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Alaska Airlines 737-900 MAX loses a door in-flight out of PDX

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Alaska Airlines 737-900 MAX loses a door in-flight out of PDX

Old 7th Jan 2024, 12:19
  #241 (permalink)  
 
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Originally Posted by DogTailRed2
On the failure door and the one above why is the edge trim missing? Is that normal when deploying the escape hatch? To an untrained eye to see the packing in the fuselage looks weird.
Its not an escape hatch; its a non-functioning plug-door. The trim in this photo has been removed for access/inspection/photography. That's what the inside of a fuselage looks like when the trim has been removed.
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Old 7th Jan 2024, 12:46
  #242 (permalink)  
 
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Originally Posted by MechEngr
After the Lion Air crash there was zero heat on Boeing. It was only after false statements immediately after the ET-302 crash, that the pilots doing the exact in-sequence operations given in the Emergency AD and the FCOM update, that the crap hit the fan. The plane was painted as uncontrollable, but that was far from the truth. By the time the actual actions taken by the ET-302 came out more than a year later the PR damage to Boeing had been done. Had Airbus been subjected to the same flack over knowingly not grounding all their planes when the pitot de-icing issue connected to AF447 was found, an issue they had a fix for prior to the crash that they didn't install, then there would be some equal footing. In both cases a situational sensor failed and the crews mishandled the aircraft because the software was inadequate to stop them from doing so.
There is a huge difference between a sensor temporarily failing with the pilot making completely unwarranted inputs commanding the plane into a stall, versus a system that actively and repeatedly degraded the plane's flight characteristics because of a failed sensor.

In the first case, the pilots needed to do almost nothing and the problem would correct itself. Just "don't do anything stupid". In the second the pilots needed to take immediate action to maintain controllability.

These issues are nowhere near being equal in severity.
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Old 7th Jan 2024, 13:25
  #243 (permalink)  
 
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Originally Posted by fenland787
I agree, zooming in on the higher res image of the failed door/plug in post #194 (it's still very hard to be sure I'm not just seeing artefacts in the image) but it almost looks like the visible end of the pin is showing an axial counterbore hole and an uneven surface at about the point that cross bolt would have been?
However if that were the issue then a quick visual inspection of the pins would not find it and the inspection of the other aircraft would surely take longer than it seems to......
Looks very much as though this and flipfrog’s earlier post are correct. The roller pins in the fuselage frame clearly do engage in the door guide tracks although maybe not as far as you might expect given the available depth of the fitting) BUT the engagement of the lock bolt which stops the plug lifting up the track with the roller pin looks marginal.

Given this event had a direct (not root) cause of a mechanical engagement fault I’d have to say I’m surprised at the woolly terms of the AD. Surely we should expect specific dimensions to be checked and recorded. Against a Boeing specification? - perhaps there wasn’t one.

Last edited by Europa01; 7th Jan 2024 at 18:55. Reason: Correction of component terminology - thanks Chris Brady
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Old 7th Jan 2024, 13:28
  #244 (permalink)  
 
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Originally Posted by AirScotia
It also seems odd to me that two seats next to the relevant window were apparently empty, two of only seven unoccupied seats in a full flight - including a window seat at that.
It's normally just a trivia - though of relevance here - that USA passengers, have a strangely different perspective to Europe, and go on about getting an Aisle Seat. Noticeable on carriers with free seating like Southwest that those first in take aisle seats, whereas comparably on Ryanair they more commonly take window seats first. It leads to considerable inefficiencies in boarding as the aircraft fills up and there needs to be making way for others to pass by, sometimes with reluctance, Given these incident seats are at the rear, they are the ones, fortunately, likely to go unused where the aircraft is not full.
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Old 7th Jan 2024, 13:34
  #245 (permalink)  
 
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Originally Posted by aeromech3
I imagined these were just lanyards much like ceiling panels and others have to facilitate opening without uncontrolled dropping, the adjacent structure does not looked beefed up for a pip pin type lock, but I stand to be corrected!
Yes, that's correct. They support the plug in the partially open position as seen here in the video posted by MechEngr-
Originally Posted by MechEngr
Informative video:

Indicates a non-functional door was used rather than in-oping an exit door and suggest retaining bolts were missing. If so, then there will be a paper trail back to whoever signed off that the bolts were installed.
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Old 7th Jan 2024, 14:37
  #246 (permalink)  
 
