Thursday, 13 March 2014

Recovering plane wreckage from water an arduous task

When planes crash into water, it can take days to find the "black boxes" that record information about the flight — even when the plunge is witnessed, according to four plane crash investigations before the latest search for Malaysia Airlines Flight 370.

And once the wreckage is recovered, the investigation following can then take years.

In a more difficult case, it took two years to find the flight recorders after the 2009 crash of Air France Flight 447 in the Atlantic Ocean, and months more to recover parts of the plane. The difficulties came even though the plane went down within a few miles of its last signal.

"You start with the last place you know where the airplane was and widen out from there," said William Waldock, who formerly worked in Coast Guard search and rescue and now teaches safety science at Embry-Riddle Aeronautical University in Arizona. "It should have been right over the Gulf of Thailand where it started."

He was surprised that Vietnam's fairly sophisticated radar wasn't able to track the plane or its debris all the way to the water.

"For them not to be able to be able to track it to the surface, I just find that astounding," Waldock said.

Even when the crash is witnessed, such as the TWA explosion in 1996, the search can be difficult because debris can spread in the air on the way down or in the water's current.

"When it hits water, it's not like a brick wall, not a solid and it starts breaking up more," said Al Yurman, a former investigator with the National Transportation Safety Board. "It rips things apart."

He suggested the Gulf of Thailand, where the search has focused since the Malaysia flight disappeared early Saturday, is a large area to cover.

"It could take them any amount of time more before they find anything," Yurman said.

Following are the results of four plane crashes that illustrate the difficulties of a water recovery:

Trans World Airlines Flight 800, a Boeing 747-131, from New York's JFK airport to Paris broke up over the Atlantic Ocean near East Moriches, Long Island, on July 17, 1996, killing 230 people on board. The U.S. National Transportation Safety Board investigated.

The search: The plane broke up and fell into the ocean about 8:30 p.m., with witnesses on shore witnessing the flash. Pieces of wreckage were found along a path 4 miles long and 3.5 miles wide. Remote-operated vehicles and divers were used to recover victims and wreckage. The recovery took 10 months and retrieved more than 95% of the plane.

The black boxes were recovered July 24, 1996. Although the recorders were damaged in the crash, they yielded "data of good quality."

The investigation concluded Aug. 23, 2000. The NTSB ruled that the center fuel tank exploded, likely from a short-circuit in nearby wiring.

SilkAir Flight 185 from Jakarta, Indonesia, to Singapore crashed Dec. 19, 1997, in the Musi River in Indonesia, killing 104 people aboard. Indonesia's National Transportation Safety Committee investigated.

The search: The Boeing 737-300 crashed about 4 p.m. and wreckage penetrated deep into the river bed, although parts of the plane were found nearly 2½ miles away. About 73% of the plane was recovered, most from an area in the river 196 feet by roughly 262 feet. The river was about 26 feet deep at that location. Recovery was difficult for Indonesia and Singapore navy divers because of the river current and because much of the wreckage was buried. Only six human remains were recovered at the site. Recovery of the wreckage was completed Jan. 28, 1998.

The flight-data recorder was recovered by divers on Dec. 24 and the cockpit-voice recorder by river dredging on Jan. 8, 1998. But the black boxes had been turned off before the plane's descent from 35,000 feet.

The investigation was concluded Dec. 14, 2000. The NTSC found no mechanical failure to explain the crash and ruled that the plane was probably steered to the ground from the cockpit. A California jury hearing a case about the crash later ruled that the plane's rudder malfunctioned and forced the plane into the ground.

EgyptAir Flight 990 from New York's JFK airport to Cairo crashed Oct. 31, 1999, about 60 miles south of Nantucket, killing 217 people aboard. The U.S. National Transportation Safety Board investigated, at Egypt's request.

The search: The Boeing 767-366ER crashed about 1:50 a.m. and debris was found in two fields. The initial recovery effort lasted from Oct. 31 to Dec. 22, when about 70% of the plane was recovered. A second recovery to gather more material occurred March 29 to April 1, 2000.

The Navy found the flight-data recorder Nov. 9 and the cockpit-voice recorder Nov. 14. Both recorders were damaged in the crash and their tapes were wet when found, but the tapes were in otherwise good condition and investigators were able to retrieve information from them.

The investigation was concluded March 13, 2002. The NTSB found no problems with the plane and ruled that a relief pilot steered the plane into the ocean for unknown reasons.

Air France Flight 447 from Rio de Janeiro to Paris crashed in the Atlantic Ocean off the coast of Brazil on June 1, 2009, killing 228 people on board. . The Bureau d'Enquetes et d'Analyses investigated.

The search: French and Brazilian navies found floating debris from the Airbus A330-203 between June 6 and 26, but the search for the plane took years longer in four phases. The third unsuccessful phase spanned 2,400 square miles of ocean in April and May 2010. The wreckage was finally located about 12,800 feet deep on April 2, 2011, during the fourth phase from March 23 to April 12, 2011, about 6.5 nautical miles from its last known signal. Ultimately 104 bodies and parts of the plane were recovered by June 16, 2011.

The flight-data recorder was recovered May 1, 2011, and the cockpit-voice recorder the next day. Parts of the memory boards were damaged, which investigators tried to repair, but some data was missing.

The investigation concluded July 27, 2012. The BEA concluded that the plane's airspeed indicators froze during a storm and surprised pilots, who mistakenly pulled the aircraft into an aerodynamic stall and fell into the ocean.

Thursday 13 March 2014


Post a Comment