Earlier quoted context omitted.
Correct, but I've seen a lot of confusion that its a systemic problem (ala MCAS) with the Max family. It doesn't look that way. It looks like a manufacturing problem on one particular variant.
The 8 had the great MCAS crashes (boeing solution ? tell the pilot to turn it off when it happens !), the 7 has anti icing that burnout the engine nacelle and make it fall (boeing solution ? being exempted from the certification requirement of your engines not falling off and we will fix it in a few years !), the 9 has doors that fall off (boeing doesn't even have a solution on that one, but they know others bolts ar…
United finds loose bolts on plug doors during 737 Max 9 inspections
361–370 of 773 posts
Re: United finds loose bolts on plug doors during 737 Max 9 inspections
#362Doesn’t this call into question the manufacturing of ALL 737 MAX’s including the 7 and 8 since they must use the same manufacturing process?
Only the max-9 has the door plug, the smaller airframes don't have that door, and the larger airframes always have the door fitted
It's not really about the door plug per se, it's about how Boeing's entire manufacturing, design and QA process could allow such an elementary mistake to escape notice in the first place.
If they got this wrong, what other bolts didn't they tighten properly? This question is especially relevant since just a few weeks ago, Boeing issued an airworthiness directive about loose bolts in the rudder system.
In any reasonable aerospace organization, the discovery of a systematic problem with the rudder system assembly should have prompted an audit of other processes. Why did that audit not uncover this issue with the plug door?
Presumably, the answer is that Boeing's processes are so incomplete or and/or unreliable so that, even when being given a hint at what kind of a problem to look for, they can't find other instances of the same problem themselves.
It raises the question of what other systems on the plane have problems, and whether Boeing is even capable of confidently answering this question at this point, or whether we just have to wait and see what other parts start falling off.
Re: United finds loose bolts on plug doors during 737 Max 9 inspections
#363Assuming that it's up to airline's employees (not Boeing) to remove/replace the panel/'plug as needed - and that 'loose bolts' means 'not properly torqued' rather than 'can't be', the logical conclusion is that the problem lies with the airline's employees (not Boeing). IOW, it's far too early to be speculating about blame.
Why would the airline need to remove/replace the plug? It doesn't appear to be the sort of thing that requires maintenance. They would have to remove the interior wall panels to inspect or work with the hardware involved.
In any case the aircraft is only a couple of months old, so it probably hasn't undergone any major work by the airline yet.
Arguably it should have, if the reports of pressurization warning lights are accurate and meaningful. But sadly, I can imagine them looking for a problem, not finding this one due to the need to take the whole plane apart ("Unable to replicate"), and concluding that the warnings were spurious.
Re: United finds loose bolts on plug doors during 737 Max 9 inspections
#364Literally just flew on a United Airlines 737 MAX 9 one week ago. It seems like the craft I flew on has probably been grounded in the week since. I noticed that we were flying on a MAX before boarding and nearly asked to switch flights, but consoled myself that I was being irrational and that the planes were almost certainly fine now. Guess my confidence was misplaced.
I mean, you're here now. Plane did its job. The safety margins on flying machines is really high, so while Boeing really should figure out what the hell is going on, the plane didn't fall out of the sky after a depressurization incident. It failed to a known state (ideally by design!)
That it didn’t fall out the sky is largely due to the door blowing off at a lower altitude by some fluke or miracle. Had this happened at cruising altitude we’d be telling a different story.
Re: United finds loose bolts on plug doors during 737 Max 9 inspections
#365https://www.youtube.com/watch?v=maLBGFYl9_o is a good video explaining how the bolts/doors etc are supposed to go together.
Very interesting video that shows a clear picture of how the plug is held in place. Some interesting spots in the video, 8:44 shows how the upper two locking bolts lock the roller pins into the upper door tracks, and 10:00 show the lower two locking bolts onto the sliding hinge posts. 13:10 shows how the door blew cleanly off, with very little damage to the roller pins and lower hinge posts. Some comments say the sam…
Shear forces on four bolts, isn't that the same thing that caused the disaster in that hotel with the suspended walkway in the 1980s? With more than a hundred deaths. Is this not a basic case in engineering school, like THERAC-25? Not a licensed PE.
Re: United finds loose bolts on plug doors during 737 Max 9 inspections
#366[deleted]
Re: United finds loose bolts on plug doors during 737 Max 9 inspections
#367Earlier quoted context omitted.
Does wiring bolts actually help? I feel like if a bolt is going to come loose enough such that the wire is all that is holding it in then you have a big problem already. The wire is just delaying the inevitable. A bolt is either fastened or it isn’t. If the wire is all that’s left to hold it, then it isn’t fastened and your parts are being held together with a very weak piece of wire.
> Does wiring bolts actually help? There's different kinds of bolts that get wired, with different kinds of goals and results. My only experience is wiring bolts according to the rules for club racing motorcycles. Some things, like oil sump drain bolts for example, wiring them will stop them backing out so far as to fall our, and while it will probably weep oil if it loosened enough to take ups the writing slack, it…
Happened to me once when I was racing an R6 6 years ago. I didn't torque the rear wheel nut, but had put my safety wire clip back through the axle so the nut couldn't back off. Got a warmup lap in and started in on a fast lap during a practice session, and it was immediately obvious something was wrong. Limped back into the pits and found the loose nut. I said a quick prayer to the wiring rulebook (and the people who crashed before that rulebook existed), and inspected everything on the bike.
Re: United finds loose bolts on plug doors during 737 Max 9 inspections
#368Earlier quoted context omitted.
Yes, this seems like a top to bottom culture rot problem at Boeing sacrificing quality control in exchange for reduced costs. A few years ago, I had read that certain airlines demanded planes manufacturered in Washington rather than South Carolina, and I wonder if that information actually ends up being a useful signal for better quality planes. https://www.postandcourier.com/business/airline-surveys-poin... https://…
I think the Max 9 are made in WA though, so it would be a much wider scale cultural problem than just SC's non-union vs. WA union factories.
They’re final-assembled in WA. The plug is installed by Spirit Aerosystems in Kansas.
Re: United finds loose bolts on plug doors during 737 Max 9 inspections
#369https://www.youtube.com/watch?v=maLBGFYl9_o is a good video explaining how the bolts/doors etc are supposed to go together.
Very interesting video that shows a clear picture of how the plug is held in place. Some interesting spots in the video, 8:44 shows how the upper two locking bolts lock the roller pins into the upper door tracks, and 10:00 show the lower two locking bolts onto the sliding hinge posts. 13:10 shows how the door blew cleanly off, with very little damage to the roller pins and lower hinge posts. Some comments say the sam…
Most of the pressure of the door should be supported by the stop pads, rather than the bolts. The force on the bolts should generally be from vibrations, not from pressure differential pushing the door out.
Re: United finds loose bolts on plug doors during 737 Max 9 inspections
#370Earlier quoted context omitted.
I mean, you're here now. Plane did its job. The safety margins on flying machines is really high, so while Boeing really should figure out what the hell is going on, the plane didn't fall out of the sky after a depressurization incident. It failed to a known state (ideally by design!)
That it didn’t fall out the sky is largely due to the door blowing off at a lower altitude by some fluke or miracle. Had this happened at cruising altitude we’d be telling a different story.
Pretty small potatoes compared to what https://en.wikipedia.org/wiki/Aloha_Airlines_Flight_243 survived. These things are actually pretty well built.