43 Years ago today: On 28 November 1979 an Air New Zealand DC-10 struck Mount Erebus, Antarctica, killing all 257 occupants.
|Date:||Wednesday 28 November 1979|
McDonnell Douglas DC-10-30
|Operator:||Air New Zealand|
|Total airframe hrs:||20763|
|Engines:||3 General Electric CF6-50C2|
|Crew:||Fatalities: 20 / Occupants: 20|
|Passengers:||Fatalities: 237 / Occupants: 237|
|Total:||Fatalities: 257 / Occupants: 257|
|Aircraft fate:||Written off (damaged beyond repair)|
|Location:||Mount Erebus ( Antarctica)|
|Crash site elevation:||447 m (1467 feet) amsl|
|Phase:||En route (ENR)|
|Nature:||Domestic Non Scheduled Passenger|
|Departure airport:||Auckland International Airport (AKL/NZAA), New Zealand|
|Destination airport:||Christchurch International Airport (CHC/NZCH), New Zealand|
In 1977 Air New Zealand received permission from the Director of Civil Aviation to conduct scenic charter flights overflying Antarctica in the McMurdo area, using DC-10 airliners.
Flight crews that operated these flights received a dedicated route qualification briefing which included the route that was to be flown and the operational limits regarding a.o. altitude and visibility.
Nineteen days before the planned departure of flight TE901, both pilots received this briefing during which diagrams and maps were issued that depicted a track which passed to the true west of Ross Island over a sea level ice shelf.
Subsequently the airline discovered that the IFR computer stored flight plan route contained the wrong destination coordinates with an error of 2° in longitude. This was changed just prior to departure of flight 901. The flight crew thus assumed they would be able to descend over a sea level ice shelf, whereas the corrected route would take the aircraft straight towards the turning point over Williams Field Air Base. This route passed direct over Mount Erebus reaching to 12450 feet AMSL. The flight crew programmed their navigation computer using these new coordinates, without having been notified of this change.
The aircraft, ZK-NZP, then took off from Auckland International Airport at 19:17 (27 November). The flight progressed normally from Auckland to Antarctica and the weather was clear over Northern Victoria Land. The aircraft was on its planned track and turned over the appropriate point at Cape Hallett to proceed direct towards the next planned waypoint (the TACAN at Williams Field) near McMurdo.
During this leg of the flight the weather conditions over McMurdo and Ross Island generally overcast with a ragged cloud base of 3000 feet. The direct flight from Cape Hallett to Williams Field was interrupted some 40 miles true north of McMurdo to take advantage of a hole in the cloud cover, which extended vertically to sea level and to descend the aircraft in this gap prior to its planned arrival near McMurdo. The captain bad been advised that the visibility below the cloud which was over Ross Island, was 40 miles.
This descent was made despite the safety requirements to maintain a minimum sector altitude of 16000 feet until overhead McMurdo TACAN and to descend below that height only in a specified sector and in weather conditions of 20 km visibility and no snow showers, and after contacting the radar controller.
When flight 901 requested a clearance for a descent from 10000 to 2000 feet on a heading of 180° Grid (i.e. towards the north) and to proceed to McMurdo VMC there was no reason for the Air Traffic Centre staff at McMurdo to question this as it was from a reported position to the true north of Ross Island and therefore the descent would take the aircraft back out over the sea level ice and the flight had confirmed it would maintain VMC inbound to McMurdo.
Had the crew followed their stated intention to descend on a heading of 180° grid they would have increased their safety margin from the high ground, but without further advice to McMurdo Centre the pilot in command reversed the aircraft’s descent track and from 5800 feet the descent to 2000 feet was completed on a heading of 357° grid back toward the cloud covered high ground. This inbound track had a minimum safe altitude of 16000 feet. After reaching 2000 feet the aircraft captain announced he would descend a further 500 feet to obtain a better view below the continuous cloud layer.
The aircraft headed toward the cloud covered island, while the pilots were under the assumptions they were safely over a sea level ice shelf.
The captain descended the aircraft a further 500 feet from the original 2000 feet but at 1500 feet and at a distance to run of 26 miles he finally became concerned and stated “We’re 26 miles north, we’ll have to climb out of this”.
The weather conditions had a high potential for a whiteout phenomenon due to the overcast conditions above the continuous snow covered slope. After the captain’s decision to climb the aircraft out of the area he and the co-pilot were discussing the most suitable climbout path when the ground proximity warning system sounded instructing the crew to “Pull up”. The crew responded to the alarm without undue hesitation, the flight engineer calling off the heights of 500 and 400 feet indicated on the radio altimeter and the captain calling for “Go-round power”. The warning 6,5 seconds before the impact was, however, too late for the crew’s action to make any significant effect on the aircraft’s level flight path.
The ground proximity warning system’s alarm was delayed because the terrain closure started from above a coastal cliff 300 feet high instead of a steadily increasing slope which would have triggered the warning approximately 3 seconds earlier. The system has an approximate 6 second delay after it first senses a dangerous closure rate with the terrain below the aircraft. This is to minimise spurious alerts triggered by short steep slopes below the aircraft during normal safe flight paths.
The aircraft collided with the ice slope of Mount Erebus on Ross Island at an elevation of 1467 feet AMSL and immediately started to break up. A fire was initiated on impact and a persistent fire raged in the fuselage cabin area after that section came to rest.
An accident investigation report by the Chief Inspector of aircraft accidents, came out in May 1980. The probable cause according to this investigation 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.”
Due to public demand, the New Zealand Government announced a further one-man Royal Commission of Inquiry into the accident, to be performed by judge Justice Peter Mahon. In April, 1981 he released his report. He concluded that: “The dominant cause of the disaster was the act of the airline in changing the computer track of the aircraft without telling the air crew.” He continued: “In my opinion, therefore, 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. That mistake is directly attributable, not so much to the persons who made it, but to the incompetent administrative airline procedures which made the mistake possible. In my opinion, neither Captain Collins nor First Officer Cassin nor the flight engineers made any error which contributed to the disaster, and were not responsible for its occurrence.”
In para. 377 of his report, Mahon controversially claimed airline executives and management pilots engaged in a conspiracy to whitewash the enquiry, famously accusing them of “an orchestrated litany of lies” by covering up evidence and lying to investigators.
Air New Zealand and the Civil Aviation Division were ordered to pay the costs of the inquiry, and the airline had to pay an extra fee of $150,000.
Air New Zealand appealed against Mahon’s findings to the Court of Appeal, which set aside the costs order against the airline. Mahon in turn appealed to the Privy Council in London. His findings as to the cause of the accident, namely reprogramming of the aircraft’s flight plan by the ground crew who then failed to inform the flight crew, had not been challenged before the Court of Appeal, and so were not challenged before the Privy Council. His conclusion that the crash was the result of the aircrew being misdirected as to their flight path, and was not due to pilot error, therefore remained. But the Board held that Mahon had acted in excess of his jurisdiction and in breach of natural justice by going on to make findings of a conspiracy by Air New Zealand to cover up the errors of the ground staff. In their judgment, delivered on 20 October 1983, the Law Lords dismissed Mahon’s appeal and upheld the decision of the Court of Appeal.