MolaKule
Staff member
Finger-pointing intensifies over crash of Flight 261
- Alaska Airlines blames grease it used; Boeing says it was bad maintenance
Seattle Post-Intelligencer 09/23/02
author: James Wallace
With the federal investigation into the crash of Alaska Airlines Flight 261 quickly nearing an end,
the various parties involved in assisting the National Transportation Safety Board in its investigation
have weighed in with opinions about what caused or contributed to the accident.
Alaska Airlines, in a not-yet-public submission to the NTSB obtained by the Post-Intelligencer,
pointed the blame toward The Boeing Co.
The Seattle-based carrier has pushed the theory that a Boeing-approved grease, not its own
maintenance shortcomings, led to extreme wear and the eventual failure of a critical flight control
mechanism in the tail of the jetliner.
As might be expected, the parties don't see eye to eye.
Boeing, in its submission, said the kind of grease that Alaska used played no role in the crash, but
that the lack of lubrication by Alaska did. A pilots group criticizes not only the airline but also a
lack of federal oversight.
The crash off the Southern California coast near Point Mugu on Jan. 31, 2000, killed all 88 people
aboard the MD-83 jetliner. Although the safety board has not yet ruled on the probable cause,
sources say the board's investigators have concluded that a lack of lubrication by Alaska, and not
the kind of grease used, likely led to the failure of a jackscrew that controlled the horizontal
stabilizer.
Late last year, the board took the unusual action of removing from the investigation an Alaska
representative who had strongly advocated the wrong-grease theory.
Alaska is one of several parties to the crash investigation that recently were allowed to submit their
views about the accident to the safety board in writing.
Some of the submissions were highly critical of Alaska and the role of the FAA in allowing the
nation's ninth-largest airline to increase the interval between inspections of the part that failed as
well as the time between lubrications.
"The Alaska Airlines maintenance program was deficient in that it failed to address a safety of flight
condition through the extension of maintenance intervals," the Aircraft Mechanics Fraternal
Association said in its submission to the board.
The fact that federal regulators give the airlines wide latitude in setting their maintenance practices
and schedules is a critical issue that came up early in the Flight 261 investigation and which the
safety board is expected to address in detail in its final report on the crash.
"The factual record indicates that had the accident not occurred on this particular flight, it would
have occurred in the very near future," one of the parties, the Air Line Pilots Association, said in its
submission.
"The condition of the jackscrew components was the result of years of mismanagement and poor
oversight on the part of Alaska Airlines and the Federal Aviation Administration."
The board's investigators are now preparing a draft final report of several hundred pages that will
likely be presented to board members at a public meeting late this year.
All indications are that the report will cite several factors for the crash, including inadequate
maintenance by Alaska and insufficient oversight of the airline by the FAA. The report is also
expected to question the design and certification of the jackscrew mechanism itself.
While the parties to the investigation are not allowed to participate in drafting the board's final
report, they are permitted to submit their opinions in written form. The parties did so at the end of
August.
The safety board will soon make these submissions part of the Flight 261 public record. The
Seattle Post-Intelligencer obtained the documents of three key parties to the investigation -- Alaska
Airlines, Boeing and the Aircraft Mechanics Fraternal Association -- from sources. The document
of a fourth party, the Air Line Pilots Association, was posted on its Web site.
The cause of Flight 261's crash has been known since the pieces of the tail assembly were first
pulled from the Pacific within a few days of the accident. The question that remains is why the
jackscrew mechanism in the tail came apart in flight, causing the plane to plunge out of control
while en route to Seattle from Puerto Vallarta, Mexico.
The jackscrew is in the plane's tail, where it controls a horizontal stabilizer, which resembles a small
wing on the plane's tail.
The stabilizer, used to maintain level flight, is adjusted by the jackscrew, a mechanism that
resembles the threaded rod on many garage door openers. An electric motor rotates the jackscrew
through a large nut to tilt the stabilizer up and down. Wreckage from Flight 261 showed that the
threads in the nut were stripped.
