page_title: AN/APS-20
section_title: Aircraft
hierarchical_section_title: AN/APS-20 / Applications / Aircraft
caption_attribution_description: A U.S. Navy Douglas AD-3W Skyraider early warning plane (BuNo 122880) in flight in the early 1950s.
context_page_description: The AN/APS-20 was an airborne early warning, anti-submarine, maritime surveillance and weather radar developed in the United States in the 1940s. Entering service in 1945, it served for nearly half century, finally being retired in 1991. Initially developed at MIT under Project Cadillac, the radar was developed to be carried by aircraft to extend the sensor range of ships by placing a radar at altitude. Although developed for carrier-borne operation, first being installed in the single-engined General Motors TBM-3W Avenger, it was also used in larger four-engined airframes, the last carrier being a fleet of Avro Shackleton AEW.2 converted maritime partrol aircraft. Similarly, although developed for detecting aircraft, it saw extensive service in anti-submarine and maritime patrol roles and was one of the first radars to be used in researching extreme weather like hurricanes by agencies like the ESSA. As well as the United States, the radar was used by a large number of services in other countries, including the French Navy, JMSDF, RAF and RCAF. Early versions of the radar could see a low flying aircraft at 65 nautical miles and a ship at 200 nautical miles.
context_section_description: Avro Shackleton AEW.2 – 12 converted.
  Boeing B-29 Superfortress – 3 converted.
  Boeing PB-1W – 32 converted.
  Canadair Argus Mk.1 – 13 built.
  Fairey Gannet AEW.3 – 44 built.
  Douglas AD-W / EA-1 Skyraider – 367 built, including one XAD-1W prototype.
  Douglas Skyraider AEW.1 – 50 built.
  Douglas DC-6 – 2 converted.
  Goodyear ZPG-2W – 5 built.
  Goodyear ZPG-3W – 4 built.
  General Motors TBM-3W Avenger – 27 converted.
  Grumman Avenger Mk.3W2 – 8 delivered.
  Grumman TB3F-1S / AF-2W Guardian – 156 built, including one XTB3F-1S prototype.
  Lockheed PO-2W / WV-2 / EC-121 Warning Star. 232 built.
  Lockheed P2V-3W Neptune – 30 built.
  Lockheed P2V-4 / P-2D Neptune – 51 built, including P2V-2S prototype.
  Lockheed P2V-5 / P-2E Neptune – 424 built.
  Lockheed P2V-7 / P-2H Neptune – 287 built, including 48 assembled by Kawasaki.
  Lockheed EP-3E Orion – 2 converted.
  Lockheed WP-3A Orion – 4 converted.
  Sikorsky HR2S-1W – 2 built.
caption: Douglas AD-3W Skyraider
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