Patent GB-125438-A (GB)
Title: Improvements in and relating to Aerial Observation.
Inventor: POWER RICHARD FITZ
IPC: F41G11/00
Filed: 1916-07-25
Abstract: 125,438. Power, R. F. July 25, 1916. Sights and methods of sighting.-Consists of an observation-of-fire instrument for use on aircraft, having a transparent plate which is maintained horizontal and carries position identification lines, the objects, such as the target and shell bursts, being observed through the plate and from a prescribed height above it; alternatively, the plate is a transparent mirror reflecting into the field of view identification lines carried by another surface which is maintained horizontal. As shown, in Figs. 1 and 2, the observation plate K comprises a transparent disk carried by a frame b mounted pendulously on pivots g from a gimbal ring G. The disk is marked with circles lettered A, B, C, &c., and spaced apart by distances representing to a known scale known distances on the earth. The disk is mounted in a case J having a glass top and bottom, and an eye-piece P is carried by a height bar Q adjustable in a block R pivoted on a fork T which is itself pivoted on the case J at t, the two pivot axes being at right angles. The height bar is adjusted vertically before observation by means of a rack q and pinion turned by a milled disk p so that the, eye-piece P is at a. height above the disk K corresponding to the altitude of the aircraft, &c. A compass L preferably having a floating card 0 is marked with divisions corresponding to the twelve points of a clock face, the 12-6 line being in the true N-S line of the compass. The letters on the disk K are arranged in rows at right angles, and lines N at right angles to one another and corresponding to the rows of letters are marked on the transparent top of the compass box. When observing for artillery, the eye-piece is adjusted about the pivots so that the target is seen through the centre of the disk K, and the position of the shell burst is observed, its distance from the target being read by the circles, and its bearing being read by estimation of the position of a corresponding image on the compass card. The position may then be signalled by the known clock code to the gun station, and the position of the burst may be there determined by means of a celluloid clock code disk on a map. In a modification, the eye-piece after adjustment for height is maintained fixed, and the disk K is housed in a box H which, as shown in plan in Fig. 5, may be slid horizontally by means of chain 15 operated by a pinion 16 along a slide 14. The correction which has to be made in connexion with oblique observations with the apparatus shown in Figs. 1 and 2, owing to the diminution of the height of the eye-piece above the disk K, is thus avoided. The compass is carried by a bracket I on the side of the slide 14. Fig. 10 shows an instrument comprising a view tube t pivoted at v on a pillar l and having an internal transparent mirror forming the " observation surface " which reflects to the eye, with the aid of a mirror at the end of a tube 22, an image of a compass 21. The compass is carried within a ring on a block x pivoted to a collar w sliding on the tube t, the block being capable of sliding on a bar j carried by a sleeve m adjustable vertically on the pillar l by means of a rack and pinion. The compass card is marked with the points of a clock face, and the circles are also marked on the card or on the cover glass of the compass. Before making an observation the sleeve m is adjusted on the pillar l in accordance with the height of the aircraft, &c.