Pulse1
You wrote:
<<** wk, if you are suggesting that the crew of ZD576 deliberately flew 25 passengers into IMC below MSA with two conflicting navaids, you are indeed suggesting gross negligence, in my view.>>
I think that if you read past posts you will find that I have consistently made the points, in my opinion, that:
they never intended to enter the mist/IMC;
they entered it because, for whatever reason, they misjudged their distance from it;
it is very difficult to visually judge one’s distance from a headland shrouded in mist;
the crux of the matter is, that while it is the responsibility of the crew in a VFR flight to ensure that collision avoidance can be effective relying upon the eyes only, I believe that I have previously described well enough how an available reading on a trusted instrument could bias one’s judgment to agree with that reading;
had they no other nav aid other than SuperTANS (of which this crew was aware of its inherent inaccuracies after a sea crossing), they should indeed have been prudent in their approach to the turning point.
If it were the case that they thought, for whatever reason, that they were further away from the landmass than they actually were we may be able to quantify the size of their error by making an assumption about their reason for being in cruise climb:
Had they started the climb ½ to 1 mile further out, they would have been about 1000ft at the actual position of waypoint A – which would have put them in (radio) line of sight with the Macrihanish TACAN/DME (do a transaction on an OS map between waypoint A and the Mac aerodrome) to which their TACAN CU was set (ch107) – their heading put waypoint A and the MAC navaid approximately in line ahead which would have given them an accurate fix at that point; one would assume that there would have been no reason to get so accurately to waypoint A just to turn up the coast on a ferry flight – perhaps they were verifying the accuracy of another system that was supposed to be at waypoint A and which had misled them (by being ½ to 1 mile further up the hill)?
(Cruise climb in this case had nothing to do with an intention to go over the Mull as it would have had to have been initiated miles before it was to get to the safe altitude.)
Regarding the recent debate on speed, on a ferry flight in good VFR conditions the speed of ZD576 was entirely appropriate, was it not? They could hardly be expected to slow down in the vicinity of that mist which was FIXED ON THE LANDMASS provided that they believed that they could turn away from it – if there was no obligation to go to a specific, close in point there would have been no need to go so close as to require (for prudence, good airmanship, and staying within the guidelines for helos at low level) a reduction in speed – it only makes sense if they were required to go over a specific point which they believed was before the start of the mist.