Reading a VFR Sectional Chart

The sectional chart is the FAA's standard map for flying by sight under visual flight rules. Each one is named after a major city in its area, such as the Seattle or Anchorage sectional, and is drawn at a scale of 1:500,000, which keeps ground features and symbols legible in the cockpit. Over a coloured picture of terrain, water, roads and towns it prints the aeronautical information a VFR pilot needs: airspace, airports, obstructions, radio aids and frequencies.

Reading it well is a large part of the FAA private pilot knowledge test and of safe cross-country flying. Every symbol is defined in the chart legend and explained in the FAA Aeronautical Chart Users' Guide; the European equivalent is the ICAO 1:500,000 chart (see the ICAO VFR aeronautical chart and aeronautical charts).

The sectional chart and its scale

At 1:500,000, one inch on the chart is about 6.86 NM, or 7.9 statute miles. The chart is printed on two sides, a north and a south half, with about two minutes of latitude of overlap between them. The projection is Lambert conformal conic, on which a straight line closely approximates a great circle; because the meridians converge, a true course is measured at the meridian nearest the middle of the leg. Parallels and meridians are printed every 30 minutes with a tick mark every minute, and since a minute of latitude is 1 NM, the ticks along a meridian double as a distance scale.

Around the busiest Class B airports, a masked line marks the area covered by a terminal area chart at 1:250,000, which should be used there for its greater detail. The chart panel carries tables that the map itself cannot hold: control tower frequencies and hours, approach control frequencies, and the special use airspace with its altitudes, times of use and controlling agency.

Airspace depiction: Classes B, C, D and E

Class A, from 18,000 ft MSL to FL600, is not shown on visual charts. The other controlled classes are (see airspace classification):

Class B is built of sectors, each a Class B shelf with its own floor, giving the upside-down wedding cake shape. A "100 over 30" sector runs from 3,000 ft to 10,000 ft MSL, and a floor preceded by + means "upward from above" that altitude, so flight at or below it is outside Class B. Below a shelf the speed limit is 200 kt. A solid magenta line labelled MODE C & ADS-B OUT 30 NM marks the veil around the primary airport, inside which an altitude-reporting transponder and ADS-B Out are required from the surface to 10,000 ft MSL.

Class C normally has a 5 NM core from the surface to 4,000 ft above the airport and a 10 NM shelf from 1,200 ft to 4,000 ft above the airport, but every area is tailored and the chart figures govern. A ceiling of T means up to the floor of an overlying Class B. Boxed magenta notes give the approach frequencies on which to establish two-way communication before entry, generally within 20 NM. Class D areas operating part-time carry a note, and outside their hours revert to Class E or G as the Chart Supplement states.

Class E begins at 1,200 ft AGL unless the chart shows otherwise, and floors above 700 ft AGL other than 1,200 ft are labelled, for example 2400 MSL. Victor airways are drawn as blue centrelines with their V number; they are Class E corridors 4 NM either side of the centreline from 1,200 ft AGL to below 18,000 ft MSL, and a boxed figure gives the total distance between the navaids.

Special use airspace and other areas

All special use airspace except controlled firing areas is charted. Prohibited, restricted and warning areas are drawn with blue hatched borders, alert areas and military operations areas (MOAs) with magenta ones, each labelled with its type and number, such as P-51, R-5706 or A-680. The panel table lists altitudes, times of use and the controlling agency; no NOTAM is issued to announce activation during the permanently listed times, and "TO" an altitude means up to and including it (see special use airspace).

Other areas follow their own conventions:

• Military training routes are charted by centreline and designator with arrowheads showing direction. A four-digit number, as in VR1007, means no segment above 1,500 ft AGL; three digits or fewer mean at least one segment above it. Route widths and altitudes are not charted.
• National security areas have a broken magenta line and ask pilots to avoid them; flight becomes prohibited only by NOTAM. Only temporary flight restrictions relating to national security are charted, with a broken blue line.
• Special conservation areas, such as national parks and wildlife refuges, are outlined; AIM 7-5-6 requests a minimum of 2,000 ft above their surface.
• Miscellaneous activity areas are shown by a letter in a magenta diamond: A for aerobatic practice, G for gliders, H for hang gliders, U for ultralights and UA for unmanned aircraft. A parachute symbol marks a jumping area.

