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 frigate 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.
These ships were designed primarily as antisubmarine warfare (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 (180 m). The IVDS could take advantage of water layer temperature conditions in close-range (less than 20,000 yards (18,000 m) submarine detection, tracking and fire-control. In practice, the IVDS was the only ASW detection system of any tactical value in a ship of this limited speed, and the inability to successfully engage a target once acquired was well known both within the USN, and outside of it.
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 (50 km/h). 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, allowing a plant working pressure of 1,200 psi and 1000 °F superheat. They were equipped with one 5 in (127 mm) 54 caliber Mark 42 gun forward, an ASROC abaft the gun and forward of the bridge. Since they were single purpose platforms their surface defense capability was nominal; however they did 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. They were equipped with a helicopter hangar aft.
| 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 Sonar AN/SQR-18 Towed array sonar system AN/SPG-53 Mk68 Gun Fire Control System |
| 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 |
