Art Of The Chart

The first time a person unfolds an aviation map, which he soon discovers is called a chart, he quickly observes that it is nothing like any other chart - or map - he has ever seen. It is full of complex concentric rings in many colors and irregular variations, cryptic coded print, exotic symbols, and many other mysterious secrets. The chart appears to be cluttered with markings that can appear terribly confusing and seemingly incomprehensible, even while scrutinizing it at a desk. How in the world can he possibly get any use out of this thing in the confines of a bouncing and cramped airplane cockpit?

A fold or two more and he will find the coded legend of the chart's contents. This legend, while fairly inclusive, often can leave even an experienced pilot with more questions than answers. Many of the chart legend's explanations and descriptions are rudimentary and difficult to understand when applied to the actual chart layout, while other chart features aren't even mentioned.

The charts pilots use during visual flight rules (VFR) flight are called VFR sectional aeronautical charts. The more detailed VFR terminal charts (officially terminal area charts) at half the scale offer the pilot twice the detail of sectionals, but are only available to depict the airspace surrounding the nation's busiest airports. Sectional charts - which, if they overlap terminal chart areas, depict the territory of mutual coverage within a bold white box labeled "TAC" - are the most commonly utilized aeronautical charts. There is also a VFR chart called a WAC (world aeronautical chart), pronounced whack. The symbology is nearly identical (although less detailed) to that of the sectional and terminal charts, but WACs are little used in flight training because their extremely large area of coverage and tiny geographical details are most useful only for very long flights.

Although VFR sectional and terminal charts use nearly identical symbology, there are a few notable differences. For example, the VFR sectional chart depicts airports with hard-surface runways between 1,500 feet and 8,069 feet long within solid blue (for tower-controlled airports) or magenta (for nontowered airports) circles, while terminal charts boldly outline the runway layouts at all airports with hard-surface runways of 1,500 feet or longer. On the sectional chart, hard-surface runways are outlined only if they are 8,070 feet or greater in length.

VFR terminal charts also display IFR arrival routes (light-blue arrowheads with a depiction of an airliner) and departure routes (light-blue arrowheads only). These show the approximate paths jets take into and out of the primary airport within the terminal area.

Sectional charts are printed on both sides; instructions on the chart tell pilots how to plot courses from the one side of the chart to the other. Sectionals also feature a contour interval key on the cover, which is topped with the point of highest elevation on the chart along with its geographical coordinates. VFR terminal charts are printed on one side, but many include on the reverse side a simplified VFR flyway chart with stylized landmark and airspace depictions of the same coverage area. Wide light-blue lines on these flyway charts show suggested VFR transition routes and altitudes.

With these notable exceptions, VFR sectional and terminal area charts employ virtually the same symbology. These chart features apply, by and large, to WACs as well.

VFR Chart Legends - Decoding The Codes

VFR chart legends, even when they display or make mention of aeronautical information, often employ abbreviations and symbology that are either not decoded or, if decoded, not explained. For example, the Airport Data section of the chart legend notes that "SVFR" stands for special VFR, "FSS" stands for flight service station, and "CTAF" stands for common traffic advisory frequency-but it does not clarify what any of those services are or how they work. The airport data information block omits airport ground control frequencies, which are found on the Control Tower Frequencies table. The table also features all airport control tower (CT) frequencies, local times of control tower operation, and the availability of airport surveillance radar and precision approach radar (ASR/PAR). Airport traffic pattern altitudes (TPA), which cannot be obtained anywhere on VFR charts, are also omitted (see the Airport/Facility Directories or A/FD). Except for rotating beacon location symbology (a hollow star), runway lighting availability (L), and pilot controlled lighting (PCL) availability (*), airport lighting and signage information is also omitted from VFR charts.

Just below, in the Radio Aids to Navigation and Communication Boxes section, the legend omits the fact that "TWEB" denotes a transcribed weather broadcast, that "HIWAS" is hazardous in-flight weather advisory service, "VOR" stands for very high frequency (VHF) omnidirectional radio range, "RCO" stands for remote communication outlet, or that "ASOS" and "AWOS" stand for automated surface observing system and automatic weather observing system, respectively. Although it is true that the abbreviations for ASOS/AWOS do appear above in the Airport Data section of the chart legends, they are denoted together as Automated Surface Weather Observing Systems. This section does, however, denote "NDB" as nondirectional beacon and "FSS" as flight service station.

