Flight Controls Flashcards
How many FCUs (flap control units) are provided?
3
What are the basic functions of the FCUs?
- primary mode control
- secondary mode control (through electric motor) - indication and annunciation (flap position information to EICAS and other systems)
- protections
How many groups of leading flaps are provided, names, and how are they normally powered?
3 - inboard, midspan and outboard
pneumatically (bleed air)
What are the two groups of trailing edge flaps, and how are they powered?
inboard, outboard
hydraulically
How are opposite trailing edge flaps connected?
mechanically for symmetry
What protection features do FCUs provide for trailing edge flaps in primary mode?
flap load relief
flap asymmetry
flap disagreement and uncommanded motion protection
What protection features do the FCUs provide for trailing edge flaps in secondary mode?
flap asymmetry
flap disagreement and uncommanded motion protection
(no load relief)
Describe the function of the FCUs in primary mode.
drive LE flaps pneumatically and TE hydraulically to selected position (flap lever)
Describe the function of the FCUs in secondary mode
- If any flap group fails to move to commanded position, FCU switches to secondary mode (elec motors)
- occurs by symmetrical flap group on both wings
What happens if a primary control failure occurs in either the inboard or midspan leading edge flap group?
both groups revert to secondary mode
What happens if a failure occurs in a leading-edge flap group on one wing?
other wing’s flap group will also move to secondary mode. if occurs during flap movement, wing in primary mode will continue to extend flap first
What happens immediately if a trailing edge asymmetry is detected?
primary mode shut down for failed group - FCUs do not use secondary mode
What EICAS Advisory message displays if all three FCUs fail in their control function?
FLAPS CONTROL
How does the Flap Alternate Control mode work?
bypasses FCUs - simplified electric control system/motors
Is there any asymmetry protection in alternate flap mode?
no protections in alternate mode
State the actions that occur when the Alternate (ALTN) Flaps Arm switch is pushed
- arms flap alternate control mode
- arms alternate flaps selector
- shuts off primary and secondary mode operation
- asymmetry protection not available
- flap lever inoperative
What is the maximum extension of the trailing edge flaps in alternate mode?
25
Describe the secondary mode or non-normal expanded flap position indication for leading edge flaps.
Individual flap groups, with position/ drive unit inop shown
Describe the secondary mode or non-normal expanded flap position indication for trailing edge flaps.
individual flap groups, similar to normal, amber if asymmettry or drive failure
What does an amber “X” mean on an expanded flap display?
position sensor for respective flap failed
Describe the Alternate Mode Expanded Flap Position Indicator.
individual LE/TE groups indication, flap positions to 25
Describe the flap position indication on EICAS if the standby bus is the only powered AC bus.
left wing TE sensors not powered, expanded indication with amber x on left TE flaps
What flaps extend when the flap lever is moved from UP to Flaps 1?
inboard and midspan LE
What flaps extend when the flap lever is moved from Flaps 1 to Flaps 5?
outboard LE and TE to flap 5 position
What flaps sequencing occurs when using alternate flaps?
extend: all LE + TE flaps extend immediately
retract: all TE flaps retract, then LE flaps retract
Describe the flap load relief.
in primary mode (with A/T off), if exceed flaps 30/25, will retract to 25/20 (flap lever position stays the same). If reduce speed will extend again
How long does the flap indication on primary EICAS remain displayed after all flaps are up?
10 secs
What is the effect on the flap system during engine reverse thrust operation?
auto-retraction of inboard and midspan LE flaps - so flap position indicator reflects flaps in transit
Describe the function of the Stabilizer (STAB) Trim Cutout Switches, AUTO position
(guard closed) - supplies hydraulic power for stabilizer trim - shuts off related system hydraulic power (to STCM) if unscheduled trim detected
What surface component is moved when stabilizer trim inputs are made?
horiz. stabilizer
State what occurs when the Stabilizer Trim CUTOUT Switches are in CUTOUT.
- shuts off related hydraulic power to stabilizer trim
Describe the function of the alternate trim switches
- trims stabilizer using alternate control channel
- both switches pushed in same direction powers actuators, drive stabilizer in desired direction
- increased range of stabilizer travel
How do the FMCs calculate correct stabilizer trim greenband?
gross weight CG Takeoff thrust derate
How does the aircraft provide a crosscheck to ensure the correct greenband has been selected?
position of nose gear oleo pressure switch compared to green band
What is the effect on stabilizer trim if the control wheel stabilizer trim switches are used while the autopilot is engaged?
if one AP engaged, will disengage AP. If > one AP engaged, trim switch inhibited
State the effect on the autopilot and stabilizer trim, if the alternate trim switches are used with any number of autopilots engaged.
overrides AP, but does not disengage AP
How many spoiler panels are provided?
12
Which spoiler panels do not function as flight spoilers?
6,7
Which spoiler panels function as speedbrakes in flight?
3-10
Which spoiler panels function as ground spoilers when on the ground?
All
Which spoiler panel is displayed on EICAS status display?
4, 12
Which spoiler panels are extended with the spedbrake lever in the flight detent position
3-10
When do the spoiler panels extend to the UP position during landing, if the speedbrake lever is ARMED?
-thrust lever 1 and 3 near idle
- main gear touch down
When do the spoiler panels extend to the UP position during landing if the speedbrake lever is NOT Armed?
