FOR most pilots of commercial airliners the first sign of an impending mid-air collision comes when a synthesised voice in the cockpit calls out: “Traffic, Traffic”.
This voice comes from a complex piece of equipment called a traffic alert and collision avoidance system (TCAS). Compulsory on European and American commercial airliners, TCAS is designed to prevent a mid-air crash even if a pilot or an air traffic controller has made an error.
The system is based around the transponders fitted into every airliner that air traffic control uses to determine an aircraft’s identity, height, course and speed. On most…
