LE BOURGET, France The crew piloting a doomed Air France jet over the Atlantic did not appear to know the plane was in a stall, despite repeated warning signals, and never informed the passengers anything was wrong before the jet plunged into the sea, according to new findings released Friday.
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.
All 228 people were killed when the Airbus 330, en route from Rio de Janeiro to Paris, crashed as thunderstorms hit over the Atlantic on June 1, 2009. It was the worst accident in Air France's history.
The passengers were never told what was happening as Flight 447 went into an aerodynamic stall and then dived for 3 1/2 minutes into the sea, according to a summary of the BEA's latest findings released Friday.
The pilots themselves may not have been aware they were in the stall even as it was dooming the flight, the summary says.
The BEA will release a fuller report later Friday, based on cockpit voice and data recordings retrieved from the ocean depths in May in an exceptionally long and costly search operation.
The summary confirms that external speed sensors obstructed by ice crystals produced irregular speed readings on the plane. 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, according to the BEA.
Families of the victims have been eager to hear more about what happened; several met with investigators Friday morning at the BEA's headquarters in Le Bourget outside Paris.
"It's mainly the technical elements that we are missing," Robert Soulas, who lost his daughter in the crash, told AP Television News. "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 boxes' "talk" has allowed investigators to key in on the "precise circumstances of the accident" if not the exact cause, the BEA said.
This is the most extensive report by investigators to date. A final report is expected in early 2012.
In a statement, Air France said there was currently no reason to question the crew's technical skills. The airline said the report showed that a series of unlikely failures led up to the stall and crash, and said its pilots demonstrated a professional attitude and remained "committed to their task to the very end."
The airline 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 for the crash away from its pilots and onto the Airbus jet itself.
Among other recommendations from the BEA is equipping passenger planes with an image recorder that shows the instrument panel so that investigators can analyze what went wrong.
The captain was on a rest break when the warnings began. It's unclear why the co-pilot at the controls, 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 traveling too slowly.
A basic maneuver for stall recovery, which pilots are taught at the outset of their flight training, is to push the yoke forward and apply full throttle to lower the nose of the plane and build up speed.
This procedure, which can cause the aircraft to quickly lose several thousand feet of altitude, can be dangerous if the plane is near the ground. But with AF447 flying at over 35,000 feet, the risk of that would have been negligible.
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.
"I have the controls," the flying pilot said, according to the recordings.
The plane climbed to a maximum 38,000 feet before its brief but agonizing descent into the ocean while moving forward and with its nose tilted upward.
At 2:10.16, the co-pilot not flying said, "so we've lost the speeds" as the plane began its climb, reaching 7,000 feet per minute before the pilot flying nosed the aircraft down.
At 2:10.50, the co-pilot not flying tried several times to call the captain back from his rest as the stall warnings went off again this time for 54 seconds.
The captain arrived about a minute and a half after the autopilot disconnected, but seconds after he arrived, "all the recorded speeds became invalid and the stall warning stopped," the summary says.
At 2:12.02, both co-pilots said they had no more "valid indications" to fly by.
The recordings end at 2:14.08 4 minutes, 23 seconds after the first stall warning.
No announcement was ever made to passengers.