Search for Air France black boxes expected to continue

French investigators are expected to continue the search for Air France Flight 447's flight data recorders even after their 'pinger' signals fade in the next few days, perhaps with the aid of advanced sonar scans.

A Louisiana-based undersea mapping company, C & C Technologies, confirmed that it has been contacted by the Bureau d'Enquêtes et d'Analyses (BEA), the French investigation agency, regarding a "phase two" of the search effort.

The BEA sought information about using the company's computerized submarines – known as autonomous underwater vehicles – to scan the ocean floor. The Agence France-Press also cites BEA officials saying the search will continue beyond June 30, when the signals are expected to disappear, as long as it seems "a reasonable effort." BEA officials did not return Monitor calls.

The flight data recorders, known as black boxes, hold key information that can help explain what caused the Airbus 330-200 to apparently break up over the Atlantic Ocean on a routine flight June 1 from Rio de Janeiro to Paris. The black boxes emit an acoustic signal that makes them easier to locate, but the batteries that power them are designed to last only 30 days.

Currently, an international flotilla comprising French and Brazilian naval ships, a French nuclear submarine, a Dutch ship towing a US Navy signal locator, and several research vessels are scouring the ocean more than 600 miles northeast of the Brazilian coast.

Reports earlier this week suggested the black boxes' signal had been located, but the BEA later said the sounds were not from the flight data recorders. French investigators are said to be hoping the black boxes will continue to emit a signal beyond 30 days, but are reportedly also setting up contingency plans.

BEA officials contacted deepwater mapping company C & C Technologies to discuss initiating a "side-scan sonar" approach.

"It creates an acoustic picture of the [ocean] bottom to help find the debris, and hopefully, the flight data recorders," says Thomas Chance, president and CEO of C & C Technologies.

Historically, such undersea mapping was done with ships towing underwater equipment that emitted an acoustic signal that reflected off the ocean bottom to create a sonar image.

"What we're doing now is an autonomous underwater vehicle approach, where there is no cable between the underwater vehicle and the ship, and that allows the vehicle to go a lot faster … than you could with the older, towed systems," says Mr. Chance. This also makes it easier to navigate mountainous undersea terrain.

Aviation analysts say it's vital to find as much of the wreckage as possible, as well as the black boxes, to understand what caused the accident. "The great fear is that you get a plane that goes down and you don't know why," says Clint Oster, an aviation expert at Indiana University in Bloomington. Without that information, "we don't know how to try to reduce the chances that it will happen to another aircraft."

Analysts note that it's rare, even in ocean crashes, for black boxes to be lost. That's in part because most accidents occur either on landing or take off and so the wreckage is in relatively shallow water.

In this case, the ocean floor where the wreckage is thought to be has been compared to the Andes Mountains with depths ranging from two to three miles, making the search more difficult. But Chance says using the side-scan sonar approach with autonomous underwater vehicles makes success more likely, though it could still take several months.