The 46 Knox-class frigates were the largest, last, and most numerous of the US Navy's second-generation anti-submarine warfare (ASW) escorts. Originally laid down as ocean escorts (formerly called destroyer escorts), they were all redesignated as frigates on 30 June 1975, in the 1975 ship reclassification plan and their hull designation changed from 'DE' to 'FF'. The Knox class was the Navy's last destroyer-type design with a steam turbine powerplant.
Due to their unequal comparison to destroyers then in service (larger size with lower speed and only a single propeller and 5-inch gun), they became known to a generation of destroyermen as "McNamara's Folly", a jab at then-Secretary of the Defense Robert McNamara.[2]
These ships were retired from the US Navy at the end of the Cold War due to their relatively high running costs, a declining defense budget, and the need for ships with a more advanced anti-submarine capability. None of the ships served more than 23 years in the US Navy, and by 1994, all of the class had been retired, although some remain in service with foreign nations such as Egypt, Taiwan, Thailand, and Mexico.
The design soon ran into problems however, with the US Navy deciding to switch to conventional 1,200psi (8,300kPa) boilers, requiring a redesign, and the ships became longer and heavier in order to accommodate the less compact power plants. Furthermore, Sea Mauler was cancelled in 1965, leaving the ships to complete without any anti-aircraft system except the 5" gun.[4][5]
The steam plant for these ships consists of two Combustion Engineering or Babcock & Wilcox"D" type boilers, each equipped with a high-pressure (supercharger) forced draught air supply system, with a plant working pressure of 1,200psi (8,300kPa) and 1,000°F (538°C) superheat and rated at 35,000shp (26,000kW) driving a single screw. This gives them a speed of 27kn (50km/h; 31mph).[6][7]
The ships were designed primarily as anti-submarine warfare (ASW) platforms.[5] Their main anti-submarine sensor was the large bow-mounted AN/SQS-26CX low-frequency scanning sonar, operating as an active sonar at a frequency of about 3.5kHz and passively at 1.5–4kHz. The active modes of operation included direct path, to a range of about 20,000yd (18,000m), bottom bounce, and convergence zone, which could give ranges of up to about 70,000yd (64,000m), well outside the capability of ASROC, and requiring the use of a helicopter to exploit.[5][8][9] An eight-round ASROC launcher (with 16 missiles carried) was fitted between the gun turret and the bridge, backed up by four fixed 12.75in (324mm)Mark 32 anti-submarine torpedo tubes. A flight deck and hangar for operating the DASH drone helicopter was fitted aft.[10][5]
Construction
Ten ships were authorized in Fiscal Year 1964, sixteen in 1965, and ten each for FYs 1966, 67 and 68; six were canceled in 1968, and four more in 1969. While the FY64 and FY65 ships were ordered from four different shipyards, later ships (DE-1078 onwards) were all ordered from Avondale Shipyards in order to cut costs.[4] These ships were built on a production line, with prefabricated modules being assembled upside down, welded together and then rotated into an upright position.[10] They were originally commissioned as destroyer escorts (DEs) 1052–1097 in 1969–1974,[5] but were redesignated as frigates (FF) on 30 June 1975.[11]
The USSJoseph Hewes(FF-1078) and subsequent ships of the class were modified to enable them to serve as flagships. The primary change was a slightly different arrangement of the "Officer's Country" staterooms with additional staterooms in a new 01 level structure which replaced the open deck between the boats. The stateroom on the port side under the bridge was designated as a "flag" stateroom, with additional staterooms for flag staff when serving as a flagship. These ships have been referred to as the Joseph Hewes-sub-class [citation needed].
Bow modifications including bulwark and horizontal spray strake on USSBowen(FF-1079) in 1984.
