All things being equal, the simplest solution tends to be the best one
Ockham’s razor
THE axiom above, attributed to the 14th century English logician William of Ockham, states that the explanation of any phenomenon should make as few assumptions as possible, eliminating, or “shaving off”, those that make no difference in the observable predictions of the explanatory hypothesis.
In other words, when multiple competing theories are equal in other respects, the principle recommends selecting the theory that introduces the fewest assumptions and postulates the fewest hypothetical entities.
It is perhaps apt to apply this to the speculation surrounding the events of August 14, 2005, when a Boeing 737 jet crashed into a hillside at Grammatikos, killing all 121 people on board.
To many in the aviation industry, the verdict of the accident report would seem to adopt a warped version of Ockham’s approach: go with the simplest answer, chucking out “unnecessary” assumptions.
Now, according to Akrivos Tsolakis’ report, the primary cause of the crash was human error: the two pilots had failed to notice during checks before and after takeoff that the cabin pressurisation mode selector was in the manual position. The data suggests that the Helios ground engineer had set the selector on manual the night before the flight, following a pressure leak test. Had the switch been set to automatic, it would have allowed the cabin to pressurise by itself.
After take-off, the plane did not pressurise and the two pilots failed to recognise “the warnings and reasons for the activation of the warnings”, including a cabin altitude warning horn and the dropping of oxygen masks. Presumably, that is because the sounds emitted for takeoff configuration and cabin altitude warnings are identical.
The steady loss of cabin pressure led to the onset of hypoxia (oxygen deprivation), causing the pilots and passengers to pass out. The jet flew on autopilot for hours before it ran out of fuel and smashed into the ground.
But some feel this explanation is far too simple, almost conveniently so. Others flip the argument on its head: the theory fits perfectly, and is backed up by the data. The answer’s staring you in the face, they say.
David Learmount, Operations & Safety Editor for Flight International, adheres to this latter standpoint.
“Is it credible that the pilots did not carry out the pre-flight and the after-takeoff checklists? Well yes, it is. Based on my experience, these things are entirely possible.”
Yet given the plane’s tainted history – including a serious decompression incident in December 2004 – how plausible is it that the pilots were not versed in these problems? Indeed, it’s more than likely that the two aviators had flown the actual jet – together or separately – on past occasions. So what are the chances the problem of August 14 2005 snuck up on them, catching them completely unawares?
“Look,” says Learmount, “from the information we have, it’s clear that this was not an ideal crew to work as a team. And believe me, it’s not the first time that the co-pilot sits around, his arms folded, waiting on the captain’s cue.
“This is precisely what Tsolakis pointed out in his report: the absence of proper crew resource training at the airline. We’re not saying the pilots were total incompetents or clueless. We’re saying they made mistakes, but actually they were victims themselves – victims of Helios’ practices.
“The report says the aviators assumed there was something wrong with the takeoff configuration warning, and not pressurisation. This fixation with a preconceived idea is often the cause of crashes or near misses. How else to explain that they kept climbing, instead of levelling the plane or returning to base? It’s obvious: they never realised the plane was losing pressure.”
In December 2004 incident, the fated plane, the Olympia, was bound to Warsaw from Larnaca. It returned to Larnaca after decompression in the cabin, and was grounded for a week while inspectors got to work.
The subsequent technical log read “NFF” – No Fault Found. In other words, engineers had looked at the plane and found nothing wrong with it. The plane was cleared to continue flying.
So, should the jet have been recalled or grounded for good? What is standard practice in the aviation industry?
“If it says NFF, then you have done all you can. There’s no reason to stop the plane from flying,” offered Learmount.
Moreover, Learmount said Boeing had not contested any of the technical aspects of the accident report. The Mail has independently confirmed this.
“It’s important to remember that accident reports never claim the absolute truth. Their purpose is to state the probable cause.
“Bottom line: we’re as close to the truth as we’ll ever get,” he said.
“Sure there are grey areas,” he added. “There almost always are. But the Tsolakis report is a
good one.”
