SERVO-FLAP ROTOR POWER IMPROVEMENT THROUGH WIND TUNNEL TESTING

The K-MAX helicopter servo-flap rotor’s power improvement has been successfully improved as the result of a study conducted in the University of Hartford’s subsonic wind tunnel. Three types of test models were fabricated and tested. First, eight different servo-flap bracket shapes were tested with 3 air-speeds and 5 yaw angles to determine an optimum flap bracket shape. Second, a ½-scale model of the existing servo-flap assembly and individual components was designed, manufactured and wind tunnel tested. Two blade pitch angles and three servo-flap angles with a total of six combinations of angle of attacks were tested. Third, 2.5:1-scale models of existing and modified servo-flap brackets were tested at 7 different airspeeds. The power improvement of the servo-flap assembly was achieved by 8.2% for a five-degree and by 7.3% for a zero-degree angle of attack of the rotor blade. The methodology used to determine the overall in-plane force and power requirement of the servo-flap assembly and the individual components, along with the process of the aerodynamic drag minimization of the brackets, were also addressed.