-thrust lever 1 and 3 near idle
- main gear touch down
- thrust reverser 2 or 4 to idle detent
Since the speedbrake lever is in the DN position during takeoff, what action provides an automatic spoiler function for RTO?
1+ 3 near idle
2 or 4 to reverse idle
For go-around protection, what action drives the speedbreak lever to the DN position?
thrust lever 1 or 3 advanced from idle
Which elevator panels are displayed on the Surface Position Indicator?
outboard
What can you do if you lose elevator control due to a jam?
significant manual force to override (shearouts)
Describe the elevator feel system
- feel and centering mechanism provides artificial feel at control columns - force increases with speed
- hyd 2/3 power mechanism - loss of one does not affect feel forces
- if both fail, mechanical springs provide feel forces (no longer function of airspeed)
How does the aileron lockout system work, and what is its purpose?
locks outboard ailerons in neutral position at 238 kts, allows full control below
What would happen if you use aileron trim with the autopilot engaged?
forbidden - moves aileron neutral point, so when disengaged could cause abrupt roll input
How do the rudder ratio changers work?
2 rudder ratio changers gradually reduce each rudder surface’s response to pedal inputs as airspeed increases
If ratio changer system fails, response will remain the same as at point of failure
- may get too large or too little response
What is the purpose of the yaw dampers?
2 independent yaw dampers improve airplane lateral+directional stability and provide turn coordination
- help prevent dutch roll
Describe the OFF position of the landing gear
depressurizes the landing gear system
How many degrees can the NWS turn the nose gear with the tiller, and how many degrees with the rudder pedals?
70 deg
7 deg
When does RTO apply maximum brake pressure?
when thrust levers retarded to idle > 85 kts
What does the BRAKE SOURCE amber light indicate when illuminated?
active brake hydraulic sources (hyd systems 4, 1 and 2) have low pressure
(if you have pressure in any of the above you will not get this light)
What does a white, crosshatched, expanded gear position indication mean?
gear in transit
What does amber x expanded gear position indication mean?
gear position indicators inop
What does a white empty box on gear synoptic display indicate?
All landing gear position indicators inoperative
What sensing systems control in flight and ground operation of various airplane systems?
air/ground sensing system and nose gear extension sensing system
How does the airplane distinguish between air mode and ground mode?
air mode = main gear tilt sensors indicate gear tilted ground mode - not tilted
Nose gear extension sensing provides a signal to relays controlling functions in which systems?
stall warning and nose gear steering
What conditions must be satisfied on order for the landing gear lever lock to release?
- prevents OFF to UP on ground, can be manually overridden by push/hold landing gear lever lock override switch
- lever lock released in flight when main gear tilted and body gear centred
(all four main gear hydraulically tilt as airplane lifts off. landing ground load brings gear to level position)
Describe the sequence of events when the landing gear lever is moved UP?
- gear door open
- automatic braking occurs - gear begins to retract - EICAS position changes from green DOWN to white crosshatch in-transit indication
How are the landing gear held in the UP position after retraction?
- uplocks - nose gear mechanically
- UP on EICAS for 10 secs
-lever OFF depressuirzes system
During landing gear extension or retraction, state what happens if any gear position disagrees with lever position after normal transit time?
EICAS gear position indication changes to expanded non-normal format - affected gear displayed as in transit (or up/down if never unlocked)
GEAR disagree checklist
How does the gear extend through the alternate gear extension system?
- Gear uplocks and door latches electrically released
- gear allowed to free fall with gravity
- gravity and airloads extend gear
- springs pull downlocks into locked position
When does body gear steering operate?
- When nose wheel steering > 20degrees
- Activated when ground speed decreases < 15 kts
(Deactivated when increasing > 20kts)
When is body gear steering deactivated?
As ground speed increases > 20kts due to centering
What is the purpose of the brake accumulator?
The brake accumulator provides for parking brake application
Describe the difference between normal and alternate anti-skid braking systems?
Normal - each main gear wheel’s speed sensor detects skid, associated antiskid valve reduces brake pressure on that individual wheel.
Alternate - works on lateral wheel pairs, not individual wheels
How does the brake torque limiter function in the Alternate brake system?
Each wheel has a brake torque sensor.
When excessive torque sensed, signal sent to antiskid valve to release brake pressure.
In alternate brakes, antiskid valve releases brake pressure on lateral wheel pair
When do the auto brakes apply after landing?
- all thrust levers closed
- ground mode sensed
- wheels have spun up
Which systems contribute to total airplane deceleration on landing?
Brakes
Thrust reversers
Spoilers
Give examples of what would disarm the autobrakes after landing?
- pedal braking applied
- any Thrust lever advanced after landing
- Speedbrake lever moved to DOWN detent after speedbrakes have deployed on the ground
- DISARM or OFF position selected on Autobrakes selector
- autobrake fault
- normal antiskid system fault
- loss of normal brake hydraulic pressure
What hydraulic system pressurizes the brake accumulator?
4
Can the airplane be stopped with normal accumulator pressure?
No
Why is it necessary to pressurize hydraulic system 4 before pressurizing the other systems?
- when parking brake set, first hydraulic system pressurized may supply a small amount of fluid to the brake lines
- when brakes released, that fluid returns to hyd system 4
- so pressurizing hyd 4 first avoids sys 1 or 2 hyd fluid transferring into system 4
What provides automatic brake source selection?
AUTOBRAKES Selector
- normal brakes and antiskid systems must be functioning
