The first two flights in February 1977 used the geographical coordinates of Williams Field for the McMurdo waypoint. The next four in November that year used the McMurdo NDB. The flight plan track for all six flights between Cape Hallett and the McMurdo waypoint went across Ross Island and Mt Erebus, some 12,500 feet high. For that reason, the minimum safe altitude for that sector was 16,000 feet.
At that time the flight plans were produced manually, and the coordinates for each waypoint for the entire flight (inclusive of the McMurdo waypoint) were taken from the flight plan and individually loaded manually by the flight crew into the DC10 aircraft's sophisticated on-board navigation computer, known as the area inertial navigation system (AINS), prior to departure.
Ahead of the flights scheduled for November 1978, it was decided to store the flight plan information in the airline's ground computer, so that the flight plans could be produced automatically. The coordinates of Williams Field (77° 53' south, 166° 48' east) were selected for the McMurdo waypoint.
When inserting the McMurdo longitude coordinate into the ground computer terminal, the individual concerned made a transpositional error by typing 164° 48' east, instead of 166° 48' east. The two-degree error converted into 27 miles, which placed the McMurdo waypoint roughly in the middle of McMurdo Sound. The effect of the error was that the flight plan track for the final southbound sector from Cape Hallett went down McMurdo Sound, instead of across Ross Island and Mt Erebus. This incorrect coordinate went unnoticed in the flight plans for the four flights in November 1978.
A further four flights were scheduled for November 1979. Captain Collins attended a route clearance briefing with First Officer Cassin on 9 November 1979, at which they were provided with a copy of a flight plan containing the incorrect longitude coordinate. The evidence showed that Captain Collins had noted the coordinates and had later plotted them on a topographical map. There should have been no room at the briefing for ambiguity in the location of the McMurdo waypoint.
Captain Simpson, who commanded the flight on 14 November 1979, attended the same briefing. He, too, was under the impression from the copy of a previous flight plan that the McMurdo waypoint was at the head of McMurdo Sound. On his flight, Captain Simpson checked the actual McMurdo coordinates that had been manually entered into the aircraft's AINS, and mentally related them to a topographical map. This exercise confirmed his understanding that the McMurdo waypoint was located in McMurdo Sound. He thought it would be about 10 miles to the west of the McMurdo base and was surprised to see that in fact the distance was 27 miles.
Two days later Captain Simpson suggested to the captain in charge of the Antarctic flights that future crews should be informed of the full extent of the distance between the TACAN and the McMurdo waypoint, to avoid a similar reaction. This message was taken as suggesting that the TACAN ought to be used as the McMurdo waypoint. The Navigation Section was asked to look into the matter. Instead of checking the McMurdo waypoint on a current computer-generated flight plan, they assumed by reference to the source data used to input the initial McMurdo entry that it was 77° 53' south, 166° 48' east.
The McMurdo TACAN coordinates were 77° 53.7' south, 166° 58' east. They reflected a minor difference of 0.7' latitude and 10' longitude compared with the McMurdo coordinates that the Navigation Section had assumed were on the current flight plan. The 10' of longitude was equivalent to the two miles between Williams Field and the nearby TACAN.
Despite these minor differences, it was thought desirable to incorporate the TACAN as the McMurdo waypoint. The ground computer was routinely updated overnight every Tuesday. The change was therefore effected on the evening before the accident flight on 28 November 1979. Because it was thought to be of a minor nature, the flight crew were not informed.
The change to the McMurdo coordinates was to have fatal implications. On approaching McMurdo, the crew were informed of a low overcast in the area, with a cloud base of 2000 feet and visibility of about 40 miles. The McMurdo base controllers offered them a radar-assisted descent through the cloud to 1500 feet, which they accepted.
The crew could not take advantage of a radar-assisted let down as they were unable to establish the necessary very high frequency radio contact with McMurdo air traffic control, nor were they positively identified on radar. The captain therefore elected, spontaneously it would seem, to take advantage of an area of broken cloud, through which to carry out a visual descent from the minimum safe altitude of 16,000 feet.
On completing their descending orbits, the crew recaptured the inbound flight plan track to the McMurdo waypoint, eventually levelling off at 1500 feet. In carrying out the descent in this way, relying heavily on the AINS for track guidance over the final stages, the crew must have believed the aircraft was programmed to fly towards the McMurdo waypoint on a track that would take them down McMurdo Sound, clear of high ground.
In truth, by virtue of the change to the McMurdo coordinates, the aircraft was on a track directly towards Ross Island and Mt Erebus. At the time, the solid overcast cloud had merged with the white slopes of the mountain to create the optical whiteout phenomenon. To an inexperienced observer, whiteout renders a snow-covered sloping surface invisible. Thus the mountain slopes ahead of the aircraft, with which it collided, would not have been apparent to the flight crew.
