Modeling Propeller Aerodynamics and Slipstream Effects on Small UAVs in Realtime

Abstract

This paper focuses on strong propeller effects in a full six degree-of-freedom (6DOF) aerodynamic modeling of small UAVs at high angles of attack and high sideslip in maneuvers performed using large control surfaces at large deflections for aircraft with high thrust-to-weight ratios. For such configurations, the flight dynamics can be dominated by relatively large propeller forces and strong propeller slipstream effects on the downstream surfaces, e.g., wing, fuselage and tail. Specifically, the propeller slipstream effects include propeller wash flow speed effects, propeller wash lag in speed and direction, flow shadow effects and several more that are key to capturing flight dynamics behaviors that are observed to be common to high thrust-to-weight ratio aircraft. The overall method relies on a component-based approach, which is discussed in a companion paper, and forms the foundation of the aerodynamics model used in the RC flight simulator FS One. Piloted flight simulation results for a small RC/UAV configuration having a wingspan of 1765 mm (69.5 in) are presented here to highlight results of the high-angle propeller/aircraft aerodynamics modeling approach. Maneuvers simulated include knife-edge power-on spins, upright power-on spins, inverted power-on pirouettes, hovering maneuvers, and rapid pitch maneuvers all assisted by strong propeller-force and propeller-wash effects. For each case, the flight trajectory is presented together with time histories of aircraft state data during the maneuvers, which are discussed.