WASHINGTON - The National Transportation Safety Board delayed a series of proposed safety measures for the Boeing 737 for 19 months because Boeing contended the measures were unjustified.
If implemented, the safety steps designed to address rudder-control problems suspected in at least two 737 crashes, including a USAir crash in Pittsburgh in 1994 that killed 132 passengers and crew, would cost Boeing hundreds of millions of dollars.
The recommendations might also imply that mechanical failure of the airplane was at least partly responsible for the crashes, creating potential legal liability for financial claims from families of crash victims.
So far, the NTSB has not reached a conclusion on the cause of the Pittsburgh crash. It concluded its investigation of a 1991 crash in Colorado Springs, in which a 737 mysteriously dived out of the sky while landing, killing all 25 aboard, without being able to find the cause.
The safety-board's proposals were unveiled publicly yesterday. A final NTSB vote on the measures will be held in two weeks. They then go to the Federal Aviation Administration, which would have to act before the recommendations became binding.
Sources said the recommendations were first drafted in March 1995, but their release was delayed 19 months because of Boeing's opposition.
Historically, the NTSB has relied heavily on the airplane manufacturers for technical expertise in determining the causes of
crashes. As a result, the manufacturers have gained considerable clout in safety-board deliberations.
Boeing is continuing to oppose many of the measures the safety board is considering to prevent inadvertent rudder movements from throwing a 737 out of control.
Boeing spokesman Russ Young contended no safety concerns have emerged in the lengthy investigations into the two as-yet unsolved 737 crashes or in a special seven-month review of the 737's rudder completed by the FAA last year.
"We've seen nothing in the accident investigations, in the design review conducted by the FAA, or in the service history of the aircraft that would require anything this far-reaching," Young said.
Meanwhile, Boeing officials are expected to take directly to NTSB Chairman John Hall and other board members the protests they have been making to board investigators ever since the Pittsburgh crash, said sources close to the board.
Boeing chief 737 engineer Jean McGrew said the company will await the final recommendations on proposed rudder-system upgrades. "We're not quite clear what the recommendations are going to look like, once the board is finished with them," McGrew said.
The safety board yesterday discussed calling for:
-- Extensively redesigning rudder-system components to make them less prone to sudden, hard twists of the rudder, the vertical tail piece that controls the jet's left-to-right heading. Upgrades would be retrofitted on the entire fleet of 2,800 jets.
-- Limiting the useful life of a crucial hydraulic part called the rudder power control unit (PCU). Dirty hydraulic fluid can jam the unit, resulting in hard rudder twists. The PCU was originally limited to 12,000 flights, but FAA rules were changed to allow "on condition" replacement, meaning airlines can use the unit indefinitely.
-- Establishing new procedures and installing new cockpit instruments to alert pilots to sudden rudder swings.
-- Training pilots how to right a plane suddenly thrown out of control by a hard rudder swing, especially at low altitudes when they may have only a few seconds to make precisely the right maneuvers.
-- Tightening FAA criteria for certifying 737 rudders as safe.
The primary author of the NTSB's recommendations is Greg Phillips, the safety board's top rudder expert. Phillips has spent thousands of hours examining, testing and retesting rudder parts from the 1991 crash of a United Airlines 737 in Colorado Springs and a similar crash of a USAir 737 in Pittsburgh on Sept. 8, 1994.
Sources who work with Phillips, speaking on the condition of anonymity, said he began circulating and promoting much the same set of recommendations six months after the Pittsburgh crash, in March 1995.
A couple of months later, in May 1995, the FAA completed its special review of the 737's control system, underscoring many of the concerns about the rudder raised by Phillips.
Yesterday, Phillips said "ample time" had passed since the completion of the FAA study. "We need to spur those on and get these actions accomplished," Phillips told board member John Goglia.
Recent developments have added urgency to the proposed upgrades.
Pilots are continuing to report 737 flights disrupted by unexpected rudder movements. McGrew said Boeing has received reports of more than 20 such cases so far in 1996, continuing a trend of some 50 such cases reported between the Pittsburgh crash and the end of 1995.
Boeing contends most of these reports involve glitches in an automatic rudder-control device, called the yaw damper, which can move the rudder only a few degrees.
But records show some jets have recurring problems that routine yaw-damper fixes don't eliminate. That was the case with the jet that crashed in Colorado Springs.
Then, last spring, an Eastwind Airline 737 had at least two mildly disrupted flights in the weeks prior to nearly crashing on June 9 near Richmond, Va. The pilot, Brian Bishop, saved the plane by instinctively using the kind of recovery maneuvers safety officials want to see mandated as training for 737 pilots.
Also pushing the need for rudder upgrades are the results of a recent testing of the PCU removed from the USAir jet that crashed in Pittsburgh. The tests were conducted in an independent lab by a panel of independent experts requested by the safety board's Hall. The results revealed the USAir jet's PCU could jam and cause a hard rudder swing to one side operating with dirty fluid under certain temperature conditions.
Boeing has challenged the expert panel's findings and will be allowed to retest the USAir jet's PCU, with Phillips watching, at its laboratory in Renton next week.
"If we get different results, then we will have to understand why the results are different," said Boeing's McGrew, adding that additional testing could follow.