The present study deals with optimizing the mission performance of hybrid-electric aircraft propulsion. This relates to single-mission analysis, safety-driven power redundancy considerations and fleet-wise assessment. The first part pertains to the optimization of performance for hybrid-electric propulsion at system level. An in-house computational tool is developed. It employs a genetic algorithm to optimize the power management strategy, evaluating the flight energy consumption. The operation of a 19-seater commuter aircraft is investigated. The concepts of Boundary Layer Ingestion and Distributed Propulsion display the potential to boost electrified propulsion, with series-hybrid and series-parallel configurations displaying up to 30% reduction in fuel and 20% reduction in energy consumption. Optimized flight profiles combined yield an additional 12% average energy consumption benefit for short, medium and long regional missions. The one-engine-inoperative oversizing consideration is expanded for aircraft propulsion systems with multiple energy sources and thrust-generating media. It is found that increasing oversizing rate close to the ideal leads to lower optimum energy consumption and increases redundancy. However, payload capacity penalties are required, up to 4 passengers. Heavier variants without penalties are up to 4% more efficient in terms of energy-per-weight in their carrying capacity against counterparts of the same oversize rate with reduced payload capacity. The proposed method highlights tradeoffs needed between redundancy and performance in sizing novel systems. The effectiveness of hybrid electric aircraft is also evaluated as part of a fleet. A Markov Chain-based Digital-Twin-like framework is developed to create a data-driven flight schedule. Test cases for Greece and Sweden are evaluated. In analyzing charging strategies, a 114-minute charge fully replenishes battery energy, but hinders the fleet flying capacity by 36%, offering only 8% energy benefit compared to a 40-minute turnaround. It is also found that increasing charger power raises available battery energy and enables up to a 16% efficiency improvement, but installation costs scale significantly. Specifically, 1500 kW chargers require three times higher dollars-per-kWh of added battery energy than 750 kW chargers, while delivering only a 6% additional efficiency gain. In evaluating the supporting infrastructure, findings suggest small remote Greek islands not connected to the mainland power-grid would require up to 30% additional peak power when serving hybrid-electric aircraft in a point-to-point approach. In a sensitivity study, decreasing the number of airports acting as charging hubs does not significantly affect the number of chargers per charging airport. This reduces the total amount of chargers across Greece by 66% when utilizing only the top 10% largest airports as charging hubs, compared to having chargers at all airports. The opposite is considered when placing chargers to all airports but the two largest in Sweden. Results showcase that a balance between hub-and-spoke and point-to-point travel can add around 25% in available electric energy per flight, while reducing the number of chargers by 14%, alleviating congested airports. Furthermore, removable batteries are considered for on-ground charging. It is found that, for a 30-aircraft fleet, having one additional battery per airport decreases the battery cost by 41% in a 15-year timeframe compared to on-board charging.
Κωνσταντίνος Ι. Παπαδόπουλος (2026) studied this question.