DESIGN AND FLIGHT TEST RESULTS FOR MICRO-SIZED FIXED-WING AND VTOL AIRCRAFT

There has been recent interest in unmanned air vehicles with a largest linear dimension no greater than 6 inches. Micro sized air vehicles (µAV) are intended to operate close to a point of interest without detection and provide surveillance teams with critical information in life threatening situations that is currently not available in a rapid-deployment urban-environment mission scenario. This paper studies the importance of aerodynamics, propulsion, and mission requirements on the design of a µAV. A Multi-Disciplinary Optimization method is used to size µAV’s for a baseline mission. Sensitivity studies of the optimized designs identify features that most strongly affect its performance. Electric and internal combustion engine propulsion are compared. Results of these analyses show that large energy density, power density, and maximum lift capability are the most important features of successful µAV’s and that ICE power is superior to electric because of its larger power density. The results also show that increases in parasite drag due to low Reynolds number is of minor importance so long as lift capability is maintained. Maneuverability constraints have the strongest influence on µAV size because smaller turn radii require lower wing loadings and for a fixed weight this implies larger wing area and size. Three radio controlled prototypes of µAV’s were built and test flown based on the design study results. These vehicles are a 9 inch span electric powered fixed-wing, a 6 inch span ICE powered fixed-wing, and a 7 inch diameter ICE powered VTOL design. Each design has been flown successfully as a radio control aircraft and the flight test results revealed several unexpected difficulties relating to aircraft stability, control, and propulsion system integration. Further numerical analysis of the VTOL design shows that the size penalty for VTOL capability is negligible and that a 6 inch tail-sitter µAV can perform all of the mission requirements and operate in VTOL and translational flight modes.