Knox-class frigate

Knox-class frigate USS Robert E. Peary (FF-1073) and the skyline of San 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 Navy
Preceded by:	Garcia-class frigate / Brooke-class frigate
Succeeded by:	Oliver Hazard Perry-class frigate
Built:	1965–1974
In commission:	1969–1994 (USN)
Completed:	46
Retired:	46 (USN)
General characteristics
Type:	Frigate
Displacement:	4,260 tons (full load)
Length:	438 ft (134 m)
Beam:	46 ft 9 in (14.25 m)
Draft:	24 ft 9 in (7.54 m)
Propulsion:	1 shaft, one Westinghouse steam turbine, 2 V2M boilers. total 35,000 shp (maximum)
Speed:	over 27 knots (50 km/h)
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/passive Sonar AN/SQR-18 Towed array sonar system AN/SPG-53 Mk68 Gun Fire Control System
Electronic warfare & decoys:	As Built AN/WLR-1C – AN/ULQ-6C and AN/SLA-15 (Comprising AN/SLQ-26 System) AN/SLQ-32 Electronics Warfare System and Mark 36 SRBOC
Armament:	one Mk-16 8 cell missile launcher for ASROC and Harpoon missiles one Mk-42 5-inch/54 caliber gun Mark 46 torpedoes from two dual tube launchers) RIM-7 Sea Sparrow (BPDMS) or Phalanx CIWS
Aircraft carried:	One SH-2 Seasprite (LAMPS I) helicopter

Knox-class frigates were United States Navy warships, originally laid down as ocean escorts (formerly called destroyer escorts), but were all redesignated as frigates on 30 June 1975 in the USN 1975 ship reclassification and their hull designation changed from DE to FF.

A sub-class of the Knox class was built, commonly referred to as the Hewes class. The primary differences were slightly different arrangement of the "Officer's Country" staterooms with additional staterooms in the 01 level instead of the open deck between the boat decks. The stateroom on the port side under the bridge was designated as a "flag" stateroom, with the additional staterooms for flag staff when serving as a flagship.

History

The 46 ships of the Knox class were the largest, last and most numerous of the US Navy’s second-generation ASW escorts. The lead ship of the class was USS Knox (FF-1052), laid down 5 October 1965 and commissioned on 12 April 1969, at Todd Shipyards in Seattle.^[1] Planned as the follow-on to the twin 5-inch gun armed Garcia-class frigates and the Tartar missile-equipped Brooke-class frigates, their initial design incorporated the prior classes' pressure-fired boilers in a similar-sized hull designed around the massive bow-mounted AN/SQS-26 sonar, with increased endurance and reduced crew size. Anti-submarine armament was to consist of ASROC anti submarine missiles together with the DASH drone helicopter, while defensive armament was to be the RIM-46 Sea Mauler short range anti-aircraft missile backed up by a single 5-inch gun.^[2]

Drawing of a Knox-class frigate as built.

The design soon ran into problems, with the US Navy deciding to switch to conventional 1,200 psi (8,300 kPa) boilers, requiring a redesign, with the ships becoming longer and heavier in order to accommodate the less compact power plants. In 1965, Sea Mauler was cancelled, leaving the ships to complete without any surface-to-air missile system.^[3][1]

Ten ships were authorized in FY 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.^[3] These ships were built on a production line, with prefabricated modules being assembled upside down, welded together and then rotated into an upright position.^[4] They were originally commissioned as destroyer escorts (DEs) 1052–1097 in 1969–1974,^[1] but were redesignated as frigates (FF) on 30 June 1975.^[5]

Bow modifications including bulwark and horizontal spray strake on USS Bowen (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. In 1979, the class began to receive "hurricane bows" beginning with USS Bagley (FF-1069). The modification heightened the bow section, adding bulwarks and spray strakes to prevent burrowing into on-coming seas and better protect the forecastle armament.^[6]

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 (large size with low speed and a single screw and 5 inch gun), they became known to a generation of destroyermen as “McNamara’s Folly.”^[7]

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 need for ships with a more advanced ASW 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.

