What is the function of the transponder in a Cessna 172?

The transponder in a Cessna 172 serves a crucial function by transmitting the aircraft’s position and other information to air traffic control (ATC). This device plays an essential role in maintaining situational awareness for both the pilots and air traffic controllers, especially in congested airspace. By providing a unique code (squawk code) and altitude data, the transponder helps ATC track and identify the aircraft on radar, improving safety and coordination during flights.

Other options represent functionalities that are not associated with the transponder. For instance, measuring fuel flow is managed by separate fuel systems, calculating airspeed involves an airspeed indicator that relies on pitot-static systems, and automatic altitude adjustment is typically handled by the aircraft's autopilot and altitude hold systems. Thus, the transponder’s primary purpose and function is to ensure effective communication between the aircraft and air traffic control, aiding in navigation and safety throughout the flight.