Alaska Airlines 737-900 MAX loses a door in-flight out of PDX

[A0283]

Credit to MLHeliWrench for that Reddit photo ! Would be interesting to get more of those… and more if details.
Would also be interesting to have a comparable photo of an activated door configuration.

Trying to picture both the installation sequence and an emergency operation sequence. Plus remarks made by other posters. And photos of the accident aircraft.

For me only questions at this stage.

Question - do we have 6 shear pins (??????) per side here (on the accident aircraft photos the holes seem still filled up), plus 1 per side cam roller high up, and 1 per side cam below?

Question - do we have 1 (black top) spring element here per side below? And do these assist in shearing??? So apparently, not only moving the door/hatch up,but also shearing.

Question - does this mean (is that what other posters mean) that we only have 2 locking elements high up and only 2 below 2+2=4 (if we exclude the 6+6=12 shear pins)???

Appears to be a built-up door and less integrated than I would expect at this day and age.
Question - Does someone know if they use this structure assy as the basis for the manufacture of an active door (machining/drilling/bushing this assy and adding emergency operating mechanisms)?

Appears they do a solid paint job on this door.

If the HS-748 case from long ago would be predictive, then you would expect more aircraft having had installation and/or pressurisation problems (apart from this one).
Might be that a structural door cause would not be the type of cause (platform/ gate based) maintenance would look for at the start, when confronted with pressurisation problems.

[DaveReidUK]

Originally Posted by aeromech3

The community picture on Reddit, has a seat config which would suggest the use as an emergency exit when required?

The massive amount of legroom does indeed make it look like that, but the plug door cannot be used as an E/E (no opening mechanism, no slide, no vent panel, etc).

It is, however, possible to substitute a functioning door to increase the passenger limit, but if that happens it's only likely to be done once during the life of the aircraft.

[procede]

Originally Posted by DaveReidUK

The massive amount of legroom does indeed make it look like that, but the plug door cannot be used as an E/E (no opening mechanism, no slide, no vent panel, etc).

It is, however, possible to substitute a functioning door to increase the passenger limit, but if that happens it's only likely to be done once during the life of the aircraft.

My guess is that they removed a row of seats to do the inspection.

[DaveReidUK]

Originally Posted by A0283

Question - Does someone know if they use this structure assy as the basis for the manufacture of an active door (machining/drilling/bushing this assy and adding emergency operating mechanisms)?

Almost certainly not, I can't see any advantage in doing that compared to building an actual E/E door from scratch.

[A0283]

Originally Posted by msbbarratt

Anyone know the glide angle of a door plug?

As usual in aerospace… there is at least one (NTSB or FAA) paper on that… if I remember correctly it had different formulas for different shapes and sizes… don’t remember if it had a formula for cleanly departing doors …

[MLHeliwrench]

Originally Posted by procede

My guess is that they removed a row of seats to do the inspection.

yes, a row would need to be removed to pull the interior panels with relative ease.

below is I picture with what I would guess as the only ‘lock bolts’ keeping the plug from sliding up and out off the retention fittings. This is only speculation. I’m not familiar with how the lower part works. If it’s actually a hinge or just hooked in there.



Blue circles highlight possible lock bolts.

[aeromech3]

Originally Posted by DaveReidUK

The massive amount of legroom does indeed make it look like that, but the plug door cannot be used as an E/E (no opening mechanism, no slide, no vent panel, etc).
It is, however, possible to substitute a functioning door to increase the passenger limit, but if that happens it's only likely to be done once during the life of the aircraft.

Didn't mean to imply the plug would be used in an exit config; worked on a VC10, with cargo door which we could re-config the interior to full pax in a shift; if I recall the hydraulic ram had to be removed; another a HS748 remove passenger seats and install canvass ones for the task; perhaps this airline has the E/E door in storage, not ascertained where the slide would be fitted but as the E/E door has to open outward it might be part of the door and deploy split seconds before the door, as there is no fairing below the aperture for a stowage, interesting!

[kghjfg]

I noticed those too, on the picture with the door missing the pin that comes out of the fuselage to engage into the sliding socket on the door looks very short.

It doesn’t look long enough to properly engage and the lock bolt to stop the door sliding back up.

[rog747]

AFAIK
There have not been any previous issues before with this type of exit door (which is a drop down hatch with a Slide, added aft of the wing) as fitted on the 737-900ER,
and to the latest 737M8-200, and as seen here on the 737M-9
(a door will also be fitted on the M-10 but it is, I think larger)

This type of hatch (once called the hat rack door) was first fitted to the Boeing 707-320C first delivered 60 years ago in 1963.
AFAIK there were no issues with these doors that I can recall.
That old design may still today be a legacy from that 707 door design?
I do not know if this maybe the case sorry, but worth a Pprune ponder?

FYI
They were also fitted to the DC-8 Super Sixty series as well as the -55F series.

In the case of yesterday's incident I expect that both installation and/or quality control to be at the fore of the Investigations.

[fenland787]

Originally Posted by kghjfg

I noticed those too, on the picture with the door missing the pin that comes out of the fuselage to engage into the sliding socket on the door looks very short.

It doesn’t look long enough to properly engage and the lock bolt to stop the door sliding back up.

