Chart symbols

This element is about reading a sectional chart fluently — pointing at any symbol and stating what it means without consulting the legend. The DPE will hand you a chart, point at a feature, and ask "what does this mean?" — boundary lines, shadings, MEFs, airport symbols, obstructions. The grade is on recognition speed and accuracy, not memorization of every legend entry.

Two color rules, two line-style rules, three vertical references. Color tells which traffic system. Line style tells the enforcement level. Numbers tell altitude. Everything else is lookup against the Chart User's Guide.

The picker below cycles through the 31 symbols you'll meet most often on a sectional. Tap each one to see the plain-English meaning, what it changes about your flight, and the common misreads that trip students up.

The legend convention behind sectional charts

The legend isn't random — it follows two consistent conventions that you can lean on when a symbol surprises you. Blue equals towered or higher-tier controlled airspace (Class B, Class D, towered airports). Magenta equals lower-tier controlled or non-towered (Class C, Class E, non-towered airports, the Mode C veil). The color tells you which system you're in.

Solid line equals firmer enforcement; dashed line equals softer. Solid blue (Class B) requires explicit clearance to enter. Dashed blue (Class D) requires only two-way comm. Solid magenta (Class C) requires two-way comm. Dashed magenta (Class E surface area) requires no clearance for VFR but tightens weather mins. The line-style step from solid to dashed corresponds to a step down in entry difficulty.

Faded shading marks the Class E floor altitude. Magenta vignette = 700 AGL floor; blue vignette = 1,200 AGL floor. No shading means Class G all the way up to the Class E floor wherever that is in the area. The vignette fade is most visible at the edge of a shaded region.

The chart conventions live in the FAA Aeronautical Chart User's Guide; airspace structure itself is defined in 14 CFR Part 71, with operating rules in Part 91 subpart B (Class E operations under §91.127, weather minimums under §91.155-class-c-d-e). Within these conventions, every individual symbol you encounter falls into a category — boundary line, shading, navaid, obstruction, etc. — and the symbol pattern carries information about the type.

Airspace boundary lines and altitude boxes

Boundary lines come in four flavors plus two shadings. For each, an altitude box (or vignette color) tells you the vertical extent.

Class B (solid blue line). Stair-step altitude boxes per sector — the wedding cake. A box reading 100/SFC means ceiling 10,000 MSL, floor surface (the inner core). 100/30 means ceiling 10,000 MSL, floor 3,000 MSL (a shelf). Both numbers are in hundreds of feet MSL. Entry requires explicit clearance per §91.131.

Class C (solid magenta line). Two-ring structure with altitude boxes: inner ring typically 40/SFC (4,000 AGL to surface, 5 NM radius), outer shelf 40/12 (4,000 AGL to 1,200 AGL, 10 NM radius). Entry requires two-way radio comm established per §91.130.

Class D (dashed blue line). Single ceiling shown in a dashed blue box, in hundreds of feet MSL — e.g., [27] means 2,700 MSL ceiling, surface as the implied floor, within ~4 NM. Entry requires two-way comm per §91.129.

Class E surface area (dashed magenta line). No clearance required for VFR, but weather mins tighten to 3-152 inside the boundary. Typical around non-towered airports with published instrument approaches per Part 71.

Class E vignettes are the shading-floor convention: faded magenta = 700 AGL floor; faded blue = 1,200 AGL floor (CONUS default). Below the floor is Class G.

Mode C veil (thin solid magenta circle at 30 NM). Not an airspace class — an equipment requirement under §91.215 and §91.225. Surface to 10,000 MSL within 30 NM of a primary Class B airport; Mode C transponder and ADS-B Out required regardless of whether you enter Class B itself.

Airport symbols

The first information is the color: blue = towered, magenta = non-towered. Within each color:

• Filled circle = at least one paved (hard-surface) runway
• Open circle = soft surface only (grass, dirt, water)
• Runway depiction inside the circle = actual runway alignment, in scale-appropriate orientation
• Square = airport with services (fuel, etc.) available
• Star inside = beacon
• L or asterisk = lighted
• R in a magenta circle = private or restricted-use (prior permission required)
• H in a magenta circle = heliport (helicopter-only)
• Anchor or seaplane symbol in a magenta circle = seaplane base

Each airport symbol is paired with a data block. The data block lists: identifier (KFFZ, etc.), elevation in MSL, longest runway in hundreds of feet, lighting indicator, and frequency (CTAF for non-towered, tower for towered). Time zone is sometimes shown.

For non-towered fields, the frequency printed near the symbol is CTAF — pre-load it before arrival. For towered fields, it's the tower frequency.

Navaids, obstructions, and other markings

Navaids. Hexagon = VOR. Hexagon inside a rectangle = VORTAC (VOR plus military TACAN, providing DME for civilian aircraft). Hexagon with a small square = VOR-DME (VOR plus civilian DME). Dotted bullseye = NDB (older low-frequency beacon, rarely used). A graduated outer circle around a VOR/VORTAC is the compass rose — oriented to magnetic north, used to identify radials.

Obstructions. Single tower = vertical line with a dot or small triangle on top. Group obstruction = clustered symbols. Lighted obstruction = additional notation or lightning-bolt-like indicator. Heights show in two formats: MSL on top (what your altimeter reads at the tip), AGL in parentheses below (the structure's height above ground). The difference implies the terrain elevation at the base.

MEF (Maximum Elevation Figure). A large blue number per sectional quadrangle, in hundreds of feet (e.g., 7⁵ = 7,500). Highest known obstacle in the quadrangle plus a buffer. Layer the FAA-recommended margin on top — +1,000 AGL flat, +2,000 AGL mountain — then apply §91.159 hemispheric rule to pick a legal cruise altitude.

Other markings. Parachute canopy symbol = active skydiving area; gliders may be operating from any local gliderport (magenta G in a circle); ultralight activity uses a magenta UL in a circle. All three call for heightened scan when nearby.

Worked examples:

• Phoenix-area sectional read. Around Falcon Field (KFFZ) you'd see: a blue airport symbol with internal runway depiction (KFFZ is towered, Class D, ceiling 2,500 MSL shown as [25]). A few miles west, Phoenix Sky Harbor (KPHX) shows a blue airport symbol surrounded by solid blue Class B stair-step boxes (e.g., 100/SFC inner core, 100/40 outer shelves) AND solid magenta Class C boundary inside the Class B because KPHX has both airspace types layered. A thin solid magenta circle at 30 NM from KPHX marks the Mode C veil — Mode C + ADS-B Out required throughout. Nearby MEFs in the surrounding quadrangles read 4⁵, 5², 7⁵ (4,500 / 5,200 / 7,500). South of the city, antenna farms show as obstruction symbols with MSL/AGL altitude pairs.

• Class E floor identification game. A non-towered field (magenta filled circle) sits inside a region of faded magenta vignette. Just beyond, the vignette transitions to faded blue. Outside both shadings is Class G all the way up to the higher Class E floor. Reading: at the airport, Class E starts at 700 AGL (magenta vignette); a few miles away, Class E starts at 1,200 AGL (blue vignette); far enough away (a rare situation in CONUS), Class E might not start until 14,500 MSL. The vignette transition isn't just decorative — it tells me whether VFR at 800 AGL puts me in Class E or Class G, with the corresponding weather minimum implications.