What is the primary purpose of a Primary Surveillance Radar (PSR) in air traffic control?

• A. To detect aircraft and provide range and bearing for non-transponder targets, enabling ATC to track all aircraft.
• B. To provide meteorological data to ATC for weather avoidance.
• C. To identify aircraft solely via transponder replies.
• D. To control aircraft autopilot functions from radar.

Answer: (A)

The main idea is that a primary surveillance radar detects aircraft regardless of whether they transmit a transponder, giving controllers the range and bearing needed to track all targets. It does this by sending radar pulses and measuring the round-trip time to determine distance, while the rotating antenna provides the bearing. This allows visibility of non-transponder or non-cooperative aircraft, which is crucial for maintaining situational awareness and broad airspace surveillance. Weather data comes from separate weather radar systems, not PSR. Transponder-based identification and altitude information are handled by secondary surveillance radar, which relies on replies from aircraft rather than primary echoes. Autopilot control is not a radar function.