Patent GB-634386-A (GB)
Title: Display system for supervision of air traffic and the like
IPC: G01S7/04
Filed: 1947-01-31
Abstract: 634,386. Air-traffic supervision. STANDARD TELEPHONES & CABLES, Ltd. Jan. 31, 1947, No. 3030. Convention date, Feb. 5, 1946. [Class 118 (ii)] An air-traffic or like supervision display system comprising means for optically projecting on a screen a representation of a craft and means for automatically moving this projected representation in accordance with the known course and speed of said craft has a double gimbal arrangement which permits motion both in a straight line and in a circle to be automatically reproduced on the screen. An operator receives flight information by radar, telephone or telegraph and sets controls correspondingly so as to project on a screen an image which moves thereon and which represents the position, direction of flight, altitude and identity of an aircraft. An image of the screen is reflected on to the surface of a halfsilvered mirror through which the radar display is viewed, this superposition of the two displays permitting one to be checked readily against the other. In the centre of the screen 1 is represented the airport 14 and runways 15, the lines 18 representing azimuthal radio guides. The radii 16 indicate degrees of azimuth and the circles 17 indicate distances from the airport, the broken circle 19 representing the stacking lane in which craft circle while waiting to land. An aircraft is represented by an arrow 20, the head showing the direction of flight, the point of intersection of the cross-line with the body showing the position of the aircraft, the colours of head and body indicating the altitude and the accompanying symbols 23 identifying the particular plane. Projector unit. The projector unit (Fig. 3) has a lamp housing 32 which projects the image of an arrow on to a mirror 31 and hence eventually on to the display screen. Switches 34, 35 can be set so that motors 36, 37 rotate discs 38, 39 to a point where an appropriately coloured arrow-head, and body, are in the path of the light-beam. A switch 42 similarly controls a disc bearing identification characters in the character selecting unit 41. The position of the image on the screen is controlled by a double gimbal system 44, 47, 49 and 52 mounted in a fixed frame 43. The final member 52 controls in turn the angle of tilt, about two perpendicular axes 60, 62, of the mirror 31, and thus the projected image may be moved at will over the display screen. The origin controls 70, 72 are used to move the image so as to indicate the present position of an aircraft in the case of a straight flight, or the orbital centre in the case of a circular flight. The azimuth control 70 rotates the first gimbal member 44 via a Selsyn system 71, 46 and the distance control 72 tilts the second gimbal member 47 about its pivots via a second Selsyn system 73, 48 and the image is thus moved to the point on the display screen represented by the polar co-ordinate settings of the azimuth and distance controls 70, 72. For a straight flight the direction in which the flight is to take place is then adjusted by means of a second azimuth control 74 and Selsyn system 75, 51 which rotates the third gimbal member 49. A switch 76 is then moved to the position shown to drive a motor 77 from a power source 80, thus driving a further Selsyn system 78, 53 to tilt the fourth gimbal member 52 and mirror 31 in the required azimuth and hence cause the projected image to move along the required path with a speed determined by the setting of a switch 79. In the case of a circular flight, the origin controls 70 72 are set to move the projected'image to the required orbital centre and a fourth control 81 is set to move the image out on to the circumference of the required circle. The flight azimuth control 74 is then set to rotate the image to the proper position on the circumference, and the switch 76 reversed to drive a motor 82 from the power source 80 and hence rotate the Selsyn system 75, 51 and gimbal member 49 to move the projected image around the circumference at a speed determined by the switch 79. For prediction purposes the drive may be speeded up and then reversed by means of the switches 83, 84 respectively. The direction in which the arrow-image points is determined by a unit 40 driven by a motor 85 under control of the flight azimuth control 74, but in the case of circular flight the latter control determines the radial distance and the arrow must be at right angles to this direction. In its " circular " position switch 76 therefore drives a control device 86 to rotate the unit 40 by a further 90 degrees. The Selsyn systems may be duplicated to give both coarse and fine adjustments. The screen may be transparent and viewed from the rear. Specification 623,188, [Group XL (c)], is referred to.