Originally Posted by
AF330
So if rudder trim is never used during long turns (AP engaged scenario), when would AP decide to apply rudder trim (of course, except engine failure..)? Is there any flight phase during normal operations where AP asks for Rudder Trim? Maybe cruise? Or on short final in windy conditions?
Thanks.
AF330, I think there is a bit of confusion about terminology; perhaps what you have in mind is the
yaw damping function, that is
always active:
Yaw damping stabilizes the aircraft in yaw and coordinates its turns.
In automatic flight (AP engaged) during takeoff and go around, it assists rudder application after an engine failure (short-term yaw compensation).
Note: When the AP is engaged, the FMGS sends orders to the FAC to give :
- Yaw damping during approach
- Yaw control for runway alignment in ROLL OUT mode
How?
through the rudder trim:
The rudder trim function :
- Executes trim orders, entered by the pilot by using the manual trim knob.
- When AP is engaged
executes trim orders from the FMGS.
Assists the system in recovering from engine failure (long-term yaw compensation) in all flight guidance modes.
If the pilot pushes the rudder more than 10 ° out of trim, it disengages the AP.
Note: When the AP is engaged, the rudder trim knob is inoperative : the master FMGC sends rudder trim orders to the FAC.
Ref: FCOM DSC 22_40-20 yaw function
I hope it helps.