Which statement describes how a transponder affects visibility to ATC radar?

Which statement describes how a transponder affects visibility to ATC radar?

• A. It transmits weather data.
• B. It only transmits when requested by pilot voice.
• C. A transponder provides visibility on ATC radar by replying to interrogations.
• D. It automatically updates flight plans.

Answer: (C)

ATC radar visibility relies on the transponder’s active response to radar interrogations. When the air traffic radar system (secondary surveillance radar) sends an interrogation, the aircraft’s transponder automatically replies with a coded identification (and often altitude in Mode C, plus other data in newer modes). This exchange lets the controller see a labeled target with altitude on the radar screen. The transponder does not transmit weather data, doesn’t wait for pilot voice requests, and doesn’t automatically update flight plans. The essential idea is that ATC radar relies on the transponder’s reply to detect and identify the aircraft.

ATC radar visibility relies on the transponder’s active response to radar interrogations. When the air traffic radar system (secondary surveillance radar) sends an interrogation, the aircraft’s transponder automatically replies with a coded identification (and often altitude in Mode C, plus other data in newer modes). This exchange lets the controller see a labeled target with altitude on the radar screen. The transponder does not transmit weather data, doesn’t wait for pilot voice requests, and doesn’t automatically update flight plans. The essential idea is that ATC radar relies on the transponder’s reply to detect and identify the aircraft.