Patent GB-940293-A (GB)
Title: Improvements in and relating to collision warning systems for aircraft
Inventor: WIERSMA RUDOLF ARNOLD
IPC: G01S13/933
Filed: 1959-11-26
Abstract: 940,293. Anti-collision radio systems. AVEL CORPORATION GENEVA. Nov. 15, 1960 [Nov. 26, 1959], No. 40292/59. Headings H4D and H4L. In a system for computing on a first aircraft the risk of future collision with a second aircraft and in which the first aircraft carries an interrogator and the second a responder including means to transmit height, course and speed, means are provided whereby the computation cannot be carried out unless both aircraft are flying straight and level courses. The computer carried by the first aircraft may be as described in Specification 897,101. The interrogator includes a rotating directional aerial 16 scanning through 360 degrees in azimuth and fixed aerials 18, 19 which between them afford omni-directional coverage; when the first aircraft attitude is changing, gyroscope 24 causes energization of relay 21 the associated contacts of which (1) switch the interrogator from aerial 16 to contact 17, which is oscillated between aerials 18, 19 by counter 20, (2) disconnect azimuthal components resolver 29 from gate generator 27, and (3) switch line 66 from computer 40 to warning lamp 39. Pulses A1 from generator 1 emerge after a fixed delay in unit 2 as pulses B1 and the latter, after a delay t h  proportional to aircraft height in unit 3, emerge as pulses B2; pulses B1, B2 are transmitted on radio frequency f 1 .The second aircraft responds with pulse train C1 . . . C4 on radio frequency f 2 if it determines that the incoming B pulses are from an aircraft at approximately its own height. The B2 pulse from unit 3 produces from generator 27 a range gating pulse D1, the lagging edge of which is adjustable eitheir when aerial 16 is in use, in accordance with the component of the first aircraft's velocity V1 towards the responder, or, when aerial 17 or 18 is in use, in accordance with V1. If the responder decides that the first aircraft is the lower, pulse C2 is made to occur at t 1  after C1, and conversely at t 2  (t 2  > t 1 ); gate 33 is opened t 3  after pulse C1 and closed t 4  after C1 and a further gate is opened t 4  after C1 and closed t 5  after C1, so that pulse C2 is accepted by gate 33 or 35 depending on whether the first aircraft is lower or higher, respectively, than the second one. The ensuing pulse J1 is fed to computer 40, which produces no output unless triggered thereby, via contact 38, and also to fixed-delay device 42 to produce pulse K1 which triggers mono-stable multivibrator 43 to generate gate pulse L1 ; the interval between pulses C2 and C3 is proportional to the eastward component of the velocity V2 of the second aircraft and the duration of pulse L1 corresponds to maximum and minimum possible values of that component. Pulse C3 is fed via gate 44 to the computer and to units 45, 46 to form pulse N1 for gating pulse C4 entry to the computer, the interval between pulses C3 and C4 being proportional to the northward component of velocity V2. The computer receives also mechanical or electrical inputs corresponding to the course of the first aircraft, speed V1 and the relative bearing of the second aircraft as obtained from the angular position of aerial 16. The computer result is extracted only after receiving a C4 pulse, by means of pulse P1. If there is no estimated risk of collision, pulse Q1 on line 61 illuminates sign 61 warning the pilot to maintain existing course and speed. Arrangements are included whereby in the event of estimated risk of collision, lamp 53 or 54 is energized to indicate that he should dive or climb respectively unless the relative aircraft heights are such that collision is unlikely. A corresponding pulse B3 is transmitted to the responder to indicate to the second pilot that he should take action in an opposite sense, Figs. 3 and 4 (neither shown). Specification 940,292 also is referred to.