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FAA to Order Review of Braking System : Air safety: Thrust reversers must be altered in Boeing 757s. The action, which stems from new evidence on crash, may affect hundreds of jets.

September 08, 1991|DON PHILLIPS | WASHINGTON POST

WASHINGTON — The Federal Aviation Administration will order a safety investigation involving hundreds of new-generation jetliners based on new evidence it has uncovered in the crash of a Boeing 767 in May.

Boeing and transportation officials, in an investigation of the 767 crash, found that if a special auxiliary braking mechanism on the engine, called a thrust reverser, deploys while the jet is in flight, the plane becomes almost impossible to control, officials said Saturday.

The FAA has ordered changes on some 767s in the wake of the crash, and this week will order changes in the braking system of the 767's smaller sister, the 757.

But preliminary simulations show that all larger modern twin-engine jets with the engines mounted on the wing might have the same control problem, and more detailed tests will be performed on those jets. In addition to the Boeing 757s and 767s, many Airbus Industrie planes--the A300, A310, A320 and A330--and the McDonnell Douglas MD-11 also are involved, officials said.

Anthony J. Broderick, associate FAA administrator for regulation and certification, said the FAA has no reason to believe that it is unsafe to fly these planes, but it is acting out of an "abundance of caution" after its investigation of the May 26 crash of a Lauda Air 767 in Thailand that killed all 223 people aboard.

Although the FAA orders so far deal only with short-term fixes to Boeing aircraft, Broderick said, engine thrust reversers on all large twin-engine jets must be certified as 100% fail-safe if those planes are determined to have the same aerodynamic qualities as the 767.

A thrust reverser redirects a portion of a jet engine's exhaust, providing extra braking power on landing. A number of safety systems are designed to ensure that the mechanism cannot be deployed in flight.

Boeing is working on a system to replace the one used on the 54 767s with Pratt & Whitney PW4000 engines, the type used on the Lauda plane that crashed. The FAA, based on a Boeing recommendation, earlier ordered thrust reversers deactivated on those planes, which can be safely landed with conventional wheel brakes alone.

Also involved in this week's FAA order will be 179 757s with the same engine, and those reversers must also be deactivated if the work is not completed quickly, Broderick said.

There has been no final determination of the cause of the Lauda crash, but investigators found evidence that the left engine thrust reverser deployed in flight as the 767 climbed at high power at about 26,000 feet.

Boeing and some crash investigators said initially that even if the reverser had deployed, the pilot should have been able to control the plane. Dozens of similar deployment incidents involving older planes with different engine arrangements, such as the Boeing 727 and the four-engine 747, had been easily controlled.

The airline's owner, race car driver Niki Lauda, said a week after the crash that the thrust reverser could not be the cause because he duplicated the Thailand incident in a 767 training simulator and easily controlled the plane.

However, it appears that aircraft simulators were inadequately programmed to reflect effects of a thrust reverser deployment on large jets with two wing-mounted engines, such as the 767.

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