3.5 Minutes of Terror: Speed Sensor Failure Led to Air France Crash

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The AF447 black boxes are displayed on May 12, 2011, at the BEA headquarters near Paris.

According to an official report, the pilots couldn’t reclaim control as the plane dropped out of the sky at a rate of 10,000 feet per minute. 

France’s Bureau of Investigation and Analysis (BEA) released the findings [PDF] from the flight’s black boxes, which were found intact at the bottom of the Atlantic in early May. And their analysis paints a harrowing picture of Air France flight 447’s literal dropping out of the sky.

(PHOTOS: See the flight resting at the bottom of the Atlantic)

Having departed from Rio de Janeiro bound for Paris, the co-pilots encountered trouble with the speed sensors four hours and 10 minutes into the flight. The flight was on autopilot as the pilot in command took a routine rest out of the cockpit. They were knowingly headed into a turbulent and storm-ridden spot over the Atlantic, and the black boxes show the pilots attempted to maneuver around the storm slightly.

It was at this point, after autopilot turned off and they worked to change their course, that a stall warning sounded, meaning that the airplane wasn’t generating enough lift. The report notes the co-pilot grabbed the controls and lifted the plane, which, according to aviation experts is contrary to normal procedure during a stall, when the nose should in fact be lowered.  During the lift, the speed sensors plunged then spiked in an apparent malfunction, the report shows. “So, we’ve lost the speeds,” the co-pilot noted.

For nearly a minute, as the speed sensors jumped, the pilot was not present in the cockpit. By the time the pilot returned, the plane had started to fall at 10,000 feet per minute while violently rolling from side to side. But the BEA notes the crew acted in accordance with all procedures, frantically attempting to command the plane as it pitched and rolled in the sky. The plane’s speed sensors never regained normal functionality as the plane began its three-and-a-half minute freefall.

The report shows the flight remained stalled throughout the drop, with its nose pointed up 15 degrees in response to the pilots’ attempt to generate lift. The flight plunged into the Atlantic nose-up, killing all 228 on board.

The findings coincide with investigators’ earlier theory that the sensors, known as pitot tubes, malfunctioned, possibly because of ice at such a high altitude. The BEA plans to release a full report next year, including the cause of the crash, which is still under investigation.

(BRIEF HISTORY: Black Boxes)