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Alaska Airlines maintenance records raise new questions
23 aircraft from nine airlines fail inspections
WASHINGTON (CNN) -- New and serious questions about maintenance practices at Alaska Airlines have been raised in connection with records uncovered by the National Transportation Safety Board while the agency has been investigating the crash of Flight 261.
A stabilizer malfunction is believed to have caused Flight 261 to crash off the California coast last month, killing all 88 people aboard.
The horizontal stabilizers are wing-like structures located on the tail of the aircraft, which control the plane's pitch, pointing the nose of the aircraft up or down. A gimbal nut moves up and down a jackscrew to change the stabilizers' position.
The jackscrew and gimbal nut were found to be damaged when they were recovered from the wreckage of Flight 261.
The NTSB said a heavy maintenance check at Alaska Airlines' Oakland maintenance facility in September of 1997 showed the gimbal nut on the plane that flew Flight 261 to be worn to the maximum acceptable limits and indicated plans to replace it.
But the records also show the same part was inspected five times the next day, September 30, 1997, and was repeatedly found to be well within limits for continued use.
"The first person could have used a piece of equipment to measure it with -- it could have been a piece of equipment that was out of calibration," said Bob Vandel of the Flight Safety Foundation.
During that last major inspection of the horizontal stabilizer on the plane, the gimbal nut was not replaced.
Alaska Airlines defends inspections
Alaska Airlines is defending its inspection record, saying signs of wear found on the gimbal nut were considered acceptable by the plane's manufacturer.
The initial measurement during the September 1997 check showed play between the jackscrew and the gimbal nut of 40/1000ths of an inch, the maximum allowed. Several later readings produced a "consistent" measurement of 33/1000ths of an inch, said Jack Evans, Alaska Airlines spokesman.
"There was actually no repair required," Evans said.
"The instructions from the manufacturer allow you to release an aircraft back into service at the upper end of the range.
"Reports that this was a failed or troubled part are totally inaccurate. The manufacturer builds in a tolerance for that part that is much greater than that," he said. "It did not signal any cause for concern here."
Service facility under separate probe
The significance of the previous inspection information is continuing to be evaluated by the NTSB.
"No determination has been made as to whether this information has any bearing on the accident," said NTSB chairman Jim Hall in a written statement.
The Oakland facility has been the subject of federal investigations over allegations some maintenance records may have been falsified.
A federal grand jury has been investigating a whistle-blower's complaints of maintenance irregularities at the service center. However, the Federal Aviation Administration said earlier this month that the jet that crashed was not involved in that investigation.
From metal shavings to lack of lubricant
Most of the FAA-mandated inspections of tail assemblies on nearly 1,100 MD-80 series jetliners have been completed. The FAA reported 23 planes from several airlines were found to have problems or potential problems.
"I don't know how significant those maintenance problems are, but if any one of them was significant, we may have eliminated one accident," said Vandel.
The FAA said the following airlines reported finding problems during the recent inspections of the jackscrew mechanisms associated with horizontal stabilizers of planes in the MD-80 series:
Suspect jackscrews removed from aircraft were being turned over to the FAA. Some were already being evaluated at the NTSB laboratory.
The FAA said Monday it could shorten the 30-day period it gave carriers for a more detailed check of the wear between the jackscrew and the nut once the agency examines parts taken from planes during the first stage of the inspection. If problems are found, the agency may require that the inspections be completed in less than 30 days.
"It's an option that we have," said FAA spokesman Paul Takemoto.
The agency has already increased the frequency of regular jackscrew inspections from every eight months to about every three months.
The eight Alaska Airlines planes found with problems were grounded.
In other cases, though, some airlines said they put their planes back into service if the only problem was a gritty residue found around the jackscrews that may prove to be from normal wear.
The NTSB says it will continue to review the maintenance records of Alaska Airlines in an effort to determine if there are maintenance or operational practices that contributed to the large number of planes with problems in that area.
The lawsuit filed Monday in U.S. District Court in Chicago by attorney Robert Clifford charged the airline with negligence, alleging the pilots bypassed nine viable landing sites in favor of "trouble-shooting" the stabilizer in the air.
Other defendants named in the lawsuit were plane manufacturers Boeing Co. of Seattle and McDonnell Douglas of St. Louis, which is now owned by Boeing.
Alaska Airlines probe focuses on 1997 inspection of stabilizer jackscrew
Flight Safety Foundation
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