Quick Facts
- Type
- Safety System
- Also Known As
- TCAS
- Used By
- Pilots, ATC
Definition#
TCAS (Traffic Collision Avoidance System, also ACAS — Airborne Collision Avoidance System) is an aircraft system that interrogates nearby transponders to track traffic. It issues Traffic Advisories (TAs) and Resolution Advisories (RAs) when collision risk is detected.
Why It Matters Operationally#
TCAS is the last line of defense against mid-air collisions. Pilots are trained to follow RA commands (climb/descend) immediately, even if they conflict with ATC instructions. TCAS II is mandatory for aircraft over 5,700 kg or with 19+ passenger seats.