Alaska Airlines 737-900 MAX loses a door in-flight out of PDX
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I doubt that, I don't think you would need to do anything with the lugs to open the plug or door. In a side view (looking along the airframe's longitudinal axis), the door or plug moves at a slight angle relative to the lugs so that it moves away from them (but against any pressure differential present in the fuselage) while moving up. That's why, when viewed from outside, there is room at the top for the plug/door to move up.
Difference of the plug compared to the real door
Just a thank you for all the explanations and theories. I haven’t had time to read everything so a couple of stupid questions from a retired driver:
Is the door plug just a stripped down normal exit door without a slide bustle?
Were the previously logged cabin pressure controller faults due to leakage induced bleed flow or something else?
And, if I may, supplemental irrelevant questions just for interest:
Does a 737 Max need a running (not just serviceable) APU for 180ETOPS?
Are Max main doors still dis/armed by kneeling and praying to the god of the girt bars, or have they been updated?
Is the door plug just a stripped down normal exit door without a slide bustle?
Were the previously logged cabin pressure controller faults due to leakage induced bleed flow or something else?
And, if I may, supplemental irrelevant questions just for interest:
Does a 737 Max need a running (not just serviceable) APU for 180ETOPS?
Are Max main doors still dis/armed by kneeling and praying to the god of the girt bars, or have they been updated?
Note the bolt hole in the roller guide
I’ll first answer question #2: the previously logged cabin pressure controller faults have been mentioned several times in the thread, and they were reported to be not linked to cabin air leakage.
Still, I think I’ve read that hissing noises had been reported nevertheless. Investigators will still have an open ear for this detail!
Now I come to your main question. See image above.
The door plug is an optional different and lighter ‘stand-in’ that has been designed to be compatible with the door frame around the opening for the additional emergency door devised for NG 900 / MAX 9 fuselages with high density seating. It has one normal passenger window (instead of the two windows that would probably fit in the space of the emergency door AND the surrounding door frame). Otherwise it’s a permanently covered structural hole-in-the-wall. Even from the outside it’s not too noticeable.
It lacks the inward-opening shoe-sized vent door in the uppermost part of the emergency door. And it lacks the handle for opening from the inside, and the slide pack in its bustle. Have a look at the post behind this permalink:
Alaska Airlines 737-900 MAX loses a door in-flight out of PDX .
It has no passenger window, but instead the typical small window for a standing person to oversee the outside conditions before deciding to actually open the door.
However, in looking for the linked image, I now dis-covered something that I didn’t notice before. The image reveals that the standard emergency door shows a small dark hole in the door-mounted guide for the fuselage-mounted roller. This looks like the hole where (in case of a door plug) the bolts that everybody is searching for should be to restrain the door (EDIT: door plug) from moving upwards.
I’ll have to leave the slightly off-topic two other questions open.
Last edited by Plumb Bob; 11th Jan 2024 at 16:23. Reason: Fell into the door plug trap.
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Reading the various quotes on the BBC article posted by Icare9 above, , the first question that comes to mind is : are there more bolts that need "additional tightening" or are missing anywhere else on those aircraft ? If I was the regulator I would ask for a thorough look everywhere else where there are bolts and nuts .. But that would effectively ground the aircraft for months ..And is it to be restricted to the MAX-9 ? , these " quality control failures" might exists on the other variants too..
Icare9
The BBC article actaully said
The aircraft, which were suspended in the US following an incident on an Alaska Airlines flight "need to be 100% safe", said Transportation Secretary Pete Buttigieg.
Which, to an engineer, means "never".
The BBC article actaully said
The aircraft, which were suspended in the US following an incident on an Alaska Airlines flight "need to be 100% safe", said Transportation Secretary Pete Buttigieg.
Which, to an engineer, means "never".
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Final check/build sheet mix up?
Final checks for the emergency door equipped MAX9 would not include making sure the lock bolt holes in fact have bolts installed.
Final checks for the plug equipped MAX9 would have a check/sign off for lock bolts installed.
Assembly crews (such as the folks putting in the interior panels) would be used to seeing those bolt holes in your picture empty on the emergency exit door equipped models. I wonder if this particular airframe was the first after a run of a few airframes equipped with emergency exit doors. Perhaps complacency or rushing though the task of checking all the doors/plugs: then signing off a whole page of sign offs could be a factor.
