Analysis and Testing of Mach-Scaled Rotor with Trailing-Edge Flaps

Ongoing research is presented directed toward the development of a Mach-scaled rotor model with piezoelectric bender-actuated trailing-edge flaps for individual blade control of helicopter vibration. First, an analytical model is developed for the coupled actuator-flap-rotor dynamic response in hover. Then, the analysis is validated by using test data obtained by hover testing a 6-ft (1,82-m)-diam, Froude-scaled rotor with piezo-bender-actuated trailing-edge flaps. The analytic model shows good correlation with experimental flap deflections and oscillatory hub loads. For the Froude-scaled model flap deflections of ±4 to ±8 deg, for 1 to 5 /rev flap excitation, were achieved at 900 rpm. This flap activation resulted in a 10% variation in the steady rotor thrust level at 6 deg collective. Next, two Mach-scaled rotor blades with piezo-bender actuation were designed and fabricated. The rotor was tested in the vacuum chamber, and flap deflections of ±8 deg were achieved in vacuum at the Mach-scaled operating speed of 2000 rpm. The analysis predicts that in hover flap deflections of ±5 deg can be achieved at 2000 rpm. Future work will involve hover tests followed by forward flight tests in the wind tunnel to confirm these predictions and demonstrate concept feasibility.