The Grumman AF Guardian is the first purpose-built anti-submarine warfare (ASW) carrier-based aircraft to enter service with the United States Navy.
[4] The "killer" deleted the cannon of the torpedo bomber, but retained the bomb bay, added a third crewmember, a searchlight, and short-range radar, and (as the XTB3F-2S) first flew in January 1949.
[4] The Guardian saw service in the maritime patrol role during the Korean War, however it proved unpopular with pilots, being underpowered and heavy on the controls; the aircraft suffered from a severely high accident rate.
[4] Shortly after the end of the war, it began to be replaced by the Grumman S2F Tracker,[9] the U.S. Navy first purpose-built ASW airplane to combine the hunter and killer roles in a single airframe.
[4] After disposal by the U.S. Navy five Guardians saw many years service with Aero Union based at Chico, California, in the forest firefighting role, the last being retired in 1978.