Still don't see how anyone can claim that descent down to 1500ft in an area that has a substantially higher MSA and doing it solely based on what the INS is telling you is normal practise.
For a regular flight of course not - and probably not for sightseeing flights now, as a result of lessons learned. But every pilot that flew that route prior did just that, and they were allowed to as long as the visibility was good - which as far as the accident crew was concerned, it was.
Regarding the weather radar, I believe Mahon went to visit Bendix, where he discovered from the manufacturers concerned that the atmosphere in the region is too dry, weather radar being reliant on atmospheric moisture, to make it useful as a warning for terrain at that altitude. The radar return would, unfortunately, only have confirmed what they believed they were seeing - a flat expanse of sea ice to the horizon.
And as has been stated before many times, the captain did indeed check the waypoints against charts the night before - in fact he showed his daughters where he was going on the family atlas. Those waypoints were changed in the early hours of the morning they took off and the flight crew were not notified of the change.
Regardless of one's opinion of the responsibilities of an airline captain once the aircraft has left the ground, it is important to also bear in mind the responsibilities of the employer to allow their employees to operate safely, and while I'm sure ANZ in the late '70s was not alone in this, there was a staggering degree of corporate complacency going on. Firstly, the rescinding of the rule that every Antarctic flight should have at least one crew member on the flight deck who had been down there before. Secondly, the laissez-faire attitude to the enforcement of MSA on Antarctic sightseeing flights. Thirdly, the failure of the Nav Section to perform a re-check on the co-ordinates fed into the computer, which remained incorrect for over a year - giving line pilots the impression that the intended route was down McMurdo Sound and not over Erebus.
Given sector whiteout conditions, the only clue that the crew would have that something had changed would be the different co-ordinates for the McMurdo waypoint on the printout they were given at pre-flight compared to the materials they'd been given at the briefing - how many pilots check that on a regular basis?