6 ms·

The headline is missing an important bit. Boeing knew of the flaw, and sent a letter to airlines about it. In 2011.

rabidonrails 10mo ago
Well yes but Boeing also said it "would not result in a safety of flight condition." There's a lot of gray going on here.
- hahahahhaah 10mo ago
  Yeah saved boeing losing face and sales by requiring all the planes be grounded and fixed. Just eye it up every 5 years, if you want to.
  - itopaloglu83 10mo ago
    And that’s how McDonnell Douglas took over Boeing from the inside and eroded its engineering mindset altogether.
- dralley 10mo ago
  The FAA has not determined that this flaw did lead to a safety of flight condition. Investigation is still ongoing.
- autoexec 10mo ago
  A former air accident investigator who works as an aviation safety consultant said "It's extraordinary that Boeing concluded that a failure of this part would not have safety consequences," and said the report was "disturbing" Doesn't seem like gray to me. It seems a company who has a history of cutting corners and ignoring or downplaying safety problems did exactly that in this case too which resulted in the deaths of many people. UPS made an error here as well in trusting Boeing when they said it wasn't a safety issue and they should have installed the revised bearing assembly out of an abundance of caution, but I don't know much they would have known back in 2011 about the changes at Boeing that prioritized profit over safety following the merger with McDonnell Douglas
  - jacquesm 10mo ago
    I think every company operating Boeing aircraft should have reviewed their stance on Boeing directives in light of MCAS and the aftermath by now. If they did not that is a failure of sorts as well.
    - palmotea 10mo ago
      > I think every company operating Boeing aircraft should have reviewed their stance on Boeing directives in light of MCAS and the aftermath by now. If they did not that is a failure of sorts as well. Actual question: would an airline have the engineering competence to second-guess an airplane manufacturer's engineering guidance? They operate airplanes but don't build them, and I'd assume they'd out of necessity need to trust the manufacturer's judgement.
      - ses1984 10mo ago
        Maybe the airline doesn’t but their insurance company should, if not directly than indirectly.
        nradov 10mo ago
        That's not how it works. Insurers don't have the resources or technical competence to second guess aircraft manufacturer maintenance guidelines.
        ses1984 10mo ago
        When it’s your hundreds of millions of dollars on the line, you go find experts who have the competence needed to do a proper risk analysis.
      - jacquesm 10mo ago
        They certainly have a responsibility towards their passengers that goes beyond their relationship with Boeing. Passengers trust airlines with their lives, with Boeing they have 'just' a business relationship. Airlines have every reason to be skeptical of their supplier even if they do not have the engineering competence to second guess them. They could for instance look through their past communications with the manufacturer and see for themselves which advisories they agree with because for instance they are obviously not safety critical, this would then allow them hire specialists to evaluate the remainder for a second opinion.
- bombcar 10mo ago
  Apparently they expected it to blow up on the ground, so technically the plane wasn't flying yet ...
- somat 10mo ago
  I am wondering what the exact fail mode here is. Because my naive conclusion after looking at the part in question is exactly the same "would not result in a safety of flight condition." if the bearing cracked at the point in question it is going nowhere, the bearing is still captive in its housing. hell it looks like it could have been designed as two pieces and it would work the same. the large bolt is what is holding the engine on. The best I can come up with is that a split bearing causes increased wear on the mounting bracket and nobody noticed for a long time. Anyhow, here is the ntsb update in question https://www.ntsb.gov/investigations/Documents/DCA26MA024%20Investigative%20Update.pdf https://www.ntsb.gov/investigations/Documents/DCA26MA024%20I...
  - jacquesm 10mo ago
    That's indeed a very naive conclusion. Once that bearing is gone the stress that it would normally allow to escape on account of rotation would be directly transferred to the metal around it and to the bolts holding the whole thing in place. Guess what broke first? So if that bearing went that's not quite a smoking gun yet but it would definitely be a step closer to a root cause.
