I'm a bit out of my waters when it comes to aerospace, hopefully someone more familiar with the field can correct me if I'm wrong on any of these accounts. I kn

I'm a bit out of my waters when it comes to aerospace, hopefully someone more familiar with the field can correct me if I'm wrong on any of these accounts. I knew I should have given examples from the medical field, but the parent post mentioned airplanes and nuclear plants so... Airplanes that cannot be flown without computers definitely do exist. The F-117 is perhaps the most famous. Its shape makes it aerodynamically unstable on all three axes and it needs constant correction from the FBW system. Which has quadruple redundancy :). You can turn off the autopilot in these systems, obviously, so you get to say where it goes -- but without the FBW system to issue corrections, the plane crashes. As for Boeing (or Airbus, who have this ELAC thing)... the main thing to understand here is that there is not a computer. There are several computers, each of them covering a particular set of modules (e.g. ELAC controls the ailerons and elevator, SEC controls spoilers and elevator). There's a more in-depth overview here: https://aviation.stackexchange.com/questions/47711/what-are-the-main-components-of-the-airbus-fly-by-wire-system-is-ecam-related-t https://aviation.stackexchange.com/questions/47711/what-are-... . The autopilot is only one of them. The way they take over each other's functions is actually remarkably advanced, and leads to very interesting procedures for handling failures, see e.g. https://hursts.org.uk/airbus-nonnormal/html/ch05.html https://hursts.org.uk/airbus-nonnormal/html/ch05.html . Now, on some airplanes, some actuators can only be controlled through these computers. They get the commands from the pilot and they issue the right signals that control the actuators. There's no way to bypass them. You can turn off the autopilot and the plane goes where you want but the actuators that control the flight control surfaces are still acted upon by computers. I don't know if this is the case on Airbus specifically (like I said, I'm in a different field), but if it were, then simply turning those systems off in case of something unexpected is definitely not the right design solution.