Aero-Propulsive and Aero-Structural Design Integration of Turboprop Aircraft with Electric Wingtip-Mounted Propellers

The current focus in the aviation industry for more sustainable designs, could mean the revive of propeller propulsion, due to their relative high propulsion efficiency compared to jets. In addition, wingtip-mounted propellers installed in tractor configuration can be used as tip-vortex attenuating devices, reducing the wing induced drag. So far, studies on wingtip-mounted propellers mainly concentrated on the aerodynamic interaction effects, disregarding the integration with the airframe and wing-structural mass. This paper presents a method to integrate into an aircraft sizing process the aerodynamic, aero-propulsive, and aero-structural effects of tip-mounted propellers, in the context of a typical turboprop featuring hybrid-electric propulsion. Subsequently, a number of case studies are performed to investigate the sensitivity to modifications of the propulsion system on wing and aircraft level. Results show that the performance benefit gained by the application of a wingtip-mounted propeller is easily overruled by the weight penalty that it introduces, an almost linear relationship between shaft power ratio and MTOM was observed. For variations of propeller diameter, it is seen possible to attain equal performance in terms of energy efficiency with a mass penalty. For phi=0.1, the reference performance is obtained for a tip-mounted propeller occupied span fraction of 0.175 with an increase in MTOM of 2.8%. For phi=0.2, this is obtained at a larger tip-mounted propeller (occupied span fraction = 0.275) and an increase in MTOM of 5% compared to the reference design.