The Knox class had been criticized for deck wetness and there were a number of instances of damage to the forward weapons mounts in heavy seas, so the class were refitted with "hurricane bows" beginning with Bagley(FF-1069) in 1979. The modification heightened the bow section, adding bulwarks and spray strakes to prevent burrowing into on-coming seas and to better protect the forecastle armament.[12]
Twenty-five ships of the class (DE-1052, 1056, 1063–1071 and 1078–1097) were refitted with the AN/SQS-35(V) Independent Variable Depth Sonar, an active sonar operating at about 13kHz.[5][6][7] The IVDS' sonar transducers were packaged within a 2-ton fiberglass-enclosed "fish" containing the sonar array and a gyro-compass/sensor package launched by the massive 13V Hoist from a stern compartment, located just beneath the main deck, to depths of up to 600ft (180m). The IVDS could take advantage of water layer temperature conditions in close-range (less than 20,000yd (18,290m)) submarine detection, tracking and fire-control.[citation needed] The AN/SQS-35 "fish" was later modified to tow an AN/SQR-18A TACTASS passive towed array sonar.[13][14] The DASH drone proved unreliable, and following its withdrawal in 1973, the ships' helicopter facilities were expanded to accommodate the larger, manned, Kaman SeaspriteLAMPS 1 helicopter.[15]
Thirty-one ships (DE-1052–1069 and 1071–1083) were fitted with an eight-round Basic Point Defence Missile System (BPDMS) launcher for RIM-7 Sea Sparrow missiles in place of the cancelled Sea Mauler short range surface to air missile system, while Downes(FF-1070) was fitted with a NATO Sea Sparrow (IBPDMS) launcher. It was planned to equip the other 14 ships with Sea Chaparral, based on the Sidewinder air-to-air missile, but this plan was abandoned.[16] Most ships were refitted with a 20mm (0.79in)Phalanx CIWS aft during the 1980s, replacing the Sea Sparrow launcher.[13]
In the 1970s, several ships received an interim surface warfare upgrade allowing Standard ARM anti-radar missiles to be fired from the ships' ASROC launcher.[16] Later, all ships were modified to launch Harpoon anti-ship missiles from the ASROC launcher, which could carry two Harpoons, with two more carried in the ships' ASROC magazine.[13]
Baleares class
Five modified ships were built in Spain for the Spanish Navy as the Baleares-class. In these ships, the Sea Sparrow launcher and helicopter facilities were replaced by a Mk 22 launcher for sixteen Standard surface-to-air missiles, giving them a limited area air-defence capability.
Chi Yang class
Chi Yang class ROCN Yi Yang (FFG-939)Chi Yang class ROCN Lan Yang (FFG-935)Chi Yang class ROCN Yi Yang (FFG-939) has 10 SM-1 missiles installed in two forward twin box launchers on top of the helicopter hangar, and two triple box launchers installed between the stack and the hangar.Chi Yang class ROCN Ning Yang (FFG-938)Port Left Rear View.
In the 1990s, the US agreed to transfer eight Knox-class frigates to the Republic of China Navy (ROCN). The ROCN, anticipating future difficulties in maintaining the steam plants on these ships, originally contemplated an ambitious plan to replace these plants with diesel engines. However, due to budget considerations and the acquisition of newer ships, this plan is now believed to have been shelved. These frigates were renamed the Chi Yang-class and assigned to the ROCN 168 Patrol Squadron.[17]
By 2005, the ROCN had removed several systems from the retired Gearing class upgraded World War II-vintage destroyers and transferred them to seven of the Chi Yang class. These systems include SM-1MR Standard missile in box launchers, H-930 modular combat system, DA-08/2 air/surface search radar, and STIR-180 illuminating radar. Each Chi Yang-class frigate has 10 SM-1 missiles installed in two forward twin box launchers on top of the helicopter hangar, and two triple box launchers installed between the stack and the hangar, pointing to port and starboard.[18]Chi Yang (FFG-932) did not receive the upgrade.
The ASW capability of the Chi Yang class is provided by its SQS-26 bow-mounted sonar, SQS-35(v) VDS, SQR-18(v)1 passive TAS, MD500 ASW helicopter, Mk-16 8-cell Harpoon/RUR-5 ASROC box launcher, and four Mk46 324mm (12.8in) torpedoes. While on ASW patrol, the frigate will carry two Harpoon SSMs and six ASROCs in its Mk-16 box launcher.[19]
There are some speculations that these ships will probably be upgraded with Hsiung Feng III missiles.[20]
Regarding to the outdated battle system onboard and the ageing ships, the class is expected to be replaced by the newly built Taiwanese Light Frigate. [21]
The RUR-5 ASROC is an all-weather, all sea-conditions anti-submarine missile system. Developed by the United States Navy in the 1950s, it was deployed in the 1960s, updated in the 1990s, and eventually installed on over 200 USN surface ships, specifically cruisers, destroyers, and frigates. The ASROC has been deployed on scores of warships of many other navies, including Canada, Germany, Italy, Japan, Taiwan, Greece, Pakistan and others.
The Fleet Rehabilitation and Modernization (FRAM) program of the United States Navy extended the lives of World War II-era destroyers by shifting their mission from a surface attack role to that of a submarine hunter. The FRAM program also covered cruisers, aircraft carriers, submarines, amphibious ships, and auxiliaries. The United States Coast Guard also used this term in the 1980s for the modernization of its Hamilton-class cutters.
The Gearing class was a series of 98 destroyers built for the U.S. Navy during and shortly after World War II. The Gearing design was a minor modification of the Allen M. Sumner class, whereby the hull was lengthened by 14 ft (4.3 m) at amidships, which resulted in more fuel storage space and increased the operating range.
