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M11 > 11.1 Theory Of Flight > Flashcards

11.1 Theory Of Flight Flashcards

1
Q

What aircraft axes are there and what motions do each take? (3)

A

Lateral = pitch
longitudinal = roll,
vertical = yaw

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2
Q

What primary flight controls are there? [3]

A
  • Ailerons
  • elevators
  • rudder
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3
Q

What is the definition of primary flight controls?

A

Required to safely control the aircraft during flight

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4
Q

What is the purpose of secondary flight controls?

A

Intended to improve aircraft performance characteristics or to relieve excessive control loading

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5
Q

What devices can be used as secondary flight controls?[4]

A
  • Slats
  • Flaps
  • flight spoilers
  • trims systems
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6
Q

What motion do ailerons control and around what axis?

A

Roll about the longitudinal axis

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7
Q

What supplement the ailerons?

A

Roll spoilers

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8
Q

On which wing will the aileron deflect downwards?

A

The up-going wing

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9
Q

When will the outboard ailerons be locked out during flight? Why?

A

During high speed flight, less deflection required to provide motion

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10
Q

What motion do elevators control and around what axis?

A

Pitch, lateral axis

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11
Q

Which way will the aircraft point if the elevators are deflected downwards?

A

Downward

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12
Q

What is a stabilator?

A

Sometimes referred to as an all moving tail, fully moveable horizontal stabiliser

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13
Q

What 2 types of canards are there?

A

Lifting canard and control canard

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14
Q

Which canard generates an upload or positive lift that opposite to a conventional Horizontal stabiliser?

A

Lifting canard

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15
Q

Which canard is primarily used for pitch control during manoeuvring?

A

Control canard

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16
Q

At what angle of attack is a control canard usually at?

A

Zero

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17
Q

What motion does the rudder provide and on what axis?

A

Yaw and vertical axis

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18
Q

At what speed does the rudder have minimum travel?

A

Above 200 knots

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19
Q

What prevents rudder/stabiliser overload during high speed?

A

Rudder limiter system

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20
Q

What angle of deflection in the rudder is permitted at speeds up to 150 knots?

A

30 degrees

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21
Q

What angle of deflection is permitted in the rudder at speeds of 150-200 knots?

A

15 degrees

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22
Q

What angle of deflection in the rudder is permitted at 200 knots?

A

5.7 degrees

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23
Q

What are ruddervators also known as?

A

V-tails

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24
Q

How is a yaw motion made in v-tail aircraft ?

A

When one surface moves up and the other down

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25
Q

On a v-tail, when both control surfaces are moved up at the same time, what happens to the orientation of the aircraft?

A

Nose up

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26
Q

What advantage is there for v-tail aircraft?

A

Saves weight as no Vertical stabiliser required

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27
Q

What are the disadvantages of v-tail aircraft? [3]

A
  • Large Control surfaces,
  • Both motions can’t be achieved at the same time,
  • Complicated adjustments
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28
Q

What are elevons?

A

Elevator and aileron combination

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29
Q

What 2 lift devices are there?

A
  • Flaps

- Slats

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30
Q

With flap and slat extension, what changes on the wing?

A

Increased camber

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31
Q

What are flaps and slats used for?

A

Increase lift at low speed flight

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32
Q

What drag devices are there? [2]

A
  • speed brakes

- Spoilers

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33
Q

Where are flaps usually located?

A

Trailing edge

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34
Q

What percentage of lift is created by the several types of flaps? [4]

A
  • Plain flap = 55%
  • Split edge flap = 65%
  • Slotted flap = 70%
  • fowler flap = 95%
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35
Q

Which flap is most effective at generating lift?

A

Fowler flap

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36
Q

What percentage of lift is generated by slats?

A

35%

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37
Q

Where are spoilers located?

A

On the upper surface of the wing

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38
Q

What is the function of spoilers?

