag than corresponding wood blades. Someresearch work is being done to delay retreating blade stall by highlift devices which allow the blade to go to higher angles of attackwithout stalling, thus permitting the helicopter to attain higher speedswith the same configuration. Boundary layer control (see September1955 issue of the ARMY AVIATION DIGEST) is the medium bywhich much of this work is being accomplished and promises to be anaid for helicopter designers of cargo-type craft . Helicopter blades inservice should be kept free of slung grease, dirt, bugs, and otherforeign matter; and particular attention should be paid to the bladesurface to maintain smoothness by repairing any scratches or erosion.

Prevention of lade Stallt is the pilot s responsibility to avoid serious blade stall by notonly adhering to flight restrictions but also by recognizing situationswhich could cause blade stall if the helicopter s speed or attitudewere not altered.Blade stall in steady forward flight is not a serious danger sinceample warning is given to the pilot in the form of increasing vibration and stick forces. The speed at which blade stall appears is par

tially a function of the gross weight, tip speed, and the density altitude. Therefore, a pilot can be flying well under VNE of the helicopter and still encounter blade stall if m neuvering loads are high orsevere gust conditions are met. Loss of rot >r rpm and high g loadswhile maneuvering will cause premature stalling, which often givesthe pilot little warning when encountered suddenly.As the density altitude increases, the helicopter blade anglesincrease to provide the same lift in the less dense air. Therefore, themaximum speed will have to be adjusted according to the altitude atwhich the helicopter is flying. The H-19, for instance, decreased VNE4 to 5 knots for each 1 000 feet increase in altitude. Most FlightHandbooks give charts for VNE versus altitude.

n increase in gross weight or load factor will reduce VNEappreciably. The H-19 will experience a decrease of 15 knots in the


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1955 RETREATING BLADE STALL 21speed at which blade stall occurs for each increase of 1,000 poundsin gross weight. t is evident that a high speed pullout of several g'scan easily cause severe blade stall. The performance of the CessnaCH 1 is a good example of the effect of gross weight on VNE. At2,600 pounds gross, the CH-1 has a VNE of 122 mph at .sea level.The VNE drops to 112 mph at 2,800 pounds and is reduced to 103mph at a maximum gross weight of 3,000 pounds. In most helicopters the pilot must mentally calculate the VNE of the helicopter for~ v r y flight condition, the main parameters being gross weight anddensity altitude.

Correctit e ActionWhat can the pilot do once blade stall is encountered? Recommended procedure as stated in most Flight Handbooks include fourbasic corrective actions: reduce collective pitch, increase rotor speed,reduce forward speed, and reduce altitude.

ConclllsionRetreating blade stall will be ever present with conventionalhelicopters, its main effect being a limiting factor for forward speed

and altitude. Designers are able to delay blade stall to increase speed,but future gains will be small without resorting to convertiplanetypes of aircraft. From the safety standpoint, blade stall need nothave serious effects, but the pilot must know the limitations of thehelicopter and must recognize blade stall when it does occur.

The first balloon used in combat was an aerial observation postemployed in 1794 by the French in the battle of Fleurus, during apolice action against the Austrians.


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A NIGHTFLYING HELICOPTER. its rotor tips lighted by an experimentalsystem traces an unusual pattern of arcs in this time exposure. Heavy traces oflight at bottom resulted from the plane's hovering before starting ascent. Thephotographer used a flash bulb to freeze the helicopter midway in its climb.


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ROTOR LIGHTING SYST MThe flying saucer scare may have a brief revival if a new, stillexperimental rotor blade lighting system becomes standard equipment on night-flying helicopters.The lights are mounted in the tips of the rotor blade, and inflight the rapidly revolving blades create the eerie, circular light pat

tern illustrated on the opposite page. Although somewhat sensationalin appearance, the new lighting system is being developed to servetwo important functions: (1) to distinguish helicopters from fixedwing aircraft at night and (2) to facilitate night formation flying inhelicopters. Helicopters equipped with blade . ip lights are easilyidentified as far away as 5 miles, even against a background of citylights.Helicopters are presently equipped with conventional green and

