Alaska Airlines 737-900 MAX loses a door in-flight out of PDX
The stop pads on the B737-800 entry door are definitely flat - checked them today myself out of curiosilty after reading this thread. They seem to be identical in design to the MAX-9 door plug.
But this raises an important question: was the door plug literally hanging by a thread for the last couple of flights? If so, the theory that a higher differential pressure would have prevented the door plug from exiting the aircraft at higher altitudes (because of increased forces against the stop pads) may be inapplicable. Would the structure surrounding the door plug have survived a sudden pressure equalization if the door plug had blown at, say, FL410?
But this raises an important question: was the door plug literally hanging by a thread for the last couple of flights? If so, the theory that a higher differential pressure would have prevented the door plug from exiting the aircraft at higher altitudes (because of increased forces against the stop pads) may be inapplicable. Would the structure surrounding the door plug have survived a sudden pressure equalization if the door plug had blown at, say, FL410?
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Investigation scope and worries
With both formal and informal aerospace accidents investigation you need a large number of specialisms, viewpoints and scenario views to come to facts, feasible conclusions, and learn. Have to say that after 40 years I personally start to learn more and more from the informal ones, like here on pprune (and the 1-on-1’s via pprune). For me personally the gap between a 30 days prelim and the 365 days (final) report is too long. It would be beneficial to have at least a Half Year or even better Quarterly Factual Update Reports.
I have already shared a few (apparent) lessons from this case at work (and yes I am very careful with that), but have to add to get a confirmation with the intermediate or final report (much) later. Full learning delayed :-(
The biggest issue in my view with this investigation is that the scope of the NTSB investigation is far too specific far too tight.
Next to this specific aircraft accident event investigation there needs to be a much wider one. For example, not to blame but to learn, why did the FAA (and EASA and …) fail to spot the wider cultural issues on the arguably mostly scrutinised aircraft (MAX) program ever. Only starting an NTSB ‘wide one’ after this ‘specific one’ I would rate that as a systemic failure. It will take far too long. Solving this specific one does not solve the wider issue.
In spite of for example the FAA now apparently starting to add hands-on inspections to the paperwork based ones (I had the impression they already did after the two MAX crashes :-0).
A failed culture creates a failed process, and a failed process delivers failing aircraft.
I have already shared a few (apparent) lessons from this case at work (and yes I am very careful with that), but have to add to get a confirmation with the intermediate or final report (much) later. Full learning delayed :-(
The biggest issue in my view with this investigation is that the scope of the NTSB investigation is far too specific far too tight.
Next to this specific aircraft accident event investigation there needs to be a much wider one. For example, not to blame but to learn, why did the FAA (and EASA and …) fail to spot the wider cultural issues on the arguably mostly scrutinised aircraft (MAX) program ever. Only starting an NTSB ‘wide one’ after this ‘specific one’ I would rate that as a systemic failure. It will take far too long. Solving this specific one does not solve the wider issue.
In spite of for example the FAA now apparently starting to add hands-on inspections to the paperwork based ones (I had the impression they already did after the two MAX crashes :-0).
A failed culture creates a failed process, and a failed process delivers failing aircraft.
Last edited by A0283; 14th Feb 2024 at 09:29.
With both formal and informal aerospace accidents investigation you need a large number of specialisms, viewpoints and scenario views to come to facts, feasible conclusions, and learn. Have to say that after 40 years I personally start to learn more and more from the informal ones, like here on pprune (and the 1-on-1’s via pprune). For me personally the gap between a 30 days prelim and the 365 days (final) report is too long. It would be beneficial to have at least a Half Year or even better Quarterly Factual Update Reports.
This Alaska Airlines debacle a shining example as was another a few years ago when a fragment of a SAM missile was identified as the cause of a downed aircraft.
Kudos to all who provide us with such information.
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Scope of investigation
With both formal and informal aerospace accidents investigation you need a large number of specialisms, viewpoints and scenario views to come to facts, feasible conclusions, and learn. Have to say that after 40 years I personally start to learn more and more from the informal ones, like here on pprune (and the 1-on-1’s via pprune). For me personally the gap between a 30 days prelim and the 365 days (final) report is too long. It would be beneficial to have at least a Half Year or even better Quarterly Factual Update Reports.
I have already shared a few (apparent) lessons from this case at work (and yes I am very careful with that), but have to add to get a confirmation with the intermediate or final report (much) later. Full learning delayed :-(
The biggest issue in my view with this investigation is that the scope of the NTSB investigation is far too specific far too tight.
