737 Mid-Cabin Emergency Exit Doors - Plug Option
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- Опубліковано 2 чер 2024
- Please note this video has been superseded by • 737 Technical Aspects ...
This video is a follow up to yesterday’s video on 737 Mid-cabin Emergency Exit Doors. In it I focus on the construction and securing of the plug option.
This is in response to the incident to Alaska Airlines flight AS 1282 whose mid-cabin emergency exit door plug detached in-flight whilst climbing through 16,000ft on 5 Jan 2024. Fortunately, there were no injuries.
** Errata **
In this video I state that a downwards force is required to remove the door plug. I based this statement on text in the AMM SDS which I now believe to be incorrect or misleading. It is possible that a very small downwards motion (1-2mm) is first required to be able to free the locking bolts. But the door must be moved upwards by a couple of inches to clear the guide tracks. Apologies for any confusion.
An updated explanation can be found here • 737 Technical Aspects ...
Contents:
0:58 Introduction
1:24 The Plug Option
3:57 Construction
7:26 Securing The Door
11:39 Alaska Airlines 1282
14:38 Fallout - Наука та технологія
![[柴犬ASMR]曼玉Manyu&小白Bai 毛发护理Spa asmr](http://i.ytimg.com/vi/0TsXQ7z2Dh4/mqdefault.jpg)
Laerned a lot about the B737 with you. Thanks for all the info. Things way clearer now.
Great to hear!
Boeing removes the plug door at Renton to install the interior, and then fastens them again. So the last people to work with this door were at Boeing, not at Spirit Aerosystems.
The Door Plug is installed by Boeing not Spirit Aerosystems as an “optional extra cost” item.
It depends on who outfits the interior right? That’s not always either of these companies.
@@Prxyshj Boeing fits the interiors to new aircraft. This aircraft was ten weeks old.
And they smoke dope in Washington.
From reports I've read, the specific Alaska Airlines aircraft had the plug doors opened and interior worked on to install a WiFi upgrade in November-December.
Reuters: Spirit Aero made blowout part but Boeing has key role... Spirit builds fuselages for 737s and sends them by train with the special door assembly “semi-rigged"… 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
See my post above. I don't buy this answer. Look at the pictures of the 737 MAX hulls in transport. www.aerotime.aero/images/Unfinished-Boeing-737-MAX-fuselage-traveling-on-rail-to-Renton-Washington-the-United-States.jpg
Someone screwed up...maybe.🤔
Spirit has problems for sure!!!!
Trying to cheat the employees out of wages and benefits !!!
Thank you ! That's a fascinating piece of the puzzle.
I'm guessing nobody put the bolts in and hey presto there flies the door
Yesterday the video creator stated that the "plug" or more correctly the door blanking panel must be lifted to unhook from the stuctural-pressure-bearing-lugs. Today you say that the panel must be moved down. Looking at the mechanusm and the J channel bracket device it looks like yesterday was correct. Also the castleated nuts on the lockng bolt are locked with split pins. This suggests that they are tightrned to a low torque so as to not crush the upper J-channels or the hollow lower hinge struts. The split pin will prevent the nut from loosening or tightening. The bolt retaining the blanking panel in the closed and locked condition by shear-load on the small bolt.
Agree with your second sentence because it didn’t make sense as stated in this video based on parts involved.
Haven’t seen prior video.
AMM SDS 52-23-00 Page 6 MID CABIN EXIT DOOR PLUG - COMPONENTS, Lift Assist Springs:
"Apply a downward force to the door plug this forces it down until the rollers clear the guide tracks. At this time the door plug can open outboard."
*** Errata ***
In this video I state that a downwards force is required to remove the door plug. I based this statement on text in the AMM SDS which I now believe to be incorrect or misleading. It is possible that a very small downwards motion (1-2mm) is first required to be able to free the locking bolts. But the door must be moved upwards by a couple of inches to clear the guide tracks. Apologies for any confusion.
@@ChrisBrady737 That is hilarious - I mean, it's a nonsense, but so often you see instructions in the AMM that are complete nonsense. I had a case where we had repeated failures in the same systems in our fleet, costing hundreds of thousands of dollars a year. The engineers were diligently following the AMM procedure to test a pressure regulator - I had a good look at the procedure and it was written in a way that if the regulator wasn't regulating, it would nonetheless pass the test to confirm that it is regulating. So I wrote a new procedure, but having told the shift managers that the tests they were doing weren't working, they just replaced all the regulators and the problems haven't returned since. But if they do, the AMM will be changed when they do their next test.
Yes it is alarming that errors persist in the AMM and FCOMs after many revisions@@paulsaccani1115
Spoken with a BA engineer:
The plug doors are habitually removed on the FAL for ventilation, tool access, ease of interior install - then re-installed.
Interesting thank for the info
Not an A/C that is 2 months old
Sounds like either no inspection or removal again without proper RTS
"The plug doors are habitually removed on the FAL for ventilation, tool access, ease of interior install - then re-installed."
As long as each occurrence is documented and done PER the maintenance manual.....shouldn't be a problem.
@@markskibo5159 Huh?
7:22 -Looks like the plug must be raised instead of lowered to release the pin from the track. Minor detail in a great video.
That's what I was looking at also, was going threw the comments to see if someone at seen this.....I am pretty sure he will correct it...
@@paulparisien8198 Great video otherwise.
Agreed.
AMM SDS 52-23-00 Page 6 MID CABIN EXIT DOOR PLUG - COMPONENTS, Lift Assist Springs:
"Apply a downward force to the door plug this forces it down until the rollers clear the guide tracks. At this time the door plug can open outboard."
AMM SDS 52-23-00 as written means that the diagram at 6:30 does not apply to the door plug option, which shows the guide track on the door plug opening downward, so that the plug would need to be raised, with spring assist, to get the open end of the guide slot over the roller pins mounted to the fuselage to open it. The instructions imply that the guide tracks would need to be installed on the plug with the open end up. However, 8:50 clearly shows that the open end of the guide track faces downward, thus the plug in this photo must be raised to release from the roller.
Alternatively, the instructions in AMM SDS 52-23-00 may have been written in India, along with the flight software.
This documentation discrepancy is important to investigate, as it impacts the possible failure scenarios.
Two great videos on this issue. I really appreciate you bringing this level of detail!
Seems to me the only way that door could move is if the bolts weren’t secured or even installed. If everything was installed properly there is no way for the door to move with out major damage to the area.
I seriously doubt there is an underlying design flaw with the plug as they have been flying for years in the 900ER without incident.
Shift Change in the middle of installing the plug...It NEVER got the "Capturelock" bolts installed...No people where in those SEATS on Purpose cause too many passengers complained of Noise and Draft ,,ASK the Crew why those seats were EMPTY.......!!
the upper pins in the photo that the slots are supposed to lower down upon don't look like they're especially substantial in that image. They look short. I wonder if that's just characteristic of the image, or if they actually are short.
