In the present study, numerical simulations of a high-speed compound unmanned rotorcraft were carried out by employing an unstructured Reynolds-Averaged Navier-Stokes solver. For the simulations, a conceptually designed rotorcraft was used which includes two propellers, a fuselage with main and tail wings and a co-axial rotor. Aerodynamic characteristics of the propulsion components were studied by comparing aerodynamic coefficients with the following modes: hovering, transitional low-speed, high-speed, and maximum flight speed conditions. Furthermore, the effects of the fluid dynamic interactions between the co-axial rotor, propellers, and wings were investigated. Lastly, the impact of ground on the aerodynamic performance on the rotorcraft was studied.