5 ms·

This plane appears to be a (sorta) flying dumpster fire rushed to market against Airbus with tragic consequences. One design flaw after another is MAX failure.

by kjar 7y ago

dsfyu404ed 7y ago
The industry is pretty homogeneous and somewhat of a revolving door between the few OEMs. What are the odds that the code on this plane is orders of magnitude worse (in terms of code quality) than every other similar bit of code in the sky? Edit. I should have to say this but I'm not defending Boeing here. I'm saying it's not at al unforeseeable that the other planes, even ones by other manufacturers are just as bad. Clearly they thought nothing was abnormal about this one until it started falling out of the sky. I see this kind of like diesel-gate. If one of them is cheating they're probably all cheating.
- closetohome 7y ago
  Or conversely what are the odds that the others have similar undiscovered or undisclosed issues?
  - ls612 7y ago
    Fairly low, given that every other type in widespread service has been flying much longer than the MAX with a very good safety record
    - BuildTheRobots 7y ago
      And Boeing do have form when it comes to software. https://www.engadget.com/2015/05/01/boeing-787-dreamliner-software-bug/ https://www.engadget.com/2015/05/01/boeing-787-dreamliner-so...
- caf 7y ago
  Upgrades to the 737 do have a particularly constrained design space, though (due to the oft-mentioned very low ground clearance).
  - chrisseaton 7y ago
    Why can’t they change the ground clearance and remove the constraint?
    - supergauntlet 7y ago
      The engines on the original 737 design were quite small by modern standards, and the wings were low as well. As such there aren't really a ton of places to put new, larger engines. They basically have to be placed further forward and higher up. This means the pitch moment created by throttling up/down is different on different versions of the 737, which is what required the MCAS device in the first place - they were trying to make sure the 737 MAX flew the same as previous models.
      - chrisseaton 7y ago
        I think you’re just repeating the impact of the low ground clearance, rather than explaining why there still has to be low ground clearance. You’ve said they can’t have larger engines because ground clearance is low... we already know that... but why must ground clearance be low?
        supergauntlet 7y ago
        Ah, you mean why did they originally do it? Sorry, I misunderstood. The original reason was that the 737 was designed that way so that it could be boarded with just stairs instead of a skybridge: https://simpleflying.com/737s-low-to-the-ground/ https://simpleflying.com/737s-low-to-the-ground/ This was super helpful to small carriers at the time, but as time has gone on it's caused problems.
        deleted 7y ago
- makomk 7y ago
  It's worse than other such planes. For instance, the accident on Qantas Flight 72 is superficially similar - faulty data caused the Airbus A330's flight computer to ignore pilot input and abruptly pitch down, injuring a number of passengers - but it really wasn't. The Airbus engineers knew that angle-of-attack sensors fail, so unlike Boeing they designed their system to compare the input from multiple AOA sensors and ignore bogus data. Unfortunately, that comparison algorithm had a flaw - it got confused when it received spikes of invalid data with a certain timing pattern and erroniously used the invalid data. That pattern shouldn't have been possible. No-one has been able to figure out any possible cause for it even in retrospect, and they certainly didn't anticipate it. However, the engineers designing the system did realise that the flight computers could have subtle bugs triggered by specific data timing - so not only did every flight computer have a monitoring channel running independently-written code checking its calculations, that monitoring channel was intentionally not synchronized with the main channel or any other flight computers. This meant every time one of the flight computers acted on bogus data and forcibly pitched down, the monitoring channel calculated values so different that the fault detection disabled its ability to do so within a few seconds. The maximum allowed authority and the altitude at which the system was enabled were also much more carefully restricted than MCAS, so it couldn't take such erroneous actions in situtations where the pilot might be unable to recover. Combine the two safeguards, and something like Qantas Flight 72 with a few passenger injuries but no crash was pretty close to the worst-case scenario that could be caused by this weird and incredibly unlucky issue.
  - cjbprime 7y ago
    > That pattern shouldn't have been possible Huh, this is new to me. I thought it was simply that two sensors failed, and their failed values outvoted the correct value in the quorum vote with the third sensor. What's the mystery about?
    - bronson 7y ago
      Section 5.3: https://www.atsb.gov.au/media/3532398/ao2008070.pdf#page225 https://www.atsb.gov.au/media/3532398/ao2008070.pdf#page225 A microprocessor failed and output corrupted data.
- notatoad 7y ago
  My instinct is that you're probably correct, and most planes are probably riddled with similar problems and would look bad if they came under the same scrutiny as the 737 Max is currently under. For example, I remember after the 787 was launched there was a few stories in the press about the batteries catching fire mid-flight, but it turned out the designers and engineers had accounted for that possibility and it wasn't really a big deal. They've improved the batteries, but it didn't actually hurt anybody. However, the problem with the max seems to be that instead of designing for failure - assuming that critical systems might fail and the plane should recover gracefully from the failure of most internal systems - they seem to have designed for success, and made the assumption that no part of the plane will ever fail. And that's obviously not realistic, and we're seeing the consequences of it here.
  - vkou 7y ago
    > My instinct is that you're probably correct, and most planes are probably riddled with similar problems and would look bad if they came under the same scrutiny as the 737 Max is currently under. The 737 MAX only looks bad because it's track record so far is that it's a death trap.
  - CaptainZapp 7y ago
    I remember after the 787 was launched there was a few stories in the press about the batteries catching fire mid-flight, but it turned out the designers and engineers had accounted for that possibility and it wasn't really a big deal. It was a huge deal and the plane was grounded for three month due to those battery fires. Originally the engineers did not account for battery fires and needed to refit a compartment to seal the batteries in case a fire occurs. Luckily it was either on approach, or they could emergency land the plane when the problem occured. A burning lithium battery in a flying plane is one of the worst imaginable scenarios you can encounter during a flight and is a fucking big deal. Edited to add : https://en.wikipedia.org/wiki/Boeing_787_Dreamliner_battery_problems https://en.wikipedia.org/wiki/Boeing_787_Dreamliner_battery_...
  - rsynnott 7y ago
    > My instinct is that you're probably correct, and most planes are probably riddled with similar problems and would look bad if they came under the same scrutiny as the 737 Max is currently under. 0.5% of all 737 MAXes which exist have killed everyone on board. No other mass market production airliner in recent history has that sort of record, AFAIK.

