DronelixPart 107 chart reading
What does a dashed blue circle mean on a sectional chart?
It marks a Class D boundary. On this fictional training chart, the ring surrounds Marlow Muni. The boxed 27 gives its ceiling in hundreds of feet above mean sea level: 2,700 feet MSL.
For a Part 107 flight inside that active Class D area, get prior ATC authorization. The blue ring tells you where Class D is. The 27 tells you the ceiling; it is not a radius or a frequency.
Class D surface area around the towered airport. A Part 107 flight within it needs prior ATC authorization under 14 CFR 107.41.
The charted Class D ceiling is 2,700 feet MSL. The number is in hundreds of feet, and MSL is measured from sea level.
Try the question from Dronelix
This is question faa107-air-061 from the app's Part 107 airspace bank. Choose an answer, then read the reason.
Show the answer and FAA sources
First answer. A dashed blue circle is a Class D surface area, and the blue airport symbol inside it marks a towered field. 14 CFR 107.41 requires prior ATC authorization for a Part 107 operation in Class B, C or D airspace, or within the lateral boundaries of a Class E surface area designated for an airport.
The magenta shading is a different clue. In this training scene it marks a Class E floor at 700 feet AGL, not a Class E surface area. Check the FAA Aeronautical Chart Users' Guide and AIM 3-2-5 for the chart convention and Class D description.
Use a current chart for an actual flight
This drawing is an exam exercise, with fictional airports and simplified boundaries. A real operation needs current aeronautical information and any required authorization. The FAA publishes chart guidance and Part 107 authorization instructions.
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