The advantages of fly-by-wire are too good to pass up, so that leaves the question of how to design an FBW system.
A high school teacher of mine in the 1970s predicted an accident like AF447. He framed it this way: the 'American' approach is to implement FBW to always do what the pilot inputs indicate, whereas the 'French' approach is to do the right thing, and override the pilot if the FBW 'knows' better. That's an interesting cultural cultural consistency as well!
So, the 'American' approach is better if the sensors are not working as expected, and it makes the software simpler. The 'French' approach is better if the pilot is wrong, but both the sensors and the software must be working perfectly. Everyone makes mistakes, and all software has bugs. What to do?
(In reality, some 'judgement' is needed by the software, even in the American approach.)
EDIT: That said, some of the design choices in the Airbus FBW are baffling, such as making the control input the average of two different inputs. I like to think AF447 is less likely to have happened in a Boeing ship, although the ulitimate cause of the crash was a pilot making what amounts to a beginner mistake.
None of this is relevant to the actual issue raised by the GP: the yokes of the pilot and co-pilot are not mechanically linked. They can be mechanically linked even with a FBW system. And personally, as someone with a bit of flying experience myself, I can't comprehend why you'd want them to not be mechanically linked. The opportunity for confusion with conflicting inputs is too damn high.
Mechanically linking is heavier than fbw/electrical/fiber optic linking, and what's the point if there's no mechanical linkage to the control surfaces?
With the fbw system, the software makes the choice on how to interpret the control movement, use one or both? If one, which one?
EDIT: Maybe you mean that a mechanical linkage would provide a feedback mechanism, so that one pilot would know if the other pilot was attempting an input? I don't know if there's force feedback on Airbus flight controls.
> what's the point if there's no mechanical linkage to the control surfaces?
In this case, the pilot would have realized the junior copilot was issuing control inputs and (likely) prevented a plane from crashing, saving the lives of all aboard.
Seems like a pretty decent point to me.
> EDIT: Maybe you mean that a mechanical linkage would provide a feedback mechanism, so that one pilot would know if the other pilot was attempting an input? I don't know if there's force feedback on Airbus flight controls.
Yes, that's what I meant. And no, there isn't. At least, not one that would indicate conflicting inputs from the other pilot.
> although the ulitimate cause of the crash was a pilot making what amounts to a beginner mistake.
But it was only one of the pilots, the right-side pilot, who continued to hold the stick back and and retained command. The left-side pilot didn't realize that was occurring until it was too late.
A high school teacher of mine in the 1970s predicted an accident like AF447. He framed it this way: the 'American' approach is to implement FBW to always do what the pilot inputs indicate, whereas the 'French' approach is to do the right thing, and override the pilot if the FBW 'knows' better. That's an interesting cultural cultural consistency as well!
So, the 'American' approach is better if the sensors are not working as expected, and it makes the software simpler. The 'French' approach is better if the pilot is wrong, but both the sensors and the software must be working perfectly. Everyone makes mistakes, and all software has bugs. What to do?
(In reality, some 'judgement' is needed by the software, even in the American approach.)
EDIT: That said, some of the design choices in the Airbus FBW are baffling, such as making the control input the average of two different inputs. I like to think AF447 is less likely to have happened in a Boeing ship, although the ulitimate cause of the crash was a pilot making what amounts to a beginner mistake.
Don't miss William Langewiesche's article!
https://www.vanityfair.com/news/business/2014/10/air-france-...