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

[DTA]

Originally Posted by DaveReidUK

It's by no means certain that that's actually possible.

The upper restraining bolts go through holes in the guide tracks attached to the door plug. There would be no reason for those holes to exist in the guide tracks on a live door (I don't know whether they do or not, does anyone?).

The lower bolts go through holes in the fitting that hinges down as the door opens. The jury still seems to be out re whether it's the same fitting on the live door, because of the debate on how far the respective doors are able to open and, if they're different, whether the holes exist on both.

So may turn out that it's not actually possible to lock the live door in place with those bolts. We need someone with an AMM.

Post 726 shows the live door and the holes in the upper guides are visible. I guess this reduces the spares holding required.

[Thrust Augmentation]

Originally Posted by DaveReidUK

The upper restraining bolts go through holes in the guide tracks attached to the door plug. There would be no reason for those holes to exist in the guide tracks on a live door (I don't know whether they do or not, does anyone?).

[MarineEngineer]

If I were tasked with closing and securing that door, I might pull it inwards and push it down with one foot. Then I would an undersize bolt, welding rod, nail or similar in one of the four holes just to keep it in place while I positioned the proper bolts. If this had been done but the last step had been omitted, it might explain why it took so long for the incident to occur.

[sandringham1]

Originally Posted by DaveReidUK

Not quite.

In Chris Brady's videos, he rightly labels them "lift assist springs". It's someone either inside or outside of the aircraft, pulling down the actuation lever, that provides the additional force required to lift the door off the rollers. The springs were originally fitted because of the difficulty in opening the door purely by brute force.

The spring assist was especially important if the door had an escape slide hanging on it, I guess.
What I don't understand is how the door, that appears to fit tightly into the fuselage skin with a small shut line, is able to move upwards on the rollers/guide fittings enough to allow the 12 stop pads to be cleared. Doesn't the door skin conflict with the fuselage skin at the top.

[Thrust Augmentation]

Originally Posted by sandringham1

What I don't understand is how the door, that appears to fit tightly into the fuselage skin with a small shut line, is able to move upwards on the rollers/guide fittings enough to allow the 12 stop pads to be cleared. Doesn't the door skin conflict with the fuselage skin at the top.

There is a gap of sorts at the top, look at post #783.

[sandringham1]

Originally Posted by Thrust Augmentation

There is a gap of sorts at the top, look at post #783.

I saw that but didn't believe they would do it like that, I wonder where any water getting in there goes?

[D Bru]

Mid-aft emergency exit deployment 737-900ER (referring to the discussion in this thread about how far the emergency exit can open on it’s bottom hinges, in comparison to the "plug"):

You Tube

Mid-aft emergency exit deployment 707 (several inside test view tests from 14:30, outside view tests start at 21:40):

You Tube

Clearly, some things have developed since….

Interesting though that in the 707 this emergency exit door was a proper “plug” type: opening to the inside, impossible to “escape”, the door/plug that is. But as the different tests demonstrate, what to do with such a sizeable object inside the aircraft in case of an emergency (exit)?

[hoistop]

Originally Posted by D Bru

Mid-aft emergency exit deployment 737-900ER (referring to the discussion in this thread about how far the emergency exit can open on it’s bottom hinges, in comparison to the "plug"):

But as the different tests demonstrate, what to do with such a sizeable object inside the aircraft in case of an emergency (exit)?

Pull it in, then throw it out of the airplane. No need to store it inside. (in real emergency)

[rog747]

Originally Posted by D Bru

Mid-aft emergency exit deployment 707 (several inside test view tests from 14:30, outside view tests start at 21:40):

https://www.youtube.com/watch?v=LUyKK3mSqPw

Clearly, some things have developed since….

Interesting though that in the 707 this emergency exit door was a proper “plug” type: opening to the inside, impossible to “escape”, the door/plug that is. But as the different tests demonstrate, what to do with such a sizeable object inside the aircraft in case of an emergency (exit)?

