In this paper, an innovative methodology for the conceptual design of hybrid-powered airplanes is proposed. In particular, this work focuses on parallel hybrid architectures, in which the thermal engine is mechanically coupled to an electric motor, both supplying propulsive power during a limited number of flight phases, e.g. during takeoff and climb. This innovative solution is the subject of several studies being carried out since the current decade. In this paper, a brief overview of the works conducted by other researchers is provided. Then, an overall aircraft design methodology is proposed, which is derived from the most renewed design algorithms. The original contribution of this work is represented by the development of a methodology for the design of hybrid propulsion systems. Moreover, the proposed method is integrated within a global aircraft design methodology. In particular, several effects of the innovative system on the entire aircraft are considered, for instance the variation of the empty mass or the impacts on fuel consumption. The paper ends with some case studies of the proposed design methodology, and a discussion of the obtained results is provided.

The article proposes the design of a test bench simulator to test a parallel hybrid propulsion architecture for aeronautical applications. The virtual test bench simulates, in a scaled version, the real test bench, designed for a power of about 0.4 MW. After presenting the architecture of the real propulsion system, the virtual test bench is described. The real system is basically composed by a paralleled electric motor and thermal engine which provide mechanical power to the propeller. Saving cost and volume the test bench is composed by electric motors simulates the behaviors of the real propulsion system despite their differences. The dynamic relationships expressing the transmission of torque between the components, and the method of down-sizing the power delivered are highlighted. Particular attention is given to the real inertia actions that must be simulated on the virtual test bench. An application of the proposed methodology is then presented through the simulation of the take-off phase, and the torque time histories, angular velocities and powers generated on the virtual test bench are used to verify the corresponding time histories expected in the real system.

An innovative aircraft preliminary design environment is presented, in particular highlighting the impacts of on-board systems design discipline on the Overall Aircraft Design, especially in terms of mass changes and fuel consumptions. The design environment has been conceived and set up during a collaboration between Politecnico di Torino and the German Aerospace Center (DLR - Hamburg). The entire design workflow is presented, focusing the attention on the subsystems design module, an in-house tool named ASTRID, developed at Politecnico di Torino. ASTRID is conceived to design both conventional and innovative systems, as hybrid-electric propulsion systems and More Electric and All Electric architectures. In particular, from the design modules of the proposed environment, system masses and secondary power levels are obtained, hence pointing out the system design effects on aircraft weights and fuel consumptions. Two case studies are presented. The first one refers to the preliminary design of a general aviation aircraft equipped with a hybrid-electric propulsion system. Several variants are designed varying the degree of hybridization, meant as the ratio between the electric power and the total propulsive power. The second case study is centered on four 90-passengers civil airplane designs with the same stakeholders' requirements but different on-board systems technology levels - i.e. ranging from a conventional architecture to the All Electric Aircraft, passing through two More Electric configurations. Each design affects differently the aircraft empty weight and the required mission fuel. At the end of the designs, it is assessed that a high degree of hybridization, around 35%, entails a drastic fuel reduction, marking the significant benefits of this innovative technology. Concerning the second case study, the most innovative concept, the All Electric Aircraft, is characterized by a significant fuel reduction due to the more efficient power off-takes and a lower empty weight compared to the traditional architecture, hence returning a lower Maximum Takeoff Weight

The on-board systems are having even more importance in aircraft design since the continuous research for a competitive, more optimized and less costly aircraft. In addition, the introduction of new technologies related to the More Electric Aircraft and All Electric Aircraft concepts have raised the interest on on-board systems discipline giving the option of analyzing different architectures. The present paper would enhance the selection of the best on-board systems architecture introducing a new workflow, which is able to identify the best architecture in terms of procurement and operating cost. Since the importance of fuel required providing the secondary power, the effect of each specific architecture on engine performance is particularly considered including a detailed engine module. The workflow is implemented in Optimus framework within a collaborative and multidisciplinary environment and it is open to be integrated with additional modules increasing the fidelity of the analysis. To explore the capability of the defined workflow, the H2020 AGILE regional jet is identified as test case

A Collaborative and Distributed Multidisciplinary Design Optimization (MDO) methodology is presented, which uses physics based analysis to evaluate the correlations between the airframe design and its sub-systems integration from the early design process, and to exploit the synergies within a simultaneous optimization process. Further, the disciplinary analysis modules involved in the optimization task are located in different organization. Hence, the Airframe and Subsystem design tools are integrated within a distributed overall aircraft synthesis process. The collaborative design process is implemented by making use of DLR's engineering framework RCE. XML based central data format CPACS is the basis of communication to exchange model information between the analysis modules and between the partner organizations involved in the research activity. As a use case to evaluate the presented collaborative design method, an unmanned Medium Altitude Long Endurance (MALE) configuration is selected. More electric sub-systems combinations based on the mission requirements are considered. The deployed framework simultaneously optimizes the airframe along with the sub-systems. DLR's preliminary aircraft design environment is used for the airframe synthesis, and the Sub-systems design is performed by the ASTRID tool developed by Politecnico di Torino. The resulting aircraft and systems characteristics are used to assess the mission performance and optimization. In order to evaluate the physics based framework and system-airframe synergies, three case studies are considered: a) Subsystem Architecture's effect on overall aircraft performance for a given mission and fixed airframe. b) Effects of variation of mission scenario on aircraft performance for a chosen subsystem architecture and fixed airframe. c) Optimization involving wing planform variables and subsystem architecture for a given mission