Next to this specific aircraft accident event investigation there needs to be a much wider one. For example, not to blame but to learn, why did the FAA (and EASA and …) fail to spot the wider cultural issues on the arguably mostly scrutinized aircraft (MAX) program ever. Only starting an NTSB ‘wide one’ after this ‘specific one’ I would rate that as a systemic failure. It will take far too long. Solving this specific one does not solve the wider issue.
In spite of for example the FAA now apparently starting to add hands-on inspections to the paperwork based ones (I had the impression they already did after the two MAX crashes :-0).
A failed culture creates a failed process, and a failed process delivers failing aircraft.
I have already shared a few (apparent) lessons from this case at work (and yes I am very careful with that), but have to add to get a confirmation with the intermediate or final report (much) later. Full learning delayed :-(
The biggest issue in my view with this investigation is that the scope of the NTSB investigation is far too specific far too tight.
Next to this specific aircraft accident event investigation there needs to be a much wider one. For example, not to blame but to learn, why did the FAA (and EASA and …) fail to spot the wider cultural issues on the arguably mostly scrutinized aircraft (MAX) program ever. Only starting an NTSB ‘wide one’ after this ‘specific one’ I would rate that as a systemic failure. It will take far too long. Solving this specific one does not solve the wider issue.
In spite of for example the FAA now apparently starting to add hands-on inspections to the paperwork based ones (I had the impression they already did after the two MAX crashes :-0).
A failed culture creates a failed process, and a failed process delivers failing aircraft.
Pegase Driver
Correct . The Investigation unit ( e.g NTSB ) makes recommendations to the regulator who is the only one with the power to implement them (or not.) but the big flaw in the US system is that the FAA is both Regulator and service provider.. In addition the FAA Administrator is politically appointed, and in the US, lobbies have a huge influence on the politics. . Lots of conflict of interest in there.
Now, the NTSB has no actual power to implement changes to prevent or discourage a future event, it can only issue recommendations. It's up to the FAA to determine what - if any - changes are warranted based on those recommendations (or, in rare cases, the US Congress can take action if they don't think the FAA has taken the necessary actions).
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Toyota’s Daihatsu division has stopped vehicle deliveries while it reviews compliance issues. Should Boeing do likewise? IIRC Boeing did stop deliveries of 777s years ago because of quality non compliance
The NTSB is a congressionally mandated, independent agency who oversee all civil aviation accidents and other transportation related accidents. Their main purpose is to investigate the accident, to determine probable cause, and to issue safety recommendations if warranted. Beyond that the FAA handles all other issues. So unless an issue is directly related to, or a contributing factor to the probable cause, the NTSB, in most cases, does not include that issue within its investigative process. Rarely does the NTSB investigate the underlying factors of the accident. That is the job of the FAA.
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Reason for discrepancy of door marking?
The NTSB preliminary report states
while (as reported earlier in this thread) a photograph in some news article shows that the fallen door plug has the marking
which we know is that of another AC delivered later to Alaska.
The NTSB report is void of information on that discrepancy.
Has the reason for that discrepancy surfaced?
The MED plug was then installed and rigged on the fuselage (Spirit AeroSystems Fuselage Line 8789) before it was shipped to Boeing on August 20, 2023.
LINE UNIT : 8799
The NTSB report is void of information on that discrepancy.
Has the reason for that discrepancy surfaced?
CVR. over-written.
I find it hard to believe, that in an age of multiple Gigabyte Memory Cards, that the CVR is limited to the last 2 hours of use. This is surely a political reason, and not just limited by engineering restrictions. Maybe the NTSB needs to recommend longer CVR records.
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The NTSB is a congressionally mandated, independent agency who oversee all civil aviation accidents and other transportation related accidents. Their main purpose is to investigate the accident, to determine probable cause, and to issue safety recommendations if warranted. Beyond that the FAA handles all other issues. So unless an issue is directly related to, or a contributing factor to the probable cause, the NTSB, in most cases, does not include that issue within its investigative process. Rarely does the NTSB investigate the underlying factors of the accident. That is the job of the FAA.
If the FAA may be part causal here … then the NTSB in my view shall include them in their investigation coverage … if the outcome of the investigation is that the FAA is part causal here indeed, then NTSB input should be used by Congress to set that right and return them to ‘a’ gold standard …
Just one aspect:
The fact that the FAA is turning from ‘paper checking’ only, to also perform ‘floor checking’, is a clear indication that a strategic shift is required. This would require Congressional guidance accompanied by focussed funding.
Experience with top to bottom ‘floor checking’, including all levels of paperwork, requires working with multiple experienced disciplines over a period of years. Years at least as much for example as getting yourselves more air traffic controllers because the floor work is a combination of science and art.
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The NTSB had already recommended this (for a long time).
