I found it interesting that Boeing did proactively tell airlines to inspect 737 MAXs for a possible loose bolt in a different part of the plane (rudder section) at least 8 days before the January 5th event. Example story: https://www.reuters.com/business/aerospace-defense/boeing-ur...
Unfortunately, Boeing did not know they had other issues with the plug door bolts.
Given everything I've seen so far, I'd bet good money that what happened here was miscommunication between Spirit and Boeing. Spirit started out locking down the plug, then Boeing asked them to just loosely attach it[1] so Boeing could yank the plug for interior/wiring/AC/paint, then someone at Boeing forgot about the "loosely". So now, they get in a hurry (maybe the AC/interior didn't need any access to work on, which makes sense for this MAX variant, it wouldn't need as many hatches to pull wire) and it went down the Renton line as if the plug was fully installed. It's enough to pass high blow inspection and other inspections, but then over time that "shipment config" attachment vibrated out, and pop goes the plug.
Almost certainly systemic issue though, so that sucks. Sucks real bad.
They need to get a Tiger Team or whatever together to look at everything with a shipment config, and make sure those "ship kits" don't leak into the real actual airplane configuration. This is . . ok, this is really manufacturing 101 stuff, but well, things happen.
I'm in the industry, but haven't touched the MAX, so take this with a grain of salt.
Bolts are most likely tightened with a torque wrench or a gun that is set to a torque spec. Over tightening a bolt is as bad as a loose bolt.
I speculate these passed QA from Boeing because they might have been correctly torqued to the spec. What happens in field is hard to understand. One possibility is vicinity to the engine can cause extreme vibrations, these can make them loose.
Other possibility is the maintenance side of things - maybe a badly calibrated torque wrench could be the reason.
Mechanical systems are not inherently immutable.
Nope. It is most probably caused by operational stress - rudder assembly is moving, fuselage is also working (compression and decompression cycles on take off and landing, thermal expansion and compression). I bet they don't just put red Loctite on it to keep it from getting loose. My bet is design flaws, not manufacturing or QA.
EDIT: I saw the pictures of bolts with pins and bolts without pins. The ones with pins cannot get loose, the others can. Let's see what happened.
They are not related. Probably different types of bolts, for sure different stress types. Rudder assembly is a moving part, these false door panels are not.
It's not a control surface, but it is a "moving part." That's what's baffling to me, that they spent a lot of effort building this hinge and pin roller system, and designed the door to hinge open up to 15 degrees.
It makes me wonder if there's maintenance procedures that at some point would require the operation of that door to successfully complete. Otherwise, the mechanism itself seems so incredibly overwrought, with lots of additional bolts, castle nuts, retaining pins, and even sprung hinges at the bottom.
Does anyone know why this "plug-type non-plug door" is built this way?
I recall a running joke from my childhood - from a former communist East European counry - about a certain car saying you should finish the assembly at home after purchase, tightening the screws before first use. Despite being a famously poor quality car - even in the sloppy East European practices - that supposed to be a joke not to follow suit!
I was responsible for safe for flight inspections on military aircraft and the photo included in that post is completely insane to me.
Those bolts being loose (and they are BIG bolts) would mean multiple people in the installation process didn’t do their jobs, and signed their life on the line saying they did.
When I did maintenance, there was someone (QA) there to witness every torqued bolt, inspect every safety wire and installed part.
Wby the rush to judgement ("The fish rots from the head."). What was done and not done will be traced and the causes determined with good old engineering and detective work. Responsibility will be revealed and the proper parties punished.
Rushing to judgement merely obscures the true responsibilities.
Looks like the installer did their job poorly and the QA rubber stamped it without checking.
Are the QAs required to make photos to prove that they did their job? Like those food delivery people.
From when I worked as an engineer on the assembly line for smaller jets, know that there would be a record trail of exactly who completed the work, who signed off on it and what the work order steps were for anything related to these assemblies and components. This would include the work done at Boeing and their suppliers. Will be interesting to ultimately hear the root cause here.
Don't they have many ways to prevent bolts from unscrewing? I know at least a few by doing mechanical stuff on motorcycles, and it seems that other planes don't have such problems (at least not within 2 months after the last inspection).
My understanding is that the bolts did have castle nuts and retaining wires in the design. So either they were incorrectly fitted, or the bolts themselves were under specified with regard to strength.
