I do not understand the following paragraph in the website: "The vertical path - Discussion of the aircraft’s flight path would not be complete without consideration of the vertical aspect of the path. The minimum safe altitude over Mt Erebus was 16,000 feet. Descents below this altitude could only be conducted visually, that is clear of clouds and with good visibility, or by radar from McMurdo air traffic control. The former was used, although to be absolutely correct the aircraft should have requested, and been cleared for, a “visual approach.” Instead, the clearance was for a “descent maintaining VMC,” which means “visual meteorological conditions,” that is, clear of clouds and with good visibility. Since the requirements for maintaining VMC are similar to those for a visual approach this anomaly was not a factor in the accident."

I agree that MSA was 16000 feet and I agree that descent below MSA could only be VMC or with radar. But I definitely do not agree with the phrase "The former [ie, VMC] was used". It would be more correct to say the "The former was cited by the captain as the basis for the descent."

Visual meteorological conditions did not exist between the cloud and the ice, and the captain knew it. How can any pilot, private or professional, be justified in descending below the cloud and below MSA in those circumstances?

There is something very strange going on here, because we have professional pilots divided into two completely separate camps over some of the most basic principles of airmanship.

 

It appears that the majority of NZALPA members support the exoneration of the crew, on the basis that they were not at fault in any way. Then there are those on my side of the fence, who place all the blame on the crew. Where there is nothing wrong with the aircraft, the crew will usually bear some of the responsibility, the question being how much. But in this case, the choice is between 100% or 0%. There’s no middle ground.

 

Before reading ‘Daughters of Erebus’, I was a middle grounder, the main reason being that the crew was not briefed on the danger of flying visually below cloud. But I always wondered about that comment made by the captain at the beginning of the transcript. And now it transpires that the captain and one of the first officers attended a briefing at Operation Deep Freeze. For me, that has to be the end of the VMC argument. The descent below MSA was made in instrument meteorological conditions.

 

So everything boils down to whether the IMC descent was justified. Although a radar assist was proposed, the crew were unable to contact the ATC (which might be why the captain decided, wrongly, to make a visual descent).  There was a TACAN available, whose distance function could have been used as a cross-check, but its signal was not being received. That leaves the Area Inertial Navigation System.

 

In Paul Holmes book, he emphasises the accuracy of the AINS. Judge Mahon did much the same in his report, and I assume that this is also the basis for NZALPA’s position. But the AINS was not an approved instrument for a landing approach or any other descent below MSA. I didn’t think there was any argument about that. The DC-10’s AINS was a top-of-the-range three platform system, which was remarkably good at its job, which was to get the aircraft from an area on one side of the Pacific to an area on the other. But once in the area, the aircraft’s position had to be confirmed before going below MSA. Why was the AINS not sufficient confirmation? First, because it tended to ‘drift’ the longer it went with a ground update, and second, because it could be wrong. A waypoint might have been entered incorrectly – or a pilot attempting to change a waypoint or punch an offset might do so incorrectly – or the navigation section might have changed a waypoint and forgotten to tell the crew.

 

I do not know whether this might have anything to do with things, but it should be noted that GPS was not available in 1979.

Regrettably, another bald assertion without any argument.

As a method of debate, that makes about as much sense as repeating the same statement over and over, which is a method that Retired employs on another thread.

If Retired is someone who actually knows what he or she is talking about and is not a bored sixth former with internet access, what parts of the post are "wrong in very basic Airline terminology."?