Arkroyal,
Apologies for the delay in replying, its the time of year when we get lots of visitors.
The HOL Commitee accepted that, when the crew selected the waypoint change at a computed 0.81NM from the (misplotted) lighthouse (and 0.95NM from impact), they were not experiencing any significant difficulty in handling the aircraft in view of the fact that such a change required 3 seperate, and deliberate, actions by the pilots. The pilots failed, however, to make the relatively small course correction of some 7 degrees demanded by their navigation equipment.
The average groundspeed from the ATC fix on leaving the Aldergrove CTZ at 16:46:24 to initial impact power-down time of 16:59:36 was 158 kts. AAIB concluded that groundspeed at impact was "of the order of 150 kts". The assessment by Boeing, using the last steering command 0.75 secs before impact, gave an aircraft groundspeed of 162.8 kts. Finally the "distance to go"(86.63nm) and "time to go"(32.8 min) to the selected waypoint of Corran gives a groundspeed of 158.5 kts towards that point.
All of these calculations show a remarkable similarity, the slightly lower speed assessment at impact by AAIB being attributable to the final desperate flare.
IF there was a control problem after waypoint change, why was there no "emergency squawk" or distress call? Waypoint change was some 21 seconds before impact. If there was no control problem at waypoint change, then why did they continue towards the cloud covered high ground at high speed instead of making the small course change demanded?