The change to the McMurdo coordinates was known to Mr Chippindale, as well as being the subject of very close scrutiny at the Royal Commission of Inquiry. In his report in June 1980, Mr Chippindale found the probable cause of the accident to be "the decision of the captain to continue the flight at low level toward an area of poor surface 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".
The Royal Commissioner rejected the contention that the crew were uncertain of their position. He found that below minimum safe altitude they were entitled, as a means of determining their position, to rely exclusively upon the "unerring accuracy" of the AINS, and their understanding that it was programmed to fly a route down McMurdo Sound. He concluded 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", and that the pilots were in no way responsible.
In his latest article (NZ Herald, 3 March 2012), Mr Holmes calls the Chippindale Report "reprehensible", and describes its conclusion that the pilots did not know where they were as "wrong on all counts". This is self-evident nonsense. If the pilots had known where they were (as distinct from where they thought they were), there would not have been an accident. Mr Holmes makes the same mistake as the Royal Commissioner by refusing to accept that good airmanship required independent confirmation by the crew of the aircraft's actual position prior to descent below minimum safe altitude, notwithstanding their pre-flight understanding of the flight plan track and their apparent high degree of confidence in the accuracy of the AINS.
Several means were available to the accident crew by which to establish their true position. They could (and should) have done what Captain Simpson had seen fit to do on his flight, namely to relate the actual McMurdo coordinates entered into the AINS to a topographical map. In his case, that very straightforward exercise confirmed his understanding that the McMurdo waypoint was at the head of McMurdo Sound. Had the accident crew done the same during their flight, they would have been alerted to the mismatch in the McMurdo waypoints. The crew also had at their ready disposal a continuous readout of the aircraft's latitude and longitude. Relating that information to a map would have revealed that the aircraft was not over the flat sea ice of McMurdo Sound, but to the true north of the high terrain on Ross Island.
Mr Chippindale was not alone in his view of the cause of the accident. In civil proceedings brought by certain families of the deceased crew against the US Navy air traffic controllers at McMurdo, a US District Court considered the evidence in considerable depth. It had before it both the Chippindale and Mahon Reports. The court concluded that the air traffic controllers were not responsible for the accident, which it found was caused by a combination of the change in the McMurdo coordinates without telling the flight crew, and "the careless performance of the crew which did not avail itself of several available fail-safe systems, any one of which would have enabled it to discover in ample time that it was not on a proper course".
Over the years, experienced commentators, whose views count, have expressed opinions to essentially the same effect. The fact that the voices of opposition to the Mahon view have been drowned out by the wealth of publicity in its favour, especially in recent times, does not diminish their legitimacy. Nor can the opposing views be dismissed by attacking the integrity of those holding them, such as the disgraceful denigration of Mr Chippindale, viciously branded a liar, and no longer here to defend himself.
As I wrote last time, there is a natural reluctance to criticise the conduct of those no longer here to defend themselves, particularly in the tragic circumstances of this case. If, however, the events of more than 30 years ago are to be revisited in the public domain, the presentation must do justice to the facts. The basis on which Messrs Holmes and Dunne support their call to Parliament fails to meet this test.
And even if it did, what exactly is Parliament expected to say? That the Mahon Report on causation was right, and that Chippindale was wrong? By what legal mechanism is Parliament to arrive at that result? Is it to split out those parts of the Report that have been discredited by the courts, and effectively uphold the rest? How are individual MPs expected to do that? Would a majority in Parliament need to vote in favour? Or is this somehow to be pushed through by a willing minority?
In the final analysis that is all academic. There is no need for Parliamentary affirmation. The facts are the facts, no matter how valiant or eloquent the attempt to reinvent them. Trying to achieve closure for the loved ones of the flight crew, however laudable, should not be at the expense of those others, and their loved ones, also closely associated with the Erebus tragedy.
It is also inexcusable for Mr Holmes, in support of his cause, to perpetuate the myth that the most senior people in Air New Zealand were involved in a "breathtaking, scandalous, concerted process of cover-ups, coercions, obfuscations and simple bloody lies". The highest courts in the land have debunked those findings as completely without foundation, as did the New Zealand Police, who investigated them very thoroughly, and brought no charges. To maintain the allegations shows a contemptuous disregard of the decisions of the courts and reveals an appalling ignorance of the facts. It is also deeply offensive and hurtful for those still alive, and their families, who were so wrongly condemned by the egregious excesses of the Mahon Report.
Responsibility for the Erebus accident must be left to lie where it rightly falls, however painful that may be. It would be wrong for Parliament to take sides, all the more so were it to align itself with one that so defies objective scrutiny.
* Richard J McGrane was junior counsel for Air New Zealand at the Royal Commission of Inquiry in Erebus and in the subsequent court proceedings.
