Alaska Airlines 737-900 MAX loses a door in-flight out of PDX
I read somewhere that Spirit installs the plugs in a provisional manner but that they are then removed by Boeing because they need access when they complete the aircraft. It seems very likely that Boeing would at least open them as normally there is a door there and their procedures would be based on that.
Look at the photos, with a plug there is the guide fitting between the top two contact pads. Now look at the photo of a door. With a door fitted there is another device further down in the frame which is part of the door locking/unlocking mechanism. That is not there with the plug so that also would have to be installed if Boeing did the swap. That would require I assume removing some of the existing rivets or drilling new holes to install those. Given the backlog of orders Boeing knows well in advance what spec product to order from Spirit, the only possible exception would be orders that end up not being taken up. I suggest to you that in that case the aircraft will be built as ordered and parked green or as a white tail until a buyer can be found at which point the aircraft is likely to be flown back to spirit for modification, if required, before returning to Seattle for cabin installation.
I could however be wrong and wait with baited breath to be corrected.
Last edited by Peter Fanelli; 8th Jan 2024 at 18:57.
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NTSB B-Roll - Alaska Airlines Flight 1282 Boeing 737-9 MAX
https://youtu.be/QoiGuuGZPNc?si=YEUrKSRCY8nQPNPw&t=132
Check out 2:12 - the right side is being examined and light is coming through. Either the NTSB opened the right side for inspection, or the right side was also not secured.
https://youtu.be/QoiGuuGZPNc?si=YEUrKSRCY8nQPNPw&t=132
Check out 2:12 - the right side is being examined and light is coming through. Either the NTSB opened the right side for inspection, or the right side was also not secured.
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Are we, perhaps, seeing the difference between a cabin depressurisation following, say, a window blowing out, and the effect of a hole suddenly appearing that's many times the size of a window?
The end result will be the same - a cabin at ambient pressure - but the time taken to get to that point will almost certainly vary. What rate of decompression are cockpit door blowout panels intended to cope with?
The end result will be the same - a cabin at ambient pressure - but the time taken to get to that point will almost certainly vary. What rate of decompression are cockpit door blowout panels intended to cope with?
Does the door even have blow-out panels? They may have been disabled to prevent terrorist access.
It's around 10 psia outside at 16k feet, so if fully pressurized to 15 psia that is only a 50% expansion - the volume of air in the cockpit and the area below the cockpit to be expelled is 50% of the geometric volume. The greatest pressure is 5 psi; ~20 inch X 70 inch door = 7000 lbs, or 3500 pounds on the latch. I would bet the latch is fine and the door simply flexed enough to disengage. The energy stored in the flex might be what damaged the lavatory door from arching back the other way when the latch slipped.
(edit) **I forgot about the crown blowout; that must have been after 9/11. It may not have been as large as this but it was close.
Last edited by MechEngr; 8th Jan 2024 at 18:20.
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Makes no sense, Spirit builds the fuselages and therefore the doors. Why build and install a plug or door in Wichita only to be removed at final assembly. Spirit obviously makes the emergency exit doors, are they going to ship doors to Boeing so they can remove the plug and install a door? Is Boeing going to manufacture doors in Seattle to fit to some aircraft? What happens to the now redundant plugs removed from fuselages on arrival from Kansas? Do they now get shipped back to Kansas for reuse?
Look at the photos, with a plug there is the guide fitting between the top two contact pads. Now look at the photo of a door. With a door fitted there is another device further down in the frame which is part of the door locking/unlocking mechanism. That is not there with the plug so that also would have to be installed if Boeing did the swap. That would require I assume removing some of the existing rivets or drilling new holes to install those. Given the backlog of orders Boeing knows well in advance what spec product to order from Spirit, the only possible exception would be orders that end up not being taken up. I suggest to you that in that case the aircraft will be built as ordered and parked green or as a white tail until a buyer can be found at which point the aircraft is likely to be flown back to spirit for modification before returning to Seattle for cabin installation.
I could however be wrong and wait with baited breath to be corrected.
