Is a mode C transponder required in Class C airspace?

A mode C transponder is indeed required when operating within Class C airspace at or above a certain altitude. The regulations specify that all aircraft must have a transponder with altitude reporting capability when flying in Class C airspace, which generally extends from the surface up to 4,000 feet above the airport elevation.

This requirement is in place to enhance situational awareness for both pilots and air traffic controllers, allowing for better management of air traffic in busy environments. In Class C airspace, the transponder effectively communicates the aircraft’s altitude and location, which is crucial for maintaining safety and preventing collisions. It's important for pilots to understand that this requirement applies specifically to when the aircraft is operating at or above the specified altitudes, not just when in the airspace, which is the focus of this answer.

The other options suggest different scenarios that do not accurately reflect the regulatory requirements for operating in Class C airspace. Understanding the specific requirements for equipment such as transponders is essential for compliance with aviation regulations and for ensuring safe flying practices.