An Aerodynamic Data System for Small Hovering Fixed-Wing UAS

Small fixed-wing UAS that are able to hover combine the station keeping abilities of a rotary wing platform and the extended range of conventional aircraft. Current autopilots for these vehicles rely on inertial measurements plus airspeed to transition from forward flight to hover, accumulating appreciable position error during the transition. Once in hover, a combination of inertial and GPS data is used for station keeping. By combining additional real-time aerodynamic data with traditional inertial measurements, the aircraft can maintain high angle-of-attack operation for controlled slow flight and execute forward/vertical flight transitions closer to stall. Such a capability can expand the autonomous maneuver repertoire as well as improve accuracy at which existing maneuvers are conducted. This paper describes the design, implementation, and testing of a small-scale aerodynamic data system augmenting a traditional inertial navigation system. Collected aerodynamic data includes angle of attack, sideslip angle, airspeed, and pressure distribution along the wing chord. Wind tunnel tests verify the calibrated air-data probe can measure angles of attack from -75° to 75° and sideslip angles from -45° to 45°. The aerodynamic-inertial data system was incorporated into a Funtana hobbyist airframe with thrust exceeding weight. Flight test results from a series of forward-hover transitions are presented, along with requisite guidance and flight control laws for autonomous operation.