Alaska Airlines 737-900 MAX loses a door in-flight out of PDX
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
The FAA on that Jan 11 update makes the (to my mind) inaccurate description of the problem: "This investigation is a result of an incident on a Boeing Model 737-9 MAX where it lost a “plug” type passenger door and additional discrepancies." Its a door plug, not a passenger door.
TBC has an opportunity to acknowledge the issues or to obfuscate. The FAA will likely be tolerant of a full and frank response, otherwise it appears to be prepared to apply punitive sanctions for gross non compliance by the TQMS of the manufacturer. It's not a sudden, exceptional failure condition, it has been developing over 28 years, and TBC seems to not be interested in resolving the underlying weaknesses.
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.
And it gets even more complicated ...
Leaving aside the hinge bracket bolts, The Air Current reports here that on the aircraft involved in the incident, Boeing had found on receipt of the fuselage from Spirit that 6 of the 8 bolts securing the rollers to the door surround were loose.
Yet another interesting potential failure mode.
Leaving aside the hinge bracket bolts, The Air Current reports here that on the aircraft involved in the incident, Boeing had found on receipt of the fuselage from Spirit that 6 of the 8 bolts securing the rollers to the door surround were loose.
Yet another interesting potential failure mode.
BBC News: https://www.bbc.co.uk/news/business-67943988
"US official says Boeing jets won't fly until safe ...
"US official says Boeing jets won't fly until safe ...
In their Thursday statement, regulators added that they have informed Boeing that they are conducting an investigation to determine if the aircraft maker failed 'to ensure completed products conformed to its approved design and were in a condition for safe operation.'
'The safety of the flying public, not speed, will determine the timeline for returning the Boeing 737-9 Max to service,' the FAA said.
'The safety of the flying public, not speed, will determine the timeline for returning the Boeing 737-9 Max to service,' the FAA said.
Join Date: Apr 2010
Location: Alexandria VA USA
Posts: 40
Likes: 0
Received 0 Likes
on
0 Posts
And it gets even more complicated ...
Leaving aside the hinge bracket bolts, The Air Current reports here that on the aircraft involved in the incident, Boeing had found on receipt of the fuselage from Spirit that 6 of the 8 bolts securing the rollers to the door surround were loose.
Yet another interesting potential failure mode.
Leaving aside the hinge bracket bolts, The Air Current reports here that on the aircraft involved in the incident, Boeing had found on receipt of the fuselage from Spirit that 6 of the 8 bolts securing the rollers to the door surround were loose.
Yet another interesting potential failure mode.
Join Date: Sep 2020
Location: Texas
Posts: 2
Likes: 0
Received 0 Likes
on
0 Posts
Probably too expensive to plug the doorway from inside the fuselage with the plug being larger than the opening, sealing tighter as the cabin pressure differential increases. Also, plugging an exit to fit in a couple of additional seats is like shortening a runway. Safety is compromised again by the accountants!
Join Date: Aug 2007
Location: Ireland
Posts: 216
Likes: 0
Received 0 Likes
on
0 Posts
The bolts drawn in blue on post 684 hints to a fully threaded bolt, also called a set screw, used for the locking. Which is a lot weaker than a partly threaded actual bolt. This would have been a vulnerability factor when the roller pin regularly hit it on the middle. The sideways or bending strength of a set screw is probably not more than that of a bolt 1 size down.
Is there a picture of the actual "bolt" that is supposed to be used and in the free.
Is there a picture of the actual "bolt" that is supposed to be used and in the free.
Last edited by vikingivesterled; 11th Jan 2024 at 21:38. Reason: Added info.
Join Date: Apr 2015
Location: Under the radar, over the rainbow
Posts: 794
Received 0 Likes
on
0 Posts
https://theaircurrent.com/wp-content...it-anatomy.jpg
Join Date: Dec 2014
Location: Schiphol
Posts: 480
Likes: 0
Received 0 Likes
on
0 Posts
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.
