Ron Chippindale should not have redrafted the CVR transcript, but there’s very little difference between the two versions. The comment that’s always pointed to is “Bit thick in here eh Bert”, but no-one would attach any significance to such a comment, even if it was said.

The line in Chippindale’s report that he gets the most flak for is where he said there was no evidence that the crew were misled by the changed waypoint. Admittedly, it sounds ridiculous, given that the aircraft hit the mountain in nav mode at 1500 feet. What he neglected to mention was that he spoke to the three surviving pilots who attended the briefing and that they all said, according to Chippindale, that they believed the waypoint was at McMurdo Station (which is also what the briefing’s audiotape said). This is why he did not attach much significance to the changed waypoint.

Despite its deficiencies, Chippindale’s report covers all the bases. He identifies the captain’s error in going below MSA without confirming his position, but given the standard requirements for accident reports at the time, he went on to find the point in time when the accident became inevitable. Chippindale found that point to be when the aircraft levelled out at 2000 feet after completing the descending orbits. He could have spent more words on the subject, but he was basically 100% right. Mahon and Vette said that the crew saw a “false horizon”. That was rubbish. They saw no horizon, which is why the captain decided to go down to 1500 feet, to which the F/O responded “Yeah probably see further anyway”. Given the lack of visibility, the captain locked the aircraft back onto the nav track, as some sort of precaution, and flew on for 120 seconds before deciding to climb out. There was plenty wrong with that decision, as Gasman points out on another thread. The point is that he was flying VMC, and the AINS did nothing to improve his vision.

The only area in which Mahon was “learned” was ignoring facts that didn’t suit. He heard undisputed evidence that the inertial navigation system (“INS”) was not to be used to go below the minimum safe altitude (“MSA”), which, in most parts of the world, is 1000 feet above the highest terrain. That rule was not mentioned, either in Mahon’s book or in his report.

Captain Collins knew that he could not, in the vicinity of a 12000 foot mountain, descend to 2000 feet in reliance on the INS. In the absence of radar confirmation of his position, the only way he could go that low was if he was visual – so he solved the problem by pretending to be visual. Anyone who disagrees with the word “pretending” should read the transcript: “very difficult to tell the difference between the cloud and the ice”.

One of the reasons why the INS was not to be used to go below MSA was to prevent an “administrative blunder in Auckland” becoming an “awesome disaster in Antarctica”. The system required various human inputs. The co-ordinates of the aircraft’s start position, which were displayed at the gate, had to be manually entered. The co-ordinates from the flight plan had to be manually entered. While in the air, the data could be altered manually. For example, a pilot might elect to by-pass a waypoint or to fly x miles to the left of the nav track. All of these manual inputs had the potential to cause an error. And the production of the flight plan also involved manual human inputs and therefore had the potential to create an error, which is exactly what occurred. The point is that the error would not have caused an accident if Captain Collins had followed the basic rule, that Mahon never mentioned: Don’t use the INS to go below MSA.

The function of the INS was to get the aircraft from one side of an ocean to the other, where the pilot would either be able to see where he was or to confirm his position using ground aids.  Given the requirement to stay above MSA, an error in the INS would be revealed before the aircraft got into danger. If Captain Collins had followed the basic rule, of which he was fully aware, the aircraft would have flown over the summit of Erebus, whereupon the radio would have sprung into life and the error would have been revealed. Instead, he broke another basic rule by flying visually when he knew he couldn’t see properly.