The problem to my admittedly armchair view is that with the springs at the bottom, the plug is designed to lift itself up and off, the springs in the hinge assembly are loaded to tension when the plug is installed. If there's any mistake in securing the plug then those springs are going to make the problem worse.
I'm wondering if the perimeter bolts for the frame attachments were simply omitted, and the bolts used to lock the slots aren't up to the job of holding the door in place in that event, and the door was able to come up and out accordingly.
@@4881828citation needed
@@4881828 Ah HA!!! I wondered if no one had reported this, and combined with cabin pressure squawks was all the airline needed to investigate. Similarly- I boarded a TWA 727 and sat by the exit door, on engine start and rise to idle there was like there was no seal. No engine noise attenuation. Moved to the center seat and my backpack and told the person next to me what to expect if the door separated. Well- it sealed on throttle up and did not leak, so I moved back. I instructed my direct reports it is OK if they did not choose, or wanted to refuse, TWA for company travel. Flight 600 popped 5 days later. I hope an accurate story comes out soon.
@@4881828shift change maybe, but mechanics always leave written 'tie-ins' to alert 2nd shift what they were doing before going home.
Great job, Chris. Thank you for quickly producing these two videos which help people better understand the door plug system.
My pleasure, I hope they are useful
@@ChrisBrady737 Can you confirm that the door sensor / flight lock hardware is not installed on mid-cabin emergency exit plug doors and therefore wouldn't trigger a fault or PSEU indication if the door translated out of the locked position either on the ground or in flight?
@@ChrisBrady737 According to flightaware- there is around 10 max 9s flying as we speak! This is the last thing Boeing needed- because of the MCAS disaster- that was entirely preventable- the scrutiny on this Aircraft is going to be intense. And so much for Boeings request to defer the Anti Ice issue to pilot memory!!
I would suspect that all 737 inspected will have a photo record of what they find with and RII signoff to boot.
Correct, the mid exit door captions should have INOP stickers over them
Great information. I fly this airplane and I always learn something watching your videos. Thanks for taking the time to put together a follow-up. I appreciate your fact based commentary.
Thanks for your kind comments, stay safe!
I'd go peel open the covering and check those bolts being screwed tight with my own eyes before I flew one of those planes...😮
@@jarchdmyep & in the same way that it's always safest to fly on the airline that's recently had a mishap, I'm 100% sure of the engineers who will now be checking EVERY single door-type plug on these aircraft for correct fitment of the locking bolts. This exact problem will not reoccur.
Very good explanation and illustrations of the plug option - Thanks very much!
Great video Chris. Thank you for making that that’s helping a lot of people understand exactly how this latching mechanism is working for the plug option.
The nuts securing the upper and lower movement of the plug door are called castle bolts, bolts that have the look of a castle tower. The pin hold the castle nut in place it called a cotter pin. The cotter pin installation prevents the castle nut from backing off the bolt.
Do you mean the nuts on the bolts are called castle or castellated nuts? Good pickup on the use of split or cotter pins rather than lockwire.
Call them split pins in Australia. (retired Boeing QA 25 years)@@ImperrfectStranger
No argument from me, Leon. I live in Australia :) Cotter pin seems to be used in the Boeing Maintenance Manual though. @@LeonAust
we call them cotter pins and castle nuts in the US. You Aussies always have to have a different word for everything :)
Heres a guess...it was taken out. When re-installed the cotter pin(s) were omitted. Those castle nuts are not self locking. It would work for awhile till vibration loosens it to the point of failure. My guess is the top 2 cotter pins were omitted. OR the plug itself failed.
Finding the door should help.
Congratulations on your proper pronunciation of Oregon. Very few English speakers outside of the western United States pronounce it correctly.
Very good reporting. Thank you for the photographic details graphs and charts. Well done. Bravo.
Thanks for watching
Great vide Chris. Thanks for taking the time to create and share.
You are welcome, glad it was useful
Thanks for the detailed technical video on this unknown to me aspect of an airplanes structure. The video alone made me subscribe. Happy new year!
You are very welcome. Thanks for subscribing.
Thanks - really appreciate this detail. I am a recently retired 737 captain.
I can’t help feeling that somebody stuffed up badly by either not installing or securing bolts, a very disappointing failure.
You wouldn't even buy a new car 🚙 with door bolts missing let alone an airplane ✈. 🥸
Any door departure experience?
Excellent video, Chris. Thank you for your effort.
You are welcome
Best video on the internet regarding this issue. Thanks Chris
Many thanks, glad you enjoyed it!
Looking at these assemblies and detail parts makes me recall my time in 777 final assembly. Commercial aircraft are a conglomeration of many tens of thousands of parts, a lot custom made, and all assembled together by hand piece by piece with numerous fasteners. Opportunities for error are abundant.
One of the most common root causes of disasters is Shift Changes. A worker does part of a job, goes off looking for the needed lock bolts, castle nuts, and cotter pins, the whistle blows, and he leaves. The next shift worker doesn't realize that the job was left unfinished. A good scenario is that first shift finishes the work that required the plug to be open, and pulls it shut. Second shift comes on, and installs the headliner without noticing that the lock bolts weren't installed. With the headliner in place, the locks can't be inspected. Oh well, let it go, plane is scheduled, it's probably OK.
Something similar happened to a turbofan engine, with which I was familiar, some years ago. In flight, an ‘unbent’ split pin (UK term for a cotter pin) retracted from a mechanism. This meant that the engine could not be throttled back for landing. Nevertheless, the pilot was able make a successful landing, but at a much higher speed than normal.
It was probable that the the split pin did not get bent because of a shift change or a meal break.
Well, I think a lot of steps was missing to do not intall bolts and/or cotter pins. In the place where I work if you don´t complete a Task sing just line you done and sometimes make a coment, and always task printed in paper. So next worker know what to do exactly. And before intall cabin panel (in this case) a quality control check works in area. Im talking about factory and C-checks facilities cos Alaskan 737 is a baby plane only 2 or 3 months old.
I wholeheartedly disagree.
Factory assembly lines, especially in the USA, have a high degree of quality control. We aren’t employing children like certain other countries and have many standards and checks. The company itself oftentimes has better internal quality control than what’s required through government regulations.
That’s A LOT of missing pieces to blame on mere shift changes.
@@angieg2561 4 bolts, 4 nuts, 4 cotter pins, but that's still just one job item, should only take a few minutes. Also supposed to be signed off by an inspector.
A big part of the problems at some Boeing plants is elimination of QA/QC, workers are expected to self inspect their work, but not allowed time to do the inspection. Workers are then blamed for defects because they are not allowed time to do the work right.
