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River Class Destroyer Escort
Type 12 Anti-Submarine frigate

The first four Type 12 River Class Destroyer Escort / Anti-Submarine frigates, Parramatta (III), YARRA, STUART and Derwent, were a modified version of the Royal Navy's Type '12' Whitby and Rothesay Class frigates, which had very good sea-keeping qualities. Swan (III) and Torrens (II) were a derivation of the Royal Navy's Leander Class general purpose frigate, which was itself a development of the Type '12'. `Swan (III) and her sister ship, TORRENS, were the final two River Class DEs constructed for the RAN.

The decision to acquire a new generation of frigates was announced in August 1950. The six new anti-submarine frigates were to be a modified version of the Royal Navy's Type '12' Rothesay Class frigates, but with improvements in habitability to meet specific Royal Australian Navy (RAN) needs.

In the event only four hulls were finally approved, with an armament of one twin 4.5 inch turret, one twin 40 mm Bofors Mk 5, two Limbo anti-submarine mortars and twelve 21-inch torpedo tubes. The ships also introduced a number of new capabilities, including a hull-mounted medium range sonar, and in the case of Derwent and Stuart, a Type 199 variable depth sonar that could be lowered below the surface temperature layer.

The 4.5 inch twin turret was designed as dual purpose, having both anti-surface and anti-aircraft capabilities. A crew of six was carried in the turret for loading and operation, and a further 18 below for supply of shell and cordite from the magazines to the gun bay and up to the turret.

Derwent, with her consort, Stuart, were the second pair of Type 12's to be ordered in 1958, but to a slightly modified design. Both ships featured a flushed hull on the portside aft, to accommodate a control room and deck space for their variable depth sonar. From Navy News, dated May 15 1964, "Derwent also is prepared for atomic warfare and has a 'wetting-down' device to cope with nuclear fall-out. An elaborately equipped operations room is the hub of the frigate. The ship can be controlled from this compartment, where a mass of dials and screens gives the Commanding Officer all available technical information."

The River Class Destroyer Escort (DE) were 112.8 meters in length, 12.5 meters across the beam, 2,750 tonnes displacement and carried a crew of 250. The hull was designed in 1947, the internal configuration in 1953 and construction of the Class began in 1954. The River Class Destroyer Escorts, the Guided Missile Destroyers (DDGs) and the Oberon Class Submarines were the oldest warships in the RAN at the end of the Cold War. At the time they were launched, ships' companies were all male and crew comfort was not a high priority. The design of a modern warship is a series of compromisesbetween con?icting requirements for space, weight and power often to the detriment of aspects of daily life, such as privacy, which many civilians take for granted. Personnel who served on these vessels must accept and be prepared to adapt to these conditions.

The Type 12 anti-submarine frigate HMAS Parramatta, the first of six River Class Destroyer Escorts, was constructed for the Royal Australian Navy at Cockatoo Island Dockyard as ship numbers 199. It was laid down on 3 January 1957, launched on 31 January 1959, and commissioned on 4 July 1961. Its overall length was 370 feet, and displacement was 2 100 tons. HMAS Parramatta was the first of the Type 12 frigates built in Australia. The frigates were later reclassified destroyer escorts. Main machinery was also manufactured for HMAS Parramatta, Stuart, Yarra and Derwent. This work was allocated ship/job number 202.

PARRAMATTA completed several overseas deployments and spent many months on the Australia station. One of her early career highlights was the escort of the Royal Yacht BRITANNIA during the visit of Her Majesty the Queen in 1963. PARRAMATTA had active service during the Vietnam War, escorting the fast troop transport HMAS Sydney (III) to Vung Tau, Vietnam, in 1965, 1968 and 1971. She also served on patrol duties between 1964 and 1966 during the Indonesian Confrontation. In July 1976 PARRAMATTA was diverted to the Indonesian island of Bali to provide humanitarian relief following an earthquake which killed over 500 Balinese and injured another 3,000.

HMAS PARRAMATTA was decommissioned on 3 June 1977 for modernisation and refit at Williamstown Naval Dockyard, and on completion recommissioned on 26 August 1981. Highlights of her second commission included a rare visit to the Peoples Republic of China in 1986 and participation in 1986 Royal Australian Navy 75th Anniversary Naval Review and the Bicentennial Naval Salute in 1988. PARRAMATTA was decommissioned on 11 January 1991 as the River Class Destroyer Escorts were replaced by the Adelaide Class Guided Missile Frigates. She was sold to a Pakistani company and towed from Australia October 1991 to be broken up.

The third of three Type 12 anti-submarine frigates to be built at Williamstown, Derwent was launched on 17 April 1961. "I name this ship, Derwent, I congratulate all those who have so faithfully and skillfully constructed her. May she be a valuable addition to the Royal Australian Navy, and may God's protecting care be over all who sail in her." With these words by Lady Burrell, wife of the First Member of the Naval Board, Admiral Burrell, Derwent was officially named and launched. She was the fourth warship to bear the name, with the previous three having served in the Royal Navy. After decommissioning, Derwent continued to serve the nation when she was used as the platform for the Ship Survivability Enhancement Program (SSEP). The SSEP involved a series of fire, smoke, weapons effects and electronic experiments, with the data being used to enhance the combat survivability of ships and their crews to a range of weapons and associated threat effects.

