Module 7 - Wing and High Lift Devices Testing

Question 1

Why are aircraft equipped with high lift devices?

Answer 1

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

Question 2

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

Answer 2

take-off, landing

Question 3

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

Answer 3

stoppage speed

Question 4

Stoppage speed for take-off

Answer 4

1.2 VS1

Question 5

Stoppage speed for landing

Answer 5

1.3 VSO

Question 6

What determines the stalling speed?

Answer 6

wing’s CLMAX

Question 7

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

Answer 7

high, lowest

Question 8

formula for stalling speed

Answer 8

VSTALL = √(2W)/(ρACLMAX)

Question 9

What is the relationship between CLMAX and VSTALL

Answer 9

inverse relationship

Question 10

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

Answer 10

camber

Question 11

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

Answer 11

lift coefficient (CL), CLMAX

Question 12

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

Answer 12

high drag, nose-down attitude

Question 13

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

Answer 13

flaps, less cambered

Question 14

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

Answer 14

flap

Question 15

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

Answer 15

low-speed aerofoils

Question 16

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.

Answer 16

high-speed aerofoils

Question 17

Types of trailing edge flaps

Answer 17

• plain flap
• split flap
• slotted flap
• fowler flap
• slotted fowler flap

Question 18

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

Answer 18

plain flap

Question 19

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

Answer 19

plain flap

Question 20

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.

Answer 20

split flap

Question 21

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

Answer 21

split flap

Question 22

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

Answer 22

higher

Question 23

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

Answer 23

higher pressure air, re-energize

Question 24

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

Answer 24

slots

Question 25

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

Answer 25

greater increase, less, complicated

Question 26

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

Answer 26

fowler flap, wing area, camber

Question 27

Can fowler flaps be slotted?

Answer 27

Yes

Question 28

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).

Answer 28

fowler flap

Question 29

Why is the pitching moment adjustment bigger for fowler flaps?

Answer 29

because of the chord's rearward extension

Question 30

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

Answer 30

increased, decreased

Question 31

the lowering of the flap ________ the effective attack angle

Answer 31

raises

Question 32

What decreases the acceleration during take-off?

Answer 32

drag

Question 33

Flaps should offer as _________ drag as possible.

Answer 33

little

Question 34

When and why is drag of the flap advantageous?

Answer 34

during landing because it contributes to the braking force

Question 35

Adding drag during approach also increases ____________.

Answer 35

velocity stability

Question 36

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

Answer 36

larger

Question 37

the lift/drag ratio is a measure of _____________

Answer 37

aerodynamic efficiency

Question 38

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

Answer 38

lift/drag ratio

Question 39

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

Answer 39

pitching moment

Question 40

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

Answer 40

pitching moment

Question 41

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

Answer 41

distribution of pressure, flap area

Question 42

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

Answer 42

Pressure Center

Question 43

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

Answer 43

wing downwash

Question 44

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

Answer 44

increase, decrease

Question 45

the pitching moment will be affected by ________________

Answer 45

flap form, wing position, and tail plane relative position

Question 46

the pitching moment may be ______________

Answer 46

nose-up, nose-down, or near zero

Question 47

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

Answer 47

steady flight

Question 48

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.

Answer 48

increase, decreased

Question 49

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

Answer 49

nose-down attitude

Question 50

What provides greater visibility of the landing field?

Answer 50

nose-down attitude

Question 51

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

Answer 51

leading edge

Question 52

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

Answer 52

leading edge flap because it increase leading edge camber

Question 53

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

Answer 53

Krueger flap

Question 54

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

Answer 54

Krueger flap

Question 55

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

Answer 55

variable camber leading edge flap

Question 56

unlike trailing edge flaps, leading edge devices can be _________

Answer 56

fully extended (deployed) or retracted (stowed)

Question 57

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

Answer 57

delay separation

Question 58

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

Answer 58

leading edge slot

Question 59

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

Answer 59

slat

Question 60

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

Answer 60

slat

Question 61

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

Answer 61

delaying the separation

Question 62

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

Answer 62

high lift coefficient

Question 63

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

Answer 63

pressure shifts

Question 64

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

Answer 64

closed position

Question 65

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

Answer 65

pressure 'suction' caused by the shift of the stagnation point

Question 66

disadvantages of the slot

Answer 66

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

Question 67

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

Answer 67

minimal

Question 68

_______________ are used for most large transport planes.

Answer 68

both trailing edge and leading edge systems

Question 69

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

Answer 69

before

Question 70

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

Answer 70

withdrawn

Question 71

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 _________________.

Answer 71

automatically halted

Question 72

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

Answer 72

asymmetrical situation

Question 73

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

Answer 73

prevent damage

Question 74

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

Answer 74

flap load relief system

Question 75

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

Answer 75

speed drops below Vfe

Question 76

What is Vfe?

Answer 76

Vertical Flap Extension

Question 77

flap setting for take-off

Answer 77

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.

Question 78

flap setting for climb

Answer 78

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.

Question 79

flap setting for landing

Answer 79

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

Question 80

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.

Answer 80

boundary layer, plenum chamber

Question 81

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

Answer 81

boundary layer control via suction

Question 82

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

Answer 82

ducted overboard

Question 83

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

Answer 83

blowing

Question 84

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

Answer 84

boundary layer control via blowing

Question 85

methods of preventing the separation of boundary layer

Answer 85

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

Question 86

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.

Answer 86

nose-down, nose-up

Question 87

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

Answer 87

75%, 25 deg

Question 88

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

Answer 88

120%, 28 deg

Question 89

combination used on air haulage aircraft

Answer 89

double-slotted fowler flap and slat combination