Originally Posted by
chris lz
But in a sense, isn't that precisely why INS is not as reliable as ground aides? They can be inadvertently misprogrammed. The crew themselves can mistakenly punch in a wrong coordinate. If you've never been to destination before, wouldn't it also be prudent to check the programmed coordinates you've just entered and make sure they match the actual coordinates for the McMurdo Sound route?
This is where things get murky, thanks to the actions of certain contemporary ANZ management people and the US radar station staff. If Collins was true to form he would have checked and re-checked the co-ordinates on his ops sheet against what was in the AINS system before takeoff and found no discrepancy. The rest of the story would be found in his little A6 ring binder. This was recovered from the site by police and sealed in an evidence bag by Inspector Gilpin, noting that it contained "numerous pages of legible technical writing and figures that indicated they related to the flying of aircraft. We recognised that this could be of importance to any investigation into the crash, and I sealed and secured it in a bag before it was returned to McMurdo". The NZCAA officials were not there yet, so it wound up in the hands of Chief Pilot Gemmell, and was never seen again in its intact state publicly, instead turning up at the 1981 inquiry with all its pages removed.
True to his meticulous nature, Collins performed all the cross-checking at home the previous night, which can only lead to the conclusion that contained in that book was proof that he was certain they were going down McMurdo Sound and not over Erebus. This would have rendered ANZ's case at the inquiry null and void, because it relied entirely on the idea that the nav track had *always* run over Erebus, and it was the McMurdo track that was an aberration. Hewitt's navigation change was input to the computer at approximately 1:40AM the morning of the flight, and nobody told Collins or any of his crew. At his preflight briefing he had every right to believe that the co-ordinates he had fastidiously plotted before retiring the night before and the ones he now held in his hand, and would later cross-check as he input the co-ordinates into AIMS, were one and the same.
I'm aware the Lewis Bay track and the expected route down McMurdo Sound would have appeared similar. But before the letdown commenced, could the crew really be 100% certain of their position by visual means alone?
Up until the crash flight, it was all they had. The southernmost waypoint in all previous INS-navigated Antarctic flights was to a point just west of the Dailey Islands and had no navaid (because it was, as it turns out, a typo rather than an actual fix), and the NDB at McMurdo, which was the secondary navaid fix, had been withdrawn in 1978. And forget "similar" - unless you were intimately familiar with the area, in certain conditions they would have appeared nigh-on identical. Prospector likes to talk about Beaufort Island being on the wrong side, but looking at the let-down tracks, it's possible they would have emerged from cloud south of the island - photos exist of the island taken from within the passenger cabin, but there is no proof that it would have been visible from the flight deck. In any case they were taking a visual fix from Cape Tennyson, thinking it was Cape Royds, and Cape Bird, thinking it was Cape Bernacchi.
Hewitt selected the new navaid fix in 1978, which would be the TACAN south of Ross Island, but because of the typo, none of the crews ever knew that was the intent - they simply entered the co-ordinates and assumed that the new route was designed to follow the military track. To my mind it looks like Hewitt simply entered the co-ordinates into the computer from his data sheet - did not re-check them against a map as he was entering them, and forgot about it entirely until Captain Simpson reported the 26 mile discrepancy three weeks before the Collins flight. After making the correction, Hewitt made no attempt to contact the computer section to confirm that it had been updated, and likewise the computer section did not confirm with nav section that the work had been done. Again, to my mind very unprofessional behaviour.
The only major concern from the confirmed voices on the CVR seems to be that Mac Central was out of radio contact in the last few minutes of the flight - however the transponder was coding, indicating that the crew believed that they were being tracked on radar. The radar tapes that covered the last four minutes and change leading up to the crash had been erased, and Mahon got a very frosty reception from the US base when he visited and made it known he was aware of this.
I want to make it clear that even though I think Vette and Mahon's investigations were more in-depth and the conclusions more correct than those of Chippindale, this does not invalidate entirely the work that Chippindale did, and I don't think he was any less than scrupulously honest about what he believed. The problem as I see it is that the information Chippindale had to work from was tightly controlled by ANZ, and that most of what he had to work with was only the material that ANZ wanted him to see. The only major fault I see in Chippindale's methodology was inviting Captain Gemmell to participate in his re-write of the CVR transcript, and indeed, revising the content of the CVR transcript from what was agreed in Washington in the first place. I'm sure that had he known that Captains Gemmell and Crosby were engaged in the obtaining and destruction of evidence from Collins' and Cassin's files - even clearing material from their homes without the knowledge or permission of their families, he would not have been so sanguine about their involvement in his investigation.