The decision to descend at 45 miles out, which was just as much a cause of the accident as the changed waypoint, might be explainable. Ten minutes beforehand, Capt Collins had accepted the offer of a radar assist, so the standard procedure would be to maintain MSA until his position had been confirmed and then go down through the cloud. The weather reported to the captain was a continous layer of cloud with a base of 6000 feet. After accepting the radar assist, the F/O tried to contact the Tower on VHF radio (being the only radio the Tower had) and then the captain took over and tried to get the Tower himself, without success. This was just prior to the decision to descend, so the two are probably linked.
The theory about the transponder light coming on cannot be correct, but the descent decision must have had something to do with the proposed radar assist, because that plan was obviously abandoned. The captain would have expected to be in contact with the Tower at least by 60 miles out. As he got to 45 miles out, there had been no contact, despite numerous attempts, so the captain probably concluded that the VHF radio was having one of its off days. If so, there could be no radar assist, whatever be the state of the transponder light. At the time, he was approaching the edge of the cloud layer which, he had been told, extended all the way to McMurdo Station. Without the radar assist, the only way that he and the passengers would get to see the place was VMC, and the only way to do that was to go down the hole while he still had a hole to go down. It was a 'now or never' situation.
Although the decision might be understandable, so too was Capt Van Zanten's, yet he is regarded as a villain, while Capt Collins is regarded as God's gift to NZ aviation. What Capt Collins did was hasty, stupid, negligent, and contrary to the warning he had given to himself only a few minutes beforehand.
All of this was compounded by what happened afterwards. Capt Van Zanten was stuck with his bad decision, but Capt Collins had a full 20 minutes to appreciate his mistake, yet instead of returning to MSA, he kept going down.
Last edited by ampan; 1st Jan 2012 at 20:57.