Patent GB-217622-A (GB)
Title: Improvements in and relating to methods of and mechanism for guiding aircraft
IPC: G01S1/02
Filed: 1923-02-14
Abstract: 217,622. Soc. Industrielle des Procedes W. A. Loth, and Loth, W. A. Feb. 14, 1923. Leader gear arrangements; infra red rays, telegraphy by; receiving systems and apparatus; thermionic detectors.-In apparatus for guiding aircraft to illuminated landing-grounds electromagnetically defined by means, of insulated guide cables energized at different frequencies and intensities which transmit audio-frequency signals to apparatus on the aircraft, a number of branch circuits radiating from a centre are arranged on the landing ground and means are provided for manually or automatically connecting that branch only in circuit which is at the time parallel or most nearly parallel to the direction of the ground wind in order that the aircraft may alight head to wind. Fig. 1 shows a leader cable 2 leading to and around an aerodrome, the current being passed also by a switch 3, operated by hand or by a wind vane, through any of a series of shunt radiating cables 4 sunk in the ground. A cable 1 transmits the characteristic signal of the station or the cable 2 may be used for this purpose if the propagation of the signal outside the looped part of the cable is prevented. The cables defining each landing ground may not only transmit their characteristic indication or frequency but may be used for transmitting telephone messages at audio or high frequency and simultaneously telegraphic messages may be transmitted to other aircraft by utilizing inaudible frequencies. For detecting the position of the cables the aircraft may carry two vertical windings at right angles to one another and arranged in the longitudinal and transverse planes of the aircraft or at 45‹ to the longitudinal plane, in combination with two horizontal windings on the wings or with a single horizontal winding. By connecting the windings in various ways the position and angle of approach of the machine relative to the cables may be determined. Fig. 6 shows a landing ground having a convex surface and provided with a central projector 33, a ring of lamps 35 and concentric cables 1<a>, 1<b>, 1<c>, 39 carrying alternating currents of different frequencies. A winding on a gimbal frame in the aircraft enables the passage of the aircraft over the successive cables to be detected. Where a flat aerodrome is employed coaxial loops may be supported one, above another on a pole, the loops carrying currents of different frequencies to enable the height of the aircraft to be determined. Or a trailing wire from the aircraft by forming an earth connection to a circuit on the aircraft may in addition indicate the proximity mechanically. Alternatively loops of insulated cable with a condenser in circuit may be laid along each landing track and by acting inductively on a circuit carrying an alternating current on the aircraft produce a signal as the ground is approached. Sources of infra red radiations influencing detectors cn the aircraft may be arranged along the tracks for this purpose. Sources of infra red radiations may be arranged at the centre of each landing ground and at intervals along the guide cables. Fig. 5 shows means acting in conjunction with the cable detector windings for picking up infra red radiations. A thermopile 14 at the focus of a mirror 15 is in circuit with the primary winding 18 of a transformer the secondary winding 24 of which is in circuit with a detector 26 and receiver 27<1>. The thermopile circuit also contains a potentiometer 19 for eliminating undesirable currents. The circuit also has an interrupter 17, and a loop 16 is designed to neutralize the inductive effect of the interrupter coil on the circuit. The circuit containing the detector 26 also contains a secondary winding 25 coupled to a primary winding 23 in circuit with the cable detector windings. The interrupter 17 is of audio frequency different from that of the circuit containing the winding 23. If high frequency transmision is being received from the cables, the thermopile circuit may be tuned to the same frequency by means of a condenser 26<1> and variable inductance 27.