Airlines Told to Stop Using Boeing 767 Thrust Reversers : Safety: FAA says 168 of the craft have the device, which helps jets stop. The mechanism is linked to the 223-death crash of one of the planes in Thailand.

From Associated Press

The Federal Aviation Administration ordered U.S. airlines Friday to disconnect the engine-reversing mechanism that is linked to the fatal crash of a Boeing 767 last May.

The thrust reverser directs the powerful jet engine force forward, producing the sudden deceleration that passengers feel after the airplane touches down.

An FAA spokesman said that 168 of the 382 two-engine Boeing 767s in service around the world are equipped with the device.

Investigators determined that an engine reversed in flight on a Lauda Airlines plane shortly after it took off from Bangkok, Thailand, on May 26. The Austrian airliner crashed in the jungle, killing all 223 people on board.

The FAA said the investigation has not shown conclusively what caused the engine reversal or even whether it led to the crash, but it said that "possible discrepancies" were found in the valve that controls direction of the jet flow.

Both Boeing and the FAA said the 767 is designed to stop with its brakes alone and that safety will not be compromised by disabling the thrust reversers.

Boeing said it discovered the problem this week when testing a directional control valve on a 767 equipped with Pratt & Whitney PW4000 engines, the type used on the Lauda jet. The company said it is reviewing other such control systems to ensure that they do not have a similar potential for failure.

Tests showed that contamination in the valve can cause internal blockage that, together with an increase in hydraulic pressure, can cause the valve to activate the reversing mechanism in flight, the FAA said.

The order affects Boeing 767s operated by Delta, United, American and USAir. Overseas airlines using the planes are expected to go along as well.

American Airlines spokesman John Hotard said in Ft. Worth that the order affects 17 American 767s, which primarily are used on transatlantic flights. The airline is telling its crews not to use the reversers, and the actual disabling will begin Sunday.

In its directive, the FAA said all electrically controlled thrust reversers must be deactivated "until such time that final corrective actions have been identified." Airlines have seven days to comply.

The suspect electrical mechanism is unique to the Pratt & Whitney engines, the FAA said, but it also ordered deactivation of thrust reversers on 767 engines made by General Electric and Rolls Royce because their designs are similar.

The FAA said it will require that 767s without thrust reversers have an additional 5% of runway length for takeoff, to add an extra safety margin if the takeoff has to be aborted. No such added runway is needed for landing, the FAA said, because "operating rules presently require conservative factors."

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