Conceptual Design Assessment of Advanced Hybrid Electric Turboprop Aircraft Configurations

This paper presents a conceptual design study of hybrid electric turboprop aircraft configurations for entry into service in the year 2035. A design mission of 800 nm and 70 passengers was the focus of the study. The hybrid electric architecture was used as an enabler for advanced configurations and improved propulsive efficiency. The main energy source for cruise flight is conventional fuel, batteries are used only to cover peak loads. A design process with four phases covering a wide design space was performed: 1) initial brainstorming phase (48 concepts identified), 2) qualitative down-selection based on expert judgment (reduction to 17 concepts), 3) initial quantitative analysis with simple spreadsheet methods (reduction to four concepts), and 4) evaluation of the four most promising concepts with classical conceptual design methods enhanced by more detailed disciplinary analysis when required. The most promising concept after all phases consisted of a parallel hybrid architecture with a high aspect ratio wing, electrically driven propellers at the wingtip and reduced vertical tailplane. A mission fuel reduction of 4% compared to an advanced EIS 2035 turboprop without hybrid electric propulsion was achieved with this concept. Other promising configurations included a tailless concept and a distributed propulsion configuration.