Tyre Question
 

Sorry for my ignorance but it has been awhile since I did my apprentice training and being around helicopters with slabs of metal underneath I have forgotten.

What is the usual reasons for a tyre to be U/S, is it the showing of the first ply?

Carcass showing,sidewall damage,FOD,underinflated(also underinflated tyre on opposite/adjacent axle,flat spots,thermal blowout,tie rods broken/missing(refer to MEL on this one for amounts) any other anyone??

worn to limits can be another,depends who sees that!!!

wear and cuts are the normal reasons for change. You need to check your MM or Tyre manual, the first chord showing may be wear chord or carcuss. Wear chord may not be an immediate problem depending on where the a/c is, carcuss is a problem.

Dunlop Aircraft Tyres Limited - Tyre Care Manual

Good reading, in answer to your question, it seems if the tyre is retreadable, then, yes change it.

Once had cause to fly on an IL76TD freighter (long story, but a money earning down router) and a number of the tyres appeared to be worn beyond the first few canvas layers.
I discussed this with the crew and asked "When do the tyres get changed?" "When they burst!" was the straight and to the point answer:hmm:

This isn't As I See It, or for many others I'd guess