On-Board Systems Preliminary Sizing in an Overall Aircraft Design Environment

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.