Towards a Low-Speed and Highly Agile UAV Through a Novel Fuselage Design, Slender Leading-Edge Extensions and the Wake-Ingestion Concept

Presently, there is a strong demand for light, economical, and highly maneuverable UAVs that, when operating independently or in a swarm formation, can replace expensive manned platforms. Such applications include emergency response and firefighting in areas such as canyons or rugged terrain, where the agility of the aircraft is mandatory. Moreover, such UAVs can serve as test benches for flight-control systems of general aviation aircraft (A/C) in emergencies, such as high-g/high-angle-of-attack (AoA) regimes. To this end, a new low-subsonic (Reynolds number ≈4 million) fixed-wing UAV concept is proposed herein, aiming for high maneuverability in the category of low-subsonic-speed and light (up to 200 kg) UAVs. Its characteristics are a variation of the prolate spheroid (6:1 aspect ratio) fuselage for low-drag cruise flight, a non-slender delta main wing for high structural strength, and the integration of a powerplant, i.e., electric ducted fans (EDFs), close to the wing to enhance the aero-propulsive performance of the A/C. The latter is achieved through proper manipulation of the generation and evolution of the leading-edge vortices (LEVs) over the wing by the suction produced by the EDFs. The computational fluid dynamics (CFD) code used herein is OpenFOAM-v2412, and the simulations are implemented on a high-performance computing platform. The numerical simulations indicate that the proposed A/C, which uses concepts such as leading-edge extensions (LEXs) for lift augmentation, wake ingestion, and a novel LEV manipulation method, can be highly agile and economical in the sense that it is inherently stable and does not require expensive flight-control systems for stabilization. In addition to its aerodynamic performance, the A/C also uses design concepts conducive to a low radar cross-section (RCS).