ABIW
I think I have explained as best I can on numerous occasions how I think it may have been fitted and as I do not indeed know exactly how for sure, it is only suggestion and an appeal for anyone who may be able to determine this to come forward.
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The evidence that such a system was fitted is simply that everything that is known or that can be reasonably assumed from the available data suggests that they were heading for a particular point closer in than they needed to go, in those conditions, to simply turn up the coast on their ferry flight;
in such conditions, where the hazard can be seen but its detail obscured such that it is difficult to judge visually ones distance off, there is only one system that a helo pilot will trust more than his visual judgment, more than the SuperTANS, more than his dead reckoning, to allow him to approach closely yet keep him a small safe distance from the murk (to keep him in the clear/ to prevent him entering it) and that is a DME system of some sort (ask helo pilots esp North Sea helo pilots);
as at their altitude the MAC beacon was not LOS the only possible candidate remains the PRC112 system;
such a system gives an approximate azimuth bearing (+/- 4deg) which seems the only feasible explanation for that RIGHT steer demand just after waypoint change (already very close in);
ZD576 was the first RAF HC2 that could have a go of this system and US personnel trained, experienced, and equipped with the ground equipment were stationed at Mac some of those in the team would no doubt have been able to have been convinced of the worth of such an opportune demo;
The ground equipment only had to be ½ a mile or so further inland, up the hill from where it was supposed to be and everything is explained.
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There was a strong political motive for them to be stopped from getting to their meeting strong enough, I would suggest, for the possibility of them being set up this way to be at least explored thoroughly. If any of you have something that may confirm the use of this system but are holding back (apart from Off Sec Act, etc) because you think you are just covering up a test that went horribly wrong think again, you could be preventing something much more serious coming to light, something that is worth putting personal considerations aside for.