Every bolt you could see was checked before every flight yes. Every important bolt you couldn’t see during inspection was torqued, witnessed by QA, secured via safety wire or cotter pin, and secondary torque holding was then inspected by QA.
This thing is obviously not just an interior part, look at the meat in those castings, and it’s obviously safety critical, look at the cotter pins on other bolts. Sounds like it was going to be installed behind interior paneling and not inspected every day. For something like that, every important bolt should be secured by secondary methods, torqued and witnessed installed correctly. This looks like a failure in engineering (not having wire on this bolts), then a profound failure in assembly with multiple people not doing their jobs (not torquing, not witnessing, faking logs), risking the lives of passengers.
If this happened at cruising altitude and speed, people would have died. I can’t find the flight number but I believe 9 people died when a jet lost cabin pressure and a piece of the plane while decompressing during cruising altitude over water.
Bolts and machine screws are very interesting. One mistake I, an amateur bike mechanic, made for years was not greasing bolts properly before assembly.
It sounds counterintuitive but without grease a bolt (or machine screw) will bind early with a high torque well before it is correctly tensioned lengthways. The torque is just a proxy for the tension and it is this tension which is needed to fasten your components together as intended.
The grease means that when the torque to turn the bolt reaches the correct value then the bolt is also under the correct tension instead of being because it got stuck in the thread half way.
It's a complex topic. Depending on the design, lubrication may be required or forbidden. And if it's required, it should normally be on the threads only, under the head is usually forbidden.
And it's very important to understand that in most mechanical design with fasteners, the fasteners provide tension, and friction between 2 faces actually carries the load. Too little tension then fasteners can be sheared off. Too much, then the fasteners may not have remaining strength available for loads that act to add tension to the fasteners.
Using a torque wrench to reach target tension is normally only about +/-30% accurate. Usually design margin allows for this but in very critical applications where margin is not feasible, calibration is done on a sample of the same materials, etc, or a more direct measurement done. More direct measurement can mean hollow fasteners that allow you to measure the amount of stretch, use of ultrasonic measurement to measure stretch, washers with integrated strain gauges, or cleverly designed "tension indicating" washers or fasteners. There are many types so I just those keywords for anyone interested.
I am not saying that this design required such complex methods and sizing these fasteners should not be difficult. There is probably a mistake or lack of control in the assembly process.
Lots of good stuff in this comment but I'm confused about the +/- 30% accuracy quote, in my experience it is relatively easy to reach sub 10% accuracy based on comparing different (good quality) torque wrenches against each other and against a calibrated one.
Ive been working on cars and motorcycles and everything else other than airplanes for almost 25 years now, from motor swaps to transmission rebuild and custom suspension. The only time I ever use is a torque wrench is on engine internals, or smaller fancy areas into aluminum. Everything else, over the years, you learn by feel.
You pay attention to the size of the bolt, the material it's going into, and it's overall job. Yes you'll mess it up a few times a long the way. Hopefully you're a lot more careful when you see that the cost of making a mistake is a difficult extraction or alteration of some sort. Personally, I think you'll run into bolt/thread failure 10x more from improper insertion, dirty threads, corrosion, and overall entropy than you will from over torquing once you learn a few early lessons.
I've done countless brake jobs, tire rotations, oil changes, spark plugs, valve cover gaskets, shock and bushing changes, without a torque wrench. I've yet to ever had a problem from it after going a little too hard when I was 16 yrs old and learning what bolts and materials can hold what.
Torque specs only apply to clean and clear threads that are free of corrosion and grease -- unless otherwise-specified.
Threads that are this way do not get stuck half-way.
If the threads are already boogered up for whatever reason, then the torque specification is already wrong: The threads aren't clean, clear, and free of corrosion and grease. This can result in under-tensioned fasteners when using a torque wrench as a guide, since boogered threads (rather obviously) can present an impingement that allows a torque wrench to click off before proper tension is reached.
However, grease is not a magical antidote to this condition.
If the threads (boogered or not) are greased, then the torque spec is also wrong: Greased threads are also not clean and clear, and free of corrosion and grease. This can result in over-tensioned fasteners when using a torque wrench as a guide, since grease is (rather obviously) a lubricant -- allowing things to slide more-freely in a way that doesn't allow a torque wrench to click off until somewhere beyond ideal tension.
