This paper deals with the definition of an improved powertrain model for hybrid-electric aircraft. It is well known that powertrain equations are one of the most convenient tools for modelling the propulsion system at aircraft level, when it comes to hybrid architectures characterized by more than a single propulsive source. However, for a reliable implementation of a robust optimization algorithm for the hybridization parameters, the designer should consider some singularity points related to certain non-physical configurations depending on the operating mode. In this work, singularities are firstly identified by analyzing the operating modes, then a solving strategy is reported. Another crucial aspect is the correct design and simulation of battery behavior. In a broader perspective, the high-level objective of the activities related to powertrain model is to assess a possible fuel saving for regional turboprops using e-storage units as secondary power source. In this respect, preliminary results in terms of flight performance referred to a regional aircraft similar to ATR42 are presented and discussed. The authors conclude that a block fuel saving up to 51% for the typical mission is possible with a battery specific energy of 500 Wh/kg and when the benefits of aero-propulsive interaction are fully exploited.

A design chain for preliminary design of hybrid-electric and full-electric aircraft allowed to explore different possible innovative concepts aiming to find out the best configuration with respect to top-level requirements. The aim of this work was to opportunely describe how it was possible to obtain a high-fidelity estimation of mass and stiffness properties for main wing components (spars, ribs, skin and stringers). The configuration under consideration hereinafter is a full-electric configuration of a commuter 19 passengers, which provides for 8 electric motors distributed along the wingspan, with two tip electric motors as a primary propulsive system. The design starting point was the estimation of flight loads, which come out from V-n diagram. Afterwards, in order to refine the first level weight estimation (based on analytic method) a dedicated high-fidelity structural analysis was performed, which allowed a higher-fidelity strength assessment as well. This approach allowed to verify the structural efficiency of the wing within the aircraft flight envelope and to optimize the structure components.

The growing sensitivity to the problem of sustainability requires a rethinking of how aviation is typically conceived by modern society. The aim of the research today must be to analyze the feasibility of disruptive solutions, which drastically reduce consumption and make it possible to meet the growing demand in the commercial aviation sector. The current level of technological maturity does not allow direct implementation on large commercial aircraft, which are responsible for most of the emissions from aviation. In this context, the Clean Sky 2 ELICA project aims to trace a technological roadmap towards green aviation, using the Small Air Transport as a test bed. Two different 19-seat commuter aircraft are presented in this work. The first one, with entry into service in 2025, presents a hybrid-electric architecture with batteries. The second configuration, with entry into service in 2035, is entirely propelled with hydrogen fuel cells, allowing the direct emissions of carbon and nitrogen oxides to be totally eliminated. Both configurations benefit from distributed electric propulsion.