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Knox class frigates were United States Navy

United States Navy

The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...

warships, originally laid down as ocean escorts (formerly called destroyer escort

Destroyer escort

A destroyer escort is the classification for a smaller, lightly armed warship designed to be used to escort convoys of merchant marine ships, primarily of the United States Merchant Marine in World War II. It is employed primarily for anti-submarine warfare, but also provides some protection...

s), but were all redesignated as frigate

Frigate

A frigate is any of several types of warship, the term having been used for ships of various sizes and roles over the last few centuries.In the 17th century, the term was used for any warship built for speed and maneuverability, the description often used being "frigate-built"...

s on 30 June 1975 in the USN 1975 ship reclassification

United States Navy 1975 ship reclassification

The United States Navy reclassified many of its surface vessels in 1975, changing terminology and hull classification symbols for cruisers, frigates, and ocean escorts.- Classification prior to 1975 :...

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

Anti-submarine warfare

Anti-submarine warfare is a branch of naval warfare that uses surface warships, aircraft, or other submarines to find, track and deter, damage or destroy enemy submarines....

escorts. The lead ship of the class was the , laid down

Keel

In boats and ships, keel can refer to either of two parts: a structural element, or a hydrodynamic element. These parts overlap. As the laying down of the keel is the initial step in construction of a ship, in British and American shipbuilding traditions the construction is dated from this event...

October 5, 1965 and commissioned

Ship commissioning

Ship commissioning is the act or ceremony of placing a ship in active service, and may be regarded as a particular application of the general concepts and practices of project commissioning. The term is most commonly applied to the placing of a warship in active duty with its country's military...

April 12, 1969, at Todd Shipyards

Todd Shipyards

Todd Shipyards was an American soccer club based in Brooklyn, New York that was an inaugural member of the American Soccer League. The team was formed when the Todd Shipyard company decided to merge the Brooklyn Robins Dry Dock with Tebo Yacht Basin F.C....

in Seattle. Planned as the follow-on to the twin 5-inch gun armed s and the Tartar

RIM-24 Tartar

The General Dynamics RIM-24 Tartar was a medium-range naval surface-to-air missile , and was among the earliest surface-to-air missiles to equip United States Navy ships...

missile-equipped s, their initial design incorporated the prior classes’ pressure-fired boilers (the design later was changed to conventional 1200 psi (8,273,708.8 Pa) boilers) in a similar-sized hull designed around the massive bow-mounted AN/SQS-26

AN/SQS-26

AN/SQS-26 was a United States Navy surface ship, bow mounted, low frequency, active/passive sonar. At one point it was installed on over 60 US Navy warships from the 1960s to the 1990s and may still be in use on ships transferred to other navies.-Capabilities:...

sonar.

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. They were built in four different shipyards and were originally commissioned as destroyer escorts (DEs) 1052–1097 in 1969–1974, they were redesignated as frigates (FF) on 30 June 1975.

The Knox class was the Navy’s last destroyer-type design with a steam powerplant.

Due to their unequal comparison to destroyer

Destroyer

In naval terminology, a destroyer is a fast and maneuverable yet long-endurance warship intended to escort larger vessels in a fleet, convoy or battle group and defend them against smaller, powerful, short-range attackers. Destroyers, originally called torpedo-boat destroyers in 1892, evolved from...

s 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.”

These ships were retired from the US Navy at the end of the Cold War

Cold War

The Cold War was the continuing state from roughly 1946 to 1991 of political conflict, military tension, proxy wars, and economic competition between the Communist World—primarily the Soviet Union and its satellite states and allies—and the powers of the Western world, primarily the United States...

due to a declining need for an advanced ASW capability. By 1994 all ships of this class had been retired from the US Navy, although some remain in service with foreign nations such as Egypt, Taiwan

Taiwan

Taiwan , also known, especially in the past, as Formosa , is the largest island of the same-named island group of East Asia in the western Pacific Ocean and located off the southeastern coast of mainland China. The island forms over 99% of the current territory of the Republic of China following...

, Thailand

Thailand

Thailand , officially the Kingdom of Thailand , formerly known as Siam , is a country located at the centre of the Indochina peninsula and Southeast Asia. It is bordered to the north by Burma and Laos, to the east by Laos and Cambodia, to the south by the Gulf of Thailand and Malaysia, and to the...

