The last official word in the crash of Air France flight 447 in June 2009 says malfunctioning sensors misled pilots who didn't understand they were in a stall, causing them to fatally pull the plane's nose up, instead of down. Better training, said the final report from BEA, the French air safety investigator, could have helped pilots understand the plane was stalling, not diving, despite the false readings from their instruments.
It's long been thought that the plane's autopilot switched off when it hit bad weather about halfway through its flight from Rio de Janeiro to Paris, and that pilots couldn't recover control. Air-speed sensors called pitot tubes are thought to have iced over, disengaging the autopilot. The wreckage showed the controls set to point the plane's nose up when it hit the water on its belly after a three-minute and 30-second fall, BEA said in its initial report last May.
The agency's new report, of which The Associated Press' Cecile Brisson has the most comprehensive coverage so far, says the pilots didn't understand they were in a stall, and pulled the plane's nose upward because they thought they were in a dive because they were getting false information from their instruments. Per Brisson:
Chief investigator Alain Bouillard said the two pilots at the controls never understood that the plane was in a stall. He said only a well-experienced crew with a clear understanding of the situation could have stabilized the plane in those conditions.
"In this case, the crew was in a state of near-total loss of control," he said.
A stall happens when air doesn't move fast enough over the plane's wings to create lift. In order to recover control, the pilots should have pushed the nose forward to increase the plane's speed. Instead, they pulled back, slowing it down further.
It's important to note that while Thursday's report attempts to explain the crash through both pilot error and equipment failure, it doesn't assign blame. "The agency said its report does not examine the issue of responsibility for the crash, which is the subject of a separate judicial inquiry," CNN reported.