2.5 Reading Sectional Charts

Reading Sectional Charts

The VFR Sectional Aeronautical Chart is the primary visual map of the NAS. On test day the FAA hands you a printed Airman Knowledge Testing Supplement containing chart excerpts (legends keyed to letters and numbers), and several scored questions ask you to extract a fact from a marked location. Speed matters less than accuracy: a methodical reader scores these reliably.

Scale and Grid

• Sectionals are printed at a scale of 1:500,000 (1 inch = about 6.86 NM).
• Latitude lines run east-west; longitude lines run north-south.
• Each degree is divided into 60 minutes; coordinates read as degrees and minutes (e.g., N33 45' W118 20').
• Grid quadrangles formed by the lines measure 30 minutes by 30 minutes.

Airport Symbols and Color Coding

The airport data block packs essential facts: the identifier (4-letter ICAO code starting with K in the contiguous U.S.), the CT (control tower) frequency, ATIS (Automatic Terminal Information Service) frequency, field elevation in feet MSL, longest runway length in hundreds of feet, and a star for a rotating beacon.

Airspace Boundary Colors

Obstructions (Critical for Drone Pilots)

Towers, antennas, and wind turbines threaten low-altitude drones, so obstruction reading is high-value:

Obstruction labels carry two numbers: the top number is the height in feet MSL (top of the structure above sea level) and the number in parentheses is the height in feet AGL (above the ground at the base).

Worked example: an obstruction marked 1340 (300) stands 300 ft tall (AGL) with its tip at 1,340 ft MSL, meaning the ground there is about 1,040 ft MSL. A drone at 400 ft AGL nearby is roughly 1,440 ft MSL — only about 100 ft above the tower tip, so plan a wider buffer.

Terrain and Maximum Elevation Figures

• Contour lines and color tints show rising terrain.
• Maximum Elevation Figures (MEFs) are large bold numbers in each quadrangle giving the highest known feature (terrain plus obstacles plus a vertical buffer) in hundreds of feet MSL — 34 means 3,400 ft MSL. MEFs are a fast safety reference, not a regulatory altitude.

Other Useful Symbols

• Visual checkpoints appear as flagged purple symbols.
• Power lines show as lines with small towers; railroads as crosshatched lines; highways as bold lines.
• Blue = water, yellow tint = urban/built-up area, helpful for VLOS planning.

Exam Strategy and Common Traps

1. Find the lettered/numbered location in the supplement first.
2. Identify the airspace around it (color and floor/ceiling).
3. Identify the airport (color = tower status).
4. Read obstructions and MEFs last.

The top trap is mixing the MSL and AGL obstruction numbers — remember the parenthetical is AGL. The second trap is reading a non-towered (magenta) airport as towered (blue).

Using the Testing Supplement Efficiently

The FAA supplies chart excerpts in the Airman Knowledge Testing Supplement, and each excerpt has a printed legend. A common mistake is to try to memorize every symbol; instead, learn the high-frequency ones the test repeats — airport color, airspace boundary colors, obstruction MSL/AGL labels, and MEFs — and rely on the supplied legend for the rest. Questions usually mark a location with a letter or arrow, so your job is to anchor on that exact point and read outward: airspace first, then the nearest airport and its data block, then obstructions, then terrain.

Reading outward from the marked point keeps you from being distracted by busy chart features elsewhere in the excerpt.

Why Obstruction Reading Is a Drone-Specific Skill

Manned aircraft cruise far above the towers and turbines that fill a sectional, but a drone at 400 ft AGL operates in exactly the band where these obstructions live. A 400 ft AGL tower is at your altitude limit, and a 1,000 ft broadcast antenna pierces well above it. The chart gives you both heights so you can plan a buffer: the AGL number tells you how high the structure rises from its base, while the MSL number lets you compare it to your drone's MSL altitude when terrain varies.

Wind turbines, increasingly common, are often shown as grouped symbols, and guy wires on tall antennas extend hundreds of feet outward and are invisible from a distance — a real-world hazard the chart hints at but cannot fully convey.

Worked Scenario

An excerpt marks your launch point near an obstruction labeled 2049 (568). The structure rises 568 ft AGL with its tip at 2,049 ft MSL, so the ground at its base is about 1,481 ft MSL. If your launch site sits at the same elevation, a drone at 400 ft AGL reaches roughly 1,881 ft MSL — still 168 ft below the tip, meaning the tower towers over your legal ceiling. The correct plan is to keep well clear laterally rather than trying to overfly it. Reading both numbers and converting to a common reference is the analytical skill the chart questions reward.