By Gerard Bon
PARIS (Reuters) - A French nuclear submarine with advanced sonar equipment began searching on Wednesday for the flight recorders of an Air France airliner that crashed into the Atlantic last week, the French military said.
The Emeraude was sent to the area to hunt the "black box" recorders, which may help explain the disaster and which are believed to lie on the ocean floor.
Investigators face a long search for clues to what went wrong when the Airbus A330 jet disappeared on a flight from Rio de Janeiro to Paris killing all 228 people on board, French military spokesman Christophe Prazuck said.
"Up to now, the time frame for the search for victims and debris has been of the order of days or a week. Here, at the very least, it's going to be of the order of weeks or months," he told LCI television.
The Air France flight is believed to have run into trouble when it hit a violent storm midway over the Atlantic Ocean and potential problems with speed sensors have become one of the focal points of the inquiry.
The European Aviation Safety Agency said on Tuesday it issued a reminder to pilots on how to proceed when they suspect airspeed readings are unreliable.
It said it was analyzing speed sensor data "with a view to issuing mandatory corrective action." The agency added it would not prejudge the outcome of the investigation and reiterated that Airbus planes are "airworthy and safe to operate."
Late on Wednesday, Airbus denied a report in an early edition of French daily newspaper Le Figaro that it was considering grounding its fleet of A330 and A340 planes following the crash.
"We are not considering grounding the fleet because it is safe to operate," said Airbus spokesman Stefan Schaffrath.
Other causes have not been ruled out, but France's interior ministry said two passengers identified as suspicious turned out not to be a concern. The website of the French weekly L'Express had quoted a French military spokesman as saying they could have been linked to Islamic terrorism.
WEATHER HAMPERS SEARCH
Brazilian military search teams using planes and ships had recovered 41 bodies by Tuesday, but none were found on Wednesday. Briefing reporters, Air Force Brigadier Ramon Borges Cardoso said visibility had been poor in the search areas.
Television pictures showed a military plane preparing late on Wednesday to fly the first 16 bodies found to Recife on mainland Brazil from the archipelago Fernando de Noronha off the northeast coast, where the search operations are based.
The 16 bodies had undergone preliminary identification procedures which would be continued in Recife.
Cardoso said the search for bodies would continue until around June 19, but could go on further if weather conditions and ocean currents were favourable.
Military planes expanded their search into airspace controlled by Senegal due to ocean currents that may have swept some bodies in that direction, Brazil's Air Force said, but searches there on Wednesday were interrupted by bad weather.
France has sent about 400 military personnel, three planes, one frigate with a helicopter, and a research vessel with mini-submarines as well as the nuclear submarine.
In the search zone, where scattered pieces of debris including a large section from the aircraft tail have been recovered, vessels are trying to comb a rugged area of the ocean floor, thousands of metres below the surface.
Prazuck said searchers had taken two weeks to locate the black box recorders after the crash of a Boeing 737 at Sharm el-Sheikh in Egypt in 2004, despite much easier conditions.
"Here the accident happened 1,000 kilometres (620 miles) from the coast. The situation is very complex," he said.
He said the Emeraude was searching an area of 36 square kilometres (14 sq miles) and the search zone would change daily. If the recorders are found, miniature submarines from the Pourquoi Pas, the French exploration and survey ship, could be used to retrieve them.
The doomed plane sent 24 automated messages in its final minutes on June 1, detailing a rapid series of systems failures.
The speed sensors that gauge how fast an aircraft is flying have become the focus of the investigation after some of the messages showed they provided inconsistent data to the pilots.
Air France said on the weekend it had noticed icing problems on the speed sensors known as pitot tubes in May 2008 and had asked Airbus for a solution. Airbus responded by reaffirming existing operating procedures, according to Air France, which decided to go ahead and change the sensors from April 27. The A330 that crashed had not yet been modified.
