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Aeronautical Laboratory > Module 7 - Wing and High Lift Devices Testing > Flashcards

Module 7 - Wing and High Lift Devices Testing Flashcards

1
Q

Why are aircraft equipped with high lift devices?

A
  • to reduce the distances from take-off and landing
  • allows operations at greater weights from the provided runway lengths
  • allows carrying higher payloads
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2
Q

The distances of _______ and _______ depend on the velocities required and these are set out in the performance regulations.

A

take-off, landing

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3
Q

One of the criteria for both take-off and landing is for a healthy gap over the _____________.

A

stoppage speed

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4
Q

Stoppage speed for take-off

A

1.2 VS1

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5
Q

Stoppage speed for landing

A

1.3 VSO

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6
Q

What determines the stalling speed?

A

wing’s CLMAX

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7
Q

CLMAX must be as ____ as possible to achieve the ______ possible distances

A

high, lowest

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8
Q

formula for stalling speed

A

VSTALL = √(2W)/(ρACLMAX)

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9
Q

What is the relationship between CLMAX and VSTALL

A

inverse relationship

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10
Q

One of the main factors that defines an aerofoil section’s CLMAX is the _______.

A

camber

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11
Q

Increasing an aerofoil section’s camber increases the ________ at a given angle of attack and increases ________.

A

lift coefficient (CL), CLMAX

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12
Q

A cambered section is suitable for take-off and landing but this would give ______ at cruising speeds and require a very _____________.

A

high drag, nose-down attitude

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13
Q

To maximize the cruise and adjust the section for take-off and landing by using _____, it is normal to choose a __________ aerofoil section.

A

flaps, less cambered

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14
Q

a hinged portion of the trailing or leading edge that can be deflected downwards and thus create a camber increase

A

flap

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15
Q

The flaps will only be on the
trailing edge for ___________.

A

low-speed aerofoils

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16
Q

On _______________ where the leading edge might be symmetrical or have a negative camber, both the leading edge and the trailing edge will generally be flapped.

A

high-speed aerofoils

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17
Q

Types of trailing edge flaps

A
  • plain flap
  • split flap
  • slotted flap
  • fowler flap
  • slotted fowler flap
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18
Q

has a simple construction and provides a reasonable increase in CLMAX, but with a reasonably high drag

A

plain flap

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19
Q

primarily used on low-speed aircraft and where very fast take-off and landing are not necessary

A

plain flap

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20
Q

The flap forms part of the lower surface of the trailing edge of the wing, with the upper surface contour not affected when the flap is lowered.

A

split flap

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21
Q

gives about the same increase in lift as the plain flap at low angles of attack, but gives slightly more at higher angles as there is no increase in the upper surface camber and so separation is delayed

A

split flap

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22
Q

split flap: because of the wake’s increased depth the drag is ______ than for the simple flap

A

higher

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23
Q

The aim of the slot is to guide __________ over the flap from the lower surface, and to ___________ the boundary layer.

A

higher pressure air, re-energize

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24
Q

This retards the airflow separation on the flap’s upper surface.

A

slots

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25
Q

The slotted flap gives CLMAX a _________ than the plain or split flap, and much ____ drag, but has a more ________ design.

A

greater increase, less, complicated

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26
Q

The ___________ travels backwards and downwards, giving initially an increase in __________, and then an increase in _________.

A

fowler flap, wing area, camber

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27
Q

Can fowler flaps be slotted?

A

Yes

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28
Q

the _________ gives the flaps considered the greatest increase in lift, and also gives the least drag because of the slot and decreased thickness (chord ratio).

A

fowler flap

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29
Q

Why is the pitching moment adjustment bigger for fowler flaps?

A

because of the chord’s rearward extension

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30
Q

For lowered flaps, the CLMAX is ________ but the angle of stalling is ________.

A

increased, decreased

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31
Q

the lowering of the flap ________ the effective attack angle

A

raises

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32
Q

What decreases the acceleration during take-off?

A

drag

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33
Q

Flaps should offer as _________ drag as possible.

A

little

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34
Q

When and why is drag of the flap advantageous?

A

during landing because it contributes to the braking force

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35
Q

Adding drag during approach also increases ____________.

A

velocity stability

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36
Q

as the flap angle changes, the changes in drag get ________

A

larger

37
Q

the lift/drag ratio is a measure of _____________

A

aerodynamic efficiency

38
Q

affects the performance of the aircraft in areas such as range, angle of climb which angle of glide

A

lift/drag ratio

39
Q

Flap motion, up or down, typically can cause a _______________ to change.

A

pitching moment

40
Q

caused due to the displacement and downwash at the tailplane of the Pressure Center (CP)

A

pitching moment

41
Q

Moving a trailing edge flap will alter the ____________ over the entire aerofoil chord, but the greatest changes will occur in the __________.

A

distribution of pressure, flap area

42
Q

the ____________ will shift rearward when the flap is lowered, providing a nose-down pitching moment

A

Pressure Center

43
Q

The effective angle of attack to the tailplane is determined by the _____________.

A

wing downwash

44
Q

If the flaps are lowered, the downwash will ________ and the angle of attack on the tailplane will __________, creating a moment of nose-up pitching.

A

increase, decrease

45
Q

the pitching moment will be affected by ________________

A

flap form, wing position, and tail plane relative position

46
Q

the pitching moment may be ______________

A

nose-up, nose-down, or near zero

47
Q

The lift must be equal to the weight when the aircraft is in ____________.

A

steady flight

48
Q

If the flaps are lowered but the velocity is kept constant, the lift will _________ and the angle of attack must be ___________ to maintain it at its original value.

