GB565953A - Improvements in navigational and like instruments - Google Patents

Abstract

565,953. Plotting instruments. HURST, R. A. May 28, 1943, No. 8533. [Class 97 (iii)] Relates to an instrument for plotting course, speed, or for navigational purposes and comprises a transparent rectangular plate PR, a rotatable transparent circular wind plate WP and parallel arms PA, whereby the instrument is mounted on a drawing board and may be moved about while maintaining its parallelism. The plate PR is provided with centre lines graduated in arbitrary units denoting time speed scales as and, as shown, are marked in speeds 180 to 500 miles per hour and also 90 to 250 miles per hour. Converging lines cl<1>, cl<11> are drawn to a slope such that the ordinate between them at any particular speed represents the distance travelled in one minute at that speed. The wind plate WP has at its edge compass markings graduated in steps of 5 degrees and is provided on its upper surface with six circles numbered 20 ... 120 in multiples of 20, denoting wind speed in miles per hour. On the underside of the wind plate with the circle 120 as base, an Appleyard scale AS<1> is marked such that the division marked' 60 coincides with the 330 degrees mark on the compass and serves as a datum line. On the upper side with the circle 20 as base, a righthand scale rhh<1> is marked representing heights in thousands of feet. On the same circle as base, a left-hand temperature scale lht<1> is marked, representing air temperature. Arcuate bands AB are marked on the plate PR, as shown, and are provided with arrow heads and marked for magnetic variation and also for east and west. On the plate PR below the wind plate WP are marked corresponding Appleyard, temperature and height scales on opposite sides of the circles from those on the wind plate WP. Near each edge of the plate PR a number of turn circles tc are described, the diameters of which are related to the rates of turn and to the speeds in miles per hour of craft turning at those speeds. The circles are marked appropriately port and starboard. The instrument is carried by parallel arms PA from a slide sli mounted on a guide g on the drawing board. A method of use is described in the Specification.