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CAA Module 11 > Module 11.1 Theory of flight > Flashcards

Module 11.1 Theory of flight Flashcards

1
Q

What are the 3 primary axes in flight?

A
  • Longitudinal
  • Lateral
  • Vertical
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2
Q

What are the 3 movements about the axes?

A
  • Roll
  • Pitch
  • Yaw
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3
Q

What movement is about the vertical axis?

A

Yaw

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4
Q

What movement is about the lateral axis?

A

Pitch

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5
Q

What are the primary flight controls?

A
  • Rudder
  • Aileron
  • Elevator
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6
Q

What happens when the aileron deflects upwards?

A

Decrease in lift

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7
Q

What is the equation for dynamic energy?

A

= 1/2 x Density x Velocity Squared

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8
Q

What occurs to the outboard aileron at high speeds?

A

Locked

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9
Q

What aileron is used at high speeds?

A

Inboard aileron

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10
Q

What is the purpose of roll/flight spoilers on an up-going aileron of a rolling aircraft?

A

Supplement aileron control by reducing lift

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11
Q

What is the differential operation of flight spoilers linked to?

A

Aileron control system

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12
Q

Roll spoilers have two purposes what are they?

A
  • Execute accurate turn
  • Reduce need for large aileron deflection at high speeds
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13
Q

Why is the elevator at the position furthest away from the C of G?

A

Greater leverage

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14
Q

What are stabilators?

A

Dual purpose control surface

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15
Q

Where are stabilators used?

A

High speed military aircraft

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16
Q

When a shockwave forms on the hinge line of an elevator the control surface is ineffective what is the solution to this?

A

Stabilators

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17
Q

THS is also known as what?

A

Variable incidence stabilisers

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18
Q

THS are only used for what purpose?

A

Pitch trimming

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19
Q

What is the advantage of the THS?

A

Reduced drag due to reduced requirement for elevator deflection

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20
Q

What does the trim angle account for?

A
  • Weight distribution
  • Fuel consumption
  • Flap and engine settings
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21
Q

Which way is the trim wheel movement for nose down?

A

Spin wheels forward

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22
Q

What are Canards?

A

Flight control system forward of the wings

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23
Q

How Canard config influence the flight control system?

A
  • Lift and trim
  • Pitch control
  • Stability
  • Stall prevention
  • High A of A manouvuers
  • Control redundancy
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24
Q

What is the purpose of a rudder limiter?

A

Limits rudder movement at high speeds

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25
Q

What is side slip?

A

Yaw in the direction of the roll movement

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26
Q

Elevons are a combination of what controls?

A

Elevators and ailerons

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27
Q

Ruddervators are a combination of what controls?

A

Rudder and elevator

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28
Q

What is adverse yaw?

A

Yaw in the opposite direction to roll

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29
Q

How is adverse yaw prevented?

A
  • Aileron differential
  • Frise aileron
  • Spoilers
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30
Q

Frise ailerons increase drag how?

A

Has a leading edge that protrudes into airflow

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31
Q

What direction is roll in adverse roll?

A

Opposite to yaw

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32
Q

What do slots do?

A

Do not increase lift but they energise the boundary layer to delay separation

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33
Q

What is the disadvantage of slots?

A

Fair amount of drag

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34
Q

What is the main difference of slots and slats?

A

Slats are moveable

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35
Q

What does a slat produce?

A

Lift due to camber increase

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36
Q

Flap extension has what effect on the nose?

A

Pitch it down

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37
Q

Which flaps produce the least lift increase?

A

Plain flaps

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38
Q

What are the leading edge droops designed to improve?

A

Improve airflow over wings at high A of A

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39
Q

What do Kruger flaps result in when extended?

A

Blunt leading edge leading to better lower speed handling

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40
Q

Where may leading edge flaps be found?

A

Large aircraft at wing root

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41
Q

What are flaperons?

A

Aileron that can also act as a flap

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42
Q

When would a flaperon be used?

A

Take-off/landing

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43
Q

What are the 3 types of spoilers?

A
  • Flight
  • Ground
  • Roll
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44
Q

When would flight spoilers be used?

A

Too slow the aircraft inflight, max deflection is not used.
- Only a few spoilers used not all

45
Q

When would ground spoilers be used?

A

Rejected take off or landing

46
Q

What happens when roll spoilers are deployed?

A

Only a few spoilers deployed on the wing of the direction you want to turn in

47
Q

When can speed brakes be used?

A
  • Final approach to touchdown
  • Landing
48
Q

What do speed brakes not have an affect on?

A

Lift

49
Q

What affect does span wise flow have on the boundary layer?

A

Makes it thicker and at the wing tip

50
Q

What is the danger of swept back wings?

A

Tip stalls first

51
Q

What do wing fences do?

A

Delay onset of boundary layer separation at wing tip

52
Q

What does a saw tooth leading edge do?

A

Creates a small vortex that limits boundary layer outflow and redirects span wise flow

53
Q

Where are vortex generators placed?

A

Trailing edge of the wing

54
Q

How and why are they installed like this? (Vortex generators)

A

They are installed opposite so that the vortices mix

55
Q

Where would a stall strip be installed?

A

Leading edge at wing root

56
Q

What do stall strips encourage?

A

Encourage the root to stall before the wing tip

57
Q

Where would a trim tab be found?

A

Trailing edge of primary control surface

58
Q

Besides anti-balance what direction are the trim tabs moved?

A

opposite to the control surface

59
Q

What is the purpose of the trim tabs?

