The Challenges for the Integration of the Drive Shaft in the RACER's Wing Configuration

The RACER is a high speed rotorcraft which is currently under development at Airbus Helicopters as part of the European research program CleanSky2. Eye-catching feature of the RACER is its joined wing configuration with an integrated super-critical drive shaft in the upper wing in order to provide power to the lateral rotors located at the wing tips. This wing configuration is the best compromise between different requirements which are partly opposing. As there is no previous experience with such a wing configuration, this paper describes the difficulties, challenges, requirements and limits for integrating the super-critical drive shaft in it. Special attention is given to the structure-mechanical concept and its consequences for the drive shaft's behavior and movement inside the thin wing profile. The paper focuses on identifying and showing the main drivers for sizing, with all individual contributors leading to the final structure-mechanical concept of this unique wing configuration for a vertical take-off and landing vehicle. On top, the integration of the wings including drive shaft, the interaction with the fuselage and other secondary aspects of the wing functions and needs are treated.