Re: Airbus trim system?

Date:         26 Jul 98 23:57:21 
From:         Pete Mellor <>
References:   1
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In article <airliners.1998.983@ohare.Chicago.COM>,
  Scott Macmillan <> wrote:
> Hello folks,  I was watching one of those 'in the cockpit' videos
> the other day that featured the Airbus A320.  During the video I could
> see the trim wheel moving back and forward of its own accord.

Sitting in the jump seat of an A321 a couple of weeks ago,
I noticed that the trim wheels seemed pretty active. The
captain said that it was quite normal, as the auto-trim
continually adjusts for slight movements of CoG as the drinks
trolley moves backwards and forwards along the cabin, or
passengers go to the toilet (to name but two causes).

In a normal flight, after they have set the initial trim on the
ground prior to take-off, the crew never touch the trim wheels.
The only exception that I am aware of is in the case of complete
loss of the flight control system, when the manual adjustment of
of the horizontal stabiliser via the trim wheels becomes the only
means of controlling pitch. (This has never occurred on a scheduled

Peter Mellor, Centre for Software Reliability, City University, Northampton
Square, London EC1V 0HB, UK. Tel: +44 (171) 477-8422, Fax: +44 (171) 477-8585
E-mail:, Web: