John Purdey, Again you make many assumptions, not least that the aircraft was functioning normally. Again, there were at least three possible unserviceabilities that could have caused this accident and could not be discounted as the cause.
A. Engine runaway to high power. It does happen I've had this happen myself, not too long ago, albeit not in a Chinook but in another more modern type with DECU controlled engines. The failure was not practiced in the simulator because it had reportedly not happened before and in any case it was supposed to be impossible because of the logic of the sytem. It was not possible to programme the simulator to make it happen; I later tried to practice this but was told it wasn't possible to do so. The aircraft manufacturer could not find the reason why this occurred. We were close to the ground, in the hover and we were able to deal with it. In a situation of forward flight under a low cloudbase, it would have been much more difficult to deal with. There is so much evidene of this happening to the Mk2 Chinook, it doesn't need posting here again.
B. Control pallet failure. Found detached in the wreckage. Real evidence but not conclusive. Another Chinook had previously suffered this failure, which occurred due to a poor design feature. If the aircraft controls failed, the pilots would have had little choice about subsequent events.
C. Nav system inaccuracy. Evidence of previously reported on this airframe, but no fault found and aircraft continued in service with no rectification having been carried out.
D. The actual post accident evidence of the co-pilot's intercom selected to the emergency position indicated that the crew had a problem in communicating with each other across the cockpit. This is a danger in itself when the non flying pilot does the navigation but in an emergency situation (either of the above A, B or C. or others not discovered) it could well have been the straw that broke the camel's back.