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

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

Old 18th Jan 2024, 18:18
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Generally it seems the flight crew did an excellent job, and certainly got the plane down intact with 100% survival. However, out of curiosity I was looking at the event timing as read out by NTSB and I am wondering if those with commercial training or experience with decompression and emergency descent would comment on the reaction times in this situation and how it compares to your experience or simulator training. I have not found a time-stamped version of the ATC communications with which to correlate.

Decompression and emergency descent are "memory item" checklists. I read at least one CAP describe the simulator training as "You hear the bang, you execute the memory items without hesitation." B737 memory items are shown below (at least some historic version), note that CREW COMMUNICATIONS-ESTABLISH in the decompression checklist is between the pilots after donning masks, not with the cabin crew or ATC.

It took 1:08 after the event for the plane to start descending. Does that fit your expectations when considering reaction time and aircraft control/response time? What else may have been happening in what seems like a long minute? It took 4:27 to get down to 10,000ft while ascending at only 14,830.




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Old 18th Jan 2024, 19:33
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To be honest that sounds like a long time to me as well... If you hear the cabin altitude horn I would at least expect to stop the climb while you're trying to figure out what's going on.
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Old 18th Jan 2024, 20:25
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Originally Posted by lateott
@ST Dog It would be very helpful to this forum if you would provide a source since you are so definitive about your conclusion.

Wish I could remember now. I thought it was one of Juan's videos, but possibly a comment on one of them.
I modified the post to make it less definitive.

At the same time, I've seen no documented claims that the seats were blocked off, or that there were noise complaints from those seats.
Alaska could clear it up with a definitive statement but I've not seen that either.

I don't place much store in Snopes. They claim an email from Alaska yet didn't publish the email.
The closest to a source is a Tweet from Pete Muntean @CNN

In both cases the wording is vague. No one assigned could mean the actual manifest shows the seats empty, not that no one had a tickets for those seats.
The lack of a definitive follow-up to the question about a missed connection leaves it open.

Several posts here have already pointed out the incredibly low probability that those 2 seats would both be vacant on a flight that was 96% full.
Agree and a missed connection seems a likely reason for that. The flight wasn't full so no standby passengers to be assigned.
For the last few years I been told to stay in my assigned seat until after takeoff, even on flights with a lot of empty seats.
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Old 18th Jan 2024, 21:30
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I believe there is a method to the madness with seat assignments. Unaccompanied minors or escorted passengers are in the very rear. Upgrades are in first and premium. Exit rows are often popular, too for leg room.

There's a bit of a bathtub effect where the Super Saver fares and non-revs fill in the area in question. If they didn't have 100%, that's a likely area to have a vacancy. Not much of a mystery and why suspect something? The seats weren't on an MEL.

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Old 18th Jan 2024, 23:49
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Originally Posted by DaveReidUK
I'd be interested in seeing​​ how that was worked out.

And the definition of "incredibly low probability".
The probability is small and gets smaller if you look at a single particular pair of seats: those closer to the left door plug. Even if we add constraints like all aisle seats being occupied and all empty seats being in coach class it would still be small. I'll take a stab at computing the probability with those constraints:

46 window and 46 middle seats for coach, so 92 seats that can be empty with my constraints. The chance for the window seat to be empty is 7/92. Once that seat is empty, the chance that the seat adjacent to it is also empty is 6 out of the remaining 91 seats. So, to compute the probability for the two events together, we multiply 7/92 by 6/91. Which is almost exactly 0.005. Just 0.5%. Or 1 in 200 flights.

And, if we remove my initial constraints, the probability gets even lower. We would have 7 empty seats out of 178. So the probability becomes 7/178 multiplied by 6/177, which is around 0.13%, or one in 750 flights.

Originally Posted by aox
I've booked seats at music gigs that were very nearly sold out

The chances of there being remaining seats adjacent to each other don't seem to be particularly small.
Not sure about those music gigs, but in cinemas, when choosing the seats by yourself, they usually do not allow you to leave a single empty seat between you and other occupied seats, to prevent ending up with one sit gaps in an occupied row, which would prevent couples from booking the last few seats if they want to be next to each other.

Now, if Alaska had some similar constraints for similar reasons, yes, the probability of finding 2 adjacent empty seats would be higher than what I computed above. Assuming they would try their best to group those 7 empty seats in pairs of two when booking, we would have 3 pairs of 2 seats and a separate empty seat. So, with the constraints I gave earlier, you would have 3 chances out of 46 to have them near the left plug. Or around 6.5%, one in 15 flights. Still low, but better than the 0.5% or 0.13% computed earlier.
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Old 19th Jan 2024, 06:11
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If Alaska suspected the door plug was unsafe, do you really think they would block two seats on the left, but not on the right? If they had had noise complaints I'm pretty sure Alaska would not have left the plug uninspected. The risks to passengers and the company's reputation are just too great.

Last edited by MarineEngineer; 19th Jan 2024 at 10:17. Reason: spelling
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Old 19th Jan 2024, 06:46
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Originally Posted by MikeSnow
46 window and 46 middle seats for coach, so 92 seats that can be empty with my constraints. The chance for the window seat to be empty is 7/92. Once that seat is empty, the chance that the seat adjacent to it is also empty is 6 out of the remaining 91 seats. So, to compute the probability for the two events together, we multiply 7/92 by 6/91. Which is almost exactly 0.005. Just 0.5%. Or 1 in 200 flights.

