So the entire control of an airplane comes down to a single nut that is stripped so that jackscrew goes up and throws the entire stabilizer out of control. I never knew the stabilizers were so critical to keeping a plane nose up or down
I researched the design of the tail section and my suspicions were correct...The horizontal stabilizer pivots (acting like an elevator) instead of being fixed. HATE THAT. A fixed stabilizer prolly doesn't produce enough deflection for this configuration but if the control (screw-jack) arm ever fails or detaches from an actual ELEVATOR, (attached to the trailing edge of a FIXED horizontal stabilizer), it tends to neutralize.....and then use trim to fly. But what do I know? I'm a plumbing contractor... REPLY
@@readmore3634 You have to understand that everything is a compromise. You could "why don't they" enough times that a plane just becomes either too costly to manufacture or too heavy to fly economically. In aviation, nearly everything is a question of "how much does it cost" or "how much does it weigh". Take any design, and it will have a service interval that, if ignored, will make it look like a dumb design. That grease gun could have a faulty grease level sensor, and since no one is regularly checking an "automatically lubricated" part, you could end up with the same result. Meanwhile, some other airline manufacturer comes along with a design that eliminates the grease gun, shaves 100,000 dollars off the price tag, and just makes "grease this part and inspect then replace when out of spec" to the service requirements. Also, the failure wasn't down to heat cause by rotational friction. The jack screw moves very slowly. There was a mechanical failure of the assembly due to excessive wear brought on by poor maintenance.
@@opmike343 Totally Agree.....I read an article where a maintenance "person" was interviewed, saying the jack-screw was hard to get to. My idea of having a sump was just (an example of) an idea. Maybe install an extension grease line with an easy-accessible Zerk fitting. I dunno, it's just how I think. As for the heat element... There was mention that in (some) airline gates the planes are subject to "higher than normal" temps due to reflection of sunlight from terminal windows....thinning/melting the grease. Also, the "constant control input" trying to "right" the airplane could have over-heated the stop at the end of the unlubricated jack-screw. (imagine the force induced with that huge stabilizer at full deflection at that speed against that stop) We've all experienced removing a stubborn nut before...if not...why be here in this comment?
@@JustRememberWhoYoureWorkingFor Agree....but use of power can sometimes control lift to some degree....full fuel tanks might get you to a dry lakebed landing..... I just don't like this design...it's unforgiving...
Never really liked the McDonnell Douglas', even prior to this accident. Speaking as someone who lives near Seattle and flies exclusively with Alaska Airlines, to their credit they got their shit together and are now one of the most highly rated airlines, and deservedly so.
I live near Seattle as well and have flown with Alaska airlines twice. Both excellent experiences. So tragic that it took the loss of 88 lives to get their executive's heads out of their asses though...😭
@Haralabos Nikolopoulos I'm no engineer, but my guess is that if there were 2, both screws must move in unison. Twice as much failure probability. If one screw were to stop moving, I imagine it would be hard to disengage the screw from the stabilizer (maybe not.) However, if one screw did fail catastrophically like this one, I imagine that spreading the load between two mechanical stops would stop or at least slow the complete failure of the horizontal stabilizer seen at the end of the video (assuming the mechanical stops were the same strength as they are in the single-screw system.) I don't know about the fairing bracket in this hypothetical system, maybe if it was stronger, it would help. This is just my analysis, I'm not an engineer. Can anybody who knows more elaborate on this?
GigaG11 it would not be very easy to have two jack screws moving in unison especially if you have a nut which is designed to wear away and be replaced as it would give different levels of wear, a simpler solution would have been to make a more robust fail safe stopping system to stop the extreme nose down position as that position gives a steady rate of decent which would allow an emergency landing rather than a sudden dive
Could the pilots have kept the stabilizer at the same angle and never stripped or destroyed the nut? I know they didnt know but moving that screw around really is what caused it to break
It jammed at cruise. Flew that way for 2:20 and the pilots were using slight pressure (10 lbs) on the yoke to keep it level. Contacted company and maintenance and they attempted an inflight troubleshoot, including reactivating the primary and secondary motors. Decided on a diversion to LAX, vs. the planned destination of SFO. The whole system failed due to inadequate maintenance, lubrication of the screw and nut, and measurements of wear, including extended periods of time between those events. Nothing they could have done differently except divert sooner, in my very humble opinion.
if they knew that mechanically, it's prone to wearing down with risk certain death, why didn't they build in a safety mechanism in case of failure? American safety standard... this is why unreliable US cars don't sell abroad.