Description

Aerial view of Knox-class frigate USS McCandless (FF-1084)

Overhead view of Knox-class frigate USS Fanning (FF-1076)

The Knox class are 438 feet (133.5 m) long overall and 415 feet (126.5 m) at the waterline, with a beam of 46 feet 9 inches (14.2 m) and a draft of 24 feet 9 inches (7.5 m). At 4,200 metric tons (4,130 tons), with a length of 438 feet (133.5 metres) and a beam of 47 feet (14.3 m). 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 1,200 pounds per square inch (8,300 kPa) and 1,000 °F (538 °C) superheat and rated at 35,000 shaft horsepower (26,000 kW) driving a single screw. This gives them a speed of 27 knots (50 km/h).^[8][9]

These ships were designed primarily as antisubmarine warfare (ASW) platforms.^[1] As built, 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 3.5 kHz and passively at 1.5–4 kHz. The active modes of operation included direct path, to a range of about 20,000 yards (18,000 m), bottom bounce, and convergence zone, which could give ranges of up to about 70,000 yards (64,000 m), well outside the capability of ASROC, and requiring the use of a helicopter to exploit.^[1][10][11] 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.^[1][8][9] 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 feet (180 m). The IVDS could take advantage of water layer temperature conditions in close-range (less than 20,000 yards (18,290 m) submarine detection, tracking and fire-control. The AN/SQS-35 "fish" was later modified to tow an AN/SQR-18A TACTASS passive towed array sonar, the active sonar transponder being removed from the fish as part of the modification.^[12][13]

As built, they were equipped with one 5 in (127 mm) 54 caliber Mark 42 gun forward, an eight round ASROC launcher (with 16 missiles carried) abaft the gun and forward of the bridge, with four fixed 12.75 in (324 mm) Mark 32 anti-submarine torpedo tubes. A helicopter deck and hangar for operating the DASH drone helicopter was fitted aft.^[4][1] The helicopter facilities were expanded in the 1970s to accommodate the larger, manned, Kaman SH-2D Seasprite LAMP helicopter.^[14] While as built, anti-aircraft capabilities were limited to the 5-inch gun, it was planned to refit the ships with a short range surface to air missile system to replace the cancelled Sea Mauler. 31 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, while DE-1070 was fitted with an improved NATO Sea Sparrow 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.^[15] All ships were refitted with a 20 millimetre Phalanx CIWS aft during the 1980s, replacing the Sea Sparrow launcher where fitted.^[12] Surface warfare weaponry was at first similarly limited to the gun, with several ships receiving an interim upgrade allowing Standard ARM anti-radar missiles to be fired from the ships' ASROC launcher in the 1970s.^[15] 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.^[12]

Baleares class

Five modified ships were built in Spain for the Spanish Navy as the Baleares-class frigates.

Chi Yang class

Chi Yang class FFG-932

In the 1990s the US agreed to transfer 8 Knox-class frigates to the Republic of China Navy (ROCN). The ROCN planned to upgrade these ships with new air defense, anti-submarine, and electronic warfare capabilities, including new radar, towed active sonar, CIWS guns, VL air defense missiles, active/passive electronic warfare systems, etc. However, due to budget considerations and the acquisition of newer ships, only a few upgrades were implemented. These frigates were renamed the Chi Yang class and assigned to the ROCN 168 Patrol Squadron.^[16]

By 2005 the ROCN had removed several systems from the retired Gearing class upgraded World War II-vintage destroyers and transferred them to the Chi Yang class. These systems include SM-1MR Standard missile in box launchers, H-930 modular combat system, and DA-08 air/surface search 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.^[17]

The anti-submarine 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/ASROC box launcher, and 4 x Mk46 324 mm torpedoes. While on ASW patrol, the frigate will carry 2 x Harpoon SSMs and 6 x ASROCs in its Mk-16 box launcher.^[18]

These ships will be upgraded with Hsiung Feng III missiles.^[19]

Units

References

Citations

References

• 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.

External links

Wikimedia Commons has media related to Knox class frigates.

• "Knox Class Frigate". Destroyer History Foundation. Archived from the original on 25 July 2011. 
• "Knox Class Frigate". Global Security. 
• "Knox Class Frigate". Federation of American Scientists. 
• "Knox Class Frigate Preservation Association". kcfpa.org.