    - ethbr1 10mo ago
      After watching the below video, it's the excess bearing play and thus no-longer-constrained force directions that would seem to be the issue. With a proper tolerance bearing in place, the force is constrained so that other parts are only stressed in directions they're well suited to handle (because the bearing takes the load). Once the bearing develops excess tolerance, you've got a bucking engine that (to your point) is directly loading other parts in unexpected ways/directions, eventually causing failure. The fact that Boeing supposedly modeled this and came up with non-safety critical in the event of bearing breakage... curious how that will turn out.
      - jacquesm 10mo ago
        > The fact that Boeing supposedly modeled this and came up with non-safety critical in the event of bearing breakage... curious how that will turn out. They'd have to show at least one plane with a bearing gone that still flies as intended. I suggest we break one on purpose, put the full complement of Boeing execs on that plane to prove its safety given the alternative of retracting that statement.
- otikik 10mo ago
  What's gray? To me it looks like written proof of incompetence.
- jjk166 10mo ago
  Which may have been a very reasonable conclusion based on what they knew of the issue. The letter sent out reported a split of the bearing race. A split bearing race won't prevent it from supporting the load. It's easily possible that Boeing's simulation of an aircraft operating with a split bearing race was fine. The NTSB investigation found that for this crash, not only did the bearing race crack, but also that the bearing lugs, which hold the bearing in place, were fractured. I don't have access to the original text of the letter Boeing sent out, but based on the NTSB report, it sounds like only the issue with the bearing race was previously identified. The two may very well be related, but that doesn't mean that the lug fractures are an expected result of the race failure - perhaps some contributing factor made the lugs more susceptible than predicted. It also remains possible that the bearing damage is a red herring; the aircraft was nearing the end of its service life and had known structural issues in other parts of the pylon. The fact is that for more than a decade after the bearing race issue was reported, it didn't result in a safety of flight condition. The insinuation that Boeing was deliberately trying to hide or downplay a known issue is simply unwarranted. It would be irresponsible for the NSTB not to mention a known issue that could have potentially been relevant, it's not evidence the issue was improperly handled.
WillPostForFood 10mo ago
FWIW, the MD-11 was designed by McDonnell Douglas, and manufactured by McDonnell Douglas in 1991, before the Boeing merger. A McDonnell Douglas DC-10 failed in a similar way in Chicago in 1979, so it the issue may go way back.
- topspin 10mo ago
  AA Flight 191 in 1979, 273 dead. American Airlines invented their own engine removal procedure using a forklift and damaged a pylon and mounting bracket. The engine ripped off the wing on takeoff.
  - jsr0 10mo ago
    Interestingly, the reason American Airlines was removing the engines (and pylons) in the first place was to replace that same aft bearing. McDonnell-Douglas had found that the aft bearing could wear out sooner than expected and issued a service bulletin requiring replacement. There is mention of it in the AA191 NTSB report[1] and also at Admiral Cloudberg's article on the accident[2]. [1] https://www.ntsb.gov/investigations/AccidentReports/Reports/AAR7917.pdf https://www.ntsb.gov/investigations/AccidentReports/Reports/... [2] https://admiralcloudberg.medium.com/rain-of-fire-falling-the-crash-of-american-airlines-flight-191-e17ffc5369e5 https://admiralcloudberg.medium.com/rain-of-fire-falling-the...
- philipwhiuk 10mo ago
  This would be a better defense if not for the aphorism that "McDonnell-Douglas bought Boeing with Boeing's money"
- sidewndr46 10mo ago
  I'm reasonably certain it was McDonnel Douglas that acquired Boeing with Boeing's own money. Most likely everyone who designed that plane has retired at this point anyways.
  - p_l 10mo ago
    It's commonly trotted out, but the people who spearheaded the disastrous changes including mass outsourcing were Boeing for life - with McD people writing alarming memos about outsourcing goals set for Dreamliner
rootusrootus 10mo ago
That is the critical bit. They knew about it, and we can speculate that their assessment was wrong, but there is no coverup, no scandal. Sometimes engineers are wrong.

