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Module 13 EASA Part 1 > 13.7 Flight Controls > Flashcards

13.7 Flight Controls Flashcards

1
Q

In a manually operated control system how are the requirements of CS 25 met following a control jam or severance?

A
  • Duplicating aileron and elevator control runs
  • Providing a disconnect unit so that the pilot’s and co–pilot’s controls can be disconnected from each other
  • Pilot controls left aileron and left elevator, co–pilot controls right aileron and right elevator
  • Control runs are separated by running along opposite sides of the fuselage
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2
Q

What is the maximum deflection of a cable through a fairlead?

A

3°

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3
Q

What must be ensured about the fitment of a cable guard?

A

Does not interfere with the rotation of the pulley

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4
Q

To achieve differential aileron movement a quadrant may be used. What other method may be employed?

A

Bellcrank levers

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5
Q

How are the primary flying controls in a manually operated system protected from damage due to wind gusts?

A

Gust locks or gust dampers

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6
Q

Where would you find the primary control stops and the secondary control stops?

A

In cable systems

Primary (first to make contact) – adjacent to the control surface

Secondary (will have a specified clearance when the primary stops are in contact) – control cabin end of the control run

Opposite is true of push pull systems

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7
Q

What are the advantages of flying control systems using a push pull tube operation?

A
  • Only a single control run is required since push pull tubes transmit motion in both directions
  • The control system does not apply loads to the structure, as with cable systems
  • Tubes and aircraft structure are usually made of the same material and thus expand and contract by the same amount
  • Less prone to damage and wear
  • Overcomes stretching and reduces friction
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8
Q

What is the purpose of a bellcrank lever?

A

Transmit force and permit a change in direction of the force

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9
Q

What does the torque tube do?

A

Linear motion of a push pull tube is changed to rotary motion

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10
Q

What does a stall protection system continuously monitor?

A

Aircraft angle of attack and the position of the slats and flaps

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11
Q

At what speed is the stall warning system designed to operate at?

A

5% above the stalling speed for the particular flap/slat configuration

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12
Q

What would happen if the pilot took no action following a stall warning?

A

A stick pusher or nudger automatically recovers the aircraft from the stall

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13
Q

If an aircraft has duplicated stall warning and recovery systems, how many would have to operate in order for warning and recovery?

A

If either system detects a stall condition, it will vibrate the column

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14
Q

What does the electrically operated stick pusher do when the aircraft reaches a specified angle of attack and speed combination?

A

Actuator moves the control columns forward

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15
Q

What are the differences between power assisted and power operated controls?

A

Power assisted – Force exerted by the pilot is supplemented by hydraulic power, pilots gets feedback from control surfaces, controls are reversible and conventional trim tabs are used

Power operated (or fully powered) – Moved entirely by hydraulic power, pilot provides only the small force necessary to operate a servo valve, controls are irreversible and artificial feel is required for the pilot

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16
Q

What are the five requirements of a powered flying control system?

A
  • Sensitivity
  • Stability
  • Irreversibility
  • Feel
  • Back–up
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17
Q

What is minimum valve overlap?

A

Minimum valve overlap gives sensitivity

This means that the ‘lands’ of the moving valve only just close off the pressure and return ports

Any movement of the valve, no matter how small, will allow fluid to flow to the actuator and cause it to move

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18
Q

What three factors ensure stability in a powered flight control system?

A
  • Elimination of backlash or lost motion in the control system
  • Keeping the hydraulic system free from air
  • Fitting spring or hydraulic dampers in the control system
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19
Q

What would be the effect of the pilot having no feel or proportional feedback from the control surface?

A

The pilot wouldn’t be able to gauge the degree of deflection of the control surfaces

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20
Q

What are the two methods of achieving redundancy within a powered flying control system?

A
  • Manual reversion
  • Duplication of the power units or the power supply
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21
Q

How does a ram mounted power assisted control achieve negative feedback and ‘nulling’ of the actuator?

A

The pilot makes a selection with the control column, which remains in this position

The actuator body moves and the selector valve body moves with it until the drillings are covered

This stops the supply of fluid to the actuator, stopping the movement of the control surface and ‘nulling’ the input signal

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22
Q

What is the purpose of the interconnecting valve?

