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I'm confused as to what Boeing is changing then - your description of 'dual-dual' systems sounds like what is happening with the master/slave failover system al

by MFLoon 7y ago

I'm confused as to what Boeing is changing then - your description of 'dual-dual' systems sounds like what is happening with the master/slave failover system already in place. It sounds like what they're changing is to have the two systems cross-check each other in real time, rather than have the in-band delayed core be the sanity check for each system, which seems like a big difference because it means that there are now disagreement scenarios whereas an in-band sanity check always is just checking one system against one set of invariants and thus can't disagree with it's own observations. Or am I misunderstanding?

ethbro 7y ago
You're forgetting there's a third system: the pilot. If the majority of computer aids turn off, the plane doesn't simply drop out of the sky. It reverts back to a more complicated, but human-controllable, vehicle. From the article (and who knows how much Bloomberg understood) the active-active sounds more like recognizing, not recovering from, errors. Which isn't the worst idea. Pilots being, well, pilots.
- joe_the_user 7y ago
  I think the problem is that the 737 Max is the product of a long line of planes engineered to fly the original 737 but now flying very differently due to the massively increased engine size, which supposedly creates a much more unstable aircraft. So you're asking the pilot to, in the midst of some other failure, to start flying a weird plane they ever flown before. You could solve that problem by training all your pilots in this BUT this solution is very expensive, so expensive the airlines might just demand their money back instead. And that wouldn't be a solution for Boeing.
  - ethbro 7y ago
    All true. But from where we are today, that seems like a better solution from a safety perspective. And now, the FAA (or EASA) might just mandate that anyway. I wouldn't be surprised if CAAC refuses to ever recertify the 737 MAX, especially if a trade deal isn't struck.

by MFLoon 7y ago

ethbro 7y ago

You're forgetting there's a third system: the pilot. If the majority of computer aids turn off, the plane doesn't simply drop out of the sky. It reverts back to a more complicated, but human-controllable, vehicle. From the article (and who knows how much Bloomberg understood) the active-active sounds more like recognizing, not recovering from, errors. Which isn't the worst idea. Pilots being, well, pilots.

joe_the_user 7y ago
I think the problem is that the 737 Max is the product of a long line of planes engineered to fly the original 737 but now flying very differently due to the massively increased engine size, which supposedly creates a much more unstable aircraft. So you're asking the pilot to, in the midst of some other failure, to start flying a weird plane they ever flown before. You could solve that problem by training all your pilots in this BUT this solution is very expensive, so expensive the airlines might just demand their money back instead. And that wouldn't be a solution for Boeing.
- ethbro 7y ago
  All true. But from where we are today, that seems like a better solution from a safety perspective. And now, the FAA (or EASA) might just mandate that anyway. I wouldn't be surprised if CAAC refuses to ever recertify the 737 MAX, especially if a trade deal isn't struck.