Which statement about Mode C transponder operation is true?

Which statement about Mode C transponder operation is true?

• A. It provides continuous voice communication with ATC
• B. It transmits altitude only when requested
• C. It provides precise altitude information to ATC for separation
• D. It is used only for military aircraft

Answer: (C)

Mode C is an altitude-encoding transponder that replies to ATC radar interrogations with the aircraft’s altitude data. This coded altitude lets controllers maintain vertical separation between aircraft, even when visibility is limited. The altitude information is transmitted automatically whenever the transponder is interrogated, not only when requested. It’s used by both civil and military aircraft, and it does not provide voice communications. So the statement that Mode C transmits precise altitude information to ATC for separation is the correct one.

Mode C is an altitude-encoding transponder that replies to ATC radar interrogations with the aircraft’s altitude data. This coded altitude lets controllers maintain vertical separation between aircraft, even when visibility is limited. The altitude information is transmitted automatically whenever the transponder is interrogated, not only when requested. It’s used by both civil and military aircraft, and it does not provide voice communications. So the statement that Mode C transmits precise altitude information to ATC for separation is the correct one.