Garcia-class frigates were United States Navy warships. These frigates were originally ocean escorts bearing the hull classification DE until 1975. The ships were commissioned between 1964 and 1968 and decommissioned between 1988 and 1990.
The Republic of China Navy is the maritime branch of the Republic of China Armed Forces (ROCAF).
The California class was a pair of nuclear-powered guided-missile cruisers operated by the United States Navy between 1974 and 1998. Other than their nuclear power supply and lack of helicopter hangars, ships of the California class were comparable to other guided-missile cruisers of their era, such as the Belknap class. The class was built as a follow-up to the nuclear-powered Long Beach, Bainbridge, and Truxtun classes. Like all of the nuclear cruisers, which could steam for years between refuelings, the California class was designed in part to provide high endurance escort for the navy's nuclear aircraft carriers, which were often limited in range due to their conventionally powered escorts continuously needing to be refueled.
Destroyer leader (DL) was the United States Navy designation for large destroyers from 9 February 1951 through the early years of the Cold War. United States ships with hull classification symbol DL were officially frigates from 1 January 1955 until 1975. The smaller destroyer leaders were reclassified as destroyers and the larger as cruisers by the United States Navy 1975 ship reclassification so destroyer escorts could be reclassified as frigates (FF) in conformance with international usage of the term.
The Cheng Kung-class frigates are eight guided-missile frigates in service in the Republic of China Navy (ROCN). They are based upon the U.S. Oliver Hazard Perry class and built by China Shipbuilding Corporation in Kaohsiung, Taiwan under license throughout the 1990s as part of the Kuang Hua I project. These frigates served as the mainstay of the ROCN's area air defense capability prior to the acquisition of the Keelung (Kidd)-class destroyers in 2005. They are designated with the hull classification PFG rather than FFG used by the Oliver Hazard Perry class.
The Chikugo-class destroyer escort was a class of destroyer escorts built by the Japanese Maritime Self-Defense Force as the successor of the Isuzu class, with the same ASW mission. This class was followed by JDS Ishikari. This is the first Japanese destroyer escort class to carry ASROC anti-submarine missiles.
USS Stein (DE-1065) was a Knox-class destroyer escort, later redesignated as a frigate (FF-1065) of the United States Navy. She was named after Tony Stein, the first Marine to receive the Medal of Honor for action in the Battle of Iwo Jima.
USS Gray (FF-1054) was a United States Navy Knox-class frigate. She was named for Marine Corps Sergeant Ross F. Gray, who was a posthumous recipient of the Medal of Honor.
USS Connole (FF-1056) was a Knox-class frigate, named for Commander David R. Connole, Captain of USS Trigger when the submarine was lost in battle in March 1945.
USS Rathburne (FF-1057) was a Knox-class frigate of the US Navy. Despite the different spelling, she was named for Continental Navy officer John Rathbun (1746-1782).
USS Meyerkord (FF-1058) was a Knox-class frigate in service with the United States Navy from 1969 to 1991. She was scrapped in 2001.
ROCS Lan Yang (FFG-935) is a Chi Yang-class frigate of the Republic of China Navy. She was formerly in service as the USS Joseph Hewes (FF-1078), a Knox-class frigate of the United States Navy.
USS Brewton (FF-1086) is a Knox-class frigate of the United States Navy and the first ship of her name. She is currently in service with the Republic of China Navy as the ROCS Fong Yang (FFG-933).
The Bronstein-class frigates were United States Navy warships, originally laid down as ocean escorts, but were all redesignated as frigates on 30 June 1975 in the United States Navy 1975 ship reclassification and their hull designation changed from DE to FF.
The Baleares class were a group of five frigates built for the Spanish Navy in the late 1960s and 1970s. The ships were a modified version of the American Knox-class frigates. The key differences are the replacement of helicopter facilities by a medium-range surface-to-air missile system and associated radars. Constructed between 1968 and 1976, the Baleares class began entering service in 1973 and formed the 31 Escort Squadron, based at Ferrol. The five ships were upgraded several times during their service lives. The ships were retired beginning in the mid-2000s and replaced by the Álvaro de Bazán-class frigates on a one-to-one basis.
The Allende class is a series of four anti-submarine frigates used by the Mexican Navy. Allende-class frigates are former United States Navy Knox-class-ships which were acquired beginning in 1997. They form the Mexican Gulf Fleet of the Mexican Navy. They are used for anti-submarine and offshore patrol duties. All four ships were taken out of service by 2016 and one was sunk as an artificial reef in 2022. In 2024, it was announced the other three hulls would be donated for use as artificial reefs.
The Dealey-class destroyer escorts were the first post-World War II escort ships built for the United States Navy.
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