Abstract: A fail-safe hydraulic actuator that uses one or more constant force retraction springs to provide fail-safe retraction of the piston and piston rod in the event of loss of hydraulic pressure. The constant force retraction spring(s) can be packaged in a small volume thus decreasing the overall length of the actuator. This allows the actuator to be utilized in areas where length is a concern. The constant force retraction spring(s) are part of constant force retraction spring mechanism(s) that can be mounted within a hydraulic fluid cavity of the fail-safe hydraulic actuator to protect the constant force retraction spring mechanism(s) from the environment surrounding the actuator. A sensor that detects the linear position of the piston within the piston chamber may also be provided.