A320 Permanent Offset of Rudder Trim

[Field In Sight]

A mate asked me the following question and I couldn't answer it.

FCOM 3.04.27 p12

Acft in cruise, balanced fuel, equal thrust. A/P engaged.

"Rudder Trim Indication should stay within 1 degree right and 2.3 degrees left." i.e. not symmetrical.

The note says that the "the permanent offset of rudder trim indication" average 0.5 degree right and 0.8 degree left. Note "rudder trim indication" not deflection.

It also says that the real rudder deflection shouldn't exceed 1.5 degrees left or right.

I can understand that on average a real rudder deflection could exist due to lateral inbalance, but not an average indication error.

It is probably just a typical Airbus translation, but I'm waiting to be enlightened.

Cheers,

FIS

[pakeha-boy]

FIS... yeah mate,have seen that written and would agree with it up to a certain point....also converting the french explanation into Enlish doesnt always seem to come out the way it should.

Have flown the 319/320 and now currently the 321.... our taxi checklists make us reset the rudder trim to zero,which is done on the taxi...but on all A/C...I have noticed that when you set it at zero,it almost always resets itself to 0.1-0.2 ...never stays a zero.

The explanation that I have recieved for this is that based up your config....ie flap setting,final wt and others the FAC,s which control..
-roll normal
-rudder trim
-rudder travel unit
-yaw alternate

reset the rudder for T/O...even though on take off you are manually using the rudder pedals for steering.....the question asked would be ..so what difference does it make......the difference is in making sure the FAC,S are giving correct info to the rudder once the autopilot is engaged and also for auto landings.....

I would have to agree with the explanation....hope this helps...PB