Patent GB-629945-A (GB)
Title: Improvements relating to apparatus for the instruction of navigation by radar
IPC: G09B9/54
Filed: 1945-03-14
Abstract: 629,945. Electric control systems. LINK, E. A. March 14, 1945, No. 6449. Convention date, March 20, 1944. [Class 40 (i)] [Also in Group XL (c)] A link trainer such as is described in Specifications 370,128 and 481,375, [both in Group XXXIII], simulates a radar equipped fighter, while a target under the control of an instructor gives rise to an indication on the display unit, comprising a C-scan and range meter, within the trainer. A recorder (or " crab ") moves over a table in accordance with the operations of the student within the trainer and a second recorder simulating the target moves under the control of the instructor. Factors representing the separation between the recorders and the simulated difference of altitude between the aircraft are fed to mechanical triangulation means from which the slant range and elevation of the target from the fighter are obtained. The azimuth of the target is determined from the heading of the trainer and the relative positions of the recorders upon the table. These quantities are then applied to a modified radar receiver which displays the simulated position of the target. Fighter recorder.-The rotation of the trainer is applied to the input of a selsyn system, the rotation being transmitted electrically to the output of the system where it rotates the propelling wheels of the fighter recorder (described in Specification 484,243, [Group XXXIII]), about a vertical axis, so that any change in the simulated direction of motion of the trainer causes the direction of motion of the recorder to change correspondingly. To vary the speed of the recorder, the throttle of the trainer is mechanically linked to a selsyn system, the output of which, acting through a follow-up system causes a drum to move longitudinally. The drum bears an elevated portion, the extent of which varies along its length. The drum rotates continuously and co-operates with a stationary cam follower so that the driving motors of the recorder are actuated when the cam is upon the raised portion of the drum. The proportion of the time for which this occurs varies according to the longitudinal position of the cam relative to the drum and' thus the operation of the throttle varies the speed at which the target recorder moves. The controls for causing driving or climbing also operate differentially with the throttle so that the speed increases on diving and decreases on climbing. Target recorder.-The target recorder is similar in operation to the fighter recorder but it is under the control of the instructor. Rotation of a handle by the instructor rotates the propelling wheels to alter the direction of travel of the target. A second handle moves a drum longitudinally for varying the speed, as described for the fighter recorder. Determination of azimuth.-A rod which is pivotally mounted upon the target recorder slides within bearings on the fighter recorder. Relative movement of the two recorders causes the rotation of the rod about its pivot, which is transmitted by a selsyn system to a differential gear which is driven through a follow-up system. The rotation of the trainer about its axis also drives the differential gear so that the output of the gear is proportional to the azimuth angle of the target with respect to the trainer. This output is transmitted by a further selsyn system to position the wiper arm of a potentiometer, the output from which is used to give the required azimuth indication on the C-scan display within the trainer. Determination of altitude angle and slant range.-A string is attached to the rod joining the recorders, its other end passing over a pulley at the input of a selsyn system. The length of the string varies with the separation between the recorders, and thus the selsyn output which, acting through a follow-up system, determines the position of a rod 364 mounted transversely upon a toothed shaft 365, is a measure of the horizontal range. A bellows, as described in Specification 481,375, responds to simulated changes of altitude of the trainer and is coupled mechanically to a selsyn system. The instructor controls the target altitude by the movement of a handle which causes the rotation of the housing of the receiver of the altitude selsyn system, so that the absolute rotation of the output shaft is a measure of the difference in altitudes between the trainer and target. The output shaft rotates the toothed shaft 365 to cause a rack 370 mounted upon the transversely placed rod to move at right-angles to the length measuring horizontal range. The position of the rack is a measure of the altitude difference and thus a mechanical triangle is obtained, the hypotenuse measuring the slant range, and the angle opposite the side, representing the altitude difference, measuring the altitude angle. A sliding rod 376 is pivoted at one end so that the length of a string 386 running along it measures the slant range and the angle through which it turns measures the altitude angle. These quantities operate upon their respective selsyn systems, the output of which determine potentiometer settings as for the azimuth measurement. The potentiometer outputs are then employed to give the required indications upon the radar display unit within the trainer. Conversion of altitude angle to elevation angle.- The elevation angle of the target varies with the altitude of the trainer and becomes equal to the altitude angle when the plane of the trainer is horizontal. To correct for the difference between the altitude and elevation angles, a pair of gimbals is provided, Fig. 5 (not shown) banking and climbing or diving controlling the inner and the outer gimbals respectively. A roller is positioned on the inner gimbal, its positions round the gimbal being determined by the azimuth angle. When the trainer changes its altitude, the gimbals move carrying the roller with them, the magnitude of the movement of the roller being proportional to the correction to be applied to the altitude angle. This movement is applied to a selsyn which, operating through a follow-up system, rotates the housing of the elevation angle selsyn receiver, so that the absolute rotation of its output shaft measures the required angle. Specification 603,302 also is referred to.