by Michael Dessner

On the 1^st of June, 2009 an Airbus A330-203 carrying 219 Air France passengers lifted off at 7 PM in the evening from Rio de Janeiro, Brazil.  Three and a half hours later, about a third of the way to the destination city of Paris, the crew made their final radio call to controllers.  40 to 45 minutes later a series of messages were received by automated systems that indicated the plane had suffered a catastrophic failure of some sort.  A few long minutes after that, when the plane failed to make scheduled contact to the controllers in Africa, the search for AF447 began.

The initial phase of the search was massive, within 48 hours a Brazilian Naval vessel was on the scene and over the next few days it would be joined by four more.  The French National Navy sent four additional ships accompanied by a nuclear submarine as well as a civilian research vessel equipped with a submersible and Remote Operated Vehicle (ROV); two commercial tugboats also participated.  Passive underwater acoustic searches were made to listen for the frequency of the black boxes while operations were conducted on the surface to recover a relatively small amount of aircraft debris and a minority of the lost passengers.  The initial area in which the plane was supposed to have come down was halfway across the Atlantic directly over the Mid Atlantic Ridge, a submerged mountain chain and rift valley.  The peaks of the Mid Atlantic Ridge aren’t the highest in the world but the chain is easily the longest and largest on Earth and it marks the birthplace of the continents. This divergent plate boundary is constantly pushing the Americas and Africa/Europe away from each other at a rate of 1-5 cm a year.  The Mid Atlantic Ridge runs north to south for 10,000 miles, is at times 1,000 miles wide and mostly remains hidden under 8,000 feet of water.  It does rise precipitously in places however, as most mountains do, and in some places it even breaches the waves, most notably in the form of Iceland, some 4,000 miles from the missing plane’s final resting place.

Unfortunately for the families of the lost the initial search was unsuccessful.  The debris that was gathered on the surface of the ocean was not enough to define the nature of the tragedy and the black boxes were not detected within the 30 day time frame that they are expected to continue sending out their homing signal.  Phase 2 would have much the same result.  The Pourquoi Pas, a French research vessel that had participated in the first phase of the search, returned for a month in late July/early August 2009 in order to use dive equipment and towed sonar arrays to look for the debris field.  They were unsuccessful.  It was right around this time that the Waitt Institute was initially approached to assist the effort.

In the waning months of 2009 talks began between the French Government and the US on how the search could be successfully concluded.  Many eyes turned to Woods Hole Oceanographic Institute out on Cape Cod, Massachusetts.  The people at WHOI have been plying the depths of the oceans for over 75 years and are world leaders in the field.  They had pioneered a new technology for underwater searches working with the US Navy and that technology was just coming of age.  Autonomous Underwater Vehicles, or AUV’s, vastly increase capabilities over towed array side scan sonars, traditionally used in the past to search the ocean floor.  AUVs, as the name suggests, are free swimming devices that can perform the same type of search but are not limited, when working in waters up to 6,000 meters deep, by a four and a half mile tether running up to a surface vessel.  They swim solo, know where they are spatially at all times (a most critical capacity for re-navigation to suspected targets) and are exponentially more efficient.  By removing the hours taken up making the wide sweeping turns required when using a towed system AUVs increase the coverage against time efficiency by a factor of 4.  Even that increased efficiency is overshadowed by what the AUVs can do once a target is presented in the sonar data.  Within twenty four hours of detecting a potential site the AUV can be back over the exact same piece of real estate with pinpoint, unerring accuracy, and mere hours later it will carry to the surface photographs of every inch of bottom in the area designated.  Visual proof positive; a ground truthed target within 24 hours of initial detection with no changeover in equipment, indeed no postponement of survey operations.  That capability is a serious game changer when it comes to deep ocean search.

In early 2010 the BEA in France determined that a group of scientists would perform an analysis to define the search area and the equipment for Phase 3 would be the Waitt Institute AUV’s.  A team of twelve people from WHOI led by Mike Purcell and Greg Packard would be the equipment operators and Andy Sherrell who has worked as sonar analyst for the system since its inception in 2008 would continue in that role.

