trilander
Just for the record, they were flying in good visibility in all directions apart from straight ahead and to the right (they were approaching the Mull at quite an obtuse angle) until they actually entered the mist which was on the Mull land mass itself (caused by the rising moist air in the prevailing strong wind – a common condition at that location at that time of the year) – and of course there was plenty of light at that time at that latitude at that time of the year. The only problem that those local weather conditions would have posed for the crew was the judgment of their distance to go to the Mull shoreline (which they were approaching at quite a speed with the strong tailwind) with the ground detail obscured.
It has been suggested that they may have been distracted by such things as spurious engine warnings and the like or perhaps an actual malfunction in control or performance; given that they were already very close to the rock, if they had known how close they actually were, surely such a quality and experienced crew would not have allowed any such warning or actual performance anomaly to distract them from the immediately essential flying. Surely had they known how close they actually were, their first reaction should have been to give themselves some room to manoeuvre while they addressed any such problem – a slight turn to the left would have achieved this, turning a bit earlier than planned, anything but to carry straight on as they did.
So I say, even the suggested distraction theories require that they were somehow misled as to their proximity to the Mull.
As they had already got so very close to the Mull when they changed waypoints in conditions where they could not have visually judged their distance (or they would surely have started to turn, OK?) their slight turn to the right and continuation suggests that they were under some obligation to get in very close and must have had a reference to something.
One would have thought that some discussion of this obvious aspect would have been warranted but it would appear that it is taboo. And yet every known, or reasonably assumed, characteristic of this flight is consistent with them pressing on to a close in position and being surprised (remember the very last manoeuvre – extreme left yaw pedal and pull up) as though they thought they were further out.
As a point of interest, if they had started their (apparent) cruise climb ½ to 1 mile further out they would have been high enough to get (radio) LOS to the Macrihanish TACAN (or DME, whichever it was that was operational at the time) and to which the TACAN CU was found to have been set (ch 107) which would have allowed them an accurate distance from that navaid to, say, waypoint A. Popping their heads up a bit to check on something, perhaps – maybe salvaging something from a test where conditions did not allow visual confirmation or a touchdown. No other scenario explains both cruise climb and the selection of ch 107.
ZD576 was the first RAF HC2 Chinook to have the ability to have the on board equipment plugged into the nav avionics racks to try out the personnel locator system procured for RAF Chinooks only a year later; the groundside equipment was available at that time in the hands of US SEALS present on the Mull and they were experienced in its use – what an opportunity for a test!; but no such on board equipment was found in the wreckage? - the nav avionics racks had apparently incorrectly stowed connectors (or something like that) consistent with inexpert removal of a piece of equipment (the ground crew who had worked on the racks immediately before the flight was blamed for incorrect procedures, I believe); and of course there was the response from one of the SEALS, who were all over the crash site when UK authorities turned up, when challenged – they were looking for their equipment. All that was required was for the ground equipment (hand held) to be, say, ½ a mile up the hill from where it was supposed to have been (say, the lighthouse helipad) and an obstruction to the peace process was removed.
Yeh, you could count on that local weather at that time of year near the evening ....