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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 8th Jan 2024, 05:33
  #341 (permalink)  
 
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The door plug has been found! Below is a link to a comprehensive news article including a video of NTSB press conference.


News article with NTSB brief regarding found door plug
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Old 8th Jan 2024, 06:12
  #342 (permalink)  
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As an aside…. I’m sure Apple will be all over it for an ad.

Found an iPhone on the side of the road... Still in airplane mode with half a battery and open to a baggage claim for #AlaskaAirlines ASA1282 Survived a 16,000 foot drop perfectly intact!

When I called it in, Zoe at @NTSB said it was the SECOND phone to be found.,,,





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Old 8th Jan 2024, 06:19
  #343 (permalink)  
 
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NTSB "B-Roll" Video

Plug diagram from NTSB/Boeing

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Old 8th Jan 2024, 06:51
  #344 (permalink)  
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Originally Posted by GarageYears
From the BBC:

“A teacher called Bob found the missing section in his yard, the chair of the organisation leading the investigation said on Monday.”

No further details. But well done “Bob”

- GY
Later version:

Ms Homendy later announced that the part of the fuselage that detached had been found, after a teacher named Bob located the missing section in his yard.

Perhaps the BBC writer or editor noticed something that occurred to me straight away I saw the first quoted version, that it wasn't yet Monday in that part of USA at the time of writing.
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Old 8th Jan 2024, 06:56
  #345 (permalink)  
 
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We’ll soon know if safety bolts were in place. Without them what prevents door disengaging under negative G and low cabin pressure? Or more likely jiggling loose under a series of reduce G encounters, again with low pressure differential.
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Old 8th Jan 2024, 07:00
  #346 (permalink)  
 
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Originally Posted by JamaicaJoe
Can we all agree that the missing part of the plane is a "door" that replaces an emergency exit "door, That it is NOT a "plug"?, it is not designed as a "plug", does not function as a "plug" under pressurization of the hull. In fact, it performs exactly the opposite. The outward forces work to stress the door against its retainers not the frame in any intrinsic or hermetic manner..
The item is a “door plug” it is not a “plug door” - different definitions
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Old 8th Jan 2024, 07:02
  #347 (permalink)  
 
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Originally Posted by JamaicaJoe
I think the guide roller on at least the side shown in photos was not long enough to reliably engage the door. The four bolts really do nothing to secure the door , rather prevent movement of the mechanism.
You are ignoring the fact that when the door is in place there are no (should not be, see below) any significant loads on the guide and pin. The only load is that from the lift assist springs. It appears that even this is minimal if the lower bolts are fitted.
So if lowwer bolts missing it's possible that the spring loads caused an upper boult or guide to fail but this seens unlikely to me.
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Old 8th Jan 2024, 07:03
  #348 (permalink)  
 
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Originally Posted by JamaicaJoe
A couple comments:
1) Can we all agree that the missing part of the plane is a "door" that replaces an emergency exit "door, That it is NOT a "plug"?, it is not designed as a "plug", does not function as a "plug" under pressurization of the hull. In fact, it performs exactly the opposite. The outward forces work to stress the door against its retainers not the frame in any intrinsic or hermetic manner..
I think you lost that semantic battle nearly 40 years ago when the A320 first flew with pretty much that same semi-plug design on all its main-deck doors.
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Old 8th Jan 2024, 07:12
  #349 (permalink)  
 
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Follow on to my response to JamiaJoe above. I said there should not be significant loads on the quides, pins or upper lock-out bolts.
Unless of course, as I suggested yesterday, the stops were not correctly adjusted. This would put pressurisation loads on the guide / pin possibly resulting in low cycle fatique failure of the guide / pin/ bolt and loss of the plug.
I've seen no comment on this theory.
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Old 8th Jan 2024, 07:17
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Originally Posted by DTA
Could the door have been damaged on the ground? Just looking at the white marks either side of the opening in the above photo.
Far more likely to be the result of the bits you see hanging outside the door aperture bashing against the airframe in the slipstream once the plug had departed
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Old 8th Jan 2024, 08:19
  #351 (permalink)  
 
