Nuclear-physical method to facilitate the landing of aircrafts

The application of gamma rays for guiding aircrafts on the landing approach offers advantages as compared with radioguiding methods: several radioactive preparations are at disposal as simple sources and the rays are hardly disturbed by weather and ground effects. With their aid, a system may be composed whose precision of guidance, in contrast to all existing methods, becomes more and more exact on approaching the landing ground. In the version of the experimental facility described, a 21-Ci of 60Co and a 25-Ci source of 137Cs from a simple shield on the ground emit two beams of rays with parallel axes at the desired landing angle towards an approaching helicopter. With the aid of three detectors, an electronic switch determines the slant range to the touch-down point (50 m in front of the radiation source) and the deviation with respect to the axis of the beam. The range of the experimental facility is about 500 m. A changed version is expected to give an increase up to 1,000 m. The radiation dose to the pilot approaching is so small that even if two sources with an activity of 25 curies are used, 40 landings per week are permissible without health physical monitoring. (orig.)