Airport symbols and data blocks

Airports with a control tower and their data are printed in blue, all others in magenta. The symbol tells the pilot about the runways: the runway layout drawn to shape for hard-surfaced runways longer than 8,069 ft or some multiple-runway airports, a circle with the runway drawn inside it for hard-surfaced runways of 1,500 to 8,069 ft, and an open circle for runways that are not hard-surfaced or are shorter than 1,500 ft. Tick marks around a basic airport symbol mean fuel is available; for airports drawn with their runway pattern, the Chart Supplement says whether fuel is available. A star on top means a rotating beacon in operation from sunset to sunrise. Other symbols mark private fields with landmark value (Pvt), abandoned airports, seaplane bases and heliports.

The airport data block beside the symbol is read line by line. The Seattle sectional legend uses this example:

The elevation is the highest point of the usable landing area. An asterisk before the L means lighting limitations described in the Chart Supplement, and a dash means no runway edge lights. ASOS or AWOS frequencies appear when there is no full-time ATIS. "NO SVFR" above the name means fixed-wing special VFR is prohibited there, and a boxed name means special air traffic rules under 14 CFR Part 93.

Runway length is that of the longest active runway, including displaced thresholds but not overruns, rounded at 70: 8,070 ft is charted as 81, 8,069 ft as 80. The details behind every item are in the Chart Supplement.

Terrain, obstructions and maximum elevation figures

Terrain is shown by contours, normally at 500 ft intervals with intermediate ones at 250 ft, by shaded relief lit as if from the north-west, and by colour tints from light green for low ground to dark brown for high ground. Spot elevations give the height of selected points, and the highest terrain on the chart is noted in the legend. The mountain pass symbol gives the pass elevation, which is not a recommended route or clearance altitude.

An obstruction symbol is charted for man-made obstacles more than 200 ft AGL, or more than 299 ft AGL in the yellow tint of a built-up area, with a taller symbol for those 1,000 ft AGL or higher. The bold figure is the elevation of the top in feet MSL and the figure in brackets the height above ground: in the legend's example, 2049 (1149) is a structure rising 1,149 ft above the ground to 2,049 ft MSL. UC means under construction or reported but unverified, flash marks show high-intensity lights, and a group symbol shows only the highest of a cluster. Wind farms are hatched with the MSL elevation of the highest turbine boxed; their lights sit on the nacelles, which can be 200 to 300 ft below the unlit blade tips.

The maximum elevation figure (MEF) is printed in each quadrangle bounded by the ticked lines of 30 minutes of latitude and longitude, in thousands and hundreds of feet MSL: a large 12 with a small 5 means 12,500 ft. The FAA adds the possible vertical error of the source, 100 ft or half the contour interval where the source's interval exceeds 200 ft, to the highest feature and rounds up to the next 100 ft. Where natural terrain is highest it also adds 200 ft for uncharted obstacles:

The MEF is not a safe altitude and adds no clearance margin; it is not verified by field survey, and pilots add their own margin when choosing a cruising altitude (see minimum safe altitudes).

Navaids and checkpoints

VORs, VORTACs and VOR-DMEs have distinct blue symbols, with an information box in blue giving the name, frequency, identifier in Morse code and, for a VORTAC, the TACAN channel. An underlined frequency has no voice, and a heavy-line box marks a flight service station. NDBs are magenta, with their frequencies in kHz. A navaid on an airport may be shown as a small open circle, with its type breaking the top line of the box.

The VOR compass rose around each VOR-type navaid is oriented to magnetic north, so radials read from it are magnetic; DMEs have no rose. Dashed magenta isogonic lines give the magnetic variation from the five-year epoch model (2025 values on the Seattle chart), and local magnetic notes warn of disturbance.

A visual checkpoint is marked by a magenta flag, its proper name underlined; the name is the one used by controllers, not necessarily the feature's official name, and it serves for position reports. VFR waypoints, shown by a four-pointed star, have five-letter names beginning with VP for entry in a GPS. Landmarks such as stadiums or refineries are marked by a small black square with a description, the raw material of pilotage (see dead reckoning and visual navigation).

Chart currency and the legend

Sectionals are revised every 56 days. The title panel gives each edition's validity to the minute: the Seattle sectional of 2026 runs from 0901Z on 3 September to 0901Z on 29 October, with no grace period. Between editions, changes are promulgated by NOTAM and by FAA safety alerts and charting notices; an electronic chart needs the same currency check as paper. The FAA flight-checks charts, generally every four years, to catch obstructions and other changes that were not reported. The legend panel explains every symbol, and when in doubt the Chart Users' Guide is the authority.

Library articles are written for study and exam preparation. They do not replace your aircraft's approved documentation, your operator's procedures or the regulations themselves.