Well yes but Boeing also said it "would not result in a safety of flight condition." There's a lot of gray going on here.

hahahahhaah 10mo ago
Yeah saved boeing losing face and sales by requiring all the planes be grounded and fixed. Just eye it up every 5 years, if you want to.
- itopaloglu83 10mo ago
  And that’s how McDonnell Douglas took over Boeing from the inside and eroded its engineering mindset altogether.
dralley 10mo ago
The FAA has not determined that this flaw did lead to a safety of flight condition. Investigation is still ongoing.
autoexec 10mo ago
A former air accident investigator who works as an aviation safety consultant said "It's extraordinary that Boeing concluded that a failure of this part would not have safety consequences," and said the report was "disturbing" Doesn't seem like gray to me. It seems a company who has a history of cutting corners and ignoring or downplaying safety problems did exactly that in this case too which resulted in the deaths of many people. UPS made an error here as well in trusting Boeing when they said it wasn't a safety issue and they should have installed the revised bearing assembly out of an abundance of caution, but I don't know much they would have known back in 2011 about the changes at Boeing that prioritized profit over safety following the merger with McDonnell Douglas
- jacquesm 10mo ago
  I think every company operating Boeing aircraft should have reviewed their stance on Boeing directives in light of MCAS and the aftermath by now. If they did not that is a failure of sorts as well.
  - palmotea 10mo ago
    > I think every company operating Boeing aircraft should have reviewed their stance on Boeing directives in light of MCAS and the aftermath by now. If they did not that is a failure of sorts as well. Actual question: would an airline have the engineering competence to second-guess an airplane manufacturer's engineering guidance? They operate airplanes but don't build them, and I'd assume they'd out of necessity need to trust the manufacturer's judgement.
    - ses1984 10mo ago
      Maybe the airline doesn’t but their insurance company should, if not directly than indirectly.
      - nradov 10mo ago
        That's not how it works. Insurers don't have the resources or technical competence to second guess aircraft manufacturer maintenance guidelines.
        ses1984 10mo ago
        When it’s your hundreds of millions of dollars on the line, you go find experts who have the competence needed to do a proper risk analysis.
    - jacquesm 10mo ago
      They certainly have a responsibility towards their passengers that goes beyond their relationship with Boeing. Passengers trust airlines with their lives, with Boeing they have 'just' a business relationship. Airlines have every reason to be skeptical of their supplier even if they do not have the engineering competence to second guess them. They could for instance look through their past communications with the manufacturer and see for themselves which advisories they agree with because for instance they are obviously not safety critical, this would then allow them hire specialists to evaluate the remainder for a second opinion.
bombcar 10mo ago
Apparently they expected it to blow up on the ground, so technically the plane wasn't flying yet ...
somat 10mo ago
I am wondering what the exact fail mode here is. Because my naive conclusion after looking at the part in question is exactly the same "would not result in a safety of flight condition." if the bearing cracked at the point in question it is going nowhere, the bearing is still captive in its housing. hell it looks like it could have been designed as two pieces and it would work the same. the large bolt is what is holding the engine on. The best I can come up with is that a split bearing causes increased wear on the mounting bracket and nobody noticed for a long time. Anyhow, here is the ntsb update in question https://www.ntsb.gov/investigations/Documents/DCA26MA024%20Investigative%20Update.pdf https://www.ntsb.gov/investigations/Documents/DCA26MA024%20I...
- jacquesm 10mo ago
  That's indeed a very naive conclusion. Once that bearing is gone the stress that it would normally allow to escape on account of rotation would be directly transferred to the metal around it and to the bolts holding the whole thing in place. Guess what broke first? So if that bearing went that's not quite a smoking gun yet but it would definitely be a step closer to a root cause.
  - ethbr1 10mo ago
    After watching the below video, it's the excess bearing play and thus no-longer-constrained force directions that would seem to be the issue. With a proper tolerance bearing in place, the force is constrained so that other parts are only stressed in directions they're well suited to handle (because the bearing takes the load). Once the bearing develops excess tolerance, you've got a bucking engine that (to your point) is directly loading other parts in unexpected ways/directions, eventually causing failure. The fact that Boeing supposedly modeled this and came up with non-safety critical in the event of bearing breakage... curious how that will turn out.
    - jacquesm 10mo ago
      > The fact that Boeing supposedly modeled this and came up with non-safety critical in the event of bearing breakage... curious how that will turn out. They'd have to show at least one plane with a bearing gone that still flies as intended. I suggest we break one on purpose, put the full complement of Boeing execs on that plane to prove its safety given the alternative of retracting that statement.
otikik 10mo ago
What's gray? To me it looks like written proof of incompetence.
jjk166 10mo ago
Which may have been a very reasonable conclusion based on what they knew of the issue. The letter sent out reported a split of the bearing race. A split bearing race won't prevent it from supporting the load. It's easily possible that Boeing's simulation of an aircraft operating with a split bearing race was fine. The NTSB investigation found that for this crash, not only did the bearing race crack, but also that the bearing lugs, which hold the bearing in place, were fractured. I don't have access to the original text of the letter Boeing sent out, but based on the NTSB report, it sounds like only the issue with the bearing race was previously identified. The two may very well be related, but that doesn't mean that the lug fractures are an expected result of the race failure - perhaps some contributing factor made the lugs more susceptible than predicted. It also remains possible that the bearing damage is a red herring; the aircraft was nearing the end of its service life and had known structural issues in other parts of the pylon. The fact is that for more than a decade after the bearing race issue was reported, it didn't result in a safety of flight condition. The insinuation that Boeing was deliberately trying to hide or downplay a known issue is simply unwarranted. It would be irresponsible for the NSTB not to mention a known issue that could have potentially been relevant, it's not evidence the issue was improperly handled.

