Thanks Walt,
I didn't have time to trawl the responses to that old post of yours but did anyone come up with why the PF had 035 deg selected on his HSI? It could be important, it might not - Chinook operators please could you tell us what were the SOPs for a VFR LL leg - was it to select the inbound track to the WP on the HSI. Then, what was the sequence of events at a WP change - who said what to whom to set up the HSI for the next leg - or did TANS do it automatically for you? In which case, where DOES 035 deg come from? (was it the track onward from WP B (Corran) to C (Fort George) - indicating an inadvertent error prior to WP change at WP A to select the incorrect leg's QDM or a mis-selection of the QDM to Corran? I am almost sure it wasn't for an LZ - sorry Walt!
I suspect that Walt's old post about unauth'd LZs created a certain amount of 'gnashing of teeth' from all corners but while I disagree with his hypothesis, I don't think he can be proved wrong - not for certain. Certainly, I think it is less likely than either of the negligence or UFCM/Engine fault/distraction theories (that is all they are). Perhaps the biggest argument against Walt's idea is that the ac was still travelling over 130 kts IAS as it approached the LZ - which is not conducive to landing, I should think?
However, he may have highlighted that perhaps the lighthouse was not 'misplotted' 200m SE but that the 'previously used' LZ co-ords were 'commonly' used as a WP (did 1 Gp SH/SF have a list of approved LZs with LZ recces/co-ords/elevations/obstacles etc etc -if so, was there one for Mull lighthouse?). This slight 'misplotting' could have contributed to the visual illusions below cloud, approaching the land - adding further to the debate as to why didn't they turn left.
Nonetheless, using the slightly incorrect co-ords for the lighthouse (WP A) is not a major factor for navigation either way (BOI agrees), However, this might have slightly mislead the crew!
If they thought they were 'on track' (027deg) from BFS to the lighthouse, then actually, they would have been tracking slightly to the right of the lighthouse in still air. Now add in the fact the the TANS computed position was in error by 280m SW, it is likely that the HSI was showing very slightly left of track (Chinook operators - how was the HSI calibrated when slaved to TANS?).
From the crew's perspective, this slight 'left of track' might have given them the idea that they were slightly further away from the lighthouse than they were and slightly to the left. In effect, that may have added to any visual illusion and /or confusion as they approcahed WP A - exacerbated by a 20 kt southerly wind (pointing the nose of the ac further right) . A little confusion at this point may have taken up some extra brain power for the crew to orientate themselves - maybe enough to delay the sighting of the lighthouse area, change WP and start the turn to the left. I can't find reference to it but does anyone know what hdgs were selected on the HDG bugs? The geometry indicates they had approx 20 secs to impact from where we presume the ac actually was at WP change and a max of 10 secs to start a turn left to avoid overflying the coast. Actually, that is quite a long time at Low level. So it begs the question - why didn't they turn towards the north - the one-million-dollar question?
If the crew were not visual with the land at this time and they carried on, then they probably did get it wrong by delaying the turn longer than 10 secs after WP change or by climbing too late/too low ROC. This is as postulated by the ROs, caz etc - but this is somewhat negated by the fact the crew changed waypoints, indicating they were visual with WP or its area.
However, it is also perfectly feasible, based on the testimony of the yachtsman (who was in a better position to see what the crew could see than those who were on land and above the base of the upslope stratus), that the ac was remaining 'VFR below' . If you can accept that, then the crew were not negligent at, or even before, the WP change. If only a ADR/CVR had been fitted - what a poor decision that was!
But what happened after the WP change is definitely UNKNOWN. Perhaps the delayed turn was because of the visual illusions and disorientation caused by the small nav kit errors? Of course, control restrictions/UCFMs and spurious Eng Fail captions/Runaways up 'cannot be discounted' either.
What is certain is that, because there was no ADR/CVR, the final minutes of ZD576 are a mystery to us all. With that as foundation, perhaps someone could explain how the burden of proof relating to Gross Negligence is met?
I don't suppose caz or baston will agree, alas!
In fact' they will probably either 'diss' everything I have said with no rational discussion or just put their fingers in their ears and go lalalalalala (figuratively speaking)!
Could any Chinny drivers please attempt to answer my questions in italics
TVM
flipster