How to Read a Sectional Chart for Part 107 Chart Questions (Worked Example)

Why chart questions trip people up

The Part 107 knowledge test hands you a chart excerpt and asks something concrete: which frequency is the CTAF, what airspace sits over a point, how tall is that obstacle. The answer is printed on the chart. What fails people is not the aviation knowledge, it is reading order: a sectional packs six or seven facts into two lines of text next to an airport, and if you do not know which number is which, 135.075 and 123.075 look interchangeable.

This guide decodes one real excerpt step by step. Every rule below comes from the FAA Aeronautical Chart Users' Guide (sections "Airports", "Airport Data", "Airspace" and "Obstructions") and the legend printed on the sectional itself. The airport data was cross-checked against the FAA airport database for the current cycle.

The excerpt: St George Regional (SGU), Las Vegas Sectional

Open the practice image for this airport at Part 107 chart image questions. It is a crop of the Las Vegas Sectional effective Sep 3, 2026, centered on ST GEORGE RGNL in Utah. Here is everything printed in it, in the order you should read it:

Now the decoding, line by line.

Step 1: Read the airport data block in the FAA's order

The Chart Users' Guide, "Airport Data", fixes the order of the text next to an airport. Top line: name and identifier. Then, when the airport has one, the control tower frequency ("CT") and the ATIS or automated weather frequency. Then one line that always reads the same way: elevation, lighting, longest runway length, and the CTAF.

For SGU:

• ST GEORGE RGNL (SGU): the name is spelled as the FAA database spells it. There is no "CT -" entry on this airport, which already tells you something: SGU has no control tower (the FAA database lists it as NON-ATCT). The data block is in magenta, which the "Airports" section of the guide uses for airports without a control tower; towered airports are drawn in blue.
• AWOS-3PT 135.075: an Automated Weather Observing System, type 3PT, broadcasting on 135.075 MHz. You listen to it. You do not transmit on it. The FAA database lists this exact entry: "SGU AWOS-3PT 135.075".
• 2884: airport elevation in feet above mean sea level. The database value is 2883.6 ft, rounded to 2884 on the chart.
• *L: the "L" means the runway has lighting; the asterisk means there are limitations (for example, lights that operate only part of the night or on request). The guide sends you to the Chart Supplement for the details. A plain "L" with no asterisk means lighting in operation sunset to sunrise.
• 93: the longest runway, in hundreds of feet. 93 means 9,300 feet. The guide rounds this to the nearest hundred, so a runway of 9,250 ft would also print as 93.
• 123.075 with the C in a circle: the Common Traffic Advisory Frequency. The circled C is the symbol the legend reserves for the CTAF. This is the number the exam is asking for when it says "CTAF".
• Boxed WX: the FAA weather camera symbol (the chart legend lists it under airport symbols). It belongs to the airport line but it is not a frequency and has no number of its own.

Step 2: Why 135.075 is not the CTAF

This is the single most common chart error on the Part 107 test, so it deserves its own step.

Two frequencies sit next to SGU. The one on the line above, 135.075, is labeled AWOS-3PT: a weather broadcast. The one on the lower line, 123.075, is followed by the circled C: the CTAF. The guide's rule is simple: the CTAF is the frequency marked with the circled C, and nothing else qualifies. A weather frequency is labeled by its system (ATIS, AWOS, ASOS). A tower frequency is labeled "CT". If the question asks for the CTAF, find the circled C and read the number immediately to its left.

The FAA airport database confirms it: CTAF 123.075 (UNICOM is on the same 123.075 at SGU), AWOS-3PT 135.075, and the St George RCO on 122.5. Three different numbers, three different jobs.

Why it matters for a remote pilot: 14 CFR 107 does not require you to carry a radio, but the ACS expects you to know how manned traffic communicates around a non-towered airport, and a question about the CTAF is the way the test checks it.

Step 3: The magenta dashed ring is Class E at the surface

Around SGU there is a circle drawn with a dashed magenta line. The "Airspace" section of the guide assigns each class a line style:

• Class B: solid blue lines, with floor and ceiling in each sector.
• Class C: solid magenta lines, with floor and ceiling in each sector.
• Class D: a dashed blue line. The ceiling is printed inside brackets in hundreds of feet MSL, for example [27] for 2,700 ft MSL.
• Class E that begins at the surface: a dashed magenta line. No ceiling in brackets, because Class E continues upward until it meets the next controlled airspace.
• Class E that begins at 700 ft AGL: the soft magenta shading (vignette) along the outer edge of an area.
• Class G: whatever is left, up to the Class E floor.

SGU has no tower and no dashed blue ring, so there is no Class D. The dashed magenta ring means controlled airspace, Class E, reaches down to the ground inside the circle. The FAA database agrees: Class E airspace "Y", service continuous.

