The Leander-class, or Type 12I (Improved) frigates,Purvis, M.K., 'Post War RN Frigate and Guided Missile Destroyer Design 1944–1969', Transactions, Royal Institution of Naval Architects (RINA), 1974Postwar Frigates comprising twenty-six vessels, was among the most numerous and long-lived classes of frigate in the Royal Navy's modern history. The class was built in three batches between 1959 and 1973. It had an unusually high public profile, due to the popular BBC television drama series Warship. The Leander silhouette became synonymous with the Royal Navy through the 1960s until the 1980s.
The Leander design or derivatives of it were built for other navies: Royal New Zealand Navy as the Leander class Chilean Navy: Royal Australian Navy: Indian Navy: Royal Netherlands Navy:
Design The policy adopted by the Royal Navy during the 1950s of acquiring separate types of frigates designed for specialised roles (i.e. anti-submarine, anti-aircraft and aircraft direction) had proved unsatisfactory. Although the designs themselves had proved successful, the lack of standardisation between the different classes led to increased costs during construction and also in maintenance once the ships became operational. Furthermore, it was not always possible to have the ships with the required capabilities available for a specific task.
The first move towards creating a truly general-purpose frigate came with the Type 81 Tribal class which was initially ordered in 1956. The 24-knot speed of the Tribals was considered the maximum possible for tracking submarines with the new medium-range sonars,N. Friedman. British Destroyers and Frigates. The Second World War 7 After. 2006. Chatham, p. 243 , entering service. The type 81 gas turbine saw the frigates underway quickly, without taking hours flashing up steam turbines, and the provision of a helicopter for long-range attack was considered essential in the nuclear age. These ships were mainly intended to operate in the tropics but lacked the speed and armament required for the priority fleet carrier escort role East of Suez, where fast radar picket capability was important, as much as anti-submarine capability. So the new frigates would combine the roles of the T12 and T61. The fully air-conditioned Royal New Zealand Navy Rothesay class variant, , which gave all the crew a bunk and cafeteria messingD K Brown. A Century of Naval construction. Conway Maritime. 1983. London pp. 203–207, and a RNZN commissioned design study for a more fully capable Type 12 frigate, which also assessed whether the Type 12 could carry 2 of the larger Wessex AS helicopters, was used as the basis of the RN Leander Improved Type 12 design..R. Gardiner. Conway's All the World's Fighting Ships. Part 1. Western powers. Conway Maritime. London.1983, pp. 164–165.
On 7 March 1960, the Civil Lord of the Admiralty C. Ian Orr-Ewing stated that the "Type 12 Whitby-class anti-submarine frigates are proving particularly successful ... and we have decided to exploit their good qualities in an improved and more versatile ship. This improved Type 12 will be known as the Leander class. The hull and steam turbine machinery will be substantially the same as for the Whitbys. The main new features planned are a long-range air warning radar, the Seacat anti-aircraft guided missile, improved anti-submarine detection equipment and a light-weight helicopter armed with homing torpedoes. We shall also introduce air conditioning and better living conditions."Hansard HC Deb 07 March 1960 vol 619 cc39-200 Navy Estimates 1960–61, statement by the Civil Lord of the Admiralty (Mr C. Ian Orr-Ewing), 7 March 1960. The 1963 edition of Jane's Fighting Ships described it as a "mainly anti-submarine but flexible and all-purpose type".
The difference between the Leanders (Type 12I) and the Whitbys (Type 12) was most obviously that the stepped quarterdeck of the Type 12 had been done away with, resulting in a flush deck, with the exception of the raised forecastle. The superstructure had been combined into a single block amidships and a new bridge design gave improved visibility. A hangar and flight deck were provided aft for the Westland Wasp light anti-submarine helicopter, which was still at the prototype stage when the first ships were ordered. The ship was air conditioned throughout and there were no portholes in order to improve nuclear, biological and chemical defence. The ships were all given names which had previously been given to Royal Navy cruisers, mostly of characters from classical mythology,Marriott, p. 82 the exceptions being Cleopatra and Sirius.
