The design and experimental control of an unmanned Tilt-Rotor aerial vehicle operating in Bi-Rotor mode is presented in this article. Tilt-Rotor UAVs exhibit important flight characteristics due to their ability to fly both like a rotorcraft (in Bi-Rotor Mode) and like a fixed-wing aerial system. The ability of having a dual flight envelope makes ideal for complex missions where both the speed and flight endurance of a fixed-wing design and the hovering, aggressive maneuvering and vertical take-off/landing capabilities of a helicopter are needed. In the work presented, the main design principles, the Bi-Rotor mode nonlinear/linearized dynamics and the corresponding attitude tracking controller design are exhibited. Experimental studies in attitude stabilization indicate the overall system and controller's efficiency in hovering operation.