FAA Orders Replacement of Faulty Rudders on Boeing 737s

Rudder systems on Boeing 737s, the world’s most widely used airliners, must be replaced by U.S. carriers under a $364-million retrofitting program ordered Monday by the Federal Aviation Administration.

The order came years after two disastrous 737 crashes that were blamed on rudder failure. The first, near Colorado Springs, Colo., in 1991, killed all 25 aboard a United Airlines flight. The second, near Pittsburgh three years later, killed 132 on a USAir jetliner. USAir since has been renamed US Airways.

U.S. carriers will have six years to comply with Monday’s order, which affects all 2,000 of the twin-engine jets being flown in this country.

Foreign carriers, which fly an additional 2,500 Boeing 737s, are expected to follow suit voluntarily.

Boeing said Monday that it will pay for the retrofits, which will be accomplished during regularly scheduled maintenance. It added that 737s now on order will be delivered with the new rudder systems.

The National Transportation Safety Board concluded last year that both the 1991 and 1994 crashes occurred after the pilots pushed control pedals to move the rudder in one direction, but the device moved in the opposite direction.

The rudder is the large, hinged slab on the vertical part of the tail that works like the rudder on a boat--helping a plane fly straight, turn right or turn left.

Jetliner pilots use the rudder primarily to compensate for crosswinds when taking off and landing.

Full deflection of a rudder can cause a plane to roll and then plunge; that’s apparently what happened in the Colorado Springs and Pittsburgh crashes. The NTSB said radar data and on-board recording devices recovered from the wreckage showed that in both cases, the jetliners banked steeply to one side before plunging nose-first into the ground.

Boeing reported in 1995 that, in addition to the two crashes, its 737s had experienced rudder-related “lateral or directional problems” 187 times in the previous 15 years. None of those 187 incidents caused a crash, but they did prompt the flight crews to make precautionary landings or file incident reports with Boeing.

Monday’s order was the latest--and presumably the last--in a series of FAA directives issued since the crashes. One earlier directive mandated a simplified procedure for pilots to use if the rudder jams. Another called for mechanical modifications designed to reduce the likelihood of malfunctions. A third called for improved maintenance procedures.

But in the end, a group of experts appointed by the FAA concluded that these earlier fixes were inadequate and that a new system was required. The FAA proposed the retrofit in November and, after months of input from the industry and the public, issued the replacement order.

The new system, designed by Boeing, is fully redundant, with two independent control mechanisms, both of which can be overridden by the pilots.

“This new design will increase the overall safety of the 737 by simplifying the rudder system and eliminating a range of failure possibilities,” the FAA said.