NTSB tests grease used on Alaska airplanes

The National Transportation Safety Board is testing the grease Alaska Airlines has been using to lubricate the jackscrew assemblies of its MD-80 jets to see if under certain circumstances the grease can corrode airplane parts.

The NTSB's focus on grease comes after Alaska recently conducted tests of its own without first notifying the federal agency - a breach of protocol in the investigation of the Jan. 31 crash of Alaska Flight 261.

The jackscrew assembly is part of the MD-80's horizontal stabilizer, the wing-like structure on the tail that controls the up-and-down pitch of the plane's nose. Failure of the jackscrew is suspected as a cause of the crash off Southern California in which 88 people - many from the Seattle area - perished.

Alaska's tests indicated that the specific type of grease it switched to three years ago, called AeroShell 33, may not be compatible with the type of grease it had been using, called Mobilgrease 28, said sources close to the NTSB investigation.

Alaska's tests showed that when mixed with remnants of Mobilgrease 28, AeroShell 33 forms a pasty substance that picks up dirt and foreign material that becomes very gritty, said a senior Alaska mechanic familiar with the airline's analysis.

Sources said that some inside the company theorize that the pasty substance may have acted like a grinding compound on the jackscrew.

Airline officials also suggested that AeroShell 33 may be corrosive to copper, an element used to make the jackscrew's bronze gimbal nut, the sources said.

The jackscrew is a 2-foot-long, 1 1/2-inch-diameter threaded shaft made of hardened steel. It moves up and down through a stationary gimbal nut to adjust the stabilizer.

Bronze threads from Flight 261's gimbal nut were found stripped and twisted around its jackscrew. Although there was some grease on the jackscrew, there was none on portions of the jackscrew that normally came in contact with the gimbal nut.

The NTSB has now undertaken examinations of its own to test the "import of any possible incompatibility" between AeroShell 33 and Mobilgrease 28, said NTSB spokesman Terry Williams.

The agency is also looking into the possibility of AeroShell 33 being corrosive to copper, Williams said. "Further, the composition of the remnants of grease found on the jackscrew and gimbal nut is being studied," Williams said. "We do not know the import of any of this - including any wider safety issues - yet."

NTSB Chairman James Hall recently intervened in the investigation to admonish Alaska's senior executives for conducting the unauthorized grease test.

"Chairman Hall has spoken to (Alaska) CEO John Kelly and president William S. Ayer to express his displeasure with what occurred," Williams said.

The NTSB uses a "party system" to solve aviation disasters. The system relies on technical expertise provided by airlines, frame and engine makers and their suppliers, and labor unions representing pilots, mechanics and ground workers. In exchange for the right to be at the heart of the investigation, the potentially culpable parties agree to take direction from the NTSB's investigator-in-charge and to divulge everything relevant to the probe.

Alaska spokesman Jack Evans said the airline has "cooperated fully with the NTSB investigation.

"If there are concerns about any of our actions, we'll gladly discuss those with the NTSB and any of the parties to the investigation," Evans said. "But we won't do so in the media." Evans would not say why Alaska switched to AeroShell 33 and declined to discuss how the airline may be addressing any grease-compatibility issues that might apply to its fleet of jets.

"Questions pertaining to the type of grease used on the jackscrew assemblies of our MD-80 fleet is a matter currently under review by the NTSB, so we'll have to defer to the safety board to discuss those matters," Evans said.

In 1997, Alaska asked Boeing - which had bought McDonnell Douglas, producer of MD-80s - about switching to AeroShell 33 as the lubricant for the jackscrew, said Boeing spokesman John Thom.

Boeing reviewed previous testing and the service history of AeroShell 33, a multipurpose aviation lubricant designed for airplane roller bearings, actuator screws and other moving parts, Thom said. In September 1997, Boeing advised the airline in writing that it had "no technical objection" to the switch, Thom said.

Williams, the NTSB spokesman, said Alaska has returned to using Mobilgrease 28 on its MD-80 stabilizer jackscrews.

Some plaintiffs' attorneys suspect the airline is maneuvering to deflect at least some of the liability for the crash of Flight 261 onto the aircraft manufacturer.

"It's a total ploy," said Art Wolk, a plaintiff lawyer from Philadelphia. "Alaska wants the plaintiffs to focus on Boeing to bring them to the table on any kind of a settlement."

Byron Acohido's phone message number is 206-464-2352. His e-mail address is bacohido@seattletimes.com.