Gents,
Extract from A320 AMM for your perusal.
Ailerons
Each aileron can be powered by two servocontrols signalled by two Elevator and Aileron Computers (ELAC) and supplied from different hydraulic systems
In the event of a failure, the ailerons become automatically controlled by the ELAC 2 (roll) and the associated servocontrols switched to the active mode, the others being now damped. If a multiple failure condition causes the loss of the control of the two servocontrols of an aileron, the servocontrols automatically switch to the damping mode. This operating mode is also automatically engaged in the event of loss of pressure.
Rudder
One servoactuator is normally operating, the other being by-passed. A spring rod is provided to center the actuators when both of them are depressurized.
Elevators
In the event of the loss of control of the two servocontrols of the elevator, the servocontrols are automatically switched to a centering mode and hold the surface in the neutral position (Electrical control loss). In the event of the loss of the two hydraulic systems supplying the servocontrols of one elevator, the damping mode becomes automatically engaged.
Spoilers
In the event of an electrical failure, the associated surface is hydraulically held down. In the event of a hydraulic failure, the servocontrol is hydraulically locked in one direction to prevent the surface from raising. In both cases the control of the symmetrical surface is automatically inhibited.