To avoid any further allegedly emotive language, I will leave things to Captain Gordon Vette, in his book “Impact Erebus”:

 “Like other pilots, Captain Collins had implicit faith in the DC10’s navigation system – implicit within the reservation of good airmanship, which means counter-checking where possible and never accepting it as infallible.” (page 87)

 “The Area Inertial Navigation System (AINS) was in its element on the Antartic flights. The vast, lonely stretch of southern ocean could offer no surface-based radio aids. Only within a 40 to 50 mile radius of McMurdo at the southernmost extremity of the track, would those aids become available. The AINS would guide the machine accurately – within a mile each way of the track for every hour flown – until the aircraft descended to a low altitude, then the crew would fine tune its position using the ground aids. The AINS is relied on absolutely for cruising at altitude – it is the passage-maker. All the pilots who flew south spoke approvingly of the extreme accuracy of the AINS. Like the human mind, the system has one failing. Inaccurate information fed into it is acted on as if it were accurate.” (pages 87 and 88)

 “Like any good pilot, Collins would certainly have made up his mind that unless visual conditions were good, there was no way he would take the aircraft below Minimum Safe Altitude (MSA) of 16,000 feet. MSA constitutes a platform for pilots. Once below it they leave behind the self-sufficiency of the inertial navigation system and commit themselves once more to guidance from aids on mother earth, and to visual flying – ‘eyeballing’ it in pilot jargon.” (page 119)

 "Even with the granted accuracy of the inertial navigation system, no pilot should descend in instrument meteorological conditions beneath his minimum safe altitude until he is perfectly certain of his position. He can do this by checking with ground aids, or by visually identifying the terrain over which he is flying. Should he even look like straying into unclear weather at lower heights, he should fly out immediately – unless of course his position can be monitored exactly with ground radio aids or radar.” (page 169)

 “The AINS must not be used in Instrument Meteorological Conditions (IMC) below MSA.” (page 210)

 Given the above, how could Vette have supported Mahon’s finding that the crew was blameless? Vette accepted that below the cloud layer, the pilot wasn’t visual. What, then, does Vette say about the captain’s visual descent below the cloud layer?:

 “Collins and crew (and in fact almost everyone who gave evidence at the inquiry except the scientists) believed that the only way you could collide with terrain was to fly into cloud and suffer reduced atmospheric transparency or visibility.” (page 173)

 Contrary to what a reader of Vette’s book might think, he was not the first person to discover the phenomena of sector whiteout. It had been known of for decades, and there’s nothing particularly complicated about it: If two things look much the same, it’s hard to tell them apart. The slight problem with Vette’s assertion about what the captain believed is that it is completely and demonstrably wrong. After being given the latest weather at McMurdo Station, the captain said that they would probably have to go elsewhere, the reason being that it was “very difficult to tell the difference between the cloud and the ice”. What did Vette say about that statement? Absolutely nothing, in common with Mahon, NZALPA, and all the other believers.  The reason for the lack of any reference to that part of the transcript, the accuracy of which was not disputed, was that it destroys any suggestion that the captain was without blame.

Out of context?  It’s the very context that makes it absolutely clear that he was NOT looking down and referring to what he saw at the time. Instead, he was thinking ahead. The difficulty in distinguishing cloud from ice is his stated reason for not going to McMurdo Station.

This pilot knew that he would not be visual below the cloud layer. He knew he could only go below MSA on instruments and he knew that the INS was not sufficient. He did not, at the time of his cloud/ice comment, know about the available ground radar facilities, so on receipt of the weather report, he correctly decided to bail out and go somewhere else.

The fact that the captain knew he would not be visual below the cloud layer is confirmed by what happened shortly after he decided to go elsewhere, when he was offered a radar-assisted descent. From the captain’s perspective, this changed everything, because he could have his position confirmed before going below MSA.  On receipt of the offer, the captain gratefully accepts it and then announces the plan to the passengers. If the captain believed that he would be visual below the cloud layer, the radar would have made no difference, because he could have gone below MSA with or without it.

Ten minutes later, without any discussion with the rest of the crew, the captain dived down below MSA through a hole in the cloud layer on the basis that he was visual. He  effectively decided to ignore his own warning and that decision has to be the primary cause of the accident. His decision to fly visually when he knew he couldn't see properly was not caused by any mistake made by the navigation section or any inadequecies in the briefing. It was caused by a very bad error that bordered on reckless.