The pilots of the Air France aircraft that crashed off Brazil may have fought to control their stricken aircraft to the end, because it was intact when it hit the Atlantic ocean, investigators indicated yesterday.

In a first report on the disaster that killed all 228 aboard, the French accident bureau said that the Airbus A330 of Air France Flight 447 had not broken up at altitude as reported earlier by Brazil.

Neither was it in a nose or tail-down dive. A study of 660 pieces of debris showed that it had shattered only when it slammed belly-first into the sea, said the bureau.

“The plane was not destroyed while it was in flight,” said Alain Bouillard, the chief of the investigation into the disaster which happened on June 1. “It seems to have hit the surface of the water in level attitude and with a strong vertical acceleration.”

Times Archive 1962: Crash pilot's protest before flight

The two major crashes of Air France airliners last month have aroused deeper than usual anxieties in France

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This could indicate that the crew had retained some control after the aircraft plummeted in little over four minutes from its cruising altitude of 35,000ft on its way from Rio to Paris, experts said. An aircraft falling belly first is likely to be in a stall or recovering from one. Aircraft diving fully out of control from high altitude usually break up before reaching the ground.

No passengers were wearing life-jackets so they had not been prepared for an emergency, said Mr Bouillard. There was no way of knowing if they were conscious when the aircraft hit the water. The Brazilian authorities so far have refused the investigators access to post-mortem examination results from the 51 bodies recovered from the ocean.

The investigators confirmed that the disaster began with faulty readings from the pitot speed sensors. This caused electronic systems to disconnect and left the crew with the task of hand-flying a handicapped airliner.

They said that it was too early to assign a cause to the crash, but their outline confirmed the sequence of events from a data transmitter on the aircraft that has been analysed widely by experts. The airliner was flying at night in a tropical storm zone that was not especially severe, said Mr Bouillard. The pitot speed sensors fed faulty readings to data computers. This in turn caused the automatic pilot and automated flight system to shut down, leaving the pilots to hand-fly the aircraft.

“This does not mean that the aircraft was not flyable,” said Mr Bouillard. “It means that it reverted to classical piloting.” Pilots expert in the A330 and A340 long-range Airbus family dispute the assumption that the aircraft was flyable. Piloting an airliner by hand at cruising altitude in turbulence at night without air speed data is extremely difficult, Cedric Maniez, an Air France A330 captain told The Times. The airline had simulated the conditions last week and experienced crew struggled to keep control.

The accident bureau said that the faulty pitot tubes were not the cause of the crash. “We can say that the pitot is strongly suspected of causing the incoherent speed readings. It is one of the factors but not the only one,” said Mr Bouillard. This was also the consensus in the flying world, where suspicion has fallen on the computerised systems of the Airbus. The long-range airliners have suffered at least three dozen similar failures involving faulty speed readings, it has emerged over the past month.

Lawyers for families of victims have said that there could be a flaw that would require all A330 Airbuses to be grounded. The bureau rejected this.

James Healy-Pratt, whose London firm, Stewarts Law, is representing two dozen families, said: “In our view the evidence still points to three factors — bad weather, questionable pitot tubes, and questionable functioning of the ADIRU [air data] computers.” Air France and Airbus are likely to face claims totalling about $500 million (£300 million) over the disaster,

Submarines and other vessels will continue until July 10 to search for the airliner’s two flight recorders on the ocean floor.

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