The Radio Technical Commission for Aeronautics Special Committee 117, on A New Precision Approach and Landing Guidance System, was formed in late 1967 to develop a new precision guidance concept for approach and landing. The existing ILS, although in use since World War II, requires increased implementation now, and is only now being implemented in many parts of the world. There is a risk of delaying implementation of needed ILS service by public consideration of a successor system. Nonetheless, the present Instrument Landing System falls short of meeting the future requirements of fixed wing and VTOL/STOL aircraft, and literally dozens of new landing system ideas have been developed. The paper describes the efforts of RTCA SC-117 to select a new approach and landing guidance system. The Committee has concluded that an optimized scanning fan beam system can meet most of the operational requirements, and that such a system can be recommended with high confidence of practical success. The paper reviews some of the conclusions reached, and notes several of the most important problems facing the designers—such as frequency, data rate, and antenna requirements as they affect aircraft systems, as well as the tradeoff between demands of aircraft systems and limitations of radio systems.