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So what do, then, as a home-gamer with a bicycle or maybe a car in the rust belt (but never an aircraft) full of dissimilar metals that are constantly rotting?
You could perhaps kit up to do the Junker test such as in DIN 65151, and make a study of how different greases affects things. You can even make a career out of publishing your studies.
Or: Just make sure the threads are clean, clear, and dry, and then assemble with an anti-seize paste which does not have lubricating qualities that affect final tension yield. (Permatex makes some, as do others.)
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(And in aircraft, always do what the engineers say. If the engineers are wrong, then: Stop doing whatever it is that you're doing, and consult them.)
I need manufacturers to give "frame spent 3 decades in the salt belt, questionable metal compatibility and won't be taken apart until it breaks again" torque specs.
It's like they think I'm going to take this thing apart and put it back together every year.
j/k, finding torque specs for a decades old steel bike is a lost cause
A properly designed service manual will specific if the fastener should be lubed. If it doesn't say lube/thread locker should be used, then the fastener should be torqued dry.
In some cases (some spark plugs are what I can think of) explicitly tell you NOT to grease them, as that will let you over-torque them and potentially damage threads (aluminum heads, steel plugs). So using grease is not always the recommended procedure.
However, the same photo shows other critical bolts that hold the whole hinge on the door are loose, and there’s not meant to be a pin on those.
I’m curious how the decision is made whether to include that pin in the design. Did they idiot-proof the maintenance of the plug, but not the initial installation?
> As part of the production process, Spirit builds fuselages for 737s and sends them by train with the special door assembly “semi-rigged,” one of the people said.
> “They are fitted but not completed," the person said.
> At its Renton, Washington, plant, Boeing typically removes the pop-out, or non-functioning, door and uses the gap to load interiors. Then, the part is put back and the installation in completed. Finally, the hull is pressurized to 150% to make sure everything is working correctly, the person said.
I can imagine a diffusion of responsibility as to whose job it is supposed to be to tighten those hinge bolts. Spirit is installing the plug in a “semi-rigged” state. Boeing is removing the plug to load the interior, then reinstalling it. I’d hazard a guess that Boeing is not removing the hinges, because the plug can be removed without doing so. What if, when reinstalling the plug, Boeing workers just redo the stuff they removed? They tighten the vertical movement arrestor bolt, put the pin through it, and believe they have done their job? If they never messed with those other hinge bolts, they don’t bother tightening them?
I’m no MBA or aerospace engineer, but why sub-contract the fuselage? I get subbing engines, since engine designs can be used on/adapted to other (possibly non-Boeing) airframes, hence opening up economies of scale, etc. But the fuselage is most of the plane by mass and integral to the design of everything else. If you don’t like making fuselages, maybe you should get out of the aircraft business. Was this just a union-busting thing?
"Loose bolts" is not a ton of detail. It could have nothing to do with any of the bolts discussed in that video.
I'm having a hard time imagining how this failure could occur from just those bolts "needing tightening". They are lock bolts with pins and appear to take shear forces and provide no clamping functionality. Even if the bolts were "loose", or not torqued to spec, how would they come all the way undone? Then the bolts, under shear, work their way out completely? And isn't the lift spring forcing the top pins into the upper part of the track? On top of that the curve of the track appears to be such that outward force on the door would actually cause the pins to go into the upper part of the track.
IDK, seems like there is something else going on. Different bolts maybe.
The bolts themselves don't take the entirety of the shear forces. They provide tension and therefore friction between the mounting surfaces which is where the shear is handled. By being loose, there is no friction to handle shear and also the item can gain additional momentum (more distance to travel) during shakes and impacts which might increase the impact force above the rated strengths strength.
I'm not an aerospace engineer, but it seems those hinge bolts might be better replaced with rivets --- if the hinge isn't frequently removed from the door.
Or it means the torque specs were a little too low, or too high and stripped, or the bolt threading was defective/spec’d wrong. Or bad metallurgy. Or the spec didn’t specify which order to tighten the bolts, so which direction you go causes different outcomes.
Lots of stuff is assembled consistently and carefully “wrong”, but as specified.
Well they left a ladder in the tail of a plane during assembly in the not distant past. It's not like just a couple screws or washers were left behind to rattle around.
An ex worked on a QA-type project related to production for them. It makes me wonder if some of the issues were more fundamental than that project could ever have addressed.
