Patent GB-1313260-A (GB)
Title: Display apparatus for use as aircraft gunsights
IPC: F41G9/00
Filed: 1971-09-01
Abstract: 1313260 Teaching warfare HONEYWELL Inc 1 Sept 1971 [4 Sept 1970] 40715/71 Heading F3C [Also in Division H4] In a real or simulated aircraft a cathode-ray tube display is produced showing the locus of the present positions which a stream of hypothetical projectiles previously fired from the aircraft would have as viewed from the aircraft. Thus, referring to Fig. 3, an aircraft, the present position of which is 0 and is assumed to have followed, in the previous two seconds, a course determined by the line 20<SP>1</SP>, 10<SP>1</SP>, 0, is further assumed to fire projectiles at 0À1 second intervals so that the projectile fired 0À1 seconds ago would be at position 1, that fired 0À2 seconds ago at position 2 &c. with that fired 2 seconds ago at position 20. (In the Figure, curve 60 is the actual trajectory of projectile 10, line 62 the locus of the present positions of the projectiles 1-20 and curve 61 the actual trajectory of projectile 20). Based on the above assumptions electronics computing apparatus is employed to compute, for each (hypothetical) projectile; a first threedimensioned vector quantity representative of the distance between the position of the aircraft when the projectile was fired and the present position of the aircraft, e.g. #α20=the distance between positions 20<SP>1</SP> and 0 for projectile 20; a second three-dimensioned vector quantity representative of the distance between the position of the aircraft when the projectile was fired and the present position of the projectile, e.g. #b20= the distance between positions 20<SP>1</SP> and 20 for projectile 20; a third three-dimensioned vector quantity, computed from each first and second vector quantity, and representative of the distance between the present position of the aircraft and the present position of the projectile, e.g. #Á20=the distance between 0 and 20 for projectile 20; the apparatus further computing the co-ordinates of the head of each third vector quantity in a Cartesian system having a plane normal to the direction in which the proj ec biles are fired from the aircraft and controlling the cathode-ray tube to display, in the Cartesian system, the locus of the positions of the heads of the third (three-dimensional) vector quantities. Fig. 2, shows the general form of the display which includes, in addition to the stream of projectiles 2 to 20 (even numbers only shown), a bore-sight cross 37, range bars 40, 41 and 42 together with a radar "pip" (range mark) 43. The bore-sight cross, the range bars and the radar pip displays are produced according to the general scheme shown in Fig. 1 which includes the projectile stream computer 24 controlling the display of projectile stream. This computer which is described with reference to a functional diagram (Fig. 4, not shown) utilizes data concerning air speed, angle of an attack, sideslip angle, air density, air temperature (the latter two parameters to enable the drag on the projectiles to be computed for an assumed mass and surface area) together with the translation and rotation of the aircraft in inertial space an initial muzzle velocity for the projectiles and initial values for the first and second three dimensional vectors, i.e. the α and b vectors of Fig. 3. The apparatus then computes a recurring succession of vectors #α1 to #α20 and #b1 to #b20 from which a corresponding succession of #r vectors is computed and converted into X and Y beam deflection signals for the display tube. Fig. 6, shows the sequence of beam deflec - tion and on-off conditions which are required to produce the display which is presented to the pilot as a head-up display.