red lig4ts on the fuselage to identify the right and left sides of theaircraft. However, because of the peculiar maneuverability of thehelicopter which enables it to move both forward and backward, arotor blade lighting system is highly desirable as a safety factor during p.ight flights. With a lighting system installed in the rotor blades,horizontal direction as well as vertical motion of the helicopter isinstantly apparent .Additionally, the constantly revolving circle oflight clearly distinguishes the diameter of the rotor blades, a safetyfactor important in night formation flying and to night landings andtake-off s during concentrated operations. .Two types of rotor blade tip lights are being tested. One typeuses red and green bulbs, producing a circle which is green on theright side and red on the left side. The switching on and off ofthe red and green bulbs,is automatically timed with the turning of therotor. This color system makes any change in the flight path of theaircraft readily discernable to pilots of other helicopters in formation or to other approaching aircraft. The second type of light usesblue bulbs on both rotor tips. With this arrangement, the rotor pathappears as a blue circle.The lighting system as a whole is being developed by the KamanAircraft Corporation, Bloomfield, Conn., under contract with theNavy. t is supplied with power from the 28-volt electrical system of


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4 ARMY AVIATION DIGEST

the HTK-1 helicopter with which experiments are being conducted.A system of silver slip rings and brushes at the blade hub transferselectrical power from the mast to the blades.A clear plastic housing in the rotor blade tip enclQses the lampand is designed to follow the blade contour as closely as possible soas not to affect the aerodynamic blade design. Operating at 12 voltsthe lamp is supplied with power through a resistance cable inside theblade which drops the voltage to the required level.

High Centrifugal ForcesIn conjunction with the Kaman Corporation WestinghouseElectric Corporation Bloomfield N. J. has developed an aircraft

lamp for the system which will withstand centrifugal forces up to1,000 times the force of gravity.The greatest problem encountered in developing the lamp wasaccording to the developing finn arriving at one with a reasonablelife-span under the high centrifugal forces existing at the blade

tip. These forces can exceed 700g on present helicopters ~ d reach1,000g under certain speed conditions. The lamp developed willstand 1 000g which means that each part of the lamp is subjected toa force 1,000 times its normal weight.The final result of a series of gradually improved designs is a

lamp with closely spaced rigidly supported filament wires. In orderto provide the light intensity required the lamp has two tightly coiledfilaments in series. The lamp itself produces about 35 candlepowerbut reflectors in the blade tips increase the effective output approximately nine times. Fpur heavy filament supports serve as lead-inwires and are imbedded in a massive glass mount. In helicopter application the axis of the lamp coincides with the longitudinal axis ofthe blade.

This article w s prepared by the ARMY AVIATION DIGEST staffThe views expressed are not necessarily those of the Department ofthe Army or of The Army Aviation School. The Editor


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UR HI HLI HTSaptain Fred R. Reed Transporation Corps

The views expressed in this article are the authors and are not necessarily those0 the Department 0 the Army or 0 The Army Aviation School.- The Editor

The word report unfortunately has an adverse effect on mostpersonnel. Immediately, a report is classified as more paper work,more red tape, more harassment.. Such an attitude applied to the Unsatisfactory EquipmentReport System established by SR 700-45-5 will tend to limit theurgently required information from the users of equipment in thefield. t is not intended to imply that Unsatisfactory Reports on Transportation Corps air items take precedence over other items of equipment, but it is desired to emphasize the safety of flight aspects.Realizing that one's life and the proper functioning of any aircraftmay depend upon the timely submission of an Unsatisfactory Reportfrom someone halfway around the world certainly should removeany restrictive thinking toward submission of the reports.

What can be reported? Almost any unsatisfactory condition.The following are examples that have been furnished the field but arewell worth repeating.(a) Failure or malfunction of Army TransportationCorps air items, equipment, or material used by Department

of the Army aviati?n activities prior to its p r ~ s c r i e d overhaul or replacement time.