@@angieg2561 Boeing got rid of QA/QC in some areas, it was holding up production. Shouldn't be that way, but it's all about "shareholder value".
Thank you for your detailed explanation of the “door plug” construction.
At 7:00 it says in the third paragraph: “To open the door plug, a downward force is needed to force it down against the lift assist springs until the rollers clear the guide tracks.”
If the guide rails are attached to the "door plug", the description in the paragraph should be: “To open the door plug, an upward force is needed to force it up assisted by the lift assist springs until the rollers clear the guide tracks.”
Agreed-he had it backwards. Very clear from looking at the design. Lift up to open.
*** Update ***
In this video I state that a downwards force is required to remove the door plug. I based this statement on text in the AMM SDS which I now believe to be incorrect or misleading. It is possible that a very small downwards motion (1-2mm) is first required to be able to free the locking bolts. But the door must be moved upwards by a couple of inches to clear the guide tracks. Apologies for any confusion.
Great explanation of this door/ plug design. Thank you
You are welcome!
Chris the Boeing 737NG-900ER also has plugs installed. Last night we reinspected a -900ER for any discrepancies and found none. That aircraft had over 41,000 hours TT. If N704AL had failed the decay check: quite easy to perform, it would have been found and solved, so I feel that that was speculation on the pressurization issue. These plugs are not on line item inspections and only get inspected during a heavy check, there would have been no previous inspection done since it was such a young aircraft. BTW I love your channel keep up the good work. As you stated in this video there would have been a catastrophic failure of six different bolts to produce this effect. I await the NTSB report of their findings.
Not necessarily a catastrophic failure of six different bolts, if all of the nuts were never tightened or even entirely omitted, one would only need vibration and pressurization/depressurization cycles to potentially back the bolts out. Unless there's an obstruction present to prevent that from happening, which doesn't appear to be the case.
In that type of case, assembly practices being adjusted and a slightly more fault tolerant design would entirely mitigate the issue.
Either way, that's why they do thorough inspections and investigations.
@@spvillano That's my feeling on what happened. The nuts were not torqued up, vibrated loose and the rest is history. A quality management issue from Renton.
@@cjmillsnun That has gotta be the reason! I can't think of any other cause- as I don't see any structure damage!!
They're castle nuts with wire locks, so IF the issue is missing bolts it's not just a torque issue. Missing wire locks would be an easy thing to spot.
@@SteveSmith-cd4hs It s gotta be the case, an inspection by a Inspector was simply pencil wipped or forgotten in the Aircraft paperwork! All doors require 100% Inspector buyback!!
6:30 The “roller pin” doesn’t go anywhere, it’s attached to the frame and stationary, it can’t move around a corner. The “guide track” attached to the door is what moves. The only way to disengage the pin from the guide is for the guide to move upward (along with the door), with assistance from the lift springs on bottom hinge assemblies.
Does make more sense to me else those springs wouldn't be the opposite of a 'help' opening the thing.
@@secondskins-nl Well, without the bolts, it looks like it just needs a yank upwards and slight push and there you go... A minute turbulence at altitude would open it... well, about the way it opened.
Now, the question is, was it wise to make (the plug) springy to open with easily detaching single-and-only safety device (bolts) instead to make it harder to open but foolprof to put back?
Yes, the diagram reflects what you say. But the instructions in diagram say to move plug downward to open.
The roller pin is part of the door. The track is in the frame.
The lift springs hold the plug closed in the absence of the bolts by pushing it up on the tracks at the top of the doors.
@@docneleIt needs a yank DOWN to unlock the door (ie a hard landing) in the absence of the bolts.
Many thanks. Your video answers many questions by showing us what a plug versus a door looks like at this location. It is especially useful for those that have never seen it…
Glad it helped
Great video for such a short turnaround 👍
This is by far the best explanation of the MCED plug that I've seen. None of the many aircraft I've worked on had these plugs, and I was very curious about the technical details concerning construction of the plug and it's operation. Thank you for educating me!
You are welcome, glad it helped.
High quality content! Thank you.
Glad you enjoyed it!
Thank you to the fellow for they manual reference. And thank you for the video. I could not understand how the door could depart until now.
From my 737 MRO days I speculate that the bolts and plugs were installed at Spirit Aerospace at Wichita Kansas then transported by train to Seattle, then the bolts and door were removed at Boeing to help workers get interior parts inside the fuselage for installation. 4 bolts failing at once would be quite a coincidence, but the universe is not that lazy. One bolt should have been able to hold that door in especially one of the upper ones on the roller latches since they act in tandem . The two at the bottom looks like it just acts as stops on the hinge.
You did a pretty good job on this. But I think you need to do a little more explanation of the opening and closing procedure. Maybe get a copy of the manual to explain. Your nomenclature was confusing at times. I don’t think you push down the door to get it open. I think you remove the 2 upper bolts then remove the 2 lower bolts. This allows the door to slide up allowing the fitting to slide up away from the rollers then allowing the stops to clear. To close the door you push down allowing the the stops to engage and the roller guides to mate with the rollers then push down on the door to put the 4 locking bolts in.
The Boeing manual is wrong.
*** Errata ***
In this video I state that a downwards force is required to remove the door plug. I based this statement on text in the AMM SDS which I now believe to be incorrect or misleading. It is possible that a very small downwards motion (1-2mm) is first required to be able to free the locking bolts. But the door must be moved upwards by a couple of inches to clear the guide tracks. Apologies for any confusion.
The absolute only way the plug could come out is if *all 4 bolts* were not reinstalled after maintenance. Any 1 of the bolts would have been enough to hold the door down on the pins. Apparently it is common to open the plug for ventilation during MX. Vibration or turbulence in climbout would allow the lift assist springs to lift the track over the rollers.
Since aircraft was 2 months old, would it have had any significant maintenance?
@@tomsixsixunlikely
@@tomsixsix Someone on Blancolirio said that Alaska does an inspection after delivery.
My unsubstantiated guess is that landing loads (when pressurisation is minimal) allowed the springs to push up the door a bit at a time until the door came loose. Each time the door came up a bit, the contact surface and resulting friction would be reduced.
Agreed-any of 4 bolts could have prevented slide of door upwards to clear 12 stop pads and 2 rollers -so it seems highly likely that all 4 were missing. Probably error occurred at last maintenance event when door was last opened.
Clear as crystal. Thank you for this!
Glad it was helpful!
Thank you for your always great insight and your modest way of telling us what you know. No speculation. Let them investigate first. Appreciate this follow up video as all your previous very informative videos. Keep up the good work. Keep the nose high 😊 Brgds from a 737 captain
Many thanks, I appreciate your feedback.
