They never informed the passengers anything was wrong before the jet plunged into the sea, killing all 228 on board, including five Britons and three Irish citizens.
Based on cockpit recordings from the crash, the French air accident investigation agency is recommending mandatory training for all pilots to help them fly planes manually and handle a high-altitude stall.
The Airbus 330, en route from Rio de Janeiro to Paris, crashed amid thunderstorms over the Atlantic on June 1, 2009. It was the worst accident in Air France’s history.
Passengers were not told what was happening as Flight 447 went into an aerodynamic stall and then dived for three and a half minutes into the sea, according to a summary of the BEA’s latest findings. The pilots themselves may not have been aware they were in the stall even as it was dooming the flight, the summary, released yesterday, says.
It confirms external speed sensors obstructed by ice crystals produced irregular speed readings. Since the accident, Air France has replaced the speed monitors on all its Airbus A330 and A340 aircraft.
The BEA says neither of the co-pilots at the controls had received recent training for manual aircraft handling or had any high-altitude schooling in case of unreliable air speed readings.
A stall warning sounded numerous times, and once for a full 54 seconds, but the crew made no reference to it in cockpit exchanges before the jet crashed.
There was no evidence of task-sharing during the crisis by the two co-pilots in the cockpit at the time, according to the BEA’s findings. The captain was on a rest break when the warnings began.
The BEA says it is unclear why the co-pilot, flying manually in what became the final minutes of the flight, maintained a nose-up input – contrary to the normal procedure to come out of an aerodynamic stall.
Normally, the nose should be pointed slightly downward to regain lift in such a stall, often caused because the plane is travelling too slowly.
Several of the families of the victims met with investigators at the BEA’s headquarters in Le Bourget outside Paris.
“It’s mainly the technical elements that we are missing,” said Robert Soulas, who lost his daughter in the crash. “It’s completely premature to accuse the pilots if we don’t know what situation they were confronted with.”
The reasons for the pilots’ apparent lack of reaction continue to elude investigators. But, the BEA said the boxes’ “talk” has allowed investigators to key in on the “precise circumstances of the accident”.
In a statement, Air France said there was no reason to question the crew’s technical skills.
The airline said the report showed a series of unlikely failures led up to the stall and crash, and its pilots demonstrated a professional attitude and remained “committed to their task to the very end”.
It also suggested the aircraft’s systems and alarms may have “hindered the crew’s understanding of the situation” during the stall, in comments possibly intended to shift some blame onto the Airbus jet.
Among other recommendations from the BEA is equipping passenger planes with an image recorder that shows the instrument panel so that investigators can analyse what went wrong.
At 2 hours, 10 minutes and 5 seconds into the overnight flight, the autopilot and then auto-thrust disengaged when the stall warning sounded twice. The co-pilot at the controls nosed the plane up.
The plane climbed to a maximum 38,000 feet before its brief but agonising descent into the ocean while moving forward and with its nose tilted upward.