Metallic shavings found on the jackscrew from Flight 261 were determined to have come from the
nut.
Boeing, in its 25-page submission to the safety board, said the part failed because of a lack of
lubrication.
"Based on factual evidence and the analytical studies conducted for this investigation, Boeing
believes that operation of the jackscrew unit on (the plane) for an extended period without
adequate lubrication resulted in a high wear rate, and combined with the operator's extended
interval for endplay inspection, resulted in the loss of the acme nut threads, leading to loss of
control of the airplane."
Alaska changed lubrication grease in January 1998 from Mobil 28, which had been approved by
McDonnell Douglas for use on MD-80 planes like the one that crashed, to Aeroshell 33, which
was developed by Boeing for use on its jets.
Alaska operates both Boeing and McDonnell Douglas jets and wanted to simplify its maintenance
after Boeing acquired McDonnell Douglas in 1997.
"Based on service experience and extensive testing performed by the NTSB," Boeing said in its
submission, "there is no evidence that the wear rate of the accident acme nut was adversely
affected by the operator's selection of Aeroshell 33 lubricant, or that any acme nut material was
lost due to corrosion or chemical reaction as a result of Aeroshell Grease 33, Mobilgrease 28, or
any combination of these two greases."
Boeing was not alone in that view.
"The change to Aeroshell 33 from Mobilgrease 28 by Alaska Airlines was significant with respect
to the lack of oversight on the part of the FAA and the failure to follow proper procedures on the
part of Alaska Airlines," the pilots association wrote.
"However, we must add here that the grease change, in and off itself, did not have any significant
impact on the lubricating abilities or the wear characteristics of the component. In fact, the NTSB's
grease group determined that Aeroshell 33 actually provided better friction characteristics than
Mobilgrease 28 and mixtures of the two greases had little effect on the lubricating properties."
Not long after the crash, the FAA ordered Alaska to switch back to Mobil 28. Alaska, the only
major airline to lubricate its MD-80 jets with Aeroshell 33, had provided inadequate
documentation to support the change, the FAA said.
During the NTSB public hearing in December 2000, testimony showed that Alaska signed off on
what amounted to slipshod paperwork for the change in lubricating grease. In its recent submission,
Alaska acknowledged it did not follow its own procedures for the grease change but said that had
nothing to do with the crash.
"While it is clear that Alaska personnel did not follow internal procedures in making the change to
Aeroshell 33, this oversight does not change the fact that erroneous and incomplete information
about the grease was provided to Alaska," the airline said in its submission.
Alaska criticized grease testing performed on behalf of the board. It also was critical of comments
by former NTSB Chairman Jim Hall, who told reporters soon after the tail wreckage of Flight 261
was pulled from the ocean that the jackscrew mechanism appeared to lack lubrication.
"Unfortunately, this erroneous public announcement led some to conclude that Alaska failed to
properly lubricate the jackscrew assembly and, as a result, the scope and direction of this
investigation has been unduly affected," Alaska wrote in its submission.
Alaska said that even after the recovered jackscrew assembly was washed down, some grease
was found on the assembly, indicating it had been lubricated.
At the time of the crash, Alaska was greasing its jackscrews every nine calendar months, or after
about 2,550 flight hours.
In 1984, McDonnell Douglas had recommended the jackscrew mechanism be lubricated every
600 flight hours. But over the years, the interval between lubrications was allowed to change, with
the approval of the FAA. Before Flight 261 crashed, Boeing was recommending intervals of 600
to 900 hours, or 3,600 hours, between MD-80 jackscrew lubrications. The interval used
depended on the type of maintenance program airlines followed.
In its submission to the safety board, the Aircraft Mechanics Fraternal Association criticized the
process that allowed some carriers to stretch out the lubrication and maintenance schedule.
It described that as an "unrealistic extension of maintenance intervals without sufficient data."
Another key maintenance issue was the frequency of checks of the jackscrew and nut for wear.
