Half a Tube&Wing: Function-to-Form Mapping Approach to Understanding Fixed-Wing Civil-Aeroplane Design Space

An overwhelming abundance of innovative civil aeroplane concepts has been presented by the research community in recent decades. Their development has been motivated mainly by need for better operating energy, or in particular the fuel efficiency - the common objective variable for economic and environmental optimisation. This paper focuses on one common conceptual issue with the disruptive concepts which originates in remarkable divergence of the concept space in different directions away from the conventional Tube&Wing paradigm. As a consequence, it becomes increasingly difficult to make a meaningful comparison of any arbitrary pair of concepts by employing the conventional intuitions, definitions, or figures of merit. The objective of the paper is to elaborate a framework that could encompass the entire design space under a common conceptual umbrella. The method we employ relies on systems engineering principles of Function-to-Form mapping. Firstly, a comprehensive review of innovative concepts is provided, with emphasis on the problem of the apparent complexity of the design space arising from the conventional taxonomic intuitions. Then, the descriptive framework is presented, with relevant definitions of function, form and system architecture. First-order application of the framework to the conventional aeroplane design space implies that the Tube&Wing concept family can be represented as roughly one-to-one function-to-form mapping. By analysing the summarised pool of disruptive concepts in the same key, inference is made on existence of an extensive and continuous design space. Furthermore, and argument is presented for existence of the civil-aeroplane performance optimisation trend that aligns with parts of the design space moving away from one-to-one function-to-form mapping. In other words, parts of the design space moving towards the regions in which concepts map as many functions onto as few forms as possible. If extended to the entirety of the life cycle of the system, this framework could reveal even more possibilities for system optimisation, in line with contemporary socio-economic attempts to resolve potentially contradictory requirements and constraints of sustainable growth of the aeronautical industry.