+1 to that. That failure didn't have to be fatal.
Alaska flight 261
- Thread starter GON
- Start date
And again manually greasing an acme screw and bronze nut is just plain NUTS, for a passenger aircraft. Guess all missed what I posted above.
That is a very creative interpretation not supported by any actual facts or the NTSB.
So, that's not my interpretation. Dozens of points to the fact the lack of jackscrew maintenance (lubrication, inspection, overhaul) was the proximate cause, lack of redundancy was a cause, and lack of maintenance policies including overhauls, signoffs, and inspections was the cause. Here's the summary:
Relevant NTSB summary findings: http://iasa.com.au/folders/Breaking_News/hotoffthepress/ntsbfindings.html
1-18: Summary - the jackscrew worn threads from inadequate lubrication caused critical loss of control.
19. The acme nut threads on the accident airplane's horizontal stabilizer jackscrew assembly wore at an excessive rate.
21. There was no effective lubrication on the acme screw and nut interface at the time of the Alaska Airlines flight 261 accident.
22. The excessive and accelerated wear of the accident jackscrew assembly acme nut threads was the result of insufficient lubrication, which was directly causal to the Alaska Airlines flight 261 accident.
23. Alaska Airlines' extension of its lubrication interval for its McDonnell Douglas MD-80 horizontal stabilizer components, and the FAA's approval of that extension, the last of which was based on Boeing's extension of the recommended lubrication interval increased the likelihood that a missed or inadequate lubrication would result in excessive wear of jackscrew assembly acme nut threads and, therefore, was a direct cause of the excessive wear and contributed to the Alaska Airlines flight 261 accident.
24. When lubricating the jackscrew assembly, removal of used grease from the acme screw before application of fresh grease will increase the effectiveness of the lubrication.
26. If the jackscrew assembly lubrication procedure was a required inspection item for which an inspector's signoff is needed, the potential for unperformed or improperly performed lubrications would be reduced.
27. Alaska Airlines' extension of the end play check interval, and FAA's approval of the extension, allowed the accident acme nut threads to wear to failure without the opportunity for detection and, therefore, was a direct cause of the excessive wear and contributed to the Alaska Airlines flight 261 accident.
29. The existing process by which manufacturers revise recommended maintenance task intervals and by which airlines establish and revise these intervals does not include task-by-task engineering analysis and justification and, therefore, allows for the possibility of inappropriate interval extensions for potentially critical maintenance tasks.
30. Because of the possibility that higher-than-expected wear could cause excessive wear in less than 2,000 flight hours and the additional possibility that an end play check could be unperformed or improperly performed, the current 2,000-flight-hour end play check interval specified in Airworthiness Directive 2000-15-15 may be inadequate to ensure the safety of the Douglas DC-9, McDonnell Douglas MD-80/90, and Boeing 717 fleet.
32. Until August 2000, Alaska Airlines used a fabricated restraining fixture that did not meet Boeing specifications; however, the Safety Board could not determine whether the use of this noncompliant fixture generated an inaccurate end play measurement during the last end play check or whether the use of this fixture contributed to the accident.
34. Deficiencies in the overhaul process increase the likelihood that jackscrew assemblies may be improperly overhauled.
35. The absence of a requirement to record or inform customers of the end play measurement of an overhauled jackscrew assembly could result in an operator unknowingly returning a jackscrew assembly to service with a higher-than-expected end play measurement.
38. The dual-thread design of the acme screw and nut does not provide redundancy with regard to wear.
39. The design of the Douglas DC-9, McDonnell Douglas MD-80/90, and Boeing 717 horizontal stabilizer jackscrew assembly did not account for the loss of the acme nut threads as a catastrophic single-point failure mode. The absence of a fail-safe mechanism to prevent the catastrophic effects of total acme nut thread loss contributed to the Alaska Airlines flight 261 accident.
40. When a failure could have catastrophic results, it is not appropriate to rely on maintenance and inspection intervention to prevent the failure from occurring if a practicable design alternative could eliminate the catastrophic effects of the failure mode. (TO BE REVISED)
41. Douglas DC-9, McDonnell Douglas MD-80/90, and Boeing 717 series airplanes, and if found necessary other transport category airplanes, should be modified to ensure that loss of the horizontal stabilizer trim system's jackscrew assembly acme nut threads or other control assembly does not preclude continued safe flight and landing.
