Cazatou
<<… with the greatest dispatch, coupled with the minimum exposure to potential hostile action. I know of no person who has suggested otherwise >>
Actually, many years ago I had suggested that it would have been for such tactical considerations that they would have been approaching the landmass fast and low (the hills muffling their approach) and turning so as to go along the coast very close to the mist (which was to be expected on the landmass slopes and which would prevent anyone on the land from seeing them coming for more than a fleeting moment so that they could not be targetted).
You said:<< I know of no person who has suggested otherwise >> Guess what? – this suggestion was ridiculed strongly by many – I am glad that you at least now appreciate the possibility.
.
Further, this was, I believe, a routine tactic for any mil helo coming over from NI when the local mist conditions afforded this protection – I and the lighthouse keeper witnessed one do it in near identical conditions and he told me that they did that all the time.. This contrasts with your view: << Whether it was appropriate to continue with that course of action as they approached the fog enshrouded Mull is another matter.>> - I say it was a more likely course of action when there was the common ground hugging mist there.
.
If they were relying upon visual judgment only for their distance off that mist, they would have to have been prudent – the ground detail of the general slopes would have been blurred to say the least – I cannot imagine that an experienced crew like them would have carried on at (cruising) speed, as I have explained so many times before, without either clear sight of a familiar feature (in which case they would have turned in time) or were referring to something else for their range to go.
Confusion between the fog signal station and the lighthouse has been suggested: however, if you plot their approach track, the lighthouse, and the fog signal station on a 1:50,000 OS map, you will see that, at their (very oblique) approach angle, such a confusion would have only put them tens of metres to the right – not hundreds as suggested.
There was no pressing need, for the above mentioned tactical considerations, for them to approach the mist at a precise point if they had no clear visual reference – as an experienced pilot familiar with the area posted here some time ago, they merely had to start turning gradually left to line up with the shoreline/ edge of mist in the distance when they were feeling uncomfortable with their judgment of proximity or, I add, when they had reached close in according to their SuperTANS (with a margin for error). That they did not suggests some specific reason for approaching more closely and this is reinforced with the steer to the RIGHT at waypoint change.