And who has not got a grasp on a mandatory requirement? Got nothing to do with NZ regulations. VMC descents or whatever.
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