Type 21 Frigate

The term "Patrol Frigate" was introduced by the USN in 1943, it applied to the Tacoma Class ship, originally classed a Patrol Gunboat. The Tacoma was based on the British River Class Frigate and was not regarded as an ocean going ship by the Americans, most Tacoma Class ships were crewed by Coast Guard and restricted to coastal operations.

Although the term has been used since for different types of ships, for instance the very large general purpose Halifax Class ships, in general the term still refers to small Frigates which might also be classed as Corvettes. A typical Patrol Frigate was the Vosper Thornycroft Mk V, four of which were sold to Iran as the Alvand Class. The Type 5 was a general purpose ship, armed with a medium calibre gun, SSM, Limbo Mortar and light AA cannon. Displacement was 1,540 tons full load and powered by a pair of Diesels for cruising and two Olympus Gas Turbines for high speed operations.

With a need to fill a projected gap in Frigate numbers following the delay of the Type 22 Frigate the RN announced the purchase of commercially designed Frigates, the Type 21 or Amazon Class which would be based on the Type 5 design.

HMS Antelope, to the conservative eyes of the Royal Navy the ship looked more like a luxury yatch than a warship, and the accomodation matched the looks, in her time the Type 21 was regarded as the height of luxury living for Matelots. The ship however was intrinsically top heavy and subject to sea damage in the worst of Atlantic weather, designed originally for shallow water navies she proved unsuited to the Blue Water Royal Navy, but when Britain went to war in a way that had never been planned the Type 21s showed their metal and highlighted the importance of general purpose ships instead of dedicated anti-submarine warships.

Cost overrun was huge, from just over a projected £3,000,000 to over £14,000,000 for Amazon, the first of the class. From experience I would hazard a guess this was due to the "stick this on while you are at it" that so plagues RN building. But the reason for this is really rather simple and inevitable: not only has the RN continued to shrink post war to the point where it can no longer perform any of it's stated roles, but each ship order is cut back as soon as it is placed. With numbers available being axed each ship has to carry a greater burden of tasks and so the design is continually added to.

From a coastal lightweight ship employing off the shelf technology the Type 21 expanded to a long range Escort operating the latest helicopter, equipped with the newly developed CAAIS computer system and all gas turbine instead of Diesel and gas.

Eight Type 21's were delivered and were quite extraordinary ships, looking nothing like any other ship in the Fleet. Despite their massive inflation in price they may well have been further orders had it not been for the RNs commitment to the development of the disasterous dedicated Anti Submarine Frigate the Type 22.

The Falklands war exposed the RN's policy for the madness it was when air defence Destroyers had no surface to surface capability and Frigates lacked adequate air defences. Unable to release the Type 42 Destroyers from protecting the main fleet it fell to the Frigates to close in to shore and provide the shore bombardment and air protection of landing ships. Exactly the roles for which the Type 41 and 61 had been designed. With most Leanders now refitted to specialist Anti-Submarine and Anti-Surface roles and lacked guns at all it fell to the older Rothesay and the Type 21 to step into the breach. The Type 21's suffered with two lost and others damaged, their hull design also proved less robust to the extreme weather, betraying their origin as a coastal patrol ship.

All six survivors were sold to Pakistan where they have been re-armed and form a very formidable force.

HMS Ardent, pictured here with only one Exocet fitted so she was probably on firing trials, Ardent was the first Type 21 to carry the missiles, but the ship's had to be counter ballasted to compensate for the additional top weight. Maintaining stability would be of prime concern throughout the lives of these ships.

HMS Ardent on fire and sinking with the Crazy Y (Yarmouth) lending assistance. The poor air defence of the Royal Navy was in part due to assumption of higher powers that the RN would fight the next war in concert with NATO under the umbrella of US Carrier aircraft.

Greyed out for war and anonymous a Type 21 with the addition of Exocet fires her Mk 8 gun.

The Type 21 caused quite a stir when they joined the Fleet, the first of the Class, HMS Amazon, appeared almost science fiction like in her advances on the Type 12. The engine rooms were amazing spotless cathedrals where someone had apparently forgotten to actualy fit the engines themselves. It was with some bemusement that as visitors a bunch of us were shown the small cocoon in which this shiny device resided, smaller than the gearbox to which it was attached. So small in fact that the engines could actualy be lifted out and replaced!

Throughout the ship there was this sense of being on an alien vessel, there were no great tangles of cables and pipes everywhere, cleaning the ship had to be a dream without all those unreachable nooks and crannies. The equipment rooms were filled with screens and keyboards that would have been happy and at home aboard a Star Trek ship, but most amazing of all was the accomodation.

Junior rates had seperate sleeping areas to the their recreation area. This was stunning and just plain wrong, how could this be? Bunks were still triple decked, but each set of three was in a little nook radiating off the mess square which was set out with seats, just that: seats, not folded bunks. At a stroke the whole way of life was changed, no more arguments and deals to try and strike a balance between those wanting to sleep and those wanting to party. To us the ship was a luxury liner, not a warship, and had a profound effect on our expectations for the next generation of Frigate if this was only a stop gap.

The speed of the ships too was stunning, the only downside being the inclusion of the out dated Seacat Missile, albeit with a jazzy new director and a general disappointment at the weapon fit, particularly in the early days when the ships operated the Wasp as the Lynx was not yet available. The ships would start to look better once equipped with Exocet, STWS, Lynx and 20mm.

There is no doubt in my mind that the effectiveness of the Type 21 in the Falklands heavily influenced the final design of the the Type 23, though the ridiculously inadequate and incompetant Mk 8 gun was copied, despite it's appalling record of jamming in action, it would be an inexcusable two decades before the RN finally started to see the Mk 8 slowly being replaced with the Mod 1 which apparently can fire more than a half dozen rounds without dismantling it's own breach mechanism.