, Turkey

Turkey

Turkey , known officially as the Republic of Turkey , is a Eurasian country located in Western Asia and in East Thrace in Southeastern Europe...

and Mexico

Mexico

The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

Description

These ships were designed primarily as antisubmarine (ASW) platforms. They each had AN/SQS-26 hull-mounted sonar manufactured by General Electric and capable of active echo ranging in the 3.2 kHz range. The active modes of operation included omni-directional, phased directional, bottom bounce, and convergence zone. The battle displays included A and B scans. There was also a "Unit 31" chart readout display capable of long-distance passive detection, often well beyond the ranges capable of the surface search radar. The frigates were also equipped with an AN/AQS-35V Independent Variable Depth Sonar (IVDS) manufactured by EDO Corporation of College Point, NY, operating actively in the 13 kHz range with dual Planned Position Indicator (PPI) battle displays. 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 (182.9 m). The IVDS could take advantage of water layer temperature conditions in close-range (less than 20000 yards (18,288 m) submarine detection, tracking and fire-control.

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), they are driven by a single screw geared turbine developing 35,000 shaft horsepower (26 MW), giving them a speed of 27 knots (53 km/h). The steam plant for these ships consists of two Combustion Engineering

Combustion Engineering

Combustion Engineering was an American engineering firm and leading firm in the development of power systems in the United States with approximately 30,000 employees in about a dozen states at its peak. Headquartered in Stamford, Connecticut, C-E owned over two dozen other companies including...

or Babcock & Wilcox "D" type boilers, each equipped with a high-pressure (supercharger) forced draught air supply system, allowing a plant working pressure of 1,200 psi and 1000 °F superheat. This design allows fast acceleration, crucial while prosecuting a submarine attack. They are equipped with one 5 in (127 mm) 54 caliber Mark 42 gun forward, an ASROC

ASROC

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...

abaft the gun and forward of the bridge. Since they are single purpose platforms their surface defense capability is nominal; however they do mount Harpoon missiles and Mk-44/46 torpedoes. The aft weapons point was originally outfitted with Mk 25 basic point defense missile systems (BPDMS) for launching Sea Sparrow missiles. These were eventually refitted with a 20 millimetre Phalanx CIWS

Phalanx CIWS

The Phalanx CIWS is an anti-ship missile defense system. It is a close-in weapon system and was designed and manufactured by the General Dynamics Corporation, Pomona Division...

. They are equipped with a helicopter hangar aft.

Baleares class

Five modified ships were built in Spain for the Spanish Navy

Spanish Navy

The Spanish Navy is the maritime branch of the Spanish Armed Forces, one of the oldest active naval forces in the world. The Armada is responsible for notable achievements in world history such as the discovery of Americas, the first world circumnavigation, and the discovery of a maritime path...

as the Baleares class frigate

Baleares class frigate

The Baleares class are a group of five frigates built for the Spanish navy in the 1970s. The ships are a modified version of the American Knox class frigates. The key differences are the replacement of the Sea Sparrow PDMS and ASW helicopter facilities by Standard SAM and associated radars...

Chi Yang class

In the 1990s the US agreed to transfer 8 Knox class frigates to the Republic of China Navy

Republic of China Navy

The Republic of China Navy is the maritime branch of the Armed forces of the Republic of China . The ROC Navy's primary mission is to defend ROC territories and the sea lanes that surround Taiwan against a blockade, attack, or possible invasion by forces of the People's Republic of China...

(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.

By 2005 the ROCN had removed several systems from the retired Gearing class upgraded World War II

World War II

World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

-vintage destroyers and transferred them to the Chi Yang class FFG. These systems include SM-1MR Standard missile

Standard missile

Standard Missile can refer to a family of several different American missiles:* RIM-66 Standard , a medium range surface-to-air missile, the successor of the RIM-24 Tartar missile...

in box launchers, H-930 modular combat system, and DA-08 air/surface search radar (with speculations that the Mk 75 76/62 rapid-fire gun might also replace the older Mk 42 127 mm/5" gun in the future). 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.

The anti-submarine capability of the Chi Yang class FFG 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

Harpoon

A harpoon is a long spear-like instrument used in fishing to catch fish or large marine mammals such as whales. It accomplishes this task by impaling the target animal, allowing the fishermen to use a rope or chain attached to the butt of the projectile to catch the animal...

/ASROC