A

Reduce the load for the pilots by making it easier to move the control surface

60
Q

A trimmed aircraft has what?

A

0 aerodynamic moments

61
Q

What is the disadvantage of a balance trim tab?

A

Reduces efficiency of the control surface

62
Q

How does a pilot operate the control surface with a servo tab?

A

By moving the tab not the control surface

63
Q

What is a spring tab?

A

A spring tab is like a servo tab however it only moves at a certain load
- High speed only

64
Q

When would an anti balance tab be used?

A

Used when input off control is too sensitive and needs some resistance

65
Q

What is a disadvantage of anti balance tabs?

A

More effort to deflect

66
Q

When does mass balance flutter occur?

A

C of G of control surface aft of hinge line

67
Q

What is control surface bias?

A

Control surfaces set at a slight angle from neutral to create a continuous aerodynamic force to offset forces during flight

68
Q

What is a horn balance?

A

A weight placed forward of the hinge line on a control surface

69
Q

What is an insert hinge?

A

An insert hinge is where the hinge line is moved back

70
Q

How does a balance panel work?

A

Creates a chamber of higher and lower pressure and uses this to help move the control surface

71
Q

What is the equation for mach number?

A

Velocity/Speed of sound

72
Q

What are the 3 speed ranges?

A
  • Subsonic <0.8 mach
  • Transonic 0.8 to 1.2 mach
  • Supersonic >1.2 mach
73
Q

Is the local airspeed of airflow over the wing greater or less than true speed?

A

Greater than

74
Q

What range can local airflow be in if true speed is in transonic?

A

Supersonic

75
Q

Is air incompressible or compressible at supersonic?

A

Compressible

76
Q

Describe the pressure waves of transonic?

A

Piled up

77
Q

Describe the pressure waves of Subsonic?

A

Equally spaced

78
Q

Describe the pressure waves of Supersonic?

A

Intersecting

79
Q

What is the critical mach number?

A

The min true speed that will result in local air speed being the speed of sound

80
Q

Air is considered compressible at what speeds?

A

Mach 0.4 and above

81
Q

What problems occur when a shock wave is formed?

A
  • Reduce lift
  • Increase in drag
  • Buffeting
  • Control problems
  • Uncommanded changes in trim and stability
82
Q

Normal shockwaves occur at what angles to the airflow?

A

90 degrees

83
Q

What direction do shockwaves move if the speed is increased?

A

Aft towards trailing edge

84
Q

What happens when supersonic airflow passes through a shockwave?

A
  • Velocity decrease
  • Density and pressure increase
  • Temperature increase
85
Q

What angles do oblique shockwaves occur to the airflow?

A

Not 90

86
Q

What happens to the airflow speed when passing through an oblique shockwave?

A

Slightly reduced

87
Q

When is an expansion wave formed?

A

When a supersonic airflow changes direction around a curve or corner

88
Q

What occurs to the airflow of an expansion wave?

A
  • Increase in velocity
  • Decrease in pressure, density and temp
89
Q

What does the wave profile on a flat plate profile look like?

A

Positive AoA

Leading edge:
- Underside oblique wave
- Top expansion wave

Trailing edge:
- Underside expansion wave
- Top oblique wave

90
Q

As the speed increases, where does a shockwave occur?

A

Underside of the wing

91
Q

What occurs to the flow after the shockwave?

A

Turbulent flow

92
Q

What are the two supersonic wing profiles

A
  • Double wedge
  • Circular arc
93
Q

Where is centre of pressure located on a wing if the airflow is supersonic?

A

50% aft of Chord line

94
Q

Where is centre of pressure located on a wing if the airflow is subsonic?

A

25% aft of chord line

95
Q

What can be said about the expansion wave on a circular arc profile?

A

Continuous

96
Q

What is the benefit of vortex generators?

A

They create a small oblique shock wave when airflow is supersonic, this reduces the normal shock. This means less flow separation and reduced wave drag

97
Q

What is the body type with the lowest theoretical wave drag?

A

Sears-Haack body

98
Q

To ensure volume distribution, what can be done to the fuselage at the wing attachment position?

A

Narrowed/ waisted fuselage

99
Q

What is aerodynamic heating caused by?

A

Friction from the air

100
Q

What can be done to supersonic aircraft to eliminate aluminiums strength problem at high temperature?

A

Use of titanium alloys

101
Q

How does a normal shock diffuser inlet slow air to subsonic speeds?

A

Normal shock wave

102
Q

What speed is a normal shock diffuser suitable for?

A

Low supersonic

103
Q

In a single/ multiple oblique shock inlet, oblique shock waves reduce what?

A

The strength of the normal shockwave

104
Q

How does a variable supersonic inlet work?

A

Actuators move a panel to change the size of the inlet. This affects the normal shock and at high speeds moves further to create oblique shockwaves to reduce the normal shock strength

105
Q

What happens in a divergent intake of a subsonic engine?

A
  • Velocity decrease
  • Pressure and density increases
106
Q

When a wing is swept back what can be said for the thickness?

A

Reduced profile thickness

Profile thickness = Actual thickness/ chord length

107
Q

What is the most common angle for swept wings?

A

30 degrees

108
Q

What do swept wings reduce?

A
  • Critical mach no.
  • Profile drag
  • Improved stability laterally
  • Overall frontal area
109
Q

What is the drawback of sweptback wings?

A
  • Tip stalls first
  • Increased span wise flow

CAA Module 11 (22 decks)

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