Alaska Airlines flight forced to make an emergency landing... 82

[SWComposites]

engines - once again you demonstrate your ignorance. There is nothing to indicate a material problem. Nothing. As far as materials these doors are essentially the same as 10’s of thousands successfully flying every day.

 

[waross]

Those springs on the hinges are to hold the door up when it is open or about to be opened.
If the door slid downwards when it was open, then it wouldn't close.
The stop pins would impact in front of the stop pads instead of behind them.
That said, the springs must be strong enough to support the weight of the plug, and probably strong enough to support the weight of a functional door.
Ther must have been some friction holding the door down in the closed position.
Absence friction the springs would have lifted and disengaged the door.
I surmise that vibration on the ground when the internal and external pressures were equal may have allowed the springs to slowly work the door upwards until the stop pins were just clear of the stop pads but the top guide was still engaged.
The differential pressure at 16,000 ft alt then fractured the still partially engaged upper guides.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[TugboatEng]

, an Apple iPhone was found which appears to have fallen from the plane and not only did it appear to be undamaged, is was still fully functional

I imagine the terminal velocity of a modern cell phone is quite low. A brush with a tree leafy branch (this was Oregon) on the way down can only help.

 

[Alistair_Heaton]

the hull is pressurised to -500ft as soon as the doors are shut and the engines are started.

 

[jrs87]

Quoting waross

waross, how do you feel about these comments?

Those springs on the hinges are to hold the door up when it is open or about to be opened.
If the door slid downwards when it was open, then it wouldn't close.
The stop pins would impact in front of the stop pads instead of behind them.
That said, the springs must be strong enough to support the weight of the plug, and probably strong enough to support the weight of a functional door. Perhaps counterbalance like garage door or double hung window, spring holds it were other force puts it.
There must have been some friction holding the door down in the closed position.
The spring is basically neutral when the door is closed
Absence friction the springs would have lifted and disengaged the door.
I surmise that vibration on the ground when the internal and external pressures were equal may have allowed the springs to slowly work the door upwards until the stop pins were just clear of the stop pads, but the top guide was still engaged. The aircraft left the factory with the track lock bolts not installed but with the plug set but not fixed in the down position.
The differential pressure at 16,000 ft alt then fractured the still partially engaged upper guides. 14,000 feet, climbed after rapid decompression another 2,000 feet before diving. Fractured guide as last failure point is plausible.

 

[Alistair_Heaton]

The root cause is the restraint bolts were not fitted to stop movement.

The failure mode after that is interesting but not really relevant.

There should be a paper work trail with duplicate signatures whenever the doors are closed. If that paper work doesn't exist then a cert of Airworthiness shouldn't have been issued.

We see it in the techlog when the technicians open the normal emergency exits. One stating they were open and another entry saying they were closed. Which I might add we have sensors on and will trigger a caution in the front if they are not "green" we don't see them on the door synoptic page normally unless they are open.

I believe during a C check the job cards have all these signatures and listings. And the CAMO ensures that its all done and signed off before issuing the certificate of Airworthiness.

 

[Alistair_Heaton]

As an aside the communications are doing the rounds.

Pretty horrible and dirty on both sides.

https://www.youtube.com/watch?v=SEh71lT08hI

 

[LittleInch]

I was thinking when they released the original pilot transcript that it was soumding rather "informal".

Did no one ask or state they were squawking 7700?

Or use the words mayday? Or even panpan?

I though everyone used FL 100, not ten thousand feet??

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Alistair_Heaton]

Transition altitude in the USA is 18000ft before you set 1013 so its normal for them.

By the sounds of it they were struggling with the stabilisation to get it in.

Personally a big bang like that rapid depressurisation I would be doing a compromised airframe decent and approach so the speed would be back at 210knts. Early gear down in case there is issues with that. They were loaded with fuel so its not as if that was an issue taking drag hit and fuel burn. In fact getting rid of it is a bonus.

On a mayday the pilot dictates the requirements so you just tell them your required track miles and they will give it. To be fair the controller was giving hints that it was available and maybe they should.

 

[LionelHutz]

The aircraft left the factory with the track lock bolts not installed but with the plug set but not fixed in the down position.

