Which class of airspace is described as low level controlled airspace from 12,500 to 17,999 feet with ATC clearance and mode C or S required?

Which class of airspace is described as low level controlled airspace from 12,500 to 17,999 feet with ATC clearance and mode C or S required?

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

Answer: (C)

ATC clearance and a functioning altitude-reporting transponder signal that you must have to enter are the hallmarks of a highly regulated, radar-enabled airspace around busy airports. This is Class B airspace, organized in multiple shelves around major airports. Each shelf has its own bottom and top, and some portions reach up into the mid to upper teens thousands of feet, just below the start of Class A at 18,000 ft MSL. Because traffic is dense and converging from many directions, ATC must actively sequence and separate all aircraft, which is why you need explicit clearance to enter and a Mode C (or Mode S) transponder for altitude information. The other classes don’t fit this description as neatly: Class D is typically surface to a few thousand feet around smaller airports with a simpler entry requirement, Class C has its own core-and-shelf structure but usually with different vertical extents and not the same layered, high-altitude shelves, and Class E generally allows entry without a specific ATC clearance in many areas and doesn’t mandate Mode C/S in the same way.

ATC clearance and a functioning altitude-reporting transponder signal that you must have to enter are the hallmarks of a highly regulated, radar-enabled airspace around busy airports. This is Class B airspace, organized in multiple shelves around major airports. Each shelf has its own bottom and top, and some portions reach up into the mid to upper teens thousands of feet, just below the start of Class A at 18,000 ft MSL. Because traffic is dense and converging from many directions, ATC must actively sequence and separate all aircraft, which is why you need explicit clearance to enter and a Mode C (or Mode S) transponder for altitude information. The other classes don’t fit this description as neatly: Class D is typically surface to a few thousand feet around smaller airports with a simpler entry requirement, Class C has its own core-and-shelf structure but usually with different vertical extents and not the same layered, high-altitude shelves, and Class E generally allows entry without a specific ATC clearance in many areas and doesn’t mandate Mode C/S in the same way.