Alaska Airlines 737-900 MAX loses a door in-flight out of PDX
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I was also trying to find out about the wiring. If it were a door, there would be sensors with corresponding wiring to send a message to the cockpit if there was any issue like all the other doors. I understand the airframe arrives from Spirit as an empty shell and Boeing install all wiring. In the case of a plug, would Boeing a) install these sensors anyway and just not connect them b) just install the wiring in case the sensors are added later or c) there is no door wiring at all and it would all be added at time of conversion from plug to door should it happen? In the case of c) which I believe is the correct option, I guess there is no particular reason for Boeing to look at the hardware of the plug in any way, but if a) or b) then I guess Boeing are 100% taking the thing in and out.
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It appears to me that the installation of the vertical movement arresting bolt will create interference with the roller pin and guide track if the tolerances of the door assembly are not controlled or adjusted in some other way. Could a tight fit of the door have fractured the guide track?
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It appears to me that the installation of the vertical movement arresting bolt will create interference with the roller pin and guide track if the tolerances of the door assembly are not controlled or adjusted in some other way. Could a tight fit of the door have fractured the guide track?
This could be why the bolts were left loose. There was meant to be a final adjustment of the door at some point before entering service.
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While I have no specific or direct knowledge of these aircraft, and don't fly or work on them, I can restate what was stated earlier in this thread regarding the wiring... The question on sensors was asked a ways back, answer was that the plane was wired for door sensors, annunciator lights are in the cockpit, but are placarded inop and there are no active electrical connections when plug door is installed. That answer is somewhere further up this thread - I'm simply restating it.
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I feel like still much to unpack in this case. Theres a distinct lack of photo detail involving the lower guide fittings and their designed attachment. Are the 4 bolts installed into nutplates? I cant verify from the photos Ive seen. If so, I would say that is improper for this application. I would expect a tension bolt and locknut but anyway. Also in the example showing loose hardware, it looks to me that these same bolts are not proper diameter. These guide blocks should be precisely located with no adjust. Were nutplates too small? Just how it appears with these minimal details. I think installers would likely loosen these blocks to make easier alignment onto both shafts simultaneously, then retorque .
In any case, the 2 upper lock bolts must have been missing. I cant make the plug depart its position if those are installed. The 12 outward stops cannot be overcome unless the lock bolts are gone.
Also, it appears that in the first gate photos of the exterior opening that the aft lower shaft is dangling with something else attached, but not present in later NTSB photos with plastic curtain.
In any case, the 2 upper lock bolts must have been missing. I cant make the plug depart its position if those are installed. The 12 outward stops cannot be overcome unless the lock bolts are gone.
Also, it appears that in the first gate photos of the exterior opening that the aft lower shaft is dangling with something else attached, but not present in later NTSB photos with plastic curtain.
Question: what does Boeing gain by intentionally being reckless? Saving 0.7 man hours per plane? Great, the financials are looking better. The company is saved.
But seriously, if not employee error (which to me is gross negligence and possibly a federal offense, what does the company as an entity have to gain
But seriously, if not employee error (which to me is gross negligence and possibly a federal offense, what does the company as an entity have to gain
There is an old saying, If you think that quality is expensive try an accident.
On a longer time scale those accountant games destroy a company. For the accountant the trick is to move to another position or company faster, than he is hold responsible.
For pilots such a behavior does not work out, as mother nature holds them accountable within the next hours of their decision making. So this group here might have more difficulty to understand those decision processes.
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Since several planes are affected, and since different bolts are loose/missing, this must be a procedural problem. It was not an individual who forgot to torque a bolt. The hinge brackets have slotted holes for adjustment, the 12 door stops all need adjustment in a certain order. This adjustment procedure has methodically failed to be completed. There is a problem in the process, most likely at Boeing before the pressurization test.
Therefore the entire assembly process needs to be reviewed and fixed, not only for that door. And not limited to the -9 type. Remember the loose bolt in the rudder system concerning all variants?
https://www.reuters.com/business/aer...ed-2024-01-09/
Therefore the entire assembly process needs to be reviewed and fixed, not only for that door. And not limited to the -9 type. Remember the loose bolt in the rudder system concerning all variants?
https://www.reuters.com/business/aer...ed-2024-01-09/
Last edited by spornrad; 10th Jan 2024 at 06:49.
