Scaling Laws for Empirical Tailsitter Design

Tailsitter unmanned arial systems (UAS) are promising as the architecture combines the benefits of multirotor vertical takeoff and landing (VTOL) capabilities with the efficiency of fixed-wing forward-flight aircraft. Upward-facing rotors generate lift required for VTOL and the aircraft transitions to forward flight by rotating approximately 90 degrees about the pitch axis so the wings, integral to the aircraft architecture, generate lift for efficient forward flight. However, the complex and non-linear transition dynamics and tail-less architecture of tailsitters makes the design scaling rules for the design of such aircraft challenging. This study aims to close the knowledge gap by developing a set of empirical scaling rules for tailsitters, which can be used as the starting points for designing future UAS. Parameters including payload mass, battery mass, electronic mass, and wing sizing are organized into scaling laws which were correlated to the takeoff weight. The relations between structural weight and takeoff weigh are also empirically established, which is crucial for the preliminary design but is lacking from current literature. Additionally, the range and endurance of UAS tailsitters up to 25 kg made of common off-the-shelf parts were estimated using these results. Finally, as a case study, the scaling laws were applied to the design of a 5 kg tailsitter with a 1 kg payload. The detailed design includes choosing wing shape and size, selecting airfoil type, shaping payload bay, and determining structural layout. The vehicle was weighed and tested for validation of the scaling laws.