Flight computers at heart of Air France crash?

As the search for the black boxes from Air France Flight 447 continues, some pilots are raising new concerns about the safety of the Airbus 330's computerized flight controls.

French and Brazilian authorities said Tuesday they will search for Air France Flight 447 as long as there is hope of finding the flight data recorders.

Several Brazilian military ships, a French submarine, and two Dutch ships towing high-tech US Navy listening devices are scouring the Atlantic for any signs of the pinger beacons from the flight data recorders, known as black boxes. The pinger signals weaken daily and are designed to last only another two weeks.

"We'll continue doing this until the moment that, technically, we determine the searches are useless," Nelson Jobim, Brazil's defense minister, told a Brazilian press agency today.

The black boxes hold data that can help unlock the mystery of what caused the Airbus 330 to apparently break up in flight and plunge into the Atlantic Ocean on June 1, during a flight from Rio de Janeiro to Paris.

Without that black-box data, lingering questions will fuel speculation about the safety of the A330 and other highly automated planes like it. Initial examination of some of the 49 recovered bodies indicates the plane broke up in flight, but there have been no signs of an explosion.

That's prompted a new round of concern among some pilots and aviation analysts that the plane's computerized flight controls may have malfunctioned, initiating a chain of events from which the pilots could not recover.

The reason for the concern is that A330 series jets have recently experienced a number of potentially disastrous computer anomalies. In one case, erratic computer commands caused an A330 to suddenly pitch nose-down until the captain could regain control, according to a report by the Australian Transport Safety Bureau [PDF]. That incident occurred in October on an A330 operated by Qantas Airways. The plane diverted to the nearest airport and landed safely, but 11 passengers and one crew member were seriously injured. A similar incident occurred on a Qantas A330 in December.

But other analysts and Airbus, which manufactures the A330, caution against such speculation, saying any parallels are superficial at best. The component responsible for the Qantas A330's erratic movements, a computer known as an Air Data Inertial Reference Unit (ADIRU), was made by a different manufacturer than the one installed in the Air France A330, says an Airbus spokesman.

But that explanation does not assuage some A330 pilots, who say they have experienced other unusual computer anomalies in their years in the A330 cockpit.

"The question isn't did the Air France plane have the same computers as Qantas, but [rather] could a computer fault bring down a modern jet?" one A330 pilot writes in an e-mail, who asked to remain anonymous because he is not authorized to speak to the press. "The answer is, yes, given the Airbus flight control system."

In the past week, speculation about what caused the crash has centered around Pitot sensors, small tubes at the front of the plane that send information about airspeed to the plane's various computers. At high altitudes, certain older Pitot sensors can ice up and produce inaccurate readings about a plane's speed. Just prior to AF447's disappearance, the jet's computers sent out a flurry of error messages that included inconsistent speed readings from the Pitot tubes. In the past week, Air France has replaced all the Pitot tubes on its Airbus 330s as a precautionary measure.

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