4 ms·

The takeaway I'm getting form all of this is that the system functionality is fine, but the operation is too obscure. There should be a design intention to com

The takeaway I'm getting form all of this is that the system functionality is fine, but the operation is too obscure. There should be a design intention to communicate information to the pilot as clearly as possible, for automatic systems or otherwise. Relying on training alone for pilots to interpret this failure hasn't worked. It's too much of a blackbox if pilots can't quickly learn how the system is operating, e.g. how it operates when autopilot is on or off.

thatswrong0 8y ago
And they should have the MCAS rely on two AoA sensors and deactivate when there’s disagreement or perhaps ring a warning. IIRC Southwest Max’s have something like that, but it’s not a factory default (which is astonishing to me)
- outworlder 8y ago
  Southwest only has the 'AoA disagree' indicator, for pilot awareness. But it doesn't change the operation of MCAS itself.
- CydeWeys 8y ago
  It needs 3 sensors. If there's 2 sensors when you detect disagreement you can't safely do anything, even if it is warranted (e.g. if the AoA data showing 'good' is what's faulty). With 3 sensors you can discard just one bad sensor and continue flying safely, and then repair the broken sensor after the flight. Note that modern aircraft have 3 pitot tubes for precisely this reason. If AoA sensors are going to be so important too, then there also need to be 3 of them.
  - thatswrong0 8y ago
    Oh yeah totally agreed, I was just thinking that the 737 MAXs currently only have 2 installed so that’s what they could work with without an even greater retrofit.
    - CydeWeys 8y ago
      Well they're already not flying, likely won't be for many months, and the vast majority of 737 MAXes aren't built yet. Adding another sensor definitely seems like it might be in the cards, if it would help to resolve this issue.
linuxftw 8y ago
> The takeaway I'm getting form all of this is that the system functionality is fine, but the operation is too obscure. Doesn't sound like it's fine to me. In the case of the Lion Air crash, the AoA sensors were JUST REPLACED due to previous flight problems. Sounds to me like the system is fundamentally broken in some way.

thatswrong0 8y ago

And they should have the MCAS rely on two AoA sensors and deactivate when there’s disagreement or perhaps ring a warning. IIRC Southwest Max’s have something like that, but it’s not a factory default (which is astonishing to me)

outworlder 8y ago
Southwest only has the 'AoA disagree' indicator, for pilot awareness. But it doesn't change the operation of MCAS itself.
CydeWeys 8y ago
It needs 3 sensors. If there's 2 sensors when you detect disagreement you can't safely do anything, even if it is warranted (e.g. if the AoA data showing 'good' is what's faulty). With 3 sensors you can discard just one bad sensor and continue flying safely, and then repair the broken sensor after the flight. Note that modern aircraft have 3 pitot tubes for precisely this reason. If AoA sensors are going to be so important too, then there also need to be 3 of them.
- thatswrong0 8y ago
  Oh yeah totally agreed, I was just thinking that the 737 MAXs currently only have 2 installed so that’s what they could work with without an even greater retrofit.
  - CydeWeys 8y ago
    Well they're already not flying, likely won't be for many months, and the vast majority of 737 MAXes aren't built yet. Adding another sensor definitely seems like it might be in the cards, if it would help to resolve this issue.

linuxftw 8y ago

> The takeaway I'm getting form all of this is that the system functionality is fine, but the operation is too obscure. Doesn't sound like it's fine to me. In the case of the Lion Air crash, the AoA sensors were JUST REPLACED due to previous flight problems. Sounds to me like the system is fundamentally broken in some way.