Just to add to the collapse/rebound pipe work theory stated above. If this did happen, maybe there is some evidence such as some small remaining distortion, or paint or other coating with tiny wrinkles or fractures. I'd think you'd have to go looking for this kind of evidence though, to find it.
I also think this theory could explain all facts to date as we (Ppruners) know them, but the evidence of a pipe work collapse/rebound would have to be there to confirm it.
Last edited by Flight Safety; 13th May 2008 at 20:04.