8 ms·

Boeing discloses a new problem with the 787 Dreamliner

deleted 5y ago
[deleted]
WalterBright 5y ago
What's peculiar about this is the FAA says it's not a safety problem. So why is it intervening? As far as I can tell, the problem is the gap between the bulkhead and the fuselage is larger than spec. This means that it'll take more airflow to pressurize the cabin. There are always going to be leaks. The idea is that if all the joins are at the adverse end of the tolerance, meaning more air leaks, there must be enough pressurization air to keep it pressurized. But this is rarely the case, so one part being larger than spec should not cause a problem. Parts get delivered out of spec sometimes, and they get bounced to engineering to evaluate if the design as a whole will still work. I.e. it shouldn't actually be a problem unless the other joins are near the limits of their tolerances. So, what's missing from CNN's reporting is why they are demanding a rework. The local newspaper, which should have a better handle on the situation, doesn't do any better at reporting this.
- WalterBright 5y ago
  Let's put it another way. Suppose you've got a gearbox, with a shaft in it, and a stack of parts on the shaft. The shaft with its parts must fit in the gearbox. The gearbox has a max and min size, and each part has a max and min size. The engineer divides up the tolerances so that if they are all at max size, and the gearbox housing is at min size, the parts will fit. Now, if a gear comes back from the manufacturer larger than its max size, but enough of the other parts are not near their max size, the stack will still fit and it's ok. (But engineering still has to approve the fit.) This is not in any way a crisis. It simply costs extra money because the out-of-spec part gets bounced to engineering for review. Yes, I did these exact calculations on the 757 stab trim gearbox.
  - DoingIsLearning 5y ago
    TIL Walter Bright is actually an Aerospace Engineer. I had always assumed that (as a compiler guru) you had a CS background. :)
    - throw0101a 5y ago
      > Bright is the son of the air force pilot Charles D. Bright.[4][5] Bright graduated from Caltech in 1979 with a Bachelor of Science in aerospace engineering.[6] * https://en.wikipedia.org/wiki/Walter_Bright https://en.wikipedia.org/wiki/Walter_Bright
    - amelius 5y ago
      I'm guessing that the CS stuff is more intellectually challenging.
      - JshWright 5y ago
        Why would you guess that?
        deleted 5y ago
        [deleted]
      - ta988 5y ago
        If you have friends in mechanical engineering, ask them to join you on a visit day at their workplace or any other place with engineering. That will change your mind.
        okprod 5y ago
        When I was at Stevens everyone piled into CompEng and EE, kind of looking down on ME (and CS actually). To this day my ME friends are some of the smartest, coolest people I know.
        deleted 5y ago
- mhandley 5y ago
  My understanding is that it's not about airflow, but about unplanned for localized stresses rather than having them distributed evenly. This means the joint does not meet limit load requirements. While it's not so bad it could immediately structurally fail under expected loads, over time the stress concentration could weaken the structure at those points, leading to premature failure or more likely, significantly shorter service life than expected.
  - WalterBright 5y ago
    The FAA said it wasn't a safety issue. Not meeting limit load requirements is a safety issue. Though I wouldn't be surprised if the CNN reporter got it all bollixed up. I wouldn't take anything seriously from CNN.
    - mhandley 5y ago
      If it is the issues from last year, this article has a lot more detail: https://seekingalpha.com/article/4374235-boeing-dreamliner-manufacturing-nightmare https://seekingalpha.com/article/4374235-boeing-dreamliner-m... As I understood it, there are two issues, neither of which is a problem by itself, but if they occur simultaneously, it would not meet limit load requirements. But maybe CNN is reporting on another new issue - hard to tell.
      - mhandley 5y ago
        It looks like this isn't exactly the issues from last year, but is a new related issue. This Seattle Times article has slightly more detail: https://www.seattletimes.com/business/boeing-aerospace/a-new-787-dreamliner-manufacturing-flaw-will-prolong-boeing-delivery-halt/ https://www.seattletimes.com/business/boeing-aerospace/a-new... Last year's issue related to joints around the rear pressure bulkhead. This article indicates the new issue is a similar problem related to the forward pressure bulkhead.
