Originally Posted by
chris lz
In practical terms, in 1979 on a DC-10, is it reasonable then to suppose that this type of error was far more likely than a failure of a ground based navigation aide? I'm thinking the answer is "yes." But then I have heard from one pilot that AINS is "much more accurate" than what a typical ground based aide would predict for a plane's exact position. Maybe this is true also?
The problem as this applies to the Erebus crash is that on each Antarctic flight using it the AINS had been completely accurate every single time. The reason ANZ tried so hard to muddy the waters was because their navigation section had mis-keyed the fix in the first place and left it that way for over a year, even to the extent that the charts presented to the pilots at briefing showed the "incorrect" route - this left them vulnerable to accusations of incompetence in the first instance. Correcting the route to the TACAN in the middle of the night without notifying the crew who had been briefed on the previous route and were due to leave in the morning could, in the hands of a lawyer, open them to accusations of gross negligence in trying to cover up their earlier incompetence - hence the all-out effort to destroy all evidence that showed the McMurdo Sound track had been the accepted route for a year.
Regarding ground navaids, the McMurdo NDB had been gone since 1978 - all there was in the area was the TACAN, which - while it had been the intended waypoint as far as nav section's seniors were concerned since the NDB was decommissioned - was never on the route supplied to the pilots between 1978 and 1979, nor was it's existence briefed. If crews had known about it, the only purpose it could serve would be to provide a fix after they had made the left turn south of Ross Island, because to use it as a direct fix during their south-westerly track would have taken them straight over, or indeed into the side of, Erebus - which at low level would have been a major safety hazard, and at high level would have contradicted the whole purpose of the flight, which was sightseeing.
@IGh - Ironically it was the global response to the Mahon report that made accident investigation what it is today. I disagree that the NTSB's independence harms the quality of it's output, however, and I know the "'Hoot' Gibson" incident, of which you are talking, fairly well. It wasn't just Boeing who advanced that particular theory though, the truth is that a lot of line pilots knew about the use of CB's to pop the slats in cruise - my suspicion is that the NTSB and the FAA had been looking for an opportunity to end the practice for a long time and for better or worse used that incident to do so. To discuss it further here would be taking the thread off-topic however.