Air France crash focus on speed; search hopes fade

PARIS/RECIFE, Brazil (Reuters) - Crews searching in worsening Atlantic weather on Friday faced the prospect they may never find bodies from an Air France crash, which may have been caused when the pilots acted on flawed speed readings.

Airbus, the maker of the A330 jet that crashed on Monday killing all 228 people on board, issued a warning late on Thursday that pilots should follow standard procedures -- to maintain flight speed and angle -- if they suspect speed indicators are faulty.

That reinforced an emerging theory that the experienced pilots operating the Rio de Janeiro to Paris flight may have inadvertently set the plane at a wrong speed as it passed heavy thunderstorms after leaving Brazil’s northeastern coastline.

Going too fast in turbulent conditions risks damaging a plane’s structure, while going too slow can cause it to stall.

Airbus said its message to clients did not imply pilot error or that a design fault caused the crash of Flight AF 447, the world’s deadliest air disaster since 2001 and the worst in Air France’s 75-year history.

“This Aircraft Information Telex is an information document that in no way implicates any blame,” Justin Dubon, a spokesman for Airbus, said on Friday.

More than 300 aircraft similar to the Air France jet -- an Airbus A330-200 -- are in service worldwide.

The French air accident investigation agency aims to release an initial report by the end of the month. But finding the evidence contained in debris and, crucially, in black box flight recorders is proving a monumental task.

France has sent a nuclear-powered submarine with advanced sonar equipment to help locate the black box and any other sunken debris, armed forces spokesman Christophe Prazuck said. But he said the black box may not be emitting the signal that allows it to be located.

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Mountains on the ocean floor, which is as deep as 3 kilometers (1.9 miles) below the surface, could block that signal, even if it is being transmitted.

“We have to take this chance and give it a go, but it’s a long shot. We need some luck,” he said.

Finding any bodies in the shark-infested area becomes less likely with each passing day. Three Brazilian navy ships have been scouring the area for more than a day but have not been able to fish out any of the plane’s debris.

“As the chances of finding survivors or bodies is becoming more remote, we are focusing on finding the debris,” Air Force Brigadier Ramon Borges Cardoso told reporters in Recife, the city on Brazil’s northeastern coast, where the debris will be gathered for inspection.

He said rain and low visibility hampered crews on Friday.

The wreckage spotted by Brazilian air force planes is spread over a huge area of ocean about 1,100 km (680 miles) off the South American country’s northeastern coast.

Searchers believe the bodies may have sunk with a large part of the plane if it was relatively intact when it hit the ocean, military sources said.

Brazilian President Luiz Inacio Lula da Silva called for a minute of silence for the crash victims at the start of a televised speech on Thursday.

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French magistrates have opened an investigation into possible manslaughter over the crash, the prosecutor’s office said on Friday, a routine procedure after such a large loss of life. It could take years to complete.

Investigators know from the aircraft’s final batch of automated messages, which were sent over a three-minute period, that there was an inconsistency between the different measured airspeeds shortly after the plane entered a storm zone.

An industry official said warnings such as the one Airbus sent on Thursday are only issued if accident investigators have established facts that they consider important enough to pass on immediately to airlines.

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The recommendation was authorized by the agency looking into the disaster, which has said the speed levels registered by the slew of messages from the plane showed “incoherence.”

Investigators do not know if the plane was traveling at an incorrect speed as it crossed the storm cluster.

An aviation expert, who declined to be named, said the plane’s airspeed sensors, called pitot tubes, work on air pressure and might provide incorrect readings if they get obstructed by objects like ice.

The tubes are heated to prevent icing at high altitude and there was no immediate information on what went wrong.

Airbus said the correct procedure when confronted by unreliable speed indications was to maintain thrust and pitch and start trouble-shooting.

The Airbus telex has revived a long-standing debate among pilots over whether the Airbus planes are overly complex.

“This is a plane that is conceived by engineers for engineers and not always for pilots,” Jean-Pierre Albran, a veteran pilot of Boeing 747s, told Le Parisien newspaper.

“For example, on a 747 the throttle is pushed by hand. You feel it move in turbulence. On recent Airbuses, this throttle is fixed. You look at the dials. You don’t feel anything.”