42. Catastrophic single-point failure modes should be prohibited in the design of all future airplanes with horizontal stabilizer trim systems, regardless of whether any element of that system is considered structure rather than system or is otherwise considered exempt from certification standards for systems.
43. The certification requirements applicable to transport-category airplanes should fully consider and address the consequences of failures resulting from wear.
44. At the time of the flight 261 accident, Alaska Airlines' maintenance program had widespread systemic deficiencies.
45. The FAA did not fulfill its responsibility to properly oversee the maintenance operations at Alaska Airlines, and at the time of the Alaska Airlines flight 261 accident, Federal Aviation Administration surveillance of Alaska Airlines had been deficient for at least several years.
PROBABLE CAUSE
The National Transportation Safety Board determines that the probable cause of this accident was a loss of airplane pitch control resulting from the in-flight failure of the horizontal stabilizer trim system jackscrew assembly's acme nut threads. The thread failure was caused by excessive wear resulting from Alaska Airlines' insufficient lubrication of the jackscrew assembly.
Contributing to the accident was
(1) Alaska Airlines' extended lubrication interval, and the FAA's approval of that extension, which increased the likelihood that an unperformed or inadequate lubrication would result in excessive wear of the acme nut threads; and
(2) Alaska Airlines' extended end play check interval, and the FAA's approval of that extension, which allowed the excessive wear of the acme nut threads to progress to failure without the opportunity for detection.
(3) Contributing also to the accident was the absence on the MD-80 of a fail-safe mechanism to prevent the catastrophic effects of total acme nut thread loss.
Further citations from Wikipedia:
Alaska Airlines Flight 261 - Wikipedia
In NTSB board member John J. Goglia's statement for the final report, which was concurred with by the other three board members, he wrote:
Quite obviously, as I stated, this is penny-pinching foolishness gambling with planes full of humans. Every step in the chain of causation - from failing to create (or demand of Boeing) a redundant system for a critical part, to cutting maintenance on critical non-redundant parts (the whistleblower said that the jackscrew maintenance was a 4 hour job but cut by Alaska to just 1 hour), to not having overhauls or supervisor inspections, etc. is a COST CUTTING measure.
In the end, Alaska (for which I am a shareholder) unconscionably put a few dollars in front of the lives of millions of travelers and people on the ground. The few tens of thousands of dollars on the service life of these planes, doing proper engineering and service, directly killed 80+ and put in jeopardy untold numbers of others. Because they were too cheap to pull a plane for 4 hours to lubricate the poorly designed jack screw that did not have a redundant system.
Any idea how many hundreds of millions of dollars this negligent death of 88 lives cost Alaska Airlines?
Let's see. 88 dead humans. Plus the anguish of their families, average of say 10 per person so that's 880 people suffering.
The loss of the aircraft, someone has to pay: $3,000,000. https://www.globalplanesearch.com/listing/aircraft-for-sale/Splash/McDonnell-Douglas-MD-80-83/241864
The cost of the recovery and multi-year investigation: Don't know, probably measured tens of millions of dollars given the typical multi-year sea-recovery costs and recreation.
The legal settlement was $300,000,000 ... https://www.nphm.com/about-us/verdi...-cases-resolved-for-0ver-300-million-dollars/
So, probably in the 1/2 BILLION dollar range when completed, and 88 dead people. But the good news is they did save 50 cents on maintenance... so there's that in the "win" category.
Hopefully that clears up my position.
You have no idea what you're talking about. None.
Apparently MrLemonade is no longer around so I'll refrain from parsing that tome and responding to any of it.That is a very creative interpretation not supported by any actual facts or the NTSB.