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One of the hinge brackets is still on the plane, the other is missing. In an earlier photo it wasn't clear but the newest photo shows that the bracket is absent on both sides on the door. For this reason, the NTSB asked in the press conference to look out for a green thing.
Given 2: The forward Hinge Guide Fitting is missing, it is not attached to the hinge protruding from the airplane nor is it attached to the door plug. It separated from both.
Question: How could this possibly be? What events could lead to the forward Hinge Guide Fitting having separated from both the door plug and the hinge?
-As scifi notes above, the Hinge Guide Fitting can be considered part of the plug, secured by 4 bolts to locking nut plates.
-The forward Hinge Guide Fitting must have been attached securely enough to the door plug for it to be yanked violently enough to shear the Vertical Movement Arrestor Bolt (if it was present), AND violently enough to be pulled over the top retaining washer and 2 hex nuts as noted by dragon6172
-Yet it was not found attached to the door plug in Bob's yard after its peaceful fall from the sky
Theory: The Hinge Guide Fitting must have detached from the plug before it left the plane, or as it left the plane. Maybe it was never attached, other than to the hinge cylinder.
It is possible the door plug interior base snagged it and ripped it past the top retaining washer and nuts? The spring looks like its missing as well. The aft Hinge Guide Fitting may have "gotten lucky" that it was not snagged in a similar way. Maybe there are witness marks.
Therefore, first event must have been separation from door plug (if it was ever attached). Second event must have been separation from hinge cylinder. The Hinge Guide Fitting could not have separated from the door plug during the fall if it was mounted securely enough to by ripped from the hinge.
(Although I do wonder if after all that chit chat at Bobs house the NTSB was smart enough to carefully search the landing point under the door plug in Bob's yard with a metal detector for bolts/remnants or other items that may have dislodged from the door plug when it impacted the trees/ground...)
Forward Hinge Cylinder with missing Hinge Guide Fitting and Spring
Base of door plug
Last edited by lateott; 10th Jan 2024 at 06:45. Reason: Typo
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I think the lower hinge guide is adjustable. It looks as though the holes on the hinge guide are slotted. This allows for adjustment to even the gap between the door and fuselage skin.
This could be why the bolts were left loose. There was meant to be a final adjustment of the door at some point before entering service.
This could be why the bolts were left loose. There was meant to be a final adjustment of the door at some point before entering service.
I just noticed something else on that photo that I have looked at 100 times. Look at the wear marks on the black cylinder where it meets the upper part of the Hinge Guide Fitting. That thing was moving around.
Last edited by lateott; 10th Jan 2024 at 06:46. Reason: Typo
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Since several planes are affected, and since different bolts are loose/missing, this must be a procedural problem. It was not an individual who forgot to torque a bolt. The hinge brackets have slotted holes for adjustment, the 12 door stops all need adjustment in a certain order. This adjustment procedure has methodically failed to be completed. There is a problem in the process, most likely at Boeing before the pressurization test.
Therefore the entire assembly process needs to be reviewed and fixed, not only for that door. And not limited to the -9 type. Remember the loose bolt in the rudder system concerning all variants?
Therefore the entire assembly process needs to be reviewed and fixed, not only for that door. And not limited to the -9 type. Remember the loose bolt in the rudder system concerning all variants?
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One of my university tutors worked on the Comet 4 and Trident. As a young engineer he discovered how de Havilland were torquing Comet wing attachment bolts. These could not be reached with a torque wrench that could apply torque directly on the bolt axis. Instead they attached one end of an open ended spanner to the torque wrench with the other end engaging the head of the blind bolt.
It was fairly easy to show that depending on how you held the torque wrench/spanner combination you could get wildly different applied torques to the bolt. Even no torque at all. This discovery caused a certain amount of consternation in de Havilland production.
Another technique I have seen (from Deutz diesel cylinder head bolts if I remember) is to torque the bolts to a certain (small) torque then apply a certain number of turns. That probably makes it easier to line up locking fittings.
(SLF engineer)
It was fairly easy to show that depending on how you held the torque wrench/spanner combination you could get wildly different applied torques to the bolt. Even no torque at all. This discovery caused a certain amount of consternation in de Havilland production.
Another technique I have seen (from Deutz diesel cylinder head bolts if I remember) is to torque the bolts to a certain (small) torque then apply a certain number of turns. That probably makes it easier to line up locking fittings.
