Patent GB-867029-A (GB)
Title: Navigational system
Inventor: PERKINS EARL STUART
IPC: G01S1/02
Filed: 1959-07-07
Abstract: 867,029. Radio navigation. BUTLER CO. July 7, 1959, No. 23270/59. Class 40(7) [Also in Groups XXXIII and XXXVI] Relates to a craft navigational instrument for indicating on the craft the position of the craft 12, Fig. 2, with reference to a selectable waypoint 41 in which D.C. voltages proportional to the cartesian co-ordinates of the craft and the waypoint relative to a radio beacon 11 are produced from corresponding input polar coordinate signals by two pairs of sine and cosine potentiometers 21, 20 and 89, 90 and combined to give two voltages proportional to the cartesian co-ordinates of the craft relative to the waypoint which are applied to galvanometer movements 39, 38 to produce horizontal and vertical deflections of vertical and horizontal crossed pointers 35, 34 so that the positions of the aircraft and waypoint are indicated respectively by the intersection of the pointers 35, 34 and a central reference point 40 on the instrument face 33 as shown in Fig. 3. As shown a voltage proportional to the distance of the craft from the radio beacon is applied across the sine and cosine potentiometers 20, 21 from a potentiometer 15 controlled by the distance output from a D.M.E. receiver and the wipers of the sine and cosine potentiometers 20, 21 are controlled by the bearing output of the beacon receiver. A voltage proportional to the distance of the waypoint from the beacon is applied across the sine and cosine potentiometers 89, 90 from a manually controlled potentiometer 79 and the wipers of the sine and cosine potentiometers 89, 90 are set manually by a knob 97 in accordance with the bearing of the waypoint from the beacon. According to the present invention the windings of the sine and cosine potentiometers 21, 20, 89, 90 are conjointly rotatable by means of a knob 110 which also controls a rotatable bearing scale 106 surrounding the instrument face 33 so that when the knob 110 is adjusted to make the vertical pointer 35 coincide with the reference point 40 as shown in Fig. 4 the resultant vertical displacement of the horizontal pointer 34 from the reference point 40 indicates the radial distance of the craft from the waypoint and the reading on the scale 106 given by the pointer 35 indicates the bearing of the waypoint from the craft. The instrument face 33 is rotatable about the reference point 40 by means of a differential synchro 104 controlled by the compass and by the knob 110 so that the magnetic heading of the craft is indicated on the scale 106 by an index arrow 105 on the face 33. When the craft is directed towards the waypoint the index arrow 105 will coincide with the pointer 35 as shown in Fig. 4. Horizontal and vertical distance scales are marked on the face 33. The deflection sensitivity of the instrument is controlled by applying the outputs from the sine and cosine potentiometers 21, 20, 89, 90 through ganged semi-circular potentiometers 60 ... 67 controlled by a knob 45. A stop 129 prevents deflection of the horizontal pointer 34 beyond the edge of the instrument face. The voltage between the wipers 26 and 26<SP>1</SP> of the cosine potentiometer 20 is applied to a meter 130 to provide an additional indication of the distance of the craft from the waypoint and this voltage is also (1) differentiated by a capacitor 135 to indicate velocity on a meter 136 and (2) applied to operate a relay 139 as the craft passes the waypoint.