deadhead,
From John King's "New Zealand Tragedies, Aviation".
This was referred to in a company memorandum to Antarctic crews, OAA 14/13/28 dated 8 November 1979. Headed McMurdo NDB NOT AVAILABLE, it was succinct and unambiguous.
Delete all references in briefing dated 23/10/79. Note that the only let down procedure available is VMC below FL160 (16,000ft) 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 Grid through 360 Grid to 270 grid from McMurdo Field, within 20 nm of TACAN CH29
4. Descent to be coordinated with local radar control as they may have
other traffic in area.
A copy of this memorandum was recovered from cockpit wreckage.
Meanwhile the crew of Flight TE901 approaching Antarctica had discussed the weather with the McMurdo meteorological office which advised that Ross Island was under a low overcast base of 2,000ft with light snow and a visibility of 40 nautical miles.