Contrary to the manned tailsitter aircraft concepts, which have been shelved and forgotten after mid 1960's, the unmanned versions of these concepts have become popular. Since, tailsitter type UAVs combine both vertical takeoff and landing (VTOL) operation and relatively high speed cruise flight capabilities which provide manifest advantages over the other VTOL aircraft concepts, including helicopters and organic air vehicles (OAVs). However, there is no mini class tailsitter UAV with efficient high speed cruise flight capability. This paper presents the design methodology and optimization of ITU Tailsitter UAV concept with hybrid propulsion system approach to fill that gap. The initial design and analysis show the advantageous performance over other mini-class VTOL UAVs.