Obstacle_Collision_Avoidance_System
The Obstacle Collision Avoidance System (OCAS) is designed to alert pilots if their aircraft is in immediate danger of flying into an obstacle. OCAS uses a low power ground-based radar to provide detection and tracking of an aircraft's proximity to an obstacle such as high buildings, power line crossings, telecom towers or wind turbines. This capability allows the visual warning lights to remain passive until an aircraft is detected and known to be tracking on an unsafe heading.
OCAS is currently the only FAA approved Audio Visual Warning System (AVWS) approved in the National Airspace. OCAS is also the only AVWS approved by the International Dark Sky Association.[citation needed]
OCAS is operational in the US, Canada, Norway and Germany.[citation needed] OCAS developer was acquired by Vestas in 2011.[1]