Final checks for the plug equipped MAX9 would have a check/sign off for lock bolts installed.
Assembly crews (such as the folks putting in the interior panels) would be used to seeing those bolt holes in your picture empty on the emergency exit door equipped models. I wonder if this particular airframe was the first after a run of a few airframes equipped with emergency exit doors. Perhaps complacency or rushing though the task of checking all the doors/plugs: then signing off a whole page of sign offs could be a factor.
I am hoping that a sufficiently definitive NTSB preliminary report is issued in 30 days or less. All the answers appear to be on the ground with no mysterious interactions between crew, aircraft, weather, et al that are the more frequent and overlapping set of conditions that lead to an investigation.
It seems like a fairly simple path as I previously outlined - design, manufacturing engineering, QA, QC, and the assemblers. Somehow this particular door happened as a result of a procedural disconnect.
The 1 year report can delve into the wider aspects of production controls and make recommendations for systemic improvements, but I at least want to see quite soon a report that Unnamed Person #1 did this and Unnamed Person #2 who was supposed to do that and didn't, so that the rest of aviation can then look to whatever those involved also touched and make sure it is OK.
It seems like a fairly simple path as I previously outlined - design, manufacturing engineering, QA, QC, and the assemblers. Somehow this particular door happened as a result of a procedural disconnect.
The 1 year report can delve into the wider aspects of production controls and make recommendations for systemic improvements, but I at least want to see quite soon a report that Unnamed Person #1 did this and Unnamed Person #2 who was supposed to do that and didn't, so that the rest of aviation can then look to whatever those involved also touched and make sure it is OK.
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Seems the FAA have formally notified Boeing that they are "conducting an investigation to determine if Boeing failed to ensure completed products conformed to its approved design and were in a condition for safe operation in compliance with FAA regulations"
https://www.faa.gov/newsroom/updates...max-9-aircraft
https://www.faa.gov/newsroom/updates...max-9-aircraft
"… Boeing jets (737-xxx) won't fly until safe ...."
"… are there more bolts that need "additional tightening" or are missing anywhere else on those aircraft ?"
Are there aircraft in service which have restraining bolts fitted to exits, but which are meant to be operational ? !
"… are there more bolts that need "additional tightening" or are missing anywhere else on those aircraft ?"
Are there aircraft in service which have restraining bolts fitted to exits, but which are meant to be operational ? !
Anyone notice this comment underneath Dominic Gates article in the Seattle Times, ref post 688:
"But there is a line tech, somewhere, that is likely removing these doors after manufacture AND after installation. Look at the picture from the United Airlines loose bolts. Everyone is focusing on the castle nut bolts, but the loose bolts in the picture are the bolts that connect the bottom hinge guide to the frame of the plug/door. Those should never be unscrewed, ever, BUT there are obvious tool marks on the heads of those bolts (post manufacture). Why would the hinges guide parts be removed from the door? ... It's obvious. The normal opening of the plug only goes 15 degrees. Someone wanted a quick way to remove the plug completely, for working in the cabin (maybe not dragging equipment around). Nobody wants to deal with spring tensioners or anything complicated, which would be needed if the plug was properly removed from the fuselage. So the shortcut is to remove the bottom hinge parts from the plug/door and pull the door out from the bottom. That's what the United Airlines picture shows, and it's likely what the other newly found loose bolts are (Alaska/UA hulls)."
Seems feasible?
"But there is a line tech, somewhere, that is likely removing these doors after manufacture AND after installation. Look at the picture from the United Airlines loose bolts. Everyone is focusing on the castle nut bolts, but the loose bolts in the picture are the bolts that connect the bottom hinge guide to the frame of the plug/door. Those should never be unscrewed, ever, BUT there are obvious tool marks on the heads of those bolts (post manufacture). Why would the hinges guide parts be removed from the door? ... It's obvious. The normal opening of the plug only goes 15 degrees. Someone wanted a quick way to remove the plug completely, for working in the cabin (maybe not dragging equipment around). Nobody wants to deal with spring tensioners or anything complicated, which would be needed if the plug was properly removed from the fuselage. So the shortcut is to remove the bottom hinge parts from the plug/door and pull the door out from the bottom. That's what the United Airlines picture shows, and it's likely what the other newly found loose bolts are (Alaska/UA hulls)."
