Walter
The strength of the Boeing analysis is that, on that final leg, there was insufficient time (as they were already pretty much on their top cruising speed) to have done much significant maneuvering prior to that final flare other than to have kept to track;
What ;available data' was 'analysed' to divine the aircraft's cruising speed? The non existant FDR?
Why it turned right is never going to be known beyond doubt, and that is why the finding is wrong.
IF they were that close to the high ground, and barrreling towards it relying on a piece of kit (which would have been less accurate than the on board TANS), to give them a DME countdown to the WP, then it's game set and match to Wratten and Day. That would have broken all the rules of VFR flight.
I'm with Tandem. This fanciful pursuit of the most unlikely use of a device no british military helicopter pilot has ever heard of is an unhelpful distraction. Furthermore, its use would have been totally negligent at the level being flown at. Please drop it.
BTW, back to TANS, (and Walter, the GPS and Doppler sides are separate. Poor doppler sea returns woulld have no effect on its sattelite accuracy) are we certain that it was in 'tactical steer' mode. In 'Route steer' mode, the waypoint change would have been automatic.