What's crazy to me is that these things do not roll of the factory line in large numbers. If it was a car plant or some other line where large numbers come off per shift, you could find that possibly one operator for one shift set their torque wrench to the wrong setting causing the finished items for that shift to be suspect. But seeing as not one plane rolls of the floor per shift, this is much more systemic like possibly the documentation was wrong or similar where it is persistently done incorrectly. Or maybe just the one plane for that one day that the worker incorrectly set their torque wrench that day.
When a junior software engineer drops a table in production, we don’t say the junior engineer was sloppy. We say the protections and process in place were bad.
I don’t like how the sentence in this parent comment blames individuals for process problems.
It's a cliche thing to say, but if it was a known issue and management papered over it - as the alternative is incompetent engineering instead of just cost-center-managed engineering - someone should go jail?
Nah. When you have an engineering culture problem, putting people in jail is not going to solve anything. It will scare employees, sure, but it won't fix your culture.
I believe someone at Boeing actually was criminally prosecuted in connection with the earlier MAX 8 problems, but, as in all these situations, it is seriously unlikely that that fixed any actual problems. Most likely, somebody felt they needed a neck to wring and found a convenient scapegoat.
I am curious why the door plug is not a plug door — that is, a design wherein the desired panel would be installed from the inside and sealed by the differential pressure, like a cabin door. This part looks more similar to cargo door; those usually have to open outward for space, but what is the design constraint for this case?
"I’ve been an aircraft technician for 23 years and we operate the Max9. I’ve opened and closed one of these plugs as well. Keep in mind that other 737 NG’s have these plugs installed in the longer fuselage models, not just the Max. They all work the same way and there’s never been an incident like this. I’m not saying this is what happened, but I can’t see how this could lug could come loose unless the two upper capture bolts, and the two lower bolts through the spring hinges weren’t installed. Even if a set of bolts, either uppers or lowers were missing with the opposites installed, I can’t see how the plug could come loose and depart the airframe. Just my ten cents. " - @jeffropenn
blancolirio is really great at explaining...mishaps. He provides details and an explanation of those details that's accessible. It's the first place I go to "find out what happened" for any kind of air incident.
Not just aviation and not just mishaps, but, almoshaps too!
I first started watching his channel during the Oroville dam crisis in 2017 and he had some excellent coverage of that event. He seems to cover "things which interest him" the venn diagram of which which overlaps with mine quite a lot.
Readit News
Unfortunately, Boeing did not know they had other issues with the plug door bolts.
Especially since most shops have pretty much tossed professional career QA out the window.
Almost certainly systemic issue though, so that sucks. Sucks real bad.
They need to get a Tiger Team or whatever together to look at everything with a shipment config, and make sure those "ship kits" don't leak into the real actual airplane configuration. This is . . ok, this is really manufacturing 101 stuff, but well, things happen.
I'm in the industry, but haven't touched the MAX, so take this with a grain of salt.
[1] Basically a "shipping" or train configuration
EDIT: I saw the pictures of bolts with pins and bolts without pins. The ones with pins cannot get loose, the others can. Let's see what happened.
Sure, it failed, and it isn't perfect.
But planes have had a long track record of being absurdly safe.
It's not a control surface, but it is a "moving part." That's what's baffling to me, that they spent a lot of effort building this hinge and pin roller system, and designed the door to hinge open up to 15 degrees.
It makes me wonder if there's maintenance procedures that at some point would require the operation of that door to successfully complete. Otherwise, the mechanism itself seems so incredibly overwrought, with lots of additional bolts, castle nuts, retaining pins, and even sprung hinges at the bottom.
Does anyone know why this "plug-type non-plug door" is built this way?
Those bolts being loose (and they are BIG bolts) would mean multiple people in the installation process didn’t do their jobs, and signed their life on the line saying they did.
When I did maintenance, there was someone (QA) there to witness every torqued bolt, inspect every safety wire and installed part.
There is something rotten in Boeing.
The same management that drove it to ground?
The fish rots from the head. And these constant problems sure do sound like a new company culture of cutting corners instead engineering first.
I've heard this since they killed hundreds of people in the two crashes. Why are they being protected? They have names.
Rushing to judgement merely obscures the true responsibilities.
Alternative is wrong bolts, or sabotage.
But more possible - one lazy QA ghosting.