This plane appears to be a (sorta) flying dumpster fire rushed to market against Airbus with tragic consequences. One design flaw after another is MAX failure.

by kjar 7y ago

This plane appears to be a (sorta) flying dumpster fire rushed to market against Airbus with tragic consequences. One design flaw after another is MAX failure.

dsfyu404ed 7y ago

The industry is pretty homogeneous and somewhat of a revolving door between the few OEMs. What are the odds that the code on this plane is orders of magnitude worse (in terms of code quality) than every other similar bit of code in the sky? Edit. I should have to say this but I'm not defending Boeing here. I'm saying it's not at al unforeseeable that the other planes, even ones by other manufacturers are just as bad. Clearly they thought nothing was abnormal about this one until it started falling out of the sky. I see this kind of like diesel-gate. If one of them is cheating they're probably all cheating.

closetohome 7y ago
Or conversely what are the odds that the others have similar undiscovered or undisclosed issues?
- ls612 7y ago
  Fairly low, given that every other type in widespread service has been flying much longer than the MAX with a very good safety record
  - BuildTheRobots 7y ago
    And Boeing do have form when it comes to software. https://www.engadget.com/2015/05/01/boeing-787-dreamliner-software-bug/ https://www.engadget.com/2015/05/01/boeing-787-dreamliner-so...
caf 7y ago
Upgrades to the 737 do have a particularly constrained design space, though (due to the oft-mentioned very low ground clearance).
- chrisseaton 7y ago
  Why can’t they change the ground clearance and remove the constraint?
  - supergauntlet 7y ago
    The engines on the original 737 design were quite small by modern standards, and the wings were low as well. As such there aren't really a ton of places to put new, larger engines. They basically have to be placed further forward and higher up. This means the pitch moment created by throttling up/down is different on different versions of the 737, which is what required the MCAS device in the first place - they were trying to make sure the 737 MAX flew the same as previous models.
    - chrisseaton 7y ago
      I think you’re just repeating the impact of the low ground clearance, rather than explaining why there still has to be low ground clearance. You’ve said they can’t have larger engines because ground clearance is low... we already know that... but why must ground clearance be low?
      - supergauntlet 7y ago
        Ah, you mean why did they originally do it? Sorry, I misunderstood. The original reason was that the 737 was designed that way so that it could be boarded with just stairs instead of a skybridge: https://simpleflying.com/737s-low-to-the-ground/ https://simpleflying.com/737s-low-to-the-ground/ This was super helpful to small carriers at the time, but as time has gone on it's caused problems.
        deleted 7y ago
makomk 7y ago
It's worse than other such planes. For instance, the accident on Qantas Flight 72 is superficially similar - faulty data caused the Airbus A330's flight computer to ignore pilot input and abruptly pitch down, injuring a number of passengers - but it really wasn't. The Airbus engineers knew that angle-of-attack sensors fail, so unlike Boeing they designed their system to compare the input from multiple AOA sensors and ignore bogus data. Unfortunately, that comparison algorithm had a flaw - it got confused when it received spikes of invalid data with a certain timing pattern and erroniously used the invalid data. That pattern shouldn't have been possible. No-one has been able to figure out any possible cause for it even in retrospect, and they certainly didn't anticipate it. However, the engineers designing the system did realise that the flight computers could have subtle bugs triggered