Patent GB-574050-A (GB)
Abstract: 574,050. Teaching aircraft recognition. JOHNSON, L. G., and ROSE, A. G. Sept. 18, 1941, No. 11969. [Class 146 (ii)] [Also in Group XXI] Apparatus for training personnel in aircraft recognition, comprises a screen, means for projecting a beam of light on to the screen, one or more models of aircraft disposed in the beam of light so that images are formed on the screen, and means to cause relative movement between the models and the screen and/or the light-projecting means so as to vary the position and/or the size of said images on the screen. A dummy rifle in duplicate is also provided and arranged to throw the image or shadow of a ring-and-bead graticule on to the screen and also of a bullet-strike circle, at the instant of firing, to a position ahead of the target to allow for the rate of travel of the target. The screen 76 is translucent and is disposed between a projector device 56 and a dummy gun 77 and scale models of aircraft 11 are adapted to be fixed by a universal support 13 on a stand 12 intermediate of the projector and the screen, so that images of the models are thrown upon the screen. The upright 12 is carried by a carriage 14 adapted to be reciprocated on slides 17 disposed at right angles to the screen by means of a chain 21 driven by a sprocket wheel 22 which in turn is driven through a slipping-clutch device 26 on a shaft 27 driven through gearing from a motor 29 under the control of a rheostat 30, and a reversing switch 25. Coupled with the motor is a generator 31, the voltage of which is registered on a voltmeter 32 to correspond with the speed of approach or recession of the model with respect to the screen. A pointer 34, driven from the shaft 27, is adapted to coact with a graduated disc 38 to indicate the position of the carriage with regard to the screen at any time and so indirectly to represent the range of the image from the observer, this range decreasing as the model moves in a direction away from the screen and towards the light source. Driven synchronously from the pointer is a scale device 48 with which coacts a light 49 and lens 52, so that the correct range of the image on the screen may be projected thereon, the light 49 and the motor controls being connected to the trigger of the gun, so that pressure on the trigger causes the motor 29 to be switched off and the light 49 to be switched on. An upright extension 53 of the carriage guides carries a projector frame 54 and projector 56 disposed in a line with the model 11, and the intensity of the lamp is controlled by a resistance 60. An apertured shutter 59 is mounted in front of the lamp and a rotary colour plate 88 may be disposed in front of the shutter so that the colour effects on the screen may be varied. The lamp housing also carries a motor 61 adapted to rotate a frame 62, 63 which carries models 66 at the ends of bars 64 depending from the frame members 63 on which they are rotatively and axially adjustable, a coupled generator 68 and a voltmeter 69 indicating the speed of the rotation, which is controlled by a rheostat 67. A transparent moving cloud-effect screen 84 is suspended by flexible connectors from the frame so that it can be raised above the frame when not in use, and a fixed screen 86 in a support 87 is used to give static cloud effects when required. On the opposite side of the screen is arranged a pair of training guns 77 working simultaneously ; on one of the guns is arranged a projector 78 fitted with a ring 8 and bead graticule, the image of which is to be projected on the screen, while the other gun is fitted with a rotatably adjusted projector 79 which gives a circle of light to represent a bullet group and is lighted by a switch connected with the gun trigger. For practice in aircraft recognition the frame 63 remains inoperative, the screen 84 and the rods 64 are raised and the model 11 is attached to the stand 12. The universal joint 13 allows the model to be turned in any direction and for the purpose of comparison between different types of aircraft, a supplementary stand 91 supporting further models is placed on the guides 17 between the projector 56 and the screen, so that the images of the different models are projected side by side on the screen 76. For range-estimation practice, the ring bead and sight projector on the screen by the projector 78 is harmonised with a gun-sight 92 so that the gunner has the impression of looking through a normal sight and the model on the carriage is moved towards and away from the screen, the speed of movement being registered by the voltmeter 32. When the correct portion of the sight is filled with the image for the assumed range, the gunner fires, presses the trigger and the bullet circle is projected on to the screen, the traverse of the model is stopped, and the correct range is projected on to the screen by the projector 49. Representations of tracer bullets may replace the ring-and-bead graticule in the projector 78 for tracer-bullet practice and in this case the movable cloudeffect apparatus 84 is operated. For relative speed estimation practice, the pillar 12 is removed and the rods 64 are brought to the position to bring the models 66 into line with the projector, and the frame 63 is rotated to take the models in succession across the ring graticule on the screen. The speed of the target is estimated by the time taken for the image to pass across the ring-sight and the gun is trained by the gunner and the trigger pressed, whereupon a bullet circle is projected by the projector 79 which has been previously set by the instructor to the correct allowance for the speed and range and should, if the estimate is correct, be superimposed on the moving image. The use of a number of models 66 shortens the waiting period between the practices. Alternatively, instead of the targets moving across the light beam, the carriage and its supports may be arranged to pivot about an axis remote from the screen and the framework 63 may be dispensed with. According to the Provisional Specification, the gun-sight for projection is mounted on the carriage 14 and another carriage, arranged to traverse at right-angles to the former, supports the target, so that the size of the projected gun-sight and the speed of the model may both be varied.