The pilots of Air France flight 447 that crashed into the Atlantic Ocean three years ago lacked the right training to respond to a surprise scenario, the French aviation investigator said in its final report of the incident.
The investigation uncovered "profound loss of understanding" in the cockpit in a moment of surprise, when the aircraft went into a stall and lost lift, the report found. The pilots lacked training for stall scenarios, and the authority recommended that flight simulation training is reviewed.
"The dual failure of the expected procedural responses shows the limits of the current safety model," the French BEA authority said in its report. "The crew, whose work was becoming disrupted, likely never realized they were facing a 'simple' loss of all three airspeed sources."
The crash of the Airbus SAS A330 wide-body prompted a two- year search for the flight recorders to help determine why the plane disappeared, killing all 228 people aboard. The recordings revealed a state of confusion in the cockpit, with pilots not responding to stall warnings, highlighting a pressure point in modern aviation, where computers run most tasks and pilots are less trained in rapid crisis reaction.
Airbus, which helped fund the search for the recorders, has said that the aircraft responded flawlessly throughout its descent into the Atlantic Ocean. The pilots were required to take over the controls after the autopilot disengaged because of faulty speed readings caused by iced-up sensors. That occurrence alone could not explain a crash, Airbus has said.
"Without waiting for this final report, Airbus has already started working at industry level to further reinforce the robustness of pilot probes requirements and actively supports related activities," the aircraft manufacturer, based in Toulouse in southern France, said in a statement today.
A report last year that laid out the pilots' last minutes as they tried to get the situation under control pointed to confusion in the cockpit. That led France's air crash investigator to recommend better pilot training, particularly in cases where automated computers flying the plane get knocked out, forcing the pilot to command the aircraft.
Flight 447 crashed on June 1, 2009, en route to Paris from Rio de Janeiro. The disaster remained shrouded in mystery until the recorders were retrieved. It is unusual for modern aircraft to crash during their high-altitude cruise, as most accidents occur on takeoff or landing. Air France has defended its pilots, saying confusing cockpit readouts are partly to blame.
The flight-recorder readings revealed that Chief Pilot Marc Dubois, 58, had been on a routine break when the autopilot disengaged, and that he at no point until the crash took back control of the jet. Instead, the two junior co-pilots, aged 37 and 32, shared the task of stabilizing the plane, with the senior pilot giving occasional commands from the background.
"The occurrence of the failure in the context of flight in cruise completely surprised the crew of flight AF447," today's report said. "The apparent difficulties in handling the airplane in turbulence in high altitude resulted in over- handling in roll and a sharp nose-up input" by the co-pilot, the report said.
Aviation safety specialists have said the trio were probably bewildered by erratic instrument readings and may have done the opposite of what was needed to keep the jet from crashing. The pilots had only three and a half minutes to avert disaster as the jet fell toward the ocean at a speed of 180 feet (55 meters) a second.
"The startle effect played a major role in the destabilization of the flight path and in the two pilots understanding the situation," today's report found.
Pilots are trained to avert stalls, which occur when an aircraft slows enough that its wings lose lift, by dropping the nose to increase speed. Instead, the flight data showed that the pilot at the controls for most of the last minutes consistently angled the jet nose higher.
Airbus, which like Air France is partly owned by the French state, has said the flight-recorder readings support the technical flawlessness of the wide-body aircraft. Air France has called "misleading" the fact that the stall warning alarm went on and off repeatedly as the plane moved in and out of stall, responding pilot directions in the cockpit.
Lack of Comprehension
The pilots showed "total incomprehension of the situation," even as a stall alarm blared continuously for 54 seconds before the jet hit the ocean in the middle of the night, the BEA said last year.
Still, regulators should require specific pilot training on high-speed stalls, which isn't currently mandatory and which neither of the Air France co-pilots had received, the previous report said. That report also called for manufacturers to consider making available a reading of the so-called angle of attack, which defines the angle between air flow and the longitudinal axis of the aircraft.
In the case of the crashed Airbus, the angle, which wasn't visible to the pilots, always remained above 35 degrees during the descent.
"The problem is that one can't always rely on automatic functioning," BEA Director Jean-Paul Troadec said at a press conference in Paris. "Be it a modern or a more traditional plane, pilots need to know the situation they're in to react the proper way."