Stabilizer Problems Found in 9 Jetliners

Inspections have turned up problems with the horizontal stabilizer mechanisms of at least nine planes like the Alaska Airlines jetliner that crashed last week off Anacapa Island, sources close to the crash investigation said Friday.

The problems on five of those planes--three of them flown by Alaska Airlines--appear eerily similar to those found on the stabilizer wreckage recovered after the Jan. 31 crash.

The problems on two of the planes were discovered Thursday, during a voluntary inspection by Alaska. The rest were found Friday during a mandatory inspection prompted by Thursday’s discoveries, the sources said.

The aircraft inspected and grounded Friday included two planes each from Alaska and Delta Air Lines and one each from American Airlines, Continental Airlines and Northwest Airlines.

The Federal Aviation Administration’s mandatory airworthiness directive handed down Thursday called for the inspections on all U.S.-registered DC-9, MD-80 series, MD-90 series and Boeing 717 jetliners that use the mechanisms. The checks of the more than 1,100 planes must be completed by Monday night.

Air travel disruptions were said to be minor as planes were taken off the line a few at a time Friday for the inspections, which generally took several hours. It was not known how many of the inspections had been completed by Friday night.

Investigators say that on two Delta jetliners and one Alaska plane inspected and grounded Friday, the problems discovered involve metal slivers fouling the mechanisms. These slivers were similar to those found on the plane that crashed and on the two Alaska planes inspected and grounded on Thursday.

The bronze slivers apparently had been stripped from the gimbal nut that rides the stabilizer’s jackscrew--a thick threaded bolt about two feet long. What caused the stripping has not been determined.

The spinning jackscrew moves up and down through the nut, raising and lowering the leading edge of the stabilizer--the wing-like part of the jetliner that controls much of the up-and-down pitch of the plane’s nose.

On four other planes grounded Friday--one each from Alaska, American, Continental and Northwest--the problems involved the stabilizer mechanisms, but in all but one case, no details were available.

On that one--an MD-90 purchased by American during a takeover of Reno Air--the problem was said to involve an inadequately lubricated jackscrew. Sources said there was no damage to the jackscrew or gimbal nut, and after lubrication, the stabilizer was determined to be working properly and the plane was returned to service.

American said that during its service with Reno, the jetliner had been maintained by an outside contractor.

On the afternoon of Jan. 31, during radio conversations with air traffic controllers and airline maintenance personnel, the pilots of Alaska’s ill-fated Flight 261 said they were having trouble controlling the plane because of problems with the stabilizer.

The stabilizer eventually jammed in the full nose-down position, and 12 minutes later, despite the cockpit crew’s desperate efforts to maintain control, the sleek, twin-engine jetliner spiraled down into the sea.

The gimbal nut from Flight 261--recovered from the ocean floor late Thursday, several days after the plane’s jackscrew was retrieved--was found to have stripped threads, the National Transportation Safety Board said Friday.

The NTSB said several more significant pieces of wreckage from Flight 261 were recovered from the main debris zone on the ocean floor Friday, including an eight-foot-long section of the stabilizer and portions of hinged elevator panels on the trailing edge of the stabilizer.