(b) Unsatisfactory design of equipment or material.(c) Defects due to faulty material, workmanship, orquality inspection.(d) Deterioration of equipment or material due toeffects of climatic or environmental conditions.(Continued on page 36


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OOKSFor the rmy viator

GENERAL BILLY MITCHELL, CHAMPION OF AIR DE-FENSE-Burlingame Roger. (McGraw-Hill Book Company, Inc.,330 West 42nd St., New York 6, N. Y., 1952. 3.00)Y BROTHER BILL, THE LIFE OF GENERAL BILLY

MITCHELL--Mitchell Ruth. (Harcourt, Brace and Company,Inc., 383 Madison Ave., New York 17, N Y., 1953. 4.00)General Mitchell is still important to Army aviation because thecontroversies and the emotional reactions which he stimulated operate to this day to limit the scope of the employment of aircraft inthe ground battle. These two books show how the hysteria persists.The. legend has become so strong that calmness and reason seem to

evaporate when his name is mentioned. His dramatics appear toinfect his biographers to the detriment of good reading. Thesebooks, albeit unconsciously, 'will tell the young Army aviator whatthe shouting is about.Both books contain too much emphasis upon Mitchell's rightnessor wrongness. In spite of near-canonization, he was human; and wecan see at this point in history that he was sometimes right and sometimes wrong. t looks now that he was right about the creation of aseparate air force, but wrong in the assumption that everything thatflies must belong ipso facto to the Air Force. He was right in assessingthe value of aircraft against battleship fleets, but wrong in his analysis of what to do about it. Had the United States followed his advice,there would have been no Fast Carrier Task Forces to drive the Japanese from the Pacific. He was r ~ h t in advocating more direct responsibility to aviators, but decidedly wrong in his proposal to subjectcivil aviation to the strangling effect of military control.

The Army still suffers in its aviation efforts because of theseaI).cient arguments. VTOL's, convertiplanes, helicopters, individuallift devices, and many other types of aircraft have a rightful place inArmy aviation, but the patterns of thought developed by Bill Mitchellstifle our progress. Reading these books will help to an understandingof why this is so.


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BOOKS FOR THE ARMY AVIATOR 27NUCLE R PHYSICS-Heisenberg , W. (Philosophical Library,Inc., 15 East 40th St., New York 16, N. Y., 1953. 4.75)

Written by the Director of the Max Planck Institute of Physics,this book was originally based on a series of lectures and is intendedfor readers who have no previous training in theoretical physics.

t begins with a short, interesting history of the views aboutatoms in antiquity and the development of atomic theory through theclose of the Nineteenth Century. The way is thus prepared for themain subject of the book, which includes radioactivity, the bindingenergy r nuclei, nuclear structure, and artificially induced nucleartransmutations. The author makes no claim of bringing the subjectof nuclear physics up to date, but gives the reader a good basicknowledge from which to pursue this rapidly expanding field.

The author points out that, in practical application, nuclearprocesses, like chemical processes, first can be applied to produce amore valuable material out of one of lesser value; and, secondly,they can be instrumental in producing energy. A brief discussion ofwhat is being done, and what can be done, in the fields of chemistry,biology, and bichemistry for peacetime harnessing of atomic energymakes an interesting conclusion to a physics book which is free ofmathematical formulas. Eighteen halftones and thirty-four illustrations help clarify the basic principles of p h y s i s ~ molecules, and theatom.

SONG O TH SKY-Murchie Gu y Jr. (Houghton Mifflin Company, 2 Park St., Boston 7 Mass., 1954. 5.00)A former war correspondent writes of the thing which is a part

of the aviator's being the adventure of the sky. He puts into wordsexperiences so familiar to aviators th3;t the drama often goes unnoticed by them. The author, who is also a pilot and navigator, writesof the airplane, the sky, the wind, the cloud, the phenomenon of fiy-ing with extreme sensitivity and insight.

This department is prepared by the ARMY AVIATION DIGEST staff.Views expressed are not necessarily those fo the Department of the Army orof The Army Aviation School.- The Editor


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8 ARMY AVIATION DIGESTThe sky is, to my thinking, the open book of knowledge, ofrevelation and the more I live and fly, the more opportunities I

find in the sky-the more lessons and beauty and drama undreamed,he says. In a forceful, impressively descriptive style, the authorweaves this knowledge and drama into an exciting narrative, histori-cally and technically accurate.The history of the loosening of the chains on man's wingsthrough the centuries and an explanation of what we now know formthe basis of Mr. Murchie's book. Technical matters of meteorology

and aerodynamics, while presented in a manner which will serve asa refresher on many facts well known to the aviator, take secondplace to the author's imagination and the poetic sweep of his prose. Only in what may be considered the span of half a lifetime; manhas grown so accustomed to his new wings he tends to forget howmiraculous is each flight. Mr. Murchie describes the myriad of thingswhich compose this miracle so interestingly that your first flight afterreading Song of the Sky will infect you with a sense of adventureperhaps forgotten since early solo days.THE RMYWRITER-Klein David. (The Military Service Pub-lishingCompany, 100 Telegraph Press Bldg., Harrisburg, Pa., 1954.3.00) .

