Design of the next generation of transport aircraft includes a combination of novel technologies with novel aircraft configurations. However, when to apply which technology and to what category of aircraft is not well understood. The aim is to identify opportunities and limitations of scaling of main technology applications, i.e. “switching points” across different classes of vehicles. These different fixed wing vehicle classes of aircraft are: 1) general aviation, 2) commuter aircraft, 3) regional aircraft, 4) short-medium range aircraft and 5) large passenger aircraft. The switch-over points between different technologies and system architectures are not yet well known and may also depend on aspects such as certification, operating environment or speed.
The identification of such a landscape of opportunities and limitations of key technology applications should benefit the development of (more) sustainable and environmentally friendly aircraft, to reduce the climate impact of aviation in the future and sustain general travel needs and desires with cleaner means of transportation. Such a landscape may steer future research efforts in the most relevant directions in order to mature technologies and their applications. With all partners being educational institutes, CHYLA’s developments and research directly contribute to the education of new generations of aerospace engineers.
A notional landscape of the application areas across the different vehicle classes is presented in the attached image. This image also summarizes the key results for the project.
Overall it may be concluded that:
1) For general aviation, up to ~600kg payload can be transported fully electrically over ranges up to 400km, beyond this up to 600km a serial hybrid electric powertrain is beneficial with respect to conventional kerosene.
2) For commuter aircraft, with 19 passengers, a serial hybrid electric powertrain is limited to 180km range when it has to remain within CS23 weight limit, or 10 passengers at ~300km. Beyond this range, CS25 regulations are applicable.
3) For regional propeller aircraft a clear trend emerges with between 10 and maximum 20% supplied battery power (to remain within 36m span limit): serial hybrid electric is outperformed by parallel boosted turboprop, which are both outperformed by the most complex hybrid electric powertrain. However, during off-design operation this may be different. Off-design operation is particularly interesting because fuel savings with respect kerosene aircraft (up to 50% fuel savings depending on the particular design for 70 passengers transported over 500km).
4) For larger jet airliners, liquid hydrogen combustion is the only potentially feasible solution though it comes at the cost of more weight and longer fuselage. The latter may be challenging in terms of airport limits and may require a double deck design.
5) High-power charging facilities: >400kW are required; Charging time is seen to have a relatively large impact on fleet electrification