Excellent video Chris, you've explained it all so successfully. I will now have to watch a few more of you're videos!!😅 (Retired aerospace engineer)
Thank you, glad you enjoyed it
Great additions. Very good photos, they giva a good idea of how the plug works and what could have gone wrong.
Thanks, I thought they made the video worth remaking
@@ChrisBrady737 WIthout a doubt. Thanks for your work. Getting praised in the airliners net thread on the incident too.
Yes - our thanks also to the "engineer who sent the photos overnight" !
Great video Chris, keep up the good work.
Thanks 👍
Very descriptive technical video. Thank you.
You are welcome
Between you and Blancolirio we have great information and sensible analysis. Thank you for this. If only the main stream media would either get educated before commentating. 👍
The Blancolirio video shows how the bolts with castellated nuts and cotter pins secure the door to prohibit a depressurization from ever happening. Somebody was sloppy and overlooked installing the bolts and nuts and cotter pins. Luckily, nobody was killed as a result. 🥸
I would imagine that the factory floor people already know just exactly what happened.
100% buyback inspection by an inspector wipped by Ink????
Agreed. Curious to find out if reducing the QC staff has anything to do with it.
We do. In most likelyhood
Somebody at Renton has (4) sets of fasteners in their toolbox that they don’t know they left off the aircraft or they already tossed them into the sewer. Hopefully there’s some security video or something if that’s the case.
Chris - this is a very useful summary presentation. I hope you will be able to create new content as the investigation proceeds. As discussed by other, the problem now seems to be one of the processes around installation and maintenance of the plugs and their lock bolts. Thanks again.
Good factual information. Well done
Excellent job; thanks so much for this content. As a (retired) A&P but who never worked on 737s, I was curious about the design... your video shows it is pretty straightforward and once the door and the locking bolts, nuts and cotter pins are installed correctly, they are not going anywhere. So unless there was a material failure on some part of the door structure, it seems like the investigation will focus on "assembly quality"... who touched this part of the A/C last? Thanks again...
Chris...I think what could be interesting in any follow-up video is to analyze the different ways this could have happened, i.e., different scenarios, for instance, a loose or missing bolt, misalignment, etc. That is not to blame anyone or conclude what happened but a walk-through of the different scenarios that could lead to this.
Those bolts all have castle nuts with cotter pins through the bolt preventing the nut from turning and backing off. The same arrangement that keeps your ball joints in your car! So either the cotter pins were sheared off and the castle nuts backed off, and the bolts fell out (highly unlikely to happen simultaneously on all 4 lock bolts), the cotter pins were missing and the castle nuts backed off and the bolts fell out (highly unlikely on all 4 lock bolts), the cotter pins and the nuts were missing, and the bolts backed out (somewhat unlikely on all 4 lock bolts), or someone missed a line item on some checklist, "install lock bolts, castle nuts, and cotter pins, x4" and there were no bolts, nuts, or cotter pins to begin with (ding ding ding!)
Thank you for the follow up video. Cheers....
You are welcome
Thank you for providing this very useful video.
Boeing doesn't seem to own Spirit Aerosystems, who built this airplane and built and installed the plug door. Unless there is a design defect, this isn't really Boeing's fault, right, or am I missing something?
Excellent video and I guess this has probably been discussed, but at 7:15, I don't see how the door can possibly be forced downward against the lift assist springs until the rollers clear the tracks. The tracks are attached to door and the roller pins are fixed to the frame. Only the tracks move and they can't possibly move downward with the roller pins snugly in place. I saw a comment somewhere that the "downward force" is just to unload the spring pressure on the securing bolts so they can be removed, but I can't see how that's possible either. What am I missing? It also occurs to me that the springs must almost entirely counter the weight of the door, so if the securing bolts are missing, it probably doesn't take much force to lift the door upward when the cabin is unpressurised. Without the bolts, the door would be completely unsecured, correct?
Obviously, in my opinion, whoever assembled the plug in the fuselage failed to put the locking bolt pins in place to prevent movement of the door. There was no sign of structural failure. It simply moved upwards off of the roller pins on top 17:33 and up off if the hinge pins at the bottom!
Obvious to me either a deliberate error, or major failure to follow checklist or instructions.
Hello Chris I came to your channel from Mentour Pilot who is also a 737 Captain who gave to you a huge shout out and recommendation after he explained this issue with the door plugs, so far he has had 40.000 views on his channel this morning on this topic within a 3 hour time frame, I have been a subscriber to Mentour Pilot channel for many years so I trust his knowledge and content, so now I will follow your channel as well thank you. 🙂
Welcome to this channel. I specialise in the 737 and go into it in great depth.
Very good Chris. The description was spot on except one key item.
No big though. You said the door traveled upward during closing.
I deliver the FAA certification courses for passenger and cargo doors, but only our twin aisle aircraft.
*** Update ***
In this video I state that a downwards force is required to remove the door plug. I based this statement on text in the AMM SDS which I now believe to be incorrect or misleading. It is possible that a very small downwards motion (1-2mm) is first required to be able to free the locking bolts. But the door must be moved upwards by a couple of inches to clear the guide tracks. Apologies for any confusion.
Great update to yesterdays video. Kinda confirmed my suspicion, and me not knowing the door/plug architecture, that there is a chance that the locking bolts might have been missing. I can't wait to see what the NTSB finds out when the investigation is done.
Thanks for the update video.
KINDA?
@@K1OIK yes, kinda. First of all, that comment is from 2 weeks ago, where there was absolutely no information available at the time. And as far as I know, no determination has been made on the situation of the plug retention bolts. The loose bolts that were found so far were the frame retention bolts, not the plug retention bolts. And those were not the bolts that failed during the Alaskan incident. So, yeah, kinda.
Saying anything beyond that would be non-factual and pure conjecture.
@@idontlikespm is kinda a word?
@@K1OIK yes, it's a slang/colloquially used version of 'kind of'. But thanks for arguing on the Internet about a word you're unfamiliar with, instead of giving a productive addition to the subject at hand. Very informative.
@@idontlikespm Even my 4th grade students are not so lazy to say kinda in writing.
3:07 door plug vs actual emergency exit 3:45 plug has bottom hinge, opens outwards for maintenance / inspection 4:52 inside view 6:29 guide track 7:34 securing door plug. 4 bolts prevent vertical and outward movement 8:51 upper locking bolts. Note captive bolts. 9:47 lower locking bolts
Another glaring difference. Emergency doors have Warning indications. AFAIK this plug has no warning system. Unlike every other opening into the Pressurised compartment.
I heard of your channel from Blancoliro Channel. Yes, I found your video to be insightful and educational. Yes, you have another subscriber.
Thank you, glad it was useful
Very informative video, excellent information as always.
Glad it was helpful!
Can you please send this to the media? They are so clueless and repeat what has been said over and over, and . . .
