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Aviation > Aerodynamics - Hangar flashcards > Flashcards

Aerodynamics - Hangar flashcards

1
Q

Identify drag as induced, parasitic, or profile:

  • Rotor tip vortexes
  • Lift and total aerodynamic force tilting rearward on the airfoil
  • Skin friction on the fuselage
  • Skin friction on the airfoil
  • Nonstreamlined fuselage
A
  • Rotor tip vortexes - INDUCED
  • Lift and total aerodynamic force tilting rearward on the airfoil - INDUCED
  • Skin friction on the fuselage - PARASITIC
  • Skin friction on the airfoil - PROFILE
  • Nonstreamlined fuselage - PARASITIC
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2
Q

List the 3 factors that determine Air Density.

A

Temperature

Pressure

Humidity

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3
Q

What relative combination of pressure, temperature, and humidity would produce the greatest lift about an airfoil?

A

High Pressure

Low Temp

Low Humidity

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4
Q

What is the definition of Centripetal Force?

A

An inward force directed at the center of rotation.

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5
Q

What is the definition of Centrifugal Force?

A

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

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6
Q

What force provides rigidity to the Rotor Blades?

A

Centrifugal

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7
Q

What are 3 causes of Rotor Blade Coning?

A

Low Rotor RPM

High Gross Weight

High “G” Maneuvers

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8
Q

What are the effects of Blade Coning?

A

Loss of disc area and lift

Stress on blades

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9
Q

How is the Angle of Incidence measured in a rotary-wing aircraft?

A

Between the chord line

and the plane of rotation.

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10
Q

Which control will vary (constant change) the angle of incidence of a rotor blade?

A

cyclic pitch control

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11
Q

What is the definition of Angle of Attack?

A

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

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12
Q

What are two possible effects when the blades are out of track?

A

Low-frequency vertical vibrations

Increased instability

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13
Q

Why does the helicopter act as a pendulum?

A

The center of gravity is located below the supporting elements.

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14
Q

With rotor systems which rotates counterclockwise, what is the direction in which the fuselage tends to yaw?

A

Right/Clockwise

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15
Q

How is torque effect overcome in the following helicopters?

  • Single Rotor
  • Tandem Rotor
A

Single rotor - Tail rotor

Tandem rotor - Opposite rotating main rotors

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16
Q

Does a pedal turn to the right require more or less power than a pedal turn to the left?

A

Less

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17
Q

What are the 3 Methods used to Overcome Translating Tendency in single rotor helicopters?

A

Rigging of the cyclic

Left cyclic

Tilting the mast

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18
Q

What type of vibration (high or low frequency) is associated with the tail rotor malfunctions?

A

High frequency

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19
Q

What is the yaw tendency of a helicopter which has experienced complete loss of tail rotor thrust?

A

Yaw right

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20
Q

What is the definition of Collective Feathering?

A

Pitch changes are equal and simultaneously to all blades.

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21
Q

What is the Relationship of Total Force of the Rotor System to the Tip-Path Plane?

A

Perpendicular

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22
Q

List the 2 components of total force which result when the tip-path plane is tilted. What is the purpose of each component?

A

Lift - opposes weight and acts vertically

Thrust - opposes drag and acts horizontally (Lift + Thrust = Total Force)

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23
Q

List 4 conditions that would promote “Ground effect”?

A
  1. Altitude 1 1/4 rotor diameter or less
  2. No wind
  3. Smooth terrain
  4. Open surfaces
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24
Q

List 5 conditions that would result in the Loss or apparent loss of ground effect?

A
  1. Beginning of translational movement
  2. Altitude greater than 1-1/4 rotor diameter
  3. Hovering into a wind
  4. Confined areas
  5. Uneven terrain or tall grass
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25
Q

What is the definition of settling with power?

A

Settling with Power - is a condition of powered flight in which the helicopter settles in it’s own downwash.

This is also known as Vortex Ring State.

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26
Q

What causes Settling with Power?

A

Opposing airflow hampers the rotor’s induced airflow (air coming down through the rotor system), causing a cancellation of the induced airflow. End Result is Less Lift.

27
Q

What are the Symptoms of Settling with power?

A

High rate of descent High power consumption Loss of collective pitch effectiveness Vibrations

28
Q

What are the conditions conducive to Settling with Power?

A
  1. At least a 300 ft per minute rate of descent.
  2. High power (20 to 100% applied) with insufficient power to stop descent.
  3. Low airspeed (less than ETL)
29
Q

How do you recover from Settling with Power?

A
    • If power is available: increase collective normally.
    • If insufficient power, then:
      a) Increase airspeed.
      b) reduced collective
30
Q

What are some flight conditions that would allow Settling with Power to take place during your flight?

A
  1. Downwind Approach
  2. Steep Approach > 30 degrees
  3. Formation Landings
  4. NOE
  5. Hovering OGE
  6. Masking (tactically OGE hiding)
31
Q

You are flying straight and level at 1500 feet and 90 knots. You desire to reduce airspeed to 60 knots while maintaining altitude, RPM, and heading. What control movements are necessary?

A

Cyclic to the rear, lower collective, and apply right pedal

32
Q

What are the 2 purposes of Cyclic Pitch Control?