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This thing is obviously not just an interior part, look at the meat in those castings, and it’s obviously safety critical, look at the cotter pins on other bolts. Sounds like it was going to be installed behind interior paneling and not inspected every day. For something like that, every important bolt should be secured by secondary methods, torqued and witnessed installed correctly. This looks like a failure in engineering (not having wire on this bolts), then a profound failure in assembly with multiple people not doing their jobs (not torquing, not witnessing, faking logs), risking the lives of passengers.
If this happened at cruising altitude and speed, people would have died. I can’t find the flight number but I believe 9 people died when a jet lost cabin pressure and a piece of the plane while decompressing during cruising altitude over water.
With a seperate follow through by another party to check the work.
That's SOP for US | AU | UK | EU military air mechanical crews.
Clearly this is hyperbole.
It sounds counterintuitive but without grease a bolt (or machine screw) will bind early with a high torque well before it is correctly tensioned lengthways. The torque is just a proxy for the tension and it is this tension which is needed to fasten your components together as intended.
The grease means that when the torque to turn the bolt reaches the correct value then the bolt is also under the correct tension instead of being because it got stuck in the thread half way.
And it's very important to understand that in most mechanical design with fasteners, the fasteners provide tension, and friction between 2 faces actually carries the load. Too little tension then fasteners can be sheared off. Too much, then the fasteners may not have remaining strength available for loads that act to add tension to the fasteners.
Using a torque wrench to reach target tension is normally only about +/-30% accurate. Usually design margin allows for this but in very critical applications where margin is not feasible, calibration is done on a sample of the same materials, etc, or a more direct measurement done. More direct measurement can mean hollow fasteners that allow you to measure the amount of stretch, use of ultrasonic measurement to measure stretch, washers with integrated strain gauges, or cleverly designed "tension indicating" washers or fasteners. There are many types so I just those keywords for anyone interested.
I am not saying that this design required such complex methods and sizing these fasteners should not be difficult. There is probably a mistake or lack of control in the assembly process.
Is there something I am missing here?
You pay attention to the size of the bolt, the material it's going into, and it's overall job. Yes you'll mess it up a few times a long the way. Hopefully you're a lot more careful when you see that the cost of making a mistake is a difficult extraction or alteration of some sort. Personally, I think you'll run into bolt/thread failure 10x more from improper insertion, dirty threads, corrosion, and overall entropy than you will from over torquing once you learn a few early lessons.
I've done countless brake jobs, tire rotations, oil changes, spark plugs, valve cover gaskets, shock and bushing changes, without a torque wrench. I've yet to ever had a problem from it after going a little too hard when I was 16 yrs old and learning what bolts and materials can hold what.
Threads that are this way do not get stuck half-way.
If the threads are already boogered up for whatever reason, then the torque specification is already wrong: The threads aren't clean, clear, and free of corrosion and grease. This can result in under-tensioned fasteners when using a torque wrench as a guide, since boogered threads (rather obviously) can present an impingement that allows a torque wrench to click off before proper tension is reached.
However, grease is not a magical antidote to this condition.
If the threads (boogered or not) are greased, then the torque spec is also wrong: Greased threads are also not clean and clear, and free of corrosion and grease. This can result in over-tensioned fasteners when using a torque wrench as a guide, since grease is (rather obviously) a lubricant -- allowing things to slide more-freely in a way that doesn't allow a torque wrench to click off until somewhere beyond ideal tension.
---
So what do, then, as a home-gamer with a bicycle or maybe a car in the rust belt (but never an aircraft) full of dissimilar metals that are constantly rotting?
You could perhaps kit up to do the Junker test such as in DIN 65151, and make a study of how different greases affects things. You can even make a career out of publishing your studies.
Or: Just make sure the threads are clean, clear, and dry, and then assemble with an anti-seize paste which does not have lubricating qualities that affect final tension yield. (Permatex makes some, as do others.)
---
(And in aircraft, always do what the engineers say. If the engineers are wrong, then: Stop doing whatever it is that you're doing, and consult them.)
It's like they think I'm going to take this thing apart and put it back together every year.
j/k, finding torque specs for a decades old steel bike is a lost cause
It’s also a magnetic one so I can stick it to stuff and it stays put.
Speaking from personal experience, this is also useful for brushing a robot's teeth.
There's another reason to grease them - the grease keeps the water out which prevents corrosion.
