GB708893A - Improvements in or relating to computers of the slide rule type - Google Patents

Abstract

708,893. Calculating-apparatus. BATORI, O. E. Oct. 30, 1950, No. 17601/52. Divided out of 708,811. Class 106 (1) A logarithmic calculator, of similar construction to that described in Specification 708,811 but modified for the solution of triangles, especially the wind triangle in air navigation, comprises co-operating logarithmic scales K and J on a pair of relatively rotatable discs 1 and 2, and inner logarithmic scales of the trigonometric functions of angles on the disc 2 read through an aperture 11 in an upper disc 3 secured to the disc 1. In the calculator shown, there is a double scale O on the disc 2 of logarithmic sine and cosine values which resolve wind into its components, and a logarithmic sine and tangent scale M for drift angle. Both these scales appear in the window 11 and are read at a pointer 17. To calculate the wind correction angle (drift), the cross-wind component is first read off scale K against wind force on scale J after setting wind angle on scale O against the pointer 17. Cooperating linear angle scales P and Q are marked on the discs 2 and 3 for initially finding wind angle from the wind and course directions. By setting air-speed on scale J against this value of cross-wind on scale K, the wind correction angle is shown by pointer 17 on the scale M. To calculate ground speed, the wind angle is set on the cosine scale 0; the tail wind component can then be read off scale K against wind force on scale J, and is added to the air-speed to obtain ground speed. The disc 2 is also provided with a logarithmic latitude scale L for calculating geostrophic cross-wind from pressure gradient ascertained from change in altimeter reading during level flight. The cross-wind is read off scale K against latitude on scale L after setting the flight distance on scale J against the change in altimeter reading on scale K. A logarithmic tangent scale N is also marked on the disc 2, and may be used for finding the direction between two points from their latitude and longitude differences.