French nuclear submarine on hunt for black boxes

France's Emeraude nuclear submarine is searching the crash site of Air France flight 447 off Brazil's coast to locate the plane's black box flight-data recorders. It is the first time France has deployed a military submarine on a civilian search.


Eleven days after Air France flight 447 from Rio de Janeiro to Paris vanished suddenly in a storm and crashed into the Atlantic Ocean, the underwater search for the plane’s two black box flight-data recorders is moving forward at full speed.


A French nuclear submarine, the Emeraude, joined the search crews 1,100 kilometers (700 miles) off Brazil’s northeast coast. Equipped with highly sensitive sonars, its mission is to locate the ultrasound emissions sent out by the black boxes over a 200,000-square-kilometre (77,000-square-mile) area. This is the first time France has deployed a military submarine on a civilian search mission.


If undamaged, the boxes -- in reality a bright orange color -- will have saved the flight’s digital data and voice recordings, which investigators hope will shed light on the sequence of events that led to the jet's deadly crash.


Aviation Week expert Pierre Sparaco told FRANCE 24 that the boxes are “designed to resist extreme conditions” such as high temperatures, fire and underwater pressure, but are not infallible. “If their hermetic shells resisted the crash, their contents can remain intact for over a year,” he said.


Not designed to float


A French research vessel is also expected to arrive in the area on Thursday, carrying deep-sea miniature submarines that can be used to recover the black boxes if they are located. The devices are believed to be lying on the seabed as far as 6,000 metres (20,000 feet) below the surface.


The precious boxes are not designed to float because they are firmly wedged in the tail of the jet, the part that usually suffers the least damage in air accidents. “Sea crashes are very rare, so the boxes’ location is mainly designed to safeguard the recordings in case of land crashes,” former Air France pilot and director of Le Bourget Air and Space Museum, Gérard Feldzer, told France's daily Le Figaro.


Finding the black boxes could bring a crucial boost to an investigation that so far has very little to work with. “The Digital Flight Data Recorder keeps track of several hundred different parameters, from the flight’s speed and cabin pressure to each and every turn, climb, drop or maneuver executed from the cockpit,” Sparaco explains. The Cockpit Voice Recorder records the voices and noises inside the cockpit. Together, the two give a fairly precise picture of the flight’s itinerary, flying conditions and the overall atmosphere of the flight up until its final seconds.


'Almost mission impossible'


So far, the preliminary investigation, based principally on the 24 automatic distress messages emitted by the jet in the flight’s last minutes, have focused suspicion on the possible malfunction of the plane’s exterior airspeed sensors, known as pitot probes. But Sparaco said these suspicions are “guesswork at most”. He added that a sensor malfunction would be “just one of several elements” that caused the crash.


The black boxes’ pingers stop emitting ultrasound signals after 30 days, so rescuers are in a rush to find them. “Searching for a tiny signal in such a vast perimeter is already very difficult, but searching for the boxes once they’ve stopped emitting is practically mission impossible,” Sparaco said.


Rescuers have so far pulled out at least 41 bodies from the ocean. The first 16 reached the Brazilian archipelago of Fernando de Noronha on Monday and the other 25 are on their way to those islands, where they will undergo DNA identification tests. The AF 447 crash is the deadliest in Air France’s 75-year history.


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