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So how are those bolts installed then?
Tool/Screw inserted through the plug fitting and fastened in the axial bore of the bolt, then pulled in place and secured with a safety pin?
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Old 7th Jan 2024, 15:11
  #247 (permalink)  
 
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Originally Posted by C2H5OH
So how are those bolts installed then?
Tool/Screw inserted through the plug fitting and fastened in the axial bore of the bolt, then pulled in place and secured with a safety pin?
The (intended) location of the 4 retaining bolts is explained in the annotated photos at 2:27 and 24:26 of the video linked in my post above

Last edited by Saab Dastard; 7th Jan 2024 at 16:52.
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Old 7th Jan 2024, 15:13
  #248 (permalink)  
 
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Yes I agree this video is excellent and seems to be definitive about how the Plug works. (And only the Plug has a full-size window in it. Doors have small circular Portholes).

There is 3-4 minutes right at the end about the Alaska Airlines incident.

In the absence of any visible frame distortion or tearing, I would deduce that all 4 securing bolts must have been U/S or missing, so the door could slide upwards 4" under the fitted bottom springs pressure, become completely clear of the retaining devices, and be fired out into space by cabin pressure. But how that could come about I do not have a theory.

IB
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Old 7th Jan 2024, 15:23
  #249 (permalink)  
 
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According to Reuters, the last body to amend the door would be Boeing themselves.

Spirit made blowout part but Boeing has key role


As part of the production process, Spirit builds fuselages for 737s and sends them by train with the special door assembly “semi-rigged,” one of the people said. “They are fitted but not completed," the person said.

At its Renton, Washington, plant, Boeing typically removes the pop-out, or non-functioning, door and uses the gap to load interiors. Then, the part is put back and the installation in completed. Finally, the hull is pressurized to 150% to make sure everything is working correctly, the person said.
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Old 7th Jan 2024, 15:30
  #250 (permalink)  
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They appear to have very quickly known the cause of this incident without even finding the missing door/plug. Would photos have been taken of the plug during production or later maintenance? I would presume the only thing you could tell from a photo is if the (upper) securing bolts/pins were missing? Damage or the wrong type/length would not be obvious.
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Old 7th Jan 2024, 15:35
  #251 (permalink)  
 
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Originally Posted by EXDAC
The (intended) location of the 4 retaining bolts is explained in the annotated photos at 2:27 and 24:26 of the video linked in my post 248.
My question was related to how they get into these postions.
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Old 7th Jan 2024, 15:44
  #252 (permalink)  
 
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Originally Posted by C2H5OH
My question was related to how they get into these postions.
I have not seen any detail of the lower hinge locking bolts. It appears to me that the guide fitting is locked by a headless socket cap screw and a jam nut. (Just speculation though as the photo resolution is not good enough to be sure)

Edit - later information shows this is a through bolt with castellated nut and cotter pin.

Last edited by EXDAC; 7th Jan 2024 at 18:27.
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Old 7th Jan 2024, 15:54
  #253 (permalink)  
 
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Not sure I agree with this statement:
At its Renton, Washington, plant, Boeing typically removes the pop-out, or non-functioning, door and uses the gap to load interiors. Then, the part is put back and the installation in completed.
Again, no first hand knowledge of how they do things in Renton on the 737 line, but in Everett, Emergency Exit doors are rarely used to load interior components for the simple reason that they are smaller than the main entry/exit doors. Since loading interior components is largely done manually, they want as much room as possible. While this is done both through the front and rear main doors, I've never heard of that being through an over-wing exit door.
Function E-E doors are often opened to provide ventilation, etc., both in the factory and out on the flight line (with safety straps applied across the opening to discourage people from falling out), but I seriously doubt that is ever done with a non-function exit 'plug'.
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Old 7th Jan 2024, 15:56
  #254 (permalink)  
 
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Originally Posted by Ivor_Bigunn
In the absence of any visible frame distortion or tearing, I would deduce that all 4 securing bolts must have been U/S or missing, so the door could slide upwards 4" under the fitted bottom springs pressure, become completely clear of the retaining devices, and be fired out into space by cabin pressure. But how that could come about I do not have a theory.
What function do those springs have when a plug door is fitted?

