The potential benefits of hybrid-electric or all-electric propulsion have led to a growing interest in this topic over the past decade. Preliminary design of propulsion systems and innovative configurations has been extensively discussed in literature, but steps towards higher levels of technological readiness, optimisation algorithms based on reliable weight estimation and simulation-based mission analysis are required. This paper focuses on the integration of a method for evaluating the lateral-directional controllability of an aircraft within a design chain that integrates aero-propulsive interactions, accurate modelling of the fuel system, and mid-fidelity estimation of the structural weight. Furthermore, the present work proposes a strategy for powerplant management in scenarios with an inoperative chain element. Benefits of hybrid-electric propulsion on the design of the vertical tail plane are evaluated involving the analysis of multiple failure scenarios and certification requirements. The proposed application concerns a commuter aircraft.

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 interest in environmental sustainability motivates the search for disruptive technologies and concepts. However, the lack of conceptual design methods capable of capturing the effects of new propulsive technologies is the main obstacle, often due to the absence of industrial data to support research. In this context, the Clean Sky 2 ELICA (ELectric Innovative Commuter Aircraft) project aims to fill this gap, supporting research with industrial expertise and exploiting a 19-seat commuter aircraft as a technological test bed. This paper aims to present the main results obtained in the investigation of the potential of a full-electric propulsion entirely based on fuel cell systems. After an overview of the main propulsion system modeling techniques used to pursue the objective, three different configurations will be compared, each with a different powerplant, aerodynamic characteristics and weights. The comparison will allow to highlight the real benefits of the aero-propulsive interaction, including effects impossible to quantify except with an approach based on flight mission simulation.

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.

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.

The potential benefits of hybrid-electric or full-electric propulsion have led to the proliferation of many concepts over the past decade. However, in most cases, concepts are referred to aircraft designed starting from early stages of the design process requiring a specific manufacturing chain. This could lead to aircraft which are less appetible in an industrial or economic sense. The present work proposes a complete application of the design process proposed by the authors in recent publications to refit the propulsive system of an already flying regional turboprop. The hybridization process requires the evaluation of many different powertrain architecture to find the most suited to maximize the fuel saving percentage. The resize of thermal and electric components is based on the power requirements provided by a simulation-based analysis of the mission profile. The reference aircraft is similar to ATR-42.

– The work introduces a preliminary design chain valid for hybrid-electric, full-electric, and thermal powered aircraft. From early stages of the design process, the integration of aero-propulsive interaction between propeller (or fan) slipstream and airframe is an important step to obtain trends and compare different aircraft. The present work integrates in the design chain both the distributed propulsion and tip-mounted propeller interactions, deriving for the latter effect a simple model suitable for point performance estimation. The research activity is oriented by market and political demands. Derived from these requirements, two different applications of the design process are proposed on FAR/CS-25 and FAR/CS-23 certified aircraft. Trends about the possible applications, benefits, and drawbacks show that, with the current technology state of the art, a full-electric aircraft is still unfeasible, unless a design range of 100 nmi is acceptable.

The potential benefits of hybrid-electric or full-electric propulsion have led to an increased interest in this topic over the past decade. Hence the need to develop modern and innovative methods to analyze the performance of aircraft with unconventional propulsion systems. The purpose of this paper is to describe and apply a simulation-based algorithm integrating aeropropulsive effects for the mission analysis of conventional, hybrid-electric, and full-electric aircraft. The method composes the analysis toolbox of the aforementioned software, HEAD (Hybrid-Electric Aircraft Designer), developed by the DAF Research Group. Analysis toolbox has to perform a detailed mission simulation of a generic airplane. The proposed application deals with the evaluation of the effects on performance that wingtip-mounted propellers and distributed electric propulsion on regional turboprop category. The reference aircraft is similar to an ATR-42.

A comprehensive developed conceptual design and analysis tool is here employed in the design of hybrid electric 19 passenger’s commuter aircraft. Particular attention is payed to the regulation under which aircraft must be certified. The sizing activity accounts for the aero-propulsive interactions when distributed electric propulsion is present. Output of this activity are the energetic requirements and the mass breakdown, by combining the free choice of the designer with aviation regulations and requirements. The application here presented provides parametric studies based on different operating combinations of distributed electric propulsion and e-storage. The aim of the present work is the identification of a design range which would make the choice of the new technologies profitable. The most promising result is a full-electric concept having 16 distributed propellers and designed for a flight mission of 200 nmi certifiable under FAR-23 (or CS-23) regulation.

The paper presents a thorough conceptual design approach for a generic aircraft with conventional, hybrid-electric, or full-electric powertrain. It follows the steps of classic aircraft design methods, including the main aspects related to the hybridization of an aircraft: powertrain architectures, energy sources, aerodynamic-propulsive interactions, stability and control effects. Such aircraft is designed considering design and regulations requirements. Three are the main steps of the conceptual design approach presented: preliminary design, sizing, and analysis. The first step provides a statistical baseline, including both geometry and weight breakdown, moving from top-level requirements. The sizing activity provides the energetic requirements and the mass breakdown, by combining the free choice of the designer with aviation regulations and requirements. The subsequent analysis aims to choose the baseline for high-fidelity optimization. The first application of the presented workflow deals with regional turboprop aircraft and it is based on the ATR-42 design mission. However, in the present work, a further investigation of the possible concepts, based on different design missions, highlights that the competitiveness of hybrid-electric aircrafts cannot be based on the same mission profiles on which nowadays aircrafts have been designed.