Aerodynamic Analysis and Optimization of a Coaxial Helicopter Fuselage

The flight dynamics and flight envelope of coaxial ultralight helicopter CoAX 2D were investigated. For this purpose, series of flight tests was carried out. This paper presents the computation of the fuselage aerodynamics of the CoAX 2D with the DLR flow solver TAU. For cruise flight, fuselage polars with different angles of attack and yaw angles without rotor downwash were calculated. Furthermore, different airspeeds, climb and sink rates were simulated in combination with rotor downwash. To simulate the rotor downwash from the coaxial rotors, the Actuator Disc approach is used. The lift of the horizontal stabilizer is compared between flight test and simulations for validation purposes. The lift was determined in the flight test by deflection of the tail boom. Finally, concepts for the optimization of the fuselage were developed. The landing gear was selected as a possible optimization potential. The changes from an aerodynamic point of view related to the shape of the skid supports. The aerodynamics of the new landing gear were compared with the old configuration and a reduction of drag could be shown.