What is TCAS?
TCAS (Traffic Collision Avoidance System) is an onboard system that independently monitors nearby aircraft and issues collision avoidance instructions to pilots - without any input from ATC.
How it works
TCAS interrogates the transponders of nearby aircraft to determine their range, altitude, and closure rate. It operates in two stages:
Traffic Advisory (TA) - 35-48 seconds before projected collision. Alerts the pilot to traffic: "Traffic, traffic." The pilot looks for the aircraft visually.
Resolution Advisory (RA) - 15-35 seconds before projected collision. Gives a specific vertical maneuver: "Climb, climb" or "Descend, descend." The pilot MUST follow the RA, even if it contradicts ATC instructions.
The controller's role
When a TCAS RA fires, the controller must NOT issue instructions that conflict with it. The pilot follows the RA, and the controller deals with the aftermath - re-sequencing traffic, re-establishing separation.
A TCAS RA means the ATC system failed to keep aircraft separated. It's the last line of defense.
In radarcontrol.io
The sim computes conflict predictions with resolution advisories (climb, descend, turn, speed). Conflicts show as red on the radar with the projected closest approach. The scoring system heavily penalizes separation violations (-200 points per conflict, -150 for severe).