Great 707 archive, thanks - way long before the days of throw it outside rather then place it on the seats, or in this case it went on the floor!

As mentioned above when at BMA we reconfigured our 707C's for 212 pax, a new larger 757 type door (with a slide on the door) was fitted in place of what you see in the old AA 707 video.

[Mac the Mechanic]

The aircraft fuselage is curved as is the door cut-out so when the plug/door goes up it clears the upper edge.

[rog747]

It was pretty standard practice to place Overwing Exit hatches/windows, and hat rack door on to the seats, rather then throw it out -
Later on it became more standard to throw it out over the years...

The 737NG (700 800 and 900) had the novel upward hinging overwing exits hatches....

[DaveReidUK]

Originally Posted by Thrust Augmentation

Thanks, so it does seem it's possible to lock (i.e. disable) the live emergency exit with at least the top bolts. Though I guess, if that had ever been done, functional checks of the E/E would catch it.

[spornrad]

https://www.avweb.com/aviation-news/...-deficiencies/

[Less Hair]

Could somebody have installed an active emergency door configuration on a plugged door by accident? Like not installing the bolts and leaving the plug room to slide up?

[WHBM]

Originally Posted by EDLB

Amazing that with 63 lbs a plug, and you have two, one each side, there is no option to get the tube frame without those openings at all. 1kg mass is about 100L Jet-A1 a year for normal airline use. If I assume that without an airframe opening you get 15 lbs we talk about 4T of Jet-A1 every year only two carry two plugs.

Originally Posted by ozaub

And it’s not just weight of plug. Weight of frame will be at least as much again.

Back when the 737NG first offered the extended fuselage, from the 737-800 to the 737-900, the exit configuration was kept the same, as the aircraft met the desires of US trunk carriers who didn't need the full exit provision on the -800 for maximum seating, because of their first class, galleys, and extra legroom. The additional length, and seats, still complied with the seating evacuation limit for this fitout. However this variant was a very poor seller, I think they only sold about 50 (ironically Alaska were one of the few to take some), because finance companies didn't like them as they couldn't be remarketed later to anyone who did maximum seating.

Boeing then redid the design as the 737NG-900ER, which among other things introduced this plug/real exit door fitting. The US trunk carriers didn't lose seating at this point, or have the extra maintenance cost (they thought) for a proper exit at the opening, but it could be adapted later if and when required. The approach carried forward to the MAX9.

[Reverse rotation]

This side by side comparison of the door plug and functioning door also shows significant differences in the hinge mechanisms at the bottom of the door.

Post #765 shows the door plug being fully supported by the springs in their fully extended position. The force applied by the springs in their compressed state with the plug fully closed will be significantly more (Hookes law, force is proportional to compression) and, looking at how far off the stops the springs lift the door, the upward force being applied to the door to just clear the stops will be much greater than just the weight of the door.

[DaveReidUK]

Letter from 3 US Senators - Markey (D-MA), Vance (R-OH) and Welch (D-VT) - to Calhoun:

[DaveReidUK]

Originally Posted by Less Hair

Could somebody have installed an active emergency door configuration on a plugged door by accident? Like not installing the bolts and leaving the plug room to slide up?

I think you might have hit the nail on the head.

[Thrust Augmentation]

Originally Posted by sandringham1

I saw that but didn't believe they would do it like that, I wonder where any water getting in there goes?

I guess in terms of water sealing it's much like a car door seal, water gets under the edges into the area under the surface / outside the seals & drains away from the rear & bottom;

[CleanerCc]

Why are more people not talking about aar in OKC? I can't post pictures but if you go to Google maps 35.4015987, -97.6023138 you will see they have docking and ground ac carts they put on the left side right at door plug for the wifi mod. It would take nothing to open that door in a maintenance environment. Just because they said they did nothing in that area does not mean someone did not open the door.