Flight 261 crash may spur rule change: regular replacement for suspect MD-80 tail part
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Federal safety investigators looking into the crash of Alaska Airlines Flight 261 may recommend a key part of the tail on nearly 1,200 Boeing MD-80-series jets be automatically replaced at regular intervals instead of when they wear out.
The staff of the National Transportation Safety Board (NTSB) has discussed the idea, according to documents in a civil lawsuit stemming from the crash and a government official familiar with the investigation.
Investigators believe failure of a jackscrew mechanism led to the crash of Flight 261 on Jan. 31, 2000, killing all 88 passengers and crew when the MD-83 plunged into the Pacific Ocean off Southern California. The jackscrew controls the plane's horizontal stabilizer, the winglike structure in the tail that keeps the plane flying at the proper angle.
Presently, jackscrew mechanisms are replaced when they reach a wear limit measured in the thousandths of inches.
But reliability concerns about the test used to measure wear — along with the jackscrew's lack of a backup system — have spurred talk about taking the precautionary step of requiring automatic replacement.
The jackscrew mechanism, which can last for years, costs about $60,000 new, although one can be overhauled for less.
The NTSB's report on the cause of the crash and its safety recommendations are expected to be announced late this year. Any suggested changes would have to be adopted by the Federal Aviation Administration (FAA), which regulates commercial aviation.
Ted Lopatkiewicz, an NTSB spokesman, said the agency doesn't discuss staff deliberations. Staff recommendations must be accepted by the agency's five-member board before they are forwarded to the FAA.
But in a recent deposition in wrongful-death lawsuits stemming from the crash, Gerardo Hueto, Alaska's director of fleet safety, testified there have been a "couple of occasions in NTSB meetings" in which participants discussed making the jackscrew mechanism a "life-limited item" — that is, one replaced at specified times.
A government official, speaking on condition of anonymity, agreed the option is being considered within the NTSB.
On similar planes, the U.S. military replaces jackscrews every 14,000 flight hours, Hueto said. Military officials were not able to say immediately whether that procedure is for safety or to assure planes are always ready for action.
The MD-80 series is flown by airlines worldwide, along with 115 MD-90s that would be covered by any changes. Production of the twin-engine planes stopped in the late 1990s, after Boeing acquired the jets' maker, McDonnell Douglas, in 1997.
Boeing continues to make the 717, a smaller cousin of the MD-80 that incorporates a jackscrew mechanism. But heritage Boeing models such as the 737 use a different system to move the horizontal stabilizer, which includes a backup system.
Boeing declined comment on limiting the life span of jackscrew mechanisms, as did Alaska. Both are barred from public comment on the NTSB investigation until it is completed.
Privately, Boeing officials have expressed the view the jackscrew mechanism is safe as long as it is properly maintained, said people close to the company.
The MD-80 series and its predecessor, the DC-9, have flown for more than 35 years with only one failure of the mechanism: Flight 261. Safety-board investigators are looking at whether that plane's mechanism had been properly maintained.
Hueto testified that an internal NTSB study found the test that measures wear was unreliable, although some observers say errors tend to overstate wear. Mechanics attach a device to gauge wiggle between the 2-foot-long jackscrew and the nut, measuring thousandths of inches.
Although the study hasn't been made public, the board advised the FAA in October to require changes in the wear test. The FAA is studying the proposal, and airlines have taken measures to improve the test.
The board said it was concerned the test "may not be adequate to ensure consistent, accurate, and reliable measurements" of screw and nut wear.
Bernard Loeb, former director of the NTSB's Office of Aviation Safety, said agency staffers are looking at all aspects of the jackscrew mechanism.
The board might recommend making the jackscrew mechanism a life-limited item, Loeb said. Or it could require adjustments in the MD-80 series to assure horizontal stabilizers will continue operating if the jackscrew fails.
It could also call for design changes to Boeing 717s, Loeb added. "I don't think it would be appropriate to leave it as it is," he said.
If the NTSB recommends changes, it could have a bearing in the wrongful-death suits because both Alaska and Boeing are defendants. The case is scheduled to go to trial in January.
Steve Miletich can be reached at 206-464-3302 or smiletich@seattletimes.com.