In today's Army a typewriter has been called as essential aweapon as a rifle; a mimeograph machine as important as a tankA badly constructed letter or a training manual which fumbles itsmeaning, or which fails to yield clear and specific communica-tion, has all the potential danger of a badly designed gun or a faultilyconstructed ponton bridge.

In its fourth edition, The Army Writer has become an' acceptedguide for many whose job includes using the typewriter as well asth gun.With wit and discrimination, Mr. Klein outlines how to writecorrectly, easily, and at the same time so accurately that there is littledanger of misinterpretation. Containing many examples of actualArmy writing, the book illustrates in detail the most prevalent ills inmilitary writing and shows how to correct them. The reader will findvaluable hints on how to write and edit a variety of Army publica-tions. The book also contains concise but comprehensive sections onpractical grammar and editorial style.


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Upon returning from an observation mISSIOn flown during afield exercise the pilot of an L-19 established an approach to an airstrip. The strip was 700 feet long and enclosed by trees and wires.

Lieutenant Colonel James W. Hill abDve, is the DirectDrDf InstructiDn fDr the Army AviatiDn SchoDl and is Dne Df the Army s mDst seniDr aviatDrs. He graduated frDm the test grDup fDr ArmypilDt training which was cDnducted in 1942 by the Air TrainingDetachment, Fort Sill, Okla. He was retained as a flight instructDrand later became a flight cDmmander and check pilDt. CDlDnel Hillhas lDgged Dver 4,000 hDurs flight time, is instrument rated, and isqualified in fixed- and rDtary-wing aircraft. During W Drld War I heserved as Air Officer, 1st Inf. Div., in EurDpe. His subsequent assignments included aviatiDn test prDject Dfficer fDr Army Test BDard

N ~ 1 FDrt Bragg, N. C During the KDrean War he served as AirOfficer, 7th Inf. Div., and then was selected as seniDr Army AdvisDrfDr the Japanese NatiDnal Safety Force. He returned to the ArmyAviatiDn SchoDl in 1954 as DirectDr, Department Df RDtary-WingTraining, s.erving in this pDsitiDn until receiving his present assignment in July 1955. The Editor


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30 ARMY AVIATION DIGEST OctoberWeather was CAVU and winds were calm. On his first approach, thepilot decided to make a go-around be'cause he was coming in too fast.

At this point, let us look at the pilot's statement about his secondapproach: I set up a power approach usiQg 45 degrees of flaps. Itouched down within the first third of the strip, bounced slightly, andnoted that my ground speed was high, so I pulled 60 degrees of flapsin order to slow the aircraft down. I touched down again near thecenter of the strip. At this time I thought I had the aircraft on theground and under control, but it floated up again. I continued to pullthe nose up and wait for the payoff.

'During the process of pulling the stick all the way back, I hadallowed my feet to apply pressure on the brakes. (I was wearing bootsand was not accustomed to flying in boots.) I did not realize I hadpressure on the brakes until I completely stalled and touched down.

When the plane touched down, the ground was very soft andthe aircraft skidded, dug in, and the tail came up. I slid forwardunder the safety belt applying even more pressure on the brakepedals. I tried to push myself back, but could not until the aircrafthad nosed up so high that I was unable to get the tail down. The forward motion completely stopped. As the nose dug in the ground, itseemed to pause momentarily then fall over on its back. I then cut offall switches, loosened my safety belt, and climbed out.Investigation revealed that, after tl; e second touch down, whichwas near the halfway point of the strip, the wheels of the aircraftskipped 'over the runway for approximately 200 feet; then the aircraft touched down and slid for 100 feet more. During this slide theprop struck the ground eight times. The aircraft nosed over onto itsback just short of the end of the runway.