A

Increase drag and reduce lift

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39
Q

What effect does spanwise flow have on the boundary layer?

A

Thickens the boundary layer towards the wingtips

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40
Q

What devices could be used to prevent spanwise flow? [3]

A

-Wing fences-
sawtooth leading edge
-stall strips

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41
Q

What do wing fences do to airflow?

A

Keep the air going in a straight line

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42
Q

What does a vortex generator produce?

A

Lift

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43
Q

What does a vortex generator do?

A

Takes high energy air from outside the boundary layer and mixes it with the low energy air.
Reenergise air flow within the boundary layer

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44
Q

Where are stall strips fixed?

A

On the leading edge near wing root

45
Q

What does the stall strip do?

A

At high angles of attack, Creates turbulent flow, creating a progressive outward stall starting from the root to minimise the risk of going out of control

46
Q

What do trim systems do?

A

Compensate for the imbalance of the aircraft

47
Q

What can flight control systems be divided into? [3]

A
  • Control inputs
  • Control transmissions
  • Control surface output
48
Q

What is required for combined control inputs to control rudder/elevator motions on v-tails?

A

Mixer unit

49
Q

What rotates within the mixer unit?

A

Gimbal

50
Q

Where are the control inputs located for the secondary flight controls?

A

Centre pedestal

51
Q

What is used to control pitch trim?

A

Pitch trim wheel

52
Q

what 3 types of control runs are there?

A
  • mechanical
  • hydraulic
  • electric
53
Q

what is aerodynamic horn balance?

A

part of the surface forward of the hinge line, moves into the wind aiding deflection

54
Q

what is a balance tab?

A

deflects the control surface in the opposite direction,

reduces efficiency of control surface but assists deflection

55
Q

what two parts make up the balance panel?

A
  • upper chamber

- lower chamber

56
Q

how do balance panels work?

A

a difference in pressure produces a force on the balance panel and assists deflection.

57
Q

how is the static pressure from outside the balance panels allowed into the chambers?

A

via slots

58
Q

In a balance panel, why is the upper chamber smaller?

A

as the airflow assists in returning the control surface into a streamlined profile

59
Q

what is an anti-balance tab?

A

deflects in the same direction as the control surface, increasing efficiency of the control surface, but more effort is required

60
Q

Where do you operate control tabs from?

A

from the flight deck, directly by the pilot

61
Q

how do control tabs work?

A

the pilot operates the tab and lift is produced by the tab which operates the control surface

62
Q

how does a trim tab operate?

A

operated in the flight deck, with a cable system, a screw jack and trim rod

63
Q

what does the trim tab do when it’s deflected?

A

respositioned to a new neutral position, the ‘trim position’

64
Q

how fast is the speed of sound in m/s at 20 degrees C

A

343.2m/s

65
Q

which speed region is where the air is incompressable?

A

subsonic

66
Q

what are the 3 speed regions? and what are the mach regions for each?

A
  • subsonic <0.8
  • transonic 0.8-1.2
  • supersonic 1.2-1.5
67
Q

which speed region is where the air density can change?

A

supersonic

68
Q

what is critical mach number?

A

the highest speed before any part of the aircraft travels at the speed of sound

69
Q

what is MACH?

A

aircraft speed divided by the speed of sound

70
Q

what is a build up of pressure concentration also called?

A

shockwaves

71
Q

at what mach does a normal shockwave occur?

A

mach 1.2

72
Q

what occurs behind the normal shockwave?

A

a large increase in static pressure

73
Q

when the airspeed exceeds the speed of sound, what shockwave forms?

A

oblique shockwave

74
Q

what are the characteristics of an oblique shockwave?[2]

A
  • slight change of direction

- small decrease in speed

75
Q

what forms directly behind the oblique shockwave?

A

normal shockwave

76
Q

what is wave drag?

A

portion of total drag which is due to shockwaves

77
Q

what 2 ways reduce wave drag?

