Tribal-class frigate

The Type 81, or Tribal class, frigates were ordered and built as sloops [3] to carry out similar duties to the immediate post war improved Black Swan-class sloops and Loch-class frigates in the Persian Gulf. In the mid 1960s the seven Tribals were reclassified as second class general-purpose frigates to maintain frigate numbers. After the British withdrawal from East of Suez in 1971 the Tribals operated in the NATO North Atlantic sphere with the only update the fitting of Seacat missiles to all by 1977,[4] limited by their single propeller and low speed of 24 knots. In 1979-80 age and crew and fuel shortages saw them transferred to the stand-by squadrons; three were reactivated in 1982 during the Falklands War for training and guardship duties in the West Indies.

HMS Eskimo
Class overview
Name:	Type 81 or Tribal class
Operators:	Royal Navy  Indonesian Navy
Preceded by:	Blackwood class
Succeeded by:	Type 21
Completed:	7
Retired:	7
General characteristics [1]
Type:	Frigate
Displacement:	2,300 long tons (2,300 t) standard 2,700 long tons (2,700 t) full load
Length:	360 ft 0 in (109.73 m) oa 350 ft 0 in (106.68 m) pp
Beam:	42 ft 3 in (12.88 m)
Draught:	13 ft 3 in (4.04 m) 17 ft 6 in (5.33 m) (propellers)[2]
Propulsion:	Single-shaft COSAG 1 Steam turbine 12,500 shp (9,300 kW) 1 Metrovick G-6 gas turbine 7,500 shp (5,600 kW)
Speed:	27 knots (50 km/h; 31 mph) (COSAG)
Range:	4,500 nautical miles (8,300 km; 5,200 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-21 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 QF 4.5 inch (113 mm) Mark 5* Mod 1 guns 2 × single Mark 7 40 mm Bofors guns, later; 2 × four-rail GWS-20 Seacat missile systems 2 × single 20 mm Oerlikon guns 1 × Mark 10 Limbo ASW mortar
Aircraft carried:	1 × Westland Wasp helicopter

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 almost 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 QF 4.5-in (113 mm) Mark 5 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. Originally the intended gun armament was two twin 4-inch (102 mm) Second World War standard mounts, then scheduled for a twin 3-inch (76 mm) 70 caliber mount but that and the required magazine increased weight by 256 tons [5] and then designed a gun fit of two single automatic 4-inch guns which required a hull 10 ft (3.0 m) longer[6] but were - like the twin 3/70s - too expensive and resulted in a 3000-ton displacement unacceptable for a sloop or frigate design for the RN/Treasury in the 1960s [7] of the sort fitted to the Chilean Almirante Williams class. The automatic guns were rejected on account of weight, space and cost.[7]

From the outset they were designed to carry the new GWS-21 Seacat anti-aircraft missile system[8] anti-aircraft missile system but all except Zulu initially carried single Mark 7 40 mm Bofors guns in lieu. The rest of the class were fitted with Seacat in the 1970s[9] using surplus missile systems, left over from Battle-class destroyers and County-class destroyer refits.

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 Rothesay-class frigates 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 Tribal Class ships escalated above the costs first envisaged and the original order of ships, (over twenty), was cancelled after the first seven ships had been completed. Only four would have been built if it had been possible to cancel the contractual commitments the Royal Navy had entered into for the supply of complex engines and machinery [10] for eight frigates. The ships were rather small, at 360 ft (110 m), which reduced the options for later modernisation and were always going to be limited by their single-shaft propulsion. The class were still good warships in spite of being fitted with outdated guns, (they were described by some as 'guided flagpoles')[11] if sometimes capable of 18 rounds per minute for the first two minutes, and proved the usefulness of the general purpose frigate concept and gas turbine propulsion, but the average unit costs of the Type 81s completed in 1963-64 was £500,000 more than the first eight Leanders[12] and the final cost of over £5 million of the first Tribal, Ashanti, completed in 1961 was considered too high and hence limited the number actually built; the original intent was to build 23 Type 81s. This meant that further 1960s RN frigate development would be based on the more conservative steam-powered Type 12 (Whitby) class, subsequently modernised in the Type 12M (Rothesay) class and finalised in the excellent Type 12I (Leander)-class. The later Royal Navy Type 21 (Amazon) class "General Purpose Frigates" were originally envisaged for a similar gunboat role to the Tribal-class ships and to operate East of Suez.

