Walter:
Tec&Chug
Either the pilot or an AFCS is continuously moving the controls to keep these (unstable) things straight and level – I would be surprised if a Chinook would have maintained a straight track over the distance of the last leg with even one control jammed – as I would be surprised if the pilot had not waggled controls any which way if he detected a jam which would have caused a/c attitude changes – and perhaps a change of power too.
No doubt the gyrations of which you speak would have been plain to see, Walter. Trouble is there were no eye witnesses, only the "ear witnesses". As has been pointed out the turn could have been made at any time simply to stay clear of the coast and maintaining VMC. Only then would a control jam as proposed by Sqn Ldr Burke have manifested itself. Perhaps your gyrations then ensued, but what change in sound would have made a control problem clear to the ear witnesses?