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FAA orders emergency inspection of 737 rudders

737 assembly line

November 1, 1996
Web posted at: 11:35 p.m. EST

WASHINGTON (CNN) -- Boeing Co. recommended Friday that all 737 jetliners, the world's most widely used passenger plane, be tested within 10 days for potential safety problems in the rudder systems.

The 737's rudder has been a focus of investigations into the still unexplained crashes of the Boeing aircraft in Colorado Springs in 1991 and in Pittsburgh in 1994.

Boeing said in a statement that its engineers, in conjunction with the National Transportation Safety Board, discovered the plane's rudder power control, which is similar to a power steering unit in an automobile, could jam when subjected to unusually extreme temperatures.

Boeing has forwarded its recommendations to the Federal Aviation Administration (FAA), which said late Friday that it will issue an emergency order requiring inspection of the 737 rudders.

workers in at a Colorado crash site

Boeing said that if the rudder power control unit had a jamming problem, known as a "hard over," the airplane could roll to one direction and possibly go out of control if the pilot reacted incorrectly or if the plane was too close to the ground.

Experts have been able to reproduce such an event in laboratory tests. But, they stressed, no such problems have been reported in actual conditions involving more than 69 million flights.

Boeing said the occurance of a "hard over," is "very unlikely."

crash site in Pittsburgh

It said investigations into the Colorado Springs and Pittsburgh crashes did not reveal any such jamming problem with either rudder power control unit.

But, the NTSB said it was still studying the data and its relevance to the crashes.

"While the NTSB supports Boeing's efforts, we are doing a full analysis of this data to find out how it relates to the Pittsburgh and Colorado Springs accidents," NTSB chairman Jim Hall said in a statement.

NTSB recommendations

Earlier this month, the NTSB recommended a major overhaul of the tail rudder system in the 737. The recommendations required retrofitting existing planes and redesigning new ones to prevent possible loss of control from rudder failures. There are about 2,800 Boeing 737s in service.

tail section of 737

The list of safety proposals would require Boeing to develop and install cockpit indicators that would provide details on rudder position and movements.

The NTSB also has recommended that Boeing 737 flight crews be better trained to deal with uncontrolled rolls, a practice some airlines have adopted.

If the full range of revisions is required, they could cost the airline industry tens of millions of dollars.

Boeing spokesman Tim Neale has said the rudder system already has been redesigned for newer-model 737s now in production. The design change was needed because the aircraft is bigger than older models, not because of safety concerns, he said.

Correspondent Carl Rochelle and Reuters contributed to this report.

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