To reduce the climate impact of aviation, researchers are studying the replacement of fossil kerosene with liquid hydrogen and/or drop-in sustainable aviation fuel (SAF). These fuels can bring significant reductions in CO2 emissions and can offer savings in terms of non-CO2 climate effects. In addition, tube-and-wing aircraft can be optimized to decrease the global-warming impact by using a climate metric as a design objective rather than the operating costs. Previous research has shown that airplanes designed for minimal climate impact have a reduced cruise speed and fly at a lower altitude. This paper suggests a multidisciplinary, multi-level approach the evaluate the consequences of such design and fuels choices at the network level. Following the aircraft design step, a dynamic programming routine allocates the fleet and schedules the flights to maximize the network profit. We consider a hub-and-spoke network operating from Atlanta, with demand for domestic and international destinations. Compared to the reference cost-optimal kerosene fleet, a fleet consisting of climate-optimized kerosene aircraft can reduce the climate impact by 61% at a loss in network profit of approximately 21%. This design choice requires allocating an additional five aircraft. A fleet operating climate-optimal, hydrogen aircraft minimizes the climate impact. However, the high operating cost of long-range, hydrogen aircraft lowers the achievable profit. Aircraft powered by drop-in SAF provides Pareto-optimal solutions. These insights can be used to make decisions about the allocation of future aviation fuels in a network and the payload-range requirements of future aircraft.@en

The objective of the EU-funded research project CHYLA (Credible HYbrid eLectric Aircraft) was to identify opportunities or limitations/challenges for the applications of key radical hybrid-electric technologies and areas suitable for scaling them over different aircraft classes. This was done using a ombination of conceptual aircraft design supported by sensitivity studies, credibility-based MDO and assessment of a regional operative scenario. This article summarizes the key findings from the project and presents the landscape of technology application areas. Notably, the regional and commuter classes present the largest design space with significant fuel-saving potential depending on the mission.@en