Graphic: search for flight AF-447

A French nuclear submarine began combing the Atlantic depths off Brazil yesterday in search of signals pinpointing the flight recorders that could explain why Air France Flight 447 crashed last week.

On board the Emeraude, crewmen called “golden ears” were straining to pick up in their headsets the acoustic pings aircraft black boxes are supposed to transmit for 30 days under water.

Nothing is better equipped for such faint sounds than an attack submarine with sophisticated sonar gear for detecting vessels deep in the ocean, naval officers said.

As the Emeraude, with 72 men aboard, worked with two US sonar-detecting vessels, the Brazilian and French navies continued to collect bodies and debris form the Airbus 330, which smashed into the Atlantic about 1,000 miles off Brazil with 228 people aboard.

More than 40 bodies have been plucked from the water and the first half-dozen were to be flown to Recife on the mainland for identification by fingerprints, body markings, teeth and DNA. Passengers’ belongings were also collected bobbing on the ocean surface and large fragments of the aircraft were being taken back for inspection.

The submarine is searching a zone where currents and winds are thought to have carried the crash debris. The French Navy was cautious about the chances of success in one of the most difficult searches ever tried. “There are uncertainties about the accident site. The ocean floor is rugged so it’s going to be very difficult and we’re going to need a lot of luck,” said Major Patrick Prazuck, the armed forces spokesman.

The submarine must pass very close to the boxes to have a chance of detecting them, he said. If the voice and data recorders are found, a French remote-controlled submarine will try to retrieve them with a robot arm. No flight recorders have been retrieved from the 12,000ft depth where those of Flight 447 are believed to lie.

In France, Air France pilots voiced satisfaction with the airline’s swift replacement of speed sensors on all its 35 Airbus long-range aircraft. Faulty readings by the external sensors — pitot tubes — are believed to have started the chain of events that led to the disaster.

Air France has said that its aircraft suffered a series of upsets in cruising flight over the past two years, which were caused by faulty speed readings and malfunctions in the automatic flight system.

All the clues to the Airbus’s fate have come from data transmitted during the last four minutes of its flight. An understanding of the disaster would be immensely improved with information from the flight deck voice recorder and flight data recorded on the black boxes.

Passengers had a scare yesterday when a Spanish-operated Airbus A320 made an emergency landing in the Canary Islands after suffering a failure in one of its two engines. The Iberworld aircraft, smaller than the A330, had just left Las Palmas to fly Norwegian tourists to Oslo when there was a jolt and the pilots turned round to make a safe landing. Some passengers said they had seen flames, but the airline did not identify the engine problem.

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