Here's what the service manual has to say:
http://web.bethere.co.uk/andy.reid/s...manual%202.tif
http://web.bethere.co.uk/andy.reid/service%20manual.tif
For our aircraft it would appear to be every 5 years. For later models its on condition.
Also, we would appear to be dealing with the CAA's (rather hardline?) interpretations of EASA rules. So it may be different in other jurastications ?
What's really
me off is that this has come right out of the blue. If our service organisation had prewarned us of this then we could have planned around it. It now looks like the aircraft is going to be offline at the time of the year when we least want.