I just have a quick question if you see this jb747, I understand that you are saying that leaking doors are extremely noticeable and noisy but my question is - what if the failed seal plug is hidden behind interior panels and insulation? I understand that traditional doors and emergency windows would have a well-understood history and typical documented modes of failure (when they do happen) but this particular plug is a bit more hidden than usual.
I don't know that door plugs are in themselves unusual, though I've never come across one. But, for an aircraft to leak enough air to actually be noticeable to the system, then it would have to be a pretty horrendous leak. Aircraft leak like sieves anyway, and the only reason they stay pressurised is that air is pumped in to replace what is lost. If you turn the packs off at altitude, you'd better not waste any time heading down, as the cabin will start climbing immediately. Not super rapidly, but enough to catch you if you were silly enough to test this out. So, even though there was paneling around the door, you'd expect all of the cracks and various openings to have their own little howl to add to the cacophony.
Plus I doubt that his was a gradual failure. It would have been closed, until suddenly it managed to move enough to clear the tabs, at which point the rest of the sequence would be over in less than a second.
These plugs seem to be the worst of all options, in this particular B737-Max9 model, the selection of this plug option has all the drawbacks of a novel and new point of failure in manufacturing and fatigue, it costs a bomb to reactivate as an active/useable emergency door as per the warnings from Boeing, and thus prevents future owners from going to a higher density seating arrangement, so presumes that Alaska intended to own and operate these aircraft without regard to resale value.
Actually I can't see why it costs a bomb, other than Boeing wanting it to. The door frame is there, as is the surrounding structure. Looks like a DIY job for a couple of pilots over the weekend. I'll bet any associated wiring is also there, just not connected. I don't know how the slides are handled for these doors, but presumably the storage area is still there, or is part of the door.
I don't think they'll ever find those missing bolts from that Alaskan flight so the question will remain about whether the bolts were even installed, or installed incorrectly, or there is some other flaw in that particular plug assembly.
If the bolts were installed, there will be some form of witness marks on the inside of the bolt holes. And as they won't all have undone themselves at the same time, presumably some would have ripped out if even partially done up. I'd expect they're still at the Spirit factory though.
Don't they regularly use Speedtape?
No MBA would sign off on that much Speedtape. It would be cheaper to fix the aircraft. But, they may have progressed to duct tape. Looks the same, so it must be just as good.
NOTE: Plug type doors, and door plugs, are not the same thing. These plugs are, to a degree, held in by internal pressure, but it's a big stretch to call them any sort of plug door.
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