[aperrien]

Large planes are all fly by wire. In a commercial airplane, you're talking about moving maybe a quarter-ton of metal for the rudder alone, and against high wind speeds. There is no way to move those without powerful servo motors.

[therein]

They use hydraulics, not necessarily fly-by-wire and servos. But when they lose the engines, then they lose hydraulic pressure.

[cmurf]

There's APU and/or RAT to fallback on in case of the rare dual engine failure.

[labcomputer]

I guess they are if you mean fly-by-piano-wire!

The (as of a this year) second-most popular airliner, the Boeing 737, has fully mechanical controls for the ailerons and elevator (with hydraulic boosting). Elevator trim is also mechanical.

The pilot needs to be built like a gorilla to fly it, but primary flight controls continue work, even with a total failure of all electrical and hydraulic systems.