3 ms·

> Airbus has 3 flight computers (1 PRIM and two SECs) for fly by wire - they run same software with voting deciding outcomes of commands that comes from the pi

by tivert 3y ago

> Airbus has 3 flight computers (1 PRIM and two SECs) for fly by wire - they run same software with voting deciding outcomes of commands that comes from the pilot to the flight surfaces. So a software bug could doom the plane? IIRC, some other flight-control voting system have 3 computers, but one runs software developed independently from the others.

Gare 3y ago
Boeing 787 is also fly-by-wire. Yes, software is life-critical. Therefore it is developed to a very high standard. Ada is often used.
- 7thaccount 3y ago
  I heard the military relaxed restrictions that required Ada. So the F-22 Raptor was mostly Ada, but the newer JSF is mostly C++. No idea if true, but that is what I remember.
  - tivert 3y ago
    > I heard the military relaxed restrictions that required Ada. So the F-22 Raptor was mostly Ada, but the newer JSF is mostly C++. No idea if true, but that is what I remember. I think that's correct. IIRC, the JSF C++ coding standard document is floating around.
    - chasil 3y ago
      I would certainly hope that it's the MISRA variant. https://en.wikipedia.org/wiki/MISRA_C https://en.wikipedia.org/wiki/MISRA_C
      - tivert 3y ago
        > I would certainly hope that it's the MISRA variant. I think this is it: https://www.stroustrup.com/JSF-AV-rules.pdf https://www.stroustrup.com/JSF-AV-rules.pdf, and it appears you're right: > The MISRA Guidelines were written specifically for use in systems that contain a safety aspect to them. The guidelines address potentially unsafe C language features, and provide programming rules to avoid those pitfalls. The Vehicle Systems Safety Critical Coding Standards for C, which are based on the MISRA C subset, provide a more comprehensive set of language restrictions that are applied uniformly across Vehicle Systems safety critical applications. The AV Coding Standards build on the relevant portions of the previous two documents with an additional set of rules specific to the appropriate use C++ language features (e.g. inheritance, templates, namespaces, etc.) in safety-critical environments.

by tivert 3y ago

Gare 3y ago

Boeing 787 is also fly-by-wire. Yes, software is life-critical. Therefore it is developed to a very high standard. Ada is often used.

7thaccount 3y ago
I heard the military relaxed restrictions that required Ada. So the F-22 Raptor was mostly Ada, but the newer JSF is mostly C++. No idea if true, but that is what I remember.
- tivert 3y ago
  > I heard the military relaxed restrictions that required Ada. So the F-22 Raptor was mostly Ada, but the newer JSF is mostly C++. No idea if true, but that is what I remember. I think that's correct. IIRC, the JSF C++ coding standard document is floating around.
  - chasil 3y ago
    I would certainly hope that it's the MISRA variant. https://en.wikipedia.org/wiki/MISRA_C https://en.wikipedia.org/wiki/MISRA_C
    - tivert 3y ago
      > I would certainly hope that it's the MISRA variant. I think this is it: https://www.stroustrup.com/JSF-AV-rules.pdf https://www.stroustrup.com/JSF-AV-rules.pdf, and it appears you're right: > The MISRA Guidelines were written specifically for use in systems that contain a safety aspect to them. The guidelines address potentially unsafe C language features, and provide programming rules to avoid those pitfalls. The Vehicle Systems Safety Critical Coding Standards for C, which are based on the MISRA C subset, provide a more comprehensive set of language restrictions that are applied uniformly across Vehicle Systems safety critical applications. The AV Coding Standards build on the relevant portions of the previous two documents with an additional set of rules specific to the appropriate use C++ language features (e.g. inheritance, templates, namespaces, etc.) in safety-critical environments.