NTSB rejects Alaska theory on crash of Flight 261

The wrong grease didn't cause Alaska Airlines Flight 261 to crash, but a lack of grease probably was a key factor, federal safety investigators have concluded.

At a closed-door review Wednesday of the National Transportation Safety Board's crash investigation, experts ruled out that an incompatible type of grease might have caused corrosion of a key component known as the jackscrew in the MD-83 jet's tail.

However, the NTSB report, due later this year, is almost certain to say the crash in January 2000 stemmed from failure of a jackscrew that lacked proper lubrication, according to two people who attended the review and described its conclusions.

That finding would be a setback for Alaska Airlines and a victory for Boeing. For months, Alaska has sought to show that a Boeing-approved grease could have corroded key parts on the jet, a theory that would have shifted the focus away from the airline's maintenance practices.

A finding that there wasn't enough grease would place the focus on the plane's maintenance as well as standards of the Federal Aviation Administration.

The review, at NTSB headquarters in Washington, D.C., was attended by investigators, technical experts and representatives of Alaska and Boeing.

The group concluded that virtually all of the facts have been determined and are ready to be analyzed and put into a final report.

A 400-page draft already has been compiled, and investigators say they hope to release their report this fall.

Wednesday's meeting was a key step in the Flight 261 investigation, coming nearly 27 months after the Jan. 31, 2000, crash in which all 88 passengers and crew were killed when the MD-83 plunged into the Pacific Ocean off Southern California.

Participants reviewed the findings of several work groups that looked into different aspects of the crash. The safety board uses a party system to investigate aviation disasters, relying on technical expertise provided by airlines, airframe and engine makers and their suppliers, as well as unions representing pilots, mechanics and ground workers.

Laboratory tests failed to show that corrosion from grease played any role in the crash, said the two people who attended the review and requested anonymity.

"It kind of takes that off the table," said one official, although some additional testing will be done to satisfy all parties.

But at this point, investigators have concluded that a lack of grease in critical areas of the plane's jackscrew assembly caused the mechanism to strip threads from its nut, the official said.

The jackscrew moves the horizontal stabilizer, the wing-like structure in the tail section that control's the plane's angle of flight.

But investigators will probably never know why there was a lack of lubrication because task cards filled out by Alaska mechanics show grease was applied at required intervals.

"We're never going to know that," the official said.

The report also is likely to raise questions about the reliability of the test used to measure wear of the jackscrew.

During a 1997 maintenance check on the plane, a senior Alaska mechanic recommended the jackscrew assembly be replaced because it was just under its wear limit.

Other mechanics overruled him after doing more checks, finding the part to be well within its limit.

The FBI conducted a criminal investigation into the check, but did not uncover illegal activity. The circumstances, however, led the NTSB to closely examine the reliability of the wear test.

The report this fall also may address whether Alaska's intervals for testing jackscrew wear and lubricating the part were too long, even though they fell within parameters approved by the Federal Aviation Administration, said the two people who attended the review.

They said Alaska's chief representative to the crash investigation continued to push the corrosion theory at Wednesday's meeting, but in a more muted fashion than at earlier sessions.

Another Alaska representative was removed from the inquiry late last year after the safety board concluded his work on the grease issues had "delayed and frustrated" the inquiry.

Alaska declined comment on the meeting, citing safety-board rules that prohibit parties from discussing the investigation until it is completed.

Alaska has contended a grease called AeroShell 33 may have played a role in the failure of the jackscrew assembly.

The carrier originally used Mobilgrease 28 on its MD-80 fleet, as recommended by McDonnell Douglas, the plane's builder. When Boeing acquired McDonnell Douglas in 1997, Alaska asked Boeing if it could switch to AeroShell 33, which Boeing has long recommended for its planes.

Boeing said it had "no technical objection" to the switch, although it advised Alaska to monitor the change. The Federal Aviation Administration approved the move with little review.

After the crash, Alaska suggested that AeroShell might have corroded the jackscrew assembly, possibly when mixed with remnants of Mobilgrease 28.

Alaska later stopped using AeroShell 33 on its MD-80 fleet at the FAA's request.

The NTSB is likely to fault Alaska and the FAA for the way the original switch occurred, but not cite any one grease or combination of greases as causing the crash, said one of the people at the review.

All staff findings are subject to final approval by the five appointed members of the safety board.

Incompatible grease has been cited in dozens of wrongful-death suits filed by relatives of Flight 261 victims.

The pending suits also allege poor maintenance and faulty design of the plane led to the crash.

Steve Miletich can be reached at 206-464-3302 or smiletich@seattletimes.com