Maintenance key focus of Alaska Airlines hearings

WASHINGTON (Reuters) -- Alaska Airlines and Boeing Co. face tough questions at hearings this week on the maintenance and design of key tail components in the MD-80 airliner that crashed off California last January, killing all 88 people on board.

While no conclusions on the cause of the crash of Flight 261 will be drawn at the National Transportation Safety Board proceedings, investigators have focused for months on parts controlling the horizontal stabilizer mounted on top of the jet's tail.

The pilots waged a harrowing but ultimately futile effort to keep the plane aloft after radioing that they were having trouble controlling the stabilizer that maintains level flight and is also used for gradual climbing or descent.

"This hearing is a fact-gathering process," NTSB member John Hammerschmidt has said in a statement on the hearings he will chair, which begin Wednesday in Washington.

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Traveling from Puerto Vallarta, Mexico, to San Francisco on January 31, the pilots had requested an emergency landing in Los Angeles and were trying to stabilize the plane over the Pacific Ocean before attempting to land.

Alaska Airlines is the nation's 10th largest carrier and a subsidiary of Seattle-based Alaska Air Group.

Numerous questions have been raised during the investigation about the jackscrew assembly, the mechanism that moves the horizontal stabilizer.

The two-foot jackscrew is powered by electric motors and threaded vertically through another part, a stationary gimbal nut, to move the stabilizer up and down.

The jackscrew was retrieved from the seabed off Point Mugu, north of Los Angeles, with threads from the gimbal nut wrapped around it. Investigators, in safety board reports, have questioned whether the jackscrew had been lubricated properly.

Maintenance records also show the airline nearly replaced the jackscrew mechanism on the aircraft in 1997 because it failed a test for wear but decided not to after repeat testing showed wear was within the carrier's accepted tolerances.

Hammerschmidt said the hearings would address a number of things, including Alaska's maintenance practices and Federal Aviation Administration oversight. The FAA performed a special inspection of the airline following the crash which resulted in the agency proposing a fine of nearly $1 million.

The carrier's maintenance operations are also being investigated by a federal grand jury in California.

A spokesman for the carrier would not guess what direction the investigation might take during the hearings, saying he expected a fair review from the NTSB. "Certainly we can't speculate," said Greg Witter. "We have cooperated fully every step of the way."

Another matter to be reviewed, according to Hammerschmidt, will be the design of the horizontal stabilizer in MD-80 series aircraft. Among other things, investigators want to know if a piece attached to the end of the jackscrew called the end stop separated in flight, leading to the final loss of control, or broke off the jackscrew when the plane hit the water.

A published report recently said suspicion that the end stop broke in flight was gaining steam with at least one leading NTSB investigator. However, other reports and questions raised by safety board officials in their own documents suggest a combination of failures within the stabilizer mechanism may have led to catastrophe.

A Boeing spokesman said jackscrew end stops were not designed as a back-up in the event the threads were lost from the gimbal nut. Instead, spokesman John Thom told Reuters the mechanical stops were designed to back up electrical stops that prevent the motor turning the jackscrew from moving the stabilizer beyond safe limits.

Investigators know from the plane's flight data and cockpit voice recorder that Flight 261's stabilizer went into a full nose-down position about 12 minutes before the crash.

The crew regained control after a steep dive by using other stabilizer controls called elevator panels. But they lost control of the jet for good shortly after extending, for a second time, the wing slats and flaps they would need for landing.

A loud noise was heard on the cockpit voice recorder at the beginning of the final descent from 18,000 feet .

The NTSB hearing is scheduled for three days but a safety board spokesman said it could go longer. A final report on the crash is not expected for months.

Copyright 2000 Reuters. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.

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Alaska Airlines
The Boeing Company
National Transportation Safety Board
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