The 180° spring return actuator 4thGeneration with 90° fail safety position is used for 0°-90°-180° operations where in case of air failure the actuator has to return to the 90° position. At both ends of the actuator a spring set is mounted and the compression on both sides of the springs is caused by the rotation from the 90° position. The fail-safe operation is achieved by the extension of the compressed springs that bring the actuator from 0° or 180° position to 90° position. The external travel stop is available as a standard in fully open position (180°) and in fully close position (0°), and it is easily and precisely adjustable of +/- 4° in both directions.