Glide path system

596,440. Radio navigation. STANDARD TELEPHONES & CABLES, Ltd. Feb. 16, 1945, No. 4030. Convention date, May 1, 1944. [Class 40 (v)] In a glide-path landing system'similar to that described in Specification 590,491 in which two vertically-spaced aerials arranged laterally of the runway produce patterns having a lobe 16, Fig. 2, of the lower aerial pattern L coinciding with a null of the upper aerial pattern U, and in which a carrier and modulated side-bands are transmitted by the lower aerial and side-bands only by the upper aerial in such a way that the areas on either side of the course-line are characterized by different audiofrequencies, the glide-path is progressively softened towards the runway 31, Fig. 5, by arranging the horizontal distributions of the patterns L, U so that the energy level in the pattern L increases with respect to that in pattern U as the runway is approached. This may be effected by suitably modifying the directive characteristics of the aerials by associated reflectors arranged at different angles. Thus, with the horizontal distribution of the patterns L, U shown in Fig. 5, the ratios of energies received by an aeroplane 32 at successive positions B, A, PG are respectively OE/OD, OG/OF and ON/OM.