The right side of the Radio Aids to Navigation and Communication Boxes features three blue facilities boxes, the top left denoting a VOR with a collocated flight service station, the top right depicting a FSS, and the lower box indicating a VOR that can broadcast FSS voice transmissions. (A VOR facility box without the heavy blue line around the name indicates a VOR at a location without a FSS, although the VOR may offer remote communication access to a FSS.) The frequencies along the top of the box are for communication with the associated FSS. The emergency frequency of 121.5 MHz, while always monitored by all FSSes, is not shown, nor is the En route Flight Advisory Service (called flight watch over the radio) frequency of 122.0, also monitored by FSSes. In addition to the discrete frequencies printed above the FSS box, all FSSes monitor the common frequency of 122.2 MHz, which is also omitted from the top of the box.

When calling a flight service station, always (with the exception of flight watch) use the facility's name along with the word radio, e.g. Reno Radio. The FSS boxes (thick outlined, when alone or when depicted in concert with a VOR) may be topped with the frequency 122.1R. The "R," as the legend denotes, stands for receive. Thin VOR boxes mean there is no collocated FSS, but they too can feature a frequency with the "receive" R. It is the FSS named in the rectangular box that "receives" communication over the specified radio frequency from the pilot, who listens to the FSS over the specified VOR frequency. On your call-up, tell Flight Service where you're located, so that they can transmit over the appropriate VOR: "Nashville Radio, Cessna Four-Three-Seven-Yankee on 122.1, listening over Hinch Mountain VOR, over."

The Airport Traffic Service and Airspace Information section of the chart legend is more complete than the others, but it too features incomplete or confusing entries. One symbol denotes the ceiling (in hundreds of feet msl - mean sea level) of Class D controlled airspace; add two zeros to that figure to obtain the airspace ceiling relative to your altimeter. A minus sign indicates "up to but not including" that altitude, which generally means other controlled airspace overlies that Class D area.

The chart legend entries just below the Class D ceiling symbol denote Class E airspace. Class E is controlled airspace that, with a very few VFR exceptions, does not require pilots to communicate with air traffic control (ATC). It exists primarily to afford pilots the more restrictive controlled airspace visibility and cloud clearance rules (see FAR 91.155) without the obligation of communicating with ATC. IFR Victor airways, illustrated as light blue lines with a bold blue "V" followed by the numbered name of the airway emanating from VORs, are also Class E airspace.

Class E airspace has various "floors," some at the surface, and most - utilized for transitioning into and out of airport areas not far above ground - at 700 or 1,200 feet agl.

Special use airspace, denoted on VFR charts below Class E and Victor airway legends, consists of prohibited (P-), restricted (R-), alert (A-), and warning (W-) areas (which are essentially oceanic alert areas outside of U.S. jurisdiction), in blue and military operations areas (MOAs) in magenta. Another type of uncharted special use airspace is controlled firing areas (CFA), locales of military artillery activity which utilize spotters who guarantee the safe passage of civil aircraft. Another area of national security activity, which is illustrated on the chart but not in the chart legend, is the magenta national security disk. This disk is located in areas of undisclosed national security activity which the federal government requests that pilots avoid (time/altitude details are in an adjacent magenta box). All special use airspace dimensions, times of operation, and controlling agencies (any beginning with the letter "Z" denote an air route traffic control center; their radio frequencies are omitted on VFR charts) depicted on a specific chart is explained in the Special Use Airspace table.

Along the bottom central column of the Airport Traffic Service and Airspace Information section of the legend there is a magenta flag, which denotes a visual checkpoint. These can be misleading on the chart because the underlined name of the checkpoint can be any word or group of words and can be any color, not just magenta (although the flag always remains magenta). In addition, the flag can be some distance from the underlined word(s) with which it is associated - and in heavy chart clutter, that can mean you never find the associated flag. In California, the Sausalito VOR's frequency is underlined because there is no voice available on that frequency, and the name of the VOR is underlined because the VOR facility itself is a visual checkpoint.

