Patent GB-804700-A (GB)
Abstract: 804,700. Electric analogue calculating systems. SPERRY RAND CORPORATION. Sept. 23, 1953, No. 26265/53. Class 37. [Also in Group XXI] In an aircraft bombing computor, two methods of bombing may be adopted, either synchronous or inpact. In the former, which is used at high altitudes, the line of sight is set either on the target itself or on a reference point and the craft is flown on an arbitrary course until close to the target when the automatic pilot is switched in and gives the craft the correct heading to allow for wind velocity as determined by a computer. With impact bombing, which is used at low altitudes, the line of sight is fixed and the flight of the craft is controlled to cause the line of sight to pass over the target when the bomb is released manually. In both the synchronous and impact operations, the same computor elements are employed but their interconnections are altered. Craft ground position is determined either by radar or optical means. Solution of bombing problem.-In both modes of operation the same bombing equation is solved by the computors shown in Figs. 35, 37. In the synchronous mode, Fig. 35, components of wind velocity W E , W N  are combined at 720, 730 with the time to impact Ti and then added at differentials 722, 732 to the components X E , X N  of a vector representing the separation of the target from the ground position of target. The outputs of 722 and 732 are supplied to the polar converter 630 to produce the required aircraft heading Ao. The radius vector output from 630 is fed back to the computor input to provide the time to impact Ti. The trial L and true air speed V are set in at 640 and 745. In the impact mode, Fig. 37, the device 630 which now functions as a component resolver and is supplied with the craft heading value A from the compass, supplies a feed-back signal to the computor input corresponding to X E , X N  the components of a vector representing the separation of the computor point of impact from the craft ground position. The signals X E  and X N  are converted at 50 to polar co-ordinates and position the line of sight. Wind determination.-The ground speed is determined by optical or radar means and the wind velocity determined therefrom by observing the deviation of a line of sight from a reference point. As shown, Fig. 30, the signal V representing air speed, is resolved at 701, into rectangular co-ordinates V E , V N  which are applied to differentials 702, 703 where the wind components W E , W N  are added to produce the ground speed components V E , V N . The latter are integrated at variable speed drives 704, 705 the outputs of which are the East and North components X E  and X N  of the craft ground travel and which are used to control the optical or radar sighting device so that the line of sight remains directed on to the chosen reference point. The knobs 461, 451, shown in the Figure, are in the actual computor replaced by tracking motors controlled by a universally pivoted rod. The motion of the rod moves the marker intersection on the plan position indicator to correspond with the reference point through the polar converter 50. If the rod remains still after the initial setting, then the line of sight remains on the chosen reference point if the wind component signals are correct. To find the correct wind component the angle of sight is set twice by the rod, the two settings being separated by a time interval T. The change in the line of sight settings are transmitted through the variable ratio drives 706, 1 707 which have a ratio of -. Instead of T making two separate adjustments the operator may keep the line of sight continuously on the point of reference during the interval T. Stabilization unit.-As shown in Fig. 44, the stable element is supported in a gimbal system which permits three degrees of freedom at bearings D 1'  D 2 ; E 1'  E 2  and F 1 , F 2  with respect to the stable element axes. The stable element, Fig. 54, contains, first a set of three gyroscopes G 1 , G 2 , G 3  which tend to maintain it in a fixed orientation and secondly, two levels which indicate the direction of the dynamic vertical. The signals developed by the levels are applied to two gyroscopes to maintain the axis F 1 , F 2  in coincidence with the dynamic vertical. The third gyroscope is precessed by a signal which is the difference between the heading values obtained from the stable element and a flux valve mounted in the aircraft wing. Precession of gyroscopes G 1 , G 2 , G 3  is effected by electrical internal torque motors at the bearings of the pivot axes of the gyroscopes. To maintain the dynamic vertical of the system coincident with the true vertical when the craft is stationary, the level of the unit is determined by liquid detectors (not shown) which energize the internal torque motors. To allow for the earth's rotation, the signal output of the level detector is integrated and added to the signal itself before application to the torque motor. Signals, to correct for the craft velocity, are injected into the internal torque motors and consist of values corresponding to air speed and the craft heading as derived by the stabilization unit. With optical sighting means, e.g. a periscope, the latter is stabilized by electrical signals from the stabilization unit. With a radar sighting means, the antenna is not stabilized and the correcting signals are used to position the deflecting coils of the plan position indicator and the antenna reflector, to stabilize the image of the sighting point against aircraft altitude movements. Navigation.-In the navigation of the craft towards the target, account is taken of the earth's curvature and latitude and longitude counters give the craft position during flight after initial setting at a known reference position. In this connection the earth is assumed to be spherical and a ball carriage variable speed drive is driven from the latitude counter-shaft to produce the cosine factor in the longitude reading. Specification 631,517, [Group XXI], is referred to.