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Aeronautical Charts

Scale is key difference between VFR aeronautical chart types

By Elizabeth A. Tennyson

The term aeronautical chart refers to all sorts of maps used for air navigation provided that they include at least some of the following information: topographic features, hazards and obstructions, navigation routes and aids, airspace, and airports. There are nine types of aeronautical charts in general use in the United States, but many are used mainly for instrument flying, including en route low altitude charts, en route high altitude charts, instrument approach procedures, instrument departure procedures, and standard terminal arrival procedures. For now, we'll focus on charts used in VFR flying.

Regardless of where you live, you are sure to be exposed to sectional aeronautical charts, more commonly called sectionals. These charts, which use a one to 500,000 scale, are designed to help pilots with visual navigation of slow or medium speed aircraft. Sectionals emphasize visual checkpoints and topographical information. Among the highlights of these charts are heights for obstacles and terrain; radio frequencies for navigation, communication, and weather; airport information; controlled airspace; and restricted areas. These are the charts you are most likely to use on cross-country flights.

Unlike sectional charts, VFR terminal area charts are available only for select areas. They use a scale of one to 250,000 and should be used for navigation when they are available. Terminal charts give pilots more information about the busy areas in and around Class B airspace. They have the same types of information as sectional charts but offer even more details, especially about airspace, airports, obstructions, terrain, and visual checkpoints.

World aeronautical charts or WACs use a one to 1 million scale and are best used over long distances by pilots of fast airplanes. Each chart covers a large area, and the scale means that much of the detail of terminal and sectional charts is lost. Nevertheless, WACs do include cities and towns, main roads, railroads, distinctive landmarks, frequencies, airways, and restricted areas.

Finally, airport taxi charts are sometimes used by VFR pilots. Like terminal charts, they are available for many of the largest airports. Taxi charts help pilots find their way, expediting the safe flow of traffic. They are identified by the official airport name, such as Dulles International Airport.

Because flying safely has a lot to do with having good information, it's important to fly with current charts appropriate to the type of flying you do.