What is the function of a transponder in an aircraft?

A transponder in an aircraft plays a crucial role in aviation safety and air traffic management by transmitting information about the aircraft's position and altitude to air traffic control (ATC). When an aircraft is equipped with a transponder, it responds to radar signals from ATC by sending back a coded signal that includes vital data such as the aircraft's identification, altitude, and location. This information helps controllers monitor and track aircraft in their airspace, enhancing situational awareness and coordination, especially in busy air traffic environments.

The transponder’s ability to relay this critical information allows for safer separation between aircraft and efficient traffic management. This is especially important in controlled airspaces, where maintaining awareness of all aircraft is essential.

The other options do not accurately describe the function of a transponder. While controlling engine systems and automatic navigation are important functions of an aircraft, they are managed by different systems specifically designed for those purposes. Similarly, providing real-time atmospheric data to the pilot is the responsibility of other onboard instruments, such as weather radar and atmospheric sensors, rather than the transponder itself.