Visual checkpoints, which can be any identifiable geographical or constructed feature (even IFR intersections can be designated visual checkpoints) are accepted by ATC but are often never used, while landmarks that are not designated as visual checkpoints are. In the San Francisco Bay Area, for example, pilots or controllers rarely - if ever - refer to "Camp Parks" Army base or "A Street," both designated visual checkpoints. Meanwhile, virtually every aircraft arriving and departing the East Bay under VFR is given instructions with reference to "Lake Chabot," the "Oakland Coliseum," and/or the "Mormon Temple," even though none of these landmarks is designated a visual checkpoint on the charts. Keep that in mind in an unfamiliar area and tell the controllers if "their" visual checkpoints are unfamiliar to you.

12 Other VFR Chart Secrets

Although space prohibits the coverage of every single VFR chart feature here, I have included a list of a dozen useful VFR chart "secrets" that will help round out your chart knowledge:

1. Remote communications outlets (RCO) are antenna facilities that let you talk to the associated flight service station on the displayed frequency, thereby extending its useful communications area.
2. "Mode C veils" mandate that all aircraft operating within the depicted area (a 30-nm radius from the primary Class B airport) use altitude-encoding altimeters, regardless of their altitude.
3. Control Areas are Class E airspace which, unless noted, begin at 14,500 feet msl and extend to the floor of Class A airspace to provide IFR traffic with controlled airspace while outside of terminal and high-altitude airspace.
4. Air defense identification zones (ADIZ) are areas where the control of aircraft is required in the interest of national security; for example, the oceanic and Mexican borders. The U.S./Canadian border does not require an ADIZ.
5. Chart name, time zones, adjoining chart names, military training route (MTR) symbology, adjacent VOR identifiers and frequencies (not Morse codes), and national park information are all located along chart borders.
6. Although most VOR facilities are depicted within a blue compass rose, for reasons of avoiding excess clutter, some are truncated and can be very hard to find.
7. Specific AWOS services are not differentiated in the chart legend but are on the chart airport data entries themselves as AWOS-A, AWOS-1, AWOS-2, and AWOS-3.
8. "Thin" magenta rings within MOAs, which include altitude notation, denote areas that are not included within the surrounding special use airspace.
9. Chart scales are 1:500,000 for sectional charts and 1:250,000 for terminal charts (1;1,000,000 for WACs). Verbal scales are 1 inch equals 6.86 nm for sectionals and 1 inch equals 3.43 nm for terminal charts. Each chart also features a graphic scale in nautical miles, statue miles, and kilometers along the upper edge of the depicted area.
10. There are 54 U.S. sectional and 29 U.S. terminal area charts (and many other charts and reference materials) published by the FAA's National Aeronautical Charting Office (NACO).
11. Of the 29 available VFR terminal charts, 19 feature VFR flyway charts on the reverse side: Atlanta, Baltimore-Washington, Charlotte, Chicago, Cincinnati, Dallas-Fort Worth, Denver, Detroit, Houston, Las Vegas, Los Angeles, Miami, Phoenix, St. Louis, Salt Lake City, San Diego, San Francisco, Seattle, and Tampa/Orlando.
12. VFR flyway routes and altitudes are suggested, as ATC's directives always supersede these chart depictions.

VFR sectional and terminal charts are packed with airspace, airport, communication, navigation, and topographical information that is invaluable to pilots on all VFR flights. The chart legend and layout often leave much to be desired in the way of cartographical logic. An excellent resource for further interpretation of aeronautical charts is the National Aeronautical Charting Office's Aeronautical Chart User's Guide, which AOPA members can view on AOPA Online ( www.aopa.org/members/files/chart_guide ). Aeronautical charts are a pilot's primary informational resource for planning and conducting VFR flights, and with thorough exploration and careful attention to details, VFR sectional and terminal area charts will reveal their valuable secrets and become your most frequently consulted aviation reference tools.

Aviation writer David Montoya has been a corporate and airline pilot. He has been flying for 19 years, including 11 as a CFI.