An effort is under way at NASA Langley Research Center to improve the pilot-machine interface with aircraft automation to increase the safety and utility of single-pilot instrument flight rules operations. An automatic terminal approach system (ATAS), that uses stored instrument approach data to automatically tune aircraft radios and control the aircraft autopilot, was conceived as a means of improving this critical interface. The ATAS automatically flies instrument approach procedures, including the missed approach, and provides for easy pilot interaction to accomodate air traffic control radar vectors and altitude assignments. A research prototype of an ATAS was developed to the extent necessary for a simulation implementation and piloted evaluation. This report describes the development of the ATAS concept and the software algorithms.