On the existence of a family of ideal aircraft configurations

Abstract

The overwhelming majority of all subsonic aircraft are based on the same configuration. However, this basic layout of wings and fuselage is perhaps not ideal in terms of flight efficiency. Assuming that better configurations may exist, alternatives have always been explored. Ever since the developmental priority has been focused on flight efficiency, large investments have been specifically committed to such research. If superior configurations do exist, as many results suggest, these should be implemented as a matter of urgency given the enormous environmental pressure imposed by the fast-growing aviation industry. However, until now, no consensus has been reached on which alternative to implement. To offer an alternative perspective on the old question of what an aircraft should look like, the aircraft design space was organised into families of configurations. For this purpose, a hypothetical ideal wing was introduced as a common ancestor in an imagined evolution of progressive complexity to organise configurations into families of different morphology. This approach allows for comparative evaluation at configuration level applying a new quantitative figure of merit without yet requiring exhaustive numerical optimisations. It was then hypothesised that a single family of configurations ought to be ideal for the majority of flight objectives, given that the shape for best efficiency must be a matter of physics alone, and given that typical flight objectives have much in common. While the current dominant aircraft configuration represents such a single family among the multi-wing arrangements, evaluation of its quality in terms of the new quantitative metric supports the widely held suspicion that it has avoidable deficiencies. Furthermore, within the design space, there exists a family of configurations among the single-wing arrangements that might be free of these deficiencies. This alternative has not been implemented in human aviation, leaving three high-level questions unanswered: (i) Could the configuration be implemented in aviation? (ii) How would it best be implemented? (iii) What improvement of flight efficiency can be gained by its implementation? The first question was explored in this research by qualitative evaluation of the handling qualities of the alternative wing layout and method of control by radio-controlled and full-scale tethered flight under direct human control. Other predicted flow effects around the alternative body arrangement were evaluated in wind tunnel tests. In conclusion, the notion of a single family of ideal configurations appears to be meaningful. Furthermore, because no practical hurdles have yet been found, the proposed arrangement seems to be a viable alternative to the current dominant configuration. Therefore, it seems justifiable to explore its potential further by dealing with the next two questions in future work.