Route Analysis and Flight Planning with Isotachs

Extract

Some meteorological offices now include isotachs (lines joining points of equal wind speed) on forecast upper-air charts for long-range flights. Heretofore, dispatchers and aircrews have been obliged to measure winds from upper-air charts displaying contours only. This meant use of a geostrophic wind template, and correction for cyclostrophic component and latitude. The new contour-isotach charts, in addition to displaying wind speeds more readily, present greater accuracy, since they are determined by forecasters, who may call upon better theoretical know-how, and later observational data. In order to take full advantage of this improvement, Trans-Canada Air Lines has developed two new templates; one for route analysis (determination of the best-time track) and the other for flight planning. These are designed with ease of production in mind as well as simplicity in use. They are produced photographically on heavy film, and have no moving parts.