Abstract:
Wind tunnel tests and comprehensive rotorcraft analysis were carried out on a slowed main rotor full-wing lift and thrust-compounded helicopter with a trailing propeller to investigate the effects of rotor and wing configuration on performance, blade structural loads, and hub vibratory loads. Experiments were conducted at advance ratios up to 0.7, incorporating three full-wing configurations with symmetric and asymmetric incidence angles and three different rotor shaft tilt angles. Propulsive thrust was measured by a trailing pusher propeller with its own balance system. The wind tunnel test data was used to validate the University of Maryland Advanced Rotorcraft Code (UMARC). Results showed that the maximum lift-to-drag ratio is achieved using either of the symmetric or asymmetric full-wing lift-compound configurations with high lift offloading and aft shaft tilt. Both blade structural loads and hub vibratory loads are significantly reduced when rotor lift is offloaded to the wings. Lift compounding enables efficient high-speed flight, with a high lift-to-drag ratio of 7.5 maintained at an advance ratio of 0.7. Lift and thrust-compounded rotorcraft propulsive trim was achieved up to an advance ratio of 0.5, demonstrating that efficient high-speed flight, with peak lift-to-drag ratios exceeding 4.5, is enabled through lift offloading.