Architectural Trade-offs for a Hybrid-Electric Regional Aircraft

Abstract

Research entities and the aviation industry are collaborating to reduce the greenhouse gas emissions of the global aircraft fleet. To move away from fossil fuels as energy carrier while reducing the aircrafts primary energy demand are the ideal but challenging means to achieve this target. The research activities within the German government funded project TELEM have shown on a conceptual level that both measures could be realized for regional aircraft with an optimized hybrid-electric propulsion (HEP) ar- chitecture. Short, but very frequently flown distances of 200 nm and more could be served fully electri- cally by advanced propeller-driven aircraft with an assumed entry-into-service (EIS) in 2035. This paper gives an overview of integration concepts pursued in the project and reflects on various design aspects of a plug-in hybrid-electric aircraft, featuring a fully electric flight capability and a kerosene-fueled tur- boshaft range-extender. The aircrafts HEP architecture is optimized with regard to the number of pro- pellers, as well as range extenders and their integration concept as to yield the best efficiency and to enable commonality with smaller aircraft leading to potential cost reductions among aircraft classes. Furthermore, a thermal management system, which is essential for the hybrid-electric propulsion archi- tecture and its requirements are discussed and a favorable option selected. The final configuration fea- tures ten propellers and one range extender. The results also confirmed the exceptional efficiency of a plug-in HEP architecture for regional aircraft, showing a 34.6 % reduction in fleet energy and 64.4 % reduction in fuel consumption compared to a conventional turboprop architecture with an EIS in 2035.