Modeling, guidance and control experimental results for a small unmanned aerial vehicle (UAV) are presented. The numerical values of the aerodynamic derivatives are computed via the Digital DATCOM software using the geometric parameters of the airplane. A hardware-in-the-loop (HIL) simulation environment is developed to support and validate the small UAV model autopilot hardware and software development. The HIL simulation incorporates a high-fidelity dynamic model that includes the sensor and actuator models, the test bed HIL system used to facilitate the development of the flight control system (FCS). Furthermore, design of the guidance laws, autopilot implementation on the embedded system are integrated with the HIL simulation. A mission has been design in order to validate the guidance and control loops. Finally, a user friendly graphical interface that incorporates external stick commands and 3-D visualization of the vehicle's motion completes the simulation environment.