In 1977 Air New Zealand began a series of non-scheduled sightseeing
flights to the Antarctic with DC10 aircraft. The flights left and
returned to New Zealand within the day and without touching down en
route. The southernmost point of the route, at which the aircraft turned
round, was to be at about the latitude of the two scientific bases,
Scott Base (New Zealand) and McMurdo Station (United States), which lie
about two miles apart, south of Ross Island. On Ross Island there are
four volcanic mountains, the highest being Mount Erebus, about 12,450
feet. To the west of Ross Island is McMurdo Sound, about 40 miles long
by 32 miles wide at the widest point and covered by ice for most of the
year.
It was originally intended that the flight route south would be over
Ross Island at a minimum of 16,000 feet. From October 1977, with the
approval of the Civil Aviation Division, descent was permitted south of
the Island to not lower than 6000 feet, subject to certain conditions
concerning weather and other matters. However, the evidence is that the
pilots were in practice left with a discretion to diverge from these
route and height limitations in visual meteorological conditions; and
they commonly did so, flying down McMurdo Sound and at times at levels
lower than even 6000 feet. This had advantages both for sightseeing and
also for radio and radar contact with McMurdo Station. Moreover from
1978 the flight plan, recording the various waypoints, stored in the Air
New Zealand ground computer at Auckland actually showed the longitude of
the southernmost waypoint as 164° 48' east, a point in the Sound
approximately 25 miles to the west of McMurdo Station.
The evidence of the member of the airline's navigation section who typed
the figures into the computer was that he must have mistakenly typed
164° 48' instead of 166° 48' and failed to notice the error. Shortly
before the fatal flight the navigation section became aware that there
was some error, although their evidence was that they understood it to
be only a matter of 10 minutes of longitude. In the ground computer the
entry was altered to 166° 58' east, and this entry was among the many in
the flight plan handed over to the crew for that flight for typing into
the computerised device (AINS) on board the aircraft. The change was not
expressly drawn to the attention of the crew. The AINS enables the pilot
to fly automatically on the computer course ('nav' track) at such times
as he wishes.
The crash occurred at 12.50 pm on 28 November 1979. The aircraft struck
the northern slopes of Mount Erebus, only about 1500 feet above sea
level. There were no survivors. The evidence indicates that the weather
was fine but overcast and that the plane had descended below the cloud
base and was flying in clear air. The pilot, Captain Collins, had not
been to the Antarctic before, and of the other four members of the
flight crew only one, a flight engineer, had done so. The plane was on
nav track.
The Chief Inspector of Air Accidents, Mr R. Chippindale, carried out an
investigation and made a report to the Minister, dated 31 May 1980,
under reg. 16 of the Civil Aviation (Accident Investigation) Regulations
1978. It was approved by the Minister for release as a public document.
The Chief Inspector concluded that 'The probable cause of the accident
was the decision of the captain to continue the flight at low level
toward an area of poor surface and horizon definition when the crew was
not certain of their position and the subsequent inability to detect the
rising terrain which intercepted the aircraft's flight path'. He adhered
to this in evidence before the subsequent Royal Commission.
The Royal Commission was appointed on 11 June 1980 to inquire into 'the
causes and circumstances of the crash', an expression which was
elaborated in terms of reference consisting of paragraphs (a) to (j).
Mr. Justice Mahon was appointed sole Commissioner. In his report,
transmitted to the Governor-General by letter dated 16 April 1981 and
subsequently presented to the House of Representatives by Command of His
Excellency and later printed for public sale, the Commissioner found
that '... the single dominant and effective cause of the disaster was
the mistake made by those airline officials who programmed the aircraft
to fly directly at Mt. Erebus and omitted to tell the aircrew'. He
exonerated the crew from any error contributing to the disaster.
The Commissioner and the Chief Inspector were at one in concluding that
the crash has occurred in a whiteout. The Commissioner gave this vivid
reconstruction in the course of para. 40 of his report:
I have already made it clear that the aircraft struck the lower
slopes of Mt. Erebus whilst flying in clear air. The DC10 was at
the time flying under a total cloud cover which extended forward
until it met the mountain-side at an altitude of somewhere between
2000 and 2500 feet. The position of the sun at the time of impact
was directly behind the aircraft, being in a position approximately
to the true north of the mountain and shining at an inclination of
34°. The co-existence of these factors produced without doubt the
classic 'whiteout' phenomenon which occurs from time to time in
polar regions, or in any terrain totally covered by snow. Very
extensive evidence was received by the Commission as to the
occurrence and the consequences of this weather phenomenon. So long
as the view ahead from the flight deck of an aircraft flying over
snow under a solid overcast does not exhibit any rock, or tree, or
other landmark which can offer a guide as to sloping or uneven
ground, then the snow-covered terrain ahead of the aircraft will
invariably appear to be flat. Slopes and ridges will disappear. The
line of vision from the flight deck towards the horizon (if there
is one) will actually portray a white even expanse which is
uniformly level.
