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P1 Army Aviation > Theory Of Rotary Wing > Flashcards

Theory Of Rotary Wing Flashcards

1
Q

Define settling with power?

A

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

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2
Q

List the three simultaneous conditions required for settling with power.

A

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

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3
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.

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4
Q

Define 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.

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5
Q

Describe how a pilot prevents a rotor R.P.M. over speed during an autorotation with turn.

A

The pilot must prevent rotor RPM over speed with collective control.

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6
Q

List the three conditions required for dynamic rollover to occur.

A

a. Pivot point
b. Rolling motion
c. Exceed critical angle

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7
Q

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

A

Physical and human

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8
Q

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

A

Smooth, moderate collective reduction

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9
Q

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

A

High forward speed

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10
Q

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

A

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

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11
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, 
minimize maneuvering, 
and descend to a lower altitude.
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12
Q

Listed below examples of Newton’s Laws of Motion. To the right of each example, indicate which law is involved

A

A. Torque effect - Action / Reaction
B. More power is needed to obtain a desired RPM than is need to maintain the RPM - Inertia
C. Greater load, less acceleration
- Acceleration

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13
Q

If the airflow atop the airfoil increases, static pressure will

A

…decrease and dynamic pressure will increase

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14
Q

Define center of pressure

A

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

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15
Q

Define airfoil.

A

..any surface designed to produce lift when air is passed over it

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16
Q

List two basic types of airfoils.

A

A. Symmetrical

B. Non-symmetrical

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17
Q

Six descriptions of airfoil (blade) sections

Match the descriptions to the airfoil terms

A

Chord - Straight line from the leading edge to the trailing edge

Rounded edge - leading edge

Upper curvature - Upper camber

Lower shape - Lower camber

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

Trailing edge - Tapered edge

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18
Q

Define rotational relative wind as applied to an airfoil.

A

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

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19
Q

Descriptions of airfoil movements. Match these movements to the rotational relative wind arrows.

A 
Rotation only
- look for a straight line
Rotation and flapping up
- look for and decline arrow
Rotation and airspeed
- look for a double headed arrow
Rotation and flapping down
- look for a ascending arrow
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20
Q

Define Induced flow.

A

…Downward flow of air through the rotor blades

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21
Q

Define resultant relative wind.

A

…Rotational relative wind modified by induced flow

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22
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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23
Q

Define angle of attack?

A

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

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24
Q

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

A

…the cyclic pitch control

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25
Q

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

A

…dynamic pressure increases, static pressure decreases

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26
Q

List the two components of total aerodynamic force.

A

Lift and drag

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27
Q

Describe the relationship of lift to resultant relative wind.

A

Perpendicular

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28
Q

Describe the 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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29
Q

Listed below are descriptions of various types of drag. To the right of each description, indicate whether the drag is induced, parasitic, or profile.

a. Rotor-tip vortices-
b. Lift and total aerodynamic force tilting rearward on the airfoil -
c. Skin friction on the fuselage -
d. Skin friction on the airfoil -
e. Non-streamlined fuselage -

A

a. Rotor-tip vortices- induced
b. Lift and total aerodynamic force tilting rearward on the airfoil - induced
c. Skin friction on the fuselage - parasitic
d. Skin friction on the airfoil - profile
e. Non-streamlined fuselage - parasitic

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30
Q

Which type of drag decreases with an increase in airspeed?

A

Induced drag

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31
Q

Which type of drag increases with an increase in airspeed?

A

Parasite drag

32
Q

Define dissymmetry of lift.

A

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

33
Q

Relative wind velocity on the advancing blade equals blade speed

A

Plus

34
Q

Relative wind velocity on the retreating blade equals blade speed

A

Minus

35
Q

What causes the advancing blade to flap up?

A

An increase of lift

36
Q

What causes the retreating blade to flap down?

A

A decrease in lift

37
Q

How does the helicopter compensate for dissymmetry of lift?

A

Flapping

38
Q

How does the pilot control dissymmetry of lift?

A

Cyclic feathering

39
Q

Define blowback.

A

Change in altitude of the rotor system

40
Q

How does the pilot correct for blowback?

