Design Model Validation for Small UAS VTOL using Flight Test Data

There is growing interest in development of fixed-wing small unmanned aircraft systems (sUAS) that have vertical takeoff and landing (VTOL) capabilities for both military and civilian applications. To quickly and effectively design fixed-wing VTOL sUAS such that the end product performs as intended, a validated, low-computational-cost model of weight and propulsive performance is necessary. This study develops one such model by implementing a componentbased weight build-up, low-order drag build-up, momentum theory propeller model, and an empirical approach to motor and electronic speed controller (ESC) efficiencies at relevant scale. To select appropriate subcomponent models and validate, three sUAS VTOL vehicles of different configurations were developed and flown in both hover and forward flight. The vehicles’ components were broken down by weight, and those weight breakdowns were compared with the weight model predictions. Design model predictions of power draw in hover and forward flight were validated with measured power draw during flight testing in relevant conditions. Predicted power draw for all three configurations was within 13.1% of mean test data results for hover and 19.4% of mean test results for forward flight. The predicted total weight comparison for all three configurations was within 8.7%. Predictions were found to be most sensitive to the assumed motor, ESC, and propeller efficiencies, RPMs, and accurate prediction of fuselage drag.