Aerodynamic Sensing for a Fixed Wing UAS Operating at High Angles of Attack

The flight profile of typical small unmanned air systems (UAS) has expanded in the last decade beyond those encountered by traditional fixed-wing transport and rotary-wing aircraft. These new flight conditions may involve unusual flight mechanics as with flapping wing flight or complex aerodynamics when performing difficult maneuvers as part of routine operations. Such scenarios typically involve unsteady and inherently non-linear aerodynamics that challenge current autopilots relying primarily on inertial measurements and GPS data. The addition of aerodynamic feedback to the current UAS sensing and control framework can enable the autopilots of aircraft operating under such conditions to better achieve their control objectives and expand their autonomous flight capabilities. This paper describes the ongoing development of a pressurebased aerodynamic data system for a fixed wing UAS operating at high angles of attack. Expansions to the aerodynamic instrumentation package based on flight test results are described. These include an expanded set of wing pressure ports and a custom designed multi-hole probe for prop-wash estimation. Autonomous flight test data from the first generation UAS system transitioning between cruise and hover are presented and discussed. Open loop flight data acquired using the upgraded sensing concept is then presented. Flight test results show that the sensing package provides data that is complementary to a typical Inertial Measurement Unit and can support the development of feedback control strategies based on aerodynamic measurements.