Using IFF for Range
I have entered into a series of PMs with Walter about this subject and he seems convinced that the crew of ZD576 may have been using an IFF mode to get range from a portable beacon placed at or near the planned turning point at the end of the Mull. Seems most unlikely (bordering on the fantastic!) to me, but I'm a fast-jet man, not a Chinook man, so is there a Chinook man out there who can address his concern?
He, like AM Day, thinks that the turn (of 7 degrees), 'belly up' to the coast would have been difficult to judge, meaning they were negligent. Walter's solution is that they must've been using some kind of DME, which proved to be eroneous, somehow causing the crash. My thought is that, even if an IFF DME range were available, there would be little or no use for the information and the pilots would have turned using straightforward visual range cues and that Day's negligence claim based on this is (I'll remain polite) erroneous. Perhaps, whilst you're about it, you (Chinook man) could suggest an angle of bank and length of time for a 7-degree turn - my estimate would be 15 deg bank for 5 secs.