GB579167A - Improvements in or relating to direction-indicating apparatus for facilitating the navigation of craft - Google Patents

Abstract

579,167. Navigation systems for aircraft &c. TAPP, E. T. J., and RADIO ELECTRONICS, Ltd., (formerly VACUUMSCIENCE PRODUCTS, Ltd.). Dec. 15, 1942, No. 17842. [Classes 40 (iii) and 40 (v)] [Also in Group XI] A course for an aircraft &c. is marked by a narrow composite beam of light or infra - red rays having different parts of the beam differently modulated. As shown, three searchlights 11 produce overlapping beams, Fig. 2, the beams being modulated at different audio frequencies. The receiver on the craft comprises an electron-multiplier 8 with a photo-sensitive cathode, coupled to headphones 3. Single notes corresponding to one of the modulations will be heard in the outer areas 13 ... 15, two-note chords in the areas 16 ... 18, and a three-note chord in the central area 19 corresponding to the correct course. Alternatively, a central beam marking the course may be surrounded by a number of beams partly overlapping it and each other. An additional horizontal beam from a source 21 may indicate the height at which an aircraft should flatten out for landing. The arrange-, ment may be supplementary to a radio landing system of the overlapping-beam type provided with marker beacons 22, 23, the same headphones being used for all signals. The searchlights 11 may be mounted in a well 10 having a grating 12 or a pivoted cover-plate with a reflecting under surface, automatic means being provided in this case for closing the plate on the approach of aircraft wheels. Alternatively, the searchlights may be mounted above ground and may be automatically lowered into the ground if an aircraft approaches too near. Three searchlights 24 ... 26, Fig. 3, may be mounted in a triangular frame 33 rotatable vertically about a base 53 and horizontally about an axis 35, the angle of divergence of the composite beam being also adjustable by mounting the searchlights on links 40, 41 pivoted to the frame 33 and to a central plate 46 adjustable axially by a screw 47. The modulation of the beams may be effected by shutters of the kind described in Specification 573,900. In modifications, a single searchlight has three spaced shutters, Fig. 4 (not shown), or three coaxial shutters with annular shutter elements, Fig. 5 (not shown). On an aircraft carrier, the searchlight assembly may have a gyroscopic control to maintain the beam at a fixed angle to the horizontal.