This study focuses on the aerodynamic characteristics of a high speed compound helicopter with a maximum cruise speed of 500km/h which JAXA is proposing for the use of EMS (Emergency Medical Service). The aerodynamic properties of the airframe are evaluated by the wind tunnel testing with various configurations carried out in JAXA 2 m × 2 m Low-Speed Wind Tunnel. In order to realize this high speed flight condition, the essential requirement is to achieve a very low drag/aerodynamic interference airframe. The test results show 15% lower than the target airframe drag by adopting the hub fairing and 12% improvement of lift/drag ratio by differential deployment of the flap equipped on the wing combining the synergistic effect with the lift offset generated by the main rotor.