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Quite a lot of detail here in a USA NBC account, including a range of comments from the NTSB

Missing door plug that detached from Alaska Airlines plane found in Oregon backyard (nbcnews.com)

Notable is it had pressurisation issues on both the two days before the accident, and although removed from ETOPS as a result, it states "the inspection had not been completed". Which is not surprising because it had been in full all day use every day. The accident flight was right after arrival in Portland from New York. It's also apparent, from the usual "reading between the lines" of accident investigator comments, that they don't like the idea of this sort of door plug at all, and would rather either proper fuselage structure or a proper exit door. Which as it makes its was back to the FAA could lead to some interesting decisions.
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Old 8th Jan 2024, 08:29
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Originally Posted by MLHeliwrench
The door plug has been found! Below is a link to a comprehensive news article including a video of NTSB press conference.
From another news article:

"Jennifer Homendy, chair of the National Transportation Safety Board, said at a news conference that after Alaska Airlines Flight 1282 returned to Portland International Airport, no one pulled the circuit breaker on the cockpit voice recorder or otherwise preserved the audio, which holds only its most recent two hours.

“The cockpit voice recorder was completely overwritten. There was nothing on the cockpit voice recorder,” Homendy said.
"

"The NTSB chief revealed that Alaska Airlines had blocked the plane from being used on flights to and from Hawaii because of a warning light that had lighted up at least three times, possibly indicating a pressurization problem on the aircraft.

The warning light had turned on during flights on Dec. 7, Jan. 3 and Jan. 4, and each time, maintenance crews tested and then reset the light.

“We don’t know that there was any correlation” between the warning lights and what happened during Friday night’s flight, Homendy said. But Alaska Airlines had restricted that jet from transcontinental routes so that the plane could return to an airport during an emergency, she said.

Because the pressurization light had gone off several times, additional maintenance was ordered on the plane, but it had not yet been performed before Friday’s flight."


(Source: https://www.latimes.com/california/s...warning-lights)



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Old 8th Jan 2024, 08:41
  #353 (permalink)  
 
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CVR

What a shame the CVR data was over-written. Does AS have an SOP for data preservation? If not, why not? I appreciate this crew had just been put through the wringer and it might not have been top of their agenda, but that’s why an SOP is important.

Interesting to see that an explosive decompression that was violent enough to blow open the flight deck door and remove the FO’s headset wasn’t sufficiently violent to warrant the use of ’Mayday’.
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Old 8th Jan 2024, 09:09
  #354 (permalink)  
 
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If correctly installed this door plug should never ever move.

Given the amount of differential pressure acting upon it at cruising altitude (~8psi) these considerable forces should be taken up by fixed stop pads- giving a mechanical face-to-face contact between the plug & the surrounding fuselage.

In any normal circumstances the amount of differential pressure acting on a regular cabin door will lock it totally solid in flight. You cannot physically open a door using the internal handle at altitude with the jet pressurised as you cannot overcome these forces.

From the images there would appear to be 6 bolts per side installed at manufacture which additionally hold the plug in position vertically & horizontally. These shouldn’t take any of the pressurisation loads however.

Given the low cycles of the airframe I would be very surprised if fatigue is a factor.

With previous potential indication &/or pressurisation issues &/or possible work carried out in that area then there is potential for human interaction/error. All conjecture of course.

The problem with any of these plugs is that they are filling a gap in the fuselage that was originally meant to contain a door. Whilst they are generally a fit & forget solution at manufacture- they are removable.

The only saving grace from this incident is that the incident appears to have happened at less than full diff px- thus the explosive nature has been somewhat reduced. If it had happened in the cruise there would have been a much higher probability of a more forceful depressurisation involving seats & passengers and far greater damage such as happened in historic cases.