A

When there is no hydraulic pressure, the interconnecting valve opens under spring pressure

Allows hydraulic fluid to move from one side of the ram to the other

Allows control movement with powered controls selected OFF, or with a hydraulic failure

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23
Q

How does a body mounted power assisted control achieve negative feedback and ‘nulling’ of the actuator?

A

Pilot moves the control, the servo valve moves, which allows fluid to pass to an end of the actuator

The ram moves, which moves the control surface, and the summing lever returns the servo valve to the neutral or nulled position

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24
Q

What are the three functions of the servo valve?

A
  • Direction of movement
  • Rate of movement
  • Magnitude of movement
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25
What are the two types of PCU stuck valve detection system?
* Stuck valve detector struts * Jam indicator
26
What effect would operation of the flying control unit transfer valve by the autopilot have on the cockpit controls?
Moves the associated cockpit control
27
What is a tandem actuator?
Double ended actuator with each actuator having its own servo or selector valve, ram and hydraulic supply One supply has sufficient power available to operate the control surface
28
What three factors affect the force exerted by the control surface?
* Aircraft speed * Air density (altitude) * Deflection of control surface
29
What is the main disadvantage of a spring feel unit?
Only gives a 'feel' of the controls in proportion to the control surface deflection, taking no account of density and speed
30
What does the force required by the pilot to displace the diaphragm in the ‘Q’ pot depend upon?
Force required by the pilot to displace the diaphragm varies with aircraft speed and air density
31
What would happen to feel if the diaphragm of a ‘Q’ feel pot was to rupture?
The pilot would lose 'feel'
32
What is the effect of trimming a fully powered system on a spring feel unit or ‘Q’ pot?
The spring feel unit or 'Q' pot should be returned to the neutral position or 'no load' condition
33
Give 3 examples of failsafe and multiple system provision.
* Tandem power control actuator * Split control surface * One piece control surface with two power control actuators
34
Why is it advantageous to move the entire stabiliser rather than to operate the elevators?
Moving the elevator out of continuation with the stabiliser causes drag On jet transports, elevator drag has a significant effect on airspeed and fuel consumption
35
What are the three methods of repositioning the horizontal stabiliser?
* Energising an electric actuator motor using two switches on the control columns. Using two switches prevents actuator runaway. Both switches must be operated before the motor will run * By a trim servomotor which is operated by signals from the AFCS, or where AFCS is not in control, by signals from a Mach trim system * Manually operated trim wheels and control cables (used for emergency operation following failure of the other two methods)
36
The stabiliser screw Jack is operated by a two speed electrical motor. What determines motor speed?
Trailing edge flap position Operates at low speed when the flaps are retracted
37
There are two stabiliser trim switches, one energising an arming solenoid one energising a command solenoid. How many switches need to be operated for the electrical motor to run in either direction?
Both switches are required to be made
38
When would the stabiliser need to be in the green range and what would happen if it wasn't?
For take-off Take-off warning horn will sound
39
When the stabiliser is trimmed, what automatically moves the elevators into their new faired neutral position?
Neutral shift rod mechanism
40
As speed increases beyond .7 Mach, The Mach trim actuator will retract causing the elevator PFCU servo to move. What now causes the stabiliser to move and fair the elevators?
The Mach trim actuator retracts to rotate the trim centring and feel unit
41
In a typical aileron control system how are the controls returned to neutral by the feel unit following an input?
The artificial feel unit consists of a spring loaded roller held into a centring detent in a cam profile fixed to the quadrant This mechanism centres the aileron controls
42
If an aircraft is subject to control reversal how is roll control enabled when the outboard ailerons are locked out?
Inboard ailerons
43
Airspeed and what other factor determine aileron lockout?
Flap position
44
Why do the spoilers remain retracted until a control wheel movement beyond for example 14 degrees?
Allows for lateral trimming
45
Why are the spoilers locked down in flight, these locks having to be overcome before spoiler extension?
Prevent spoiler float when a hydraulic system becomes depressurised during flight If they were not locked, the reduction in pressure over the top of the wing would raise the spoiler panel into airflow
46
How does a Q pot limiter restrict rudder movement at higher speeds?
Q pot limiter has a stepped cone attached, and Q pot is supplied with pitot and static pressure in the usual way Stepped cone restricts movement of the claw shaped stop which forms part of the rudder operating mechanism Increasing speed increases the size of step used as a stop, thus limiting rudder movement