A
  1. Tilt the tip-path plane
  2. Control dissymmetry of lift
33
Q

What is the method used by pilots to control Dissymmetry of Lift?

A

Cyclic pitch control

34
Q

In an articulated rotor system, assume that a blade flaps up; in which direction will the blade’s center of gravity move? Will the blade then lead or lag?

A

Inboard

Lead

35
Q

List 5 factors that would contribute to Ground Resonance?

A
  1. Bad oleo struts
  2. Bad drag dampers
  3. Taxing over uneven ground
  4. Hesitant touchdown
  5. Hard one-skid or wheel landing
36
Q

List 2 corrective procedures in the event of Ground Resonance?

A
  1. If operating RPM exist, get airborne.
  2. If operating RPM does not exist, place firmly on ground, reduce throttle, and go through the normal shutdown procedures.
37
Q

What are the causes of Retreating Blade Stall?

A

Remember: (S-T-A-A-L-L)

S - Steep Turns

T - Turbulent Air

A - Altitude - High DA

A - Airspeed - High Airspeed

L - Low rotor RPM

L - Loads - High Gross Weight

38
Q

What is the correction for all stalls?

A

Reduce the angle of attack to a value less than the critical angle

39
Q

List 3 Symptoms of a Retreating Blade Stall?

A
  1. Vibrations and shuddering
  2. Pitch-up tendency
  3. Left-roll tendency
40
Q

What are the corrective actions for Retreating Blade Stall?

A
  1. Reduce power
  2. Reduce airspeed
  3. Reduce the severity of the maneuver
  4. Increase RPM
  5. Check Trim
41
Q

The conditions which constitute straight-and-level flight are constant __________, __________, and __________.

A

Attitude - airspeed (cyclic)

Altitude - collective is primary power control

Direction - heading with cyclic and trim with pedals

42
Q

What is the definition of Dynamic Rollover?

A

The occurrence of a lateral motion, while any part of the landing gear is acting as a pivot point, and the aircraft exceeds it’s critical angle beyond which recovery is impossible.

43
Q

What components contribute to Dynamic Rollover?

A
  1. Pivot Point
  2. Rolling Motion
  3. Aircraft exceeds the critical rollover angle
44
Q

What are the Slope Abort Criteria?

A

Remember: (C-A-M-P-S)

C - Cyclic Stop Limit

A - Aircraft Slope Limits

M - Mast Bumping (not possible / fully articulated)

P - Personal Limits

S - Sliding

45
Q

If on the verge of Dynamic Rollover, what are your actions?

A

Decrease Collective

46
Q

What is the Definition of Dissymmetry of Lift?

A

A normal condition resulting from the advancing blade having a higher relative wind velocity than the retreating blade which creates more lift on the advancing side.

47
Q

Dissymmetry of Lift Is compensated for by what?

A

Blade Flapping (the up and down aerodynamic movement of the rotor blade as it normally rotates)

Cyclic Feathering (mechanical input through the pitch-pull tubes into the rotor system).

48
Q

What is the definition of translating tendency?

A

During hovering flight, the single-rotor helicopter tends to drift laterally to the right.

49
Q

What causes Translating Tendency?

A

This tendency results from the thrust exerted to the right by the tail rotor (to compensate for the main rotor torque).

50
Q

Translating Tendency is compensated for by what?

A
  1. The pilot. The pilot applies LEFT cyclic during a hover.
  2. a built in left cyclic “rigging”.
  3. TILTING of the main transmission to the left
51
Q

What is the definition of Retreating Blade Stall?

A

A phenomenon resulting from the retreating blade not producing enough life due to slow relative wind.

52
Q

What is the definition of Rotor Droop?

A

Rotor Droop is defined as the decrease in Rotor RPM that exists between the time a demand for power is made and the time the power is delivered.

53
Q

What is the definition of Loss of tail rotor effectiveness?

A

A rapid and uncommanded right yaw which does not subside on its own accord and which, if not quickly reacted to, can result in loss of aircraft control.

54
Q

What are the contributing factors to LTE?

A
  1. High Gross Weight
  2. High DA
  3. Low airspeed
  4. RPM R Droop
55
Q

What is Newton’s First Law?

A

Inertia A body at rest tends to stay at rest, a body in motion tends to stay in motion until acted upon.

56
Q

What is Newton’s Second Law?

A

Acceleration - A change in velocity with respect to time.

57
Q

What is Newton’s Third Law?

A

Action/Reaction - For every action, there is an equal and opposite reaction.

58
Q

What are 2 basic types of Airfoils?

A

Symmetrical

Asymmetrical

59
Q

Define rotational relative wind as applied to an airfoil.

A

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

60
Q

What is the definition of an Airfoil?

A

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

61
Q

What is the stalling angle of attack on most airfoils?

A

15 to 20 degrees

62
Q

What is the relationship between Lift and Resultant Relative Wind?

A

Lift is perpendicular to resultant relative wind.

63
Q

What is the relationship between Drag and resultant relative wind?

A

Drag is parallel and in the same direction as resultant relative wind.

64
Q

Write the lift equation.

A

L = CI PxV2/2 x A

Lift = coefficient x (density x velocity squared) / two x wing area

Aviation (13 decks)

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