December 15, 2011

I’ve always been fascinated by airplane crashes. Unlike car accidents, which are often blamed on driver (and thus human) error, airplane crashes are universally considered engineering failures, so the investigations are comprehensive stories about mechanical engineering, user interfaces, design, and psychology. In the two years since Air France 447 crashed in the middle of the Atlantic, I have been eagerly awaiting the official reports from the crash investigation. After finding the flight data recorder recently, the reports were finally completed and the true story began to emerge. From Popular Science’s fascinating article on the crash:

We now understand that, indeed, AF447 passed into clouds associated with a large system of thunderstorms, its speed sensors became iced over, and the autopilot disengaged. In the ensuing confusion, the pilots lost control of the airplane because they reacted incorrectly to the loss of instrumentation and then seemed unable to comprehend the nature of the problems they had caused. Neither weather nor malfunction doomed AF447, nor a complex chain of error, but a simple but persistent mistake on the part of one of the pilots.

Shortly after the initial airspeed sensor problem was solved by the plane’s built-in anti-icing systems, Air France 447 was a perfectly operational airplane. Every instrument was working correctly. It was flying at a safe altitude. If the pilots had pressed a couple buttons and re-enabled autopilot, everyone on board would have lived. But they didn’t. One co-pilot made a single, absurd mistake—for 4 minutes and 23 seconds—that brought the plane down.

This kind of human failure is pretty common; these kinds of seemingly stupid, impossible decisions are made all the time in catastrophic situations. I’ve seen panic set in when a startup’s servers have gone down, for example, causing the engineers to overlook something simple in their confusion. I’ve felt the crushing force when I’ve made huge mistakes.

Every time I read about or experience one of these situations, I am reminded of a story I read in The Checklist Manifesto about the emergency checklist for engine failure in a single engine Cessna airplane. The checklist has just six vitally important steps, including things like making sure the fuel valves are open and ensuring the backup fuel pump is turned on. But the first step is fascinating. It is simply FLY THE AIRPLANE. In the confusion of losing an engine, pilots often panic and forget the most obvious things they should be doing. It seems completely unnecessary, but this step ensures the best chance for survival.

The human body’s physical “fight or flight” response evolved to help it evade a dangerous situation, which historically involved extreme physical exertion. The rush of steroids into the bloodstream essentially turns off unnecessary systems, including some higher thinking processes, to aid in escape. Unfortunately, as we’ve evolved into more intelligent beings, that response hasn’t evolved along with us. The stress response is still optimized to prepare for a short period of extreme physical exertion, not for increased mental clarity. The result is painfully obvious with Air France 447: the co-pilot made an absurd error that no pilot in his right mind would make.

So, the next time you’re in a crushing situation, remember how irrational humans can be under stress, and remember to FLY THE AIRPLANE.

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Sources: second to last paragraph paraphrased from The Checklist Manifesto by Atul Gawande, an awesome book that you should read. The quoted section is from Popular Mechanics fascinating article about Air France 447.

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