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FF 1052 KNOX class Design

The most successful of the second generation escort vessels built after World War II, the Knox-class patrol frigates incorporate design features and equipment based on the two decades of escort ship development since the DEALEY class was designed in the early 1950s. The DEALEY was the first ocean escort developed to combat high-performance submarines of post-World War II design.

The configurations of KNOX class and subsequent patrol frigates differ in several respects, in part because the latter ships have an emphasis on antiaircraft/anti-surface ship capabilities with some reduction in anti-submarine equipment. By comparison, the KNOX class ships emphasize ASW capabilities. The difference has been necessitated by the changing characteristics of the Soviet naval threat to Allied ocean operations. It was envisioned that the KNOX and other ASW-oriented escorts will operate with the patrol frigates in combined task groups, possibly with other ships such as the planned Sea Control Ship, a small, carrier-like escort ship, that will carry helicopters to help protect Allied merchant convoys, and Navy amphibious and underway replenishment groups.

Forward, on the main deck, is open space for shipboard weapons. On the KNOX class escort ships there is a 5-inch multi-purpose gun and ASROC anti-submarine rocket launcher.

Amidships-in the center portion of the ships-is the superstructure which houses command and control spaces, and some living quarters. The KNOX-class ships have a large "mack" structure that combines mast and stack for boiler exhausts. The mack is topped with various radar, radio, and electronic warfare antennas.

There is a helicopter hangar at the after end of their superstructure. Immediately behind the hangar is a flight deck for helicopter landing and takeoff. On the KNOX-class ships this deck is one level above the main deck. The KNOX-class ships also are being fitted with a short-range or "point defense" anti-aircraft missile launcher on their stern, aft of the flight deck. The KNOX-class ships and PF both have space in their stern for installation of variable depth sonar which can be lowered into the water behind the ships.

Cruising at 22 knots on one boiler, they are fitted with a 5-bladed, fifteen foot wide propeller. They were designed to operate the DASH helicopter, an unmanned ASW platform which never reached production. Instead, from 1972-77 they were modified to accommodate the LAMPS helicopter (SH-2D Seasprite) during which their flight deck and hangar were enlarged. Two ships, FF-1061 and FF-1070 were never modified to accommodate LAMPS.

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.

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Page last modified: 22-07-2011 17:39:28 ZULU