Type system of the Royal Navy
The Type system is a classification system used by the British Royal Navy to classify surface escorts by function. The system evolved in the early 1950s, when the Royal Navy was experimenting with building single-purpose escort vessels with specific roles in light of experience gained in World War II. The following Type numbers are known to have been used, or proposed;
Types 11-40, Anti-Submarine Escorts 
- Type 11 : Diesel powered anti-submarine frigate based on hull of Type 41 / 61. Not built.
- Type 12 Whitby : Steam powered, high-speed first-rate anti-submarine frigate.
- Type 12M Rothesay : Improved Type 12 design.
- Type 12I Leander : Modified Type 12, general purpose frigate.
- Type 14 Blackwood : Steam powered, high-speed, second rate anti-submarine frigate.
- Type 15 : High-speed anti submarine frigate, full conversion of wartime destroyer hulls.
- Type 16 : High-speed anti submarine frigate, limited conversion of wartime destroyer hulls.
- Type 17 : Third rate anti-submarine frigate, analogous to wartime corvettes. Not built.
- Type 18 : High-speed anti submarine frigate, intermediate conversion of wartime destroyer hulls. Not built.
- Type 19 : Very high speed (42 knot) gas turbine powered anti-submarine frigate. Not built.
- Type 21 Amazon: General purpose, gas-turbine powered commercially designed frigate.
- Type 22 Broadsword : Large, gas-turbine powered, anti-submarine frigates.
- Type 23 Duke : Gas-turbine and diesel powered, anti-submarine frigates. Smaller and less expensive than the Type 22, with similar capabilities.
- Type 24 : Cheap frigate design intended for export. In RN service would have served as a towed array ASW ship. Not built.
- Type 25 : Design intended to have almost the capability of a Type 22 but at only three-quarters of the cost. Much of the thinking, including the diesel-electric machinery, went into the Type 23. Not built.
- Type 26 : Future Surface Combatant (C1 variant) - referred to by First Sea Lord Sir Mark Stanhope in his speech to the International Institute for Strategic Studies in March 2010.
Types 41-60, Anti-Aircraft Escorts 
- Type 41 Leopard : Diesel powered anti-aircraft frigate built on common hull with Type 61.
- Type 42(i) East coast frigate : High speed coastal escort. Not built
- Type 42(ii) Sheffield : Gas-turbine powered, fleet area-defence anti-aircraft destroyer.
- Type 43 : Large gas-turbine powered, "double-ended", fleet area-defence anti-aircraft destroyer. Not built.
- Type 44: A smaller "single-ended" version of the Type 43 intended as a cheaper alternative. Not built.
- Type 45 Daring : Fleet area-defence anti-aircraft destroyer to replace Type 44 project.
Types 61-80, Aircraft Direction Escorts 
- Type 61 Salisbury : Diesel powered aircraft-direction frigate built on common hull with Type 41.
- Type 62 M class : High-speed aircraft-direction frigate, full conversion of wartime destroyer hulls. Not built.
Types 81-99, General Purpose Escorts 
- Type 81 Tribal : Single-shaft steam / gas-turbine powered general purpose "colonial" frigates.
- Type 82 Bristol : Large steam / gas-turbine powered fleet anti-aircraft and anti-submarine destroyer. 1 built of 4 initially planned
See also 
- Naming conventions for destroyers of the Royal Navy - describing the various conventions used to name destroyer classes of the Royal Navy since 1913.
- Rating system of the Royal Navy - the system used to classify ships of the line during the age of sail. The "rating" system was briefly revived to further classify anti-submarine escorts during the 1950s.