Conceptual aerodynamic design of a 150-seat Prandtlplane aircraft

Kurzfassung

This conceptual design study of a 150-seat short-rang aircraft was undertaken to investigate whether a Prandtlplane (box-wing) configuration with a similar lifting surface area to an Airbus A320 could prove to be more efficient and feasible from an aerodynamic point of view than the A320. Using vortex lattice analysis via the well-proven Athena Vortex Lattice (AVL) software, a variety of geometric parameter sweeps were conducted in order to assess the influence of vertical wing separation, horizontal wing separation, aspect ratio, anhedral and dihedral, wing sweep and other such parameters on aerodynamic qualities such lift coefficient, induced drag coefficient, Oswald efficiency factor and ultimately the lift-to-drag efficiency of the configuration, while keeping the lifting surface area constant between all models in order to maintain comparability. The results found that for the Prandtlplane of this size, judicious design and a concept of a double-decker aircraft could bring up to almost 40% improvement in overall lift-to-drag efficiency for wings of the same span as the baseline aircraft. These kinds of staggering results demand further research, as does the fact that the most efficient configuration was in fact not a conventional Prandtlplane (with one aft-swept wing and one forward-swept wing) at all but a configuration incorporating two forward swept-wings with attached vertical endplates. This kind of configuration is not present in any design studies found before, and requires thorough verification and research before it can be recommended as the ideal configuration to pursue. In terms of the geometric sweeps conducted, the vertical separation was found to have the greatest influence, but also the horizontal separation was found to have an influence at short distance (leading to the biplane model). The version of the Prandtlplane with the wings fixed as having an aspect ratio equal to the baseline aircraft did not fare so well in the feasibility trials, but the aircraft with the same wingspan arrived at the results mentioned above. More research needs to be conducted and a multi-disciplinary design model considering both aerodynamic and structural effects needs to be developed alongside wind tunnel testing and flow visualisation to gain a better understanding of how these geometries might actually work in real life. Important stability and control issues also need to be considered but overall this kind of configuration holds great promise for future aircraft design.