The exam consequence: 14 CFR 107.41 requires ATC authorization to operate in Class B, C or D airspace, or within the lateral boundaries of the surface area of Class E airspace designated for an airport. Inside the dashed magenta ring at SGU you need an authorization (LAANC where available). Outside the ring, at the low altitudes a small UAS flies, you are in Class G and no authorization is needed under 107.41, though 107.43 still bars interfering with airport operations.

A quick test for any chart question: dashed blue means Class D and look for the bracketed ceiling; dashed magenta means Class E at the surface; shaded magenta means Class E starting at 700 ft AGL.

Step 4: Obstructions: bold MSL, parentheses AGL

Northwest of the runway, next to a group-obstacle symbol, the chart prints 2889 with (256) beneath it. The "Obstructions" section of the guide explains the pair: the top number is the elevation of the top of the obstruction above mean sea level, the number in parentheses is its height above ground level.

So this obstruction tops out at 2,889 ft MSL and stands 256 ft above the terrain. Subtract and you get the ground elevation at its base: 2,889 - 256 = 2,633 ft MSL.

Which number does a Part 107 pilot use? Your 400 ft limit under 107.51 is measured above ground level, and the structure exception lets you fly within a 400 ft radius of a structure up to 400 ft above its uppermost limit. The AGL figure, 256, is the one that goes into that arithmetic. The MSL figure, 2889, is the one a manned pilot compares with an altimeter.

The guide also distinguishes symbols by height: a short symbol for obstacles below 1,000 ft AGL, a taller one for obstacles 1,000 ft AGL and above, and a doubled symbol for a group of obstacles. The symbol here is the group type, so expect more than one structure at that spot.

Do not confuse an obstruction with a spot elevation. The dot labeled 4227 east of the airport is a spot elevation: the height of a point of terrain, 4,227 ft MSL, with no AGL figure because it is the ground itself. An obstruction always has a symbol and, when the height is known, an AGL figure in parentheses.

Step 5: The rest of the crop

• ST GEORGE, in large type with the yellow built-up area, is the city. The yellow shape is what a city looks like from the air at night.
• The square labeled tower inside the city is a landmark feature from the legend's landmark group, drawn as a visual reference, not as an airspace element.
• 122.5, printed above the navaid box, is a Flight Service frequency: the FAA database lists the St George RCO (remote communications outlet) on 122.5. The guide places FSS frequencies above the navaid box.
• The box reading ST GEORGE 108.6 Ch 23 UTI is a navaid data box: the St George VOR, frequency 108.6 MHz, DME/TACAN channel 23, identifier UTI, with the Morse code for UTI beside it. It is not a radio you talk on. The exam will not ask you to navigate by it, but it will trust you not to mistake 108.6 for a CTAF.
• The thin brown lines with numbers like 3000 and 3500 are terrain contours in feet MSL.

A reading checklist for any chart question

1. Find the airport name and whether the text is blue (towered) or magenta (non-towered).
2. Read the data line left to right: elevation, lighting, longest runway in hundreds of feet, CTAF with the circled C.
3. Separate the frequencies by their labels: CT is tower, ATIS/AWOS/ASOS is weather, circled C is CTAF, numbers above a navaid box belong to Flight Service.
4. Identify the airspace by line style: solid blue B, solid magenta C, dashed blue D with the ceiling in brackets, dashed magenta E at the surface, shaded magenta E at 700 ft AGL.
5. For an obstacle, read MSL on top and AGL in parentheses, and use AGL for the 400 ft rule.
6. For a point on the ground with no symbol, treat it as a spot elevation.

Practice this

The same reading order works on every sectional. Try it on real chart excerpts at Part 107 chart image questions: 10 questions are free, and the Part 107 Pass ($69, one-time) adds 15 more with explanations. If you want the questions spaced over your remaining study days, the Part 107 study plan builds the calendar.

Sources

• FAA Aeronautical Chart Users' Guide, sections "Airports", "Airport Data", "Airspace" and "Obstructions".
• Las Vegas Sectional Aeronautical Chart, effective Sep 3, 2026, legend panel.
• FAA airport database (current cycle), entry SGU: ST GEORGE RGNL, NON-ATCT, elevation 2883.6 ft, AWOS-3PT 135.075, CTAF 123.075, UNICOM 123.075, ST GEORGE RCO 122.5, Class E service continuous.
• 14 CFR 107.41, 107.43 and 107.51.
• FAA Remote Pilot - Small Unmanned Aircraft Systems Airman Certification Standards.

Version 1.0 · 2026-10-27 · verified against the FAA airport database (current cycle) and the Las Vegas Sectional effective Sep 3, 2026; technical review by the Rotate editorial team.