Tribal-class frigate

The Type 81, or Tribal class, was a class of seven general-purpose frigates for the Royal Navy designed during the 1950s that served throughout the 1960s and 1970s with limited service during the 1980s.

History
The Tribals were designed during the 1950s as a response to the increasing cost of single-role vessels such as the Type 14s. They were first such 'multi role' vessels for the Royal Navy. They were designed specifically with colonial 'gunboat' duties in mind, particularly in the Middle East. They were therefore designed to be self-contained warships with weapon and sensor systems to cover many possible engagements, air conditioning to allow extended tropical deployment and such 'modern' habitability features as all bunk accommodation (as opposed to hammocks). The fitting of gas turbine boost engines was specifically intended to allow the frigates to almostly instantly leave ports and naval bases in the event of nuclear war, rather than have to spend four to six hours to flash up the steam boilers. The G6 gas turbine proved reliable and was generally used to leave port during the frigates career and paved the way for gas turbine propulsion to become universal in the RN within 30 years.

Design
They were the first class of the Royal Navy to be designed from the start to operate a helicopter and the first small escorts to carry a long-range air search radar, the Type 965 with a single 'rake' AKE-1 antenna. They were armed with two 4.5 inch Mark 5 main guns salvaged from scrapped Second World War destroyers. Although these mountings were refurbished with Remote Power Control (RPC) operation, they still required manual loading on an exposed mounting. From the outset they were designed to carry the new GWS-20 Sea Cat anti-aircraft missile system but all except Zulu initially shipped single Mark 7 Bofors guns in lieu. In the event, budget restraints led to only Ashanti, Gurkha, Eskimo and Zulu being so fitted.

The Tribals were the first modern RN ships designed to use a combination of power sources, a feature which had been trialled with limited success in the 1930s in the minelayer HMS Adventure. An additive mix of steam and gas turbine called "COmbined Steam and Gas" COSAG was used. This gave the rapid start-up and acceleration of a gas turbine engine coupled with the cruising efficiency and reliability of the steam turbine. They would cruise on the steam plant and use both systems driving the same shaft for a high-speed "boost". They suffered however from being single-shaft vessels which severely limited manoeuvrability, acceleration and deceleration. The single screw proved significantly limiting when they were used in the 1970s Cod Wars in terms of manoeuvering in ramming manoeuvers, for and against, Icelandic coast guard cutters. The cramped awkward nature of the helicopter pad and handling provision was also exposed in the 1976 Cod war and was a major reason that some Rothesays were given further refits in preference to the Tribals and maintained in higher status reserve in the early 1980s limitations on defence spending.

Shortcomings
The costs for the Tribals escalated above the costs first envisaged, and the original order of ships, over twenty, was cancelled after the first seven ships had been completed. The ships were rather small, at 360 ft (110 m), which prevented much modernisation and were always going to be limited by the single-shaft propulsion. The class were still good warships in spite of their low cost, proving the usefulness of the general purpose frigate concept, as perfected in the excellent Type 12M Leander class and modern Type 23 class.

Service
The class served throughout the 1960s and into the 1970s fulfilling their designed general purpose "colonial gunboat" role. When change in British foreign policy made this role redundant they found themselves being pressed into service in home waters in the "Cod Wars" of the 1970s. They were not particularly suited to these duties however, as they had a hull form optimised for the calm, shallow water of the Persian Gulf and with only a single shaft were unable to manoeuvre with the Icelandic patrol vessels at close quarters.

All were decommissioned from the Royal Navy during the mid-to-late 1970s with the manpower crisis also attributing to the rapid removal of the class from service. They were however given a brief reprieve by the Falklands war, with 3 mothballed Tribals (Gurkha, Tartar and Zulu) being reactivated to cover ships deployed to the South Atlantic or undergoing long-term repairs after the conflict. The remaining units were cannibalised for spare parts to enable the 3 ships to be refitted. These ships were sold in 1984 to Indonesia.

Ships
The building costs given above are official figures from the Navy/Defence Estimates. Note that Janes Fighting Ships quotes a slightly lower cost for Ashanti of £5,220,000, as against £5,315,000 quoted in the 1962-63 Navy Estimates.