Flaps or dive brakes? The flaps on an L-19 are designed toincrease lift. The pilot evidently did not know this or, in the excitement of the moment, failed to consider it. Had he slowly reducedflaps after the second touch down and used brakes sparingly, hemight possibly have landed the aircraft safely, but he still had time,after the second bounce, to make a go-around. When in doubt, do nottake a chance: go around.

The Gray Hair department is prepared by the RMY VI TIONDIGEST staff with information obtained from the files of the world wideaircraft accident safety review board. The views expressed in this depart-ment are not necessarily those of the Department of the rmy or of TheArQty Aviation School. The Editor


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1955 GRAY HAIR 31ard anding

A pilot took off in an H -13 from the home field on a night tactical training mission and flew to an auxiliary field to practice landings He was accompanied by a rated pilot who was to fly the helicopter the second period_ Winds were calm and visibility 10 miles,but at the auxiliary field there was a layer of haze, approximately100 to 150 feet above the ground.The landing area consisted of two flare pots, spaced one behindthe other, approximately 40 feet apart. During the initial approachthe pilot asked the passenger to tum on the landing light. At thispoint the airspeed was 45 mph. The landing light beam was reflectedfrom the haze, and its reflection caused a temporary loss of the pilot'snight vision. The pilot quickly ordered his passenger to tum the lightoff. At the time, he thought that he was approximately 100 feet in theair, but suddenly the helicopter struck the ground. The pilot immediately applied pitch and brought the helicopter u n ~ r control at ahover; then he landed.

Cross tubes of the aircraft's landing gear had to be replaced,and its was necessary to disassemble the rotor head for inspection,check rigging, and make other minor repairs. .The accident report stated that the primary unsafe act was anincorrect approach sight picture by the pilot and that contributingfactors were: Haze layer at 100 to 150 feet above the ground at the

auxiliary field and inadequate proficiency of the pilot in the H-13Gaircraft for night flying. In the report it was recommended that amore adequate night proficiency training program be established forall pilots who have not been flying the same type, model, and seriesaircraft. t was recommended further that a more comprehensivenight flying program be inaugurated at the Army Aviation School sothat pilots joining a unit are qualified to fly all types, models, andseries of aircraft during all phases of operations.The report noted that the pilot had only 54 hours total flyingtime in the H-13 type helicopter and a total of only 15 minutes nighttime in it. The pilot received his tactics training at the Army AviationSchool in the H-23 since the unit to which he was originally assignedwas equipped with them. However, upon completion of his traininghe was reassigned to a unit equipped with H-13's. His total helicopterflying time consisted of 131 hours, 90 of which were obtained duringthe course of training at Gary AFB and the Army Aviation School.


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32 ARMY AVIATION DIGEST OctoberPilot inexperience and the glare of the landing light were cer

tainly contributing factors, but the administrative error of not havinga unit training program for night checkouts of newly graduatedpilots should also have been listed as a contributing error_This accident is best summarized in excerpts from the ArmyAviation Safety Board findings. The board accredited the primarycause of the accident to pilot disorientation at night The pilotbelieved that he was still 100 feet high when he made ground contact. Further, the board stated, Conditions existing which contributed to pilot disorientation were ground haze and slight condensation inside the bubble of the helicopter.The Safety Board continued, This board takes exception to thestatement of the reviewing official that a more comprehensive nightflying program should be inaugurated at the Army Aviation Schoolso that pilots joining a unit are qualified to fly all types, models, andseries of aircraft during all phases of operations. The desirability ofsuch a program certainly cannot be questioned; however, it is impractical at this time.

It is the responsibility of units to determine the proficiency ofpilots in the aircraft in which they are qualified. If, in the-opinion ofsupervisory personnel, the pilot involved in the accident was not completely trained and qualified, this pilot should not have ~ e n permitted to make night flights except when accompanied by an instructor pilot, and until such time as sufficient proficiency had been developed to warrant clearance for solo flight.

Implementation of the recommendation made by the investigation hoard, for the establishment of a more adequate night proficiency training program within the unit, is considered by this boardto be adequate to insure against recurrence of accidents of this typeThe best cure for pilot disorientation at night is experience. t isbelieved that a unit night training course for the pilot involved wouldcorrect all deficiencies in piloting technique revealed by this accident.

