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URS classes > Theory Of Rotary Wing Flight > Flashcards

Theory Of Rotary Wing Flight Flashcards

1
Q

Newton’s Laws of Motion(which law is involved)

Torque Effect

A

action/reaction

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2
Q

Newton’s Laws of Motion(which law is involved)

More power is needed to obtain a desired RPM than is needed to maintain the RPM

A

Inertia

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3
Q

Newton’s Laws of Motion(which law is involved)

Greater load, less acceleration

A

Acceleration

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4
Q

If the airflow atop the airfoil increases, static pressure will

A

decrease

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5
Q

If the airflow atop the airfoil increases, dynamic pressure will

A

increase

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6
Q

Center of Pressure

A

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

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7
Q

Airfoil

A

Any surface designed to produce lift when air is passed over it

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8
Q

Basic types of airfoils

A

Symmetrical

Unsymmetrical or Nonsymmetrical

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9
Q

Airfoil terms

A 
Chord
Upper camber
Lower camber
Span
Trailing edge
Leading edge
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10
Q

Chord

A

Straight line from the leading edge to the trailing edge

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11
Q

Upper camber

A

Upper curvature

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12
Q

Lower camber

A

Lower shape

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13
Q

Span

A

The length of the rotor blade from the point of rotation to the tip of the blade

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14
Q

Trailing edge

A

Tapered edge

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15
Q

Leading edge

A

Rounded edge

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16
Q

Rotational relative wind (as applied to an airfoil)

A

That flow of air parallel and path of an opposite to the flight path of an airfoil

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17
Q

Induced flow

A

Downward flow of air through the rotor blades

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18
Q

Resultant relative wind

A

Rotational relative wind modified by induced flow

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19
Q

How is the angle of incidence measured in a rotary-wing aircraft?

A

The angle between the chord of an airfoil and the plane of rotation (tip path plane)

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20
Q

Angle of attack

A

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

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21
Q

Which flight control changes the angle of incidence differentially around the rotor system?

A

Cyclic pitch control

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22
Q

With an increase in the speed of air over a surface, what happens to dynamic and static pressure?

A

Dynamic pressure increases, static pressure decreases

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23
Q

Components of total aerodynamic force

A

Lift and drag

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24
Q

Describe the relationship of lift to resultant relative wind

A

Perpendicular

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25
Q

Relationship between drag and resultant relative wind

A

Drag is parallel to and in the same direction of the resultant relative wind

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26
Q

Rotor-tip vortices

A

induced

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27
Q

Lift and total aerodynamic force tilting rearward on the airfoil

A

induced

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28
Q

Skin friction on the fuselage

A

parasitic

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29
Q

Skin friction on the airfoiil

A

profile

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30
Q

Non-streamlined fuselage

A

parasitic

31
Q

Which type of drag decreases with an increase in airspeed?

A

Induced

32
Q

Which type of drag increases with an increase in airspeed?

A

parasite

33
Q

Dissymmetry of lift

A

Differential (unequal) lift between advancing and retreating halves of the rotor disk

34
Q

Relative wind velocity on the advancing blade equals blade speed…

A

plus airspeed

35
Q

Relative wind velocity on the retreating blade equals blade speed…

A

minus airspeed

36
Q

What causes the advancing blade to flap up

A

An increase in lift

37
Q

What causes the retreating blade to flap down

A

A decrease in lift

38
Q

How does the helicopter compensate for dissymmetry of lift?

A

flapping

39
Q

How does the pilot control dissymetry of lift?

A

cyclic feathering

40
Q

Blowback

A

Change in the attitude of the rotor system

41
Q

How does the pilot correct for blowback?

A

cyclic feathering

42
Q

Which forces in the lift equation can the pilot control?

A

Coefficient of lift and airspeed

43
Q

What are the three factors in air density (1/2 rho) that will affect lift?

A

pressure, temperature, and humidity

44
Q

A semi-rigid disk tilts relative to the

A

mast

45
Q

An articulated disk tilts relative to the

A

hub

46
Q

Centrifugal force

A

Outward force produced whenever a body moves in a curved path

47
Q

Rotor blade coning

A

Upward flexing of the rotor blades

48
Q

Rotor blade coning is a compromise between which two forces

A

lift and centrifugal force

49
Q

gyroscopic precession

A

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

50
Q

Why is blade twisting necessary?

A

to distribute the lifting force more evenly along the blade

51
Q

A pedal turn to the right requires ____(more/less) power than a pedal turn to the left

A

less

52
Q

Translating tendency

A

Tendency of a single rotor helicopter to drift right while hovering

53
Q

List four methods used to overcome translating tendency in single rotor helicopters

A

rigging the cyclic
tilting the mast
left cyclic

54
Q

List the four rotor blade actions

A

rotation
flapping
feathering
hunting

55
Q

Describe the relationship of total force to the tip path plane

A

Perpendicular

56
Q

When the rotor disk is tilted, what are the two components of total force

A

Lift and thrust

57
Q

What are the two flight conditions

A

Balanced and unbalanced

58
Q

At what altitude would the aircraft be in ground effects

A

One rotor disc diameter measured from the rotor disc to the surface

59
Q

Loss, or apparent loss, of ground effect is caused by?

A

a. An altitude greater than one rotor diameter
b. Trees and bushes
c. Tail grass and uneven terrain
d. Hovering over water
e. Beginning of translational movement
f. Hovering into a wind

60
Q

Translational lift

A

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

61
Q

Effective translational lift occurs at an airspeed of

A

Approximately 16-24 KTS

62
Q

Transverse flow effect is noticeable at an airspeed

A

10-20 KT

63
Q

Settling with power

A

A condition of powered flight in which the helicopter settles in its own downwash

64
Q

List three simultaneous conditions required for settling with power

A

Vertical or near vertical descent of at least 300 FPM
20% to 100% engine power
Slow airspeed less than ETL

65
Q

List the required recovery procedures for settling with power

A

Increase airspeed with cyclic
Reduce collective as altitude permits
Adjust rotor RPM to normal operating range

66
Q

Autorotation

A

The flight condition during which no engine power is supplied and the main rotor is driven only by the action of the relative wind

67
Q

Describe how a pilot prevents a rotor RPM over speed during an autorotation with turn

A

The pilot must prevent rotor RPM over speed with collective control

68
Q

List the three conditions required for dynamic rollover to occur

A

Pivot point
Rolling motion
Exceed critical angle

69
Q

Dynamic rollover occurs due to a combination of which two factors?

A

Physical and human

70
Q

Which control input is required to recover from dynamic rollover on level ground?

A

Smooth, moderate collective reduction

71
Q

Operating at what speed is most likely to produce retreating blade stall

A

High forward speed

72
Q

Describe the symptoms of retreating blade stall in a single rotor helicopter

A

Abnormal vibration, pitch-up of the nose, and left roll

73
Q

Describe the recovery procedure from retreating blade stall

A

Reduce collective pitch, regain control of the aircraft, reduce airspeed, increase rotor RPM to normal operation range, minimizing maneuvering, and descend to a lower altitude

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