Which system helps pilots avoid mid-air collisions?

The Traffic Collision Avoidance System (TCAS) is specifically designed to help pilots avoid mid-air collisions. This system continually monitors the airspace around an aircraft for other transponder-equipped aircraft that may present a collision threat. TCAS works by utilizing information from the aircraft's transponder, which sends out a signal that is received by other transponder-equipped aircraft nearby.

When a potential conflict is detected, TCAS provides the flight crew with advisories, which typically include resolution advisories (RAs) that instruct the pilot on whether to climb or descend in order to avoid an impending collision. This real-time data and automated threat response capability significantly enhance the safety of flight operations by allowing pilots to take proactive measures against mid-air collisions, making it a crucial system in modern aviation.

While Air Traffic Control (ATC) plays a vital role in maintaining safe separation between aircraft, it primarily operates under ground-based instructions rather than providing real-time avoidance maneuvers like TCAS does. The Navigation Assistance System (NAS) and Ground Control Approach (GCA) are concerned with navigation and landing guidance rather than actively preventing mid-air collisions, further highlighting the distinct purpose and importance of TCAS in collision avoidance.