Alaska Air Found Excess Wear in 3 Jets Before Crash

Alaska Airlines found excessive wear in the stabilizer control systems on three planes in the months before another Alaska jetliner crashed when its stabilizer failed off the coast of Ventura County, airline officials said Friday.

The unexpected wear prompted an alert that there were problems with the stabilizer systems on Alaska’s MD-80 series jets, but a computer failed to generate that alert until three days after the crash.

“Unfortunately, it did not react in time to tip us off,” Wright McCartney, Alaska’s manager of maintenance reliability, told a National Transportation Safety Board hearing.

NTSB investigators say the stabilizer jammed and then failed entirely as the twin-engine MD-83 headed northwest on a Jan. 31 flight from Puerto Vallarta, Mexico, to San Francisco and Seattle.

The failure of the stabilizer, which is the flat, winglike portion of the plane’s tail that largely controls the up-and-down pitch of the nose, threw Flight 261 into a dive. Seconds later, it slammed into the Pacific near Anacapa Island, killing all 88 people on board.

McCartney said routine inspections of one MD-80 series jet in June 1999, and two others in November 1999, turned up wear on the stabilizer jackscrew mechanism threads that exceeded the allowable maximum. The jackscrew is a heavy, threaded bolt that moves up and down through a gimbal nut, raising and lowering the leading edge of the stabilizer.

All three worn mechanisms were replaced, and data on them were entered into a computer system the company uses to monitor maintenance and systems reliability. But even though the work on the last plane was completed in November, the data on it weren’t entered until weeks later, McCartney told the hearing.

McCartney said it was the third set of data that set off the Feb. 3 alert. Such alerts, he said, normally trigger special inspections to help head off further problems.

Thread wear was found on these jackscrew mechanisms. On the one from Flight 261, there was no grease found on many jackscrew threads, and the threads from the gimbal nut had been stripped clean.

Testimony this week has focused on two issues: whether the jackscrew mechanism was designed properly and whether it had been maintained properly.

Officials from the Federal Aviation Administration, which certified the design, said it provides strength that far exceeds any anticipated loads on the mechanism.

They said the jackscrew and gimbal nut also have a necessary form of redundancy: a double helix of spiraling threads like red and white stripes on a barber pole. Each set, they said, is capable of carrying the full stabilizer load.

Nonetheless, the jackscrew mechanism on Flight 261 failed.

Michael O’Neil, an FAA engineer, said FAA certification of a design assumes that the system will be maintained adequately. Such maintenance, he said, would include adequate lubrication with the proper grease.

In the years before the crash, Alaska officials had received permission to extend the intervals between greasings from Boeing Co., which has taken over the operations of McDonnell-Douglas, which designed and built the plane. The FAA signed off on this “escalation” of the intervals between greasings, according to Lee R. Koegel, an FAA safety inspector.

“We don’t approve such escalations; we find them acceptable,” Koegel said, explaining that the agency simply acknowledges that it is aware of them.

“So if you ‘accept’ it, that gets you more off the hook than if you ‘approve’ it,” John Clark, the NTSB’s acting director of aviation safety, observed dryly.

Alaska also received permission, starting in 1997, to substitute a new lubricant for the one it had been using. Alaska said it sought the change thinking the new grease would provide better rust protection and would perform better in the arctic temperatures at which the airline often operates.

However, NTSB investigators are looking into whether the two greases are incompatible, and whether residue from the old grease may have caused the new grease to break down. They say small amounts of the old grease were found in grease recovered from the ends of Flight 261’s jackscrew.

Investigators also say that at least one grease fitting on the Flight 261 jackscrew mechanism was plugged, but they say it is not known whether this accounted for the absence of grease on many of the threads.

Among those testifying Friday were Robert Falla and Robert Hinman.

Sixty-four Alaska mechanics wrote a letter to the carrier’s management in March, accusing Falla, then Alaska’s manager of base maintenance in Seattle, of jeopardizing safety by pressuring them to put unserviceable parts back on airplanes. Falla was fired.

Hinman, Alaska’s former director of maintenance at Alaska’s repair facility on Oakland, refused to testify until the Justice Department granted him immunity from prosecution, according to the NTSB. That immunity was granted.

Since 1998, a federal grand jury in San Francisco has been investigating alleged falsification of maintenance records at the Oakland facility.