This paper presents the modeling and control of a passively-coupled tilt-rotor vertical takeoff and landing aircraft. The aircraft consists of a quadrotor frame attached to a fixed-wing aircraft by an unactuated hinged mechanism. The platform is capable of smooth transitions from hover to forward flight without the use of tilting actuators. The transition from hover to forward flight is made possible by differential thrust between the fore and aft propellers of the quadrotor frame. In this paper, the coupled dynamics between the quadrotor frame and the aircraft frame are modeled as a constrained multi-body system. The equations of motion are established using a constrained Lagrangian approach and the model developed is used to build a realistic simulation environment for control design purpose. A cascaded control architecture based on P/PID controllers is proposed to achieve inner-loop attitude, height and forward velocity control. Simulated and experimental results are obtained with a close match for hover, transitions, forward flight, and banked turn maneuvers.