As details of the telemetry sent by Air France 447 in its final minutes become known, deep-sea technology experts are saying that the recovery of the aircraft's cockpit voice recorder and digital flight data recorder—the black boxes—will be difficult, but not impossible, with the help of deep-sea-diving robots.
After officials pinpointed the location of Air France's Airbus A330 crash site, they turned to the difficult task of recovering the black boxes, which hold the official recordings of events that happened before the plane went down. Black boxes, which are actually painted orange, can give investigators the missing bits and pieces of data needed to determine an accident's probable cause. To help officials find the boxes, embedded technology sends sonarlike signals, which can be detected for up to 30 days provided listening equipment can get within approximately 1 mile of the box, according to a spokesman for the National Transportation Safety Board. In the case of Flight 447, the crash area in the Atlantic Ocean is too deep for divers to reach.
In instances such as this, where the site is not accessible, side-scan sonar can be used to locate the boxes underwater and map the wreckage to guide remotely operated deep-sea vehicles (ROV) for recovery. The Brazilian navy, now on the scene, does not possess the equipment necessary to take on recovery, but sonar and robots are available through several other governments, oil companies, independent service contractors, and nongovernmental organizations, according to Al Bradley at the Woods Hole Oceanographic Institute in Massachusetts. On Sunday, Woods Holes' latest ROV, the $8 million Nereus, dove down 35,768 feet at the deepest surveyed point in the oceans, Challenger Deep in the Pacific's Mariana Trench. With this dive, the ROV became the world's deepest-diving robot. The highly maneuverable Nereus can be controlled by a fiberoptic connection or can swim autonomously when switched to a "free swimming" mode.
Flight 447's wreckage is likely to be "fairly open," resting on the ocean bottom, Bradley says, making the extraction of the black boxes a relatively straightforward task once the main structures have been located.
Still, because of the presumed depth, location and distribution of the wreckage — nearly 20,000 feet down in the pitching seas of the Tropical Convergence Zone across a miles-long debris field — recovery will be difficult:
"It comes down to how much money the French government wants to spend," Bradley says. Recovering and investigating a submerged wide-body airliner is expensive. The NTSB and the FBI spent $31.4 million on TWA Flight 800, which crashed off Long Island within sight of shore in 1996. While the French Navy said last night it was dispatching a pair of submersible ROVs to the crash site, the determination not to spend tens of millions of euros to recover the recorders may already have been made. France's counterpart to the U.S. NTSB, the Bureau d'Enquetes et d'Analyses (BEA), is the lead investigating agency for the crash. At a news conference yesterday, BEA head Paul-Louis Arslanian said he was not optimistic that the black boxes would be recovered. Last night the NTSB announced that it had accepted an invitation from the BEA to assist in the investigation. The U.S. team will also include technical advisers from the Federal Aviation Administration (FAA), General Electric and Honeywell.
The Airbus A330 with 238 aboard went down Sunday night over the Atlantic on a flight from Rio de Janeiro to Paris after encountering an area of strong thunderstorms, and telemetry suggests that the aircraft broke apart at altitude. A limited amount of floating wreckage was discovered by search-and-rescue aircraft Tuesday and Wednesday morning in an area 400 miles northeast of Brazil's Fernando de Noronha islands. Automatic telemetry sent by the Airbus over its Aircraft Communications Addressing and Reporting System (ACARS) satellite digital datalink to Air France's operations center indicates a cascading accumulation of critical aircraft systems failures that began approximately 3 minutes before the crash, immediately after encountering thunderstorms. The autopilot disengaged, the aircraft's fly-by-wire system was switched to alternate law (giving the pilot more direct control over the aircraft), flight-control alarms sounded; multiple faults were indicated for the Air Data and Inertial Reference Unit, the Integrated Standby Instrument System, Primary Flight Control Computer 1, and Flight Control Secondary Computer 1; and cabin pressure dropped.
By Mark Huber
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