A

Cyclic feathering

41
Q

Which forces in the lift equation can the pilot control?

A

Coefficient lift and airspeed

42
Q

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

A

Pressure, temperature and humidity

43
Q

A semi-rigid disk tilts relative to the…

A

Mast

44
Q

An articulated disk tilts relative to the…

A

Hub

45
Q

Define centrifugal force

A

Outward flexing of the rotor blades.

46
Q

Define rotor blade coning.

A

Upward flexing of the rotor blade

47
Q

Rotor blade Koning is a compromise between which two forces?

A

Lift and centrifugal force.

48
Q

Define gyroscopic procession.

A

When force is applied to a rotating body, it will manifest 90 degrees after application.

49
Q

Why is blade twisting necessary?

A

To distribute the lifting force more evenly along the blade

50
Q

A pedal turn to the right requires_______( less) power than a pedal turn to the left.

A

Less

51
Q

Define translating tendency.

A

…translating tendency is the tendency of a single rotor helicopter to drift right while hovering.

52
Q

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

A

a. Rigging the cyclic
b. Tilting the mast
c. Left cyclic
d. Automatic flight-control/stabilization augmentation system

53
Q
  1. List the four rotor blade actions.
A

Rotation
Flapping
Feathering
Hunting

54
Q

Describe the relationship of total force to the tip path plane?

A

Perpendicular

55
Q

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

A

Lift and

thrust

56
Q

What are the two flight conditions?

A

Balanced and

unbalanced

57
Q

At what altitude would the aircraft be in ground effect?

A

Less than one rotor diameter

58
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. Tall grass and uneven terrain
d. Hovering over water
e. Beginning of translational movement
f. Hovering into a wind

59
Q

Define effective translational lift

A

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

60
Q

Effective translational lift occurs at an airspeed of

A

Approximately 16-24 KTS

61
Q

Transverse flow effect is noticeable at an airspeed of

A

10-20 KT

62
Q

Label the components of the Basic Aerodynamic Model.

A
  1. Tip path plane/plane of rotation
  2. Chord line
  3. Axis of rotation
  4. Rotational Relative Wind
  5. induced flow
  6. Angle of attack
  7. Resultant Relative Wind
  8. Angle of Incidence
  9. Lift
  10. Drag
  11. TAF (Resultant Force)
63
Q

METAR is done how often

A

Routine hourly report

64
Q

METAR contains

A 
Type of report
Station identifier
Date and time of observation 
Winds
Visibility 
Precipitation and obscurations
Sky condition
Temperature and dew point
Altimeter setting and remarks
65
Q

Observation station are showed in four-letter identification system

A

i.e. KOZR- Cairns AAF

66
Q

Two factors must be considered when converting Zulu / Local time.

A

Must know time zone you are located in. Ref. FIH E-4
Daylight savings time begins second Sunday in March.
Standard time begins on first Sunday in November.

67
Q

AUTO in METAR means

A

In automated observation. Most military sites in many civilian sites are automated.

In A02A would indicate that the observer has augmented the observation.

68
Q

Wind direction is in reference to

A

True north and is reported to the nearest 10°.

69
Q

Wind speed is reported…

A

two minute average reported to the nearest knot

70
Q

Calm wind

A

00000KT

71
Q

Gust - fluctuations

A

Gust fluctuations in wind speed of 10 KTS or more between peaks in LULLS

72
Q

VRB

A

Variable is used when direction is variable and speed is

73
Q

V is used when

A

Wind varies 60° or more and the wind is > 6 knots

74
Q

When is Peak wind reported

A

Peak wind is reported in remarks when instantaneous speed is over > 25 KTS

75
Q

Visibility

A

The greatest horizontal distance specified objects can be seen and identified. Reported in miles in fractions of miles.

76
Q

Prevailing visibility

A

The greatest horizontal distance that specified objects can be seen over at least one half (1/2) of the horizontal, not necessarily continuous.

77
Q

Prevailing visibility

A

3/4 SM
1 1/2 SM
7/8 SM
1/2 SM

P1 Army Aviation (1 decks)

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