of Cape Hallett to find clear air further on and took the opportunity of
visual meteorological conditions to veer laterally from the direct
computer flight track from Cape Hallett by tracking to the west along
the coast of Victoria Land and eventually down McMurdo Sound over the
flat sea ice. Ross Island was thus left to the east while near the head
of the Sound the aircraft would turn left in order to fly over Scott
and McMurdo bases and in the vicinity of Ross Island so that a view
would be obtained of Mt. Erebus and the other three mountains there.

When the decision was made to operate the series of flights to take
place at the end of 1977 a change was made with the approval of the
Civil Aviation Division to permit flights below 16,000 feet down to
6,000 feet in a specified sector south of Ross Island and subject to
such criteria as a cloud base no lower than 7,000 feet, clear visibility
for at least 20 miles and descent under ground radar guidance. It has
been mentioned that similar criteria applied, officially at least, until
the time of the fatal crash. But the written directions were interpreted
by some pilots as leaving them with a degree of discretion to go lower
in ideal weather conditions.

Then in September 1978 steps were taken to print a flight plan for each
Antarctic journey from a record stored in the Air New Zealand ground
based planning computer. And it is at this stage that the longitude
co-ordinate for the southernmost waypoint was fed into the ground
computer as 164° 48' E.


The Flight Track

The navigation system used by DC10 aircraft is a computerised device