Appears the NTSB is focussing on this specific case … eh aircraft… the answer being for example something like “in this specific aircraft a bolt there and there was probably missing“… might get that in 30 days but would not bet on that…
Appears the NTSB leaves it up to the FAA to investigate the manufacturing and production processes. That would mean the FAA should point out your Unnamed persons. Which looks like the FAA investigating its own oversight…
If manufacturing is causal here, then you would want an independent investigator to investigate that.
I get the feeling that the NTSB is focussing on the aircraft side and not taking its role on the potential causal side of the manufacturing process.
This is why installing a specialist work group centred on manufacturing, is something I tried to suggest earlier in the thread.
If manufacturing turns out to be main cause or strong factor, then, in hindsight, it will appear strange that we got a Meteo WG but not a Manufacturing WG.
Would be interesting to hear other’s views on this.
A new video from Chris Brady and an explanation of the previous error which apparently was also found in the AMM and was the basis for Chris to use.
Thanks to Chris for all the videos and the timely updates.
Thanks to Chris for all the videos and the timely updates.
Join Date: Jan 2024
Location: Naples
Posts: 15
Likes: 0
Received 0 Likes
on
0 Posts
Estimated impact speed of Plug into Horizontal Stabilizer
TV is boring tonight, hence did some math. Worst case assuming plug rotates into highest frontal area condition once ejected (highest plug deceleration).
Calculated in incremement of 10 msec by the miracle of EXCEL. Plug hits H/S leading edge 0,21 sec after ejection with 160 mph speed difference.
Very simplified, no fancy aero., just considering change of drag with speed, only longitudinal.
Energy is 73 kJ.
Source: USA TODAY Plug Height [m] 1,2192 48 [inch]
Source: USA TODAY Plug Width [m] 0,6604 26 [inch]
calc Plug FrontalArea [m^2] 0,81 1248 [inch^2]
estm. cw Plug [-] 1,2
Source: USA TODAY Mass of Plug [kg] 28,6 63 [pounds]
estm. Air Density @ FL160 [kg /m^3] 0,8
Source NY TIMES Aircraft Speed @incident [m/s] 197 440 [mph]
scaled from 73 pic Distance Plug-Horiz.Stab. [m] 9
calc Initial Drag Force on Plug [N] 14965
calc Initial Deceleration of Plug [m/s^2] 523 53,3 [g]
calc Plug speed @ impact with H/S [m/s] 71,5 equals 160 [mph]
calc Energy [kJ] 73,1
Calculated in incremement of 10 msec by the miracle of EXCEL. Plug hits H/S leading edge 0,21 sec after ejection with 160 mph speed difference.
Very simplified, no fancy aero., just considering change of drag with speed, only longitudinal.
Energy is 73 kJ.
Source: USA TODAY Plug Height [m] 1,2192 48 [inch]
Source: USA TODAY Plug Width [m] 0,6604 26 [inch]
calc Plug FrontalArea [m^2] 0,81 1248 [inch^2]
estm. cw Plug [-] 1,2
Source: USA TODAY Mass of Plug [kg] 28,6 63 [pounds]
estm. Air Density @ FL160 [kg /m^3] 0,8
Source NY TIMES Aircraft Speed @incident [m/s] 197 440 [mph]
scaled from 73 pic Distance Plug-Horiz.Stab. [m] 9
calc Initial Drag Force on Plug [N] 14965
calc Initial Deceleration of Plug [m/s^2] 523 53,3 [g]
calc Plug speed @ impact with H/S [m/s] 71,5 equals 160 [mph]
calc Energy [kJ] 73,1
The bolts drawn in blue on post 684 hints to a fully threaded bolt, also called a set screw, used for the locking. Which is a lot weaker than a partly threaded actual bolt. This would have been a vulnerability factor when the roller pin regularly hit it on the middle. The sideways or bending strength of a set screw is probably not more than that of a bolt 1 size down.
Is there a picture of the actual "bolt" that is supposed to be used and in the free.
Is there a picture of the actual "bolt" that is supposed to be used and in the free.
The NTSB said that the cabin pressure controller had gone into Alt mode on 3 occasions. There was no mention of it having had an effect on actual cabin px.
