Prospector says;
This was the requirement for descent on that flight,
Delete all reference in briefing dated 23/10/79. Note that the only let-down procedure available is VMC below FL160 to 6,000ft as follows.
1. Vis 20 Km plus.
2. No snow showers in area.
3. Avoid Mt Erebus area by operating in an arc from 120 degrees Grid through 360 degrees grid to 270 degrees grid from McMurdo Field, within 20nm of TACAN CH29.
4. Descent to be co-ordinated with local radar control as they may have other traffic in the area
and
Note that this was the only descent procedure approved, it was formulated to allow these flights to be carried out knowing full well the lack of Antarctic experience that existed amongst ANZ crews. Whether they were VMC, VFR or whatever is irrelevant.
No - it was
not the requirement for descent on that flight.
Justice Mahon’s report 40 (b) (my emphasis)
(b) The low altitude of the aircraft:
As stated already, it is beyond dispute that there is no danger in flying at 1500 feet over any flat terrain in clear weather. That altitude is in fact far higher than the minimum safe altitude prescribed for aircraft flights by regulation 38 of the Civil Aviation Regulations.. But it happened that when the Civil Aviation Division of the New Zealand Ministry of Transport had approved these antarctic flights early in 1977, they had prescribed special minimum safe altitudes.. The minimum safe altitude on the approach to Ross Island had been set at 16000 feet and there was a permitted descent of 6000 feet to the south of Ross Island so as to permit sightseeing. This 6000 permission was confined to a special limited sector over the Ross ice shelf to the south of Ross Island.
But as inquiries eventually established, these limits, which may or may not have been observed by the airline for the initial two flights .in February 1977, had not been observed at any time thereafter. In truth, the minimum safe altitude so prescribed by the Civil Aviation Division may have been quite satisfactory as part of an initial flight plan to be used for planning purposes on the first flight. But such minimum safe altitudes of 16 000 feet and 6000 feet, insofar as they were supposed to apply to all Antarctica flights, were misconceived. They had no relation whatever to the realities of sightseeing flights in Antarctica. They continued to be the officially approved levels as between the Civil Aviation Division and the airline from February 1977 right through to the date of the disaster. But in practice the airline disregarded those minimum altitudes, and in my opinion were justified in doing so.
Captains of antarctic flights were specifically briefed in 1978 and in 1979 that they were authorised to descend in the McMurdo area to any flight level authorised and approved by the United States air traffic controller. When Captain Collins accepted the invitation from the United States air traffic controller to descend to 1500 feet where he would find himself in clear air, and with unlimited visibility, he was acting in compliance with authority directly given to him by the airline's briefing officer and under conditions approved by the United States' air traffic controller. The proposed over-flight of McMurdo Sound in the areas specified by the air traffic controller was at a perfectly safe altitude. Contrary to what I think has been a public misconception over this altitude question, there was at no time on 28 November 1979 any unauthorised "low flying" by the crew of TE 901.