Aeromechanics Investigation of a Dual-Wing Lift Compounded Slowed Mach Scale Rotor

An aeromechanics analysis of a Mach-scaled rotor with lift compounding was conducted to understand the impact of various wing configurations on performance and loads. An assessment of the single retreating side wing and dual wing configurations was conducted for advance ratios up to µ = 0.7, two wing incidence angles (4° and 8°), and three rotor shaft angles (-4°, 0°, and 4°). Aircraft performance, control angles, blade structural loads, hub vibratory loads, and aerodynamic interactions between the rotor and wing were evaluated using the University of Maryland Advanced Rotorcraft Code (UMARC). Additionally, UMARC coupled rotor-wing analysis was validated with wind tunnel data of a lift and thrust compounded rotor. The study shows that the single wing configuration is beneficial for peak vehicle performance (L/D), though the dual wing configuration minimizes blade loads. The single wing configuration observed a 7% greater wing L/D than the dual wing configuration for the same 8° wing incidence angle at µ = 0.5 and α_s = 0^◦, however, the dual wing configuration yielded a 20% lower steady flap bending moment. The study showed that the wing wake has a negative effect on the rotor performance especially at rearward rotor shaft angles; this is overcome with the efficiency gains from lift offset present in a single wing configuration but absent in the dual wing configuration. Hence, the single wing configuration attains the highest performance while the dual wing configuration minimizes structural loads. A lift compounded rotor is limited at high advance ratios since it is almost entirely offloaded, resulting in increased total lift to drag ratio at the cost of large blade structural loads.