The BBC have it
@@Plutogalaxy yeah, 1-900-IdontDoMyHomework.
News networks used to retain entire networks of consultants in all manner of fields. Cost cutting over the decades have massively reduced that to the point of abject incompetence.
The media seem to be rather clueless on everything they report
Most people (the ones that aren’t watching these kinds of videos, wink) are clueless regarding anything technical. It’s not just the media.
@@ChrisBrady737send it to American news channels, they’re absolutely clueless
Surely if the guide track is on the door the springs are trying to lift the door guide track off the roller pins, and the springs hold it up to clear the pins when open. So to "close" the door the springs have to be overcome DOWNWARDS TO LOCK THE DOOR, this means that if the locking pins aren't fitted then the door doesn't fail "safe" it fails "open" with only an assist needed from turbulence to open it fully and the door unlatch, if I am right then either you swop the roller and guide around so the springs hold the door closed or you remove the springs so the doors weight holds it in the locked position. Your dotted arrow at 7.25 should show the opposite direction of operation. Ive never worked these jets, I am just looking at the pictures, but I think I am right unless of course some one with experience on type knows better.
Its my belief that none of the 4 plug bolts or 2 pairs of lock bolts or 2 lift assist springs were installed. The door would sit in the lower position, and restrained by the two curved L-shape tracks and 12 pads. Any large shocks to overcome the weight of the door and friction, would allow the Plug to clear the tracks and pads, and pop outward into the air stream. I cannot fathom any other scenario, however extreme. As you indicate, any one lock bolt would keep the door in closed/down position. Just an MSME with 45 years experience.
Among the lot of speculation of the Alaska Incident. Is quite nice to find a Good, Simple and Technical explanation using the proper words and terminology. Thanks and keep the good work...
I’m an Aerospace Engineer working in Wichita. I dont work for Spirit anymore but I did briefly. I’m pretty sure Boeing takes the doors and plugs off of the fuselages in Renton. Spirit only partially installs them here in Wichita before shipping them off. So it’s gonna be hard to say who screwed up I think. But it sounds to me like Boeing has the responsibility for final installation of the door plug so I’m not sure how they could push the blame on Spirit.
Do you know if the airframe had the satellite antenna fitted when it left the factory?
Your slide at 3:43 states that the DOOR “must move DOWNWARDS to clear the stop fittings before [the door] can fold down”. And your slide at 6:30 states that “to OPEN the door plug a DOWNWARD force is needed…until the rollers clear the guide tracks.”
Unless I’m misunderstanding how this works, I think the explanation is backwards. It appears to me that the DOOR must move UPWARDS to clear the stop fittings and to OPEN the door an UPWARD force (assisted by the lift springs) is needed to push the door/guide track UPWARD to clear the roller pin/stop fittings.
Also, the slide at 5:45 should state that the primary purpose of the Lift Assist Springs is to provide an upward lifting force to assist in lifting the door such that the guide track clears the roller pin and the stop fittings clear the stop pads. Secondary function of the springs would be to make sure the door will not fall back in the closed position.
The slide at 9:06 shows the downward path of the roller guide.
It may be pushed down to clear the roller guide and then lifted to clear the door frame. (?)
@@jonathanbott87looking at that picture at 9:06, either the “upper guide track fitting” is moved upward to disengage from the “upper guide roller” or the “upper guide roller” is moved downward to disengage from the “upper guide track fitting”. It looks to me like the “upper guide roller” is securely fixed to the cabin airframe and doesn’t slide therefore it is the “upper guide track fitting” that is the moving part. If the “upper guide roller” stays in a fixed position then the “upper guide track fitting” must be moved UPWARD for the “upper guide roller” to be disengaged from the track. If the “upper guide roller” can move then I’m wrong. If I am correct, then assuming the “upper guide track frame” is attached in a fixed position to the plug door, then the entire door is moved UPWARD to disengage from the “upper guide roller”.
@@jonathanbott87 The guide is on the door, which would need to move up to clear the roller on the frame.
@@MCLastUsername On Boeings, the guides are usually found on the door frames. Is this different? When you open, say, a regular Boeing 747 door, the door handle moves the rollers (which run in the frame guides). I'm not sure what the springs do on this mid-cabin door plug.
@@ImperrfectStranger I'm no expert, I'm just going by the photo at 4:50 clearly showing the guides on the door and pins on the frame. In the photo at 9:06, the door is on the left, as you can tell from the arrangement of the stop at the bottom of the photo.
It is my understanding that the door and frame design has not changed on the 737 for the Max series. It's the same as it's been for many years and many variants of the 737, so this isn't a new design issue. I'm going to speculate that someone failed to install some or all of the four bolts.
That seems the most likely explanation.
Thanks again, for all the details
My pleasure!
Great explanation as I’m use to the 800 NG’s and have very little knowledge of these type of doors. Glad someone else picked up on the movement of the door and guide track on opening at 6:28. The door must move up and not down as stated in the video otherwise it would just be contacting the roller. Lots of unknowns at the moment but questions about the bolts being fitted or possible failure must be the leading question.
Excellent video and done very quickly, which wil hopefully limit the amount of misapprehension in news reports and on social media.
The door has to be lifted up, not forced down (as you say), to clear the stop pads and free the guide roller from its guide track. The diagram makes this obvious - the roller pins are attached to the door frame, the guide tracks to the door plug. As does the terminology "lift assist springs".
All four bolts prevent vertical movement. Vertical movement is necessary to clear the stop pads and before the door or door plug can move outwards.
It's fortunate that the door plug did not impact the tailplane.
The door plugs are "installed but not finished" by Spirit Aviation (which used to be Boeing Wichita) - apparantly Seattle removes the door plugs to use the openings to get internal fittings and finishings into the fuselage, then reattaches the door plugs, closes them and fits the safety bolts.
You are correct - *** Errata ***
In this video I state that a downwards force is required to remove the door plug. I based this statement on text in the AMM SDS which I now believe to be incorrect or misleading. It is possible that a very small downwards motion (1-2mm) is first required to be able to free the locking bolts. But the door must be moved upwards by a couple of inches to clear the guide tracks. Apologies for any confusion.
@@ChrisBrady737 Hi Chris, thank you for the great video and the correction. Do you know if any passengers complained that these plugs make a lot of rattling noise during take off?
@VolkanYuksel Unfortunately I don’t know that. I’m sure it will come out in due course.
I visted Spirit Aero in Wichita about a year ago. I was there as a Supplier Quality Engineer for a Prime. I wasn't there for the 737s. The facility was quite impressive. I've worked in aerospace manufacturing for many years. Quality is slipping everywhere. People like to blame C0v!D, and it is certainly a factor, but the diminished quality has been going on for more than a decade.
"but the diminished quality has been going on for more than a decade."
Why?