- altrus 5y ago
  > There are always going to be leaks. As this seems to be something that's given quite a bit of thought, do you have an idea on what the maximum diameter hole through the fuselage to safely maintain sufficient cabin pressure during cruise flight at, say, PL390? More specifically, what's the maximum rate of pressurization that the cabin pressurization system is designed to support?
  - WalterBright 5y ago
    I have no idea, as I didn't work with the tin benders (structures guys). But I do know that there can be a hole the size of a quarter and nobody will notice a pressure drop. You're not going to knock an airliner down by punching holes in the fuselage, either (some people think a bullet hole will cause it to pop like a balloon, nothing of the sort will happen).
- mannykannot 5y ago
  Perhaps “no immediate threat to flight safety” just means that no aircraft with the defect have been delivered or are in service? The phrase "Boeing said 787 planes already in service do not need to be grounded" kind-of implies that there are aircraft with this defect in service, but it need not necessarily do so.
- jsmith45 5y ago
  I think this (the FAA involvement) stems from the previous rear fuselage issues, which was a safety issue, and the FAA is still directly overseeing that issue. It sounds like the FAA have not restored Boeing's delegated authority for final airworthiness sign-off on new 787s due to not having accepting a new inspection plan for that issue yet. That would would explain why the FAA remains involved on an issue it does not consider to be a safety concern, especially as it implies there may be even more quality control issues than previously realized.
mhandley 5y ago
Is this a new issue, or just an update on the problem fastening the fuselage barrel sections together that was identified last year? This article has a lot more detail on that problem: https://theaircurrent.com/aviation-safety/boeing-pulls-eight-787s-from-service-over-structural-issue/ https://theaircurrent.com/aviation-safety/boeing-pulls-eight...
8eye 5y ago
i remember listening to a lecture on this in my business class before all these issues, we watch a video on outsourcing and how this is the first of their planes that used an advanced supply management system to outsource. traditionally boeing did most of their major sourcing from mainly the united states, the united states has some of the strictest air safety laws in the world so previously it was nearly impossible to source overseas due to supply chain parts reliability. guess that is still the case then
- WalterBright 5y ago
  Back on the 757, Boeing outsourced a lot of subassemblies to Japanese companies. We engineers liked them, as they produced very, very good parts. Though personally I liked Saginaw Gear the best, as they did the forgings for the stab trim jackscrew, and made the best of the best.
  - post_break 5y ago
    Can you share what makes forged parts better than others? Wouldn’t it simply be better molds or finishing I suppose? I’m only familiar with forged gun parts and even the cheapest forged parts look and function as good as the expensive ones, but then again going bang is easier than keeping people in the air through crazy stresses and heat and cool cycles.
    - mikewarot 5y ago
      Forging orients the grain structure of the metal in a predictable manner. It also helps remove voids. Generally, a forged part is going to be free of the voids and surface defects of a casting, and waste less material than cutting from an rolled or extruded piece of stock.
      - post_break 5y ago
        I understand what forging is, I was just asking what made their forging better than others is all.
gumby 5y ago
This article is terrible. Are these problems specific to the problem-plagued 787-10 or 787s in general (all models of which have had issues)? Is this specific to models built in South Carolina? I have read some Asian airlines are specifying Washington construction only. Any business reporter (not specific to aviation) who has covered Boeing in the last few years would know that these two questions would explain if this is bad or terrible for Boeing.
myrandomcomment 5y ago
So pre-Covid I would fly 160-200k KM per year. I loved the 787. The higher humility and cabin pressurization along with the larger windows makes the flight so much better.

