A locking mechanism for locking an actuator piston within an actuator cylinder housing is disclosed. The locking mechanism comprises a locking pin that is moveable between extended and retracted positions. The locking pin can be moved using a controller, such as a hydraulic controller, for example. In the extended position the locking pin engages the actuator piston thereby locking the actuator piston in a specific position. The locking mechanism includes a mechanical bias (such as a spring or other mechanical system) that biases the locking pin towards an extended position to lock the actuator piston when counter-pressure on the locking pin is lower than the pressure provided by the mechanical bias. The locking pin can be hydraulically operated so that hydraulic pressure that forces the actuator piston to retract also exerts force on the locking pin to move it from a locked position to an unlocked position.