Experimental investigation of ACFs’ influence on rotor critical component loads based on an unmanned helicopter

Active rotors with actively controlled flaps (ACFs) are effective for helicopter vibration control, yet dynamic deflection of ACFs may impose adverse effects on rotor critical components. This study presents the experimental validation of the ACFs’ influence on rotor critical components loads through flight tests based on an unmanned helicopter. Whirl-tower tests were conducted to validate the deflection capability of the ACFs under rotor rotating speed, as well as the functionality of the deflection monitoring and data acquisition systems. Subsequent flight tests were performed on an unmanned helicopter to evaluate the effectiveness of ACFs in reducing fuselage vibration and to investigate their associated effects on critical component loads, including blade-root flapping bending and pitch-link loads, under various forward flight velocities. The test results demonstrate that ACF deflection significantly influences fuselage vibration, blade-root flapping bending, and pitch-link loads, with the effects intensifying as deflection angle increases. However, the influences on other harmonics of these loads remain limited. With the optimal control signals, the ACFs can successfully reduce fuselage vibration while alleviating loads on critical components. These findings confirm the feasibility of employing ACFs for both vibration reduction and load management for the flight test helicopter in this study.