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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, 20:09
  #281 (permalink)  
 
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Agreed. I don't see how the door can slide upwards unless the upper bolts were missing, OR, if there's a tolerance issue with the amount of roller engaging in the slot. What if the edge of the bolt wasn't enough to hold the roller in place? Could be because incorrect diameter bolt was used, or width of frame was larger than expected / designed. Once they find the door they will know (obviously) whether the bolts are there (or not) and if they are of the correct size.

Last edited by RLB1; 8th Jan 2024 at 01:36.
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Old 7th Jan 2024, 20:17
  #282 (permalink)  
 
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Originally Posted by DaveReidUK
I note that all 4 bolts are retained by castle nuts and cotter pins (more usually known as split pins).
Split pins in UK, cotter pins in USA. MS24665 is titled "PIN, COTTER (SPLIT)".
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Old 7th Jan 2024, 20:21
  #283 (permalink)  
 
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I have read all 282 posts. I'm going for option c) "omitting the bolts"

If that is the case, either Boeing and Spirit will blame each other as to who is responsible for sending the aircraft to the customer. Or they will both learn from this.
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Old 7th Jan 2024, 20:30
  #284 (permalink)  
 
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Originally Posted by mikeygd
I have read all 282 posts. I'm going for option c) "omitting the bolts"
That struck me as the least likely. If they had been omitted during manufacture, by either Spirit or Boeing, I'm wondering what would have kept the door plug from opening on nearly 150 previous flights.
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Old 7th Jan 2024, 20:33
  #285 (permalink)  
 
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Originally Posted by mikeygd
I have read all 282 posts. I'm going for option c) "omitting the bolts"
That's my feeling too but what would stop the door lifting up and falling outboard when the aircraft was unpressurized on the ground. Is the plug lighter or heavier that the door? Are the lift springs strong enough to raise the door/plug against any friction from the stop pads, guides, and presumably some from the seal, or are they designed to just assist the lift?

Would a routine external inspection have shown if the plug had moved from the fully closed position but not yet released from the guides?
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Old 7th Jan 2024, 20:36
  #286 (permalink)  
 
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Originally Posted by DaveReidUK
What photo are you looking at that shows four sheared bolts?
If I could post photos I would, but look at the post immediately below yours and compare with the photos upthread of correctly-fitted plugs _and_ doors. In both cases the frame of the door or plug is secured to the aircraft with what appear to be twelve bolts/large screws installed from the inside. These match with fairly sturdy protrusions from the fuselage and (to the untrained eye) are pretty hefty mechanisms for holding the plug (or the door frame) in place. (To be clear, look at spornrad's picture -- the things at the top and bottom)

In the picture of the accident aircraft, you can see the four top protrusions from the fuselage (they're pretty obvious) and they appear to have metal in them where the bolts would be. But the frame is completely absent, along with the first parts of those screws/bolts, leaving the rest attached to the fuselage.

It's entirely possible I'm missing something, please (and I'm serious) tell me why I'm wrong.
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Old 7th Jan 2024, 20:37
  #287 (permalink)  
 
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Originally Posted by mikeygd
I have read all 282 posts. I'm going for option c) "omitting the bolts"

If that is the case, either Boeing and Spirit will blame each other as to who is responsible for sending the aircraft to the customer. Or they will both learn from this.
I know I would never have gotten away with claiming that I wasn't responsible for some screwup because a subcontractor or supplier was the guilty party. I don't think Boeing will in this case, either, especially because, as my Brit friends say, they have previous.

And if it is true that the plug was removed and reinstalled during final assembly at Renton, even trying to shift responsibility would be pointless.
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Old 7th Jan 2024, 20:40
  #288 (permalink)  
 
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IF there are no springs in the plug config, AND no bolts, the plug would always tend to drop back to datum between flights.
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Old 7th Jan 2024, 20:42
  #289 (permalink)  
 
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Originally Posted by ThreeIfByAir
If I could post photos I would, but look at the post immediately below yours and compare with the photos upthread of correctly-fitted plugs _and_ doors. In both cases the frame of the door or plug is secured to the aircraft with what appear to be twelve bolts/large screws installed from the inside. These match with fairly sturdy protrusions from the fuselage and (to the untrained eye) are pretty hefty mechanisms for holding the plug (or the door frame) in place.