The Y160 boiler variant used on the Batch 3 Leanders (such as ) also incorporated steam atomisation equipment on the fuel supply so the diesel fuel entering the boilers via the three main burners was atomised into a fine spray for better flame efficiency. Some ships with Y100 Boilers were also converted to steam atomisation, HMS Cleopatra being one of them. The superheat temperature of the Y160 was controlled manually by the boiler room petty officer of the watch between and the steam supplied to the main turbines was at a pressure of . The Leander-class frigates did have Babcock & Wilcox boilers but of a more conventional two-drum design, one water drum and one steam drum, much like a Yarrow boiler without the second water drum. The water drum was offset to one side and below the furnace and steam drum. The two boilers fitted were 'handed' with the water drum inboard on both. Many Leanders had six-burner furnaces (known as Five and a Half Boilers) and the output was varied by altering the number of burners in use.
Construction programme Royal NavyPennantName(a) Hull builder(b) Main machinery manufacturersLaid downLaunchedAccepted into serviceCommissionedEstimated building cost"Unit cost, i.e. excluding cost of certain items (e.g. aircraft, First Outfits)."Text from Defences EstimatesConversion groupBatch 1 Leander Y-100 machinery F109 Leander (a) & (b) Harland & Wolff Ltd, Belfast.Navy Estimates, 1963–64, page 71, Table 3 (Programme): List and particulars of new ships which have been accepted or are expected to be accepted into HM service during the Financial Year ended 31 March 1963 10 April 1959 Blackman, Raymond VB, Jane's Fighting Ships, 1963–64, pub Sampson Low Marston & Co Ltd, 1963, page 270. 28 June 1961 March 1963 27 March 1963 £4,630,000 Ikara F104 Dido (a) & (b) Yarrow & Co Ltd, Glasgow.Defence Estimates, 1964–65, page 73, Table 3 (Programme): List and particulars of new ships which have been accepted or are expected to be accepted into HM service during the Financial Year ended 31 March 1964 2 December 1959 22 December 1961 September 1963 18 September 1963 £4,600,000 Ikara F127 Penelope (a) Vickers-Armstrongs (Shipbuilders) Ltd, Newcastle (b) Vickers-Armstrongs (Engineers) Ltd, Barrow-in-Furness 14 March 1961 17 August 1962 November 1963 31 October 1963 £4,600,000 Exocet/Seacat F114 Ajax (a) & (b) Cammell Laird & Co (Shipbuilders and Engineers) Ltd, Birkenhead. 19 October 1959 16 August 1962 December 1963 10 December 1963 £4,800,000 Ikara F10 Aurora (a) & (b) John Brown & Co Ltd, Clydebank 1 June 1961 28 November 1962 April 1964 9 April 1964 Moore, John E, Jane's Fighting Ships, 1975–76, pub Macdonald and Jane's, 1975, pages 35405. £4,650,000 Ikara F18 Galatea (a) Swan, Hunter & Wigham Richardson Ltd, Wallsend-on-Tyne (b) The Wallsend Slipway & Engineering Co Ltd, Wallsend-on-Tyne (steam turbines) (b) Parsons Marine Turbines Co Ltd, Wallsend-on-Tyne (gearing). 29 December 1961 23 May 1963 April 1964 25 April 1964 £4,500,000 Ikara F15 Euryalus (a) Scotts Shipbuilding & Engineering Co Ltd, Greenock (b) Scotts Shipbuilding & Engineering Co Ltd (steam turbines) (b) Fairfield Shipbuilding & Engineering Co Ltd, Glasgow (gearing).Defence Estimates, 1965–66, page 75, Table 3 (Programme): List and particulars of new ships which have been accepted or are expected to be accepted into HM service during the Financial Year ended 31 March 1965 2 November 1961 6 June 1963 September 1964 16 September 1964 £4,350,000 Ikara F39 Naiad (a) Yarrow & Co Ltd, Glasgow (b) Yarrow & Co Ltd, Glasgow (steam turbines) (b) Parsons Marine Turbines Co Ltd, Wallsend-on-Tyne (gearing). 