Aerodynamics Class 5 HELICOPTER
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Transcript of Aerodynamics Class 5 HELICOPTER
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AERODYNAMICS REVIEW
This is a basic review ofaerodynamic factors listed in the
Primary Instructor Pilot MOI.
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DYNAMIC ROLLOVER
Dynamic rollover is the occurrence of a
rolling motion; while any part of the landinggear is acting as a pivot, which causes the
aircraft to exceed a critical angle, roll over,
and recovery is impossible.
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DYNAMIC ROLLOVER
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DYNAMIC ROLLOVER
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DYNAMIC ROLLOVER
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SETTLING WITH POWER
Settling with power is a condition of powered flight inwhich the helicopter settles in its own downwash.
Conditions conducive to settling with power are avertical or near-vertical descent of at least 300 feetper minute, low forward speed and using some ofthe available engine power (20-100 percent )withinsufficient power to retard the sink rate.
Normally, increasing airspeed is the preferredmethod of recovery. Usually less altitude is lost bythis method than by the method of loweringcollective. The two methods may be combined ifaltitude permits.
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SETTLING WITH POWER
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SETTLING WITH POWER
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SETTLING WITH POWER
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DISSYMMETRY OF LIFT
In forward flight, the combined effects of the
differential airflow across the advancing and
retreating blades and the three no-lift areas on the
retreating blade result in a dissymmetry of liftpotential between the advancing and retreating
halves of the rotor disk.
Blade flapping alone or in conjunction with cyclicfeathering can eliminate dissymmetry of lift and
allow the pilot to maneuver the helicopter.
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DISSYMMETRY OF LIFT
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DISSYMMETRY OF LIFT
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TRANSLATING TENDENCY
The tendency of the single-rotor helicopter to
move laterally during hovering flight.
It is compensated for by one or more of
the following:
Flight-control rigging.
Transmission tilted slightly to the left.
Collective pitch control system.
Pilot inputs to control drift.
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TRANSLATING TENDENCY
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AIRFLOW DURING A HOVER
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AIRFLOW DURING A HOVER
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AIRFLOW DURING A HOVER
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TRANSVERSE FLOW EFFECT
Because of coning and the forward tilt ofthe rotor system, there is a differential
airflow across the front and rear halves of
the rotor disk.
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TRANSVERSE FLOW EFFECT
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RETREATING BLADE STALL
A stall of the retreating blade that begins at or near the tipbecause of high angles of attack required to compensate fordissymmetry of lift and the three no-lift areas.
Conditions most likely to produce blade stall are:
High blade loading (high gross weight).
Low rotor RPM.
High density altitude.
Steep or abrupt turns.
Turbulent air.
Recover from blade stallReduce power.
Reduce airspeed.
Reduce the severity of the maneuver.
Increase RPM.
Check pedal trim.
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RETREATING BLADE STALL
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RETREATING BLADE STALL
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TOTAL AERODYNAMIC FORCE
As airflow flows around an airfoil, a pressure
differential develops between the upper and lower
surfaces. The differential, combined with the
resistance of the air to the passage of the airfoil,
creates a force on the airfoil. This force, is known
as total aerodynamic force, is represented by a
vector. Total aerodynamic force acts at the center
of pressure on the airfoil and is normally inclinedup and to the rear.
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TOTAL AERODYNAMIC FORCE
Total aerodynamic force may be divided into two
components called lift and drag.
Lift acts on the airfoil in a direction perpendicularto the relative wind.
Drag acts on the airfoil in a direction parallel to the
relative wind and is the force that opposes themotion of the airfoil through the air.
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TOTAL AERODYNAMIC FORCE
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TOTAL AERODYNAMIC FORCE
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AIRFLOW IN FORWARD FLIGHT
Differential velocities around the rotor systems as a result of
forward speed
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AIRFLOW IN FORWARD FLIGHT
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CONCLUSON
This has been a review of the items listed
in the Primary Instructor Pilot MOI. Please
address any questions you have byreviewing Fundamentals Of Flight, FM 1-
203 (dated October 1988) or speaking to
one of the Primary MOI/QC instructors.