page_title: Leander-class frigate
section_title: Design
hierarchical_section_title: Leander-class frigate / Design
caption_attribution_description: English: Aerial view of Leander-class frigate HMS Penelope (F127), 18 May 1970 (IWM HU 129947)
context_page_description: The Leander-class, or Type 12I 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: Condell class
  Royal Australian Navy: River class
  Indian Navy: Nilgiri class
  Royal Netherlands Navy: Van Speijk class
context_section_description: 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, 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 were 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, HMNZS Otago, which gave all the crew a bunk and cafeteria messing 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. 
  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."  The 1963 edition of Jane's Fighting Ships described it as a "mainly anti-submarine but flexible and all purpose type".
  The Leander class have the same hull and substantially the same steam turbine machinery as the Whitby class, but are a revised and advanced design and will fulfil a composite anti-submarine, anti-aircraft and air direction role. The 40mm guns will eventually be replaced by Seacat ship-to-air launchers.  The ships are equipped with VDS (Variable Depth Sonar), formerly known as dipping asdic.
  — Jane's Fighting Ships, 
  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 of characters from classical mythology which had previously been given to Royal Navy cruisers.
  The Y160 boiler variant used on the Batch 3 Leanders (such as Jupiter) 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 o
caption: Aerial view of HMS Penelope in 1970, showing the original layout of the class before conversion.
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