Seems feasible?
Anyone notice this comment underneath Dominic Gates article in the Seattle Times, ref post 688:
"But there is a line tech, somewhere, that is likely removing these doors after manufacture AND after installation. Look at the picture from the United Airlines loose bolts. Everyone is focusing on the castle nut bolts, but the loose bolts in the picture are the bolts that connect the bottom hinge guide to the frame of the plug/door. Those should never be unscrewed, ever, BUT there are obvious tool marks on the heads of those bolts (post manufacture). Why would the hinges guide parts be removed from the door? ... It's obvious. The normal opening of the plug only goes 15 degrees. Someone wanted a quick way to remove the plug completely, for working in the cabin (maybe not dragging equipment around). Nobody wants to deal with spring tensioners or anything complicated, which would be needed if the plug was properly removed from the fuselage. So the shortcut is to remove the bottom hinge parts from the plug/door and pull the door out from the bottom. That's what the United Airlines picture shows, and it's likely what the other newly found loose bolts are (Alaska/UA hulls)."
Seems feasible?
"But there is a line tech, somewhere, that is likely removing these doors after manufacture AND after installation. Look at the picture from the United Airlines loose bolts. Everyone is focusing on the castle nut bolts, but the loose bolts in the picture are the bolts that connect the bottom hinge guide to the frame of the plug/door. Those should never be unscrewed, ever, BUT there are obvious tool marks on the heads of those bolts (post manufacture). Why would the hinges guide parts be removed from the door? ... It's obvious. The normal opening of the plug only goes 15 degrees. Someone wanted a quick way to remove the plug completely, for working in the cabin (maybe not dragging equipment around). Nobody wants to deal with spring tensioners or anything complicated, which would be needed if the plug was properly removed from the fuselage. So the shortcut is to remove the bottom hinge parts from the plug/door and pull the door out from the bottom. That's what the United Airlines picture shows, and it's likely what the other newly found loose bolts are (Alaska/UA hulls)."
Seems feasible?
An investigation? Good for them. I'd suppose that this door was not intended to depart the plane in midair, so I can intuit that, yes, Boeing failed.
Better close those barn doors. The horse is out.
I get that the enforcement by the FAA has to follow this path, but this is a path that can be put onto a post-it note.
I feel sorry for the FAA employees. They will once again be used as a punching bag by the politicians that short them necessary funds to both fully staff and attract enough top people to oversee every aspect of modern aviation. I guess we can expect a bunch of very concerned Representatives openly asking if they should cut money from the FAA budget until they can prove they can do better with less, knowing that if FAA can the Reps will see that as a reason to keep the funding low, and possibly cut it further.
Better close those barn doors. The horse is out.
I get that the enforcement by the FAA has to follow this path, but this is a path that can be put onto a post-it note.
I feel sorry for the FAA employees. They will once again be used as a punching bag by the politicians that short them necessary funds to both fully staff and attract enough top people to oversee every aspect of modern aviation. I guess we can expect a bunch of very concerned Representatives openly asking if they should cut money from the FAA budget until they can prove they can do better with less, knowing that if FAA can the Reps will see that as a reason to keep the funding low, and possibly cut it further.
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This is true, you would also need to remove upper lock bolts. However, your options for removing the door are 1. Disassemble the double-nut / washer atop each spring. Then pull the cotter pins, and remove the lock bolts. To which you slide the guide blocks off the springs and hinge. (reassembly is trickier as you must reengage the hinge into each block simultaneously). OR option 2. just remove 4 hex bolts (into nutplates no less) with your air ratchet and detach the blocks from the plug. Makes reassemble easier and you need not procure 2 more cotter pins. I think option two is what they do. Edit: Also, less assistance is needed outside for reassembly because the attachment is made while plug panel is in final position, rather than maneuvering the plug around to engage the hinges which I assume would involve another hand. I wouldnt be surprised if its not a one-man task altogether with this method.
Last edited by BigJETS; 11th Jan 2024 at 17:35.
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Missing Bolts
Final checks for the emergency door equipped MAX9 would not include making sure the lock bolt holes in fact have bolts installed.
