Primary Flight Controls
– Ailerons and the multi function spoilers for roll axis control.
– Elevators for pitch axis control.
– Rudder for yaw axis control.
Secondary Flight Controls
– Horizontal stabilizer.
– Flaps and Slats.
– The multi-function spoiler (when used as speed brakes or ground spoilers).
– Dedicated ground spoilers.
Pitch Trim switch limits
- Manual PITCH TRIM Switch commands limited to 3s
- actuating 1/2 of the switch for more than 7s deactivates the switch
Fly-By-Wire Components
9 x Actuator Control Electronics (ACEs) – Three Primary-ACEs (P-ACE) – Two Slat/Flap ACEs (SF-ACE) – One Horizontal Stabilizer ACE (HS-ACE) – Three Spoiler ACEs (S-ACE)
4 x Flight Control Modules (FCMs)
Function of Primary Actuator Control Electronics (P-ACEs) x 3
- control rudder and elevator surfaces
- connect control column electrically to control surfaces
- two installed in FWD E-bay; one installed in AFT E-bay
- two channels (one active, one stby)
Function of Slat/Flap Actuator Control Electronics (SF-ACE) x 2
- control the slat and flaps surface
- installed in the middle electronics bay
- two channels one channel for flap and one channel for slat
Function of HORIZONTAL STABILIZER ACTUATOR CONTROL ELECTRONICS (HS-ACE)
- controls the horizontal stabilizer surface
- connect the control column electronically to the control surface
- installed in the aft electronics bay
- two channels that operate in active/standby configuration
- active channel changes daily
Function of SPOILER ACTUATOR CONTROL ELECTRONICS (S-
ACE)
- resides within the FCMs and is used to control the multifunction spoilers (3 per wing)
- FCM #1, FCM #3 and FCM #4 have wiring to control spoilers
Function of Flight Control Modules (FCMs)
- provide software-based assistance to the P-ACE
- required for normal-mode operation of the flight controls system
- provide Angle of Attack limiting to P-ACEs
- FCM #1 and #2 located in MAU #1
- FCM #3 and #4 located in MAU #3
Functions provided in Normal Mode
– Elevator control laws scheduling – Auto-thrust compensation – Angle-of-Attack (AOA) limiting – Rudder airspeed gain scheduling – Yaw damper and turn coordination via AFCS – Rudder flight authority – Roll spoiler scheduling with airspeed and speedbrake deployment. – Mach Trim - Configuration change compensation
Operation in Direct Mode
- result of loss of data from FCM
- Operation is defaulted to fixed control laws configuration.
- Control input provided by Captain and First Officer’s sensors is sent directly to the surface
Elevator Control Operation
- 4 X P-ACE channels controls independent PCU
- P-ACE 1 ch 1 —> left outboard elevator
- P-ACE 2 ch1 —> left inboard elevator
- P-ACE 2 ch2 —> right inboard elevator
- P-ACE 3 ch1 —> right outboard elevator
- PCUs hydraulically actuate elevator surfaces
- HYD Sys 1 —> left outboard elevator
- HYD Sys 2 —> left and right inboard elevator
- HYD Sys 3 —> right outboard elevator
Tail Strike Avoidance operation
Takeoff:
- Enabled at altitudes less than 20’
- HAGL (height above ground level) calculated by means of vertical speed
Landing:
- Enabled at altitudes less than 70’
- HAGL calculated by two radio altimeters
Go Around:
- Elevator command authority the same as takeoff config
- HAGL calculated by two radio altimeters
What happens to the elevators what the FCMs are removed from the control loop?
- systems automatically reverts to Direct Mode
- fixed control law configuration
- AP no longer avail
How is the Horizontal Stab commanded
- electromechanical system
- manually via trim switches (LH, RH, Backup)
- switches —> HS-ACE —> HSA
- automatically via FCM
- FCM —> HS-ACE —> HSA
What drives the horizontal stabilizer
- HSA (horizontal stabilizer actuator)
- two dc motors (active/standby)
Horizontal Stab Priority Logic
- Backup switch
- LH Switch
- RH Switch
- FCM (autopilot)
Roll control
- conventional ailerons
- fly-by-wire multifunction spoilers
- Hydraulic System 2: left & right inboard PCU.
- Hydraulic System 3: left & right outboard PCU
How many multi-function spoilers
6 panels:
– L3, L4, L5 (left wing) and
– R3, R4, R5 (right wing)
Multifunction Spoiler operational modes
Normal:
FCM provides airspeed gains and control limits to S-ACE
Direct:
Spoilers associated with failed FCM —> Direct mode
Spoilers associated with unaffected FCM —> Normal mode
Rudder Control
Fly-by-wire
- single rudder surface
- electrically commanded, hydraulically actuated
- Two actuators (PCUs) (Upper and Lower)
- Captain —> P-ACE-1 —> Upper actuator (HYD Sys #1)
- FO —> P-ACE-3 —> Lower actuator (HYD Sys #3)
- 2 channels per P-ACE
Rudder control operational modes
Normal:
- FCMs provide high level functions and structural protection
Direct:
- fixed speed gain (Low-speed or High-Speed)
- depends on flap position
How many Slats and Flaps
- 8 Leading edge slats (four per wing)
- 4 double slotted flaps (two per wing)
- slats extend first
- flaps retract first
Slat/Flap System components
- commanded by two SF-ACE (dual channel units)
- one channel for slats; one channel for flaps
- 2 x PDU (Power Drive Units)
- Slat PDU and Flap PDU
- 2 actuators per Flap Pane (4 per side)