In the picture of the accident aircraft, you can see the four top protrusions from the fuselage (they're pretty obvious) and they appear to have metal in them where the bolts would be. But the frame is completely absent, along with the first parts of those screws/bolts, leaving the rest attached to the fuselage.

It's entirely possible I'm missing something, please (and I'm serious) tell me why I'm wrong.
Those "twelve sturdy protrusions" are the stops that prevent the door being blown out of the aircraft.

If they were bolts through them, nobody would have to worry about the door opening, ever.

I'm pretty sure that's been covered before, more than once.
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Old 7th Jan 2024, 20:44
  #290 (permalink)  
 
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Originally Posted by ThreeIfByAir
If I could post photos I would, but look at the post immediately below yours and compare with the photos upthread of correctly-fitted plugs _and_ doors. In both cases the frame of the door or plug is secured to the aircraft with what appear to be twelve bolts/large screws installed from the inside. These match with fairly sturdy protrusions from the fuselage and (to the untrained eye) are pretty hefty mechanisms for holding the plug (or the door frame) in place. (To be clear, look at spornrad's picture -- the things at the top and bottom)

In the picture of the accident aircraft, you can see the four top protrusions from the fuselage (they're pretty obvious) and they appear to have metal in them where the bolts would be. But the frame is completely absent, along with the first parts of those screws/bolts, leaving the rest attached to the fuselage.

It's entirely possible I'm missing something, please (and I'm serious) tell me why I'm wrong.
Yes, you have it a bit wrong. There are not 12 bolts there, they are just contact pads for the stops. There is nothing that appears to be sheared or missing with the stops.
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Old 7th Jan 2024, 20:46
  #291 (permalink)  
 
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Originally Posted by DaveReidUK
Those "twelve sturdy protrusions" are the stops that prevent the door being blown out of the aircraft.

If they were bolts through them, nobody would have to worry about the door opening, ever.

I'm pretty sure that's been covered before, more than once.
Yes, and maybe not a bad idea for some redundancy in securing the plug option...
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Old 7th Jan 2024, 20:58
  #292 (permalink)  
 
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Locking Mechanism

Originally Posted by DaveReidUK
Thanks for that - I hadn't seen the latest video, which makes everything clearer. Mea culpa.

I note that all 4 bolts are retained by castle nuts and cotter pins (more usually known as split pins). Had those been correctly assembled, I can't see any way that the door plug could have let go. Incorrect assembly could be any of:

a) omitting the split pins
b) omitting the nuts and therefore the split pins
c) omitting the bolts and therefore the nuts and split pins

at any or all of the 4 bolt locations.

Any thoughts?
Looking at the Chris Brady’s still of the outside of the aircraft it can be seen that both hinge posts are still attached to the floor. The hinge guide, the big stop washer, pair of lock nuts and probably the lift assist spring are missing from the forward hinge. The rear hinge appears to have some of these parts still attached (including door bracket ?)
If the stop bolts on one or both of the hinge pillars were not present then the lift assist springs would be continuously trying to lift the plug and disengage the roller pin from the guide track. If the stop bolts on the guide tracks were effective then this shouldn’t matter but the departure of the plug suggests that they were not. From the photos it is difficult to gauge the angle of the guide tracks but it might be possible that the internal pressure force on the plug would result in an upward component adding to the load on the roller pin?

Thoughts?



Acknowledge Chris Brady’s info.