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Old 8th Jan 2024, 09:09
  #355 (permalink)  
 
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Originally Posted by JamaicaJoe

2) a) Photos of one guide pin on the accident plane appear to show a very short length of the guide pin/roller. Its length significantly less than its diameter. b) The dummy door (not a PLUG) differs from an Emergency Exit Door (not a PLUG) in a significant way. The cross bracing is removed to accommodate a larger window. Could the combination of the panel being weaker at that point have allowed the door (not a PLUG) to bow outward and dislodged the upper portion of the door from the guide pins/rollers? The four rigging bolts would do little to retain the door at this point.
You are forgetting that the door/plug cannot move past the 12 stop pads unless it first moves upwards. If the two bottom locking bolts were in place, such upward movement should have been impossible. If might be conceivable that if the two bottom locking bolts were missing and the two upper ones were in place, then the combination of short rollers/flexing allowed the upper locking bolts to slip past the rollers but that's a lot of ifs.
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Old 8th Jan 2024, 09:13
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Originally Posted by Fortissimo
What a shame the CVR data was over-written. Does AS have an SOP for data preservation? If not, why not? I appreciate this crew had just been put through the wringer and it might not have been top of their agenda, but that’s why an SOP is important.

Interesting to see that an explosive decompression that was violent enough to blow open the flight deck door and remove the FO’s headset wasn’t sufficiently violent to warrant the use of ’Mayday’.
Thinking on it - since that damage happened to the cockpit door, credit to the venting of the cargo area that the floor was not damaged.
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Old 8th Jan 2024, 09:13
  #357 (permalink)  
 
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Originally Posted by Fortissimo
What a shame the CVR data was over-written. Does AS have an SOP for data preservation? If not, why not? I appreciate this crew had just been put through the wringer and it might not have been top of their agenda, but that’s why an SOP is important.

Interesting to see that an explosive decompression that was violent enough to blow open the flight deck door and remove the FO’s headset wasn’t sufficiently violent to warrant the use of ’Mayday’.
Even more significant was the air rush sucked the emergency SOP checklist out of the flight deck. Which presumably contained the CVR switch off command. The crew had to do it all from memory instead.

One day the CVR industry will come up with an ever so simple way to avoid this overwriting. Goodness knows how often it has occurred in incidents in the past. I know the requirement is to maintain the last 2 hours, but that didn't extend to any instruction to start overwriting at 2 hours and 1 minute.
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Old 8th Jan 2024, 09:15
  #358 (permalink)  
 
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Originally Posted by LapSap
Except that I would think something that shape could possibly lose forward momentum quite quickly if tumbling, so that its trajectory quickly becomes more vertical and therefore the radial speed falls below the threshold of Moving Target Indicator (MTI) suppression speed (used to eliminate clutter). If it did paint initially, I suspect it would fade pretty quickly.
They would have been looking at raw data though.

Anyway, they found the door, so, on to the next bit!
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Old 8th Jan 2024, 09:16
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Originally Posted by DaveReidUK
I think you lost that semantic battle nearly 40 years ago when the A320 first flew with pretty much that same semi-plug design on all its main-deck doors.
Actually, I would make that over 60 years ago when the VC10 first flew with this same type of door design. I think the BAC 1-11 used this door design too.

Originally Posted by JamaicaJoe
I think the guide roller on at least the side shown in photos was not long enough to reliably engage the door. The four bolts really do nothing to secure the door , rather prevent movement of the mechanism.
Having looked at Chris Brady's second video on the mid-cabin door plug option, the locking bolts through the guide tracks would need a roller pin to be long enough to rest on top of the locking bolt through the guide track. The forces on that locking bolt are not very high, but another option would be a relatively short roller pin that just clears the locking pin with a bit of flexibility in the fuselage structure. Just speculating... but it's something that ocurred to me when I was looking at the locking bolt configuration (8:50 in that video).
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Old 8th Jan 2024, 09:30
  #360 (permalink)  
 
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Originally Posted by WHBM
Even more significant was the air rush sucked the emergency SOP checklist out of the flight deck. Which presumably contained the CVR switch off command. The crew had to do it all from memory instead.
AIUI they still had the QRH, just the laminated checklist card went for a jaunt.
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