What Is a TCAS?

Answer:

A Traffic Collision Avoidance System or Traffic Alert and Collision Avoidance System (both abbreviated as TCAS) interrogates operating transponders and provides advisory and traffic displays of other aircraft to alert crew of possible conflict in flight paths.

• TA (Traffic Advisory) will be issued when another aircraft is predicted to enter the collision airspace within 25 to 45 seconds and be within 1200ft separation. No evasive action is required.
• RA (Resolution Advisory) will be issued when another aircraft is predicted to enter the collision airspace within 25 seconds and be within 750ft separation. An evasive action is then called for and a mandatory climb or decent rate will be displayed on the VSI.

Ranges and times differ with varying types of aircraft.