30 October 1962 4 November 1963 March 1965 15 March 1965 £4,750,000 Ikara F38 Arethusa (a) JS White & Co Ltd, Cowes, Isle of Wight (b) JS White & Co Ltd, Cowes, Isle of Wight (steam turbines) (b) Parsons Marine Turbines Co Ltd, Wallsend-on-Tyne (gearing). 7 September 1962 Jane's Fighting Ships 1963–64 edition said that Arethus was laid down on 17 September 1964, however the 1975–76 edition says that she was laid down on 7 September 1964. 5 November 1963 November 1965 24 November 1965 £4,850,000 Ikara F28 Cleopatra (a) HM Dockyard, Devonport (b) Cammell Laird & Co (Shipbuilders & Engineers) Ltd, Birkenhead (turbines) (b) John Brown & Co Ltd, Clydebank (gearing).Defence Estimates, 1966–67, page 72, Table 3 (Programme): List and particulars of new ships which have been accepted or are expected to be accepted into HM service during the Financial Year ended 31 March 1966 19 June 1963 25 March 1964 February 1966 4 January 1966 £5,300,000 Exocet/SeacatBatch 2 Leander Y-136 machinery F42 Phoebe (a) Alexander Stephen & Sons Ltd, Linthouse, Glasgow (b) Alexander Stephen & Sons Ltd, Linthouse, Glasgow (steam turbines) (b) David Brown & Co Ltd, Huddersfield (gearing). 3 June 1963 8 July 1964 April 1966 15 April 1966 £4,750,000 Exocet/Seacat F45 Minerva (a) Vickers Ltd, Shipbuilding Group, Newcastle (b) Alexander Stephen & Sons Ltd, Linthouse, Glasgow (steam turbines) (b) David Brown & Co Ltd, Huddersfield (gearing). 26 July 1963 19 December 1964 May 1966 14 May 1966 £4,700,000 Exocet/Seacat F40 Sirius (a) HM Dockyard, Portsmouth (b) JS White & Co Ltd, Cowes, Isle of Wight (turbines) (b) David Brown & Co Ltd, Huddersfield (gearing).Defence Estimates, 1967–68, page 75, Table 3 (Programme): List and particulars of new ships which have been accepted or are expected to be accepted into HM service during the Financial Year ended 31 March 1967 9 August 1963 22 September 1964 June 1966 15 June 1966 £5,600,000 Exocet/Seacat F52 Juno (a) JI Thornycroft Ltd, Southampton (b) JI Thornycroft Ltd, Southampton (steam turbines) (b) David Brown & Co Ltd, Huddersfield (gearing) 16 July 1964 24 November 1965 July 1967 18 July 1967 £5,020,000 Training F56 Argonaut (a) Hawthorn Leslie, Hebburn (b) JS White & Co Ltd, Cowes, Isle of Wight (steam turbines) (b) David Brown & Co Ltd, Huddersfield (gearing). 27 November 1964 8 February 1966 September 1967 17 August 1967 £5,000,000 Exocet/Seacat F47 Danae (a) HM Dockyard, Devonport (b) JS White & Co Ltd, Cowes, Isle of Wight (steam turbines) (b) Fairfields (Glasgow) Ltd (gearing).Defence Estimates, 1968–69, page 75, Table 3 (Programme): List and particulars of new ships which have been accepted or are expected to be accepted into HM service during the Financial Year ended 31 March 1968Note that the costs quoted in the Defence Estimates are slightly different from costs quoted by the Minister of State (Mr. John Morris) - see Hansard HC Deb 26 March 1969 vol 780 c302W Question to the Secretary of State for Defence how the cost of Leander-class frigates built in the Royal Dockyards compares with that of those built in commercial shipyards.