Regarding the weather, McMurdo was reporting overcast in their vicinity and clear air to the northwest, which the crew worked out would be roughly around Cape Bird according to the CVR. The exact conditions at the time we can only speculate upon, because by the very nature of the location, there was no-one else in the McMurdo Sound/Lewis Bay area (McMurdo Station is, if I recall correctly, positioned to the south of Erebus).
Regarding the rulebook we're banging our heads against here - we need to take into account the fact that the majority of ANZ flights to the Antarctic descended to levels between 3,000 and 1,500 feet. There is no definitive proof of the weather conditions on those flights either, and if your position is such that the regulation should have been followed to the letter, then you should at least concede that ANZ were remiss in not identifying this as a problem and disciplining the pilots concerned. The fact is that they did not - these flights were sold in the company's own literature as "low-level" sightseeing flights, and actively promoted them as such when times were good. The line pilots shared their experiences with each other, and it became a de facto standard to disregard the 6,000ft limit - I wouldn't be surprised if many of the pilots weren't even aware such a limit existed before the accident.
The limit itself was drawn up by Civil Aviation with ANZ's help - it was a special case in the first place, specific to the route, because the route was unique on ANZ's roster. It doesn't even mention clearance to descend below 6,000 feet, which in most cases was suggested by McMurdo, and if the rules were followed as closely as you desire, would be declined on every occasion.
Going back to the conditions for previous flights, again we can only speculate on what they were, as no records were kept. Chippindale says that other flights occurred in "brilliantly clear conditions", but he must himself have been speculating as I'm sure he didn't interview every single pilot that went down there, and even if he did I doubt strongly that they'd have been able to paint an accurate picture of the conditions they were flying in in the months previously. So to say that the crew on this occasion acted contrary to established procedure is disingenuous in the extreme. Also, sector whiteout can occur even in clear conditions, as mentioned earlier in the thread.
The only proven difference between the accident flight and those prior was the switch in co-ordinates. That being the case, if any of those flights (or indeed any of the following flights, had Collins been luckier and his flight returned) had flown the INS waypoints handed out that day, any one of them could have impacted Erebus. Certainly speaking for myself, this is why I think that ascribing the primary cause as pilot error was completely myopic.
Antarctica is a harsh and unforgiving terrain, certainly - and flying in the area definitely requires a degree of care over and above normal operations. But between ANZ, Civil Aviation and the pilots, they got it as close to normal operations as was possible at the time. Maybe they shoudn't have - but this wasn't a small Twin Otter operation bouncing around at low level where everything is at the pilot's risk and discretion, this was a tri-monthly scheduled service that had been performed for around two years. Collins had no reason to expect that he would be in any more danger than his peers, and even given that it would seem he prepared diligently - certainly giving it more attention than any regular scheduled "Auckland to Los Angeles" flight.
Finally, Mahon's report was recognised as an official report into the disaster when it was tabled in the New Zealand Parliament on the 25th of August 1999.
Last edited by DozyWannabe; 5th Mar 2010 at 20:41.