Patent GB-405656-A (GB)
Title: Improvements in and connected with speed finders and with bombsights for use in aircraft and for other purposes
IPC: F41G3/24
Filed: 1932-07-09
Abstract: 405,656. Speed-indicators. LEVKOVITSCH, P. GOUDIME-, La Maion, Longa, La Napoule, Alpes-Maritimes, France. July 9, 1932, No. 19483. [Class 106 (iii).] Comprises a device for use on aircraft, and for other purposes such as finding the speed of one ship from another &c. for directly determining the ground speed or the relative speeds of the aircraft and another moving object incorporating in a view - finder type of instrument a rotating flat spiral, means for regulating the speed of rotation of the spiral to ensure that an observed object will appear to travel inward along said spiral, and indicating means suitably calibrated associated with the speed of rotation of the spiral. The casing 1 may be turned by handles 8 about its centre 2 and clamped in any position indicated by a scale 4 and pointer 5. Within the casing is rotatably mounted a transparent disc 9 on which is a spiral line 10. A " drift wire " 7 carried by a frame 6 extends fore and aft towards the centre 2. A clockwork motor 12 drives the disc 9, the speed of which is regulated by a governor 15. A cam 22 acting on one arm 20, stressed by a spring 21, of a bell crank lever 18 serves to control the governor and hence the speed of the motor 12. The cam 22 is mounted on a spindle 23 provided with an indicating dial 24 and operating knob 25. The indication gives ground speed corresponding to any given speed of the disc 9. An upright " height bar " 27 carries a sliding sleeve 28 provided with a ring " back sight " 29 over an opening 30 in the cover of the casing. The " back sight " may be fixed in which case the cam 22 is of conical form and may be moved laterally on the spindle 23 in accordance with height by mechanism associated with a knob 32 and dial 33. In addition, the cam may be rotated about the axis 23 by the knob 25 to give ground speed. For use as a ground speed indicator, the instrument is turned about its centre 2 until an observed object on the ground appears to pass down the " drift wire " 7. The " drift angle " can then be read on the scale 4. The back sight 29 is set to the height by the knob 25 and speed regulated until the spiral line coincides with and appears to follow observed objects as they pass. The dial 24 then indicates the true ground speed. When a fixed back sight is used, the altitude is set on dial 33. When used in a bomb sight, a foresight controlling mechanism is used comprising a drum 34 on which is wound a strip 35 attached to an arm 36 carrying at one end a ball 37 movable along the wire 7. The movement of the drum 34 with spindle 23 moves the fore sight along the wire 7. To operate as a bomb sight with fixed back sight, the dial 33 is set to height. Two adjustments may be made, one altering the adjustment of cam 22 without affecting drum 34 while the second rotates the drum. The pilot now steers so that the resultant track is towards the target, while the observer, turns the instrument towards the target, looks through the back sight, and adjusts dial 24 until spiral 10 moves at earth speed. The foresight is automatically set and pilot waits until the target appears in line with both sights. A device for finding the correct course to steer so that the machine moves in direct line of target may be incorporated. If the ground speed is required when us ing a fixed back sight, a second height scale adjacent the first and on the same spindle is adjusted to height of aircraft.