Distributed Hybrid-Electric Propulsion Benefits for Span-Limited Aircraft

The impact of the ICAO code C gate span limit is assessed on the sizing of a serial Hybrid Electric Aircraft (HEA) of increasing Degree of Hybridization (DoH). For a set of Top Level Aircraft Requirements (TLARs) similar to the ATR-42, it is shown that the increase in MTOM due to the presence of the battery is such that only a maximum DoH under 30% can be achieved before the wing span of the serial HEA reaches the 36 meters gate size. The same aircraft is fitted with Leading Edge Distributed Propulsion (LEDP) to increase the wing loading and relieve the span constraint, though this introduces limitations regarding the available wing volume. It is shown that a combination of high wing loading and of low volumetric energy density for batteries compared to jet fuel can lead to the available wing volume being too small for the required volume of the energy carriers. Finally a value in wing loading is found which simultaneously meets the span and wing-volume constraints. The higher DoH enabled by LEDP leads results in a 33% reduction in fuel burn compared to the fuel-based reference aircraft, while the overall energy consumption is increased by 6%.