L oaded ngineIt is necessary to clear the engine after sustained idling_ Elementary as this statement may be, the following accident indicatesthat pilots still forget to clear their engines.An L-19 pilot was practicing basic maneuvers on a local proficiency flight. Upon completing a power-off stall series, he experi-


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1955 GRAY HAIR 33enced a roughness of the engine on the final recovery. He immediately checked the primer to make sure that it was in the off position,then checked mixture and carburetor heat controls. All controls werefound to be in their proper position. By the time his check was complete the engine had smoothed out.As all seemed to be normal again, ' the pilot continued the pro- 'ficiency flight and decided to practice a simulated forced landing. Heretarded the throttle and established a normal glide. He flew lowenough over his selected field to satisfy himself that he could land init, then applied full power for a climb out. With application ofthrottle the engine began running rough again and continued runningextremely rough at cruising rpm. In an attempt to smooth out theengine, he tried throttling back and found that the engine ran betterat 1700 rpm. But at this rpm he could not maintain altitude. He thenlowered 30 degrees flaps in order to fly slow and hold altitude.

At the time, he was approaching a river and, upon noticing asandbar which appeared to be a suitable forced landing area, decided. to land. As he made a left tum to line up with the sandbar, his leftwing struck a power line which spanned the river, and the pilotstated, I must have instinctively added full throttle at or beforethe time I hit the wires The aircraft rolled over and struck theground in an inverted position, right wing and nose first The pilotemerged from the wreckage unhurt, but the aircraft sustained approximately 6,000 damage.Application of full throttle turned the aircraft over. The situation in which this pilot placed himself .should be brought to the immediate attention of all Army aviators, because slow turns, low to theground, can easily result in similar accidents.

In a slow tu:r;n .any application of aileron to raise the lowerwing increases angle of attack and drag. Inversely, the angle ofattack and drag is reduced in the higher wing. This condition caneasily cause a stall of the lower wing and does result in a tendency ofthe aircraft to roll to the low-wing side. Sudden application of poweraggravates this condition and will cause the aircraft to roll over.Even if recovery is attempted immediately, it would take a pilot atleast 200 feet to recover from this maneuver. Furthermore, theamount of altitude needed for recovery increases as the angle ofbank increases.

In the investigation that followed, an operational check wasmade of the carburetor, fuel pump, and fuel-selector valve. All were


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4 ARMY AVIATION DIGEST Octoberfound to be operating properly. It was the opinion of the accidentinvestigating board, based on evidence at the accident scene, that theengine was turning up full rpm upon contact with the ground.It is hard to believe that a rated pilot did not know how to prevent his engine from loading up, or what to do in the event that it did.An occasional, slow, smooth application of the throttle during theglide in the first simulated forced landing would have prevented thisaccident by assuring that the enginewould not o d up.

PROBLEMS IN HELICOPTER PILOT TRAININGcontinued from page 8)The accident rate of both sections of the experimental classeswas negligible and did not present any particular problems safety

WIse A study was conducted by the Army Aviation School to analyzeresults obtained with the experimental ACHPC classes. It was determined that, in reducing rotary-wing training time, fixed-wing training aids most by developing the attributes of judgment and planning.Further, it was decided that approximately 500 hours fixed-wingtime was needed to develop such attributes. Training time required,plus expense, was considered excessive compared to the advantagesgained.

During the study, the Army Helicopter Aviation Tactics CourseAHATC) was reviewed. In approximately 55 hours less flying

time, graduates of this course meet the same qualifying requirementsin the observation-type helicopter as those being met by graduatesof the ACHPC. The tactics course is helicopter trainsition pilot training for rated Army aviators and consists of 11 weeks training toinclude 90 hours flying time. Rated Army aviators, however, enterhelicopter pilot training with approximately 500 to 4,000 flyinghours.

onclusionHow important is fixed-wing experience to the training of Armyhelicopter pilots? It is a definite advantage, and rotary-wing trainingcan be reduced almost 40 per cent, for pilots who have approximately

500 hours fixed-wing time. However, to give cargo helicopter student


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1955 PROBLEMS I HELICOPTER PILOT TRAINING 35pi10ts 500 hours of fixed-wing training prior to rotary-wing trainingis not practical or economical; thus expense exceeds advantagesgained.