Last edited by Europa01; 8th Jan 2024 at 07:25. Reason: Addition of Photo
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Old 7th Jan 2024, 21:07
  #293 (permalink)  
 
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Originally Posted by ThreeIfByAir
In both cases the frame of the door or plug is secured to the aircraft with what appear to be twelve bolts/large screws installed from the inside.
Not being sufficiently familiar with doors, or plugs, like this one, I thought the same thing at first. But those are not bolts or screws, they are "stop fittings and stop pads." The latest video by Chris Brady answers most of the most relevant questions about the construction of the door plug. It's posted above, most recently at #281.
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Old 7th Jan 2024, 21:09
  #294 (permalink)  
 
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Originally Posted by DaveReidUK
Incorrect assembly could be any of:

a) omitting the split pins
b) omitting the nuts and therefore the split pins
c) omitting the bolts and therefore the nuts and split pins

at any or all of the 4 bolt locations.

Any thoughts?
Two additional possibilities:

1. Incorrect size bolts or inferior bolt material.
2. Some portion of the door structure was damaged during installation by using an unapproved procedure (e.g., AA 191 or UAL 811)
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Old 7th Jan 2024, 21:19
  #295 (permalink)  
 
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It's now being reported that the FAA are insisting that even aircraft that have undergone the AD inspection and been cleared, should still be grounded pending additional maintenance action:

FAA says some Boeing 737 Max 9 planes may need maintenance to prevent another blowout
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Old 7th Jan 2024, 21:33
  #296 (permalink)  
 
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Originally Posted by DaveReidUK
It's now being reported that the FAA are insisting that even aircraft that have undergone the AD inspection and been cleared, should still be grounded pending additional maintenance action
This is sort of old news getting recycled as new. It was reported yesterday that Alaska had 18 MAX 9s that had recently returned from heavy maintenance, which included a detailed inspection of the plug doors. Based on this action, Alaska allowed those aircraft to return to service (see my post #101). This was before the AD. As far as the additional maintenance, as far as I know, the FAA has yet to specify any of the specific actions necessary to return the MAX 9s to service.
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Old 7th Jan 2024, 21:59
  #297 (permalink)  
 
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Thanks for posting that, I'll fly with that guy any time!
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Old 7th Jan 2024, 22:27
  #298 (permalink)  
 
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Here is what I see from an engineering viewpoint.
The first image shows the stub guide location and due to its length, guides the door up and out. This would be how it functions when the extra exit door is installed.

Where the stub guide would be

In the second photo taken from the incident aircraft, we can see the stub guide indicated by the red arrow,. The blue arrow shows it has a threaded hole in it and that is where we would expect to see a locking bolt for when a permanent plug door is in place.

Shows the stub guide in place on incident aircraft

The third image shows where and how I would see the locking bolt in situ if it were ever installed.

shown with locking bolt
,
To me it seems the locking bolts were never installed.
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Old 7th Jan 2024, 22:38
  #299 (permalink)  
 
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Originally Posted by flynerd

The third image shows where and how I would see the locking bolt in situ if it were ever installed.

shown with locking bolt
,
To me it seems the locking bolts were never installed.
The locking bolt is in position in this image. The sketched in bolt is not in the right location or orientation.
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Old 7th Jan 2024, 22:43
  #300 (permalink)  
 
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Originally Posted by flynerd
Here is what I see from an engineering viewpoint.
The first image shows the stub guide location and due to its length, guides the door up and out. This would be how it functions when the extra exit door is installed.

Where the stub guide would be

In the second photo taken from the incident aircraft, we can see the stub guide indicated by the red arrow,. The blue arrow shows it has a threaded hole in it and that is where we would expect to see a locking bolt for when a permanent plug door is in place.

Shows the stub guide in place on incident aircraft

The third image shows where and how I would see the locking bolt in situ if it were ever installed.

shown with locking bolt
,
To me it seems the locking bolts were never installed.
The bolt is not in that location. From the most recent Chris Brady video it is actually perpendicular and its nut is visible in the photo as marked by the blue arrow below:

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