Aerodynamics Class 5 HELICOPTER

7/27/2019 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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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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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 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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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.

Documents

Aerodynamics Class 5 HELICOPTER