The Type 23 frigate or Duke class is a class of frigates built for the United Kingdom's Royal Navy. The ships are named after British Dukes, thus leading to the class being commonly known as the Duke class. The first Type 23, , was commissioned in 1989, and the sixteenth, was commissioned in June 2002. They form the core of the Royal Navy's destroyer and frigate fleet and serve alongside the s. They were designed for anti-submarine warfare, but have seen a range of duties. Five Type 23 frigates remain in service with the Royal Navy, with three vessels having been sold to the Chilean Navy and eight being retired since 2021.
In 2019, The Royal Navy announced that the Type 23 frigates would be replaced by the and the . it is anticipated that HMS St Albans will be the last to retire from the Royal Navy, in 2035.
Development When first conceived in the late 1970s, the Type 23 was intended to be a light anti-submarine frigate with a towed array sonar to counter Soviet nuclear submarines operating in the North Atlantic. The Type 23 would be replacing the frigates (which had entered service in the 1960s) and the (a general purpose design that had recently entered service) as the backbone of the Royal Navy's surface ship anti-submarine force. The procurement of the class was announced in the 1981 Defence White Paper as "simpler and cheaper than the Type 22 [with] its characteristics... framed with an eye to the export market as well as Royal Navy needs."
The ship was designed by the Royal Corps of Naval Constructors, in close partnership with the prime contractor, Yarrow Shipbuilders. No anti-air warfare system was planned, however the lessons learned during the Falklands War led to the introduction of the vertically launched Sea Wolf missile; In June 1984 BAe Dynamics was awarded a development contract for the missile system. Unlike conventional Sea Wolf, the missile is boosted vertically until it clears the ship's superstructure, and then turns to fly directly to the target. Consequently, the ship's structure does not impose no-fire directions that would delay or inhibit missile firing in a conventionally launched system. With the addition of Harpoon surface-to-surface missiles and a medium calibre gun for naval gunfire support, the Type 23 had evolved into a more complex and balanced vessel optimised for general warfare, which introduced a host of new technologies and concepts to the Royal Navy. These included extensive radar cross-section reduction design measures, automation to substantially reduce crew size, a combined diesel-electric and gas (CODLAG) propulsion system providing very quiet running for anti-submarine operations and a large range.
In December 1986 the procurement of a Ferranti command and control system was cancelled as the specification was deemed to be insufficient to meet the demands of a modern warship, particularly the processing demands of the towed sonar array. Dowty-Sema won a contract for a replacement command and control system in August 1989, however, the delay meant early Type 23s entered service without the capability to use the Sea Wolf missile system in combat.
It was reported in 1998 to the House of Commons that: "Type 23 frigates achieved approximately 85–89 percent average availability for operational service in [the previous] five years with the exception of 1996 when the figure dropped to just over 80 per cent due to a number of ships experiencing a particular defect. This discounts time spent in planned maintenance."
Unlike the Type 45 destroyer, the Type 23 frigate does not have the capability to act as a flagship.
Programme costs Prior to the Falklands War the cost of the Type 23 frigates was estimated at £75 million each in September 1980 (equivalent to £ million in ) Changes following the experiences in the Falklands, including improved damage control and fire precautions, led to an increased cost estimated at £110 million (equivalent to £ million) By 2001, the Ministry of Defence said the cost of was £135.449 million and the remaining ships would have a final cost between £60 million and £96 million each. The Ministry of Defence said in 1998 that the Merlin ASW helicopter was costing them £97M each (this was for an order for 44 airframes), and that this was 57% of the cost of Type 23. From this it can be calculated that the cost of Type 23 was £170.1M each. The Government's declared policy for construction contracts for Type 23 was "...competition, the aim being to secure best value for money for the defence budget." while maintaining "sufficient warship-building capacity to meet likely future defence requirements and a competitive base"
HMS Norfolk was the first of the class to enter service, commissioned into the fleet on 1 June 1990 at a cost of £135.449 million; later vessels cost £60–96 million.
Upgrades and future technologies
Mid-life refit The class underwent mid-life refits which lasted 12–18 months and cost £15-20m. Aside from refurbishment of the mess decks and drive train, the ships are being retrofitted with a transom flap which can add up to to the top speed and reduce fuel consumption by 13%, and Intersleek anti-fouling paint which added to the top speed of the carrier Ark Royal. Although the top speed of the Duke class is commonly quoted as 28 knots, the caption of an official Navy photo suggests that Lancaster was capable of 32 knots even before her mid-life refit. From 2000, the Sea Wolf Mid Life Update (SWMLU) improved the sensors and guidance of the missiles, point defences awere further improved with remotely operated 30 mm guns, and Mod 1 of the Mk8 main gun with an all-electric loading system and a smaller radar cross-section. The communications and command systems were also upgraded.
A further Life Extension (LIFEX) Upkeep project saw the Sea Wolf missiles replaced with the new Sea Ceptor anti-air defence missiles; these were first test-fired from on 4 September 2017.
