06.03.09 6:27 AM ET
Last Words of Flight 447: From a Robot
What happened, says aviation expert Clive Irving, was so sudden and so traumatic that the crew was disabled, perhaps unconscious from G-forces, leaving the computer to send a final burst of data.
The last person left alive on Air France Flight 447 seems to have been a computer. Accident investigators are baffled by the absence of any “Mayday” distress call from the pilots of the Airbus A330. But they do have data transmitted from the airplane as it was breaking apart. How was this possible?
Boeing and Airbus airliners have onboard computers that monitor and diagnose all the systems in real time—the engines, the power sources, integrity of the critical structures. But these were never intended to serve as guides to what may have caused a crash. They are there because they speed up maintenance—and more cost-effective.
It was several hours before the last piece of data was retrieved, at about the same time that it was established the airplane was missing over the Atlantic.
The Airbus system, called ACMS, or Aircraft Condition Monitoring System, picks up during a flight any new fault that needs attention when the airplane reaches its destination. On the ground, the mechanics have spare parts ready, and know what to look for. That allows a flight to be up and away again without delay.
When Flight 447 was stricken, the ACMS system apparently sent a final burst of data—first to a satellite and then to the Air France maintenance center in Paris. It was, according to reports, several hours before this data was retrieved, at about the same time that it was established the airplane was missing over the Atlantic.
From this, one chilling picture emerges: of a failure so sudden and so traumatic that the crew are disabled, perhaps already unconscious from violent G-forces.
The ACMS system, however, has a few more seconds of life and transmits. This does not, of course, describe what failed and why. Sudden events are usually of several kinds: an explosion triggered in a fuel tank by a spark or short circuit; a catastrophic decompression of the cabin, where the air is pressurized at the equivalent of an altitude of about 6,000 feet but where the outside pressure is far lower, so it pops like a burst balloon; or a structural failure, perhaps caused by extreme turbulence. There is also the possibility of a bomb, like the one that brought down the Pan Am 747 over Lockerbie, Scotland. This is being discounted because it is not consistent with the ACMS’ indication of an electrical failure—and because of the violent electrical storm reported at the time.
A final answer can come only from the black box, wherever in the ocean it now lies. In the meantime, the data from the ACMS, the robust robot, is all there is.
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Clive Irving is senior consulting editor at Condé Nast Traveler, specializing in aviation.