The Type 12 anti-submarine frigate HMAS Stuart was constructed for the Royal Australian Navy at Cockatoo Island Dockyard as ship number 200. It was laid down on 20 March 1959, launched on 8 April 1961, and completed on 27 June 1963. It has the same specifications as for HMAS Parramatta (III). HMAS Stuart was the first vessel fitted with the IKARA anti-submarine guided missile which had been developed in Australia.

The Type 12 destroyer escort HMAS Torrens was constructed for the Royal Australian Navy at Cockatoo Island Dockyard as ship number 224; its related ship HMAS Swan was constructed at Williamstown Dockyard. It was laid down on 16 August 1965, launched on 28 September 1968 and completed on 18 January 1971. Overall length was 372 feet and displacement was 2 750 tons. HMAS Torrens was to be the last combat warship constructed in Australia for the Navy for twenty-one years. The turbines for both the HMAS Torrens and HMAS Swan were built at Cockatoo Island Dockyard, as ship/job number 223, although the boilers were built by Vickers in England.

HMAS Swan (III) was laid down at HMA Naval Dockyard, Williamstown, Victoria, on 18 August 1965, and was the last River Class Destroyer Escort to be constructed in that dockyard. The ship was named after the Swan River in Perth, Western Australia. Swan (III) was the third Royal Australian Navy ship to bear that name, but the 25 th 'Royal Swan', the first twenty-two having served in the Royal Navy. Swan (III), especially in her initial role as a front line fleet ASW unit, had a very busy and varied RAN career, which emphasized her versatility. Swan (III) soon earned the nickname "Fluffy Duck", or "Duck", a name she retained throughout her career.

HMAS Derwent was initially F22 in 1964. This was later changed to DE22, with the prefix standing for Destroyer Escort. On 1 January 1969, the Royal Australian Navy adopted the numbering practice used by the US, Canadian and Pakistan Navies, removing the pennant number letter prefix from its ships' hulls. Derwent's pennant number thus became 49.

The 1972 Defence Review noted that "The RAN and the RAAF are well practised in anti-submarine warfare, HMAS Melbourne, with Tracker aircraft and Wessex helicopters embarked, and the antisubmarine warfare sensors and weapons (which include the Australian Ikara missile) in our six River class destroyers, and the two squadrons of Long Range Maritime Patrol aircraft referred to earlier, are primarily tasked to provide defence against submarine attack.... By the early 1980s some of the RAN's operational destroyers will reach the end of their useful lives. The possibility of local design and construction of replacement ships has been intensively studied in the Departments of Defence and the Navy and a decision will be made in the light of a mid-year review of a total defence programme for the next five years. Some weapon systems and sensors in the destroyers will reach the end of life in the 1970s from age, obsolescence, or the closing down of overseas production lines. Decisions will be required whether to modernise the first four older River class destroyer escorts and the missile, sonar and combat data systems of the three guided missile destroyers."

On December 1974, Mr. Lance Barnard, the Minister for Defence, announced that approval had been given for the modernization and extensive refitting of the RAN's River Class Destroyer Escorts, including gunnery, anti-submarine weapons, hull and machinery, with the first modernization commencing in the second half of 1976 and the last finishing late in 1980.

Australia's defence scientists developed an advanced medium-range active sonar system named Mulloka. This grew from a study begun in 1971 by scientists at the Advanced Engineering Laboratory and the Royal Australian Naval Research Laboratory, Sydney. The study sought to determine whether the British-designed 177M sonar designed to operate in North Atlantic waters and fitted to the Navy's 'River' class destroyers, could be re-engineered to be more suitable for Australian waters. It quickly became obvious that a system suitable for Australian conditions required a radical departure from the technology used in the British system. The decision to proceed with Mulloka was taken in early 1972 and work began on constructing a prototype to fit to one of the 'River' class destroyer escorts. This was accomplished near the end of 1974 and sea trials began in March 1975. The trials were only partially successful. The Mulloka system demonstrated superior performance to existing medium-range sonars, but water seeped into the system and corroded components.

Modifications and trials continued until the Navy finally accepted the system on 17 August 1979 when it was fitted to HMAS Yarra. HMAS YARRA, oldest of the RAN's River Class destroyer escorts, had double-reason to celebrate in 1979 after completing the past five years as "trials ship" for the new Australian-designed and built MULLOKA sonar system. She successfully completed her first full workup and bottle problem in five years, and 27 July 27 was her 18th birthday. She had steamed 525,085 miles in 37,098 hours. EMI Electronics (Australia) won the contract for the manufacture of the system, with Honeywell Marine Systems Division of Seattle, United States, winning the contract for design and development of the transducer array. Ultimately, the Mulloka system was fitted to the 'River' class and the two Australian-built guided missile frigates.

Signed in 1989, the contract to deliver eight ANZAC frigates to Australia and two to New Zealand was the largest Australian Defence contract ever awarded. The contract was initially agreed on to supply the Navy with eight tier-two warships to replace the six ageing River class Destroyer Escorts (DEs). The ANZAC frigates successfully replaced the DEs and provided the Surface Combatant Force with a significant advancement in capability.

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