Flight at high angle-of-attack conditions, which range beyond wing stall, has numerous advantages for mission performance; however, that flight regime is often affected by adverse behaviors. A particularly notable behavior is associated with uncommanded oscillations primarily about the roll axis and is known as wing rock. This paper investigates wing rock for a small, propeller-powered aerobatic unmanned aerial vehicle with a high degree of vertical symmetry flown at high angle-of-attack conditions. Most importantly, the investigation characterizes the nature of wing rock as a function of size and configuration of the vertical tail. The flight data indicate that wing rock is dependent on the configuration but not on the size of the vertical tail: wing rock oscillations are present for upright but not inverted regardless of vertical tail size. Furthermore, a time-frequency analysis indicates that the wing rock is actually a narrowband phenomenon for which the central frequency varies with time.

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The angle-of-attack parameter has a significant influence on the aerodynamics and resulting flight dynamics of aircraft. Flight at high angle-of-attack conditions enables many missions; however, the flight dynamics are challenging to model. This paper investigates the flight dynamics for a small UAV that is piloted in open air at high angle-of-attack conditions. Models are estimated from the flight data to indicate some characteristics of the flight dynamics. The lateral dynamics are linear while the longitudinal dynamics and directional dynamics exhibit nonlinearities and high-order terms. Additionally, the magnitude and energy of wing rock is determined for the lateral dynamics.

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