Acoustic panel:
Aft of the fan attrition liner, are honeycombe panels which on pre sb engines there were 9 of them that were bonded onto the fan case with additional bolts for security, over time they would suffer from disbond due to their being too rigid and start to break up losing the top skin and damaging the the underlying honeycombe. The fix was for 'bluefill'. (which compromised the acoustic properties... thats the bit FOCAL has been hinting at
) The later post mod panels are 1/3rd the size and bonded in with BMS5-95 which is flexible. I've only seen a couple of the post mod panels replaced and that was due to impact damage (bird strike).
Not seen a cracked OGV for years.
The T/R can be a pain (designed by Nordam I think)
AFAIK we have incorporated the mods and SB's for the sense pipes etc at overhaul so sense line failure thankfully is thing of the past. But! they tried to be clever and it's all prox. switches, what's wrong with a good old fashioned mechanical micro switch? that would have cured 99% of T/R problems.
Other than that they stay on wing for a long time and suffer little in the way of performance degradation over the life of the engine.
And the best thing from a maintenance point of view they are sooooo simple to work on!