I’ve seen other comments citing this letter as evidence that NOW the FAA is finally dropping the hammer on Boeing. I see the letter as more of a pro forma document. Wasn’t the FAA supposed to have dropped the hammer on Boeing years ago after the MAX/MCAS debacle? Wasn’t Boeing supposed to be under enhanced scrutiny as a consequence of the deferred prosecution agreement?
Reminds me of some dialogue from an old John Landis movie:
Greg: What do you intend to do, sir? Delta’s already on probation.
Dean W: They are?
Greg: Yes, sir.
Dean W: Oh. Then as of this moment, they’re on double secret probation!
Reminds me of some dialogue from an old John Landis movie:
Greg: What do you intend to do, sir? Delta’s already on probation.
Dean W: They are?
Greg: Yes, sir.
Dean W: Oh. Then as of this moment, they’re on double secret probation!
FAA implies its alarm
FAA's letter to Boeing appears (to this SLF/attorney) to reveal a state of alarm within FAA and (despite its total absence of pertinent aviation regulatory knowledge or experience) perhaps the Secretary's office as well.
Why? Because FAA's letter contains no reference whatsoever, let alone any citation, to statutory or administrative regulation provisions which specifically authorize such an investigatory process in a situation of this type. In the aftermath of the first and then second MAX accidents, there certainly were formal investigations by the Inspector General. IIRC the IG documents carried heavy, definitive citations to its authority to investigate. This letter simply announces the inquiry. Perhaps there is some unspecified general authority for this inquiry - if there is, I'll both be surprised and corrected.
I am emphatically not making any suggestion that the inquiry is improper. But it strongly suggests a case of the FAA "wingin' it." Consider also -
Administrative processes in the federal interagency always are spelled out in detail; the time frames for actions to be taken such as submitting filings, the types of information that can be requested of the responding party, any rights of confidentiality protection, and many more subjects. In this instance, however, the entire section describing how this investigation will be conducted reads like it was crafted from whole cloth. Or ad hoc in legal terms. (I'm stating more of an impression based on experience rather than a specifically provable point.)
Though Mech Engr no doubt is correct that the overall situation would benefit from a thorough report at 30 days from NTSB, I seriously doubt such a significantly comprehensive inquiry will be condcuted by the Board or that at 30 days more than facts of the occurence itself will be reported. Even if the jurisdictional line between FAA and NTSB was open to flexibility before the letter announcing FAA's inquiry, the marker has been set down now.
What this all means for FAA funding, and the still-pending FAA reauthorization legislation....what a mess, is about all that emerges at this point. .
Why? Because FAA's letter contains no reference whatsoever, let alone any citation, to statutory or administrative regulation provisions which specifically authorize such an investigatory process in a situation of this type. In the aftermath of the first and then second MAX accidents, there certainly were formal investigations by the Inspector General. IIRC the IG documents carried heavy, definitive citations to its authority to investigate. This letter simply announces the inquiry. Perhaps there is some unspecified general authority for this inquiry - if there is, I'll both be surprised and corrected.
I am emphatically not making any suggestion that the inquiry is improper. But it strongly suggests a case of the FAA "wingin' it." Consider also -
Administrative processes in the federal interagency always are spelled out in detail; the time frames for actions to be taken such as submitting filings, the types of information that can be requested of the responding party, any rights of confidentiality protection, and many more subjects. In this instance, however, the entire section describing how this investigation will be conducted reads like it was crafted from whole cloth. Or ad hoc in legal terms. (I'm stating more of an impression based on experience rather than a specifically provable point.)
Though Mech Engr no doubt is correct that the overall situation would benefit from a thorough report at 30 days from NTSB, I seriously doubt such a significantly comprehensive inquiry will be condcuted by the Board or that at 30 days more than facts of the occurence itself will be reported. Even if the jurisdictional line between FAA and NTSB was open to flexibility before the letter announcing FAA's inquiry, the marker has been set down now.
What this all means for FAA funding, and the still-pending FAA reauthorization legislation....what a mess, is about all that emerges at this point. .