Look at the photos, with a plug there is the guide fitting between the top two contact pads. Now look at the photo of a door. With a door fitted there is another device further down in the frame which is part of the door locking/unlocking mechanism. That is not there with the plug so that also would have to be installed if Boeing did the swap. That would require I assume removing some of the existing rivets or drilling new holes to install those. Given the backlog of orders Boeing knows well in advance what spec product to order from Spirit, the only possible exception would be orders that end up not being taken up. I suggest to you that in that case the aircraft will be built as ordered and parked green or as a white tail until a buyer can be found at which point the aircraft is likely to be flown back to spirit for modification before returning to Seattle for cabin installation.
I could however be wrong and wait with baited breath to be corrected.
Other optional doors or fill-in replacement structures were also offered on a predecessor model, the 737-900ER.
As part of the production process, Spirit builds fuselages for 737s and sends them by train with the special door assembly “semi-rigged,” one of the people said.
At its Renton, Washington, plant, Boeing typically removes the pop-out, or non-functioning, door and uses the gap to load interiors. Then, the part is put back and the installation in completed. Finally, the hull is pressurized to 150% to make sure everything is working correctly, the person said.
As part of the production process, Spirit builds fuselages for 737s and sends them by train with the special door assembly “semi-rigged,” one of the people said.
At its Renton, Washington, plant, Boeing typically removes the pop-out, or non-functioning, door and uses the gap to load interiors. Then, the part is put back and the installation in completed. Finally, the hull is pressurized to 150% to make sure everything is working correctly, the person said.
It's not totally clear to me if the last part refers to the MAX or the 900ER procedures but it does have to have a decent plausibility that Boeing also removes the plugs on the MAX-9.
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I read somewhere that Spirit installs the plugs in a provisional manner but that they are then removed by Boeing because they need access when they complete the aircraft. It seems very likely that Boeing would at least open them as normally there is a door there and their procedures would be based on that.
If the bolts are missing or incorrectly installed Boeing would be responsible.
I haven't been able to verify the information but those interested in the blame game probably should try before absolving Boeing.
If the bolts are missing or incorrectly installed Boeing would be responsible.
I haven't been able to verify the information but those interested in the blame game probably should try before absolving Boeing.
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The added WiFi dome on the top of the fuselage
They're not looking at the area of the plug, though, are they? The windows are at the normal spacing of 2 per sidewall panel, but it's different where the plug is. In addition, the whole sequence from 1:42 to 2:39 suggests that they're interested in an area about three or four rows forward of the very aft end of the cabin, which would be about row 30; the plug is around rows 25 and 26.
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The 737 Handbook
Flight Deck Door Pressure Relief Latch,
Flight deck door has 2 blowout panels for case of rapid decompression in the flight deck
This system is necessary as all the cabin air would rush through, and possibly over-stress, the flight deck door Pressure Relief Latch is set to release under pre-determined pressure When released, the blowout panel will open into the flight deck and equalize the pressure between the cabin and flight deckShould there be a rapid decompression in the cabin, the flight deck door is able to withstand the pressure difference as the area of the flight deck is relatively small (pressure will equalize through the leaks through the door, blowout panels won’t open)
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Thoughts on the decompression:
There is a rule in the FARs, 25.365, that lays out what decompression conditions that pressurized compartments have to be able to withstand.
There's a handy little formula in subsect (e) that, if my math is correct, and using a 12-ft fuselage diameter, works out to about 4 square feet. So basically all models of the 737 since probably 1980 should have been certified for a decompression with a hole size 4 ft^2. Alaska 1282 was clearly much bigger than this. That would explain why the cockpit door failed, it wasn't designed for the delta-p that 1282 saw.
Consequence #1: The airframe, particularly the floor structure, was overloaded. I won't be surprised if N704AL is out of service for some time while Boeing determines if the floor is still ok, and what reworks if any are needed. Probably all the interior will have to be replaced.
Consequence #2: The FAR says:
I've worked on decompression before, and we never considered door blowouts because they are considered "extremely remote". For operable doors this is true, they never blow out because of their design features. For door plugs, we now know this isn't the case, so I won't be surprised if 1282 causes a round of rulemaking to address that. I wouldn't be shocked if in the future, the cockpit annunciators for door plugs are actualy hooked up to something.
There is a rule in the FARs, 25.365, that lays out what decompression conditions that pressurized compartments have to be able to withstand.
