November 1979 aviation accident in Antarctica
The Mount Erebus disaster occurred on 28 November 1979 when Air New Zealand Flight 901 (TE901) flew into Mount Erebus on Ross Island, Antarctica, killing all 237 passengers and 20 crew on board. Air New Zealand had been operating scheduled Antarctic sightseeing flights since 1977. This flight left Auckland Airport in the morning and was supposed to spend a few hours flying over the Antarctic continent, before returning to Auckland in the evening via Christchurch.
The initial investigation concluded the accident was caused primarily by pilot error, but public outcry led to the establishment of a Royal Commission of Inquiry into the crash. The commission, presided over by Justice Peter Mahon, concluded that the accident was primarily caused by a correction made to the coordinates of the flight path the night before the disaster, coupled with a failure to inform the flight crew of the change, with the result that the aircraft, instead of being directed by computer down McMurdo Sound (as the crew had been led to believe), was instead rerouted to a path toward Mount Erebus. Justice Mahon's report accused Air New Zealand of presenting "an orchestrated litany of lies", and this led to changes in senior management at the airline. The Judicial Committee of the Privy Council later ruled that the finding of a conspiracy was a breach of natural justice and not supported by the evidence.
The accident is the deadliest in the history of Air New Zealand, the deadliest aviation accident in Antarctica, and New Zealand's deadliest peacetime disaster.
Flight and aircraft.
Flight 901 was designed and marketed as a unique sightseeing experience, carrying an experienced Antarctic guide, who pointed out scenic features and landmarks using the aircraft's public-address system, while passengers enjoyed a low-flying sweep of McMurdo Sound. The flights left and returned to New Zealand the same day. The plane left Auckland International Airport at 8:00 am for Antarctica, and was scheduled to arrive back at Christchurch International Airport at 7:00 pm after flying . The aircraft would make a 45-minute stop at Christchurch for refuelling and a crew change, before flying the remaining to Auckland, arriving at 9:00 pm. Tickets for the November 1979 flights cost NZ$ per person (equivalent to $ in 2021). Dignitaries including Sir Edmund Hillary had acted as guides on previous flights. Hillary was scheduled to act as the guide for the fatal flight of 28 November 1979, but had to cancel because of other commitments. His long-time friend and climbing companion, Peter Mulgrew, stood in as guide.
The aircraft used for Antarctic flights were Air New Zealand's eight McDonnell Douglas DC-10-30 trijets. The aircraft on 28 November was registered ZK-NZP.
The 182nd DC-10 to be built, and the fourth DC-10 to be introduced by Air New Zealand, ZK-NZP was handed over to the airline on 12 December 1974 at McDonnell Douglas's Long Beach plant. It had logged more than 20,700 flight hours prior to the crash. Captain Thomas James "Jim" Collins (45) was an experienced pilot who had accumulated 11,151 flight hours, including 2,872 hours in the DC-10. First Officer Gregory Mark "Greg" Cassin (37) had accumulated 7,934 flight hours, including 1,361 in the DC-10. Flight Engineer Gordon Barrett Brooks (43) had 10,886 flight hours, including 3,000 in the DC-10 (Brooks had also been Flight Engineer on the Air New Zealand flight involved in the Cessna 188 Pacific rescue in 1978). Also on board were First Officer Graham Neville Lucas (39) and Flight Engineer Nicholas John "Nick" Moloney (44). Flight Engineer Moloney had a total of 6,468 flight hours, including 1,700 in the DC-10.
Accident.
Circumstances surrounding the accident.
Captain Collins and co-pilot Cassin had never flown to Antarctica before (while flight engineer Brooks had flown to Antarctica only once previously), but they were experienced pilots and were considered qualified for the flight. On 9 November 1979, 19 days before departure, the two pilots attended a briefing in which they were given a copy of the previous flight's flight plan.
The flight plan had been approved in 1977 by the Civil Aviation Division of the New Zealand Department of Transport and was along a track directly from Cape Hallett to the McMurdo non-directional beacon (NDB), which, coincidentally, entailed flying almost directly over the peak of Mount Erebus. Due to a typing error in the coordinates when the route was computerised, however, the printout from Air New Zealand's ground computer system that was presented at the 9 November briefing corresponded to a southerly flight path down the middle of the wide McMurdo Sound, about to the west of Mount Erebus. The majority of the previous 13 flights had also entered this flight plan's coordinates into their aircraft inertial navigational system and flown the McMurdo Sound route, unaware that the route flown did not correspond with the approved route.
Captain Leslie Simpson, the pilot of a flight on 14 November and also present at the 9 November briefing, compared the coordinates of the McMurdo TACAN navigation beacon (about east of McMurdo NDB), and the McMurdo waypoint that his flight crew had entered into the inertial navigation system (INS), and was surprised to find a large distance between the two. After his flight, Captain Simpson advised Air New Zealand's navigation section of the difference in positions. For reasons that were disputed, this triggered Air New Zealand's navigation section to update the McMurdo waypoint coordinates stored in the ground computer to correspond with the coordinates of the McMurdo TACAN beacon, despite this also not corresponding with the approved route.
