Knox-class frigateUSS Robert E. Peary (FF-1073) and the skyline ofSan Francisco in the background
Class overview
Builders	Todd Shipyard, Seattle and San Pedro Lockheed Shipbuilding and Construction Company Avondale Shipyard
Operators	United States Navy  Republic of China Navy  Egyptian Navy  Hellenic Navy  Mexican Navy  Royal Thai Navy  Turkish Naval Forces
Preceded by	Garcia class /Brooke class
Succeeded by	Oliver Hazard Perry class
Subclasses	Baleares class Allende class Phutthayotfa Chulalok class
Built	1965–1974
In commission	1969–1994 (USN)
Planned	55
Completed	46
Cancelled	9[1]
Retired	46 (USN), some were transferred to other countries where they are in active service
Preserved	2
General characteristics
Type	Ocean escort (1964–1975) Frigate (1975–1994)
Displacement	4,065long tons (4,130 t) (full load)
Length	438 ft (134 m)
Beam	46 ft 9 in (14.25 m)
Draft	24 ft 9 in (7.54 m)
Installed power	2 × 1,200 psi (8,300 kPa) boilers 35,000 shp (26,000 kW)
Propulsion	1 × Westinghouse steam turbine 1 ×shaft
Speed	27 kn (50 km/h; 31 mph)
Range	4,500 nmi (8,300 km; 5,200 mi) at 20 kn (37 km/h; 23 mph)
Complement	17 officers, 240 enlisted
Sensors and processing systems	AN/SPS-10 Surface Search Radar AN/SPS-40 Air Search Radar AN/SPS-67 Surface Search Radar AN/SQS-26 active/passiveSonar AN/SQS-35 active/passive towedSonar AN/SQR-18Towed array sonar system AN/SPG-53 Mk68 Gun Fire Control System
Electronic warfare & decoys	As BuiltAN/WLR-1C – AN/ULQ-6C and AN/SLA-15 (Comprising AN/SLQ-26 System) AN/SLQ-32 Electronics Warfare System andMark 36 SRBOC
Armament	As built: 1 ×5 in (127 mm)/54caliber Mark 42 gun 1 × Mk-16 8–cellASROC launcher 2 × dualMark 32Mark 46 torpedo launchers First refit: 1 × Mk-25 8–cellRIM-7 Sea Sparrow (BPDMS) (DE-1052–1069 and 1071–1083) 1 × Mk-29 8–cellRIM-7H Improved Sea Sparrow (IBPDMS) (DE-1070) Mk-16 2 cells converted to launchHARPOON Second refit: 1 ×Phalanx CIWS (RIM-7/7H Sea Sparrow removed)
Aircraft carried	1 ×QH-50 (DASH) helicopter 1 ×SH-2 Seasprite (LAMPS I) helicopter (refit)

The 46Knox-class frigates were the largest, last, and most numerous of theUS Navy's second-generationanti-submarine warfare (ASW) escorts. Originally laid down asocean escorts (formerly calleddestroyer escorts), they were all redesignated asfrigates on 30 June 1975, in the1975 ship reclassification plan and their hull designation changed from 'DE' to 'FF'. TheKnox class was the Navy's last destroyer-type design with asteam turbine powerplant.

Due to their unequal comparison todestroyers 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 DefenseRobert McNamara.^[2]

These ships were retired from the US Navy at the end of theCold 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 asEgypt,Taiwan,Thailand, andMexico.

Designated SCB No. 199C, theKnox was planned as the follow-on to the twin5" gun-armedGarcia class frigates and theTartar missile-equippedBrooke-class frigates. Their initial design incorporated the prior classes' pressure-fired boilers in a similar-sized hull designed around the massive bow-mountedAN/SQS-26 sonar, with increased endurance and reduced crew size. Anti-submarine armament was to consist ofRUR-5 ASROCanti submarine missiles together with theQH-50 DASHdronehelicopter, while defensive armament was to be theRIM-46 Sea Mauler short rangeanti-aircraft missile backed up by a single5-inch/54 caliber Mark 42 gun.^[3]

The design soon ran into problems however, with the US Navy deciding to switch to conventional 1,200 psi (8,300 kPa) 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 twoCombustion Engineering orBabcock & Wilcox"D" type boilers, each equipped with a high-pressure (supercharger) forced draught air supply system, with a plant working pressure of 1,200 psi (8,300 kPa) and 1,000 °F (538 °C) superheat and rated at 35,000 shp (26,000 kW) driving a singlescrew. This gives them a speed of 27 kn (50 km/h; 31 mph).^[6][7]

The ships were designed primarily asanti-submarine warfare (ASW) platforms.^[5] Their main anti-submarine sensor was the large bow-mountedAN/SQS-26CX low-frequency scanningsonar, operating as an active sonar at a frequency of about 3.5 kHz and passively at 1.5–4 kHz. The active modes of operation included direct path, to a range of about 20,000 yd (18,000 m), bottom bounce, and convergence zone, which could give ranges of up to about 70,000 yd (64,000 m), 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 12.75 in (324 mm)Mark 32 anti-submarine torpedo tubes. A flight deck and hangar for operating the DASH drone helicopter was fitted aft.^[10][5]

Ten ships were authorized inFiscal 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 fromAvondale 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 lead ship of the class,Knox (FF-1052), waslaid down 5 October 1965, andcommissioned 12 April 1969, at theTodd Shipyards inSeattle, Washington.^[5]

TheUSS Joseph 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 theJoseph Hewes-sub-class^{[citation needed]}.

