What minimum radio equipment is required for operation within Class C airspace?

• A. Two-way radio communications equipment, a 4096-code transponder, and an encoding altimeter
• B. Two-way radio communications equipment only
• C. A 4096-code transponder only
• D. Encoding altimeter only

Answer: (A)

In Class C airspace you must be able to talk to ATC and be identified on radar with your altitude. Two-way radio communications are needed so you can establish and maintain contact with ATC before and while you are inside the airspace. The radar environment relies on a transponder that not only provides a code to identify your aircraft, but also reports your altitude to ATC. That altitude data comes from an encoding altimeter feeding the transponder. So at minimum you need the radio for communication, the 4096-code transponder with altitude reporting, and the encoding altimeter to supply the altitude information to that transponder. Without any of these elements, ATC cannot reliably communicate with you or monitor your position and altitude in Class C.