So, that's not my interpretation. Dozens of points to the fact the lack of jackscrew maintenance (lubrication, inspection, overhaul) was the proximate cause, lack of redundancy was a cause, and lack of maintenance policies including overhauls, signoffs, and inspections was the cause. Here's the summary:
Relevant NTSB summary findings: http://iasa.com.au/folders/Breaking_News/hotoffthepress/ntsbfindings.html
1-18: Summary - the jackscrew worn threads from inadequate lubrication caused critical loss of control.
19. The acme nut threads on the accident airplane's horizontal stabilizer jackscrew assembly wore at an excessive rate.
21. There was no effective lubrication on the acme screw and nut interface at the time of the Alaska Airlines flight 261 accident.
22. The excessive and accelerated wear of the accident jackscrew assembly acme nut threads was the result of insufficient lubrication, which was directly causal to the Alaska Airlines flight 261 accident.
23. Alaska Airlines' extension of its lubrication interval for its McDonnell Douglas MD-80 horizontal stabilizer components, and the FAA's approval of that extension, the last of which was based on Boeing's extension of the recommended lubrication interval increased the likelihood that a missed or inadequate lubrication would result in excessive wear of jackscrew assembly acme nut threads and, therefore, was a direct cause of the excessive wear and contributed to the Alaska Airlines flight 261 accident.
24. When lubricating the jackscrew assembly, removal of used grease from the acme screw before application of fresh grease will increase the effectiveness of the lubrication.
26. If the jackscrew assembly lubrication procedure was a required inspection item for which an inspector's signoff is needed, the potential for unperformed or improperly performed lubrications would be reduced.
27. Alaska Airlines' extension of the end play check interval, and FAA's approval of the extension, allowed the accident acme nut threads to wear to failure without the opportunity for detection and, therefore, was a direct cause of the excessive wear and contributed to the Alaska Airlines flight 261 accident.
29. The existing process by which manufacturers revise recommended maintenance task intervals and by which airlines establish and revise these intervals does not include task-by-task engineering analysis and justification and, therefore, allows for the possibility of inappropriate interval extensions for potentially critical maintenance tasks.
30. Because of the possibility that higher-than-expected wear could cause excessive wear in less than 2,000 flight hours and the additional possibility that an end play check could be unperformed or improperly performed, the current 2,000-flight-hour end play check interval specified in Airworthiness Directive 2000-15-15 may be inadequate to ensure the safety of the Douglas DC-9, McDonnell Douglas MD-80/90, and Boeing 717 fleet.
32. Until August 2000, Alaska Airlines used a fabricated restraining fixture that did not meet Boeing specifications; however, the Safety Board could not determine whether the use of this noncompliant fixture generated an inaccurate end play measurement during the last end play check or whether the use of this fixture contributed to the accident.
34. Deficiencies in the overhaul process increase the likelihood that jackscrew assemblies may be improperly overhauled.
35. The absence of a requirement to record or inform customers of the end play measurement of an overhauled jackscrew assembly could result in an operator unknowingly returning a jackscrew assembly to service with a higher-than-expected end play measurement.
38. The dual-thread design of the acme screw and nut does not provide redundancy with regard to wear.
39. The design of the Douglas DC-9, McDonnell Douglas MD-80/90, and Boeing 717 horizontal stabilizer jackscrew assembly did not account for the loss of the acme nut threads as a catastrophic single-point failure mode. The absence of a fail-safe mechanism to prevent the catastrophic effects of total acme nut thread loss contributed to the Alaska Airlines flight 261 accident.
40. When a failure could have catastrophic results, it is not appropriate to rely on maintenance and inspection intervention to prevent the failure from occurring if a practicable design alternative could eliminate the catastrophic effects of the failure mode. (TO BE REVISED)
41. Douglas DC-9, McDonnell Douglas MD-80/90, and Boeing 717 series airplanes, and if found necessary other transport category airplanes, should be modified to ensure that loss of the horizontal stabilizer trim system's jackscrew assembly acme nut threads or other control assembly does not preclude continued safe flight and landing.
42. Catastrophic single-point failure modes should be prohibited in the design of all future airplanes with horizontal stabilizer trim systems, regardless of whether any element of that system is considered structure rather than system or is otherwise considered exempt from certification standards for systems.
43. The certification requirements applicable to transport-category airplanes should fully consider and address the consequences of failures resulting from wear.
