Patent GB-745100-A (GB)
Title: Improvements in or relating to navigation aid apparatus for aircraft
IPC: G05D1/02
Filed: 1953-09-25
Abstract: 745,100. Radio navigation. SPERRY CORPORATION. Sept. 25, 1953 [Sept. 29, 1952], No. 26463/53. Class 40 (7). In order to indicate the course to be steered by an aircraft to approach and maintain it on a radio beam, an electrical signal dependent on the heading of the craft is developed in windings 6 associated with a magnetically-shaped gyroscopic compass (not shown). This signal is applied to the stator of a Selsyn 7 the rotor of which is automatically driven into a position corresponding to the heading by a motor 9 which also operates a repeater compass pointer 5 through a differential gear 10. Repeater compass card 4 may be set by a knob 12 relative to a lubber line 11 so as to correspond with the direction of the radio beam. Pointer 5 then moves with card 4 to main a true indication of heading by virtue of a coupling between card 4 and the other input to differential gear 10. Movement of card 4 is also transmitted to the rotor of a differential Selsyn 13 the stator of which is supplied from the compass signal in windings 6 so that a signal dependent on the difference between aircraft heading and beam direction is applied to the stator of a Selsyn 14 the rotor of which produces an electrical signal representative of the correction to heading necessary to fly along the beam. This signal is applied to an amplifier 31 controlling a follow-up motor 32 driving the rotor of a Selsyn 33 to produce a corresponding signal which through an amplifier 39 energizes an electromagnet operating a pointer 3 to indicate the necessary azimuth correction. In order to produce an asymptotic approach to the radio beam it is necessary to fly the aircraft at a heading differing from the beam heading by an amount proportional to the lateral displacement of the craft from the beam. A localizer radio receiver therefore produces a signal dependent on this lateral displacement, which is applied to an amplifier 22 controlling a follow-up motor 23 driving the rotor of a Selsyn 14 so as to reduce the deflection of pointer 3 to an extent which is greater the greater the lateral displacement of the aircraft from the beam. At lateral displacements from the beam greater than a predetermined value the craft is arranged to fly at a fixed heading relative to the beam by virtue of mechanical limit stops 27, 28 and a slipping clutch 25 which limit the maximum displacement of the rotor of Selsyn 14. Similar limit stops 35, 36 are associated with motor 32 to limit the movement of the rotor of Selsyn 33. To modify the necessary correction indicated by pointer 3 in accordance with banking of the craft the stator of the Selsyn 33 is supplied from a Selsyn pick-off 29 associated with the bank axis of a gyro-vertical 30. A pointer 2 operated by an electromagnet 51 indicates the course to be steered to approach and maintain the aircraft on a radio glide path. During approach, electromagnet 51 is energized in accordance with signals, combined in an amplifier 48, from the pitch pick-off 49 of gyrovertical 30 and an altitude detector 41. When on the glide path manual operation of a switch 47 substitutes signals from a glide path receiver 44 for those of the altitude detector. In modifications : (a) an electrical signal representing the difference between heading and beam direction and an electrical signal representing displacement from the beam are combined in an amplifier controlling motor 32; (b) an electrical signal corresponding to that applied to amplifier 31 and an electrical signal from the bank pick-off of the gyro-vertical are combined in an amplifier controlling pointer 3; (c) the signal from the pitch pick-off of the gyro-vertical is modified in dependence on signals from the glide path receiver or the altitude detector. Specifications 660,559, [Group XXV], and 690,985 are referred to.