Hi Matty H, I made what you advice me, to comment out,neatly, some parts of code (those most indictable) and seems I find out what was the problem!

(since now no more appcrashes)
I had 260 little darkdynamix shapes inside the airplane, all pressed in a little 3d point.
These shapes are the available debris, ready to splash out from the airplane when it's crashing on the ground (and the effect it's really cool).
I put these DarkDynamix shapes in the same collision group to avoid these can hit each other but sometimes all that causing the appcrash.
Currently I using just 2 DarkDynamix shapes as debris and no more app crashes. I just try to find another way to have hundred of debris flying out from airplane when it crash!