When planes crash in water, recovery gets complicated
Depth of water could hamper efforts to salvage small but important
When the Coast Guard put out the call that a plane went down off the California coast about 40 miles northwest of Los Angeles, help came in the form of sport-fishing boats, pleasure craft, and commercial squid fishers.
From dusk until dawn, they cruised the choppy waters, collecting debris and hoping to find survivors from Alaska Airlines Flight 261, which plunged into the ocean on Jan. 31.
Marshaling that outpouring of maritime help is probably the easiest logistical problem that aviation crash investigators will face as they attempt to understand why the MD-83 carrying 88 people on a flight from Puerta Vallarta, Mexico, to San Francisco suddenly nose-dived into water.
Investigations of ocean crashes take far more time, money, and effort than those of land crashes because of the difficult task of recovering wreckage immersed in hundreds of feet of water. As a result, it's much harder for investigators to piece together the often-tiny clues that help them understand exactly what went wrong.
"It's not unusual for relatively small pieces to hold the key in an accident investigation," says Clint Oster, an aviation expert at Indiana University in Bloomington.
While officials are not yet speculating on the cause of the crash, early indications point to a mechanical failure.
Moments before the plane disappeared from radar screens, the pilots radioed the control tower at Los Angeles International Airport to say they were having problems with the plane's horizontal stabilizers, which help control the plane.
But before investigators draw any conclusions, they want to hear the flight-data and cockpit-voice recorders, which are immersed in the waters of the Santa Barbara Channel, which runs as much as 700 feet deep.
Experts say that depth will undoubtedly complicate the recovery effort. After TWA Flight 800 went down off the coast of Long Island in July 1996, investigators spent more than nine months and more than $40 million dollars to recover 98 percent of the aircraft. That water was only 120 feet deep.
There, five scallop trawlers scooped up about one ton of pieces, some as small as a quarter, from the bottom - only 1 percent of the total wreckage. While a final cause has still not been definitively determined, investigators believe that corrosion of probes in the center fuel tank could have caused the explosion. The probes were tiny, the size of a finger.
When EgyptAir Flight 990 went down off the coast of Nantucket Island in Massachusetts last autumn, the wreckage was in 270 feet of water. Special salvage vessels and deep water robots had to be brought in to search the ocean floor.
The National Transportation Safety Board (NTSB) only recently suspended efforts to collect wreckage from the flight. It cost more than $4 million to recover about 70 percent of the plane. The cause of that accident has also not been determined.
Until recently, nearly all fatal air crashes in the US have been on land. Since a ValuJet crash over the Florida Everglades in 1996, however, the NTSB has confronted a spate of water crashes - TWA Flight 800, the John F. Kennedy Jr. accident, and EgyptAir 990.
Ordinarily, investigators spend a week or two on scene when commercial flights crash on land. By contrast, they spent six weeks in the Everglades - hiring sharpshooters to fend off alligators -and more than nine months pulling up pieces of wreckage from TWA Flight 800.
The NTSB is now on the scene in Oxnard, Calif., to try to locate and recover the black boxes from the Alaska Airlines crash. When it does - and if the data recorders confirm the mechanical problem with the stabilizer - that could be just the start of the inquiry.
"The flight-data recorder may indicate there was a mechanical problem, but it most likely will not tell you the source of the problem, why things didn't respond the way they were supposed to," says Professor Oster. "For that, you'd like to be in the position to examine key parts of the wreckage."
(c) Copyright 2000. The Christian Science Publishing Society