This paper describes the development and evaluation of a new guidance system for unmanned helicopter. The trajectory planning technique combines a receding horizon trajectory optimization based on mixed-integer linear programming with a global cost-to-go maps computed in near real-time using dynamic programming. The resulting system allows for complex, long-range mission scenarios that involve dynamically changing features. The paper gives a full description of the capabilities and functions supported by the planner software. Hardware-in-the-loop simulations were used to evaluate and demonstrate the system's performance and capabilities; the final paper will also include results from the flight-test demonstration on a Boeing Renegade unmanned helicopter.