Submarine at air crash scene to hunt black boxes

[June 10, 2009]  RECIFE, Brazil (AP) -- A French nuclear submarine reached the crash zone of Air France Flight 447 on Wednesday to join the search for the plane's black boxes, the key to determining what brought the Airbus down in the sea off Brazil with 228 people on board.

The attack sub Emeraude plans to trawl 13 square miles (35 square kilometers) a day, using sonar to try to pick up the boxes' acoustic beacons or "pingers," French armed forces spokesman Christophe Prazuck said Wednesday.

It's a race against time, because the beacons will start to fade 30 days after the May 31 crash. If the boxes are spotted, the Emeraude will work with the mini-sub Nautile, which can descend to the ocean floor and was a key part of the search for the Titanic.

"There are big uncertainties about the accident site, the ocean floor is rugged ... so it's going to be very difficult," Prazuck told France-Info radio. "It's going to be very complicated and we're going to need a lot of luck" to find the black boxes.

The French submarines will be aided by two U.S. underwater audio devices capable of picking up signals even at a depth of 20,000 feet (6,100 meters). One of those devices was being loaded Wednesday onto a ship off Brazil's northeastern coast.

A total of 41 bodies have been recovered so far from the scene of the crash, about 400 miles (640 kilometers) northeast of the Fernando de Noronha islands off Brazil's northern coast. The remains are being flown daily to Recife, where investigators hope to identify them and uncover clues into the crash based on the victims' injuries.

Prazuck told Associated Press Television News that a French frigate, the Ventose, had already gathered 130 pieces of debris, including big and small pieces. The debris was being desalted and was to be taken to an undisclosed location for further analysis, he said.

Without key information from the Airbus A330's missing data recorders, investigators have focused on the possibility that external speed monitors -- Pitot tubes -- iced over and gave false readings to the plane's computers as it flew into thunderstorms.

Airlines around the world have begun replacing Pitot tubes on their aircraft. And the European Aviation Safety Agency, responsible for the certification of Airbus planes, said it was "analyzing data with a view to issuing mandatory corrective action" following reports about the possible malfunctioning of the Pitot tubes. But it also said the A330 and other Airbus aircraft are safe to operate.

The Pitot monitors had not yet been replaced on the A330 that was destroyed en route from Rio de Janeiro to Paris.

The agency issued a safety information bulletin Tuesday as a precautionary measure reminding operators of the correct procedure if speed indications are unreliable or missing.

"We are aware of issues with this in the past, but at no time were they classified as safety-critical," said Daniel Hoeltgen, the agency's spokesman.

An important part of the investigation relies on a burst of 24 automatic messages the plane sent during the last minutes of the flight. The signals showed the plane's autopilot was not on, officials said, but it was not clear if the autopilot had been switched off by the pilots or had stopped working due to conflicting airspeed readings.

The L-shaped metal Pitot tubes jut from the wing or fuselage of a plane, and are usually heated to prevent icing. The pressure of air entering the tubes lets internal sensors measure the speed and angle of flight. A malfunctioning tube could mislead computers controlling the plane to dangerously accelerate or decelerate.

Air France said it began replacing the tubes on its A330 and A340 jets in May after pilots reported several incidents of icing leading to a loss of airspeed data, and that it had already replaced the Pitots in smaller A320 jets after similar problems were reported.

"What we know is that other planes that have experienced incorrect airspeed indications have had the same Pitots. And airplanes with the new Pitot tubes have never had such problems," said Air France pilot Eric Derivry, a spokesman for the SNPL pilots union.

On Tuesday, the airline assured its pilots that none of its A330s or A340s would fly without at least two of the new instruments, and that all Air France A330s and A340s will have all three Pitots replaced by July. Brazil's air force said it is replacing them for the president's jet.

About 70 airlines operate some 600 A330 planes similar to the doomed Air France jet, and two companies manufacture the Pitot monitors for them: France's Thales Group and Charlotte, North Carolina-based Goodrich Corp.

From Germany, more confirmation came Wednesday about rough weather over the Atlantic along the same route as the Air France crash. Lufthansa confirmed a report in Stern magazine that a passenger was injured when a Sao Paulo-to-Frankfurt flight hit turbulence off the Brazilian coast two days before the Air France crash.

"One can generally expect turbulence on this route," Lufthansa spokesman Michael Lamberty said Wednesday.

[Associated Press; By MARCO SIBAJA and EMMA VANDORE]

Charlotte Coulon of Associated Press Television News contributed to this report from Paris, Marco Sibaja reported from Recife. Other Associated Press writers contributing to this report included Federico Escher in Fernando de Noronha, Brazil; Alan Clendenning in Sao Paulo; Emma Vandore in Paris; David Rising in Berlin; Slobodan Lekic in Brussels; Eileen Ng in Kuala Lumpur; Adam Schreck in Dubai, United Arab Emirates; Harry Weber in Atlanta and Cecile Brisson in Paris.

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