There's a handy little formula in subsect (e) that, if my math is correct, and using a 12-ft fuselage diameter, works out to about 4 square feet. So basically all models of the 737 since probably 1980 should have been certified for a decompression with a hole size 4 ft^2. Alaska 1282 was clearly much bigger than this. That would explain why the cockpit door failed, it wasn't designed for the delta-p that 1282 saw.
Consequence #1: The airframe, particularly the floor structure, was overloaded. I won't be surprised if N704AL is out of service for some time while Boeing determines if the floor is still ok, and what reworks if any are needed. Probably all the interior will have to be replaced.
Consequence #2: The FAR says:
In complying with paragraph (e) of this section, the fail-safe features of the design may be considered in determining the probability of failure or penetration and probable size of openings, provided that possible improper operation of closure devices and inadvertent door openings are also considered.
Last edited by incompleteness; 8th Jan 2024 at 19:53.
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Maybe not the 737, If the following is correct.......
June29,2019 ·
Flight Deck Door Pressure Relief Latch,
Flight deck door has 2 blowout panels for case of rapid decompression in the flight deck
This system is necessary as all the cabin air would rush through, and possibly over-stress, the flight deck door
Pressure Relief Latch is set to release under pre-determined pressure
When released, the blowout panel will open into the flight deck and equalize the pressure between the cabin and flight deck
Should there be a rapid decompression in the cabin, the flight deck door is able to withstand the pressure difference as the area of the flight deck is relatively small (pressure will equalize through the leaks through the door, blowout panels won’t open)
The 737 Handbook
June29,2019 ·
Flight Deck Door Pressure Relief Latch,
Flight deck door has 2 blowout panels for case of rapid decompression in the flight deck This system is necessary as all the cabin air would rush through, and possibly over-stress, the flight deck door Pressure Relief Latch is set to release under pre-determined pressure When released, the blowout panel will open into the flight deck and equalize the pressure between the cabin and flight deckShould there be a rapid decompression in the cabin, the flight deck door is able to withstand the pressure difference as the area of the flight deck is relatively small (pressure will equalize through the leaks through the door, blowout panels won’t open)
Always wondered a bit about that...
BTW, I've not observed that to be exclusive to the 737...
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BREAKING: United has found loose bolts and other parts on 737 Max 9 plug doors as it inspects its fleet of Boeing jets following the rapid depressurization aboard an Alaska jet, according to three people familiar with the findings. per theaircurrent.com
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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. It is an official accident with lead investigator John Lovell (NTSB investigator in MAX crash in Ethiopia) leading the investigation. She said they have a general location based on primary radar for the door. Aircraft delivered to Alaska on November 11, 2023. Row 25 and 26 seats A missing headrests. On 26A, the back of the seat is missing. Clothing items in the area. Stops on door frame still intact. Door is not an emergency exit but can be opened for inspection.
Choosing to ignore other factors, there is randomly > 95% probability that 26A would NOT be empty, and > 99% probability that 26A and 26B would BOTH not be empty. In a root cause investigation, probabilities above 95% are usually considered significant.
Putting this together with the 3 prior auto-pressurization events I expect they will look closely to see if the seats were de-prioritized/blocked (at least 26A) due to intermittent noise, and my speculation is they are, and they are related.
It is possible the cause of the auto-pressurization warning was transient during certain flight phases, therefore when switched to ALT things looked fine. Uncomfortable noise may have also occurred transiently, again depending on flight phase. There is more insulation covering the plug than there would be covering a normal exposed door, but apparently air leaks are very loud.
Main point is it is extremely unlikely the empty seats were randomly empty.
(If you are going to reply that 2 people reserved the seats and missed the connection, please include a source.)
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LINK
"AAR did not perform any work on or near any mid-cabin exit door plug of that specific aircraft. AAR was contracted by Alaska Airlines to perform a 2KU Modification (Wi-Fi modification) on the aircraft that was performed from November 27 to December 7, 2023."
Last edited by lateott; 8th Jan 2024 at 20:12. Reason: Trimmed
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Intelsat / Gogo 2Ku retrofit? Pretty on the outside ...
Above three pics are from the Intelsat brochure at https://www.gogoair.com/brochures/go...duct-brochure/ - I am guessing the WiFi retrofit was the largest intervention within the interior of this aircraft since it was first put into service at Alaska?