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The Knox class was the result of congressional opposition to mounting costs of the Brooke FFG class Missile Frigate after only six Brooke class ships were built. Accordingly their mission was altered to ASW escort from that of a general escort. The original designation of the Knox class was "Destroyer Escort" (DE) being changed in June 1975 to "Frigate" (FF) but retaining the original hull number.
Knox class frigates, all of which have been retired, fulfilled a Protection of Shipping (POS) mission as Anti-Submarine Warfare (ASW) combatants for amphibious expeditionary forces, underway replenishment groups and merchant convoys.
They were designed as convoy escorts and were to replace the hundreds of Destroyer Escorts (DE) built during World War II which were being disposed of in the 1960s. They were built in favor of the Garcia (DE-1040) class program of FY1961-63. Initially ten ships were authorized in FY1964 (1052-1061), followed by 16 ships in FY1965 (1062-1077), ten in FY1966 (1078-1087), ten in FY1967 (1088-1097), and the last ten (1098-1107) in FY1968. DE 1102-1107 (six ships) were cancelled in 1968 in favor of proposed destroyer construction, and three more were cancelled (DE 1098-1100) on 24 February 1969 due to cost overruns in the SSN programs of FY1968. DE-1101 was cancelled on 9 April 1969. The program cost as reported in 1974 was $1.425 billion or an average of almost $31 million per unit. They were part of the low end mix of naval building strategy.
Knox class frigates represent the most successful of the second generation escort vessels built after World War II; cruising at 22 knots on one boiler and fitted with a 5-bladed, fifteen foot wide propeller. They were designed to operate the DASH helicopter, an unmanned ASW platform. Instead however, from 1972-1977 they were modified to accommodate the SH-2D LAMPS (Light Airborne Multi-Purpose System) helicopter during which their flight deck and hangar were enlarged. Two ships, FF-1061 and FF-1070 were never modified to accommodate the SH-2D LAMPS helicopter.
The large SQS-26CX bow mounted sonar dome was the design center of the ship, ASROC launcher complementing the ship's primary purpose of ASW. Two twin sets of Mk32 torpedo tubes angled forward from the midships structure (firing the Mk46 lightweight torpedo) provided additional ASW capability with improved loading capability over the exposed triple mounts on other classes. A variable depth sonar (SQS-35) was installed in 35 ships in the late 1970s to provide better detection capabilities against submarines operating below thermal layers. In the 1980s, 31 ships were fitted with the SQR-18A towed arrow system.
For anti-surface roles the ships originally had only the moderate range rapid-fire Mk42 5-inch/54 gun fitted on the bow with a wide arc of fire. A modification of the ASROC launcher allowed two cells to launch Standard missiles in surface-to-surface mode was initially pursued though in 1976 the Ainsworth tested a similar modification to allow firing of Harpoon SSMs and this capability was retrofitted into most ships.
Anti-air capability was introduced with the addition of the Mk25 BPDMS Sea Sparrow launcher on the fantail in 31 ships from 1971-75 (1052-1069, 1071-1083). This eight tube launcher could fire modified radar guided Sparrow missiles. The Mk29 Nato Sea Sparrow launcher was evaluated on Downes (FF-1070) along with the SPS-58 threat detection radar and IPD/TAS (Improved Point Defense/Target Acquisition System) and later incorporated in other classes, including many aircraft carriers. The baseline radar suite for the Knox class included SPS-10 and SPS-40 search radars.
The 46 Knox class frigates were phased out from 1991-94. In the mid 1990s they initially formed the backbone of the Innovative Concept Reserve Training Program. Under this program, the last eight ships remaining in service were designated Type II Reserve Training Frigates [FFT], while 32 other frigates were deactivated and designated Type III ships. The Type III ships can be completely reactivated in 180 days. Each of the eight Reserve Training Frigates ship had its own reserve crew, and was also assigned four "nucleus crews" which would man the 32 Type III ships. For instance, FF-1091 Miller transferred to the Naval Reserve Force in January 1982, and thereafter was employed in the western Atlantic and Caribbean areas. She decommissioned in October 1991 and was stricken from the Naval Vessel Register in 1995.
The Reserve Training Frigates ships were to be homeported in New York, Mobile and Ingleside Texas. The Reserve Training Frigates were all inactivated in 1994, and some of them have been disposed of through the Security Assistance Program (SAP) foreign military sale program.
Replacing the Knox-class frigates in this role were seven of the FFG-7 Oliver Hazard Perry frigates in the Naval Reserve Fleet. These ships fulfilled an important role in reducing the Active force's operational and personnel tempo by responding to contingencies such as the Haitian embargo, counter-narcotics operations, and overseas deployments, such as Carat 96 in the Western Pacific.
The Knox class has the distinction of being the last Destroyer type ships built for the U.S. Navy equipped with boiler & steam propulsion.
Following is a list of the 46 Knox class Frigates by Hull Number and then alphabetically.