Boeing was recommending the jackscrew be tested for wear every 30 months or 7,200 flight
hours, whichever came first. This is known as an "end-play" check. But the FAA gave Alaska
permission to drop the hourly requirement.
Alaska, however, was soon using its jets more hours per day. So when Flight 261 crashed, it had
accumulated 8,884 hours since the jackscrew was last inspected for wear.
A lead mechanic for Alaska had ordered the jackscrew be replaced during a heavy maintenance
check of the same plane at Alaska's Oakland, Calif., facility Sept. 27, 1997, but it was left in the
plane after other mechanics retested it and determined it to be well within wear limits.
The Boeing-approved procedures and tools used to test for wear of the jackscrew assembly are
questioned by Alaska and other parties in their submissions to the board. After the crash, the FAA
ordered airlines to check the jackscrew mechanism for excessive wear every 2,000 flight hours
and report the measurements from this end-play test to Boeing after every check.
Investigations found that the method of performing the end-play checks can increase or decrease
the likelihood of an error in measuring wear.
"The board is concerned that the current end-play check procedure may not be adequate to ensure
consistent, accurate and reliable measurements of acme screw and nut wear," the board said late
last year in a letter to the FAA.
In its submission, Alaska recommended that the current method for checking wear of the
jackscrew assembly be replaced with an X-ray or ultrasound procedure. Boeing said in its
submission that it continues to work on improvements for the end-play checks.
The safety board has not yet announced a date for the meeting at which it will consider the final
draft report on the Flight 261 crash. A person with knowledge of the investigation said the meeting
is planned in December, before Christmas.
In its submission to the board, the mechanics association touched on a point that is often made by
veteran accident investigators -- that an airline crash involves a chain of events.
"Like most accidents, the loss of Alaska Airlines Flight 261 was not the result of a single individual
in the performance of their assigned task," the association said.
"Rather, the cause is related to the failure of a 'system' that allowed an airplane to be certified as
airworthy without sufficient redundancy and a maintenance program that was deficient in detecting
a safety of flight condition."
- Alaska Airlines blames grease it used; Boeing says it was bad maintenance
Seattle Post-Intelligencer 09/23/02
author: James Wallace
With the federal investigation into the crash of Alaska Airlines Flight 261 quickly nearing an end,
the various parties involved in assisting the National Transportation Safety Board in its investigation
have weighed in with opinions about what caused or contributed to the accident.
Alaska Airlines, in a not-yet-public submission to the NTSB obtained by the Post-Intelligencer,
pointed the blame toward The Boeing Co.
The Seattle-based carrier has pushed the theory that a Boeing-approved grease, not its own
maintenance shortcomings, led to extreme wear and the eventual failure of a critical flight control
mechanism in the tail of the jetliner.
As might be expected, the parties don't see eye to eye.
Boeing, in its submission, said the kind of grease that Alaska used played no role in the crash, but
that the lack of lubrication by Alaska did. A pilots group criticizes not only the airline but also a
lack of federal oversight.
The crash off the Southern California coast near Point Mugu on Jan. 31, 2000, killed all 88 people
aboard the MD-83 jetliner. Although the safety board has not yet ruled on the probable cause,
sources say the board's investigators have concluded that a lack of lubrication by Alaska, and not
the kind of grease used, likely led to the failure of a jackscrew that controlled the horizontal
stabilizer.
Late last year, the board took the unusual action of removing from the investigation an Alaska
representative who had strongly advocated the wrong-grease theory.
Alaska is one of several parties to the crash investigation that recently were allowed to submit their
views about the accident to the safety board in writing.
Some of the submissions were highly critical of Alaska and the role of the FAA in allowing the
nation's ninth-largest airline to increase the interval between inspections of the part that failed as
well as the time between lubrications.
"The Alaska Airlines maintenance program was deficient in that it failed to address a safety of flight
condition through the extension of maintenance intervals," the Aircraft Mechanics Fraternal
Association said in its submission to the board.
