Pilots of the Air France flight from Rio de Janeiro to Paris that plunged into the Atlantic lost vital speed data just before the aircraft crashed, France's Bureau of Investigation and Analysis (BEA) said Friday.
The aircraft climbed to 38,000 ft when "the stall warning was triggered and the airplane stalled," the report says.
The investigation raises the question of why the pilots responded to the stall by pulling the nose up instead of pushing it down to recover, says CNN's aviation expert Richard Quest.
The speed displayed on the left primary flight display were "inconsistent" with those on the integrated standby instrument system (ISIS), the report says.
The aircraft experienced some "rolling" before stalling and then descending rapidly into the ocean. The descent lasted 3 minutes and 30 seconds and the engines remained operational, said the report. It plunged at 10,912 feet (3,300 meters) per minute.
At the time of the descent, the two co-pilots and captain were in the aircraft cockpit.
Quest said: "For whatever reason the aircraft speed sensors failed and the A330 went into a high altitude stall. The pilot's actions were unable to recover the aircraft and some might say, made the bad situation worse.
"The actual falling from the sky will have been horrific. This plane fell out of the sky."
All 228 people aboard the Airbus A330 Flight 447 were killed on June 1, 2009.
The pilots lost contact with air traffic controllers while flying across an area of the Atlantic Ocean known for constant bands of severe turbulence.
Air crash investigators at the Paris-based BEA have been working on the theory that the speed sensors, known as pitot tubes or probes, malfunctioned because of ice at high altitude.
Since the accident, Air France has replaced the pitots on its Airbus fleet with a newer model.
The report quotes some of the pilot's conversation -- who were not named -- and reveals that they were aware of the upcoming turbulence and storm.
Four hours and six minutes into the flight, one of the co-pilots, referred to as PF, called the cabin crew, telling them that: "In two minutes we should enter an area where it'll move about a bit more than at the moment, you should watch out... I'll call you back as soon as we're out of it."
The report said that four hours and 10 minutes into the flight: "The autopilot [and] then [the] auto-thrust disengaged," and co-pilot PF said: "I have the controls." The report said the stall warning sounded twice in a row.
At four hours and 10 minutes into the flight the other co-pilot, referred to as PNF said: "So, we've lost the speeds." A second later the stall warnings sounded again the report said.
At about this time, "The speed displayed on the left side increased sharply," the report said. The aircraft was then at an altitude of about 37,500 ft.
The report said that at this time co-pilot PNF tried several times to call the captain back to the cockpit.
The aircraft then climbed to 38,000 ft and at around four hours 11 minutes and 40 seconds into the flight, the captain re-entered the cockpit. During the following seconds all of the recorded speeds became invalid and the stall warning stopped, the report said.
Co-pilot PF said "I don't have any more indications", and the co-pilot PNF said "we have no valid indications."
About a minute later co-pilot the PF said "We're going to arrive at level one hundred." This is a height of 10,000ft. About fifteen seconds later, the data recorder indicate "simultaneous inputs by both pilots on the sidesticks."
The recordings stopped at four hours 14 minutes and 28 seconds into the flight. A full investigation into the crash is expected next year.
Airbus, manufacturers of the A330, said: "The BEA's work constitutes a significant step towards the identification of the complete chain of events that led to the tragic accident. Airbus is committed to continuing to provide support to the BEA investigation with the objective of identifying all potential lessons to be learnt," according to the Press Association.
Earlier this week French air crash investigators said they would be able to identify two bodies recovered this month from the crash site. The recovery team is now working on retrieving all the bodies, French officials have said.
In early May search teams found the crucial "data recorders" from the wreck site, estimated to lie at a depth of between 2,000 to 4,000 meters (6,562 to 13,124 feet).
The aircraft climbed to 38,000 ft when "the stall warning was triggered and the airplane stalled," the report says.
The investigation raises the question of why the pilots responded to the stall by pulling the nose up instead of pushing it down to recover, says CNN's aviation expert Richard Quest.
The speed displayed on the left primary flight display were "inconsistent" with those on the integrated standby instrument system (ISIS), the report says.
The aircraft experienced some "rolling" before stalling and then descending rapidly into the ocean. The descent lasted 3 minutes and 30 seconds and the engines remained operational, said the report. It plunged at 10,912 feet (3,300 meters) per minute.
At the time of the descent, the two co-pilots and captain were in the aircraft cockpit.
Quest said: "For whatever reason the aircraft speed sensors failed and the A330 went into a high altitude stall. The pilot's actions were unable to recover the aircraft and some might say, made the bad situation worse.
"The actual falling from the sky will have been horrific. This plane fell out of the sky."
All 228 people aboard the Airbus A330 Flight 447 were killed on June 1, 2009.
The pilots lost contact with air traffic controllers while flying across an area of the Atlantic Ocean known for constant bands of severe turbulence.
Air crash investigators at the Paris-based BEA have been working on the theory that the speed sensors, known as pitot tubes or probes, malfunctioned because of ice at high altitude.
Since the accident, Air France has replaced the pitots on its Airbus fleet with a newer model.
The report quotes some of the pilot's conversation -- who were not named -- and reveals that they were aware of the upcoming turbulence and storm.
Four hours and six minutes into the flight, one of the co-pilots, referred to as PF, called the cabin crew, telling them that: "In two minutes we should enter an area where it'll move about a bit more than at the moment, you should watch out... I'll call you back as soon as we're out of it."
The report said that four hours and 10 minutes into the flight: "The autopilot [and] then [the] auto-thrust disengaged," and co-pilot PF said: "I have the controls." The report said the stall warning sounded twice in a row.
At four hours and 10 minutes into the flight the other co-pilot, referred to as PNF said: "So, we've lost the speeds." A second later the stall warnings sounded again the report said.
At about this time, "The speed displayed on the left side increased sharply," the report said. The aircraft was then at an altitude of about 37,500 ft.
The report said that at this time co-pilot PNF tried several times to call the captain back to the cockpit.
The aircraft then climbed to 38,000 ft and at around four hours 11 minutes and 40 seconds into the flight, the captain re-entered the cockpit. During the following seconds all of the recorded speeds became invalid and the stall warning stopped, the report said.
Co-pilot PF said "I don't have any more indications", and the co-pilot PNF said "we have no valid indications."
The recordings stopped at four hours 14 minutes and 28 seconds into the flight. A full investigation into the crash is expected next year.
Airbus, manufacturers of the A330, said: "The BEA's work constitutes a significant step towards the identification of the complete chain of events that led to the tragic accident. Airbus is committed to continuing to provide support to the BEA investigation with the objective of identifying all potential lessons to be learnt," according to the Press Association.
Earlier this week French air crash investigators said they would be able to identify two bodies recovered this month from the crash site. The recovery team is now working on retrieving all the bodies, French officials have said.
In early May search teams found the crucial "data recorders" from the wreck site, estimated to lie at a depth of between 2,000 to 4,000 meters (6,562 to 13,124 feet).
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