Evaluating the Accuracy of Conventional Drag Prediction and Validation Methods for Small Electric UAVs

Abstract

The cost-effectiveness and versatility of unmanned aerial vehicles (UAVs) has led to an increase in demand for small, fixed-wing, electric aircraft. Aircraft performance characteristics such as flight time, efficiency, and turn performance rely on the amount of air resistance that the vehicle experiences. The force caused by air resistance is known as the drag force, and accurate drag predictions are essential to aircraft design, control, and mission planning. This study seeks to evaluate the accuracy of calculating the drag of small electric UAVs using a common empirical method for fixed-wing aircraft, and to determine the efficacy of using glide tests to validate drag values. Glide tests are performed to measure drag of three aircraft, and wind-tunnel testing conducted to measure the drag generated by windmilling propellers. The component drag build-up method is then implemented to analytically determine drag, and the results compared to the data. It is demonstrated that by accounting for the unique operating conditions of small UAVs, the component drag build-up method can be used to accurately determine drag. It is also shown that glide tests are an effective method to experimentally determine drag and validate predicted values.