Abstract
This study examines key indicators and criteria for assessing the efficiency of hybrid turbo-electric propulsion system (HTEPS) configurations for passenger aircraft. A comprehensive review of scientific and technical literature was conducted to identify the most relevant efficiency metrics for HTEPS, with a focus on hybrid-electric propulsion and fuel cell integration. The Evektor EV-55 Outback light multipurpose aircraft, known for its short takeoff and landing capabilities, was selected as a reference model. The study highlights the advantages of all-electric propulsion for a nine-seater aircraft, discussing the impact of hybridization on fuel efficiency, performance, and cost-effectiveness. Two hybridization architectures—sequential and parallel—are evaluated, with the sequential architecture deemed more suitable for small aircraft due to its simplicity and feasibility. The findings confirm that utilizing an engine with lower rated power, in combination with a hybrid-electric system, is a more efficient and cost-effective approach compared to conventional higher-powered engines. The paper concludes with recommendations for optimizing HTEPS configurations and future research directions in hybrid-electric aviation.