Final checks for the plug equipped MAX9 would have a check/sign off for lock bolts installed.
Assembly crews (such as the folks putting in the interior panels) would be used to seeing those bolt holes in your picture empty on the emergency exit door equipped models. I wonder if this particular airframe was the first after a run of a few airframes equipped with emergency exit doors. Perhaps complacency or rushing though the task of checking all the doors/plugs: then signing off a whole page of sign offs could be a factor.
Final checks for the plug equipped MAX9 would have a check/sign off for lock bolts installed.
Assembly crews (such as the folks putting in the interior panels) would be used to seeing those bolt holes in your picture empty on the emergency exit door equipped models. I wonder if this particular airframe was the first after a run of a few airframes equipped with emergency exit doors. Perhaps complacency or rushing though the task of checking all the doors/plugs: then signing off a whole page of sign offs could be a factor.
This is true, you would also need to remove upper lock bolts. However, your options for removing the door are 1. Disassemble the double-nut / washer atop each spring. Then pull the cotter pins, and remove the lock bolts. To which you slide the guide blocks off the springs and hinge. (reassembly is trickier as you must reengage the hinge into each block simultaneously). OR option 2. just remove 4 hex bolts (into nutplates no less) with your air ratchet and detach the blocks from the plug. Makes reassemble easier and you need not procure 2 more cotter pins. I think option two is what they do. Edit: Also, less assistance is needed outside for reassembly because the attachment is made while plug panel is in final position, rather than maneuvering the plug around to engage the hinges which I assume would involve another hand.
And, given that that's not the way of removing the door that's provided for, it wouldn't be altogether surprising if it was accompanied by official denials that it was being done at all.
That said, if the lower lock bolts remained in situ, would inadequately-secured hinge bolts allow enough play for the stops to disengage? If not, we're back to square 1 in terms of an explanation for what happened.
Many years ago when I worked at Douglas, Long Beach, I wandered the production hangers in my spare time to learn all I could about how their aircraft were built. I forget the exact wording but there were multiple signs that said something like - "Perform the task exactly in accordance with the instructions or cause the instructions to be changed!" That was long before "six sigma" was going to save us all from ourselves.
Maybe Boeing should have saved a few of those signs before they demolished those production buildings.
Maybe Boeing should have saved a few of those signs before they demolished those production buildings.
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Approx 99.9999999% safe is the regulatory standard for a single catastrophic failure (10e-9) and there may be quite a lot of those.
Mayor Pete is trying to maintain political relevance as he aspires to higher office some day. Not quite as bad as the platitudes uttered by Mayor Federico Pena after the ValuJet crash.
(I see alf5071h had the same frightening vision. Hope nobody has fallen into that reversed human factors trap.)
Last edited by xetroV; 11th Jan 2024 at 18:58. Reason: alf5071h
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Can't argue with that.
And, given that that's not the way of removing the door that's provided for, it wouldn't be altogether surprising if it was accompanied by official denials that it was being done at all.
That said, if the lower lock bolts remained in situ, would inadequately-secured hinge bolts allow enough play for the stops to disengage? If not, we're back to square 1 in terms of an explanation for what happened.
And, given that that's not the way of removing the door that's provided for, it wouldn't be altogether surprising if it was accompanied by official denials that it was being done at all.
That said, if the lower lock bolts remained in situ, would inadequately-secured hinge bolts allow enough play for the stops to disengage? If not, we're back to square 1 in terms of an explanation for what happened.
To your question, IMO, the stowed hinge/guide assy offers some significant fore/aft positioning stability to the lower half of the door, but I think its only ever secondary to the 12 mated lugs pushing the entire plug into the seal and recess around the perimeter. The 12 lugs need to be adjusted to some kind of spec. or clearance. Would be helpful to see the MM. The vertical motion is arrested by the top lockbolts, even if the lower ones are missing. Any fore /aft shifting with lower guides detached still seems too little to get past the stop lugs, but obviously the hinge assy would be handy at that point in time.
One could theorize that if the 12 lugs were loose, and the hinges disconnected at lower, cabin pressure could maybe push the plug out away from its perimeter recess, and over time dislodge the stop lugs starting from the bottom, if theres enough clearance of the inside structure to allow it.