While I was going through the analysis, final check, it struck me that many of you had perhaps not plotted the data on a big chart nor paced out the positions at the actual site (with a hand held GPS) and so may not be grasping the scale of the area on the Mull at and approaching the crash site – because one fundamental and relevant aspect would have been obvious to you had you done so, as I will attempt to explain briefly below:
Take the position where the waypoint was changed as that in the SuperTANS (AAIB deduced from position data at impact that STANS had been accurate in latter part of flight);
Accept Boeing's analysis that a turn to the right was made at that point;
Remember that a course setting of 035 was found set on the handling pilot's Horizontal Situation Indicator (HSI) – this of course meant a magnetic course and if you want to plot this on a map now you must use the magnetic variation appropriate at the time in that area;
Accept that waypoint A just happened to be on the threshold of a known landing spot for Chinooks on exercise – an obvious inner marker;
Accept that they were in clear air over the sea and the mist & cloud of concern was on the landmass affecting their sense of orientation from topography and blurring ground details past the shoreline making judgment of distance off the landmass the issue.
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The final evasive manoeuvre did not start until the final few seconds – Boeing's analysis had it that the a/c had flown a straight track from waypoint change up to this final manoeuvre.
If you draw a line representing 035m from the position of waypoint change on a large map you will be able to see that the initial impact point is only 150 metres off to the left of this track.
Remember that the final evasive manoeuvre involved the a/c turning and slewing to the left but was only enacted in the final few seconds such that any deviation off track would be small and to the left.
Is it not intuitively obvious that the a/c was on 035 until the last few seconds? - the course setting as found on the handling pilot's HSI course selector.
So 035 looks deliberate? - and yet noteables on this site have dismissed it as pure coincidence.
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If you work back from the crash site on 035m, using a ground speed of, say, 150kts, they would have crossed the shoreline at 13 sec before impact;
that is about 9 sec before the final evasive manouevre was initiated.
9s decision time when in low power regime (Boeing's analysis had them slowing down wrt TAS – the increase in wind at the Mull masking this) and perhaps wondering what was going on ...
Remember that the position where they changed the waypoint was already too close in in the prevailing conditions for this crew to have relied upon the STANS to have gotten them there at their cruising speed – despite having been pronounced accurate by AAIB in that part of the flight with hindsight, Flt Lt Tapper would not have trusted it after a sea crossing – and yet they made an intentional turn 8 deg to the right at that point.
There was no more suitable waypoint loaded into the STANS than waypoint A and this they had discarded – so what on earth is there that an experienced helicopter crew could have used as a reference at that point? Something that influenced their judgment more than the STANS and their growing perception of proximity to the landmass – something they trusted to be intrinsically accurate, perhaps – something that if conflicting with their senses could cause 9 seconds worth of hesitancy.