Science & Environment
12:28 pm
Mon March 31, 2014

Deep Sea Search and Recovery a Challenge Under Best of Circumstances

An engine from Air France flight 447, as photographed on the sea floor.
Credit Woods Hole Oceanographic Institution, Bureau of Investigation and Analysis (BEA)
Searching the vast ocean

The crash of Air France flight 447 was a best-case scenario for a deep sea search. The missing Malaysian Airlines flight is anything but.

On June 1, 2009, Air France flight 447 from Rio de Janeiro to Paris crashed into the middle of the southern Atlantic Ocean, killing all 228 people on board. The final report of the French Bureau of Investigation and Analysis found that a combination of mechanical failure and human error led to what must have been a terrifying three-and-a-half minute, 38,000-foot dive into the ocean.

But here's what the crash had going for it (if such a thing can even be said). The Airbus A 330 transmitted location and technical data until very shortly before the crash. And, because of the steep descent, it hit the water very close to its last known position. As a result, some wreckage and even bodies were recovered from the sea surface within days of the crash.

Still, it took two years - four search missions totaling months at sea - to find the complete wreckage, including the black boxes, atop a mid-ocean mountain ridge submerged under thousands of meters of water. The workhorses of the operation were three autonomous underwater vehicles, called REMUS 6000s, and the team that operates them. Together, they painstakingly mapped the seafloor in a 5,000 square mile search area using sonar and scoured the images for signs of wreckage.

The seafloor geography was one of the greatest challenges facing the search team. On their first deployment, two REMUSs actually crashed into the sides of underwater mountains, sustaining minor damage. Uneven and rocky terrain also made it harder to distinguish debris from rocks or other natural features. 

The plan for finding the missing Malaysian Airlines flight is essentially the same - narrow the search area, then deploy underwater vehicles to conduct sonar surveys, then recover the wreckage. International search teams are currently running down leads on debris spotted in the southern Indian Ocean by satellites, and the U.S. Navy has already sent one sonar mapping vehicle.

But the primary lesson learned from the Air France search is that deep ocean search and recovery takes time - a lot of it - and the international search team is nowhere close to ready to begin an underwater mission. Even if debris were confirmed to be related to the crash, oceanographers would have to use the plane's last known location, as well as data on winds and ocean currents, to back-calculate where that debris originated. Given the limited information on the plane's flight path and the length of time spent drifting since the crash, any such estimate would likely include a lot of wiggle room.

The notoriously bad weather in the southern Indian Ocean, and the fact that the southern hemisphere is approaching winter, are also likely to delay and prolong the search. And, depending where the search leads, complicated underwater terrain could also be a factor.

All told, Mike Purcell, the lead engineer on the Air France search team, says he's less confident now than he was two weeks ago about prospects for finding the Malaysian Airlines plane. But others say the imperative to find the black boxes and solve the mystery of flight MH 370 is so strong that the search will go on as long as necessary, even if that means years.

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