I agree, zooming in on the higher res image of the failed door/plug in post #194 (it's still very hard to be sure I'm not just seeing artefacts in the image) but it almost looks like the visible end of the pin is showing an axial counterbore hole and an uneven surface at about the point that cross bolt would have been?
However if that were the issue then a quick visual inspection of the pins would not find it and the inspection of the other aircraft would surely take longer than it seems to......

[Edoil17]

Maybe the panel installer wouldn't be particularly interested, but someone (whom, is really interested in what is going on at this opening) should have "inspected" the area behind this panel prior to installing the trim panel. That was always due process when closing up any panel / door. Cheers

[WHBM]

Originally Posted by PuraVidaTransport

According to the NTSB briefing tonight, there were only SEVEN (7) empty seats so just 4%. Alaska had 178 seats on the aircraft and the spokesman said there were 171 passengers.

The whole discussion here reminds one of the old joke : "When is a door not a door ..."

The fortuitous chance of the adjacent seats not being occupied may be linked to this particular flight, in previous days, always being operated by a lesser capacity 737-MAX8, which is presumably the scheduled type. Accounts describe this particular airframe having been removed from ETOPS usage by Alaska (principally their routes to Hawaii) due to outstanding pressurisation issues, but was still felt capable of internal US flights. One imagines this latter decision by Alaska will come under some review.

It will be interesting to track down passengers seated there on immediately previous flights, and ask them if there was any excessive noise from the cabin wall, given that it was losing sufficient pressurisation to be noticed. Then ask the flight attendants what was reported about that.

[DogTailRed2]

On the failure door and the one above why is the edge trim missing? Is that normal when deploying the escape hatch? To an untrained eye to see the packing in the fuselage looks weird.

[AirScotia]

It does seem surprising to me that an airframe with known pressurisation issues wasn't taken out of service right away. It also seems odd to me that two seats next to the relevant window were apparently empty, two of only seven unoccupied seats in a full flight - including a window seat at that. That suggests that these seats were not bookable, which further suggests that something was known about that area of seating. Whistling noises? Rattling? Cold breeze?

[Thruster763]

The "pins" visible in the high res picture of the incident door and parts highlighted in blue in the post by MLHeliwrench are the guide mechanism, not the locking pins. The lock pins are lower down. The guides take the load as the door moves up so the striker pad support structure is not damaged as the door or plug moves out.



That said I agree with MLHeliwrench and MechEngr that missing or loose upper bolts are the most likely cause.
The bolts do not carry any pressurisation forces they just stop the plug moving up to disengage the striker pads.
I don't know how the hinge bolts operate, but guess that they are just locking the lifting spring loads.
If the lower bolts take the spring loads and the door was closed with no upper bolts then the sealant on the outside would be able to hold the plug in place for some time. before finally giving way and allowing the door to move.

[aeromech3]

Freight door?

Originally Posted by Thruster763

The "pins" visible in the high res picture of the incident door and parts highlighted in blue in the post by MLHeliwrench are the guide mechanism, not the locking pins. The lock pins are lower down. The guides take the load as the door moves up so the striker pad support structure is not damaged as the door or plug moves out.

Is your picture of a lower freight door which opens inwards and swings up into a freight bay ceiling and has a handle mechanism which extends pins into the door aperture frame when closing?
I don't see such a mechanism in the E/E semi plug pictures.
Am I missing the point of your post?

[Jetstream67]

tdracer , 7th Jan 2024 00:25
Before you all get too wrapped up in your anti-Boeing crusade, you might want to consider this little inconvenient fact: The fuselage isn't built by Boeing -
———————————-//-/

Boeing, Apple, Ford, Samsung. Almost every large manufacturer today is a systems integrator. Their job is to specify, test and integrate the many elements of their design of end product

When it goes wrong they can blame their supplier publicly or privately but their customers are being let down by the final product /brand’s defects.

[Thruster763]

Originally Posted by aeromech3

Originally Posted by Thruster763

The "pins" visible in the high res picture of the incident door and parts highlighted in blue in the post by MLHeliwrench are the guide mechanism, not the locking pins. The lock pins are lower down. The guides take the load as the door moves up so the striker pad support structure is not damaged as the door or plug moves out.

Is your picture of a lower freight door which opens inwards and swings up into a freight bay ceiling and has a handle mechanism which extends pins into the door aperture frame when closing?
I don't see such a mechanism in the E/E semi plug pictures.
Am I missing the point of your post?

It is a picture of a door guide and striker plates. The point of my post is the parts ringed in blue in the image by heliwrench and "pins" in pictures of incident fuselage frame (silver coloured) are NOT the locking pins or bolts, they are the door / plug guides on door / plug and guide pins on frame.

EDIT,
Just looked again and it appears that the guide pin and lock pin are combined on the mid emergency exit door. So the bolts do go intor the center of the guide pins. Sorry for the confusion.

[EXDAC]

In the image of post 223 I see a wire loop on each side of the door (about level with the top of the window). These look similar to the wire tethers used on pip pins.

Are pip pins used to lock the door in place?

[aeromech3]

Originally Posted by EXDAC

In the image of post 223 I see a wire loop on each side of the door (about level with the top of the window). These look similar to the wire tethers used on pip pins. Are pip pins used to lock the door in place?

I imagined these were just lanyards much like ceiling panels and others have to facilitate opening without uncontrolled dropping, the adjacent structure does not looked beefed up for a pip pin type lock, but I stand to be corrected!