Unmanned aerial vehicles (UAVs) are remotely piloted or self-piloted aircrafts that can carry cameras, sensors, communication equipment and other payloads. Tiltrotor UAVs provide a unique platform that fulfills the needs for ever-changing mission requirements, by combining the desired features of hovering like a helicopter and reaching high forward speeds like an airplane, which might be a force multiplier in the battlefield. In this paper, the conceptual design and aerodynamical model of a realizable small-sized Tiltrotor UAV are presented, and the linearized state-space models are obtained around the trim points for airplane, helicopter and conversion modes. Controllers are designed using tracking optimal control method and gain scheduling is employed to obtain a simulation for the whole flight envelope. An interactive software infrastructure is established for the design, analysis and simulation phases, based on the theoretical concepts. © 2011 The Society for Modeling and Simulation International.