(SLF engineer)
The Torque plus angle you refer to is normally used to provide a controlled pre-stretch of a fastner.. Othen used on fastners subjected to high cyclic loads to impove fatique resistance.
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Shoddy workmanship by cheaper less trained workforce.
There is an old saying, If you think that quality is expensive try an accident.
On a longer time scale those accountant games destroy a company. For the accountant the trick is to move to another position or company faster, than he is hold responsible.
For pilots such a behavior does not work out, as mother nature holds them accountable within the next hours of their decision making. So this group here might have more difficulty to understand those decision processes.
There is an old saying, If you think that quality is expensive try an accident.
On a longer time scale those accountant games destroy a company. For the accountant the trick is to move to another position or company faster, than he is hold responsible.
For pilots such a behavior does not work out, as mother nature holds them accountable within the next hours of their decision making. So this group here might have more difficulty to understand those decision processes.
Further My post re: the washer/stop on the forward guide, though at first I thought it simply looked like a smaller washer than was correct I now consider it may be the proper item but deformed (cupped upwards) thus appearing smaller diameter when viewed top-down, coupled with the fact that the guide hole in the hinge fitting on the plug/door is fitted with what looks like a nylon bush then its feasible that the whole hinge-guide assembly simply got torn off the end of the guide shaft
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Given 1: The aft Hinge Guide Fitting (or “collar” or “bracket” or "green thing") remained attached to the aft hinge protruding from the doorway of the plane.
Given 2: The forward Hinge Guide Fitting is missing, it is not attached to the hinge protruding from the airplane nor is it attached to the door plug. It separated from both.
Question: How could this possibly be? What events could lead to the forward Hinge Guide Fitting having separated from both the door plug and the hinge?
Given 2: The forward Hinge Guide Fitting is missing, it is not attached to the hinge protruding from the airplane nor is it attached to the door plug. It separated from both.
Question: How could this possibly be? What events could lead to the forward Hinge Guide Fitting having separated from both the door plug and the hinge?
Interesting observation. It is hard to believe the retaining bolt would have allowed that degree of movement though.
https://www.forbes.com/sites/jeremyb...h=741379fd1d7a
Psychophysiological entity
The indication of sliding movement on that black tubular hinge fitting maybe left from the nylon type material, but I think it's reflection. Not sure
I flatly discounted the elongated holes at first, now I'm fairly sure they are - but they're also very wide! Then they've got a small washer which would have be compressed onto a partial void under the head of the bolt. What is going on with design like this? You can't have floppy slots to make adjustments on aircraft, or maybe the world has changed.
I flatly discounted the elongated holes at first, now I'm fairly sure they are - but they're also very wide! Then they've got a small washer which would have be compressed onto a partial void under the head of the bolt. What is going on with design like this? You can't have floppy slots to make adjustments on aircraft, or maybe the world has changed.
Signs of QA improvement
From the Reuters article referenced above:
That's better than selling off an under-performing part of the company in the expectation of improvement. But does 'sending written orders' address the seriousness of this issue? Can Boeing not afford the expense of sending people to ensure the orders are fully understood and complied with? Permanently assigned QA staff would be even better.
'QUALITY CONTROL ISSUE'
In a separate meeting on Tuesday, Boeing told staff the findings were being treated as a "quality control issue" and checks were under way at Boeing and fuselage supplier Spirit Aerosystems (SPR.N), sources familiar with the matter said.
Boeing has sent written orders to its own plants and those of its suppliers to ensure such problems are addressed and to carry out broader checks of systems and processes, they said.
In a separate meeting on Tuesday, Boeing told staff the findings were being treated as a "quality control issue" and checks were under way at Boeing and fuselage supplier Spirit Aerosystems (SPR.N), sources familiar with the matter said.
Boeing has sent written orders to its own plants and those of its suppliers to ensure such problems are addressed and to carry out broader checks of systems and processes, they said.
From the Reuters article referenced above:
That's better than selling off an under-performing part of the company in the expectation of improvement. But does 'sending written orders' address the seriousness of this issue? Can Boeing not afford the expense of sending people to ensure the orders are fully understood and complied with? Permanently assigned QA staff would be even better.
That's better than selling off an under-performing part of the company in the expectation of improvement. But does 'sending written orders' address the seriousness of this issue? Can Boeing not afford the expense of sending people to ensure the orders are fully understood and complied with? Permanently assigned QA staff would be even better.