You can only do so much honestly. If you do the proper inspections its very easily fixable. Anything you add changes a lot of things its not that simple. if it was they would do it
you dimwit read the report, the airlines didn't properly maintain the system. Has nothing to do with safety mechanism, if theyre not maintained all will fail
@@SuperBooboo02 you are right that it wasn't properly maintained by the airline, however I think the investigation also placed part of the blame on MD too
No, proper maintenance would’ve saved it. The people who made it made it to where it should’ve been inspected and re-greased every 600 flight hours, and replaced every 2000 flight hours. To save money Alaska airlines pushed the maintenance back. They were inspecting it every 2200 flight hours, and only replacing it if it needed it
redundancy was needed... a longer nut would have spread out the load and extended maint. intervals... still the staff neglected maint. -- failure was inevetable... :(
This horizontal stabilizer move up/down with the elevators at the end...meaning...if you don't have horizontal stabilizer...as soon as you pitch down you are dead
It come down to something simple. A handfull of grease every so often. These engineers act like it's fucking brain science in determining that a worm gear meshing with a disimilar metal thread needs lubed. Walmart sells a good quality lithium grease pretty cheap. Anything would have worked better than what they were useing.
@@polar3005 Most airlines do not cut corners like this. Its unfair to say most or all corporations do not care about lives lost like this. The employees, and many people working at these airlines fly these same planes. Its only a few rare airlines that would neglect maintenance to this extreme. It could just be ignorance or carelessness to follow and know the proper procedures even if it slows down operations. Airlines know this
Is NO problem with The build. The problems was with The maintnence. Alaska was cheating its service schedule.. It was noted by a mechanic that The jackscrew was weard and to be replacde but they cleard The plane out.
@@8urgerkingfoot931 of course you are right, but this way of build was a foundation for incident, you have the main tail wing section, holded by single pin as a pivot point, the cary half of the load fixing it to position, the jack screw unit is responsible to rise up or turn down the leading edge holding between two horizontal pivot points , means both connections are consatrating a high loead in to small era with no any bypass backing up system
Omg. Watching this make me sick to my stomach and sad for those lives that were lost. Rest in peace!
Me too. Sick to my stomach.
So the entire control of an airplane comes down to a single nut that is stripped so that jackscrew goes up and throws the entire stabilizer out of control. I never knew the stabilizers were so critical to keeping a plane nose up or down
It's a pretty big nut....lasts a long time if ya just grease the thing......
th-cam.com/video/bk-Dk_9mi8s/w-d-xo.html
I researched the design of the tail section and my suspicions were correct...The horizontal stabilizer pivots (acting like an elevator) instead of being fixed. HATE THAT. A fixed stabilizer prolly doesn't produce enough deflection for this configuration but if the control (screw-jack) arm ever fails or detaches from an actual ELEVATOR, (attached to the trailing edge of a FIXED horizontal stabilizer), it tends to neutralize.....and then use trim to fly. But what do I know? I'm a plumbing contractor...
REPLY
Small airplanes have their trims at the trailing edges, but for bigger airplanes that wouldn't be effective enough
@@readmore3634 You have to understand that everything is a compromise. You could "why don't they" enough times that a plane just becomes either too costly to manufacture or too heavy to fly economically.
In aviation, nearly everything is a question of "how much does it cost" or "how much does it weigh".
Take any design, and it will have a service interval that, if ignored, will make it look like a dumb design.
That grease gun could have a faulty grease level sensor, and since no one is regularly checking an "automatically lubricated" part, you could end up with the same result. Meanwhile, some other airline manufacturer comes along with a design that eliminates the grease gun, shaves 100,000 dollars off the price tag, and just makes "grease this part and inspect then replace when out of spec" to the service requirements. Also, the failure wasn't down to heat cause by rotational friction. The jack screw moves very slowly. There was a mechanical failure of the assembly due to excessive wear brought on by poor maintenance.
@@opmike343 Totally Agree.....I read an article where a maintenance "person" was interviewed, saying the jack-screw was hard to get to. My idea of having a sump was just (an example of) an idea. Maybe install an extension grease line with an easy-accessible Zerk fitting. I dunno, it's just how I think. As for the heat element... There was mention that in (some) airline gates the planes are subject to "higher than normal" temps due to reflection of sunlight from terminal windows....thinning/melting the grease. Also, the "constant control input" trying to "right" the airplane could have over-heated the stop at the end of the unlubricated jack-screw. (imagine the force induced with that huge stabilizer at full deflection at that speed against that stop) We've all experienced removing a stubborn nut before...if not...why be here in this comment?
@@JustRememberWhoYoureWorkingFor Agree....but use of power can sometimes control lift to some degree....full fuel tanks might get you to a dry lakebed landing..... I just don't like this design...it's unforgiving...
Never really liked the McDonnell Douglas', even prior to this accident.
Speaking as someone who lives near Seattle and flies exclusively with Alaska Airlines, to their credit they got their shit together and are now one of the most highly rated airlines, and deservedly so.
I live near Seattle as well and have flown with Alaska airlines twice. Both excellent experiences. So tragic that it took the loss of 88 lives to get their executive's heads out of their asses though...😭
Why didn’t they designed the jack screw system with a hardened nut too?
Because the nut being made from a soft material ensures that this is the part that will wear out first
The nut is intentionally designed to wear more than the screw, since the nut is easier to replace.
