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ATPL Systems and Aerodynamics > Flight Controls > Flashcards

Flashcards in Flight Controls Deck (44)
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1
Q

Why do large jet transport aircraft have powered flight controls?

A

Do deal with the large loads and changes in CoG.

2
Q

What level of redundancy is required for powered flight controls?

A

Triple redundancy is required if manual reversion is NOT available.

3
Q

Would fly-by-wire require triple redundancy or could it use manual reversion?

A

triple redundancy would be required, because there are not direct cables (manual control), it is all electrically driven.

4
Q

What is Q feel and why does it exist?

A

Because hydraulic forces are used to move the control surfaces, Q feel is used to provide some sort of feedback to the pilot to stop them from overstressing the airframe.

5
Q

How does the Q feel system dictate what ‘feel’ is given to the pilots?

A

Based on airspeed.

6
Q

What is the purpose of ‘control balancing’?

A

To reduce control loads

7
Q

What is the purpose of the ‘flexible seal’?

A

To reduce the control pressure / hydraulic force

8
Q

What is jack stalling?

A

When air loads are so strong that they actually prevent the hydraulic system from moving the controls.

9
Q

What is the main benefit of a variable incidence tailplane?

A

Allows pitch to be trimmed over a large CoG range whilst still allowing full elevator control to be available. Compared to elevator trim tabs, it also produces less drag

10
Q

Do trailing edge devices increase or reduce the body angle on approach?

A

reduce (remember flaps typically give you better forward vision on final)

11
Q

What is the purpose of the fowler flaps?

A

Move back and down to increase surface area

12
Q

What is the purpose of slotted flaps?

A

Re-energise the boundary layer (gaps in between the flaps will accelerate air, like lots of little wings)

13
Q

What is a flap limiter?

A

A device which will automatically retract flaps (or prevent flap extension) if the speed is too high. NOTE that the flap position handle does NOT move.

14
Q

What is a hydraulic blow back valve?

A

Allows the flaps to get retracted when the air loads are excessive (a form of flap overspeed protection)

15
Q

Compared to a clean wing, what will trailing edge flaps do to the critical AoA?

A

Decrease (you will stall at a slower speed but lower nose attitude)

16
Q

Compared to a clean wing, what will leading edge devices do to the critical AoA?

A

Increase

17
Q

How do spoilers assist roll?

A

They are extended on the down-going wing to dump lift and increase drag.

18
Q

Why is height lost during a turn with spoilers?

A

Because they significantly reduce lift on the downgoing wing, resulting in height loss.

19
Q

What is aileron lockout?

A

A system which prevents OUTBOARD ailerons being used at high speeds. Inboard ailerons are active at all times.

20
Q

How are the spoilers stopped from being deployed at high speed?

A

Blow down: The air loads will simply prevent deployment of the spoilers.

21
Q

All powered flight controls have how many hydraulic units?

A

At least two (through 3 is required for certification)

22
Q

Why are there two switches for electric aileron trim?

A

To prevent inadvertent activation of trim.

23
Q

What is one of the risks associated with spoiler walk down?

A

Tendency for height to be lost when spoilers are used, therefore large roll inputs should be avoided at low aircraft speeds on approach.

24
Q

What is the benefit of speed brakes?

A

In addition to aerodynamic drag, it also places the weight on the wheels which assists with braking.

25
Q

To assist in yaw control redundancy, what systems are available?

A

Either have two components to the rudder (if one fails the other is still available), or have multiple actuators for the same rudder surface.

26
Q

When rudder trim is applied, to the pedals move?

A

Yes, they are displaced proportionally

27
Q

What is the purpose of a rudder ratio changer?

A

As speed increases, the hydraulic force available can overstress the rudder, so it will automatically reduce the amount of deflection available.

28
Q

What is a rudder comparator?

A

For systems which have an upper and lower rudder surface, it will detect if the rudder ratio changer has jammed, causing an uneven displacement of the rudder.

29
Q

What are the two types of yaw dampers?

A

Parallel type: rudder pedals are moved as the yaw damper moves (must be off for takeoff and landing)
Series type: rudder pedals are independent (therefore can be on at all times except gusty/crosswind conditions).

30
Q

What are the two main purposes of the moveable stabiliser?

A

Reduce drag compared to trim tab, and to deal with large changes in CoG.

31
Q

What is the natural tendency of the trim when trailing edge flaps are deployed?

A

Nose pitch down

32
Q

What is the natural tendency of the trim when leading edge flaps are deployed?

A

Nose pitch up

33
Q

When one of the two hydraulic systems controlling stab trim is inoperative, what happens to trim rate?

A

Halved

34
Q

What protection is in place to prevent stab trim runaway?

A

Hydraulic cutoff valves

35
Q

How are slats deployed?

A

they are deployed with the flaps (don’t have a seperate lever). Typically stage 1 of flaps will extend slats as well

36
Q

What happens if there is a failure of the hydraulic system which moves the flaps?

A

Electrical system as a backup

37
Q

What happens to the CoL if only the inboard flaps are extended on a swept wing aircraft?

A

Moves inwards and forward (pitch up)

38
Q

What happens to the CoL if only the outboard flaps are extended on a swept wing aircraft?

A

Moves outwards and rearwards (pitch down)

39
Q

How are flaps protected from operating asymmetrically?

A

There is a system which will identify if a specified value of flap asymmetry exists and will prevent further deployment of the flaps.

40
Q

What is the purpose of slats?

A

Re-energise the boundary layer by providing larger surface. Useful for low speeds as wings are designed for high speed.

41
Q

What systems can extend the leaing edge slats?

A

Hydraulics or pneumatics primarily, or electrically as a backup.

42
Q

Why do large transport category aircraft have flight control position monitoring?

A

Because the flight deck inhibits view of the control movement (in the same way you want 3 greens for gear down)

43
Q

What is a limitation of the flight control position monitoring system?

A

the system is used to indicate full control movement on the ground, however airborne full deflection is rarely used, and therefore doesn’t provide much information.

44
Q

What information does the Digital stall Warning Computer require to activate the stick pusher/shaker?

A

Angle of airflow vane, flap position indicator, N1 speed, N2 speed, air/ground relay, ADC, leading edge module. If these weren’t available, the system would engage the pusher at innapropriate times (e.g. on the ground)