The fact that federal regulators give the airlines wide latitude in setting their maintenance practices
and schedules is a critical issue that came up early in the Flight 261 investigation and which the
safety board is expected to address in detail in its final report on the crash.
"The factual record indicates that had the accident not occurred on this particular flight, it would
have occurred in the very near future," one of the parties, the Air Line Pilots Association, said in its
submission.
"The condition of the jackscrew components was the result of years of mismanagement and poor
oversight on the part of Alaska Airlines and the Federal Aviation Administration."
The board's investigators are now preparing a draft final report of several hundred pages that will
likely be presented to board members at a public meeting late this year.
All indications are that the report will cite several factors for the crash, including inadequate
maintenance by Alaska and insufficient oversight of the airline by the FAA. The report is also
expected to question the design and certification of the jackscrew mechanism itself.
While the parties to the investigation are not allowed to participate in drafting the board's final
report, they are permitted to submit their opinions in written form. The parties did so at the end of
August.
The safety board will soon make these submissions part of the Flight 261 public record. The
Seattle Post-Intelligencer obtained the documents of three key parties to the investigation -- Alaska
Airlines, Boeing and the Aircraft Mechanics Fraternal Association -- from sources. The document
of a fourth party, the Air Line Pilots Association, was posted on its Web site.
The cause of Flight 261's crash has been known since the pieces of the tail assembly were first
pulled from the Pacific within a few days of the accident. The question that remains is why the
jackscrew mechanism in the tail came apart in flight, causing the plane to plunge out of control
while en route to Seattle from Puerto Vallarta, Mexico.
The jackscrew is in the plane's tail, where it controls a horizontal stabilizer, which resembles a small
wing on the plane's tail.
The stabilizer, used to maintain level flight, is adjusted by the jackscrew, a mechanism that
resembles the threaded rod on many garage door openers. An electric motor rotates the jackscrew
through a large nut to tilt the stabilizer up and down. Wreckage from Flight 261 showed that the
threads in the nut were stripped.
Metallic shavings found on the jackscrew from Flight 261 were determined to have come from the
nut.
Boeing, in its 25-page submission to the safety board, said the part failed because of a lack of
lubrication.
"Based on factual evidence and the analytical studies conducted for this investigation, Boeing
believes that operation of the jackscrew unit on (the plane) for an extended period without
adequate lubrication resulted in a high wear rate, and combined with the operator's extended
interval for endplay inspection, resulted in the loss of the acme nut threads, leading to loss of
control of the airplane."
Alaska changed lubrication grease in January 1998 from Mobil 28, which had been approved by
McDonnell Douglas for use on MD-80 planes like the one that crashed, to Aeroshell 33, which
was developed by Boeing for use on its jets.
Alaska operates both Boeing and McDonnell Douglas jets and wanted to simplify its maintenance
after Boeing acquired McDonnell Douglas in 1997.
"Based on service experience and extensive testing performed by the NTSB," Boeing said in its
submission, "there is no evidence that the wear rate of the accident acme nut was adversely
affected by the operator's selection of Aeroshell 33 lubricant, or that any acme nut material was
lost due to corrosion or chemical reaction as a result of Aeroshell Grease 33, Mobilgrease 28, or
any combination of these two greases."
Boeing was not alone in that view.
"The change to Aeroshell 33 from Mobilgrease 28 by Alaska Airlines was significant with respect
to the lack of oversight on the part of the FAA and the failure to follow proper procedures on the
part of Alaska Airlines," the pilots association wrote.
"However, we must add here that the grease change, in and off itself, did not have any significant
impact on the lubricating abilities or the wear characteristics of the component. In fact, the NTSB's
grease group determined that Aeroshell 33 actually provided better friction characteristics than
Mobilgrease 28 and mixtures of the two greases had little effect on the lubricating properties."
Not long after the crash, the FAA ordered Alaska to switch back to Mobil 28. Alaska, the only
major airline to lubricate its MD-80 jets with Aeroshell 33, had provided inadequate
documentation to support the change, the FAA said.
