dervish
At least you have some knowledge of that weather; may I recommend you try and recall the wind, time of day, etc that gave rise to it? Further, find out just how prevalent it is. Then borrow a boat (cheaper than an a/c) and view it from off-shore on a summer evening with similar conditions forecast. Compare what you see to the accounts from witnesses on the day. Then perhaps you may understand that the view they most likely had presented the problem of range judgement I described – they would have been aware of the immediate presence of the Mull but would have had a problem approaching a particular point on the shoreline at speed.
Tuc
<<One need only recall Flt Lt Tapper took the extraordinary step of visiting a Design Authority to discuss RNS252 because the information he had wasn't good enough.>>
Flt Lt Tapper's concerns were not limited to documentation, were they? Did he not express concerns to others in his flight as to the accuracy of the system? I have made the point many times that he would not have trusted it as close in as waypoint change to keep them from bumping into the Mull at speed – he would not have entrusted the steer data (the system using combined Doppler and GPS data) to guide the HP to waypoint A closely enough for the start of their swing around the light house – he would not have been alarmed at a discrepancy between this steer data and data from a local reference (such as CPLS data to a PRC112 at the LZ at waypoint A) and would surely have preferred the latter.
dervish et al
The whole of the available data is consistent with a planned approach to a particular point;
the LZ (with which this crew was familiar) was a good point to start a swing around the light house, given the practical range of turning radii of a Chinook at cruise speed;
from a distance, this LZ was represented by waypoint A in the STANS and, had they continued to use this system, they would have crossed the shoreline at waypoint A/the LZ, having kept on a track of 027;
close in, they changed waypoints in the STANS consistent with the NHP's course selector so as to define the route H-B, the 028 track that handrailed along the coast of Islay/Jura – a logical route to head for after turning at the Mull given that that coast was clear weatherwise but that north on the Mull was not;
the nearest shore to this point (waypoint change) was only about 600 metres away;
the a/c then followed a track of 035 to the area of the crash – that the turn onto this track was deliberate is evidenced by the HP's course selector being found set on this (without a clear visual cue ahead, it would have helped him stick to his course) and that the engines were found to have been matched at an intermediate level (a steady state consistent with coasting along and not indicating any manoeuvring);
the above suggests a change in reference from the STANS to a local reference at this point;
their right turn at waypoint change took them towards higher ground with no safe wave-off option;
the data preserved by the impact (controls and engine state, etc) pointed to a sudden awareness at their immediate proximity to the ground – they must have been misled as to their distance to go;
their actions are fully explained by that local reference being out of the position that they were expecting it to be at (waypoint A/LZ) – whether this was due to an error in an exercise or due to a wilful act needs to be investigated – the latter cannot be lightly discounted because of the security team on board who were effectively an obstacle to the peace process.
I trust that you may find this explanation more plausible than an a/c fault (for which there is no evidence and in an a/c type that has completed so many hours successfully) coming into play just as they were approaching a spot where my suggested scenario fits so well.