Come on, Boeing.

[Bravo52]

Surely this has to be the last major problem for the 737 Max? If there is another fatal accident with the Max and it is shown to be a design flaw or manufacturing defect, methinks that is the end of the Max.

Anyway, all of this should prove to Boeing that it is time to get the “Future Single Aisle” (FSA) aircraft development going.

This is not a design flaw. It is likely a maintenance failure. Huge difference. However, to your point about "issues" associated with the 737 Max, no, it won't even be close to the "end of the Max". While the design of the 737 isn't perfect, it is the best in the world at the moment...and...for the foreseeable future for what it does. People will argue the Scarebus A320 is better but they don't qualify that with any reasonable comparison. It comes down to what I like.

 

[watheyak]

4 bolts? Are there other mechanical devices that hold the door in besides all of the load being on 4 bolts? I'm estimating nearly 10,000# acting on the door which is easy enough for 4 bolts to resist.

Boeing jokes are starting:

View attachment 623971View attachment 623972

Yes. Way more than 4 bolts as pointed out many times with many nice illustrations in this thread.

And as BEC explained, this arrangement has worked flawlessly for hundreds of thousands of flight hours since 2006. When assembled correctly.

 

[smstachwick]

4 bolts? Are there other mechanical devices that hold the door in besides all of the load being on 4 bolts? I'm estimating nearly 10,000# acting on the door which is easy enough for 4 bolts to resist.

Boeing jokes are starting:

View attachment 623971View attachment 623972

Somebody has been having a little too much fun with DeepAI.

 

[BEC]

4 bolts? Are there other mechanical devices that hold the door in besides all of the load being on 4 bolts? I'm estimating nearly 10,000# acting on the door which is easy enough for 4 bolts to resist.

*sigh*. Look at the picture you posted here: #239 Twelve stop pads and twelve stop fittings which are pressed together when the door is in place. Pressurization forces hold them against one another more tightly.

The four bolts just keep it from moving up so that the stop fittings clear the stop pads and allow the door/plug to go out of the opening.

You can see the stop fittings against the stop pads in the picture I posted highlighting three of the four bolts.

 

[StreuB1]

To everyone talking about the bolts with the castellated nuts.

Those bolts are not load bearing. They are travel inhibitors. The bolts on the lower spring hinge assy's are overtravel inhibitors, so the springs do not eject the hinge itself. The upper bolts are to prevent the pins from moving out of the cam sockets. The upper pin and sockets are the main load bearing components and the bolts simply disallow the cams to reverse their over-center motion. The sprung lower hinge pawls press the pins into the cam sockets and that in turn presses the doors buffer locators into the buffer landing sockets. These all then align and register the door as well as provide 2D stability in the curved plane of the door.

The load bearing components in the assy are the lower hinge socket in the fuselages lower door jamb and the associated hinge pawl, the upper cam pins and cam sockets, and the (12) buffer points (locators and their landing sockets).

 

[BEC]

To everyone talking about the bolts with the castellated nuts.

Those bolts are not load bearing. They are travel inhibitors. The bolts on the lower spring hinge assy's are overtravel inhibitors, so the springs do not eject the hinge itself. The upper bolts are to prevent the pins from moving out of the cam sockets. The upper pin and sockets are the main load bearing components and the bolts simply disallow the cams to reverse their over-center motion.

The load bearing components in the assy are the lower hinge socket in the fuselages lower door jam and the associated hinge pawl, the upper cam pins and cam sockets, and the (12) buffer points (locators and their landing sockets).

Thanks for that. You added the other load bearing points besides the stops, which I, in my irritation at the question — again — didn't cover.

 

[smstachwick]

*sigh*. Look at the picture you posted here: #239 Twelve stop pads and twelve stop fittings which are pressed together when the door is in place. Pressurization forces hold them against one another more tightly.

The four bolts just keep it from moving up so that the stop fittings clear the stop pads and allow the door/plug to go out of the opening.

You can see the stop fittings against the stop pads in the picture I posted highlighting three of the four bolts.

I admit that I’ve found some of the diagrams a bit hard to follow sometimes, either because of my lack of experience handling the minutiae of such systems or because of the fact that I’m looking on a phone screen. Take your pick.

But I’m understanding that the normal door would swing out and down like the airstairs on a lot of regional jets, right? And the plug installed for Alaska would be bolted or pinned both within the hinge and around the edge of the door, right?

