Application of the modified blade element method for propeller blade design on high-speed helicopter X3

The X3 helicopter is the experimental demonstrator of the H3 compound helicopter concept (High speed Hybrid Helicopter) developed by Airbus Helicopter and intended to operate at cruise speeds of about 113 m/s (220 kt). It is equipped with short fixed wings and two side-mounted propellers. Usually, fixed-wing propellers are sized to optimize the power consumption in cruise flight. In the case of a compound helicopter, some other flight cases such as hover and descent in autorotation also have to be considered. The geometrical criteria to satisfy all flight regimes may be contradicting what implies a compromise and a new approach to the propeller design. This paper presents the different steps of X3 propellers design from novelty theoretical Blade Element Method studies confirmed by CFD, experimental and flight tests.