What are the two basic functions of TCAS?

The correct answer highlights the essential capabilities of TCAS, which stands for Traffic Collision Avoidance System. TCAS is designed to enhance flight safety by providing pilots with critical information about other aircraft in close proximity to their flight path.

Surveillance refers to the system's ability to monitor surrounding air traffic by receiving transponder signals from nearby aircraft. This function allows TCAS to gather data on the altitude and position of other aircraft within its operational range.

Interrogation involves TCAS actively querying nearby transponder-equipped aircraft to request their position and altitude information. This interaction helps build a comprehensive picture of the air traffic environment and is crucial for collision avoidance.

Together, these two functions enable TCAS to assess the risk of potential mid-air collisions and provide timely alerts to pilots, thereby improving situational awareness and safety during flight operations.