Some more stuff I couldn’t make a good guess at: Would an actual door have to pop inward first like the main exit does? Are they thinking that the plug somehow managed to do this as well?

I feel like a .gif animation might be useful, I wonder if anyone is working on something like that.

 

[BEC]

Either the plug or a real door has to rise up off the stops, assisted by the springs at the bottom. The upper guide tracks on the door and the pins on the door frames also guide the top of it outboard a bit at the same time. The upper bolts in question prevent that from happening while the lower ones essentially block the action of the assist springs.

If it's a real door, it also has a pressure relief vent that is opened when the handle is pulled. It does not have to come in like main exit/galley service doors do. Its action is more like the those of the overwing exits on 737s from the -700 onwards, which tip in then go out through the opening when their handle is pulled.

Yes, it is hinged at the bottom like an airstairs. The four bolts just prevent its upward/outboard at the top motion, so the 12 stops hold it from moving out.

An animation would be helpful in understanding this.

 

[Blast it Tom!]

Yes, it is hinged at the bottom like an airstairs. The four bolts just prevent its upward/outboard at the top motion, so the 12 stops hold it from moving out.

An animation would be helpful in understanding this.

Well, I just got flummoxed again. I've been trying to follow fairly silently, but with the diagrams presented, I really thought that since those 12 stops encroached the opening, were therefore a rest to keep it from moving further inward, i.e "if you sit on these, you'll be flush with the fuselage OD." So the 4 bolts were apparently missing (I may be wrong, I thought that's the current description), and these stops simply fractured, allowing the door to go it's merry way? Or can the plug, once it moves up, get past the stops? I'll see if I can see the stops in the pics from 'way back...

ETA: Yes, you can see the stops still present around the plug opening, so it must be my second option above, now in italics...

 

[BEC]

Well, I just got flummoxed again. I've been trying to follow fairly silently, but with the diagrams presented, I really thought that since those 12 stops encroached the opening, were therefore a rest to keep it from moving further inward, i.e "if you sit on these, you'll be flush with the fuselage OD." So the 4 bolts were apparently missing (I may be wrong, I thought that's the current description), and these stops simply fractured, allowing the door to go it's merry way? Or can the plug, once it moves up, get past the stops? I'll see if I can see the stops in the pics from 'way back...

ETA: Yes, you can see the stops still present around the plug opening, so it must be my second option above, now in italics...

Correct. The plug/door has to rise about 1 1/2 inches so that the stop fittings on the door go above the stop pads in the door surround on the fuselage. If it can't do that, it doesn't go out. The bolts in question restrain that upward (and a bit outward at the top) motion.

 

[brockrwood]

However, to your point about "issues" associated with the 737 Max, no, it won't even be close to the "end of the Max".

I was saying that another accident of the Max, causing fatalities, and having the accident be caused by a flaw or defect in the plane that also applies to other Maxes, might so undermine the public’s confidence in the airplane that no one will be willing to fly on one. Wouldn’t that be doom for 737 Max model of aircraft?

 

[bjphoenix]

Yes. Way more than 4 bolts as pointed out many times with many nice illustrations in this thread.

Well I thought there were up to 12 bolts. It was post #249 that said 4 bolts.

Stop pads, cams, things sliding up and down, somebody is making this more difficult than it needs to be.

 

[StreuB1]

Well I thought there were up to 12 bolts. It was post #249 that said 4 bolts.

Stop pads, cams, things sliding up and down, somebody is making this more difficult than it needs to be.

It is actually a very simple solution to hold a very critical component under enormous stress, in place.

 

[bjphoenix]

It is actually a very simple solution to hold a very critical component under enormous stress, in place.

Not having seen it in person I can't comment further but should I point out that we have evidence of one time the solution didn't work? From the description I'm picturing a mechanism similar to the little battery door on the back of my TV remote control.

 

[brockrwood]

It is actually a very simple solution to hold a very critical component under enormous stress, in place.

Ok, here is a question from the philosophy major: Why not make the door plug fit into the door frame so that the only way it can come out of the door frame is by going BACKWARDS into the inside of the airplane? Some sort of flange on the edges of the plug that fits into door frame would work. Even if the bolts holding the door plug place come loose, the pressure inside the cabin holds it against the inside of the fuselage.

