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"If the software was changed to reconcile 2 sensors, it would then lead to a new "AOA Disagree" indicator which would raise doubts to the FAA that Boeing could

"If the software was changed to reconcile 2 sensors, it would then lead to a new "AOA Disagree" indicator which would raise doubts to the FAA that Boeing could just give pilots a simple iPad training orientation instead of expensive flight-sim training." I always liked this quote from the "Mythical Man-Month": “Never go to sea with two chronometers, take one or three”. https://blog.ipspace.net/2017/01/never-take-two-chronometers-to-sea.html https://blog.ipspace.net/2017/01/never-take-two-chronometers...

jasode 7y ago
>I always liked this quote from the "Mythical Man-Month": “Never go to sea with two chronometers, take one or three”. (I can't tell if you're making a side comment or specifically replying to the categorization of "software bug".) Yes, the 737 MAX only has 2 AOA sensors instead of 3 like Airbus A320. This is a physical design of sensors mounted on the airframe. But this aerospace engineering design detail seems outside the scope of assigning blame to software programmers writing code. (There isn't a software coding methodology that makes a 3rd AOA sensor appear.)
- Kurtz79 7y ago
  It was mostly a side comment, but it seemed appropriate in this context. For such an important system, I would think that a single instance would be too little (single point of failure: even in less mission critical system it wouldn't be allowed), while using two you would not be able to resolve a reading conflict between them (which is the point of the quote), so three is probably a reasonable number. Even if applied to design and not to software programming, the concept is still sound. The point was what the quote meant, not its source.
  - weaksauce 7y ago
    Using two would have been strictly better a design than just one. Obviously three is better but two disagreeing and shutting down mcas would be much, much preferable than relying on one to the grave.
    - vkou 7y ago
      Preferable to the passengers, but not to Boeing, because that little warning light would warrant retraining and re-certification of pilots. It's why they didn't do it.

jasode 7y ago

>I always liked this quote from the "Mythical Man-Month": “Never go to sea with two chronometers, take one or three”. (I can't tell if you're making a side comment or specifically replying to the categorization of "software bug".) Yes, the 737 MAX only has 2 AOA sensors instead of 3 like Airbus A320. This is a physical design of sensors mounted on the airframe. But this aerospace engineering design detail seems outside the scope of assigning blame to software programmers writing code. (There isn't a software coding methodology that makes a 3rd AOA sensor appear.)

Kurtz79 7y ago
It was mostly a side comment, but it seemed appropriate in this context. For such an important system, I would think that a single instance would be too little (single point of failure: even in less mission critical system it wouldn't be allowed), while using two you would not be able to resolve a reading conflict between them (which is the point of the quote), so three is probably a reasonable number. Even if applied to design and not to software programming, the concept is still sound. The point was what the quote meant, not its source.
- weaksauce 7y ago
  Using two would have been strictly better a design than just one. Obviously three is better but two disagreeing and shutting down mcas would be much, much preferable than relying on one to the grave.
  - vkou 7y ago
    Preferable to the passengers, but not to Boeing, because that little warning light would warrant retraining and re-certification of pilots. It's why they didn't do it.