Way back in the thread I think it was megan who posted a link to a Mallard flight manual. For all the Popular mechanic theorists arguing about downwind turns have a look at the procedures for landing and where the flaps should be. Also interesting is the intial approach speed and the final approach speed with the flaps down. If he forgot to put the flaps down and then tried to fly at the recommended final approach speed then the crash was inevitable. No extraordinary theory of physics required, just look at the evidence.