Abstract: A platform leveling system for an aerial lift truck utilizes a master/slave combination of helical hydraulic rotary actuators to automatically level the work platform in response to movements of the boom. For a two-stage aerial lift comprised of a lower boom and an upper boom, a first rotary actuator is coupled to the base of the lower boom, a second rotary actuator is coupled to the elbow where the upper boom is hinged to the lower boom, and a third rotary actuator is coupled directly to the platform and upper boom. Movement of the lower boom relative to the base causes the first rotary actuator to displace a fixed amount of hydraulic fluid, and movement of the upper boom relative to the lower boom caused the second rotary actuator to disperse a fixed amount of hydraulic fluid.