Abstract: The effects of propeller rotation direction on pitching moment characteristics of aircraft are investigated through numerical simulations, aiming to discover a way to improve the longitudinal static stability of low Horizontal Tail Plane (HTP) turboprop aircraft. Based on the dynamic patched grid technique and unsteady Reynolds-averaged Navier-Stokes (URANS) equations, a T-tai twin-engine turboprop aircraft is computed first to validate the accuracy and reliability of the numerical method. Simulations are then conducted on three different low-HTP turboprop aircraft configurations respectively named co-rotating (CO), counter-rotating inboard-up (CNIU) and counter-rotating outboard-up (CNOU). The pitching moment characteristics and the flowfield details of each configuration are analyzed. Results indicate that the pitching moment curve slope of the conventional CO configuration is significantly lower than that of the unpowered configuration at low angles of attack due to the overall efficiency reduction of the HTP; The port HTP of the CO configuration almost loses its functionality at low angles of attack while the starboard HTP still maintains good efficiency; The large discrepancy in the efficiency between the port and starboard HTP of the CO configuration is mainly due to the difference in their local downwash gradients; Among the three configurations mentioned above, the CNOU configuration appears the worst in terms of pitching moment characteristics, while the CNIU configuration can maintain good pitching moment characteristics in the whole range of low and moderate angles of attack.

Key words: turboprop aircraft, low horizontal tail plane, propeller rotation direction, pithing moment characteristics, numerical simulation