47
What are the advantages of a fly by wire system?
* Weight saving * Reduced maintenance times * Gust load alleviation * Automatic manoeuvre envelope protection * Improved handling * Fuel saving
48
Describe automatic manoeuvre envelope protection.
In aircraft without automatic manoeuvre envelope protection, the pilot may start a manoeuvre which would be outside the flight manoeuvre limits for these aircraft In FBW, pilot moves the controls, but a computer is programmed in such a way that the command signals generated and distributed, limit the response of the controls Thus ensuring that the flight manoeuvre envelope is not exceeded
49
What is the general layout of components of an active control system known as?
System architecture
50
What is a control law?
The manner in which the computers create control surface movement and thus aircraft movement is called the control laws
51
What are the two computers installed that control pitch and roll known as?
Elevator and aileron computer (ELAC) and Spoiler and elevator computer (SEC)
52
Two independently operated electrically signalled hydraulic actuators control elevator movement. Whilst one is in the active mode what is the other actuator doing?
Damping mode
53
When autopilot is in operation what happens to sidestick movement?
Remains in the neutral position
54
If the ELAC’s were unserviceable, how is pitch control achieved?
SECs no 1 and 2 take over their role and provide pitch control This is known as the alternate control law
55
Describe the levels of redundancy available in the pitch control system.
1. Normal control law - Controlled by ELACs 2. Alternate control law - Controlled by SECs 3. Direct control law - Stick to elevator direct control 4. Mechanical back-up - Mechanical back-up
56
What is the LAF function in roll?
Where wind gust causes the wing to bend, ailerons are rapidly utilised to alleviate the load on the wing
57
In yaw, what effect does yaw damping and turn coordination have on the pilots rudder pedals?
The pedals are not moved (no feedback)
58
What is the purpose of the collapsible or detent strut in aileron control system jam protection?
Detent strut breaks out at a predetermined force, allowing movement of the unjammed control circuit
59
What device would provide elevator control system jam protection?
Control columns which are interconnected by a layshaft which incorporates a break out device May in addition be a spring loaded dog clutch
60
If a control disconnect occurs, separating the left and right elevator/aileron control circuits, what else would you expect?
A warning on the CWP
61
What is the maximum free play at the trailing edge of a trim tab?
2.5% of the tab average chord
62
What type of powered flying control is irreversible?
Fully powered flying controls
63
What are the advantages of the body mounted power assisted unit?
* Less space required as only the ram moves * Doesn't have a noticeable affect on CofG
64
What are the advantages of the ram mounted power assisted unit?
* Doesn't require complex linkages
65
What is another purpose of the simple spring 'feel' unit, apart from giving 'feel'?
Once the pilot removes the fore on the controls after compressing the spring, the spring expands and centralises the column and selector (servo valve), thus centralising the control surface
66
How is the Q feel unit designed, in terms of rod and diaphragm movement, when the cockpit control is moved in either direction?
The rod and diaphragm are always deflected against pitot pressure
67
What are the new positions of the servo valve, control surface and the cockpit primary controls known as in an aircraft with fully powered controls when in a trimmed position?
Control surface bias
68
What is the purpose of the flutter damper?
Prevent aileron flutter should both PCUs fail
69
What is the aileron deflection when the control wheel is deflected by 14°?
4°
70
What are the conditions for automatic operation of the speedbrake spoilers?
* Both main landing gears on the ground and the bogies not tilted * Thrust levers at idle * Wheels rotating eg 60 kts * No faults in the speedbrake system
71
If the speedbrakes are raised and the aircraft is rolled, which spoilers will lower?
The spoiler panels on the upgoing wing
72
How are the spoilers locked in the retracted position?
By locking fingers
73
When would it be considered that repainting a control surface has no effect on the mass balance?
Paint stripping down to bare metal and repainting to the original standard
74
What will each additional coat of paint have on the mass balance of a control surface?
Reduce the repair allowance by a specific amount All painting of this nature must be recorded
75
What might be necessary when carrying out a static friction check in a power-operated control system?
Disconnect the 'feel' spring struts to make sure that the true friction value can be obtained
76
Describe active load control.
Where bending loads are imposed on flying control surfaces by gusts, etc Active control uses sensors to automatically detect local accelerations and use control surfaces to reduce the stresses
77
What are the three benefits of using an active load control system?
