Stability and control augmentation system actuator

A stability and control augmentation system actuator operable for actuating a flight control surface of an aircraft, wherein the stability and control augmentation system actuator comprises:

• an actuator housing comprising a first aperture, a second aperture and a hydraulic chamber between the first aperture and the second aperture;
• a piston comprising a first end portion extending through the first aperture, an intermediate portion in the hydraulic chamber and a second end portion extending through the second aperture, wherein the piston is arranged for linear motion with respect to the actuator housing;
• a first fluid inlet in fluid communication with a first region of the hydraulic chamber proximal to the first aperture;
• a second fluid inlet in fluid communication with a second region of the hydraulic chamber proximal to the second aperture;
• wherein the first end portion is arranged to slide through the first aperture without a seal between the first end portion and the first aperture;
• wherein the second end portion is arranged to slide through the second aperture without a seal between the second end portion and the second aperture;
• and
• wherein the intermediate portion is arranged to slide in the hydraulic chamber without a seal between the intermediate portion and the hydraulic chamber;
• and
• bellows surrounding the second end of the piston and arranged to bias the piston, wherein the bellows are sealed against the actuator housing to seal the second aperture;
• the system further comprising:
• a first return line in fluid communication with the first region;
• and
• a second return line, wherein the second return line is in fluid communication with an inside of the bellows and the first and second return lines are connected together.