BOEING TO MODIFY 737S TO PREVENT MALFUNCTIONS.

Byline: James V. Grimaldi and Byron Acohido The Seattle Times

Vice President Al Gore announced Wednesday a plan to make major modifications to the rudders of all Boeing 737 jetliners to prevent malfunctions that can cause the aircraft to twist into a sudden nose dive.

Gore outlined proposed Federal Aviation Administration directives requiring Boeing to make four major rudder improvements, including redesigning and replacing within two years a flawed valve at the heart of the 737's rudder-control system.

In Washington, D.C., Gore told a White House-sponsored aviation safety and security conference at George Washington University that the rudder changes emerged out of the investigations of two still-unsolved jetliner crashes: in Pittsburgh and Colorado Springs, Colo.

Although federal investigators have been unable to pinpoint a cause in either accident, Gore said the exhaustive investigations ``have identified improvements that could help eliminate the chance of rudders playing a role in future accidents.''

``These changes should be made without delay,'' Gore said. ``And with today's announcement, they will be.''

Gore credited a plan developed by Boeing for Wednesday's announcement.

``Boeing has developed modifications of the rudders of older 737s that will improve safety,'' Gore said. ``And they are going to begin retrofitting those planes, largely at their own expense.''

The FAA's proposed directives affect more than 2,700 planes worldwide, including about 1,100 registered in the United States.

Boeing spokesman Chet Ekstrand said Wednesday that Boeing would pay an estimated $50,000 per airplane for the upgrades, or about $135 million for the entire fleet. Airlines are expected to pay an additional $27 million in labor costs, he said.

The rudder is the movable panel on the vertical tail that controls the direction of travel. It can sometimes swing ``hardover'' to one side - uncommanded by the pilot.

Rudder hardovers are widely suspected of causing the 1991 crash of a United Airlines 737 in Colorado Springs, which killed 25 people, and the 1994 crash of a USAir 737 in Pittsburgh in which 132 died. Both accidents remain officially unsolved by the National Transportation Safety Board.