The AN/APG-66 radar is a solid state medium range (up to 150 km) pulse-Doppler planar array radar originally designed by the Westinghouse Electric Corporation (now Northrop Grumman) for use in early generations of the F-16 Fighting Falcon; later variants use the AN/APG-68 or the AN/APG-83. This radar was employed in all domestic and export versions of the F-16 A/B models throughout the production. Subsequent upgrades have been installed in many varying aircraft types, including the U.S. Customs and Border Protection's C-550 Cessna Citation, US Navy P-3 Orion, and Piper PA-42 Cheyenne II's, as well as the Small Aerostat Surveillance System (SASS). Primary air-combat mode is look-down. In that mode, the AN/APG-66 can detect a fighter-size plane at a range of 34.5 Nautical miles (55.6 kilometers). Four modes are available in air-to-air combat. In dogfight mode, the radar scans a 20 degrees x 20 degrees field. In high-g maneuvers, it scans a 40 degrees x10 degrees pattern. The radar system consists of the following line-replaceable units:
