FIGHT CONTROLS Flashcards
How many operating modes are there for the primary flight controls?
3
Normal mode
Secondary mode
Direct mode
Describe the FLT CTRL operating schematic?
Control sends an analog signal to the ACE
ACE(Actuator Control Electronics) converts this to a digital signal and sends it to the PFC(Primary Flight Computers)
The PFCs send a signal back to the ACE which converts them back into analog and sends them to the PCU(Power Control Unit)
PCUs gives the power to operate the flight controls
What are the inputs to the PFCs?
Airspeed
Inertial data
AOA
Flaps positon
How are the primary flight controls powered?
By redundant HYD sources
How are the flight controls powered?
PCU drives the pirmary flight controls
Which controls have jam override mechanisms?
Control columns and wheels
Which controls are ridgidly connected to each other?
The rudder pedals
How many ACEs and PFCs are there in the flight control system?
4 ACEs
3 PFCs
Why do the PFCs receive other data inputs?
To compute control surface commands for improved handling characteristics
How do autopilot commands cause control surface movement?
Sends commands to the PFCs
Which control surfaces provides Roll control?
14 spoilers
2 ailerons
2 Flaperons
Which control surfaces provides Pitch control?
Elevators
THS
Which fight controls provides yaw control?
Dual surface hinged rudder
When do the aileron droop, and why?
With flaps 5, 15 and 20 selections to improve take-off performance
When and how does the flaperons droop?
Move down and aft in proportion to trailing edge flap extension
What are the flaperons used for?
In normal mode for roll control but also for increased lift
What are the 3 protection features?
1 Stall protection
2 Overspeed protection
3. Bank angle protection
What functions work in Normal mode?
Auto spd brake
Auto pilots
All 3 protections
PFCs and ACEs
When does the system switch to Secondary mode?
If airspeed and/or inertial data is lost
What functions are lost in Secondary mode?
All 3 protections
Auto spd brake
Auto pilot
Yaw damping is lost or degraded
Are the PFCs and ACEs working in secondary mode?
Yes and full manual control is retained
When is Direct mode operative?
Goes to this mode if other failures occur or if the pilot selects DISC for the “Primary Flight Computers” switch.
Are the ACEs and PFCs working in Direct mode?
ACEs are working. Sends signals direct to the PCU and skips the use of the PFCs
Which HYD systems powers the elevator?
Left Center and Right
Describe stall warning system?
There is a stick shaker but no aural warning.
Top of amber band is the manouvering speed and is the lowest speed the aircraft can be trimmed to. In the amber band a caution “AIRSPEED LOW” comes up on EICAS
If A/T is armed it will automatically engage in the amber band
Which HYD systems powers the THS?
Center and Right HYD systems
What are the inputs to the stabilizer green band indicator?
CG
T/O thrust
Gross weight
Which FMC page displays trim settings?
T/O REF 1/2
How is the calculated stabilizer green band double checked for accuracy?
By a nose gear oleo pressure switch that double checks the CG
What does the EICAS message “STAB GREEN BAND” mean and what could be the problem?
The nose gear x-check function disagrees with greenband calculation
Problem can be incorrect entry into FMC
Does the control wheel pitch trim work when the autopilot is engaged?
No, it is inhibited
With no autopilot engaged, when is pitch trim necessary?
Only when airspeed is changed
Describe how pitch trim is achieved in flight
1 Set speed on MCP, that sends info to the PFCs to change trim reference speed
2 PFCs send signal to ACEs to position the elevators via the PCU
3 Stab moves to the required position
4 Elevators streamline with stabilizer
How much does the trim reference speed change when the trim switch is operated?
Approximately 10 kts/second
On the ground, what are the trim switches on the control wheel used for?
Directly positioning the stabilizer
What surface do the primary pitch trim switches move in flight?
The elevators via the PFCs-ACEs and the PCU
Which surfaces have cable driven back-up?
Stabilizer and spoilers 4 and 11
When will trim in the nose up direction be inhibited?
When close to the manouvre margin speed
When will overspeed protection occur?
At Vmo or Mmo
How many levels on elevator feel exists in Secondary and Direct mode?
- Control column force is lower with flaps extended
Which spoiler surfaces are mechanically controlled?
4 an 11
What does the Alt pitch trim lever do?
Moves cables that controls the THS dirctly in all modes. Levers are spring loaded to neutral
Can the Alternate Pitch trim be used when autopilot is engaged?
Yes
Describe tail strike protection?
The PFCs calculates the rotation rate and decreases elevator deflection if needed
When do control column forces increase?
When airspeed increases, in Normal mode
How are control column commands changed in secondary and direct mode?
Control column now commands a proportional elevator deflection instead of a manoeuvre command
What happens is one control column jams?
Applying force on the other control wheel overrides the jam