Firstly this sytem DOES have automatic trim. It is operational all of the time and it's purpose is to sychronise (Keep Centre) the Primary AFCS (Automatic Flight Control System) servos. The position of which is displayed on the 'Galvinometers' on the instrument panel. The Galvinometers should be centred at all times! and indicate the position of the relevant servo.
If they do not centre then the AFCS is Un Serviceable. This is normally due to a failed trim system (Fuse is a good one because the airframes guy has put the wrong size fuse in ). However it is usually due to flight crew not knowing what the trim release switch does and that they have inadvertantly selected it to OFF . It could also be due to a stuck servo (Nothing that a tap with a hammer by your friendly local airframes engineer won't sort out. Well, at least for a few flying hours or so....)
avionicsbloke,
This is exactly my point, because if what you are saying is correct, and the autotrim should keep the galvinometers centred all the time, then I shouldn't have to re-centre them manually all the time by pressing the cyclic trim release. I will have a word about this with our avionics bloke to see if there is a fault in the system. (Which wouldn't surprise me as there was a very serious fault with the A/P when the helicopter was delivered, which took ages, and a new FDC to solve eventualy, and after I had got a few more grey hairs trying to recover from UA's while IMC!) I understand about switching the trim release off on the OHP of in the event of a runaway etc.
BC