by specific data timing - so not only did every flight computer have a monitoring channel running independently-written code checking its calculations, that monitoring channel was intentionally not synchronized with the main channel or any other flight computers. This meant every time one of the flight computers acted on bogus data and forcibly pitched down, the monitoring channel calculated values so different that the fault detection disabled its ability to do so within a few seconds. The maximum allowed authority and the altitude at which the system was enabled were also much more carefully restricted than MCAS, so it couldn't take such erroneous actions in situtations where the pilot might be unable to recover. Combine the two safeguards, and something like Qantas Flight 72 with a few passenger injuries but no crash was pretty close to the worst-case scenario that could be caused by this weird and incredibly unlucky issue.
- cjbprime 7y ago
  > That pattern shouldn't have been possible Huh, this is new to me. I thought it was simply that two sensors failed, and their failed values outvoted the correct value in the quorum vote with the third sensor. What's the mystery about?
  - bronson 7y ago
    Section 5.3: https://www.atsb.gov.au/media/3532398/ao2008070.pdf#page225 https://www.atsb.gov.au/media/3532398/ao2008070.pdf#page225 A microprocessor failed and output corrupted data.
notatoad 7y ago
My instinct is that you're probably correct, and most planes are probably riddled with similar problems and would look bad if they came under the same scrutiny as the 737 Max is currently under. For example, I remember after the 787 was launched there was a few stories in the press about the batteries catching fire mid-flight, but it turned out the designers and engineers had accounted for that possibility and it wasn't really a big deal. They've improved the batteries, but it didn't actually hurt anybody. However, the problem with the max seems to be that instead of designing for failure - assuming that critical systems might fail and the plane should recover gracefully from the failure of most internal systems - they seem to have designed for success, and made the assumption that no part of the plane will ever fail. And that's obviously not realistic, and we're seeing the consequences of it here.
- vkou 7y ago
  > My instinct is that you're probably correct, and most planes are probably riddled with similar problems and would look bad if they came under the same scrutiny as the 737 Max is currently under. The 737 MAX only looks bad because it's track record so far is that it's a death trap.
- CaptainZapp 7y ago
  I remember after the 787 was launched there was a few stories in the press about the batteries catching fire mid-flight, but it turned out the designers and engineers had accounted for that possibility and it wasn't really a big deal. It was a huge deal and the plane was grounded for three month due to those battery fires. Originally the engineers did not account for battery fires and needed to refit a compartment to seal the batteries in case a fire occurs. Luckily it was either on approach, or they could emergency land the plane when the problem occured. A burning lithium battery in a flying plane is one of the worst imaginable scenarios you can encounter during a flight and is a fucking big deal. Edited to add : https://en.wikipedia.org/wiki/Boeing_787_Dreamliner_battery_problems https://en.wikipedia.org/wiki/Boeing_787_Dreamliner_battery_...
- rsynnott 7y ago
  > My instinct is that you're probably correct, and most planes are probably riddled with similar problems and would look bad if they came under the same scrutiny as the 737 Max is currently under. 0.5% of all 737 MAXes which exist have killed everyone on board. No other mass market production airliner in recent history has that sort of record, AFAIK.