That's been determined and reported already? I've only heard that they have yet to be recovered.

 

[Murph 9000]

It remains to be 100% confirmed, but NTSB have already said that they believe the incident was caused by the plug moving vertically up off the stop pads, allowing it to open as designed. The fractured guide fittings are an obvious consequence of it opening while under pressure. The only way that should be possible is with all 4 locking/retaining bolts missing. There shouldn't be enough force available to shear those bolts, even if there was just one present, and it seems unlikely that fatigue would be an issue due to the age of the aircraft. They have the plug, so they can say with a high degree of confidence that the stop pads (on the frame attached to the hull) and stop fittings (on the plug) didn't fail.

It's now more a case of trying to figure out if the bolts were ever fitted, who failed to fit them the last time the plug was closed, and why they failed to fit them. There's a small chance they might have been improperly fitted, but just missing seems quite likely. There's a secondary question about why different bolts that hold some of the fittings to the plug have been found loose on other MAX 9s, but it doesn't look like those other bolts being loose would cause the plug to exit stage left; that's just some other shoddy workmanship that has been discovered in the same area.

 

[LittleInch]

You wonder then if the door had moved a little bit, enough to cause a small leak at the base or top of the door, but not enough to detach itself from the stop pins.

I'm not surprised they've come to that conclusion as it looks like an almost perfect door opening operation, just when it wasn't supposed to.

Those locking/retaining bolts though are pretty small, easily misplaced and not exactly super obvious. No Red paint or warning notice e.g. "BOLT HERE when closed". Will be interesting to see if its even on the checklist.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Alistair_Heaton]

Just a pic how the Canadians do it

 

[LionelHutz]

It certainly does appear that at least some of the bolts were missing. However, they're still looking for one of the lower hinge pieces that is bolted to the plug and the spring that pushes it up. In the pictures posted above, the other one is visible still on the airframe and not attached to the plug. So, the failure likely is not as simple as the bolts being missing and the plug popping out of the airframe. The fix won't be as simple as checking that the 4 bolts are installed either.

In the end though, it squarely points to Boeing having serious QC problems.

 

[SWComposites]

No, it appears quite simple that the 4 restraining bolts were missing and this allowed the door to open. There is no other plausible cause at this time (though we might yet be surprised). Once the door opened, it swung down on the hinges, as it is designed to do. But it is now in the airstream, so it likely tore off part of one or both hinges as it departed the aircraft.

Yes, a significant quality escape somewhere. As is the number of other loose bolts found in the door structure. See:

https://www.democracynow.org/2024/1/9/boeing_warning_signs

https://www.msn.com/en-us/money/com...-claims/ar-AA1mHUWE?ocid=finance-verthp-feeds

 

[LionelHutz]

It's already been PROVEN by inspection that OTHER bolts in the door assemblies have been found loose...

 

[SWComposites]

yes, but those loose bolts do not appear to have anything to do with the plug door opening.

 

[3DDave]

None of the other loose bolts could in any way allow the door to leave. If the bracket retaining bolts had been removed the spring that is to push the door out of position could no longer to that; it would eliminate a way to get the door to leave. Sort of an anti-defect for this accident. As long as the upper keeper bolts were in place the door could not move off the stops.

 

[dgallup]

Our friend Juan has a good series of videos on this

https://www.youtube.com/watch?v=ubCQZtLTAug&t=705s

----------------------------------------

The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[waross]

The spring is basically neutral when the door is closed

No, The springs are compressed when the door is closed.
In normal closed position the springs are compressed and pushing upwards.
This is normally restrained by the four bolts on the factory floor.

It's already been PROVEN by inspection that OTHER bolts in the door assemblies have been found loose...
.........
yes, but those loose bolts do not appear to have anything to do with the plug door opening.

All points to Boing's deteriorating standards and procedures.
If this is the best that they can do after the original crashes, maybe Boing should not be building civilian planes anymore.
Let's see what the market decides over the next couple of years.
It is certainly a strong disincentive to not buy Boing.
MBAs in purchasing may start to look past the pennies and start asking;
"What will happen next to ground our planes."
Sorry about you pension John.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!