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.
| General characteristics | |
|---|---|
| Displacement: | 2,300 tons standard (2,100 tonnes) 2,700 tons full load (2,400 tonnes) |
| Length: | 360 ft (110 m) |
| Beam: | 42.3 ft (12.9 m) |
| Draught: | 17.5 ft (5.3 m) |
| Propulsion: | Single-shaft COSAG 1 Steam turbine (12,500 shp) 1 Metrovick G-6 gas turbine (7,500 shp) |
| Speed: | 28 knots (52 km/h; 32 mph) (COSAG) 20 knots (37 km/h; 23 mph) (steam) |
| Range: | 5,300 nautical miles (9,800 km; 6,100 mi) at 12 knots (22 km/h; 14 mph) |
| Complement: | 253 |
| Sensors and processing systems: | Radar type 965 air-search Radar type 993 low-angle search Radar type 978 navigation Radar type 903 gunnery fire-control Radar type 262 GWS-20 fire-control Sonar type 177 search Sonar type 170 attack Sonar type 162 bottom profiling Ashanti and Gurkha; Sonar type 199 variable-depth |
| Armament: | 2 × single 4.5 inch (114 mm) Mark 5* Mod 1 guns 2 × single 40 mm Mark 7 Bofors guns, later; 2 × four-rail GWS-20 Sea Cat missile systems 2 × single 20 mm Oerlikon guns 1 × Mark 10 Limbo ASW mortar |
| Aircraft carried: | 1 × Westland Wasp helicopter |