TheKnox 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 withBagley (FF-1069) in 1979. The modification heightened the bow section, adding bulwarks and spraystrakes 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 13 kHz.^[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 600 ft (180 m). The IVDS could take advantage of water layer temperature conditions in close-range (less than 20,000 yd (18,290 m)) 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 forRIM-7 Sea Sparrow missiles in place of the cancelledSea Mauler short range surface to air missile system, whileDownes (FF-1070) was fitted with a NATO Sea Sparrow (IBPDMS) launcher. It was planned to equip the other 14 ships withSea Chaparral, based on theSidewinder air-to-air missile, but this plan was abandoned.^[16] Most ships were refitted with a 20 mm (0.79 in)Phalanx CIWS aft during the 1980s, replacing the Sea Sparrow launcher.^[13]

In the 1970s, several ships received an interimsurface warfare upgrade allowingStandard ARM anti-radar missiles to be fired from the ships' ASROC launcher.^[16] Later, all ships were modified to launchHarpoon anti-ship missiles from the ASROC launcher, which could carry two Harpoons, with two more carried in the ships' ASROC magazine.^[13]

Five modified ships were built in Spain for theSpanish Navy as theBaleares-class. In these ships, the Sea Sparrow launcher and helicopter facilities were replaced by a Mk 22 launcher for sixteenStandard surface-to-air missiles, giving them a limited area air-defence capability.

In the 1990s, the US agreed to transfer eightKnox-class frigates to theRepublic 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 theChi Yang-class and assigned to the ROCN 168 Patrol Squadron.^[17]

By 2005, the ROCN had removed several systems from the retiredGearing class upgradedWorld War II-vintage destroyers and transferred them to seven of theChi Yang class. These systems include SM-1MRStandard missile in box launchers, H-930 modular combat system, DA-08/2 air/surface search radar, andSTIR-180 illuminating radar. EachChi 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 theChi 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-cellHarpoon/RUR-5 ASROC box launcher, and four Mk46 324 mm (12.8 in) 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 withHsiung Feng III missiles.^[20]

Regarding to the outdated battle system onboard and the aging ships, the class is expected to be replaced by the newly builtTaiwanese Light Frigate.^[21]

• List of naval ship classes in service

• Bauer, K. Jack; Roberts, Stephen S. (1991).Register of Ships of the U.S. Navy, 1775-1990: Major Combatants.Westport, Connecticut: Greenwood Press.ISBN 0-313-26202-0.
• Blackman, Raymond V. B. (ed.)Jane's Fighting Ships 1971–72. London: Sampson Low, Marston & Co., Ltd., 1971.ISBN 0-354-00096-9.
• Friedman, Norman.The Naval Institute Guide to World Naval Weapon Systems 1997–1998. Annapolis, Maryland, USA: Naval Institute Press, 1997.ISBN 1-55750-268-4.
• Friedman, Norman.U.S. Destroyers: An Illustrated Design History. Annapolis, Maryland, USA: Naval Institute Press, 1982.ISBN 0-87021-733-X.
• Gardiner, Robert and Stephen Chumbley (eds.)Conway's All The World's Fighting Ships 1947–1995. Annapolis, Maryland, USA: Naval Institute Press, 1995.ISBN 1-55750-132-7.
• Moore, John. (ed.)Jane's Fighting Ships 1985–86. London: Jane's Yearbooks, 1985.ISBN 0-7106-0814-4.
• Polmar, Norman.The Ships and Aircraft of the U.S. Fleet. Twelfth Edition. London: Arms and Armour Press, 1981.ISBN 0-85368-397-2.
• Prézelin, Bernard and A.D. Baker III (editors).The Naval Institute Guide to Combat Fleets of the World 1990/91:Their Ships, Aircraft and Armament. Annapolis, Maryland, USA: Naval Institute Press, 1990.ISBN 0-87021-250-8.

Wikimedia Commons has media related toKnox class frigates.

• "Knox Class Frigate".Destroyer History Foundation. Archived fromthe original on 25 July 2011.
• "Knox Class Frigate".Global Security.
• "Knox Class Frigate".Federation of American Scientists.
• "Knox Class Frigate Preservation Association".kcfpa.org. Archived fromthe original on 20 March 2015. Retrieved12 May 2015.

• Frigate classes
• Knox-class frigates
• Cold War frigates and destroyer escorts of the United States
• Vietnam War frigates and destroyer escorts of the United States

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