@Haralabos Nikolopoulos
I'm no engineer, but my guess is that if there were 2, both screws must move in unison. Twice as much failure probability. If one screw were to stop moving, I imagine it would be hard to disengage the screw from the stabilizer (maybe not.) However, if one screw did fail catastrophically like this one, I imagine that spreading the load between two mechanical stops would stop or at least slow the complete failure of the horizontal stabilizer seen at the end of the video (assuming the mechanical stops were the same strength as they are in the single-screw system.) I don't know about the fairing bracket in this hypothetical system, maybe if it was stronger, it would help. This is just my analysis, I'm not an engineer. Can anybody who knows more elaborate on this?
GigaG11 it would not be very easy to have two jack screws moving in unison especially if you have a nut which is designed to wear away and be replaced as it would give different levels of wear, a simpler solution would have been to make a more robust fail safe stopping system to stop the extreme nose down position as that position gives a steady rate of decent which would allow an emergency landing rather than a sudden dive
Could the pilots have kept the stabilizer at the same angle and never stripped or destroyed the nut? I know they didnt know but moving that screw around really is what caused it to break
Apperantly it had gotten Jammed during the climb up. They had to level out at some point.
It jammed at cruise. Flew that way for 2:20 and the pilots were using slight pressure (10 lbs) on the yoke to keep it level. Contacted company and maintenance and they attempted an inflight troubleshoot, including reactivating the primary and secondary motors. Decided on a diversion to LAX, vs. the planned destination of SFO. The whole system failed due to inadequate maintenance, lubrication of the screw and nut, and measurements of wear, including extended periods of time between those events. Nothing they could have done differently except divert sooner, in my very humble opinion.
if they knew that mechanically, it's prone to wearing down with risk certain death, why didn't they build in a safety mechanism in case of failure? American safety standard... this is why unreliable US cars don't sell abroad.
@@vaporizers101 so money>life
You can only do so much honestly. If you do the proper inspections its very easily fixable. Anything you add changes a lot of things its not that simple. if it was they would do it
you dimwit read the report, the airlines didn't properly maintain the system. Has nothing to do with safety mechanism, if theyre not maintained all will fail
@@SuperBooboo02 you are right that it wasn't properly maintained by the airline, however I think the investigation also placed part of the blame on MD too
@@itseveryday8600 the reason why American cars aren't sold abroad is not reliability but size and fuel consumption
A different material choice in the Acme Nut could've prevented Alaska 261 from crashing.
The acme nut is made from a soft material on purpose so that's the part that's gonna wear out first
No, proper maintenance would’ve saved it. The people who made it made it to where it should’ve been inspected and re-greased every 600 flight hours, and replaced every 2000 flight hours. To save money Alaska airlines pushed the maintenance back. They were inspecting it every 2200 flight hours, and only replacing it if it needed it
redundancy was needed... a longer nut would have spread out the load and extended maint. intervals... still the staff neglected maint. -- failure was inevetable... :(
It's a pretty big nut....lasts a long time if ya just grease the thing......
th-cam.com/video/bk-Dk_9mi8s/w-d-xo.html
Why couldnt airforce come in and shoot the stabilizer free with precision cannon work ...I am SERIOUS! Would that have worked? Maybe?
Dougie Quick lol nice joke
This horizontal stabilizer move up/down with the elevators at the end...meaning...if you don't have horizontal stabilizer...as soon as you pitch down you are dead
It's a good vid for kids
I’m no aircraft expert but your diagram shows the elevator in an upward pitch . This would pitch the nose up not down .
It flies the tail up, which in turn pitches the nose down.
BTW they stole the idea for the jack screw from hospital beds and garage door openers
Grease the jackscrew.
Why weren’t these maintenance workers in jail? They did such a lazy shameful careless job 😡😡😡😡😡 look how many lives they cost 😥😥😥😥😥😥
facebook LARICCIA NELSON find links shared law and orther NTSB n FF/TOW at LGA find out of it past months charters air fco ...SN BRU other
It come down to something simple. A handfull of grease every so often. These engineers act like it's fucking brain science in determining that a worm gear meshing with a disimilar metal thread needs lubed. Walmart sells a good quality lithium grease pretty cheap.
Anything would have worked better than what they were useing.
6gu7 yep lol the literally used nothing. Just one small corner to cut to them had so many people killed. It's sad corporations do this
@@polar3005 Most airlines do not cut corners like this. Its unfair to say most or all corporations do not care about lives lost like this. The employees, and many people working at these airlines fly these same planes. Its only a few rare airlines that would neglect maintenance to this extreme.
It could just be ignorance or carelessness to follow and know the proper procedures even if it slows down operations. Airlines know this
That method of building an airplane must be forbidden...
Is NO problem with The build. The problems was with The maintnence. Alaska was cheating its service schedule.. It was noted by a mechanic that The jackscrew was weard and to be replacde but they cleard The plane out.
@@8urgerkingfoot931 of course you are right, but this way of build was a foundation for incident, you have the main tail wing section, holded by single pin as a pivot point, the cary half of the load fixing it to position, the jack screw unit is responsible to rise up or turn down the leading edge holding between two horizontal pivot points , means both connections are consatrating a high loead in to small era with no any bypass backing up system