Full TCAS operation required an operating _________ transponder on all associated aircraft to send and receive the signals

Full TCAS operation required an operating _________ transponder on all associated aircraft to send and receive the signals

• A. Mode A
• B. Mode S
• C. Mode C
• D. Mode A and C

Answer: (B)

The main idea is that TCAS relies on transponder responses from nearby aircraft to detect and evaluate threats. Mode S transponders provide the necessary data and addressing: they not only reply to TCAS interrogations but also supply unique addressing and altitude information that TCAS uses to identify targets and compute accurate threat assessments and advisories. With only Mode A or Mode C, you’d get limited data (identity or altitude) and the system would have less reliable target differentiation and coordination between aircraft. Therefore, full TCAS operation on all involved aircraft requires an operating Mode S transponder.

The main idea is that TCAS relies on transponder responses from nearby aircraft to detect and evaluate threats. Mode S transponders provide the necessary data and addressing: they not only reply to TCAS interrogations but also supply unique addressing and altitude information that TCAS uses to identify targets and compute accurate threat assessments and advisories. With only Mode A or Mode C, you’d get limited data (identity or altitude) and the system would have less reliable target differentiation and coordination between aircraft. Therefore, full TCAS operation on all involved aircraft requires an operating Mode S transponder.