Patent GB-648743-A (GB)
Title: Improvements relating to apparatus for aviation training
IPC: G09B9/40
Filed: 1946-01-23
Abstract: 648,743. Trainers for radio navigation. LINK AVIATION DEVICES, Inc. Jan. 23, 1946, No. 2304. Convention date, Feb. 17, 1945. [Class 40 (vii)] A trainer for simulating the navigation of a radar-carrying aircraft relative to a target aircraft, comprises a cathode-ray tube, means for producing a spot on the screen of the tube corresponding to the simulated target and means for varying the position of the spot in accordance with assumed changes in the azimuth and altitude angle of the target and in accordance with banking and pitching movements of the trainer. The invention which is similar to that described in Specification 629,945 is applied to a Link trainer as described in Specifications 370,128 and 481,375, [both in Group XXXIII]. The apparatus includes a fighter recorder and a target recorder which move over a table in accordance with the operations of the trainee within the trainer and the operations of an instructor respectively. These recorders are interconnected mechanically and the range and azimuth information derived thereby is compounded with simulated altitude-difference information to derive signals corresponding to the bearing and elevation of the target relative to the axes of the fighter. The target recorder.-The target recorder is controlled by the instructor by means of a control unit attached to the table over which the recorders move. The control unit comprises a number of variable auto-transformers the outputs from which drive motors in the recorder controlling its speed and rate of turn. On account of the nature of the gearing used the speed of the recorder is altered when making a turn and to compensate for this an additional drive depending on the rate of turn is combined with the drive dependent upon speed by means of a differential gear. Two lamps attached to the recorder shine on to the table forming a spot of light indicating the instanteous position of the recorder. The fighter recorder.-The Link trainer may be made to turn under the control of the pupil. This turning motion is transmitted through a Selsyn system, at the output of which is provided a servo follow-up system to the fighter recorder to control its direction of motion. The speed of the fighter simulated by the trainer is also under the control of the pupil. The various factors controlling the speed of the fighter, viz. throttle setting and angle of climb, are combined and are transmitted as a rotation by a Selsyn and follow-up system to a unit where they are used to control the setting. of a potentiometer. The rotations transmitted by the Selsyn system are not directly proportional to the speed and the potentiometer is set through the intermediary of a cam system so that the voltage output is proportional to speed. This voltage is applied to the grid of a gas-filled relay, the anode circuit of which is in series with the armature of a driving motor in the fighter recorder, the speed of which is consequently proportional to the potentiometer setting. As in the target recorder, a differential gear is used to compensate for variations in speed introduced during turning. An inking wheel on the recorder traces the simulated flight path of the fighter on the table. Target relative bearing.-The fighter and target recorders are joined by a sliding rod which is pivoted about a point in the target recorder directly above the spot of light. The fighter and target recorders always remain parallel to their original positions on the table and so the rotation of the sliding rod measures the compass bearing of the target relative to the fighter. This rotation is transmitted by a Selsyn system and a follow-up servomotor to an input shaft of a differential gear housed in the trainer. The trainer itself is coupled to the other input of the differential so that the relative compass bearing is combined with the heading of the trainer to give the bearing of the target relative to the fighter. The output of the differential gear causes a ring 369 which normally lies horizontally to rotate about its vertical axis. The angular position of a predetermined axis L-L<SP>1</SP> in the plane of the ring relative to the forward direction of the trainer is equal to the target relative bearing. Pitching and banking.-The pitching and banking movements of the trainer relative to its fixed base are transmitted by mechanical coupling, including push-rods 362, 363, to the above-mentioned ring which is displaced from its horizontal position in accordance with these movements. The ring is accordingly positioned relative to the forward axis of the trainer as the simulated fighter is positioned relative to the horizontal projection of the line of sight from the target. Altitude angle and range (mechanical triangulation).-A sling attached to the fighter recorder passes along the sliding rod joining the two recorders, its far end being attached to a spring-loaded pulley in the target recorder. The pulley rotates to an extent depending upon the target ground range and, operating through a follow-up system, causes the rotation of a pair of screws upon which is mounted a member which moves along the screws in accordance with the ground range. To obtain the altitude angle and slant range the altitude differential must also be obtained. The operations of the pupil cause the pressure in a bellows to be varied in inverse proportion to the assumed altitude of the fighter. This collapsing or expanding motion of the bellows is transmitted through a Selsyn and follow-up system to one input of a differential gear into the other input of which the assumed altitude of the target is inserted by the instructor from his control unit. A potentiometer in the control unit is set according to the desired rate of ascent or descent, a switch is positioned according to whether ascent or descent is desired and a timing circuit is adjusted to cause the operation to continue for the desired length of time. Then, on pressing a button a motor connected to the other input of the differential gear is driven for the desired length of time, at the desired rate and in the desired direction. The output of the differential which is a measure of the difference in altitudes between the fighter and target is transmitted by a Selsyn and followup system to the target recorder where it causes the member slidably mounted within the above mentioned member mounted on the pair of screws to be positioned transversely in accordance with the altitude difference. The second member moves in a direction perpendicular to that of the first so that it is positioned with respect to a predetermined fixed point in accordance with altitude angle and slant range. A sliding rod is attached to the second member and pivoted about the fixed point, the rotation of the rod measuring the altitude angle. The slant range is measured by means of a string attached to the second member and passing along the sliding rod. The string is tied round a pulley the rotation of which is transmitted by a Selsyn system to an instrument in the instructor's panel. Azimuth and elevation.-The rotation of the sliding rod about its pivot is transmitted by a Selsyn and follow-up system to rotate the gimbal 389 about the axis Z-Z. The line F-Ta is accordingly positioned relative to the plane of the ring 369 and its axis L-L<SP>1</SP> as is the line of sight from the fighter to the trainer relative to the plane of the fighter and its longitudinal axis. In the general condition, when axes P-P and Z-Z are not coincident the movement of gimbal 389 causes rotation of the plate 380 (shown partly broken away) relative to the ring 369, the plate being mounted on the ring by means of the ballrace 375. This rotation is transmitted by shaft 398 to rotate the input shaft of a Selsyn motor, the housing of which is rotated in accordance with the target relative bearing. The differential combination measures the azimuth angle of the target from the fighter about the axes of the latter and is applied to an indicator on the instructor's instrument panel. The rotation of the gimbal 385 about the axis P-P relative to the plate 380, is a measure of the elevation angle and is caused to actuate the Selsyn motor 378 by means of the gear segment 393 attached to the gimbal 385 and the sprocket 395. The elevation angle is indicated on the instructor's instrument panel. Radar display.-The outputs of the Selsyn systems which give the meter readings on the instructor's instrument panel also drive potentiometers so that voltage proportional to range, azimuth and elevation are obtained. These are applied to echo-simulating equipment the output of which is fed to the intermediatefrequency stages of standard radar receivers, one of which is housed within the trainer for the use of the pupil while the other is positioned where it may be seen by the instructor. The azimuth and elevation of the target are displayed on C-scopes and the range on a cathoderay tube in the case of the instructor's receiver ; the reading obtained on the cathode-ray tube is used by the instructor to control a meter on the pupil's receiver. Slip-stream simulation.-When the ground range is less than one mile, the altitude differential less than fifty feet and the heading of the target coincides with the target compass bearing the trainer is caused to pitch and bank in an irregular manner by means similar to the " rough air " mechanism described in Specification 481,375. Specifications 603,302 and 629,945 also are referred to.