The Ames Research Center initiated a program in 1975 to provide the critical information required for the design of integrated avionics suitable for general aviation. The program has emphasized the use of data busing, distributed microprocessors, shared electronic displays and data entry devices, innovative low-cost sensors, and improved functional capability. Design considerations include cost, reliability, maintainability, and modularity. As a final step, a demonstration advanced avionics system is being designed, fabricated, and flight tested. The purpose of this paper is to provide a functional description of the Demonstration Advanced Avionics System including a description of the system architecture in order to document the direction that the program is taking.