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Pilot Flight Training > Theory Of Rotary Wing Flight > Flashcards

Theory Of Rotary Wing Flight Flashcards

1
Q

Define center of pressure.

A

The point along the chord line of an air foil through which all aerodynamic forces are considered to act.

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2
Q

Define airfoil.

A

Any surface designed to produce lift when air passes over it.

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3
Q

List two basic types of airfoils.

A

Symmetrical

Non-symmetrical

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4
Q

Define rotational relative wind as applied to an airfoil.

A

The flow of wind parallel and opposite to the flight path of an airfoil.

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5
Q

Define induced flow.

A

Downward flow of air through the rotor blades.

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6
Q

Define resultant relative wind

A

Rotational relative wind modified by induced flow.

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7
Q

How is angle of incident measured.

A

The angle between the chord line of an airfoil and the plane of rotation.

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8
Q

Define angle of attack

A

The angle between the chord line of an airfoil and the resultant relative wind.

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9
Q

Centrifugal force…

A

The outward force produced whenever a body moves in a curved path

Provides rigidity to the rotor blades

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10
Q

Three adverse effects of coning

A

Loss of disk area

Loss of total lift

Stress on blades

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11
Q

Why is blade twisting necessary?

A

To distribute the lifting forces more evenly along the blade

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12
Q

How is the rotor blade twisted?

A

Higher AOI at the base and decreases towards the end

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13
Q

List the two components of total aerodynamic force.

A

Lift and drag

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14
Q

Describe the relationship of lift to the resultant relative wind.

A

Perpendicular

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15
Q

Describe the relationship between drag and resultant relative wind.

A

Parallel and in the same direction

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16
Q

Which type of drag decreases with an increase of airspeed?

A

Induced Drag

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17
Q

Which type of drag increases with an increase in airspeed.

A

Parasite drag

18
Q

Define dissymmetry of lift

A

Dissymmetry of lift is the differential lift between advancing and retreating halves of the rotor disk caused by the different wind flow velocity across each half

19
Q

What causes the advancing blade to flap up

A

An increase in lift.

20
Q

Define blowback

A

Change in the attitude of the rotor system

21
Q

Which forces in the lift equation can the pilot control

A

Coefficient of lift

Airspeed

22
Q

Define centrifugal force

A

Outward force produced whenever a body moves in a curved path

23
Q

Define rotor blade coning

A

Upward flexing of the rotor blades

24
Q

Rotor blade coning is a compromised between which two forces

A

Lift

Centrifugal force

25
Q

Define gyroscopic precession

A

When a force is applied to a rotating body it will manifest 90 degrees after the application in the direction of rotation

26
Q

Why is blade twisting necessary

A

To distribute the lifting forces more evenly along the blade

27
Q

Define translating tendency

A

Tendency of a single rotor helicopter to drift to the right

28
Q

List 4 methods used to overcome translating tendency in single rotor helicopters.

A

Rigging the cyclic

Tilting the mast

Left cyclic

Automatic flight controls and SAS

29
Q

Describe the relationship of total force to the tip path plane

A

Perpendicular

30
Q

And the rotor disc is tilted what are the two components of total force

A

Lift

Thrust

31
Q

What are the two flight conditions

A

Balanced

Unbalanced

32
Q

List the 4 rotor blade actions

A

Rotation

Flapping

Feathering

Hunting

33
Q

Define effective translational lift

A

When the rotor completely outruns the recirculation of old vortices and begins to work in relatively undisturbed air

34
Q

ETL occurs at what speed

A

16-24

35
Q

Transverse flow effect occurs at what speed

A

10-20

36
Q

Define settling with power

A

When I helicopter settles into its own downwash

37
Q

Where is the three simultaneous conditions required for settling with power

A

Vertical decent speed of at least 300 fpm

20% to 100% of engine power

Slow airspeed less than ETL

38
Q

What is the required recovery procedures for settling with power

A

Increase airspeed with cyclic

Reduce collective (altitude permitting)

Adjust RPM to normal range

39
Q

Define autorotation

A

No engine power is given and main rotor is driven only by the relative wind

40
Q

Describe how to prevent a rotor RPM over speed during auto rotation with turns

A

Collective control

41
Q

Describe the symptoms of her treating blade stall

A

Abnormal vibrations

Pitch up attitude

Left roll

42
Q

Describe the recovery procedure from retreating blade stall

A 
Reduce collective pitch
Regain control
Reduce airspeed
Increase rotor rpm to normal operating range
Minimize maneuvering
Descend to a lower altitude

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