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The issue is (from what I understand as layman) that to avoid recertification they kept their old computer hardware from earlier 737 generations, and added more

The issue is (from what I understand as layman) that to avoid recertification they kept their old computer hardware from earlier 737 generations, and added more and more tasks to do for it. https://www.nytimes.com/2019/06/26/business/boeing-737-max-faa-test.html https://www.nytimes.com/2019/06/26/business/boeing-737-max-f... (somewhere in the middle: "The issue discovered last week is linked to the data-processing speed of a specific flight control computer chip, according to the two people with knowledge of the matter. In the test, the F.A.A. pilot encountered delays in executing a crucial step required to stabilize an aircraft." )

jacobush 7y ago
That's surreal - avionics should run on hard real time. (Whether it's offline scheduled and thus "impossible" to miss a deadline, or if it's "soft" realtime and merely testing ensures this, is not the important part. The important part is that it should never miss a deadline.)
- raverbashing 7y ago
  I can understand it looks weird but it isn't. A faster processor has no more real time guarantees than a slower processor from the 80s Of course, the faster one can do more stuff in less time, but for flying an airplane (or going to the moon) the amount of computing power needed is much less than people imagine. The issue here is adding more computing into an aging platform. But there's nothing inherently wrong into using an older platform into the flight computer. Now I'm not sure if for certification purposes they would be allowed to replace it with modern hardware but just keeping the functionality the same, I believe the answer would be yes, that they are allowed (but they probably didn't want to rewrite the sw and recertify the hw)
  - wiz21c 7y ago
    is it me or the certification looks at the hardware but not at the software ?
    - raverbashing 7y ago
      Certification mostly looks at the behaviour, how you get there is your IP for the most part For example, the regulator doesn't care (much) how you built your wing, but it does care that's able to withstand 150% of the maximum expected forces. You can have parts done by different manufacturers (but to the same spec) and this is sometimes done on purpose in redundancy settings so that unknown bugs in one model are less likely to show up in a different model.
  - jacobush 7y ago
    Processing has very little to do with hitting realtime deadlines. Either you do or you don’t. In fact, sometimes faster CPUs are worse for realtime because their latency can be worse.
antihero 7y ago
> to avoid recertification they kept their old computer hardware from earlier 737 generations, This is unbelievably fucked
- adrianN 7y ago
  No, it's not. Certification is an extremely expensive process with dubious benefits for safety. Why would you change hardware that has worked fine if it can fulfill your requirements?
  - vageli 7y ago
    > No, it's not. Certification is an extremely expensive process with dubious benefits for safety. Why would you change hardware that has worked fine if it can fulfill your requirements? Is it fair to say the hardware is fulfilling the requirements though?
  - freehunter 7y ago
    Because it obviously did not work fine and does not fulfill the requirements. What seems to have dubious benefits for safety is lying to the regulators and shoehorning new processes into old technology. Because hundreds of people have died from that exact thing, just on this one airplane.
    - adrianN 7y ago
      The airplanes didn't crash because the computer was too slow. They crashed because safety critical data was read from a sensor without redundancies.
      - aurelwu 7y ago
        But now during simulations test pilots apparently found situations where the computer was too slow to handle their input in adequate time. So while the crash was not the caused by this problem, there seems to be a problem.
  - 7y ago

jacobush 7y ago

That's surreal - avionics should run on hard real time. (Whether it's offline scheduled and thus "impossible" to miss a deadline, or if it's "soft" realtime and merely testing ensures this, is not the important part. The important part is that it should never miss a deadline.)

raverbashing 7y ago
I can understand it looks weird but it isn't. A faster processor has no more real time guarantees than a slower processor from the 80s Of course, the faster one can do more stuff in less time, but for flying an airplane (or going to the moon) the amount of computing power needed is much less than people imagine. The issue here is adding more computing into an aging platform. But there's nothing inherently wrong into using an older platform into the flight computer. Now I'm not sure if for certification purposes they would be allowed to replace it with modern hardware but just keeping the functionality the same, I believe the answer would be yes, that they are allowed (but they probably didn't want to rewrite the sw and recertify the hw)
- wiz21c 7y ago
  is it me or the certification looks at the hardware but not at the software ?
  - raverbashing 7y ago
    Certification mostly looks at the behaviour, how you get there is your IP for the most part For example, the regulator doesn't care (much) how you built your wing, but it does care that's able to withstand 150% of the maximum expected forces. You can have parts done by different manufacturers (but to the same spec) and this is sometimes done on purpose in redundancy settings so that unknown bugs in one model are less likely to show up in a different model.
- jacobush 7y ago
  Processing has very little to do with hitting realtime deadlines. Either you do or you don’t. In fact, sometimes faster CPUs are worse for realtime because their latency can be worse.

antihero 7y ago

> to avoid recertification they kept their old computer hardware from earlier 737 generations, This is unbelievably fucked

adrianN 7y ago
No, it's not. Certification is an extremely expensive process with dubious benefits for safety. Why would you change hardware that has worked fine if it can fulfill your requirements?
- vageli 7y ago
  > No, it's not. Certification is an extremely expensive process with dubious benefits for safety. Why would you change hardware that has worked fine if it can fulfill your requirements? Is it fair to say the hardware is fulfilling the requirements though?
- freehunter 7y ago
  Because it obviously did not work fine and does not fulfill the requirements. What seems to have dubious benefits for safety is lying to the regulators and shoehorning new processes into old technology. Because hundreds of people have died from that exact thing, just on this one airplane.
  - adrianN 7y ago
    The airplanes didn't crash because the computer was too slow. They crashed because safety critical data was read from a sensor without redundancies.
    - aurelwu 7y ago
      But now during simulations test pilots apparently found situations where the computer was too slow to handle their input in adequate time. So while the crash was not the caused by this problem, there seems to be a problem.
- 7y ago