The Air New Zealand navigation section changed the McMurdo waypoint co-ordinate stored in the ground computer system around 1:40 am on the morning of the flight from to . Crucially, the flight crew of Flight 901 was not notified of the change. The flight plan printout given to the crew on the morning of the flight, which was subsequently entered by them into the aircraft's INS, differed from the flight plan presented at the 9 November briefing and from Captain Collins' map mark-ups, which he had prepared the night before the fatal flight. The key difference was that the flight plan presented at the briefing corresponded to a track down McMurdo Sound, giving Mount Erebus a wide berth to the east, whereas the flight plan printed on the morning of the flight corresponded to a track that coincided with Mount Erebus, which would result in a collision with Mount Erebus if this leg were flown at an altitude less than , 12,448 feet (3,794 m) being the top peak of Mount Erebus.
The Air New Zealand computer program was altered so that the standard telex forwarded to US air traffic controllers (ATCs) at the United States Antarctic science facility at McMurdo Station displayed the word "McMurdo", rather than the coordinates of latitude and longitude, for the final waypoint. During the subsequent inquiry, Justice Mahon concluded that this was a deliberate attempt to conceal from the United States authorities that the flight plan had been changed, probably because it was known that US Air Traffic Control would lodge an objection to the new flight path.
The flight had earlier paused during the approach to McMurdo Sound to carry out a descent, via a figure-eight manoeuvre, through a gap in the low cloud base (later estimated to be at around ) while over water to establish visual contact with surface landmarks and give the passengers a better view. The flight crew either was unaware of or ignored the approved route's minimum safe altitude (MSA) of for the approach to Mount Erebus, and in the sector south of Mount Erebus (and then only when the cloud base was at or better). Photographs and news stories from previous flights showed that many of these had been flown at levels substantially below the route's MSA. In addition, preflight briefings for previous flights had approved descents to any altitude authorised by the US ATC at McMurdo Station. As the US ATC expected Flight 901 to follow the same route as previous flights down McMurdo Sound, and in accordance with the route waypoints previously advised by Air New Zealand to them, the ATC advised Flight 901 that it had a radar that could let them down to . The radar equipment did not pick up the aircraft, however, and the crew also experienced difficulty establishing VHF communications. The distance measuring equipment did not lock onto the McMurdo Tactical Air Navigation System (TACAN) for any useful period.
Cockpit voice recorder (CVR) transcripts from the last minutes of the flight before impact with Mount Erebus indicated that the flight crew believed they were flying over McMurdo Sound, well to the west of Mount Erebus and with the Ross Ice Shelf visible on the horizon, when in reality they were flying directly toward the mountain. Despite most of the crew being engaged in identifying visual landmarks at the time, they never perceived the mountain directly in front of them. About 6 minutes after completing a descent in visual meteorological conditions, Flight 901 collided with the mountain at an altitude around , on the lower slopes of the 12,448-ft-tall (3,794 m) mountain. Passenger photographs taken seconds before the collision removed all plausibility of a "flying in cloud" theory, showing perfectly clear visibility well beneath the cloud base, with landmarks to the left and to the right of the aircraft visible.
Changes to the coordinates and departure.
The crew put the coordinates into the plane's computer before they departed at 7:21 am from Auckland International Airport. Unknown to them, the coordinates had been modified earlier that morning to correct the error introduced previously and undetected until then.
The crew evidently did not check the destination waypoint against a topographical map (as did Captain Simpson on the flight of 14 November) or they would have noticed the change. Charts for the Antarctic were not available to the pilot for planning purposes, being withheld until the flight was about to depart. The charts eventually provided, which were carried on the aircraft, were neither comprehensive enough nor large enough in scale to support detailed plotting. These new coordinates changed the flight plan to track east of their understanding. The coordinates programmed the plane to overfly Mount Erebus, a volcano, instead of down McMurdo Sound.
About four hours after a smooth take-off, the flight was away from McMurdo Station. The radio communications centre there allowed the pilots to descend to and to continue "visually". Air-safety regulations at the time did not allow flights to descend to lower than , even in good weather, although Air New Zealand's own travel magazine showed photographs of previous flights clearly operating below . Collins believed the plane was over open water.
Crash into Mount Erebus.
Collins told McMurdo Station that he would be dropping to , at which point he switched control of the aircraft to the autopilot. Outside, a layer of clouds blended with the white snow-covered volcano, forming a sector whiteout – no contrast between ground and sky was visible to the pilots. The effect deceived everyone on the flight deck, making them believe that the white mountainside was the Ross Ice Shelf, a huge expanse of floating ice derived from the great ice sheets of Antarctica, which was in fact now behind the mountain. As it was little understood, even by experienced polar pilots, Air New Zealand had provided no training for the flight crew on the sector whiteout phenomenon. Consequently, the crew thought they were flying along McMurdo Sound, when they were actually flying over Lewis Bay in front of Mount Erebus.
At 12:49 pm, the ground proximity warning system (GPWS) began sounding a series of "whoop, whoop, pull up" alarms, warning that the plane was dangerously close to terrain. The CVR recorded the following:
 GPWS: "Whoop whoop. Pull up. Whoop whoop..."
 F/E: "Five hundred feet."
 GPWS: "...Pull up."
 F/E: "Four hundred feet."
 GPWS: "Whoop, whoop. Pull up. Whoop whoop. Pull up."
 CA: "Go-around power please."
 GPWS: "Whoop, whoop. Pull-"
 CAM: [Sound of impact]
 End of recording. 
The pilots had begun a terrain escape manoeuvre by applying full (go-around) power, but it was too late. Six seconds later, the plane crashed into the side of Mount Erebus and exploded, instantly killing everyone on board. The accident occurred at 12:50 pm at a position of and an elevation of above mean sea level. McMurdo Station attempted to contact the flight after the crash, and informed Air New