In working on my cars, I always use a bit of grease when assembling fasteners. I've never had one come loose, nor have any rusted themselves on.
Some of the bolts that would be loosened when the plug is opened during maintenance have a pin to prevent them from turning. That pin is present in this photo: https://x.com/byerussell/status/1744460136855294106?s=46&t=s...
However, the same photo shows other critical bolts that hold the whole hinge on the door are loose, and there’s not meant to be a pin on those.
I’m curious how the decision is made whether to include that pin in the design. Did they idiot-proof the maintenance of the plug, but not the initial installation?
Some quotes from this article: https://www.reuters.com/business/aerospace-defense/spirit-ae...
> As part of the production process, Spirit builds fuselages for 737s and sends them by train with the special door assembly “semi-rigged,” one of the people said.
> “They are fitted but not completed," the person said.
> At its Renton, Washington, plant, Boeing typically removes the pop-out, or non-functioning, door and uses the gap to load interiors. Then, the part is put back and the installation in completed. Finally, the hull is pressurized to 150% to make sure everything is working correctly, the person said.
I can imagine a diffusion of responsibility as to whose job it is supposed to be to tighten those hinge bolts. Spirit is installing the plug in a “semi-rigged” state. Boeing is removing the plug to load the interior, then reinstalling it. I’d hazard a guess that Boeing is not removing the hinges, because the plug can be removed without doing so. What if, when reinstalling the plug, Boeing workers just redo the stuff they removed? They tighten the vertical movement arrestor bolt, put the pin through it, and believe they have done their job? If they never messed with those other hinge bolts, they don’t bother tightening them?
https://en.wikipedia.org/wiki/Castellated_nut
https://en.wikipedia.org/wiki/Positive_locking_device
I'm having a hard time imagining how this failure could occur from just those bolts "needing tightening". They are lock bolts with pins and appear to take shear forces and provide no clamping functionality. Even if the bolts were "loose", or not torqued to spec, how would they come all the way undone? Then the bolts, under shear, work their way out completely? And isn't the lift spring forcing the top pins into the upper part of the track? On top of that the curve of the track appears to be such that outward force on the door would actually cause the pins to go into the upper part of the track.
IDK, seems like there is something else going on. Different bolts maybe.
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It means people were careless and sloppy during assembly.
Think of it like seeing "one cockroach in your kitchen." It's not one cockroach. You just haven't opened up the rest of the walls.
Lots of stuff is assembled consistently and carefully “wrong”, but as specified.
An ex worked on a QA-type project related to production for them. It makes me wonder if some of the issues were more fundamental than that project could ever have addressed.
https://www.nytimes.com/2019/06/28/business/boeing-787-dream...
I don’t like how the sentence in this parent comment blames individuals for process problems.
Maybe. Could also be incorrect torque specs, bad parts, unexpected vibration in that area, etc.
Edit: Yes, none of these are good either. Just saying there are many possibilities.
>> "Initial reports from our technicians indicate some loose hardware was visible on some aircraft."
Friendly reminder that 'some' can also mean most or all.
In aerospace this is dead people.
I believe someone at Boeing actually was criminally prosecuted in connection with the earlier MAX 8 problems, but, as in all these situations, it is seriously unlikely that that fixed any actual problems. Most likely, somebody felt they needed a neck to wring and found a convenient scapegoat.
The presenter is a 777 pilot and A&P mechanic. Released 2hrs ago.
https://www.youtube.com/watch?v=WhfK9jlZK1o [13:43]
"I’ve been an aircraft technician for 23 years and we operate the Max9. I’ve opened and closed one of these plugs as well. Keep in mind that other 737 NG’s have these plugs installed in the longer fuselage models, not just the Max. They all work the same way and there’s never been an incident like this. I’m not saying this is what happened, but I can’t see how this could lug could come loose unless the two upper capture bolts, and the two lower bolts through the spring hinges weren’t installed. Even if a set of bolts, either uppers or lowers were missing with the opposites installed, I can’t see how the plug could come loose and depart the airframe. Just my ten cents. " - @jeffropenn
I first started watching his channel during the Oroville dam crisis in 2017 and he had some excellent coverage of that event. He seems to cover "things which interest him" the venn diagram of which which overlaps with mine quite a lot.
https://www.bloomberg.com/opinion/articles/2024-01-08/alaska...
Fortunately, most airlines in my country use Airbus planes.
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