Methods for Accurate Measurements of Small Fixed Wing UAV Inertial Properties

Two methods have been compared for the determination of the inertial properties of a small, fixed wing UAV. The first method uses the standard single degree of freedom pendulum method and the second method implements a novel, potentially easier, three degree of freedom pendulum method, which yields the entire inertia tensor from a single swing test. Both methods are using system identification of the pendulum motion to estimate the inertial properties. Substantial corrections (up to 25%) have to be applied to the experimental results. These corrections are caused by the acceleration of the pendulum being immersed in the surrounding air, also called the added mass effect. It has been found that the methods presented in literature to determine the corrections for full scale aircraft do not give the correct results for the small scale UAV under consideration. The only feasible, costeffective method to generate these corrections utilise swing tests with a geometrically similar object of known inertial properties. It has also been found that the corrections are unique with respect to the experimental methods. Several benchmarking methods, including the innovative use of static and dynamic wind tunnel test data, give high confidence in the results.