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WASHINGTON (AP) -- U.S. investigators say an exploding fuel tank apparently caused the blast aboard a Thai Airways Boeing 737, the same problem suspected in the fatal accident involving TWA Flight 800.

A report released Wednesday by the National Transportation and Safety Board said the plane's center tank exploded first, followed by the right tank 18 minutes later. The center tank is located near air conditioning packs, which had been running nonstop and generate heat when operating.

The report did not draw a conclusion about what caused the fuel tank to explode.

-- Rachel Gibson (rgibson@hotmail.com), April 12, 2001

Answers

I don't think the 737 has a center tank. I thought the tanks were in the wings. Can someone help on this.

-- David Williams (DAVIDWILL@prodigy.net), April 12, 2001.

Thai prime minister says 737 blast not from bomb April 12, 2001, 08:15 AM BANGKOK, Thailand – Prime Minister Thaksin Shinawatra said Thursday that a U.S. government probe into a blast that destroyed a Boeing 737- 400 last month shows it was caused by an exploding fuel tank, not a bomb.

RESOURCES • Boeing 737 • Federal Aviation Administration Meanwhile, Boeing on Wednesday night told all 737 operators that they should not use fuel boost pumps in the center fuel tank when the tank is empty, the Seattle Post-Intelligencer reported. Boost pumps transfer fuel from one tank to another.

The U.S. Federal Aviation Administration is expected to issue an airworthiness directive soon making the recommendation mandatory, the newspaper said, citing an unnamed industry source.

Thailand, which initially thought the explosion was caused by a plastic explosive, accepted the findings on the explosion but planned to continue its own investigation until the U.S. report was completed and made official, Thaksin said. That was expected to take about a year, he said.

The Thai Airways Boeing 737-400 exploded March 3 as it sat by a gate at the domestic terminal of Bangkok international airport, half an hour before Thaksin, his son and 147 other passengers were due to board a flight to the northern city of Chiang Mai. A flight steward was killed and seven airline staff were injured.

Explosives were initially believed to be present, but none were found when traces of chemicals had been sent to the FBI to be tested on equipment more sensitive than that available in Thailand, said a statement issued by the U.S. National Transportation Safety Board, which investigates transportation accidents.

Thaksin said it was a lab error that led Thai investigators to believe they had found traces of RDX. RDX, also known as cyclonite, is a chemical component of a plastic explosive.

"Even though we said earlier that the explosion was sabotage that was not final. We have to accept the result of the scientific tests," Thaksin said.

The NTSB statement said physical evidence was found that the center and right fuel tanks had exploded. The center tank exploded first, followed by the right tank 18 minutes later. The center tank is located near air conditioning packs, which had been running nonstop and generate heat when operating, it said.

Last year, Boeing told carriers flying its jets that they should not turn on air conditioning units of planes that are on the ground if outside temperatures are above 60 degrees. The FAA followed with a similar recommendation.

Air conditioning units are below the center wing tank on all Boeing jets except the 717, formerly the McDonnell Douglas MD-95.

The NTSB last year criticized the placement of the units and lack of a cooling unit for them.

The Thailand explosion marked the third such blast since 1990 that occurred in the center fuel tank of a Boeing plane on which air conditioning units had been running while the plane sat on the ground on a warm day.

The first was a Phillipine Airlines jet in 1990 at the Manila Airport. The explosion killed eight people.

The second involved TWA Flight 800, on which the center tank exploded about 13 minutes after takeoff from New York's Kennedy airport on the July 17, 1996 flight to Paris. All 230 people aboard were killed.

The NTSB found that fuel vapors in the tank had been heated to dangerous levels after air conditioning units on the 747 ran for more than two hours while the jet was parked at Kennedy.

The safety board recommended last year that inert nitrogen gas be pumped into jetliner fuel tanks to reduce the danger of an explosion.

The FAA is studying a system that would pump nitrogen into the center tank before takeoff. The agency is awaiting a final report by an aviation rule-making advisory committee, expected by July.

©2000-01 Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

http://www.king5.com/localnews/storydetail.html?StoryID=17453

-- Martin Thompson (mthom1927@aol.com), April 12, 2001.