During the NTSB public hearing in December 2000, testimony showed that Alaska signed off on
what amounted to slipshod paperwork for the change in lubricating grease. In its recent submission,
Alaska acknowledged it did not follow its own procedures for the grease change but said that had
nothing to do with the crash.
"While it is clear that Alaska personnel did not follow internal procedures in making the change to
Aeroshell 33, this oversight does not change the fact that erroneous and incomplete information
about the grease was provided to Alaska," the airline said in its submission.
Alaska criticized grease testing performed on behalf of the board. It also was critical of comments
by former NTSB Chairman Jim Hall, who told reporters soon after the tail wreckage of Flight 261
was pulled from the ocean that the jackscrew mechanism appeared to lack lubrication.
"Unfortunately, this erroneous public announcement led some to conclude that Alaska failed to
properly lubricate the jackscrew assembly and, as a result, the scope and direction of this
investigation has been unduly affected," Alaska wrote in its submission.
Alaska said that even after the recovered jackscrew assembly was washed down, some grease
was found on the assembly, indicating it had been lubricated.
At the time of the crash, Alaska was greasing its jackscrews every nine calendar months, or after
about 2,550 flight hours.
In 1984, McDonnell Douglas had recommended the jackscrew mechanism be lubricated every
600 flight hours. But over the years, the interval between lubrications was allowed to change, with
the approval of the FAA. Before Flight 261 crashed, Boeing was recommending intervals of 600
to 900 hours, or 3,600 hours, between MD-80 jackscrew lubrications. The interval used
depended on the type of maintenance program airlines followed.
In its submission to the safety board, the Aircraft Mechanics Fraternal Association criticized the
process that allowed some carriers to stretch out the lubrication and maintenance schedule.
It described that as an "unrealistic extension of maintenance intervals without sufficient data."
Another key maintenance issue was the frequency of checks of the jackscrew and nut for wear.
Boeing was recommending the jackscrew be tested for wear every 30 months or 7,200 flight
hours, whichever came first. This is known as an "end-play" check. But the FAA gave Alaska
permission to drop the hourly requirement.
Alaska, however, was soon using its jets more hours per day. So when Flight 261 crashed, it had
accumulated 8,884 hours since the jackscrew was last inspected for wear.
A lead mechanic for Alaska had ordered the jackscrew be replaced during a heavy maintenance
check of the same plane at Alaska's Oakland, Calif., facility Sept. 27, 1997, but it was left in the
plane after other mechanics retested it and determined it to be well within wear limits.
The Boeing-approved procedures and tools used to test for wear of the jackscrew assembly are
questioned by Alaska and other parties in their submissions to the board. After the crash, the FAA
ordered airlines to check the jackscrew mechanism for excessive wear every 2,000 flight hours
and report the measurements from this end-play test to Boeing after every check.
Investigations found that the method of performing the end-play checks can increase or decrease
the likelihood of an error in measuring wear.
"The board is concerned that the current end-play check procedure may not be adequate to ensure
consistent, accurate and reliable measurements of acme screw and nut wear," the board said late
last year in a letter to the FAA.
In its submission, Alaska recommended that the current method for checking wear of the
jackscrew assembly be replaced with an X-ray or ultrasound procedure. Boeing said in its
submission that it continues to work on improvements for the end-play checks.
The safety board has not yet announced a date for the meeting at which it will consider the final
draft report on the Flight 261 crash. A person with knowledge of the investigation said the meeting
is planned in December, before Christmas.
In its submission to the board, the mechanics association touched on a point that is often made by
veteran accident investigators -- that an airline crash involves a chain of events.
"Like most accidents, the loss of Alaska Airlines Flight 261 was not the result of a single individual
in the performance of their assigned task," the association said.
"Rather, the cause is related to the failure of a 'system' that allowed an airplane to be certified as
airworthy without sufficient redundancy and a maintenance program that was deficient in detecting
a safety of flight condition."
