Performance Comparison of Conventional, Hybrid-Electric, and All-Electric Powertrains for Small Aircraft

This study analyzes the performance in terms of block fuel and block energy consumption of small aircraft with serial-hybrid, parallel-hybrid and pure battery-electric powertrains. After deriving design specifications and top-level aircraft requirements from a Cessna 182T Skylane, a conventional reference aircraft is designed first by using the Institute of Aerospace Systems' (ILR) aircraft design and evaluation software MICADO. Afterwards, aircraft with (partially) electric powertrains are designed towards the same specifications and top-level aircraft requirements and subsequently compared against the performance of the conventional reference aircraft. Comparison is done for both design and off-design conditions, the latter being characterized by variations of trip distance and payload. The impact of the degrees of energy- and power hybridization as well as the level of battery specific energy (200 - 400 Wh/kg at pack level) is analyzed. Results indicate that serial-hybrid aircraft configurations allow fuel savings only on missions significantly shorter than the design mission and with future battery specific energy of 400 Wh/kg. In contrast, if degree of power hybridization and the level of battery specific energy are correctly matched to each other, the parallel-hybrid configuration enables small fuel savings on all mission ranges. Within the considered range of battery specific energy, it is not possible to design an all-electric aircraft with mission ranges comparable to conventional configurations.