A simulation environment is developed to assist in the design, development, and validation of complex controllers with applications to mini-UAVs, such as the four-rotor DraganFly RC helicopter (quadrotor). The simulation system is modular and includes interfaces which allow for substitution of software subsystems with hardware components. This approach enables a smooth transition from the design and simulation phases to the implementation phase. The benefits of the proposed simulation environment are examined through the application of model reference adaptive control to a quadrotor UAV in the presence of actuator uncertainties and nonlinearities.