and AF-2S (TB3F-2S), the Guardian entered fleet service on 27 September 1950 with three aircraft delivered to VS-24, with full service introduction shortly after with VS-25. A total of 193 AF-2S Guardians were built. In 1952, the AF-3S (hunter) was introduced, fitting a magnetic anomaly detector (MAD) for the detection of submerged submarines; 40 of this variant were built. The last Guardian was delivered to the Navy in March 1953, with a total of 389 built. 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. Shortly after the end of the war, it began to be replaced by the Grumman S2F Tracker, the U.S. Navy first purpose-built ASW airplane to combine the hunter and killer roles in a single airframe. The last AF retired from active service on 31 August 1955, but it remained in service with the US Naval Air Reserve until 1957. Variants XTB3F-1 Prototypes of two-seat torpedo bomber powered by one 2,300 hp R-2800-46 engine and a Westinghouse turbojet; three built. XTB3F-1S & -2S Two modified XTB3F-1 prototypes with turbojet removed and ventral radome, later redesignated as XAF-1. AF-2S Production variant with 2,400 hp R-2800-48 engine, 193 built. AF-2W Hunter variant with search radar in a ventral radome, 153 built. AF-3S Hunter/Killer variant similar to AF-2S with retractable MAD boom, 40 built. Grumman Model G-90 Proposed combined AF-2S/-2W version, cancelled. Operators United States Navy Aero Union Surviving aircraft 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. On display AF-2S 123100 – National Naval Aviation Museum at NAS Pensacola in Pensacola, Florida. It was the seventh AF-2S produced. The aircraft was operated as a firefighter until 1978. It was acquired by the museum in 1980. It is displayed in the colors of its first Navy assignment, though still carries the number "30" on the cowling, which for many years was the aircraft's call-sign as a firefighting aircraft; 129233 – Pima Air and Space Museum, Tucson, Arizona. This aircraft is displayed as it appeared while serving as an aerial firefighter with Aero Union in California. During this period the distinctive empennage with twin vertical stabilizers on each horizontal tail were removed