Re: Self drive
Now, this is all beside the point as the actuation method has nothing to do with who/what is giving the control inputs. The vast majority of autopilot installations are on non-FBW aircraft and conversely, FBW does not require the presence of an autopilot. In fact, flights can be dispatched with an inoperative or unusable autopilot on every aircraft and company I know of.
However, if the autopilot does screw up, it is still my responsibility to maintain safe control of the aircraft.
With that said:
> If the on-board computer
What on Earth is the "on board computer"???
> simply dies, severing all fly by wire controls, the pilot is pretty much useless.
It is a certification requirement (FAR/EASA) that the aeroplane be controllable in the event of loss¹ of flight control signalling. Different solutions have been adopted, e.g., on Airbus (320 series at least) rudder and trim have mechanical linkages. The 787 has redundant hydraulic / electric linkages to the flight control surfaces. If things go wrong enough, the flight deck still have direct control of the stabiliser and a pair of spoilers.
> Its not like there are hydrolics [sic] from the pedals in a Dreamliner cockpit to the rudder or ailerons.
See above (and actually, the rudder on the B787 *is* hydraulically actuated, although there is no direct linkage to the pedals).
¹ As in complete loss. A simple degradation may not even ground the aircraft.