This paper focuses on full six degree-of-freedom (6-DOF) 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. Configurations such as this include many of the currently available propellerdriven RC-model airplanes that have control surfaces as large as 50% chord, deflections as high as 50 deg, and thrust-to-weight ratios near 2:1. Airplanes with these capabilities are extremely maneuverable and aerobatic, and modeling their aerodynamic behavior requires new thinking because using traditional stability derivative methods is not practical with highly nonlinear aerodynamic behavior and coupling in the presence of high propwash effects. The method described in this paper outlines a component-based approach capable of modeling these extremely maneuverable small UAVs in a full 6-DOF realtime environment over the full envelope that is defined in this paper to be the full ±180 deg range in angle of attack and sideslip. This method is the foundation of the aerodynamics model used in the RC flight simulator FS One. Piloted flight simulation results for four small RC/UAV configurations having wingspans in the range 826 mm (32.5 in) to 2540 mm (100 in) are presented to highlight results of the high-angle aerodynamics modeling approach. Maneuvers simulated include tailslides, knife edge flight, high-angle upright and inverted flight ("harriers"), rolling maneuvers at high angle ("rolling harriers") and an inverted spin of a biplane ("blender"). For each case, the flight trajectory is presented together with time histories of aircraft state data during the maneuvers, which are discussed.
Nomenclature,c/4 = moment coefficient about quarter chord D = drag; propeller diameter J = propeller advance ratio based on V N L = lift M = pitching moment about y-axis (positive nose up) n = propeller rotational speed (revs/sec) * Associate Professor, Department of Aerospace Engineering, 104 S. Wright St. Senior Member AIAA.= propeller yawing moment due to angle of attack p, q, r = roll, pitch and yaw rate P N = propeller normal force due to angle of attack Q = propeller axial torque q = dynamic pressure (ρV 2 /2) R = propeller radius S = reference area T = propeller axial thrust u, v, w = components of the local relative flow velocity along x, y, z, respectively V = flow velocity x, y, z = body-axis coordinates, +x out nose, +y out right wing, +z down y c = airfoil camber TED = trailing edge down TEL = trailing edge left TEU = trailing edge up Subscripts N = normal component R = relative component Symbols α = angle of attack (arctan(w/u)) β = sideslip angle (arcsin(v/V )) β ′ = angle of attack for vertical surface (arctan(v/u)) δ a = aileron deflection [(δ a,r − δ a,l )/2], right +TEU, left +TEU δ e = elevator deflection, +TED δ r = rudder deflection, +TEL ǫ = wing induced angle of attack η s = dynamic pressure ratio for flow shadow (shielding) effect φ, θ, ψ = bank angle, pitch angle, heading angl...