What is the purpose of a transponder?

The purpose of a transponder is to provide identification and altitude reporting to air traffic control. This device plays a critical role in aviation safety by allowing air traffic controllers to track and identify aircraft in their airspace.

When an aircraft's transponder is activated, it responds to radar signals from ground-based radar systems by sending back information, including a unique identifier known as a squawk code and the altitude of the aircraft as determined by its altimeter. This information is essential for maintaining situational awareness and ensuring safe separation between aircraft in busy airspace.

While navigation data is essential for flight management and safety, it is the transponder's ability to communicate directly with air traffic control that makes it a vital tool for air traffic management. Engine performance metrics and weather updates are important for operational efficiency and safety, but they are not functions of the transponder. Thus, the correct answer captures the essential role of a transponder in the context of air traffic control and aircraft identification.