MIT Lincoln Lab TCAS

TCAS
On-board warning system proves to be pilots' -- and air travelers' -- best friend
BY COLLEEN O'HARA
It was a bright, sunny morning -- a good day for flying, Capt. Ross Sagun thought as he boarded the 737 and took his seat in the cockpit. Sagun anticipated a smooth trip from Las Vegas to Denver, and he and the crew prepared for departure.
Sagun received clearance from the control tower and taxied to the runway for takeoff. Flight attendants strapped themselves into their seats, and passengers settled in for the hour-and-a-half ride. Within minutes, the airplane was off the ground and cleared to climb to 7,000 feet. From the air, the hotels and casinos that once towered overhead were dwarfed by the surrounding desert and mountains.
Suddenly, at 6,700 feet, Sagun realized the flight would not be as easy as he had thought. He had just turned the airplane eastward into the sun, when an on-board warning system alerted him that a small, private aircraft was headed his way, in line for a head-on collision. On the round screen in front of him, a white diamond representing the other aircraft changed to an amber circle, and a computerized voice alerted the crew: "Traffic! Traffic!" Moments later, the circle changed to a red square, and the computer voice warned, "Conflict!" and then, "Descend! Descend!" With only seconds to spare, the 737 plunged and the single-engine plane passed just 300 feet overhead.
The warning system that saved the life of Sagun, his crew and the passengers was the Traffic Alert and Collision Avoidance System-II (TCAS-II). "TCAS is my best friend," Sagun said. "It has proven very reliable. We look at it as our last-ditch safety net. It's the last tool we have to keep the metal from touching."