The environmental impact of aviation in terms of noise and pollutant emissions has gained public attention in the last few years. In addition, the foreseen financial benefits of an increased energy efficiency have motivated the transport industry to invest in propulsion alternatives. This work is collocated within the Clean Sky 2 project GENESIS, focused on the environmental sustainability of 50-passenger hybrid-electric aircraft from a life-cycle-based perspective to support the development of a technology roadmap for transitioning towards sustainable and competitive electric aircraft systems. While several studies have already focused on the definition of possible aircraft designs combining several propulsion systems, the novelty of the present work is to consider technology forecasts and more comprehensive indicators in the design phase. These include the performance and emissions on a 200 nmi typical mission, which reflects the most economically attractive range for aircraft in the regional class. The work proposes a complete exploration of three major technology streams for energy storage: batteries, fuel cells, and turbine internal combustion engine generators, also including possible combinations of those technologies. The exploration was carried out through the execution of several designs of experiments aiming at the identification of the most promising solutions in terms of aircraft configuration for three different time horizons: short-term, 2025–2035; medium-term, 2035–2045; and long-term, 2045–2050+. As a result, in the short-term scenario, fuel energy consumption is estimated to be reduced by around 24% with respect to conventional aircraft with the same entry-into-service year thanks to the use of hybrid propulsive systems with lithium batteries. Fuel saving increases to 45% in the medium-term horizon due to the improvement in the energy density of storage systems. By the year 2050, when hydrogen fuel cells are estimated to be mature enough to completely replace kerosene-based engines, the forthcoming hybrid-electric aircraft promise no NOx and CO2 direct emissions, while being approximately 50% heavier than conventional ones.

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This paper proposes a feasibility study concerning a large turboprop aircraft to be used as a lower environmental impact solution to current regional jets operated on short/medium hauls. An overview of this market scenario highlights that this segment is evenly shared between regional turboprop and jet aircraft. Although regional jets ensure a large operative flexibility, they are usually not optimized for short missions with a negative effect on block fuel and environmental impact. Conversely, turboprops represent a greener solution but with reduced passenger capacity and speed. Those aspects highlight a slot for a new turboprop platform coupling higher seat capacity, cruise speed and design range with a reduced fuel consumption. This platform should operate on those ranges where neither jet aircraft nor existing turboprops are optimized. This work compares three different solutions: a high-wing layout with under-wing engines installation and both two- and three-lifting-surface configurations with low-wing and tail tips-mounted engines. For each concept, a multi-disciplinary optimization was performed targeting the minimum block fuel on a 1600 NM mission. Optimum solutions were compared with both a regional jet such as the Airbus A220-300 operated on 1600 NM and with a jet aircraft specifically designed for this range.