Which airspace is described as having a core from the surface to 4,000 feet AGL with an outer shelf from 1,200 to 4,000 feet and requiring two-way radio communication and a Mode C transponder?

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

Answer: (D)

This describes Class C airspace. It has an inner core from the surface up to 4,000 feet AGL around a busy airport, with an outer shelf from 1,200 feet to 4,000 feet AGL. To fly there, you must establish two-way radio communication with ATC before entering and maintain it while inside, and you must be equipped with a Mode C transponder for altitude reporting. This combination of a surface-based core, an outer shelf starting at 1,200 feet, and the communications plus transponder requirements is what defines Class C. Class B would involve a more complex, multi-shelf structure with explicit ATC clearance; Class D requires two-way radio communication but typically does not require a Mode C transponder; Class E doesn’t require two-way communications in the same way and lacks this two-tiered core/shelf arrangement around a tower.