@@edumacat3d Oh come on now.......what is all that about d, i and e ???? What are you talking about?
@@rael5469all the blaming of "DEI" going around is code for "I'm a racist white male who's intimidated by anyone else having a job"
@@rael5469 MBAs and the relentless pursuit of more profits!
@@douglasphillips1203 "diversity, equity and inclusion"
I see what you mean Doug. You are quite correct. I am in my 60s and I have seen ZERO evidence that D.E.I is responsible for ANYTHING these racists claim it is. Can we all just get along? I mean....really.
🙏Thank you for all the information. Just found your great channel and subscribed.
Thanks for watching and subscribing, I hope you find the videos useful.
I'm guessing that more training for the assemblers will be necessary in future. I'm glad I came across your vid. It really shone a light at the accident. Thanks!
Thanks for watching - and for the coffee!
You're welcome and coffee sure is cheap where you live.@@ChrisBrady737
Watching the video up to 8:25, it is plain and simple all of the four bolts were not installed, for whatever reasons. These bolts are not under any tensile load, and their jobs are only to prevent the door from moving upwards and allow the guide tracks from disengaging from the guide pins. This must had happened during production, but more likely resulted from some service grease monkey either forgot, or didn't think they are important, let alone critical.
When the door hinged open during flight at 16,000 ft, the force from the aerodynamic drag must caused the door to be ripped off the two bottom hinges violently. I would expect the airframe where the hinges are fastened to be damaged.
It amazes me how both FAA and NTSB downplayed the seriousness of the incident.
I am seeing something a bit different in reference to 6:30 in the video. The lift assist springs are applying upwards pressure to the door. For a plug install you would swing it in and use downwards force to engage the upper guide fitting. If you were to release the downward pressure the door would flop open by itself. That is what you would want if it was an emergency exit door, turn the door handle and it would force itself open. The bolts in the upper and lower guide fittings keep the plug closed by arresting the force of the spring. Pinning it in place so to speak.
Thank you, I am currently stopped at 7:30 in the video, trying to understand it, and your description helps clarify. Am I correct: (1) the roller is fixed to the fuselage, (2) the guide track is fixed to the top of the plug door assembly, (3) the lift assist springs are at the bottom of the plug door assembly, and are compressed to apply an upward spring force when the door is in its closed position (e.g. normal daily operation.) So to open, the lift assist springs help (assist!) lift the entire plug door assembly, which lifts the guide track upward and ultimately clear of the roller, is that how you understand it?
If that understanding is correct (and I'm ready to be told I'm wrong) then this description in the graphic seems inaccurate: "To open the door plug, a downward force is needed to force it {the door plug?} against the lift assist springs until the rollers clear the guide tracks." If the guide track is on the door plug and the roller on the fuselage, and the roller is sitting at the "top" of the guide track, then pushing the door downward would only seat the guide track more firmly against the roller, already at the top of the guide track, wouldn't it?
I feel like I must be misunderstanding something. What are we calling the "Door" and what are we calling the "frame"? Maybe I have these two backwards. Put another way: Is the guide track attached to the removable door plug, or fixed to the fuselage opening? And likewise, are the roller pins attached to the removable door plug, or fixed to the fuselage? If my understanding is backwards, then that would explain my confusion.
I suspect the door isn't lifted by the springs alone; they wouldn't be called lift *assist* springs if they did *all* the lifting? So my guess is that the springs make the door feel a lot lighter, but you still have to lift the door. But I'm 200% speculating, correct me if you know for sure that I'm wrong.
@@svyt Your 1st paragraph is correct.
@@TheHuesSciTech If an exit door was installed the springs would have to be sufficient enough to lift the increased weights of the door latching mechanism and slide assembly. Also this emergency exit would very likely be operated by a passenger in that row. You should only expect someone to be able to operate the handle in an emergency, not go through other motions to release the door.
@@Cobalt135 Thanks - and I mean this respectfully - just trying to evaluate the credibility of your information - you are confident in this information based on specific knowledge, or speculation of how you think it works. (I admit that I 100% do not know!)
Edit to add: Never mind. I made the mistake of posting all of this while I had the video paused around the 6 - 7 minute point. Later explanations and photos confirm all of this. Guide track on the door plug, roller pins on the door frame (i.e. fixed to fuselage, effectively.) Sorry wasting your time and questioning your info before I went further into the video!
Based on this, I suggest that the last statement in the graphic from 6:26 to 7:26 is incorrect: "To open the door plug, a downward force is needed to force it against the lift assist springs until the rollers clear the guide tracks." This is inaccurate, because in the normal "closed" position, the door plug is already forced down against the compressed lift assist springs, so the statement for how to open it should be something like "To open the door plug, after removal of the two upper locking bolts and the two lower vertical movement arrestor bolts, the plug assembly is lifted (with the help of the lift assist springs) so that the upper guide tracks move upwards off of the roller pins to release the top of the door so it can hinge outward."
Excellent video. The aviation community thanks you! This will definitely be an interesting investigation by the regulatory bodies.
Thanks Jimmy
Thanks for your informative video!
My pleasure, thanks for watching.
What type of inspection process are components such as this subjected to once installed? Is there a list of workers / inspectors who were involved in the manufacturing process? I work for an auto manufacturer and they can look back to see who tightened a specific bolt on a day / time.
Generally, yes, aircraft have a quite detailed maintainance log attached to them.
So to be clear, the door slides UP the hinge rods to clear both the pressure clamps and guide pins before open out and down.
And in order for any of that to happen, four locked through bolts have to be removed. And any one of these bolts would be enough to secure the door in place. Pretty clear then that someone overlooked something, and the final responsibility is probably with Alaskan regardless of what Spirit/Boeing did or didn't do. Although that will depend on the depth of checks during the entry to service hangar input if any work was undertaken in the area of the plug/door during the hangar input on Jan 1st.
I doubt that anybody at Alaskan touched the plug tbh...
@@oj2372I've seen speculation that this door is opened for seat install. And may have been opened by AS during initial service.
@@jonathanbott87 I would have thought the seats are already installed by the factory. Would opening those 2 doors speed up the install process really that much?
@@oj2372 Seats are installed after it leaves the production line as they can vary a lot between customers and are routinely swapped out during the aircrafts lifetime. I dont know if Alaska Air have their own MRO available to add/remove seats but it can only be done by an approved MRO facility. Considering the aircraft was so new, it would not have gone for a check yet but its an interestng theory that maybe the door was fitted correctly at the factory but opened again when the seats were added and not secured properl;y afterwards.
@@oj2372 on a 737? Absolutely. The other two options are remove the bulkhead/wardrobe by L1 or remove one or both rear toilet modules to be able to get the seats around the corner through the rear galley.
Going in through the door in question you could have several seats on a staging platform and pass them straight through the door. No bending/twisting/taking chunks out of either galley or trashing the seats trying to force them in.
