(August 2011) After the nearly miraculous retrieval of the black boxes from Air France Flight 447, the Airbus A330 that disappeared in the mid-Atlantic in May 2009 with 228 souls aboard, it quickly became apparent that the events that led to the crash, until then magnified by the lens of mystery — a monster storm? a freak structural failure? a runaway computer? — had been quite mundane. Basically, what happened was that the autopilot had turned control of the airplane over to the pilot, who first stalled it and then held the stick back for almost three minutes while descending at more than 10,000 fpm to the ocean.
That a discrepancy among the airplane’s three pitot tubes had caused the autopilot and autothrottles to disengage was already suspected from maintenance-related messages robotically transmitted by the airplane’s computers before the crash. The recovered black boxes, their data intact, told a good deal more. The airplane had rolled to the right; the pilot leveled the wings and, in a simultaneous and possibly inadvertent motion of the A330’s quite sensitive sidestick, pulled the airplane up into a 7,000 fpm zoom climb from 35,000 to 38,000 feet. There, as the jet was momentarily in level flight with decaying airspeed and the nose above the horizon, the stall warning sounded.
Now, every pilot knows that to recover from a stall you must get the nose down. But because a fully developed stall in a large transport is considered highly unlikely, and because in IFR air traffic vertical separation, and therefore control of altitude, is important, transport pilots have not been trained to put the nose down when they hear the stall warning — which heralds, after all, not a fully developed stall, but merely an approaching one. Instead, they have been trained to increase power and to “fly out of the stall” without losing altitude. Perhaps that is what the pilot flying AF447 intended. But the airplane was already too deeply stalled, and at too high an altitude, to recover with power alone. As the airplane descended with the stick held back, autotrim dutifully cranked the stabilizer to its most negative, airplane-nose-up incidence angle, where it remained until the end.
At one point the pilot briefly pushed the stick forward. Then, in a grotesque miscue unforeseen by the designers of the fly-by-wire software, the stall warning, which had been silenced, as designed, by very low indicated airspeed, came to life. The pilot, probably inferring that whatever he had just done must have been wrong, returned the stick to its climb position and kept it there for the remainder of the flight.