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

Pennant	Name	Builder	Laid Down	Launched	Accepted into service	Commissioned	Estimated building cost[13]	Fate
F117	Ashanti	(a) Yarrow & Co Ltd, Glasgow (b) Associated Electrica Industries Ltd, Manchester [14]	15 January 1958 [15]	9 March 1959 [15]	November 1961 [14]	23 November 1961 [15]	£5,315,000 [14]	Sunk as target 1988
F131	Nubian	(a) HM Dockyard, Portsmouth (b) Associated Electrica Industries Ltd, Manchester [16]	7 September 1959 [15]	6 September 1960 [15]	November 1962 [16]	9 October 1962 [15]	£4,360,000 [16]	Sunk as target 1987
F122	Gurkha	(a) JI Thornycroft & Co Ltd, Southampton (b) JI Thornycroft & Co Ltd, Southampton (steam and gas turbines) (b) Parsons Marine Turbine Co Ltd, Wallsend-on-Tyne (gearing) [16]	3 November 1958 [15]	11 July 1960 [15]	February 1963 [16]	13 February 1963 [15]	£4,865,000 [16]	Indonesian 332 KRI Wilhelmus Zakarias Yohannes
F119	Eskimo	(a) JS White & Co Ltd, Cowes, Isle of Wight (b) JS White & Co Ltd, Cowes, Isle of Wight (steam and gas turbines) (b) Fairfield Shipbuilding and Engineering Co Ltd, Govan, Glasgow (gearing) [16]	22 October 1958 [15]	20 March 1960 [15]	February 1963 [16]	21 February 1963 [15]	£4,560,000 [16]	Sunk as target 1986
F133	Tartar	(a) HM Dockyard, Devonport (b) Vickers-Armstrongs (Engineers) Ltd, Barrow-in-Furness (steam turbines and gearing) (b) Yarrow and Co Ltd, Glasgow (gas turbine) [17]	22 October 1959 [15]	19 September 1960 [15]	April 1963 [17]	26 February 1962 [15]	£4,300,000 [17][18]	Indonesian 333 KRI Hasanuddin
F125	Mohawk	(a) Vickers-Armstrongs (Shipbuilders) Ltd, Barrow-in-Furness (b) Associated Electrical Industries Ltd, Manchester (gas turbine) (b) Vickers-Armstrongs (Engineers) Ltd, Barrow-in-Furness (steam turbines and gearing) [17]	23 December 1960 [15]	5 April 1962 [15]	December 1963 [17]	29 November 1963 [15]	£4,750,000 [17]	Sold for scrap
F124	Zulu	(a) Alex Stephen & Sons, Ltd, Linthouse, Glasgow (b) JI Thornycroft & Co Ltd, Southampton (steam and gas turbines) (b) Parsons Marine Turbine Co Ltd, Wallsend-on-Tyne (gearing) [19]	13 December 1960 [15]	3 July 1962 [15]	April 1964 [19]	17 April 1964 [15]	£5,100,000 [19]	Indonesian 331 KRI Martha Khristina Tiyahahu

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,[15] as against £5,315,000 quoted in the 1962-63 Navy Estimates.[14]

Footnotes

1. Gardiner and Chumbley 1995, p. 518.
2. Blackman 1971, p. 356.
3. Freidman, N. (2006), British Destroyers and Frigates. The Second World War and After, UK: Seaforth, p. 242
4. Freidman. British Destroyers & Frigates. UK (2006), p. 247
5. D. K. Brown. A Century of Naval Construction. The History of Royal Corps of Naval constructors 1883-1983. Conway Maritime. (1983) London, pp. 17-18
6. D.K. Brown (1983) p 18
7. Gardiner, Robert, ed. (1983). All the World's Fighting Ships 1947-1982. Pt One. The Western Powers. London: Conway. p. 162.
8. Friedman, Norman (1991). Naval Institute Guide to Naval Weapons Systems. p. 410.
9. Preston, Antony (1980). Warships of the World. London: Janes. pp. 168–9.
10. Brown, F.K. Rebuilding the Royal Navy: Warship Design since 1945. p. 84.
11. Preston, Anthony (1980). Warships of the World. London: Janes. p. 169.
12. UK Defence Estimates 63-4 & 64-5
13. "Unit cost, i.e. excluding cost of certain items (e.g. aircraft, First Outfits)."
    Text from Defences Estimates
14. Navy Estimates, 1962-63, pages 218-9, 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 1962
15. Blackman, Raymond VB Jane's Fighting Ships, 1966-67, pub Sampson Low, Marston & Co Ltd, 1966, page 292.
16. Navy Estimates, 1963-64, page 71, 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
17. 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
18. Note that the 1963-64 naval estimates gave an estimated acceptance date of March 1963, and an estimated building cost of £4,205,000. Presumably the explanation is that the 1964-65 estimates are correct, and the 1963-64 proved optimistic.
19. 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

References

• Blackman, Raymond V.B. Jane's Fighting Ships 1971–72. London: Sampson Low, Marston & Co, 1971. ISBN 0 354 00096 9.
• Gardiner, Robert and Stephen Chumbley. Conway's All the World's Fighting Ships 1947–1995. Annapolis, Maryland: Naval Institute Press, 1995. ISBN 1-55750-132-7.
• Jane's Fighting Ships 1977-78, Jane's Yearbooks, ISBN 0-531-03277-9