A

increase, decreased

49
Q

if the flaps are down the aircraft can fly in a more ______________

A

nose-down attitude

50
Q

What provides greater visibility of the landing field?

A

nose-down attitude

51
Q

can have very little camber on high speed aerofoil parts and have a tiny radius

A

leading edge

52
Q

What can remedy flow separation at reasonably low angles of attack just aft of the leading edge? Why?

A

leading edge flap because it increase leading edge camber

53
Q

part of the lower surface of the leading edge which can be rotated around its forward edge

A

Krueger flap

54
Q

used on the inboard section to facilitate root stall on a swept wing, because they are less effective than the opposite variable camber

A

Krueger flap

55
Q

as it is deployed, the camber of a leading edge flap can be increased to improve efficiency by offering a better leading edge profile

A

variable camber leading edge flap

56
Q

unlike trailing edge flaps, leading edge devices can be _________

A

fully extended (deployed) or retracted (stowed)

57
Q

The leading edge flap’s main effect is to _____________, thus increasing the angle of stalling and the resulting CLMAX.

A

delay separation

58
Q

a gap between the lower surface and the upper edge of the leading edge, and can be fixed or formed by pushing forward part of the leading edge

A

leading edge slot

59
Q

a small auxiliary aerofoil fixed to the wing ‘s leading edge

A

slat

60
Q

forms a slot when deployed which allows air passage from the high pressure region below the wing to the low pressure region above it

A

slat

61
Q

The slat has the benefit of prolonging the lift curve by _______________ of the boundary layer until a higher angle of attack.

A

delaying the separation

62
Q

Due to its marked camber, when working at high angles of attack the slat itself produces a _____________.

A

high lift coefficient

63
Q

Automatic slot’s motion is caused by ____________ that occur along the leading edge as the angle of attack increases.

A

pressure shifts

64
Q

The high stresses around the stagnation point hold the slat in the ____________ at low angles of attack.

A

closed position

65
Q

What stresses carry forward the slat and build the slot at high angles of attack?

A

pressure ‘suction’ caused by the shift of the stagnation point

66
Q

disadvantages of the slot

A
  • very nose-up attitude at low speeds
  • visibility of the landing area may be restricted when approaching ground
67
Q

The differences in drag and pitching time resulting from the activity of leading edge devices are ________ compared to trailing edge flaps.

A

minimal

68
Q

_______________ are used for most large transport planes.

A

both trailing edge and leading edge systems

69
Q

The leading edge system must be deployed _______ the flap to the trailing edge is lowered.

A

before

70
Q

The trailing edge flap must be _______ until the leading edge unit is lifted when the flaps are withdrawn.

A

withdrawn

71
Q

The deflection on the two sides is contrasted on many flap control systems when the flaps are moving, and if one side fails, the movement on the other side is _________________.

A

automatically halted

72
Q

a failure of the operating mechanism may lead to an _______________ in less sophisticated systems

A

asymmetrical situation

73
Q

On a large aircraft, flaps are prevented to be deployed beyond certain high speed (Vfe) to ___________ to the flaps.

A

prevent damage

74
Q

A ____________ will sense the flap load and prevent flaps deployment.

A

flap load relief system

75
Q

If the flaps selection is made but the speed is too high, the flaps would extend as soon as the _______________.

A

speed drops below Vfe

76
Q

What is Vfe?

A

Vertical Flap Extension

77
Q

flap setting for take-off

A

Lowest take-off speed will be possible at large flap deflection but this gives large increase in drag as well which will make acceleration
to take off speed difficult. So a compromise is made and a lower flap setting is selected.

78
Q

flap setting for climb

A

Climb gradient is reduced by flaps. So if climb gradient is limited, a lesser flap angle could be used to compensate but the take-off distance required will increased.

79
Q

flap setting for landing

A

Landing distance will depend on touchdown speed and deceleration. The lowest touchdown speed will depend on the CLMAX obtained which helps in deceleration.

80
Q

In the process of suction, air is drawn from the _________ which has formed through minute holes into a __________ formed by providing an inner skin over the upper surface of the wing.

A

boundary layer, plenum chamber

81
Q

decreases the thickness of the boundary layer and ensures that longer laminar airflow stays over the wing

A

boundary layer control via suction

82
Q

At the trailing edge of the wing, the air that has been pulled into the plenum chamber is _____________.

A

ducted overboard

83
Q

accomplished by jetting high-velocity air from vents through the upper surface of the wing just below the leading edge

A

blowing

84
Q

speeds up the airflow near the skin of the wing and makes sure the boundary layer stays thin

A

boundary layer control via blowing

85
Q

methods of preventing the separation of boundary layer

A
  1. suction of the slow moving fluid by suction slot
  2. supplying additional energy from a blower
  3. providing a bypass in the slotted wing
  4. rotating boundary in the direction of flow
  5. providing small divergence in a diffuser
  6. providing guide-blades in a bend
  7. streamlining of body shapes
86
Q

The _________ pitching moment of the trailing edge flaps is countered by the _______ pitching moment of the leading edge systems, where flaps and slats are deployed together.

A

nose-down, nose-up

87
Q

Using a combination of a slotted flap and slat increases the aerofoil’s lift by ____ and its stalling angle to _______.

A

75%, 25 deg

88
Q

Using a double-slotted fowler flap and slat combination raises the lift of the aerofoil by ______ and the angle of stagnation by _____.

A

120%, 28 deg

89
Q

combination used on air haulage aircraft

A

double-slotted fowler flap and slat combination

Aeronautical Laboratory (3 decks)

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