A

vortex generators, area rule

78
Q

what does a vortex generator create inside supersonic airflow?

A

oblique shockwave

79
Q

what is area rule?

A

cross section areas plotted against body length to show smooth curve on area diagram

80
Q

what structural design could aide the area rule?

A

waisted fuselage

81
Q

which thickness profile is used for aircraft designed for super sonic speeds? why?

A
  • thin

- because shockwaves form smaller when approaching transonic and super sonic speeds

82
Q

what 2 things do designers of wings have to take into account?

A
  • strong enough to take the weight

- house the fuel tanks

83
Q

swept wings have a longer chord length and?

A

a reduced thickness for aerodynamic purposes

84
Q

what is the sweep angle of modern jets?

A

30 degrees

85
Q

what does a higher sweep angle do? [2]

A
  • reduces thickness

- increase critical mach number

86
Q

what advantage does a moveable sweptwing have? [2]

A
  • improve performance at low speeds (thicker chord to length ratio)
  • high speeds, has a greater critical speed
87
Q

what design features do transonic profiles have? [3]

A
  • flatter upper surface
  • more curved leading edge
  • thinner trailing edge
88
Q

what does a transonic profile do to air flow?

A

airflow immediately accelerates because of rounded leading edge,
then decellerates because of the flat upper surface giving off a smaller shockwave and no flow seperation behind the shockwave so it can be used for lift

89
Q

on a transonic profile, what helps with generating lift?

A

negative chamber at the trailing edge on the lower side recduces velocity of airflow and increases static pressure (higher static pressure, greater lift)

90
Q

what is a transonic profile also known as?

A

rear loaded wings

91
Q

what advantages do transonic profiles have over conventional wings? [5]

A
  • made out of thinner and lighter material allowing for greater wingspan without huge weight increase
  • reduction in drag,
  • bigger wing bigger fuel tanks
  • greater lift means wings can be smaller
  • higher mach numbers means sweep angle can be reduced (improves low speed characteristics)
92
Q

what is the disadvantage of transonic profiles?

A

from below critical mach number to just above, greater drag than conventional

93
Q

where does the shockwaves appear first in the transonic region?

A

wing root, at its thickest

94
Q

what is the name given to the flow seperation on the control surfaces in the transonic region?

A

shock stall or high speed stall

95
Q

what is the reaction known as when the aircraft has a nose down reaction after passing critical mach number?

A

tuck under effect

96
Q

what system can automatically prevent tuck under?

A

mach trim system

97
Q

what must the horizontal stabiliser do to compensate for the tuck under effect?

A

increase the downward acting force

98
Q

what effect does transonic flight have on the elevator

A

has a different effect, operates opposite to usual operation

99
Q

what are some aircraft installed with to prevent the elevator from operation in transonic flight?

A

elevator lock

100
Q

what 4 things change when airflow passes through a shockwave?

A
  • density
  • pressure
  • temperature
  • velocity
101
Q

how are temperature, pressure, density and velocity effected when air flow passes through a shock wave?

A
  • density increases
  • pressure increases
  • temperature increases
  • velocity decreases
102
Q

what angle does a normal shock sit at in relation to airflow?

A

right angle

103
Q

what happens to the airflow after a normal shockwave?

A

slows suddenly and generates heat and keeps going in the same direction

104
Q

what does an expansion wave do to airflow?

A

increases speed an turns away from the preceding air flow, follows the surface

105
Q

how is stability increased?

A

the distance between centre of gravity and centre of lift is increased

106
Q

what must be slowed when entering an engine intake? and how?

A

airflow the use of shockwaves with the least possible waste of energy

107
Q

how can shockwaves be used in engine intakes?

A

creating oblique shockwaves to slow air gradually minimising energy loss, and then a normal shock wave

108
Q

at what temperature does aluminium lose 80% of its strength?

A

250 degrees c

M11 (22 decks)

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