Which airspace is described as having a 5 NM core from the surface and an outer ring of about 10 NM, with two-way radio and Mode C required?

• A. Class B
• B. Class D
• C. Class A
• D. Class C

Answer: (D)

This describes Class C airspace. In Class C, there is a surface area around the primary airport with a 5 NM core, and a surrounding outer ring that extends out to about 10 NM. To operate in this airspace, you must establish two-way radio communication with ATC and have a Mode C transponder reporting. The core typically rises from the surface up to roughly 4,000 ft above the airport elevation, and the outer shelf reaches up to that same top but starts at a higher radius (about 5 to 10 NM from the airport). This structure and the required equipment differentiate it from other classes: Class B has multiple shelves and requires ATC clearance to enter; Class D surrounds towered airports and doesn’t require Mode C; Class A starts at 18,000 ft MSL and extends upward.