GB691351A - Improved air navigational device for measurement of track error and computation of ground speed - Google Patents

Abstract

691,351. Measuring angles. JONES, A. E., and HAYES, N. Nov. 7, 1950 [July 18, 1949]. No. 18883/49. Class 97 (iii). [Also in Group XIX] An air navigational device adapted, when placed over a chart, to indicate track error and ground speed comprises a transparent plate a marked with an angle scale i and provided with a co-operating index arm d pivoted on the zero line b. Also marked on the plate are a distance scale c and a set of longitudinal ground speed lines intersected by time interval lines l. A cursor m is provided for reading these scales. The plate a is placed on the chart with the line b over the course to be made good and the arm d adjusted over a point observed on the ground. The track error can then be read off the scale i. By placing the cursor m over the same observed point, the course made good can be read off the scale c, and the ground speed at the intersection of the cursor with the appropriate time interval line l. The index arm and cursor are protected by a transparent cover-plate g through which extends the spindle of a knurled knob h for adjusting the index arm.