Improvements in or relating to radio signalling systems for use for navigating and landing aircraft in fog

摘要

377,624. Wireless signalling. TELEFUNKEN GES. FUR DRAHTLOSE TELEGRAPHIE, 12, Hallesches Ufer, Berlin. April 4, 1932, No. 9664. Convention date, April 2, 1931. [Class 40 (v).] A system for facilitating the landing of aircraft, comprises four directional transmitters radiating concentrated beams of constant strength from outside the landing space in four mutually perpendicular directions over the landing space on the same wave-length and with different modulation frequencies. As described a circular landing space u is traversed by four concentrated beams of radiation Sn, So, Ss, Sw directed from the north, south, east and west respectively being produced by transmitters sn, so, ss, sw respectively placed outside the space. The boundaries of the beams are taken as surfaces on which a particular field strength h exists which produces a particular deflection of an indicator in the aircraft receiver. The spread of the beams in the horizontal direction is not greater than 30‹ and in the vertical direction is preferably greater than 30‹, the " landing line " being the lowest generatrix of the beam's surface. The pilot is informed of the landing direction and flies into the appropriate beam which, in an example, Fig. 3a, is the beam Sw shown in vertical section. The receiver r, Fig. 4, responds and energizes the indicator w1, through filter w, passing the appropriate modulation frequency and the pilot flies so as to keep the pointer on the central line A, corresponding to the field strength h and hence the " landing line " shown in Fig. 3a. If the pointer rises it moves into the region designated " lower " and vice versa, these being navigating instructions. To determine whether he is at the bottom of the beam i, Fig. 5, or at a position such as j the pilot swings to the right and left, and the needle movements which ensue indicate " more right " or " more left " as the case may be. When the pilot begins to receive. ignals from the transmitter so, indicated by a movement of the needle o1, he shuts off his engine. In a modified indicator, Fig. 4a (not shown), a single needle is used and vibrating reeds responsive to the different modulation frequencies indicate which transmission is being received. The Specification also describes a known guiding system applied to a landing space a .. d, Fig. 1, in which only a single landing direction is defined, in which two transmitters situated at s1 produce overlapping beams S1, S" to define a line e f of equal signal strength. A further transmitter s2, Fig. 2, produces a beam similar to one of the four beams of Fig. 3a and defining a landing line h, and another transmitter s3 producing a polar radiation diagram S3 defines the line b d which is a line of minimum signal strength and indicates the point at which the engine should be switched off.