As an aircraft mechanic new to Boeing these videos are very helpful
That is great to hear, thanks for watching.
Excellent info piece. It's early days yet. NTSB will get to the detail.
Very informative! Thank you! So my personnal conclusion is that the technician(s) who installed that door either didn't put in the locking bolts... or didn't even put them in at all. I can easily imagine the end of the shift and the door has just been installed but the bolts not fitted yet. Everyone leaves. The next day, since the door is already installed in the frame, the next assembly step goes on... and the mistake can never be noticed afterwards because that step would be installing insulation.
Which would mean the person in charge of installing the door didn't care enough to complete their work before leaving... and the person in charge of the technical inspection never actually checked.
"…either didn't put in the locking bolts... or didn't even put them in at all."
What are the "them" that were not put in at all?
When was the last time this plug was removed? I would suspect if it was in aircraft final assembly, the plane would have failed the high blow test. Often new aircraft are taking directly to a post delivery mod center for different STC installations. Those places wouldn't necessarily do a high blow test after the STC mods (if that happened). All speculation at this point.
@@chiphaynes6280 If the door/plug is in its place, I would surmise that it would actually pass an on-the-ground pressurization. The pressure itself would prevent it from moving upwards and out of its tracks. So if the bolts were not present, the door/plug could actually stay in place for a while... until vibration and airframe tortion would enventually nudge it out. Let's say, after a couple of months... ;)
I agree with you on the fact that there is a possibility that the finishing/mod center could be implicated in this though. Whoever touched it the last time for sure. But in this case, why would they actually open the insulation and remove the plug? Since it's a permanent plug option, insulation would have been installed over it at Boeing. Wouldn't it?
@@petep.2092 I am certain you are pointing out an error I made in English. As this is not my native tongue, you should point out what the mistake is. Otherwise this comment is of no value to me.
" I can easily imagine the end of the shift and the door has just been installed but the bolts not fitted yet. "
That would mean someone "bought off" the assembly steps without actually completing them.
If the crew showed up the next morning they would proceed to next actions only if the job was marked complete.
I believe the door plug has to move up to clear the roller pin not downwards as stated at 07:08. I could be wrong, I havnt worked on this particular plug door however in the closed position, the roller pin can't move down anymore.
I agree with you my understanding of the mechanism is that it should be lifted ( which would be safer as the weight of the panel adds to the integrity of the system ) but i am not a 737 specialist.
@@patpat5135looks that way to me also. Makes sense that the “LIFT assist springs” are there to help maintenance personnel lift the heavy door into the open configuration. Unfortunately, if the locking / arrestor bolts are not installed then the lift springs alone will probably eventually lift the door open after enough jostling around with plane turbulence.
@@nostromo526 the photo at 8:43 also seems to suggest the same. The roller pin looks to be already at the top of the guide and would prevent the door from being moved downwards, but maybe I'm completely misunderstaning something here.
@@nostromo526 turbulence and pressurization/depressurization cycles. They'll add to migration and potential premature wear in something really not designed to move in normal operation.
One remote possibilty that explains how it could have repeatedly flown with no bolts... If the lift assist springs carry only a percentage of the doors weight then the door will still remain locked in place at upper guide even without the bolts installed.
Until a 've g at the mid door occurs (pitch up rotation or turbulence etc) resulting in the door and its upper guides floating up off the fuselage frame guide rollers against friction at the stops. I think this is a remote possibility however because any pressure dif imparts huge loads at the stops.
Just listeed to latest NTSB briefing (which I assume you did to) and want to thank you again for these videos ecause they made me understand exactly what they were saying.
Glad to help
Great info as always, thx!
Hi Chris, those lockwires you refer to on the safetied nuts are called cotter pins. You had me thinking I'd forgotten what lockwire looks like, Lol!😂
Great explanation however, which, based on the lack of damage in general leads me to think somebody forgot to safety this door in place. That's quality control out the door for you. It's only going to get worse given how corporate thinks pilots and mechanics shouldn't even be near airplanes because it cuts into their profits. The more you know, the less you want to fly. After more than 45 years in what used to be my passion, you won't see me boarding anything anytime soon, but I'll hang on to the good times. Thanks for your videos.
I waas thinking that maybe they call them lock wire in England...... Likle french fries vs "chips" !
Just hope those good times are not the 1980s where there were between two and five times as many deaths in aviation, in spite of way less miles flown.
Lockwires are used elsewhere, but these are cotter pins. Lockwires are used to secure a whole bolt circle.
..or Split Pins?
Fantastic content. Media is so out of it still calling it a door or window.
To be fair it looks like a window in a door!
To be honest the Reddit comments aren’t any better, people just aren’t very knowledgable plane experts (only submarines).
Meanwhile we'll just go along with Boeing and call it a plug-type fitting when it's not actually a "plug" design.
Just brilliant. Thank you very much.
You're very welcome!
Great presentation.
Looks impossible for that “door” to move with those anchor and locking bolts in place. But it did, and that’s what’s both fascinating and troubling.
The locking nuts could have come loose if the locking pins were missing. Equally if the locking bolts were missing then catastrophic failure was almost inevitable. Even if the bolts are not found on the ground that does not mean they were not present. Hopefully inspection of the aircraft and plug door will shed some light on possible explanations.
I’d bet my next paycheck that the stop / arrestor bolts were not installed during final assembly.
Typical scenario would be something like this.
Day Shift finishes up and will no longer need the opening going forward. They assume Night Shift won’t need the opening any longer either so Day Shift installs the door plug engaged with the rollers / stop fittings but don’t install the stop / arrestor bolts “just in case” night shift needs to use the opening again. Night Shift comes in and says “wow, Day Shift finished up with the plug door” and proceeds to install the interior panels (without checking or installing the stop / arrestor bolts). Day Shift comes back in and sees the interior panels installed and says “great, Night Shift finished up with the plug door and even got the interior panels installed…now we can move on to a bunch of other stuff.” Late Friday afternoon rolls around and the supervisor is clearing out the stack of completed work packages piled on his desk and he isn’t quite sure from the work logs if the bolts were ever installed. He asks the Day Shift lead if the bolts were installed and that guy says “yeah, night shift finished installing the plug door”. Of course, the right thing to do is follow up with Night Shift on Monday night or maybe Tuesday morning during turnover but by the time that rolls around some other schedule crisis has come up to distract everyone and, voila, you have a door plug blowing off at 16,000 feet.
Ignoring the fact it requires or should require a sign off on a worksheet to say they have been installed. People are getting fired.
@@copperkipper1joe said that steve said he heard night shift verify the bolts were installed. Sign-off completed.
Great video series.
