Journey to the Bottom of the Sea
14 May 2014
Posted by: Peter Rowntree
While this is an intriguing title for an article written by an air investigator, often there is more to an aircraft accident than meets the eye. When most people hear about an aircraft accident, they think of them as only happening on land. The search, recovery, and corresponding investigation for those accidents are often very complex. However, that complexity pales in comparison when the aircraft has crashed in water. It is that very complexity that makes searching for missing aircraft in water so interesting, frustrating and rewarding.
My first introduction to water-based search and recovery operations was the crash of Swiss Air 111 off the coast of Nova Scotia near Peggy’s Cove in 1998. From that investigation on, I’ve always been fascinated by the world of search and recovery operations in water.
Searching for a missing or downed aircraft in water can vary from relatively easy to insanely complicated. It is akin to looking for the proverbial needle in a hay stack. Quite often, we are lucky and the aircraft remains partially afloat and is easily spotted by air or surface vessels. Other times, it has gone down in a relatively known or confined area and is moderately difficult to locate. Finally, there are those times where you have a general idea of where the aircraft went down, but finding the aircraft can be extremely difficult. This can turn into your worst nightmare. But the harder the aircraft is to find, the greater the sense of accomplishment when it’s finally located.
There are so many variables to consider when we start looking for an aircraft under water. How deep is the water? What is the clarity of the water? How big is the search area? What time of year did the accident happen? What are the weather conditions like? What equipment and expertise are available and how much will all of it cost? One thing is for certain, the cost of search and recovery for a submerged aircraft is expensive; and those costs can increase exponentially with the size of the search area, the depth of the water, the duration of the search, and the size of the aircraft.
Once the aircraft is found, the recovery effort can be just as complex if not impossible. Before any decision to recover can be made, the aircraft must be thoroughly surveyed and documented. There is often much that investigators can learn by just looking at the wreckage under water before anything is disturbed. This phase of the investigation can again be quite lengthy, but can provide vital clues as to what happened before the aircraft is recovered.
One of the big problems we investigators face is that we are often only coordinators and observers during much of the recovery. Our only view of the aircraft is sitting in a cramped room on a vessel staring at small monitors displaying images from a diver or remotely operated vehicle’s (ROV) camera. This is complicated further by the fact that we can usually only see 10 feet or less if we are lucky, due to water conditions and limited light.
Decision to recover
Once a decision is made to recover the aircraft, the real work begins. Recovering a Cessna 172 from a lake can be difficult, but it’s not really all that hard. Recovering an MD-11 from a depth of 160 feet, a Sikorsky S-92 from a depth of 548 feet, or an Airbus A330 from a depth 13000 feet on the other hand, is extremely difficult and very expensive.
With Swiss Air 111, the recovery took 14 months and cost millions of dollars. The operation used divers, barges with cranes, a scallop dragger, ROVs and finally a suction dredge—but we recovered 98% of that aircraft and the TSB was able to make many recommendations to advance safety in air travel.
The recovery of the Cougar 491 helicopter was accomplished solely by the use of an ROV and properly-equipped ship. A difficult task, but with good planning, the right equipment, and experienced ROV operators, the search and recovery was accomplished within a week. This was also how a sunken Canadian Coast Guard helicopter was recovered in the Arctic Ocean, two weeks after it crashed and sank in September 2013.
In the end, any operation that takes place in water is going to involve a massive amount of logistics, sound planning and good resources. The operation may very well be expensive and time consuming. It may often feel like a lost cause, but the feeling of satisfaction when the aircraft is finally located and successfully recovered is one that cannot be described in words.
Peter Rowntree has 26 years of civil aviation experience. He joined the TSB in November 1997 as an investigator/technical specialist in the Air Investigations Ontario Regional Office, in Richmond Hill, Ontario. Peter enjoys computer flight simulation and has his own flight simulator at home. On his spare time, he helps design digital scenery for Microsoft flight simulators. He is also an avid recreational scuba diver.
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