Impact of Engine Failure Constraints on the Initial Sizing of Hybrid-Electric GA Aircraft

Abstract

Potential advantages of hybrid-electric aircraft are fuel savings, lower emissions, and reduced noise. Since these aircraft generally apply multiple power sources, they can also be designed to sustain flight if certain parts of the propulsion system fail. Thus, an increase in flight safety can be another benefit of hybrid-electric propulsion concepts. In this paper, the influence of safety constraints on the initial sizing for a hybrid electric 4-seat general aviation aircraft will be analyzed. For this purpose, a simplified optimization method is applied to perform the initial sizing under consideration of One Engine Inoperative (OEI) constraints. The OEI constraints significantly reduce the available design space. If a hybrid-electric aircraft must be able to fly a single traffic pattern on one engine or motor, the mass increase can be less than 10% of MTOM. If a 100 km diversion is considered, the mass increase can be up to 50% of MTOM, depending on battery technology.