SEATTLE (AP) -- The criminal investigation into the crash of Alaska Airlines Flight 261 is focusing on new details about mechanics' decisions not to replace the part of the plane now suspected as a factor in the crash, The Seattle Times reported Friday.
Details of those decisions, made in 1997, are revealed in airline maintenance records obtained by the newspaper.
At issue are two series of tests performed on the jet's jackscrew assembly and the time interval between them.
Flight 261 was en route to San Francisco from Puerto Vallarta when it crashed Jan. 31 into the Pacific Ocean off Los Angeles, killing all 88 people aboard. Five of the passengers were from Alaska.
The pilots on the flight had reported problems with the plane's horizontal stabilizer, a flap on the tail which is tilted by the jackscrew assembly to determine the pitch of the aircraft.
In an investigation separate from the criminal probe by the FBI and a grand jury in San Francisco, the National Transportation Safety Board is focusing on the jackscrew assembly as a possible cause of the crash.
According to the report in The Times, a crew at Alaska's Oakland, Calif., maintenance facility tested the plane's jackscrew assembly repeatedly before ordering it replaced because of wear.
A later crew performed new tests on the part, got lower wear readings and sent the plane into service after overturning the directive to replace the worn part.
This account differs from earlier accounts of the tests, The Times says, because it shows that the directive to replace the worn part was issued only after repeated testing.
The airline previously portrayed the later tests as routine retesting, without noting that the original order was based on multiple wear tests.
Furthermore, the interval between both series of tests -- the time it took the second crew to reverse the earlier crew's decision -- was more than two days, according to the records obtained by the newspaper.
Alaska Airlines and the NTSB previously has reported the reversal occurred within hours, but both now acknowledge that account was mistaken.
Both factors -- the nonroutine nature of the retests on the jackscrew assembly and the longer time it took to reverse the earlier crew's decision -- are significant because federal agents are trying to determine whether the later set of tests was legitimate, was manipulated by company workers to get the plane back into service without further inspections, or was subject to unreliable results.
Company officials declined comment on the records, citing the criminal investigation.
The jackscrew assembly consists of a nut that rides up and down a screw as it turns to lift and lower the stabilizer.
The newly disclosed records show the original wear test -- using a device that puts pressure on the screw to determine how much it wiggles in the nut -- was repeated several times, as specified on a work card, to ensure the reading was consistent.
The tests occurred Sept. 27, 1997 -- not Sept. 29, as the airline and the NTSB had previously said.
The test found the jackscrew and nut part to be close to its maximum wear limit, with .040 inches of deterioration on the threads -- close enough to prompt an inspector to issue a ''nonroutine work card'' or ''MIG-4,'' The Times said.
Had the measurement been any higher, the airline would have been required by its own FAA-approved rules to replace the part.
Following the tests, mechanics recommended replacing the part, but a written order to that effect was scratched out and replaced with a directive to re-evaluate the finding, the newspaper said.
The new directive was issued Sept. 30 -- more than 48 hours after the first.
During that span, a replacement jackscrew assembly wasn't available, and there is a question whether one was even ordered, The Times said, citing federal officials close to the criminal investigation.
Alaska Airlines officials have declined to discuss what steps were taken before the first directive was canceled, The Times said.
Subsequent tests apparently showed less wear on the part -- a finding of .033 inches of deterioration. At .034 inches of wear -- just .001 inch more -- the part is to be rechecked after every 1,000 flight hours, according to an Alaska maintenance manual, The Times said.
That would have meant the part would have been inspected repeatedly in the 28 months between the tests and the crash.
But at .033 inches of wear, the jackscrew was not due for inspection until June 2000. The plane did undergo a major maintenance check in January 1999, but the jackscrew assembly, which is inspected only in alternate major checks, was not part of that.
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