Allende class is the name of anti-submarine frigates used by the Mexican Navy. Allende class frigates are former United States Navy Knox-class frigates, and they were bought in 1997. They form the Mexican Gulf Fleet of the Mexican Navy. They are used for anti-submarine and offshore patrol duties. This is because weapons are reduced to only one 127 mm Mk 42 DP gun and four fixed ASW torpedo launchers. Electronic combat systems are also reduced and consist only of one gun fire control System. Western Electric SPG-53F and one MK 114 ASW fire control system for ASW torpedos of 324 mm. All hulls have ASROC Mk 16 octuble launcher system. Allende class frigates can operate one small on-board helicopter (MBB Bo 105).