Faulty speed readings and electronic failures were cited by crash investigators yesterday as they said they were closer to understanding the loss of Air France Flight 447 on June 1, with the deaths of all 228 people on board.

Paul-Louis Arslanian, chief of the French accident investigation bureau, said that it was too early to pronounce on the events that led the Airbus A330 to crash into the Atlantic about 1,000km (600 miles) off Brazil, but added: “I think we may be getting closer to our goal.”His remarks strengthened suspicion among analysts that a bug in the computerised flight system of the Airbus could be the key to the disaster.

Brazilian and French searchers had by last night recovered 50 bodies and about 400 pieces of wreckage scattered over hundreds of square miles but a French nuclear submarine and other vessels have found no sign of the sunken flight recorders.

Mr Arslanian confirmed that “incoherent” speed readings were reported first in a series of alerts that the stricken aircraft transmitted automatically to Paris during its final four minutes. The other alerts “appeared to be linked to this loss of validity of speed information”. The faulty speed data affected other systems that relied on them, he said.

This would strengthen an emerging consensus in the aviation world that flaws in the electronics of the Airbus led to the loss of control. In the midst of a tropical storm, at night, the crew would have faced enormous difficulty in flying without basic flight information. A small variation outside the acceptable speed range would have put the aircraft into a stall or an “overspeed” condition from which it could not recover.

Similar incidents have been reported by Air France and other companies operating the airliner. The French airline rushed through the replacement of all the pitot tubes — the outside speed sensors — on its A330 fleet last week, after acknowledging a “significant” number of failures in recent months.

Blocked pitots alone would not cause the disaster, analysts have said, and suspicion has fallen on the electronics at the heart of the Airbus. Experts suspect a flaw in the behaviour of the three independent air data inertial reference units which collect raw flight parameters such as speed and altitude.

One such faulty unit was blamed for a near disaster on a Qantas Airbus A330 over Western Australia last October. Confused data caused the flight control computers to register — mistakenly — an imminent stall and to disconnect the automatic pilot. They commanded a strong downward pitch from which the crew, fortunately, managed to recover, although 14 people were injured.

Airbus, Air France and the European Aviation Safety Agency have all voiced full confidence in the Airbus and dismissed all theories as speculation. Nearly 1,000 of the aircraft are flying and until flight 447 none had been responsible for the death of a passenger.

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