US safety board probing Airbus A330 cockpit malfunctions

The National Transportation Safety Board on Thursday identified separate malfunctions on two different airlines that ended with safe landings over the past few weeks. They appear to describe the same type of malfunction -- triggering a loss of autopilot and automatic-throttle -- that investigators believe occurred on the Air France A330 shortly before it crashed May 31 en route from Rio de Janeiro to Paris in stormy weather.

Such airspeed issues aren't enough to bring down a jetliner. Investigators in the Air France crash suspect a combination of turbulent weather, possible computer glitches, pilot actions and perhaps other factors combined to put the jet into a fatal dive.

The safety board's disclosure partly reflects the fact that the A330's external speed-measuring devices -- called pitot tubes -- are under stepped-up scrutiny. The possibility of such malfunctions has been widely recognized and documented for many years, with Airbus and airlines developing backup procedures to safely fly aircraft.

But the NTSB's announcement underscores how such malfunctions, which can feed conflicting data to a plane's computerized controls, can result in more complex system failures and force pilots to fly without the usual cockpit automation. In one recent incident, the malfunction created a cascade of events that knocked out some primary flight-control instruments for as long as five minutes.

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