TCAS (Traffic Collision Avoidance System)

TCAS (Traffic Collision Avoidance System) is an airborne system that independently monitors the airspace around an aircraft for other transponder-equipped aircraft that may pose a collision threat. It provides advisories to the crew — first as traffic advisories (TAs) and, if the threat increases, as resolution advisories (RAs) commanding a climb or descent.

• TCAS I: Traffic advisories only (light aircraft)
• TCAS II: Traffic and resolution advisories (mandatory for aircraft >5,700 kg or 19+ passengers)
• RA commands take priority over ATC instructions
• Requires Mode S transponder on both aircraft