Thank you
Hi Chris,
I'm not connected to aviation on anyway shape or form. I saw one of your videos appear in my feed following the Alaska incident as I follow Maximus Aviation.
Anyway just wanted to say I've watched several of your videos now and absolutely love the content and presentation
Steve
@SteevioC Thanks Steve, much appreciated and thanks for watching.
Great vid, it seems almost like none of the locking bolts where installed. And the door was allowed to bounce on the lift assist springs overloading the roller pin connection, prop shearing the pin. For me, looking ant the mechanism it's seems the only way for it to fail so cleanly. Definitely looking out for the ntsb report.
Not even necessary to shear the guide rollers. If the lock / arrestor bolts were not installed, the door could work itself into the open position with enough jostling.
If no bolts were fitted, a hard landing would unlock the door and there is no physical way to check for this without disassembling the cabin interior panels. The “lift assist springs” are what holds the door closed and latched in the absence of the bolts.
The next flight the door would depart the aircraft as soon as sufficient pressure was applied.
As I understood the latest NTSB briefing, the roller pins (on frame) were in tact, but the corresponding guide tracks (on door) were sheared. These are “guide” devices and not structurally sufficient to hold the door in place.
The AL 1282 aircraft appears to have the hinge and lift assist spring assemblies still attached to the airframe. This seems to imply that the hinge guide fitting was ‘launched’ off of the hinge guide post. This would take it past the large washer and what appears to be two jam nuts at the top of the guide post. (Presumably to limit the door’s vertical travel when opened for inspections. Again, these are not structurally designed elements designed to retain the door during flight. A quick look at the remaining hinge assembly and guide posts would indicate the door plugs route of departure from guide posts.
@@allangibson8494 lift assist springs help with lifting the door when opening it. They don’t close the door.
WTF is a vid?
The fact that the two rows of seats were empty in an otherwise nearly full plane and the rumour that there has been pressurisation problems with this plane in the past raises a lot of suspicions.
That is exactly what I’ve been thinking @ 5 AM, Jan. 13. Maybe the noise was so annoying they had complaints. There will be a record.
Thank you for this excellent video. Like most ac engineers, we just wanted to understand the failure mode. Thank goodness no fatalities, by luck only.
Glad it was useful, thanks for watching
Great analysis.
Doing my airline columbo investigation, i dedooce that its highly likely that the lock bolts weren't refitted after routine servicing. Case solved.
Too early in the aircraft's life for a routine service. Besides, it is not a part of the aircraft that would need to be accessed during a routine service never mind being opened. Everything points to an assembly error at manufacture. You are a lousy detective (no offence intended)!
Thanks for your honesty, I shall now hand in my gold detective badge😢
@14:40 Fallout. Worth noting that Alaska had already returned eighteen Max9s to revenue service, and the FAA had to tell them to stop flying them. Also, Turkish Airlines flew their five Max9s all day on Saturday - including flights to Lyon, Bordeaux, Basel, Valencia and Malta - EASA seem to have been asleep on Friday/Saturday.
EASA doesn't regulate Turkish commercial airlines though.. So unless the EASA AD also blocked foreign companies flying in, the Turkish can keep flying with the instructions (or lack thereof) of their authority..
@@rkan2 as you say EASA could indeed have blocked all airlines from flying these planes into EASA territory, but failed to do so! must admit that I had presumed Turkey was a full EASA member (like Switzerland, Norway and Iceland)
The only way the door can move vertically is if all 4 bolts are missing. The load on these bolts are minimal based on the weight of tge door with the spring. Maybe each bolt has a load of 25-30lbs as tge 2 springs are supposed to lift tge door out and prevent it from falling back when the screws are removed. The door weighs 63 lbs so tge springs in total have to lift 63 lbs so tge springs would be maybe 4olb springs to help lift it. So there is no way the 4 screws were stressed. The 12 pins a d stoos on the side of fuselage and plug is what gets tge stress of pressurization of up to 22000 lbs at 36000 feet per ntsb or 5000 lbs at 16000 ft.
Assuming there were no screws the plug over time dislodged upward upon landing , maybe a hard jolt when the pla e was no longer pressurized and moved the pi s off tge stops so only a portion of tge pins were pressing against the stops and once tge plane pressurized and the load increased tge pins just slipped off the stops and then the plug flew away. That is my co cousin. The ntsb found no bolts. No way they were sheared. They just were not there. Either they were not installed or all 4 fell out. Even if there was o e bolt the door could not move vertically. Negligence.
Still an excellent video that answers so many of my questions. If this is a manufacturing oversight ref the four bolts, it is the sort of thing that can happen very easily in an assembly environment. Quality control should catch it, but.... As an aside. As an IBM engineer swapping logic cards to diagnose a computer error during a manufacturing test, I managed to leave the logic cards in another machine and the computer shipped minus 3 logic cards. Needless to say it did not work upon arrival at the customers site! My name was mud for several weeks, but it was not life threatening. I implemented an end of line quarantine area where not even the Line Engineer was allowed to borrow logic cards to diagnose a fault in another computer. I partly blamed the parts supply people as there was always a shortage of logic cards up to the day the computers were meant to ship. (JUST IN TIME or JUST TOO LATE.) maybe Boeing had a bolt or nut or split pin shortage on the line that day!
This is a speculative question more than a conclusion, but is the fact that there was zero damage to the fuselage somewhat indicative of completely missing bolts more than a gradual partial failure where one or more bolts fail at different intervals?
I think it's pretty safe to assume that the bolts were either left without the cotter pins in the nuts or not installed at all. Everything other than the guide channels on the doors were without damage consistent with something breaking off. There is a photo of the door hinges hanging out the side of the aircraft in perfect condition as if the door had just popped off
@@cheeseburger3209 good point no twisting no deformation etc indicating points of resistance etc makes sense
Absolutely great video! It's difficult to escape the conculsion that someone left the bolts off, but we shall see. I'm sure the door will be found, and that should give answers. I've just subscribed.
Thank you. I believe that the plug/door has already been found.
@@ChrisBrady737 don't see any news source on that during a quick search, but I'm always happy to wait for factual reporting over rumor based reporting, as our media when reporting rumors typically turn out a pig's breakfast for what otherwise would've been a straightforward story.
Hence, why I'll only occasionally check news updates on a developing story or investigation, waiting for the investigation before forming an opinion.
I hope so. @@ChrisBrady737
Key item in the determination of failure/fault .👍
Very informative. Thank you.
You are welcome, glad it was useful.
Great video! Made some timestamps:
00:00 - Introduction
00:29 - Details About the Plug Option and Securing the Door
02:02 - Plug Option Limitations
03:38 - Construction of the Plug Option
07:40 - Securing the Plug Option Door
11:47 - Alaska Airlines 1282 Incident
14:43 - Fallout from the Incident and Regulatory Response