What this air crew saw ahead of them as the aircraft levelled out
at 3000 feet and then later at 1500 feet was a long vista of flat
snow-covered terrain, extending ahead for miles. Similarly, the
roof of the solid overcast extended forward for miles. In the far
distance the flat white terrain would either have appeared to have
reached the horizon many miles away or, more probably, merged
imperceptibly with the overhead cloud thus producing no horizon at
all. What the crew could see, therefore, was what appeared to be
the distant stretch of flat white ground representing the flat long
corridor of McMurdo Sound. In reality the flat ground ahead
proceeded for only about 6 miles before it intercepted the low ice
cliff which marked the commencement of the icy slope leading
upwards to the mountain, and at that point the uniform white
surface of the mountain slope proceeded upwards, first at an angle
of 13°, and then with a gradually increasing upward angle as it
merged with the ceiling of the cloud overhead. The only feature of
the forward terrain which was not totally white consisted of two
small and shallow strips of black rock at the very bottom of the
ice cliff, and these could probably not be seen from the flight
deck seats owing to the nose-up attitude of 5° at which the
aircraft was travelling, or they were mistaken for thin strips of
sea previously observed by the crew as separating blocks of pack
ice.
The aircraft had thus encountered, at a fateful coincidence in
time, the insidious and unidentifiable terrain deception of a
classic whiteout situation. They had encountered that type of
visual illusion which makes rising white plateaux appear perfectly
flat. This freak of polar weather is known and feared by every
polar flier. In some Arctic regions in the Canadian and in the
north European winter, it is responsible for numbers of light
aircraft crashes every year. Aircraft fly, in clear air, directly
into hills and mountains. But neither Captain Collins nor First
Officer Cassin had ever flown at low altitude in polar regions
before. Even Mr Mulgrew [the commentator for the passengers], with
his antarctic experience, was completely deceived. The fact that
not one of the five persons on the flight deck ever identified the
rising terrain confirms the totality of this weird and dangerous
ocular illusion as it existed on the approach to Mt. Erebus at
12.50 p.m. on 28 November 1979.
Paragraph 165 of the Commissioner's report also merits quotation. We
have underlined some of it, indicating that in this particular part of
his report the Commissioner seems to accept that when they first heard
of the crash the management of the airline must have been unaware of the
true nature and danger of a whiteout. If so, they would have had no
reason to suppose that the pilot would have elected to fly at such a low
level without real visibility. That is an aspect which could well have
been strongly relied on if, when giving evidence before the
Commissioner, they had realised that they were being accused of trying
to cover up the cause of the crash from an early stage:
The term 'whiteout' has more than one meaning as being descriptive
of weather conditions in snow-covered terrain. For aviation
purposes it is often described as the cause of the visual
difficulty which occurs when a aircraft is attempting to land
during a snowstorm. As already stated, the United States Navy
maintains a special whiteout landing area situated to the south of
its normal landing strips near McMurdo Station. This area is used
when an aircraft, which is committed to a landing, is required to
land when visibility is obscured by a snowstorm. The snow in
Antarctica is perfectly dry, and a wind of only 20 kilometres can
sweep loose snow off the surface and fill the air with these fine
white particles. A landing on the special whiteout landing field
can be accomplished only by an aircraft equipped with skis or, in
the case of an aircraft without skis, then it must make a belly-up
landing on this snow-covered emergency airfield. Flying in a
'whiteout' of that description is no different from flying in thick
cloud. The pilot cannot know where he is and must land in
accordance with strict radio and radar directions. So far as I
understand the evidence, I do not believe that either the airline
or Civil Aviation Division ever understood the term 'whiteout' to
mean anything else than a snowstorm. I do not believe that they
were ever aware, until they read the chief inspector's report of
the type of 'whiteout' which occurs in clear air, in calm
conditions, and which creates this visual illusion which I have
previously described and which is, without doubt, the most
dangerous of all polar weather phenomena.
While largely agreed about the whiteout conditions, the Commissioner and
the Chief Inspector took quite different views as to whether the crew
had been uncertain of their position and visibility. This disagreement
is associated with a major difference as to the interpretation of the
tape recovered from the cockpit voice recorder covering the conversation
on the flight deck during the 30 minutes before the crash.
Both the Commissioner and the Chief Inspector found difficulty in
arriving at an opinion about what was said and by whom. Whereas the
Chief Inspector thought that the two flight engineers had voiced
mounting alarm at proceeding at a low level towards a cloud-covered
area, the Commissioner thought that Captain Collins and First Officer
Cassin had never expressed the slightest doubt as to where the aircraft
was and that 'not one word' was ever addressed by either of the flight
engineers to the pilots indicating any doubt. This is not a question on
which the present proceedings call for any opinion from this Court, nor
are we in any position to give one.
A major point in the Commissioner's reasoning, and one that helps to
explain the difference between the two reports, is that on the basis of
evidence from the wife and two daughters of Captain Collins he accepted
that, at home the night before the flight, the Captain had plotted on an
atlas and two maps a route of the flight; and he drew the inference that
Captain Collins must then have had with him a computer print-out. Any
such print-out would have been made before the alteration and
consequently would have shown the longitude of the southernmost waypoint
as 164° 48' E. The Commissioner accordingly concluded that Captain Collins
had plotted a route down the Sound. No doubt this tended to reinforce
his view that the Captain, flying on nav track, had never doubted that
he was in fact over the Sound.