deleted 5y ago

[deleted]

What's peculiar about this is the FAA says it's not a safety problem. So why is it intervening? As far as I can tell, the problem is the gap between the bulkhead and the fuselage is larger than spec. This means that it'll take more airflow to pressurize the cabin. There are always going to be leaks. The idea is that if all the joins are at the adverse end of the tolerance, meaning more air leaks, there must be enough pressurization air to keep it pressurized. But this is rarely the case, so one part being larger than spec should not cause a problem. Parts get delivered out of spec sometimes, and they get bounced to engineering to evaluate if the design as a whole will still work. I.e. it shouldn't actually be a problem unless the other joins are near the limits of their tolerances. So, what's missing from CNN's reporting is why they are demanding a rework. The local newspaper, which should have a better handle on the situation, doesn't do any better at reporting this.

WalterBright 5y ago
Let's put it another way. Suppose you've got a gearbox, with a shaft in it, and a stack of parts on the shaft. The shaft with its parts must fit in the gearbox. The gearbox has a max and min size, and each part has a max and min size. The engineer divides up the tolerances so that if they are all at max size, and the gearbox housing is at min size, the parts will fit. Now, if a gear comes back from the manufacturer larger than its max size, but enough of the other parts are not near their max size, the stack will still fit and it's ok. (But engineering still has to approve the fit.) This is not in any way a crisis. It simply costs extra money because the out-of-spec part gets bounced to engineering for review. Yes, I did these exact calculations on the 757 stab trim gearbox.
- DoingIsLearning 5y ago
  TIL Walter Bright is actually an Aerospace Engineer. I had always assumed that (as a compiler guru) you had a CS background. :)
  - throw0101a 5y ago
    > Bright is the son of the air force pilot Charles D. Bright.[4][5] Bright graduated from Caltech in 1979 with a Bachelor of Science in aerospace engineering.[6] * https://en.wikipedia.org/wiki/Walter_Bright https://en.wikipedia.org/wiki/Walter_Bright
  - amelius 5y ago
    I'm guessing that the CS stuff is more intellectually challenging.
    - JshWright 5y ago
      Why would you guess that?
      - deleted 5y ago
        [deleted]
    - ta988 5y ago
      If you have friends in mechanical engineering, ask them to join you on a visit day at their workplace or any other place with engineering. That will change your mind.
      - okprod 5y ago
        When I was at Stevens everyone piled into CompEng and EE, kind of looking down on ME (and CS actually). To this day my ME friends are some of the smartest, coolest people I know.
        deleted 5y ago
mhandley 5y ago
My understanding is that it's not about airflow, but about unplanned for localized stresses rather than having them distributed evenly. This means the joint does not meet limit load requirements. While it's not so bad it could immediately structurally fail under expected loads, over time the stress concentration could weaken the structure at those points, leading to premature failure or more likely, significantly shorter service life than expected.
- WalterBright 5y ago
  The FAA said it wasn't a safety issue. Not meeting limit load requirements is a safety issue. Though I wouldn't be surprised if the CNN reporter got it all bollixed up. I wouldn't take anything seriously from CNN.
  - mhandley 5y ago
    If it is the issues from last year, this article has a lot more detail: https://seekingalpha.com/article/4374235-boeing-dreamliner-manufacturing-nightmare https://seekingalpha.com/article/4374235-boeing-dreamliner-m... As I understood it, there are two issues, neither of which is a problem by itself, but if they occur simultaneously, it would not meet limit load requirements. But maybe CNN is reporting on another new issue - hard to tell.
    - mhandley 5y ago
      It looks like this isn't exactly the issues from last year, but is a new related issue. This Seattle Times article has slightly more detail: https://www.seattletimes.com/business/boeing-aerospace/a-new-787-dreamliner-manufacturing-flaw-will-prolong-boeing-delivery-halt/ https://www.seattletimes.com/business/boeing-aerospace/a-new... Last year's issue related to joints around the rear pressure bulkhead. This article indicates the new issue is a similar problem related to the forward pressure bulkhead.
altrus 5y ago
> There are always going to be leaks. As this seems to be something that's given quite a bit of thought, do you have an idea on what the maximum diameter hole through the fuselage to safely maintain sufficient cabin pressure during cruise flight at, say, PL390? More specifically, what's the maximum rate of pressurization that the cabin pressurization system is designed to support?
- WalterBright 5y ago
  I have no idea, as I didn't work with the tin benders (structures guys). But I do know that there can be a hole the size of a quarter and nobody will notice a pressure drop. You're not going to knock an airliner down by punching holes in the fuselage, either (some people think a bullet hole will cause it to pop like a balloon, nothing of the sort will happen).
mannykannot 5y ago
Perhaps “no immediate threat to flight safety” just means that no aircraft with the defect have been delivered or are in service? The phrase "Boeing said 787 planes already in service do not need to be grounded" kind-of implies that there are aircraft with this defect in service, but it need not necessarily do so.
jsmith45 5y ago
I think this (the FAA involvement) stems from the previous rear fuselage issues, which was a safety issue, and the FAA is still directly overseeing that issue. It sounds like the FAA have not restored Boeing's delegated authority for final airworthiness sign-off on new 787s due to not having accepting a new inspection plan for that issue yet. That would would explain why the FAA remains involved on an issue it does not consider to be a safety concern, especially as it implies there may be even more quality control issues than previously realized.

mhandley 5y ago

Is this a new issue, or just an update on the problem fastening the fuselage barrel sections together that was identified last year? This article has a lot more detail on that problem: https://theaircurrent.com/aviation-safety/boeing-pulls-eight-787s-from-service-over-structural-issue/ https://theaircurrent.com/aviation-safety/boeing-pulls-eight...

8eye 5y ago

i remember listening to a lecture on this in my business class before all these issues, we watch a video on outsourcing and how this is the first of their planes that used an advanced supply management system to outsource. traditionally boeing did most of their major sourcing from mainly the united states, the united states has some of the strictest air safety laws in the world so previously it was nearly impossible to source overseas due to supply chain parts reliability. guess that is still the case then

WalterBright 5y ago
Back on the 757, Boeing outsourced a lot of subassemblies to Japanese companies. We engineers liked them, as they produced very, very good parts. Though personally I liked Saginaw Gear the best, as they did the forgings for the stab trim jackscrew, and made the best of the best.
- post_break 5y ago
  Can you share what makes forged parts better than others? Wouldn’t it simply be better molds or finishing I suppose? I’m only familiar with forged gun parts and even the cheapest forged parts look and function as good as the expensive ones, but then again going bang is easier than keeping people in the air through crazy stresses and heat and cool cycles.
  - mikewarot 5y ago
    Forging orients the grain structure of the metal in a predictable manner. It also helps remove voids. Generally, a forged part is going to be free of the voids and surface defects of a casting, and waste less material than cutting from an rolled or extruded piece of stock.
    - post_break 5y ago
      I understand what forging is, I was just asking what made their forging better than others is all.

gumby 5y ago

This article is terrible. Are these problems specific to the problem-plagued 787-10 or 787s in general (all models of which have had issues)? Is this specific to models built in South Carolina? I have read some Asian airlines are specifying Washington construction only. Any business reporter (not specific to aviation) who has covered Boeing in the last few years would know that these two questions would explain if this is bad or terrible for Boeing.

myrandomcomment 5y ago

So pre-Covid I would fly 160-200k KM per year. I loved the 787. The higher humility and cabin pressurization along with the larger windows makes the flight so much better.