Patent GB-358742-A (GB)
Title: A device for determining the speed and direction of course of aeroplanes and moving targets
IPC: G01P3/36
Filed: 1930-10-22
Abstract: 358,742. Sighting-apparatus for aircraft. CLEMENTI, A., 8, Waaggasse, Vienna, and AKT.-GES. C. P. GOERZ OPTISCHE ANSTALT, Pressburg, Bratislava, Hungary. Oct. 22, 1930, No. 31730. [Class 97 (ii).] Apparatus for indicating directly the horizontal range (h tan # where h is the height of the aircraft and # the vertical sight angle) and the horizontal angle alpha of a target or aiming point comprises a sighting instrument rotatable about a vertical axis and having a rotatable entrance reflector the rotation (<#>2) of which is transmitted multiplied by two to a cam coupled to a second cam arranged to rotate through an angle log tan #, the horizontal range being indicated by a pointer attached to the second cam and reading against an adjustable logarithmic scale of heights and the horizontal angle alpha being read off directly on a horizontal circular scale. In the form shown, Fig. 4, the telescope housing 2 provided with a circular scale 2a is rotatable about the axis X-X in a bedplate 1. The entrance reflector 4 pivoting on trunnions 3 is geared by toothed sectors 9, 11 to a cam 12 coupled to a cam 15 by thin steel bands 13, 14. The cam 15 carries a knob 17 by which the reflector 4 may be turned and is provided with a pointer 18 running over the logarithmic scale 19a of heights. The latter may be set against the fixed pointer 23 in accordance with the height of the aircraft by rotation of the knob 20. The velocity and angle of the wind relative to the axis of the aircraft may be found by making two observations of a stationary aiming point. The calculating apparatus shown in Fig. 3 may be used. The cursor 30 is clamped to the rule 24 so that the distance AF1 corresponds to the distance flown in wind-free air by the aircraft in the period of time between the two observations. The rule 26 is set at an angle to the rule 24 corresponding to the horizontal angle alpha of the first observation and the cursor 27 is clamped so that the distance F1Z corresponds to the horizontal range. The cursor 33 is then clamped on the rule 29 and the latter set relatively to the rule 26 to represent the horizontal range of the second observation. The rules 32, 34 are then set to pass through the point F2 indicated by the cursor 33. The land speed F1F2, and course angle F2F1A of the aircraft and the speed AF2 and lateral angle F2AF1 of the wind may then be read off. If a moving target is observed instead of a stationary aiming point, the angle F2AF1 indicates the angle made by the target's course with the axis of the aircraft and the distance AF2 indicates the speed of the target. The bedplate 1 and rotatable part 2 of the sighting instrument, Fig. 4, are provided with radial bars 35, 39 connected by a sliding bar 37 perpendicular to the bar 35 and by these means the sighting instrument may be set so that when the aircraft flies at right-angles to the target's course the correct moment for release of a torpedo adapted to strike the target perpendicularly is indicated when the target is sighted in the telescope.