Washington:
Even if searchers are fortunate enough to spot floating debris in the ocean west of Australia from the missing Malaysia Airlines jet, it would be only a modest step in locating the rest of the Boeing 777, according to oceanographers and recovery experts. And only then could they dig into the question of why it crashed.
Almost two weeks after a crash, there is certain to be less of the debris on the surface, and what remains is more dispersed and farther from the clues that investigators really want, in the wreckage that has sunk beneath the waves, experts say.
The delay in finding any wreckage on the surface will "create a cone of uncertainty, which is going to be bigger with time," said Luca Centurioni, a researcher at the Scripps Institution of Oceanography in San Diego and the director of the Global Drifter Program there. "The more time goes by, the more difficult it will be to try to go back to the point of impact with the ocean."
The amount of debris and degree of dispersion would depend in part on the circumstances of a crash.
"A gentle landing on a smooth sea with mild currents keeps the debris field more intact," David G. Gallo, director of special projects at the Woods Hole Oceanographic Institution, said in an email. "A high-velocity impact or midair breakup on a stormy sea will scatter objects much more."
In the case of Air France Flight 447 - which came down in the equatorial Atlantic in June 2009 while traveling from Rio de Janeiro to Paris - searchers found debris after five days, and experts estimated that the impact site was 15 miles away. It turned out to be 30 miles away, and in a different direction, said Michael J. Purcell, the principal engineer at Woods Hole, who spent months on that search. If the Air France case is any guide, Malaysia Airlines debris could have drifted hundreds of miles.
Median ocean current speed is about a foot per second, said Centurioni, which comes to about 16 miles a day. The tropics are a bit slower; the Air France wreckage was moving at about 10 miles per day, Purcell said. Average speed at the site of any Malaysia Airlines crash would depend on where that airliner went down.
Some debris would be pushed more by wind than current, and the wind could be moving in the same direction as the current, or against it.
Some parts of airplanes, like seat back cushions, are designed to float. Aluminum parts with air trapped inside will tend to sink in rough seas. Planes like the Boeing 777, the type in the Malaysia flight, or the Airbus A330, in the case of the Air France crash, make major use of composite materials, and some of those are in the form of a honeycomb using light materials with air trapped inside. Those parts will float for some time, as the tail of Air France Flight 447 did, and the tail of the American Airlines A300 jet that crashed shortly after takeoff from Kennedy International Airport in November 2001.
The searchers, flying in various aircraft but notably in airplanes designed to hunt enemy submarines, are using infrared scanners, which detect minute temperature differences between the water and debris, as well as radar. They make low passes at hundreds of miles per hour.
If the airplane searches locate floating debris, and oceanographers calculate where it originated, the next step would be to use robot submarines to scrutinize the ocean floor. Purcell said the Woods Hole drone submarines, like the Remus 6000, traveled about 4 mph, covering a little less than a mile in width if the sea floor is smooth. They were not built with this purpose in mind. (In fact, this week the Remus 6000 was gathering clam larvae, Purcell said.)
In search work, the submarines follow a pattern like a lawn mower, laboriously tracing back and forth. The search area is now more than 2 million square nautical miles but would have to be narrowed to about 5,000 square miles before it would be sensible to use the submarines, he said.
The cockpit voice recorder, important in any investigation and crucial when a hijacking or other crime is suspected, would probably not be useful, one investigator said, because it is a two-hour loop, and the plane flew for hours after leaving its planned route. The boxes originally captured 30 minutes, on a loop of audiotape, but in 1999 the Federal Aviation Administration endorsed the idea of going to two hours. The recording is now on microchips.
Almost two weeks after a crash, there is certain to be less of the debris on the surface, and what remains is more dispersed and farther from the clues that investigators really want, in the wreckage that has sunk beneath the waves, experts say.
The delay in finding any wreckage on the surface will "create a cone of uncertainty, which is going to be bigger with time," said Luca Centurioni, a researcher at the Scripps Institution of Oceanography in San Diego and the director of the Global Drifter Program there. "The more time goes by, the more difficult it will be to try to go back to the point of impact with the ocean."
The amount of debris and degree of dispersion would depend in part on the circumstances of a crash.
"A gentle landing on a smooth sea with mild currents keeps the debris field more intact," David G. Gallo, director of special projects at the Woods Hole Oceanographic Institution, said in an email. "A high-velocity impact or midair breakup on a stormy sea will scatter objects much more."
In the case of Air France Flight 447 - which came down in the equatorial Atlantic in June 2009 while traveling from Rio de Janeiro to Paris - searchers found debris after five days, and experts estimated that the impact site was 15 miles away. It turned out to be 30 miles away, and in a different direction, said Michael J. Purcell, the principal engineer at Woods Hole, who spent months on that search. If the Air France case is any guide, Malaysia Airlines debris could have drifted hundreds of miles.
Median ocean current speed is about a foot per second, said Centurioni, which comes to about 16 miles a day. The tropics are a bit slower; the Air France wreckage was moving at about 10 miles per day, Purcell said. Average speed at the site of any Malaysia Airlines crash would depend on where that airliner went down.
Some debris would be pushed more by wind than current, and the wind could be moving in the same direction as the current, or against it.
Some parts of airplanes, like seat back cushions, are designed to float. Aluminum parts with air trapped inside will tend to sink in rough seas. Planes like the Boeing 777, the type in the Malaysia flight, or the Airbus A330, in the case of the Air France crash, make major use of composite materials, and some of those are in the form of a honeycomb using light materials with air trapped inside. Those parts will float for some time, as the tail of Air France Flight 447 did, and the tail of the American Airlines A300 jet that crashed shortly after takeoff from Kennedy International Airport in November 2001.
The searchers, flying in various aircraft but notably in airplanes designed to hunt enemy submarines, are using infrared scanners, which detect minute temperature differences between the water and debris, as well as radar. They make low passes at hundreds of miles per hour.
If the airplane searches locate floating debris, and oceanographers calculate where it originated, the next step would be to use robot submarines to scrutinize the ocean floor. Purcell said the Woods Hole drone submarines, like the Remus 6000, traveled about 4 mph, covering a little less than a mile in width if the sea floor is smooth. They were not built with this purpose in mind. (In fact, this week the Remus 6000 was gathering clam larvae, Purcell said.)
In search work, the submarines follow a pattern like a lawn mower, laboriously tracing back and forth. The search area is now more than 2 million square nautical miles but would have to be narrowed to about 5,000 square miles before it would be sensible to use the submarines, he said.
The cockpit voice recorder, important in any investigation and crucial when a hijacking or other crime is suspected, would probably not be useful, one investigator said, because it is a two-hour loop, and the plane flew for hours after leaving its planned route. The boxes originally captured 30 minutes, on a loop of audiotape, but in 1999 the Federal Aviation Administration endorsed the idea of going to two hours. The recording is now on microchips.
© 2014, The New York Times News Service
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