It's clear what role they perform when a live door is being opened, but do we know they are even present when the aircraft has the plug door (which is only ever going to be opened on a check)?
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Old 7th Jan 2024, 16:03
  #255 (permalink)  
 
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Quote:-
with the special door assembly “semi-rigged,” one of the people said.
“They are fitted but not completed," the person said.
Oops, been there, done that!
But it could never happen on an aeroplane?
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Old 7th Jan 2024, 16:06
  #256 (permalink)  
 
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As part of the production process, Spirit builds fuselages for 737s and sends them by train with the special door assembly “semi-rigged,” one of the people said.
Advertisement · Scroll to continue

Report this ad“They are fitted but not completed," the person said.

At its Renton, Washington, plant, Boeing typically removes the pop-out, or non-functioning, door and uses the gap to load interiors. Then, the part is put back and the installation in completed. Finally, the hull is pressurized to 150% to make sure everything is working correctly, the person said.

The process means that finding out where any flaw was introduced during assembly may not be clear-cut, said the sources, who asked not to be named as details of the probe are confidential.

Door plugs have been used to adapt aircraft and offer flexible layouts across the industry for years.

The investigation will include structural experts to see whether design or manufacturing played a role in the accident.

"The assumption is that it was installed or rigged incorrectly,” one of the sources said.

Boeing and Spirit declined comment on industrial processes.

Reporting by Valerie Insinna, Tim Hepher and David Shepardson Editing by Chris Reese and Leslie Adler https://www.reuters.com/business/aer...es-2024-01-07/
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Old 7th Jan 2024, 16:07
  #257 (permalink)  
 
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Originally Posted by EXDAC
I have not seen any detail of the lower hinge locking bolts. It appears to me that the guide fitting is locked by a headless socket cap screw and a jam nut. (Just speculation though as the photo resolution is not good enough to be sure)
Are you thinking that there is a bolt that goes through the plug door and into a tapped hole on the fuselage pin? It also looks like there could be a bolt that runs coincident to the outer door the secures the pin from moving upward that seems to be installed?
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Old 7th Jan 2024, 16:13
  #258 (permalink)  
 
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Originally Posted by Thruster763
It is a picture of a door guide and striker plates. The point of my post is the parts ringed in blue in the image by heliwrench and "pins" in pictures of incident fuselage frame (silver coloured) are NOT the locking pins or bolts, they are the door / plug guides on door / plug and guide pins on frame.

EDIT,
Just looked again and it appears that the guide pin and lock pin are combined on the mid emergency exit door. So the bolts do go intor the center of the guide pins. Sorry for the confusion.
I was second guessing myself and was correct the first time.This image of a DOOR shows the locking pins below the upper two striker plates which have the guide pin between them.


But it does look like the PLUG has bolts in a different location, possibly going into the guide pin.
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Old 7th Jan 2024, 16:14
  #259 (permalink)  
 
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I did post earlier today to ponder whether there was any relevance to the 707C Hat rack door design of 1963?
The door is very similar to the 737 doors fitted now so just asking could anyone care to add anything or are in the know.
as we all know Boeing have used many grandfather rights in getting the 737 Max to where it is today.
Thanks
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Old 7th Jan 2024, 16:23
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Originally Posted by DaveReidUK
What function do those springs have when a plug door is fitted?

It's clear what role they perform when a live door is being opened, but do we know they are even present when the aircraft has the plug door (which is only ever going to be opened on a check)?
I expect they are to lift the door to disengage the fingers. If the door was unable to move up then the fingers cannot release.

The question is, are the bolts at the springs situated in circular holes or in slots? If they are in slots to limit the travel of the door to just enough to clear the fingers that would make sense. It would ease the process of reinstalling the the door to the closed position. From the latest chrisbrady b737.org.uk video there is a stop cap on the top of the guide that the springs are installed on. Since the guides appear to have remained with the plane and not been bent or twisted, but the caps didn't stay, how did that happen?

It seems more like the caps, the lower locking bolts, and the upper locking bolts were never installed before delivery and who knows what was holding the door from popping up and out. Someone put the door in on the springs and then shut it. Maybe they tightened the adjusters for the fingers enough to hold it in place with friction.

I am leaning toward the door having opened during the taxi or early after takeoff and the plastic interior panel plugging the leak until it could no longer be supported by the cable straps. Then the door was ejected by the lift springs and the interior panel was adios muchacho. It would not have moved if pressure was applied before it opened as that would have damaged the fingers around the frame.
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