Air France Flight 447 left Rio de Janeiro for Paris on the evening of May 31, 2009, with 216 passengers and 12 crew. A few hours in, cruising at 35,000 feet over the Atlantic, the captain left the cockpit to take his rest. Two copilots stayed at the controls.
Eight minutes later, at 2:10 a.m. UTC, ice crystals blocked the plane’s speed probes. The airspeed readings went wrong, and the autopilot, as designed, disconnected. Now the copilots had to fly it by hand.
The fault didn’t last. The speed on the left-hand display was wrong for 29 seconds, and the last of the three readings was back within about a minute.
The pilot flying reacted to the sudden handover with abrupt, oversized inputs, and pulled the nose up. The plane climbed and slowed. The stall warning sounded, and at one point kept sounding for 54 seconds straight. The plane reached about 38,000 feet and stalled.
The captain came back into the cockpit about a minute and a half after the autopilot disconnected. By then the plane was falling at roughly 10,000 feet a minute, nose pointing up. “I have no more displays,” the pilot flying said. Nobody in the cockpit put together what was happening. The BEA, France’s air accident bureau, later listed among the causes “the crew’s failure to diagnose the stall situation.”
Four minutes and twenty-three seconds after the autopilot let go, Flight 447 hit the ocean. All 228 people on board died. It took nearly two years to find the wreckage, 3,900 meters down.
The BEA’s report did not stop at the cockpit. It found that the pilot’s first excessive reaction could be explained by startle, “amplified by the lack of practical training for crews in flight at high altitude.” Pilots trained for stalls at low altitude, in the simulator, where they knew the warning was coming. At cruising height, where the margin is thin, they essentially never flew by hand. The copilots’ records showed they had not been trained to hand-fly an approach to stall, or recover from one, up there.
The machine that was supposed to make flying safer had also taken away the practice the pilots needed for the one night it gave up.