In this paper, the modeling and control design of a vertical flight attitude control for a mini tail-sitter with variable pitch propeller is discussed. Tail-sitters VTOL-UAVs have operational flexibility of typical helicopters while having the cruise performance of fixed wing airplanes. The configuration proposed in this work is highly unstable in its natural flight state in vertical mode. A dynamic model is developed and a linear control strategy has been developed to stabilize the platform. The results are supported by experimental tests.