Patent GB-603302-A (GB)
Title: Improvements in aircraft trainers
IPC: F41G3/26
Filed: 1945-07-13
Abstract: 603,302. Ground trainers. WESTERN ELECTRIC CO., Inc. July 13, 1945, No. 18027. Convention date, Feb. 3, 1944. [Class 4] [Also in Groups XXXVIII and XL (c)] in a radar training apparatus simulating, an aircraft in flight, the potentials representative of the position of the aircraft are combined with potentials representative of the position of a target (which may be simulated by a co-operating trainer), the resultant potentials being resolved into potentials representative of the polar co-ordinates of the target with respect to the trainer. The potentials are applied to indicating means to give the appearance of a radar display, elevation and azimuth being displayed on one oscilloscope and slant range on a meter or another oscilloscope. The steering and airspeed motors of the aircraft trainer control the movement of a pantograph which controls-the movement of potentiometer arms to indicate the range and bearing from some particular reference point in the simulated flight of the trainer. In Fig. 2, the position of the arm of potentiometer P1 indicates the range and the position of the arms of potentiometer P2 indicates the bearing. A further potentiometer P3 is controlled by the altimeter unit. In a second trainer, used as the target, potentiometers P4, P5, P6 perform similar functions. Potentiometers P1, P3, P4, P6 are energized by an A.C. supply through the transformer T. The output of PI which is proportional to the range is applied to P2, the resistance of which varies sinusoidally so that the outputs obtained from the two arms are proportional to the X and Y cartesian co-ordinates of the position of the trainer. P5 performs the same function for the second trainer and the output potentials are combined in three summing amplifiers SAx, SAy, SAz, the potentials from P3 and P6 being applied to SAz. The outputs from these amplifiers are proportional to the coordinates of the target with respect to the trainer. The outputs from SAx, SAy are applied to sine-cosine potentiometers P7 and P8, mounted upon the same shaft, the outputs of which are combined in SAα and SArn to form functions proportional to (x cos α - y sin α) and (x sin α+y cos) α respectively, where α is the angle between one of the potentiometer arms and the vertical position on the potentiometer. The output of SAα controls a servomotor Mα which drives the potentiometer shaft until the function (x cos α - y sin α) becomes zero. This is the correct condition for α to equal the bearing angle between the trainer and the target and the function (x sin α+y cos α) then is equal to n, the horizontal range between the two. SArh thus supplies a potential proportional to the horizontal range. This potential is applied to the potentiometer P9 and the output of SAz is applied to the potentiometer P10, the outputs of which are combined in summing amplifiers SAr, SAe so that the servomotor Me is operated to rotate the potentiometer shaft which is common to P9 and P10 until the angle e between one of the potentiometer arms and the vertical position equals the elevation of the target with respect to the trainer and the output of SAe is proportional to the range. This potential is then applied to the meter R1 to measure the range. Alternatively, an oscilloscope may be used. A potentiometer P11 is also driven from the common shaft'to P7 and P8 so that its arm is inclined at α to the vertical. The windings of the potentiometer are attached to a ring gear which is coupled to a pinion driven by the steering motor so that the windings rotate in accordance with the direction in which the trainer is heading in its simulated flight. The windings are energized from a source of direct current. The output potential consequently indicates the bearing of the target with respect to the line of flight of the trainer. The windings of potentiometer P12, which is driven from the common shaft to P9 and P10, are similarly driven by the artificial horizon unit of the trainer so that the output potential indicates the elevation of the target with respect to the line of flight of the trainer. These potentials may then be applied to deflect the spot on the screen of an oscilloscope, but if the rotation of the trainer about its longitudinal axis, i.e. banking or rolling, is to be accounted for the outputs are applied to potentiometers P13, and P14, the arms of which are on a common shaft and are rotated in accordance with the roll of the trainer. The outputs are combined in summing amplifiers SAαc, SAe c, the outputs of which are respectively proportional to the bearing and elevation of the target when the rolling of the trainer is taken into consideration. The bearing and elevation potentials are then applied to the X and Y plates respectively of a cathode-ray tube. Relays 228 and 227 are also energized by the bearing and elevation potentials, the relay contacts being open only when no potential is applied so that the spot is at the centre of the screen and the trainer is flying directly towards its target. Relay 229 is normally energized through the key TR and through the contacts of relays 227 and 228. If, however, the spot is accurately centred on the screen and the key TR, simulating the trigger of a gun, is operated, the relay 229 will release, thereby earthing the arm of P6 and reducing the altitude potential of the target trainer to zero. The spot on the screen consequently falls indicating that a hit has been scored. In a further embodiment disclosed in Figs. -6 and 7 (not shown) two trainers cooperate. The pantograph used in the previous embodiment is not employed; instead the potentials corresponding to the components of air speeds of each trainer are obtained and are integrated by motor-generator combinations to deliver potentials corresponding to the cartisian co-ordinates of each trainer. By apparatus similar to that previously described and which is common to both trainers, potentials corresponding to. the relative polar co-ordinates of the trainers are obtained. Corrections are made by separate mechanism in each trainer for the directions of flight and the roll of the trainers, differential gearing being used instead of the geared potentiometers of the previous embodiment. As in the previous embodiment, the range is shown on a meter and the elevation and bearing on an oscilloscope in each trainer. The deflecting potentials are obtained by rectifying the alternating current output of the final summing amplifiers in place of using batteries as previously. It is also stated that direct current could be used in place of alternating current for driving the systems described. In that case reversing amplifiers would be used in place of the coupling transformers.