44. At the time of the flight 261 accident, Alaska Airlines' maintenance program had widespread systemic deficiencies.
45. The FAA did not fulfill its responsibility to properly oversee the maintenance operations at Alaska Airlines, and at the time of the Alaska Airlines flight 261 accident, Federal Aviation Administration surveillance of Alaska Airlines had been deficient for at least several years.
PROBABLE CAUSE
The National Transportation Safety Board determines that the probable cause of this accident was a loss of airplane pitch control resulting from the in-flight failure of the horizontal stabilizer trim system jackscrew assembly's acme nut threads. The thread failure was caused by excessive wear resulting from Alaska Airlines' insufficient lubrication of the jackscrew assembly.
Contributing to the accident was
(1) Alaska Airlines' extended lubrication interval, and the FAA's approval of that extension, which increased the likelihood that an unperformed or inadequate lubrication would result in excessive wear of the acme nut threads; and
(2) Alaska Airlines' extended end play check interval, and the FAA's approval of that extension, which allowed the excessive wear of the acme nut threads to progress to failure without the opportunity for detection.
(3) Contributing also to the accident was the absence on the MD-80 of a fail-safe mechanism to prevent the catastrophic effects of total acme nut thread loss.
Further citations from Wikipedia:
Alaska Airlines Flight 261 - Wikipedia
en.wikipedia.org
In NTSB board member John J. Goglia's statement for the final report, which was concurred with by the other three board members, he wrote:
Quite obviously, as I stated, this is penny-pinching foolishness gambling with planes full of humans. Every step in the chain of causation - from failing to create (or demand of Boeing) a redundant system for a critical part, to cutting maintenance on critical non-redundant parts (the whistleblower said that the jackscrew maintenance was a 4 hour job but cut by Alaska to just 1 hour), to not having overhauls or supervisor inspections, etc. is a COST CUTTING measure.
In the end, Alaska (for which I am a shareholder) unconscionably put a few dollars in front of the lives of millions of travelers and people on the ground. The few tens of thousands of dollars on the service life of these planes, doing proper engineering and service, directly killed 80+ and put in jeopardy untold numbers of others. Because they were too cheap to pull a plane for 4 hours to lubricate the poorly designed jack screw that did not have a redundant system.
Any idea how many hundreds of millions of dollars this negligent death of 88 lives cost Alaska Airlines?
Let's see. 88 dead humans. Plus the anguish of their families, average of say 10 per person so that's 880 people suffering.
The loss of the aircraft, someone has to pay: $3,000,000. https://www.globalplanesearch.com/listing/aircraft-for-sale/Splash/McDonnell-Douglas-MD-80-83/241864
The cost of the recovery and multi-year investigation: Don't know, probably measured tens of millions of dollars given the typical multi-year sea-recovery costs and recreation.
The legal settlement was $300,000,000 ... https://www.nphm.com/about-us/verdi...-cases-resolved-for-0ver-300-million-dollars/
So, probably in the 1/2 BILLION dollar range when completed, and 88 dead people. But the good news is they did save 50 cents on maintenance... so there's that in the "win" category.
Hopefully that clears up my position.
Also it was you and the RIO, and you bought signed up knowing what could happen. Now it's you, a whole crew and hundreds of passengers potentially. It's a diiferent equation altogether I'm sure.
Little do you know. I see you didn't read my thread about the ball screws. I have worked on aircraft have you?
I’ve worked in maintenance in the 121 and 135 airline industry for about 25 years. A lot of that time was with Douglas legacy products and I participated in the service bulletin validation for the revised procedure for measuring wear on the DC-9/MD-80/717 jackscrew after Alaska Airlines. So yes and I am intimately familiar with the large number of these devices on both Douglas and Boeing products. Your statement showed you have no idea what you were talking about.
Nothing but "pencil whippin the inspection. Lack of lubrication. Acme threads have been used for translation purposes for years. Nothing that difficult about lubricating a jack screw. And the Shell product was more than adequate. A grad from an aeronautical school whose name I shall not use could have done that inspection. Well, most of them.
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