In fact, why aren’t ALL of the openings on all airplanes designed that way?

 

[rocketaholic]

That plane was brand new. You really look like the gang who can't shoot straight these days.

It will be interesting. Only came into distribution as of November 2023. 177 aircraft will need to be inspected and all documentation, safety checks CDRs etc etc etc.........

 

[Bravo52]

I was saying that another accident of the Max, causing fatalities, and having the accident be caused by a flaw or defect in the plane that also applies to other Maxes, might so undermine the public’s confidence in the airplane that no one will be willing to fly on one. Wouldn’t that be doom for 737 Max model of aircraft?

No.

The design is too good.

 

[bjphoenix]

https://www.aerotime.aero/articles/...ged-on-alaska-plane-door-plug-causing-blowout

 

[Sooner Boomer]

In fact, why aren’t ALL of the openings on all airplanes designed that way?

Because in an emergency evacuation, you want things to go *out* of the plane, not in. Pulling the door into the interior of the plane would cause a lot of problems.

 

[Sooner Boomer]

Maybe this will help...





The upper guide roller is part of the frame; the upper guide track fitting is part of the door. The locking bolt (with castellated nut and cotter pin) keep the door plug from moving up. The springs on the lower hinge cause the door to press against this bolt, helping reduce rattle.

Here's the bottom of the door plug...



The hinge guide fitting is part of the door. The black cylinder is the hinge mount shaft. Again, there is a bolt that goes through this assembly (all the way through the hinge guide fitting) that limits vertical travel. The bolt has a castle nut/cotter pin.

These are the four bolts that keep the door from moving upwards.

There are tabs on the door. There are matching tabs on the frame. If you tried to just swing the door shut (pivoting on the lower hinges), the door wouldn't close because it would hit the tabs on the frame. To open/close the door, it has to be lifted up so that the tabs on the door can slip past the tabs on the frame. Once the door is closed, pressure in the cabin helps press the door tabs against the frame tabs. Sorry, no good diagram/pic.

 

[smstachwick]

I was saying that another accident of the Max, causing fatalities, and having the accident be caused by a flaw or defect in the plane that also applies to other Maxes, might so undermine the public’s confidence in the airplane that no one will be willing to fly on one. Wouldn’t that be doom for 737 Max model of aircraft?

Most of the public doesn’t know a damn thing about airplanes and can’t correctly identify a type. Most also don’t know that they can check their aircraft type when buying a ticket. Heck, a lot of news organizations reporting on incidents fail to get the aircraft type correct in accompanying images, often just settling for one of the same airline.

This is why we have the airworthiness standards that we do, so the public doesn’t have to dig around and do all that research to get on a safe aircraft type. The fact that it has come to that for some is evidence of systemic failure.

 

[OverTheTop]

The NTSB said both guide tracks were fractured.

 

[Grog6]

The helium filled room I walked into was the MR room in a r&d group I worked for. Someone saw a helium dewar had vapor coming out, and closed the vent valve, leading to failure of the dewar, which dumped 250 gallons of helium into the room. I just happened to walk in there to check a piece of equipment.

 

[vcp]

Details!? Where did you find a helium filled room!?

Que Safety Nazi vacuum chamber story: https://www.sciforums.com/threads/vacuum-pockets-and-safety-nazis.41446/

 

[NTP2]

Que Safety Nazi vacuum chamber story: https://www.sciforums.com/threads/vacuum-pockets-and-safety-nazis.41446/

Well now I have even more questions!

 

[Ron Soto]

Boeing's Fix..

 

[Antares JS]

In fact, why aren’t ALL of the openings on all airplanes designed that way?

Because Apollo 1.

 

[Antares JS]

Well now I have even more questions!

The answer to most of which is "bureaucrats are dumb."

 

[Blast it Tom!]

The answer to most of which is "bureaucrats are dumb."

Sad but true, in a strange way. I don't think individuals start out that way. But I have one of those "demotivational" posters titled "Meetings", with the explanation, "None of us is as dumb as all of us."

 

[Blast it Tom!]

The NTSB said both guide tracks were fractured.

Now it gets interesting. You figure SOMETHING had to break in order for the plug to leave - it's hinged at the bottom, so what else broke?

ETA, dang I hate being in a hurry all the time... likely the plug, where it is attached to the hinges, simply ripped away once it got onto the free stream air....