From the start the Type 21 suffered from top weight issues, aluminium was extensively used in the superstructure to try and keep it down, but the practise was discontinued, not only is aluminium very suseptable to fire (in fires on the ships it is reported that the bulkheads melted before the paint did) but airbourne canon fire tore through the ships like they were made of tissue.

In 1983 with the surviving ships showing damage to the superstructure and deck due to heavy weather in the Falklands strengthening plates were added midships, increasing displacment by 350 tons.

With top weight so critical there was never an option to upgrade the ships to Seawolf and without the political will to buy any other short range SAM system the ships were effectively condemned and put up for sale.

HMS Ardent struck by bombs aft, the Type 21 proved more resiliant than many predicted, although two were lost and one badly damaged they gave a good account of themselves in shore bombardment and picket duty, although they lacked a long range radar their EW gear was state of the art for the time and they were instrumental in countering air raids.

HMS Ambuscade is launched.

In service with the Pakistan Navy the Seacat launcher has been replaced with a Vulcan Phallanx 20mm CIWS, the Exocet with either 4 Harpoon launchers or 6 Chinese LY-60N SAM. STWS is retained on Badr and Shahjahan but the remainder are fitted with with Bofors 43X2 wire guided anti-submarine torpedoes. Each ship still operates the Lynx helicopter.

The 992 has been replaced with the Signaal DA 08 and the UAA1 ECM suite with Thomson-CSF DR 3000S suite, the CAAIS computer has been replaced with the Swedish 9LV Mk3

The ships are expected to continue in service until 2010, they are classed as Tariq Destroyers.

In Pakistani service the ships are not exposed to such severe weather as at the Falklands and are not required to operate at long range so the problems of sea keeping and stability due to ballast fuel being lost is not an issue.

Former RN Type 21 in Pakistani service, the Exocets have been replaced with the Chinese LY-60 anti aircraft missile, others took on four Harpoon.
Laid Down
Amazon F169 6-11-1969 26-4-1971 11-5-1974 Vosper 1993 Sold to Pakistan as Babur
Antelope F170 23-3-1971 16-3-1972 16-7-1975 Vosper Sunk by Aircraft 24 May 1982
Active F171 23-7-1971 23-11-1972 17-6-1977 Vosper 1994 Sold to Pakistan as Shahjahan
Ambuscade F172 1-9-1971 18-1-1973 5-9-1975 Yarrow 1993 Sold to Pakistan as Tariq
Arrow F173 28-9-1972 5-2-1974 29-7-1976 Yarrow 1994 Sold to Pakistan as Khaibar
Alacrity F174 5-3-1973 18-9-1974 2-7-1977 Yarrow 1994Sold to Pakistan as Badr
Ardent F184 26-2-1974 9-5-1975 13-10-1977 Yarrow Sunk by Aircraft 22 May 1982
Avenger F185 30-10-1974 20-11-1975 19-7-1978 Yarrow 1994 Sold to Pakistan as Tippu Sultan

Ardent and Avenger were completed with Exocet, the rest were retro fitted except Antelope which was sunk before she received them. Amazon was the last ship to receive Exocet - after the Falklands. She was also the only Type 21 that did not take part in the Falklands, at the time she was on station in the Persian Gulf.

One of the main problems with stability with the Type 21 was the engines. Compared to steam engines the Gas Turbines were extremely light and ballast had to be used. The engine arrangement was COGOG (Combined Gas or Gas) which meant either the high speed Olympus Turbines could be used, or the Tyne cruise turbines, but not both. This would have required a complex and massive gearing system that was discounted for cost sake, but would have helped ballast the ship.

But far more crucially unlike the older steam ships the Type 21 could not refill emptying fuel tanks with water, this meant the fuel itself formed part of the ballast. During the Falklands Ambuscade en-route alone to the Islands and low on fuel had to flood empty fuel tanks to avoid capsizing, 20% of her tank capacity was rendered unusable so even when she did refuel from a tanker she could only take on 80% of her max fuel load.

HMS Alacrity sporting Exocets.
Displacement 3,250 tons standard 3,600 tons full load ** accounts vary, check Janes

On Olympus max speed believed to be about 37 knots but ship could not sustain it due to risk of structural damage. With hull mods put in place in mid 80's Pakistan report speeds of 34 knots attainable.

On Tynes best speed is 18 Knots.

Length 384 ft
Beam 41.5 ft
Draught 19.6 ft
Range 4,000 NM at 17 knots (Tyne)
Complement 177
Propulsion 2 x Rolls Royce Olympus Gas Turbines providing 50,000 SHP
2 x Rolls Royce Tyne Gas Turbines providing 8,500 SHP
Radar Type 992Q combined function air and surface target indication
Type 1006 Navigation (Possibly 978 on earliest ships for a while)
912 Fire Control for Seacat and gun director
Sonar Type 184M Search
Type 162M Bottom Search
2 x 8 barrel Corvus 3" rocket Chaff Launchers

1 x Vickers 4.5" Mk 8 Automatic gun
2 x 20mm Oerlikon (4 post war)
Quad Seacat GWS-24
4 Exocet on Ardent and Avenger, retro fitted to the rest except Antelope
STWS triple barrel Mk 44/46 torpedo tube launchers retro fitted.


Originally operated the Wasp, early artist impressions suggested the ship may operate a Harrier Jumpjet but feasability studies showed down time to operational time and amount of support crew and spares prohibital. Although the Lynx became available in 1976 the Type 21 did not operate them until refitted to make changes to the hanger and handling gear.

2 x Mk 44/46 or Stingray Torpedoes
4 x Sea Skua Air to Surface missile