WillPostForFood 10mo ago

FWIW, the MD-11 was designed by McDonnell Douglas, and manufactured by McDonnell Douglas in 1991, before the Boeing merger. A McDonnell Douglas DC-10 failed in a similar way in Chicago in 1979, so it the issue may go way back.

topspin 10mo ago
AA Flight 191 in 1979, 273 dead. American Airlines invented their own engine removal procedure using a forklift and damaged a pylon and mounting bracket. The engine ripped off the wing on takeoff.
- jsr0 10mo ago
  Interestingly, the reason American Airlines was removing the engines (and pylons) in the first place was to replace that same aft bearing. McDonnell-Douglas had found that the aft bearing could wear out sooner than expected and issued a service bulletin requiring replacement. There is mention of it in the AA191 NTSB report[1] and also at Admiral Cloudberg's article on the accident[2]. [1] https://www.ntsb.gov/investigations/AccidentReports/Reports/AAR7917.pdf https://www.ntsb.gov/investigations/AccidentReports/Reports/... [2] https://admiralcloudberg.medium.com/rain-of-fire-falling-the-crash-of-american-airlines-flight-191-e17ffc5369e5 https://admiralcloudberg.medium.com/rain-of-fire-falling-the...
philipwhiuk 10mo ago
This would be a better defense if not for the aphorism that "McDonnell-Douglas bought Boeing with Boeing's money"
sidewndr46 10mo ago
I'm reasonably certain it was McDonnel Douglas that acquired Boeing with Boeing's own money. Most likely everyone who designed that plane has retired at this point anyways.
- p_l 10mo ago
  It's commonly trotted out, but the people who spearheaded the disastrous changes including mass outsourcing were Boeing for life - with McD people writing alarming memos about outsourcing goals set for Dreamliner

rootusrootus 10mo ago

That is the critical bit. They knew about it, and we can speculate that their assessment was wrong, but there is no coverup, no scandal. Sometimes engineers are wrong.