GB700592A - Control for beam guidance system - Google Patents

Abstract

700,592. Radio navigation. BENDIX AVIATION CORPORATION. May 28, 1952 [June 26, 1951], No. 13590/52. Class 40 (7) A radio beacon aircraft landing system comprises a ground transmitter providing a radio beam defining a glide path, a receiver on the craft capable of generating craft control signals from the beam signals and means associated therewith for automatically rendering effective the craft control signals when the beam signal strength is above a predetermined minimum. Further means may be also provided ensuring that the control signals are only made effective when their amplitude is below a predetermined maximum. The system ensures that landing control signals are not fed to an automatic pilot or cross-pointer indicator until the craft is correctly placed to make a safe landing. In an embodiment two craft receivers 1 and 3 respectively receive localizer and glide-path beam signals and generate craft control voltages V and also voltages V<SP>1</SP> representative of the magnitudes of received signals. These voltages are displayed on visual indicator 7, 9, 11 and 13. The control voltages V are also fed through amplifiers and isolating circuits to the appropriate input channels of automatic pilot 20. These inputs may be cancelled by shorting them by means of the contacts of relays 21 and 23 which are normally closed but which may be opened by the operation of relays 47 and 51 and 41, 48, 52 and 56 respectively. Relay 47 closes when the localizer control signal falls below a certain value and relay 49 closes when the V' output of the receiver 1 is above a certain value. Thus with adequate localizer strength and an error signal which is not excessive the automatic pilot is fed with localizer signals. The circuit of relay 41 is such that this relay is closed when localizer signals are fed to pilot 20, relay 48 is closed when the glide path control signals are below a certain level, relay 52 is closed when the V<SP>1</SP> output of receiver 3 is above a certain level, and relay 56 is closed by the action of putting the receivers into operation. Thus when localizer control is effective, adequate glide-path signals are received and the craft is not so far off the glide-path that the error signals are excessive, glide-path control circuits are also fed to the automatic pilot. The circuits of relays 51 and 52 include long time constant circuits to prevent the relays releasing due to the temporary fading of signals. Specifications 647,961, [Group XXXIX], and 675,751 are referred to.