Phase 3 would be a large comprehensive effort.  The ship Seabed Worker would carry the Waitt Institute equipment along with one more vehicle from Geomar, an ocean research Institution in Germany and the only other civilian owner of a REMUS 6000.  The expedition would be carrying 3 full ocean depth AUV’s and for the first time ever the team would conduct triple vehicle, concurrent operations.  Running all that equipment around the clock would be a huge challenge but they would be able to cover ground in a way that has never before been seen.  While the AUV’s and the team would work on the Seabed Worker a group from Phoenix International, an ocean services company with whom the Waitt Institute and WHOI had previously worked with above Titanic in 2010, would also attend on the ship Anne Candies.  They would work with their slower towed arrays but in the case either team spotted the debris field Phoenix would deploy a work class Remote Operated Vehicle (ROV) for the recovery effort to retrieve the black boxes.

The teams worked two separate 30 day trips, covered close to 4000 square miles over some of the most demanding terrain on earth, often forced to survey areas twice in order that nothing be missed. They found nothing.  It was a bitter disappointment to all involved: planners, those who searched and the families of the lost, who had now been waiting a year for answers.

Almost immediately talks began anew for another, most likely final attempt to discover the resting place of the ill fated flight.  It was again determined that the Ocean Systems Lab from Woods Hole would take the lead.  Again they would use the Waitt Institute AUV’s and again they would bring in the third vehicle from Geomar, however this time only one ship would search.  In the past there had always been an ROV on site that could be deployed immediately if the debris field was found.  This can be a premature and extremely costly way to do business as the previous three expeditions had shown.  This time the team was leaned down to a single ship that carried the Waitt Institute Launch and Recovery Systems, AUV’s, Analysis System and vans which would be loaded aboard the ship Alucia in Seattle before transiting through the Panama Canal and into the Atlantic.  The Geomar vehicle would be added to the ship in Brazil and the only people on board would be the Waitt Institute/WHOI operations teams and analysts along with French investigators from the BEA (The French national equivalent to the NTSB).  Finally the search grid would be left to our analyst and colleagues from WHOI, the actual operators who had worked the previous 2, month long searches.  They were determined to miss nothing and very few predictions or guesses were added to the plan for the search.  They would go to the point that all the evidence indicated was the last known position of the plane, put the gear into the water on that spot and search in a spiral outward from there.

They were almost immediately successful, discovering the debris fields with the sidescan sonars on day 5 and by the end of the following day had conclusive photographic evidence that they had indeed found the wreckage of Air France’s flight 447.  It was welcome and surprising news.  After two years the world’s most advanced equipment and talented people in the field of underwater search had succeeded in under a week.

In the weeks that followed the AUV’s were used to make a detailed sonar mosaic map of the entire site and then the cameras were used to do the same, a literal photograph of the entire debris field was developed.  The group from Phoenix was called back in and as they headed to the site to deploy one of their REMORA ROV’s, the group who made the discovery flew to France to brief the government and to make plans on where the black boxes were most likely to be found. Mike Purcell, Greg Packard and Mark Dennett, the primaries from the Woods Hole team, returned home in subdued triumph after the meeting.  They had quietly done in days what others had been unable to do in two years; they had brought closure to the families by determining the correct place to look and then discovering the debris field.  The mystery would be solved

Andy Sherrell continued on to work the final phases of what was now a recovery, no longer a search.  He joined the effort carrying all of the data and a couple of the Institute computers (which also carry the expensive and arcane software needed to truly parse all of the data the AUVs can collect).  We had hoped to leave our navigational transponder field in place so that the ROV team that followed could plug directly in and use the same navigational support that had been used to map the site but we had discovered during our work with Phoenix on Titanic the year before that our systems are not compatible.  The Plan B: to send Andy, the same mind and equipment that collated the data originally would also be onsite to interpret it.  On the first day, via dead reckoning navigation achieved primarily through the use of photo maps collected by the Waitt Institute AUV’s, the ROV operators were able to find part of one of the black boxes.  Within 3 days the rest of it was found and recovered and by the end of the week the second black box was recovered in its entirety.  Both devices held readable data and as of this writing the problems that brought the plane down have been definitively identified.

People in the community will tell you, if you look for something long enough, spend enough money and keep at it, sooner or later you can find anything, and this is likely pretty much true, but finding even a large aircraft on the bottom of the ocean can be a truly daunting task.  If that airplane is scattered across a mountain range that happens to reside a mile and a half under the surface of the ocean and you have a truly epic task made drastically more difficult.  It took 6 months for the world to find Steve Fosset when the famous billionaire aviator crashed his plane in the eastern Sierra Nevada, not exactly the most remote spot on the planet.  It is not unreasonable to say that finding this particular aircraft was one of the most difficult underwater searches ever attempted, and doing so in just two years was quite an accomplishment.

Read More:
- Popular Mechanics
- USA Today