HELICOPTER INSTR U NT PILOT TRAININGcontinued from page 16gational aids and the practical application of helicopter instrumentflying for several years. Information gained from these organizationsconfirmed findings of the Army Aviation School test project.

onclusionsFrom results of helicopter instrument flight research and experimentation conducted by the Department of Rotary Wing Trainingthe Army Aviation School it has been concluded that: Helicopterinstrument flying at airspeeds above 35 knots is both feasible andpractical in the utility-type helicopter. The experienced helicopterpilot can readily adapt himself to helicopter instrument flying. Additional navigational radios are required to supplement radios presently installed in utility helicopters. Utilization of helicopter instrument flight trainers would substantially reduce the amount of hoodtime required and would aid in .maintaining pilot proficiency. .Personnel participating in the test project are firmly convincedthat until instrumentation is developed to fit requirements for safehelicopter instrument flight round-the-clock and marginal weather

operations can be accomplished by pilots trained through a coursesimilar to the recommended training program.

Aerial observation and aVIatIOn had its beginning in theUnited States Army about 100 years ago.From- the basket beneath a balloon purchased by the Unionforces Professor Thaddeus Lowe observed and adjusted artilleryfire against targets in the vicinity of Falls Church Va. on 24 September 1861.


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36 ARMY A IATION DIGESTUR HIGHLIGHTS continued from page 25)

e) Defects due to improperly accomplished installation or maintenance action.f) Discrepancies in technical publications.g) Occurrences involving exposure of personnel toconditions which are harmful to health.h) Unsatisfactory performance, handling characteristics, design, or operational deficiencies.

The examples listed above are guides, not limitations. An unreported uI).satisfactory condition relnains uncorrected and hazardous.An unsatisfactory condition must be carefully considered forits effect on safety-of-flying conditions. Even the remotest possibilitythat the condition will affect safety of flight should be considered asan emergency and transmitted by the most expeditious means.Don't live, or perhaps die, with an unsatisfact ry condition.REPORT IT

This is the first in a series of columns concerning UnsatisfactoryReports received by the Transportation Corps Supply and Mainte-nance Command, 901 Washington Avenue, St. Louis 1, Mo. The col-umn is written by Captain Fred R. Reed, Chief of the TSMC Publi-cations Division. Captain Reed s assignments with the TransportationCorps have included ETO and FECOM tours, nd he served svehicle nd maintenance officer, Hqs, US Army, Alaska, from 1952to 1954. He is a graduate of the Officer Candidate School, The Infan-try School, Fort Benning, Ga., and of the Transportation OfficerCourse and the Aircraft Maintenance Officer Course of the Transpor-tation School, Fort Eustis, Va.


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DISTHIBlJTIOI\ :ACTI\ E AH\lY:OSA (3)COFS,,- (5)N m ~ (;G I. G-2. G :1 (Attn: Army AvnDiv) (5)DEI' LOG (5)TPM ; (5)Tee SVI'. DA (5)Hq. COI\' ARC (25)COXAHC Brls (5)()S :\luj Comd 50)1\G: Slate AG (2)For explanation of ahbreviations u ~ e see SI{ :l20

USAI\: l \O I l fOS Bllsl' COllld (10)ArmiHs (f:ONllS) (I)Armil'S OS) 25)Corps OS) I 0 )Dh OS) 10)B r i ~ (OS) ,5)J< I . ep (C.OI\US) (I)FI C p (CO lllS) '\1/F;USMA 2:HeT (5)50 1.

Lihrarian (l)


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RMY VI TION SCHOOL CRESTWhen reproduced in lull color, the colors red, blue, and yelloware used in the crest to indicate representation of all branches 1the rmy in The rmy Aviation School. The school s aviationtraining mission is symbolized by the perched falcon denotingthe art of falconry with its patient training of swift, keen birdsfor hunting. The mailed fist depicts the military ground armwhich exercises the control, training, and direction of the flight.

Army Aviation Digest - Oct 1955

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Transcript of Army Aviation Digest - Oct 1955