Assuming they would try their best to group those 7 empty seats in pairs of two when booking, we would have 3 pairs of 2 seats and a separate empty seat. So, with the constraints I gave earlier, you would have 3 chances out of 46 to have them near the left plug. Or around 6.5%, one in 15 flights. Still low, but better than the 0.5% or 0.13% computed earlier.
Excellent modelling, well done!
That gives a pretty robust upper threshold of that probability.
In my experience pax are sometimes moved around by (sympathetic and motivated) FAs, if they know there is some inconvenience with seats, the least of which is being kitty-cornered to the loo.
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Old 19th Jan 2024, 07:59
  #1108 (permalink)  
 
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Originally Posted by STBYRUD
To be honest that sounds like a long time to me as well.
Just to add that it does fit my expectations.

Startle factor, then removing noise cancelling headsets and possibly sun/glasses too, putting them somewhere safe then squeezing, pulling, donning and releasing the mask, locating and replacing headset and glasses, locating the mic/oxy switch and checking in with each other before continuing the recall items. The autopilot then has to convert, say, +1500fpm to about -4000fpm at (I think) 0.1g. It all takes time and must be done methodically.
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Old 19th Jan 2024, 08:05
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The probability of those two seats being unoccupied, given that they were unoccupied, is 100%.
(see e.g. W M Briggs for explanation of how probability is conditional)
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Old 19th Jan 2024, 08:31
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Empty Seats

Originally Posted by C2H5OH
Excellent modelling, well done!
That gives a pretty robust upper threshold of that probability.
In my experience pax are sometimes moved around by (sympathetic and motivated) FAs, if they know there is some inconvenience with seats, the least of which is being kitty-cornered to the loo.
Also as ST Dog pointed out in post #1108 “In both cases the wording is vague. No one assigned could mean the actual manifest shows the seats empty, not that no one had a tickets for those seats” . If the missed connection explanation was correct then surely Alaska would have been quite clear and upfront about it. If, for example, the seats were intentionally not allocated - possibly because of previous complaints of high noise then corporate vagueness wouldn’t be surprising.
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Old 19th Jan 2024, 09:34
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More Probabilities..

Seeing as we seem to be discussing Probabilities...
I wonder what the probability is of the NTSB having checked the airplane for any further loose bolts in the right hand side Plug-Door.
We might need to wait for a month or so, to get any official updates from the NTSB or FAA.
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Old 19th Jan 2024, 10:23
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It's 100%. NTSB has stated that the opposite door was secured correctly.



Last edited by MarineEngineer; 19th Jan 2024 at 14:18.
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Old 19th Jan 2024, 10:47
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Information…lack

What would help (without having a full set of drawings and manufacturing docs and final assembly procedures ) is:

a full sequence of photos … from interior installed with blankets etcetera, to stripping that all away until free to open the plug, and the reverse process…

Alaska information on the empty seats and seating in general (policy and specific)..

Intentionally not seating a person in the specific seat, or a person there moving seats … a reason might have been “noise” at that seat, might have been perceived as a loose panel, so something to mention but no fuzz … and that the pressurisation issue was seen as something separate, and having a cause somewhere else, you would expect people to check for example actual doors first, not checking a fuselage structure panel that might be opened once a year…

might followed by might is speculation of course

hope we hear more in the factual prelim report that generally comes out at accident date plus 30 days

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Old 19th Jan 2024, 11:45
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Originally Posted by scifi
Seeing as we seem to be discussing Probabilities...
I wonder what the probability is of the NTSB having checked the airplane for any further loose bolts in the right hand side Plug-Door.
We might need to wait for a month or so, to get any official updates from the NTSB or FAA.
I think the probability is 100%, and indeed I seem to recall that at one of the NTSB press briefings they said they had done so and had found no problems with the right hand door-plug on the incident aircraft.
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Old 19th Jan 2024, 12:16
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Originally Posted by roger4
I think the probability is 100%, and indeed I seem to recall that at one of the NTSB press briefings they said they had done so and had found no problems with the right hand door-plug on the incident aircraft.
I think we've seen photos or video of the NTSB investigators doing just that. I'll search, unless someone remembers where those can be found.
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Old 19th Jan 2024, 15:14
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Originally Posted by lateott
Several posts here have already pointed out the incredibly low probability that those 2 seats would both be vacant on a flight that was 96% full.
Before we get too carried away here with theoretical theories ...

- The flight's scheduled type was a smaller MAX-8, which was used on all preceding days. However, as this particular MAX-9 had been restricted from ETOPS flying, there was a switcharound, and it was used.
- The additional seat rows it provided were at the back, where the plug is. These rear seats were all completely unreserved when the aircraft switch was made.
- Most passengers in the USA select their seats at booking, which would be before the additional seats were known.
- The most favoured seats are forward, to be first out of the aircraft.
- In the USA, there is a notable preference for aisle seats. This may seem strange to Europeans, where there is more of a preference for window seats. Note the one passenger in the incident row was in the aisle seat.
- There were several seats which were vacant, not just these two. Likely they were all around this area.
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Old 19th Jan 2024, 15:33
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No more on probabilities, please, they will probably be deleted.

Thanks.
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Old 19th Jan 2024, 15:36
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And without wishing to add another factor to the calculation, here is one! I don’t know about our North American friends, but in the UK it’s quite common when booking seats to request those with extra leg room. In fact I’ve just done that for a Jet2 flight (737-800) to Madeira in a couple of months. So, IF my assumption is correct that these seats on the Alaska flight had extra leg room, to me it would be even more surprising that they just happened to be unoccupied.
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Old 19th Jan 2024, 15:51
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The 9 only has nine extra seats in economy. This is where the empty seats would have been if the plane was switched late.




Seat plans from SeatGuru


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Old 19th Jan 2024, 16:15
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Why would you assume row 26 has extra leg room? It's not an emergency exit row.
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