The Boeing 737 thread redux.

[ZRX61]

[Horse]

Looks to be held in by a dozen or so M8s.

[Skub]

[wull]

Door found in garden, 2 lost phones found as well

Whilst we’re all still searching the garage for that 10mm socket

[Mr. Dazzle]

Just hope one of them wasn't a Nokia 3210, you wouldn't one of them coming down like a meteor.

[wull]

Just hope one of them wasn't a Nokia 3210, you wouldn't one of them coming down like a meteor.

[JackyJoll]

Looks to be held in by a dozen or so M8s.

Time was, we could depend on our mates!

[Horse]

https://www.bbc.co.uk/news/world-us-canada-67919436

Bolts in need of "additional tightening" have been found during inspections of Boeing 737 Max 9s, United Airlines has said.

Inspections began after a section of the fuselage fell from an Alaska Airlines 737 Max 9 on Friday.

United Airlines said "installation issues" relating to door plugs would be "remedied" before the aircraft type would return to service.

Some 171 planes of the same type remain grounded by the US regulator.

In its statement, United said: "Since we began preliminary inspections on Saturday, we have found instances that appear to relate to installation issues in the door plug - for example, bolts that needed additional tightening."

[mangocrazy]

"Since we began preliminary inspections on Saturday, we have found installation issues in the door plug - for example, bolts that needed additional tightening."

That is scary A F. Loose bolts in a door plug? Scarcely believable.

[wull]

What concerns me is the Alaska airlines plane had 3 separate instances of a pressurisation warning going off hence the restriction of flight over water yet they never managed to find the fault, the culprit.

I’m guessing they performed a pressurisation test which would have helped them pin point where it was, you’d also think their attention would be drawn to the door plugs and at least check the door fixings, which they would have found were loose like the UA 737.

With it being relatively new, a few months old it’s clear it’s been a case of poor installation, bolts not tightened to spec and possibly a poor job of lock wire installation or whatever fail safe measures that are in place.

[Horse]

"Since we began preliminary inspections on Saturday, we have found installation issues in the door plug - for example, bolts that needed additional tightening."

That is scary A F. Loose bolts in a door plug? Scarcely believable.

Scarcely? Try this:

https://www.bbc.co.uk/news/world-us-canada-67919436

Bolts in need of "additional tightening" have been found during inspections of Boeing 737 Max 9s, United Airlines has said.

United Airlines said "installation issues" relating to door plugs would be "remedied" before the aircraft type would return to service.

Inspections began after a section of the fuselage fell from an Alaska Airlines 737 Max 9 on Friday.

Alaska Airlines says it has since found "some loose hardware" on some Max 9s.

[Mr. Dazzle]

So far as I can work out the bolts don't directly hold the door plug in. They hold it in the right place and a set of seats/pads bear the actual loads.

Still...bolts kinda need to be done up right?

Far from the first time this sort of thing has happened, and far from being a Boeing issue specifically. The most famous case being that BA windscreen, which is one of the classic school room examples in this area.

I suggest those of a nervous disposition don't think too hard about how you know if a bolt is done up You basically don't, the best you can ever get to robustly is that it's probably still tight

[Horse]

The most famous case being that BA windscreen, which is one of the classic school room examples in this area.
robustly is that it's probably still tight

As mentioned earlier, incorrect undersized bolts were used.

[Mr. Dazzle]

The most famous case being that BA windscreen, which is one of the classic school room examples in this area.
robustly is that it's probably still tight

As mentioned earlier, incorrect undersized bolts were used.

Yes, and demonstrably there was ultimately nothing to stop that happening. Lots of things which were supposed to stop it, but in the end they all failed. The swiss cheese lined up.

That's why it's a classic case study you get taught.

[Horse]

The most famous case being that BA windscreen, which is one of the classic school room examples in this area.
robustly is that it's probably still tight

As mentioned earlier, incorrect undersized bolts were used.

Yes, and demonstrably there was ultimately nothing to stop that happening. Lots of things which were supposed to stop it, but in the end they all failed. The swiss cheese lined up.

That's why it's a classic case study you get taught.

And the final slab of no-holes cheese would be to have a window fitted from the inside.

[Mr. Dazzle]

In that particular case the dashboard was in the way

It's the same with these 737 'doors'. Ultimately the preferred design would be one it's impossible to open, but then it wouldn't be able to operate an emergency escape hatch in the versions which use it as such. The preferred design would actually be "just don't have the hole on planes without that exit", but that'd cost more and airlines might want to change their mind later.

[Mussels]

As mentioned earlier, incorrect undersized bolts were used.

Yes, and demonstrably there was ultimately nothing to stop that happening. Lots of things which were supposed to stop it, but in the end they all failed. The swiss cheese lined up.

That's why it's a classic case study you get taught.

And the final slab of no-holes cheese would be to have a window fitted from the inside.

If a plane windscreen is going to detatch would it be better if it blows inward or outward?

[Mr. Dazzle]

Yes, and demonstrably there was ultimately nothing to stop that happening. Lots of things which were supposed to stop it, but in the end they all failed. The swiss cheese lined up.

That's why it's a classic case study you get taught.

And the final slab of no-holes cheese would be to have a window fitted from the inside.

If a plane windscreen is going to detatch would it be better if it blows inward or outward?

Pretty much anything on an airliner at altitude is gonna blow outwards, regardless of which way you'd prefer Air pressure inside is way higher than outside because the plane is err...pressurised. That's why wherever possible all the doors and windows are fitted from the inside, so they're forced into their frames and you don't need anything else to hold them in place.

There are exceptions of course, as we've now seen!

[Mussels]

And the final slab of no-holes cheese would be to have a window fitted from the inside.

If a plane windscreen is going to detatch would it be better if it blows inward or outward?

Pretty much anything on an airliner at altitude is gonna blow outwards, regardless of which way you'd prefer Air pressure inside is way higher than outside because the plane is err...pressurised. That's why wherever possible all the doors and windows are fitted from the inside, so they're forced into their frames and you don't need anything else to hold them in place.

There are exceptions of course, as we've now seen!

Is the pressure always going to be higher inside, on a windscreen during takeoff and landing?

[Mr. Dazzle]

No, but the forces associated with that are generally lower (excluding encounters with rogue pigeons). The internal pressurisation is generally the sizing case.