Aerodynamic and flight mechanics analysis of airbus helicopters' compound helicopter racer in hover under crosswind conditions

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Thiemeier, J.
Frey, F.
Keßler, M.
Krämer, E.
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In recent years, various helicopter manufacturers increasingly have been focusing on the development of new high-speed rotorcraft con1gurations, one of them being the compound helicopter RACER of Airbus Helicopters (AH). However, these new configurations encounter new aeromechanic challenges, in terms of aerodynamic interactions, flight mechanics stability, rotor dynamics or aeroacoustic noise emission, to name only a few. In the scope of this work, the behaviour of RACER in hover under the influence of crosswinds from eight different directions is investigated in order to support AH at the de-risking of RACER for this flight condition prior to first flight. Therefore, a multidisciplinary, high-fidelity tool chain for coupled and trimmed aerodynamic simulations of the complete rotorcraft is applied. The presentation of the results is organized in three parts. In the first part, the flight mechanic behaviour is analysed and successful de-risking of ground clearance is shown. The second part focuses on the performance of the main rotor, the lateral rotors and the tail surfaces under wind influence and shows that minimal power is required for headwind. In the last part, an analysis of the engines is performed, with a closer look at the inflow quality to the core engine and the convection of the hot exhaust gases.