Clues to Air France 447
An interesting take on what might have happened to Air France Flight 447: A Past Flight May Offer Clues to Air France 447.
Following an investigation of the A330’s uncommanded dive, Australian aviation officials, assisted by U.S. and French authorities, blamed a pair of simultaneous failures for the near disaster. The plane has three air data inertial reference units (ADIRUs), which are designed to help the plane’s flight-control computer fly the plane safely. The system is intended to eliminate the possibility of electronic error: the flight computer, which is always monitoring the trio, can disregard one ADIRU if it begins relaying information that conflicts with the other two.
But that’s not what happened when one of them went awry on October 7 and began sending erroneous data spikes on the plane’s angle of attack (AOA) - the angle between its wings and the air flowing over them - to the flight control computer. “For some reason the damn computer disregarded the healthy channels,” says Hans Weber, an aviation expert who heads Tecop International, an aviation consulting firm in San Diego. “Instead, it acted upon the information from the rogue channel.” The computer, responding to the faulty data, put the plane into a dive. (Read “Is There a Cause for Fear of Flying?”)
In its preliminary investigative report, released March 6, the Australian Transport Safety Bureau said Airbus had initially said that it didn’t know of any other similar events. But when the same thing happened again, involving a different aircraft on December 27, Airbus combed its computerized flight files and found data fingerprints suggesting similar ADIRU problems had occurred on a total of four flights. One of the earlier instances, in fact, included a September 2006 event on the same plane that entered the uncommanded dive in October (the other three flights had continued safely on). The same VCR-sized ADIRU was to blame in both those cases, although it had supposedly undergone a needed “re-alignment” following the 2006 event. All three planes carried the same brand and model of ADIRU, as do 397 of the 900 330s and 340s in the Airbus fleet.
It is not yet known whether Air France 447, an A330, carried the troublesome variety of ADIRU. But if it did, and if the Air France plane plummeted into an uncommanded dive while traveling through a downdraft generated by storms - a common occurrence over the region of the Atlantic Ocean where the plane went down - it could have been doomed as it entered a steep dive and likely broke up.
(Hat tip: CIA Reject.)
Frank says: