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French investigators say that Air France 447 experienced “a sharp fall” in airspeed while passing through a zone of turbulence, before the plane plunged 38,000 feet into the ocean.
In the final moments before Air France flight 447 stalled and began a terrifying 3.5-minute plunge into the Atlantic ocean off the coast of Brazil, the pilots lost critical speed data, a report by France’s aviation agency said Friday.
Information from the recovered flight data recorders shows “a sharp fall” in airspeed as the passenger jet flew through a zone of turbulence, according to France’s accident investigations bureau (BEA). It is the first official report on the Air France 447 air disaster, which killed all 228 people aboard when it crashed June 1, 2009 while flying from Rio de Janeiro to Paris. (read a PDF of the BEA report on AF447)
According to the BEA, the two co-pilots were flying the plane and at just over two hours into the flight, decided to turn slightly to the left to avoid a zone of turbulence while passing through an area of bad weather.
Two minutes later the autopilot disengaged, the instruments began showing "a sharp fall" in airspeed and the engine stall warning began to sound.
"We have no valid indications," one pilot said, according to information retrieved from the “black box” flight data recorders. When the airspeed dropped, the autopilot disengaged and the plane’s engines stalled.
The captain, who had left the cockpit to take a routine rest, returned but did not retake control of the plane.
"There was an inconsistency between the speeds displayed on the left side and the integrated standby instrument system (ISIS). This lasted for less than one minute," the BEA said in a statement following analysis of the recovered flight data recorders.
The plane climbed from 35,000 to 38,000 feet, but stalled and began to fall. It plunged at nearly 11,000 feet per minute, descending into the ocean in 3 minutes and 30 seconds. The plane’s nose was tilted up at a sharp angle, according to the last data on the recorder.
It is thought that there was a problem with the Airbus 330’s air speed sensors, known as Pitots, but there has been no clear conclusion. The report released Friday did not assign blame or suggest whether the Pitot tubes played a role.
The flight recorders were found along with bodies at 12,800 feet beneath the ocean in early May. A full report on the crash is due next year.