Whats TCAS or ACAS?
TCAS or ACAS is a Traffic or Airborne alert and Collision Avoidance System. The new name is ACAS, Airborne Collision Avoidance System. It is an aircraft (airborne) system based on secondary surveillance radar (SSR) transponder signals which operates independently of ground-based equipment to provide advice to the pilot on potential conflicting aircraft that are equipped with SSR transponders. The purpose of the system is to show to the pilot the position of the traffic around him and indicate when there is a potential conflict according to 2 criteria: Altitude and Distance. IMPORTANT note: Be aware that since the system reacts on SSR transponder signals, it could ONLY react if the other traffic is visible through those signals. In other words, if that other aircraft effectively switch on his transponder and squawks altitude!! Otherwise TCAS/ACAS will NOT work at all and you will get no warnings of close traffic.
