-
FMGC 1 and Capt PFD normally use data from FAC 1

 -
FMGC 2 and F/O PFD normally use data from FAC 2
 In the event of failure, the FMGCs and the PFDs use the data from
 the active FAC.

 (2)
 Yaw damper
 The yaw damper function provides:

 -manual yaw stabilization. The ELACs compute the corresponding data and transmit them to the rudder surface via the servo loop of the yaw damper (FAC).
 -alternate law for Dutch roll damping when the ELAC no longer computes normal yaw stabilization.
 -Dutch roll damping (including turn coordination) when the autopilot is engaged in cruise only.
 -engine failure recovery when the autopilot is engaged (the ELACs provide this function in manual flight).

 (3)
 Rudder trim The rudder trim function provides:

 -manual control via a rudder trim control switch located on the center pedestal. In addition the ELACs compute a command signal for rudder deflection (normal yaw damping law including recovery of engine failure) performed by the trim sub-system in manual flight. Reset of the rudder trim position is possible using a pushbutton switch located on the center pedestal.
 -automatic control when the autopilot is engaged which provides the accomplishment of yaw autopilot command and the recovery of engine failure.

 (4)
 Rudder travel limitation This function provides the limitation of the rudder travel by displacement of a stop as a function of the speed.

 (5)
 Monitoring of flight envelope and computation of maneuvering speed This function provides the Primary Flight Display (PFD) with the following data displayed on the speed scale: (Ref. Fig. 006)

 -stall warning speed (VSW)
 -lower selectable speed (VLS)
 -
maximum speed (V MAX)

 -
maximum operational speed (V MAX OP) giving margin against
 buffeting

 -airspeed tendency (VC TREND)
 -maneuvering speed (V MAN) function of the flap and slat positions
 -
minimum flap retraction speed (V3)

 -
minimum slat retraction speed (V4)

 -predictive VFE at next flap/slat position (V FEN)
 In addition :

 -V MAX and VLS are used in the FMGC for speed limitation of AP/FD and A/THR functions
 -The FAC computes the conditions of activation of the alpha floor mode of the A/THR functions (angle of attack protection in case of windshear).

 (6)
 Windshear detection (optional)

 (7)
 Low energy detection

 Display of the FAC Data on the Speed Scale of the PFD Figure 006

 (8) BITE function of the system The FAC 1 performs BITE function of the whole AFS/FMS. Each computer includes its own BITE function and is linked to the FAC
 1.
 The MCDU (linked to the CFDIU) displays the content of the
 maintenance data.

 B. Flight Management and Guidance System (FMGS)
 (1) General
 (a)
 Functions
 The FMGS performs the functions given below:

 -autopilot (AP)
 -flight director (FD)
 -autothrust (A/THR)
 -flight management which includes navigation, performance and processing of displays.

 (b)
 Operating principles The FMGS is a dual-dual type system for the autopilot and autothrust functions. In cruise mode only one autopilot can be engaged. Both APs can be engaged (through the AP1 and AP2 pushbutton switches located on the FCU) as soon as ILS approach mode is selected. AP1 has priority, AP2 is in standby (the ELACs and the FACs use the AP1 commands first and switch on the AP2 command in case of AP1 disengagement). A single A/THR pushbutton switch located on the FCU enables engagement of the autothrust function. Both A/THRs are always engaged at the same time but only one (A/THR 1 or A/THR 2) is active depending on AP and FD engagement statuses.

 -----------------------------------------------------------| ENGAGEMENT OF AP | ENGAGEMENT OF FD | A/THR ACTIVE | |---------|---------|---------|---------| | | 1 | 2 | 1 | 2 | | |---------|---------|---------|---------|-----------------| | ON |ON or OFF|ON or OFF|ON or OFF| A/THR 1 | |---------|---------|---------|---------|-----------------| | OFF | ON |ON or OFF|ON or OFF| A/THR 2 | |---------|---------|---------|---------|-----------------| | OFF | OFF | ON |ON or OFF| A/THR 1 | |---------|---------|---------|---------|-----------------| | OFF | OFF | OFF | ON | A/THR 2 | |---------|---------|---------|---------|-----------------| | OFF | OFF | OFF | OFF | A/THR 1 | | | | | | (OR A/THR 2 IF | | | | | | A/THR 1 FAIL) | ----------------------------------------------------------- The flight director is active when the aircraft electrical network is energized. Then associated FD pushbutton switches on CAPT and F/O EFIS control sections come on. The FMGC 1 normally drives the FD symbols (crossed bars or yaw bar or flight path director symbols) on Capt PFD and the FMGC 2 normally drives the FD symbols on F/O PFD. In case of the failure of one FMGC, the remaining FMGC drives the FD symbols on both PFDs. (Ref. Fig. 007)
　
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