What is the primary purpose of a transponder?

The primary purpose of a transponder is to help air traffic control identify and track aircraft. Transponders are electronic devices installed in aircraft that respond to interrogations from ground-based radar systems. When air traffic control sends a signal, the transponder responds by sending back information, such as the aircraft’s identification, altitude, and sometimes other data. This enables air traffic controllers to maintain a clear picture of air traffic in their controlled airspace, enhancing safety and efficiency.

While transponders do play a supportive role in navigation by providing altitude information (which can be useful for pilots), their main function is specifically aimed at identification and tracking by air traffic control. They do not transmit weather data directly to pilots or communicate with other aircraft in the same manner that other systems might (like ADS-B).