* Reduction of structural loads * Improvement of fatigue strength * Improvement in ride comfort
78
How does an active load control system compensate for high lift loads?
The ailerons are raised a few degrees when the flaps are not fully up and the speed less than a specified value
79
How would an active control system be incorporated into a conventional power operated flying control system?
Active control system sends commands to an electrically operated servo valve incorporated in the PFCU
80
If a repair to a mass balanced control surface is permissible, why is recording so important?
So that it can be taken into account in the event of further repairs or overpainting Thus ensuring that the moment of any repair or overpainting the existing finish is within the allowance permissible
81
List the five occasions when flight control system rigging is to be carried out.
* After manufacture * When stated in the aircraft maintenance schedule * When a component in the system is changed * After a reported flying fault from the pilot * Sometimes after a heavy landing or flight through turbulent air
82
State two precautions to be applied when using rigging pins.
* Rigging pins should be kept under strict control that their whereabouts are always known * Refer to part number for the pin so as to ensure the correct pin is being used in the correct location * Must be serviceable before use and have attention getting flags or discs attached to them * Installation and removal of rigging pins should be controlled by the use of worksheets
83
What is meant by the term sense check?
Cockpit controls are moved and a check made to make sure that the control surfaces move in the correct sense Position indicators must also move in the correct sense Correct sense of movement under autopilot command must also be checked
84
Describe a static friction check.
The control system is pulled through its full range of movement using a spring balance attached to the control column and rudder pedals Force required to operate the controls should not exceed that given in the maintenance manual
85
What must be carried out following disturbance of a flying control system?
It is a **vital point** and so requires duplicate inspection
86
What are the advantages of using a single flap power drive system over multiple jacks?
* Better asymmetric protection since there is only one power unit to be stopped * All the hydraulic components are contained in a single unit * The alternate operating system can be built into the power drive unit
87
What is the purpose of the priority valve in the electrohydraulic flap operating system?
Stop the hydraulic fluid to the power drive unit should the pressure drop to a predetermined value
88
In the event of a jammed flap, how much increase in torque would cause the torque limiter to separate the input drive from the output drive?
20% greater than normal operating torque
89
How is final drive transmitted to the flap assembly?
Transmission gearbox, a universal joint, a ballnut and a jackscrew actuator
90
As the flaps are extending, what locks the fore flaps into position and allows the mid and aft flap to extend further?
Toggle stops
91
Describe flap asymmetry.
Flaps which are not synchronised on each wing
92
What is the purpose of the comparator synchro in the flap asymmetric protection system?
Compare the position of pointers, which indicate position of flaps on each wing, and actuating a cam operated switch when the points are separated by more than a predetermined amount This energises an asymmetric shut off relay, which drives a trailing edge flap bypass valve to bypass and stop the hydraulic motor
93
How does the flap bypass valve enable operation of the alternative flap drive system?
Interconnects the flap hydraulic motor pressure and return ports to prevent it from operating during operation of the flap alternate drive system
94
How would a flap transmission over speed be detected?
In the event of a mechanical overspeed condition, the overspeed governor fly weights expand and force the rocker arm roller off the disc brake, applying brake pressure to the input shaft
95
In a mechanical flap asymmetric protection system what would cause displacement of the idler gear?
Different rates of rotation of the alternate bevel gears from each flap
96
Typically, what is the primary power source for leading edge flaps?
Provided by air motors supplied from the aircraft bleed air pneumatic system
97
What causes leading edge flaps to automatically retract on landing?
When reverse thrust is selected
98
When would autoslat operate?
At a high angle of attack and slow speed
99
What would happen if a slat asymmetry is detected?
Asymmetry transducers at the outer end of the slat drive torque shafts send position signals to a comparator If the slats are sensed to be asymmetric, the comparator will stop the drive unit and apply the asymmetry brakes
100
What would initiate a take off configuration warning?
A take off is attempted with the aircraft in the incorrect configuration
101
If alternate flaps are selected, what is the rate at which the alternate electric motor positions the flaps compared to the normal hydraulic motor?
At a slower rate under the control of an electric selector switch

Module 13 EASA Part 1 (20 decks)

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