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NTSB
Based on for instance the NTSB report of 24 September 2013, concerning the 1 April 2011 (sic!) B733 accident (manufacturing fault leads to rapid decompression at FL 340, flight SW812), I'd be doubtful to expect a lot more exciting detail or far reaching safety recommendations (if any) in the final NTSB's report on the Alaska door plug accident.
In the "analysis" part of the aforementioned report there's reference to "extremely poor manufacturing technique" and it is mentioned that the "investigation could not determine why the crown skin panel had been replaced or how the poor repair was not identified in the QA process", either at (then still) Boeing Wichita or at Renton. But the report finishes off with: "The National Transportation Safety Board determines that the probable cause of this accident was the improper installation of the fuselage crown skin panel at the S-4L lap joint during the manufacturing process, which resulted in multiple site damage fatigue cracking and eventual failure of the lower skin panel."
fgrieu I doubt if we'll read anything about the door plug swap if this did not take place at Renton, but at Spirit Wichita. Only if the swap happened at Renton it could be connected to the (lack of) records involving the removal and reinstallation of the 4 vertical arrestor bolts, since the preliminary finds that the airframe arrived at Renton with a plug and the 4 bolts in place.
What I find more remarkable is that the preliminary doesn't explicitly refer (I mean factually) to the pigtail around the fwd lower stop brackets in the photo evidently uploaded in Spirit's SAT when discussing the insulation and trim installation following the rivet rework on 19 Sept.
Finally, as regards previous posters in this Alaska thread speculating about what if the door plug would have exited not at FL15 but at cruise, I found an interesting reference in the NTSB SW812 report to an FAA circular which determines that above FL35 in case of an explosive depressurisation event, the "time of useful consciousness" (TUC) is reduced to only 6-9 seconds (the time it takes for oxygen to enter the bloodstream and flow from the lungs to the brain).
Regards
NTSB report SW812
NTSB report SW812
In the "analysis" part of the aforementioned report there's reference to "extremely poor manufacturing technique" and it is mentioned that the "investigation could not determine why the crown skin panel had been replaced or how the poor repair was not identified in the QA process", either at (then still) Boeing Wichita or at Renton. But the report finishes off with: "The National Transportation Safety Board determines that the probable cause of this accident was the improper installation of the fuselage crown skin panel at the S-4L lap joint during the manufacturing process, which resulted in multiple site damage fatigue cracking and eventual failure of the lower skin panel."
fgrieu I doubt if we'll read anything about the door plug swap if this did not take place at Renton, but at Spirit Wichita. Only if the swap happened at Renton it could be connected to the (lack of) records involving the removal and reinstallation of the 4 vertical arrestor bolts, since the preliminary finds that the airframe arrived at Renton with a plug and the 4 bolts in place.
What I find more remarkable is that the preliminary doesn't explicitly refer (I mean factually) to the pigtail around the fwd lower stop brackets in the photo evidently uploaded in Spirit's SAT when discussing the insulation and trim installation following the rivet rework on 19 Sept.
Finally, as regards previous posters in this Alaska thread speculating about what if the door plug would have exited not at FL15 but at cruise, I found an interesting reference in the NTSB SW812 report to an FAA circular which determines that above FL35 in case of an explosive depressurisation event, the "time of useful consciousness" (TUC) is reduced to only 6-9 seconds (the time it takes for oxygen to enter the bloodstream and flow from the lungs to the brain).
Regards
NTSB report SW812
NTSB report SW812
There are certainly more compelling aircraft accidents/incidents to make the case for a 25-hr CVR than ASA1282.
In 2022, a Curtiss-Wright manager stated that, “…until recently, the technology effectively restricted recording capacity to 2 hr.” I find that statement perplexing.
In 2022, a Curtiss-Wright manager stated that, “…until recently, the technology effectively restricted recording capacity to 2 hr.” I find that statement perplexing.
Do Boeing fit the same CVR kit to all 737s, and a software switch is set to either 2hr for US operators and 25hr for European operators, or are 2hr and 25hr CVRs diferent bits of kit?
FYI: That info may surface when the factual report and public docket are released. Once the initial media reports end and the preliminary report is released the NTSB usually don’t release other information until the factual/docket and final are released. However, in some high-profile cases they may release an interim report but it usually doesn’t include detailed info like “line unit numbers” in my experience. That is normally the purpose of the docket.
Usually when the FAA is found to be a contributing factor or an underlying cause, which has happened, there is an existing protocol that addresses this failure within the DOT or congress, and not the NTSB.
If the FAA may be part causal here … then the NTSB in my view shall include them in their investigation coverage … if the outcome of the investigation is that the FAA is part causal here indeed, then NTSB input should be used by Congress to set that right and return them to ‘a’ gold standard ….