VTOL Fixed wing UAVs - Some characteristics of tailsitter vehicles

This report describes some general characteristics of tailsitter vehicles as a subcategory of Vertical Take off and Landing (VTOL) - fixed wing (FW) UAVs. The most common variants of tailsitter vehicles are described, as well as examples of development projects in the past. Tailsitters have advantages as well as disadvantages compared to more conventional horizontal VTOL-hybrid vehicles. As an example, tailsitters usually employ the same propulsion system in VTOL flight as is used in fixed wing forward flight. It can therefore be challenging to achieve high energy efficiency in both flight modes. Some aspects of how tailsitters respond to wind in VTOL-mode are also included in the report.