Tony Cooper: Significance of the Erebus whiteout

The Very Reverend Peter Beck, Dean of Christchurch conducts the service at the Koru memorial site to remember the 1979 Erebus crash victims. Photo / NZPA

Opinion

If a vehicle GPS tells a driver to head into a river and the driver does so, thereby wrecking the car, who is to blame? The GPS or the driver?

The driver could invoke the Nuremberg defence - "the GPS told me to do it and I was just following orders". That's a pretty lousy defence. The blame is surely due to the driver's overconfidence in the reliability of a device known to have the potential for error.

Computer errors have always been with us so it seems both naïve and negligent to place one's safety fully into the hands of the devices. A backup is required. Surely there is an obligation on the motorist to keep a good lookout.

Therefore when we read the reports on the Erebus disaster written by Justice Mahon, Paul Holmes and others we are puzzled by the self-contradictory nature of their case.

They say that on the one hand Captain Jim Collins was an extremely careful and meticulous pilot yet on the other hand that he was careless enough to let a computer fly himself into a mountain. This contradiction discredits their case. A better analysis is required.

We contend that Collins was not negligent and that, essentially, the computer error was not the cause of the crash.

The above authors claim that Collins believed that he was heading down the safe passage of McMurdo Sound because that was the route Air New Zealand had told him that the computer would be using. We claim that Collins was under no such illusion. He was smarter than that.

The reason lies in the accuracy of the Inertial Navigation System (INS). This device accumulates an error over large distances and Mahon points out that the error down at McMurdo may have been as large as 6 nautical miles (nm).

This means that the aircraft's true position may have been 6 nm to the left or right of the INS position. In other words the aircraft could have been anywhere in a band 12 nm wide (which is 22km). 22km is the distance from Glendowie to Te Atatu, almost the width of Auckland city. That is a huge margin of error.

But Collins knew of this possible error and knew that his location was vague. He also knew, due to his diligence, that the band width extended perilously close to Mt Bird.

So he acted prudently and never assumed that he was safely in the middle of McMurdo Sound. When he descended he did so in a region where he could see water all around and where he could keep a lookout for obstacles - this explains why he flew the figure eight pattern.

As it turned out his prudence was justified because the computer error added to the INS error put him outside McMurdo Sound. He made allowance for the errors therefore we are forced to conclude that the errors were not the cause of the crash as Mahon claimed.

The cause was the whiteout. If there had been no whiteout then Collins, after making a safe descent not assuming his location, would have seen that he was off course and corrected the computer error. But the whiteout hid the mountain and Collins did not see the location cues that he was expecting. To his credit he realised that something was wrong but without whiteout training his decision to climb out was a minute late.

Collins behaved carefully and meticulously and did not let the course errors put the flight at risk. The errors could not have caused him to crash. He would not have invoked the Nuremberg defence to defend himself had he survived. It is an insult to his reputation to invoke that defence on his behalf.

The course error was neither a necessary nor sufficient condition for the crash. The whiteout on the other hand was a necessary condition for the crash. And in the sense that it had caused many air accidents in the region without the presence of course errors it is probably a sufficient condition for a crash. Sooner or later a sightseeing flight at Antarctica was going to fly into a mountain even without computer errors because it simply isn't safe flying down there when you cannot see mountains. The terrain invisibility was an accident waiting to happen.

Having established that whiteout was the sole cause of the disaster we ask who is to blame? Specifically, it was the lack of whiteout training that caused the crash. With such training Collins would have known that it was not safe to descend below the cloud layer to establish his position. He would have turned around and headed home.

Whose fault is it that Collins had no whiteout training? It is beyond the scope of this article to decide. He was sent on a mission for which he was not qualified. It seems awfully negligent for an airline to send half a dozen pilots down to a dangerous region without appropriate training.

Having fixed up the incongruous insult that Mahon and others have made to Collins' reputation it seems that the case for his exoneration is now even stronger.

* Tony Cooper is an Auckland Quantitative Analyst; analyst@ddnum.com