Sonar 2087
Sonar 2087 is described by its manufacturer as "a towed-array system that enables Type 23 frigates to hunt the latest submarines at considerable distances and locate them beyond the range at which they [submarines] can launch an attack." Sonar 2087 was fitted to eight Type 23 frigates in mid-life refits between 2004 and 2012; the five oldest Type 23 frigates, HMS Montrose, Monmouth, Iron Duke, Lancaster and Argyll were not to receive Sonar 2087. These ships continued to be employed across the normal range of standing Royal Navy deployments. The Chilean Navy procured a number of Sonar 2087 towed arrays from Thales Underwater Systems to equip its multipurpose frigates.
Artisan 3D radar
The Type 23's original medium-range radar was replaced by BAE Systems Type 997 Artisan 3D radar; the project was worth £100 million and the contract was announced on 4 August 2008. It is a medium-range radar designed to be capable of operating effectively in littoral zones and improving air-defence, anti-surface (anti-ship) and air traffic management capabilities of the Type 23 frigates. The radar is also designed to combat complex jammers. HMS Iron Duke was the first Type 23 frigate to receive the Artisan radar during her refit in 2012–13.
It is claimed the radar is five times more capable than the Type 996 radar it replaces.
Common Anti-Air Modular Missile
CAMM(M), the maritime variant of the Common Anti-Air Modular Missile, started to replace the Sea Wolf missiles on the Type 23 frigates from 2016. CAMM(M) has a longer range of 1–25+ km compared to the 1–10 km offered by the Sea Wolf missile. An option exists to give the missile a surface-attack capability, though it is currently understood the Royal Navy will not take that option, because of cost. Like Sea Wolf, CAMM(M) will be VLS launched; however due to its design, CAMM(M) can be packed much more tightly into the VLS, with up to four CAMM(M) fitting into the space occupied by one Sea Wolf missile. CAMM(M) is known as Sea Ceptor in Royal Navy service.
Martlet Lightweight Multirole Missile On an unspecified date in early 2019, tested a modified mounting for the 30mm cannon which incorporated a launcher for five 'Martlet' Lightweight Multirole Missiles, by firing four of them at a small speedboat target at the Aberporth range in Wales. The concept of mounting the missile alongside the 30mm Bushmaster cannon was tested just 5 months after the idea's conception.
The intended role of the Martlet is to further extend the Type 23's capabilities against small, fast moving targets beyond the current 30mm, GPMG and Minigun options to provide a long range 'stand-off' ability. However, a 2023 report suggested that the tests had not been deemed successful due to efflux management issues on the Type 23. The missile is therefore likely to be limited to employment on the Wildcat helicopter.
Anti-ship missile
In March 2019, a study commenced for an interim replacement for the ageing Harpoon anti-ship missiles, until completion of the Anglo-French Future Cruise/Anti-Ship Weapon (FC/ASW) programme which was scheduled to enter service in the 2030s. The interim replacement missile was originally planned to be fitted to five of the newer Type 23 frigates.
In November 2021, then First Sea Lord, Admiral Tony Radakin, said that the program had been paused and would likely be cancelled. In February 2022, the project was cancelled. However, in July 2022 the Defence Secretary confirmed that the program had been restarted. In November 2022, it was announced that the Royal Navy would receive the Naval Strike Missile (NSM), which will be fitted to a total of 11 vessels, both Type 23 frigates and Type 45 destroyers.
In 2021, it was reported that only two frigates, Montrose and Kent, were deployed with a full load of eight Harpoon canisters per ship. In August 2022, it was reported that in preparation for her planned deployment to the Persian Gulf to replace HMS Montrose, HMS Lancaster had also been fitted with eight Harpoon anti-ship missiles.
Weapons, countermeasures, capabilities and sensors
Anti-air warfare Type 997 Artisan 3D radar installed/being installed on 12 of 13 vessels replacing previous Type 996 Mod 1, 3D surveillance and target indication radar. 12 of 13 Royal Navy frigates (plus the Chilean vessels) upgraded with 32-cell Sea Ceptor GWS.35 VLS canisters (range of over ) as replacement for the previous Sea Wolf SAM. HMS Argyll was the first ship to receive Sea Ceptor, completing refit in February 2017. As of 2021 in addition to Argyll, Westminster, Montrose, Northumberland, Kent, Lancaster, Richmond and Portland had all received Sea Ceptor systems. Somerset returned to service with Sea Ceptor in March 2022, and Iron Duke followed in May 2023. St Albans and Sutherland are the final frigates to receive the upgrade, with Sutherland having begun her refit in April 2021. The 2021 defence white paper announced that Monmouth will not receive the upgrade and, together with Montrose, would be retired early. Monmouth was formally withdrawn from service in June 2021, followed by Argyll and Westminster in 2024. Lancaster was decommissioned in late 2025 following completion of duties in the Gulf in and Richmond and Iron Duke were also withdrawn in 2026 leaving the Royal Navy with just 5 remaining Frigates available for active service.
Anti-ship warfare (missiles) Up to eight Harpoon anti-ship missile launchers (apart from those fitted to HMS Lancaster (F229), withdrawn in 2023/24; being replaced on eleven Type 23 frigates and Type 45 destroyers by the Naval Strike Missile - NSM; NSM fitted to F79, F82 and F239 as of early 2025). Up to one embarked Agusta Westland AW159 Wildcat helicopter equipped with Martlet multirole missiles (as of 2021) or Sea Venom anti-ship missiles (initial operating capability from October 2025 and full operating capability projected from 2026).
Anti-submarine warfare