The Tripartite class is a class of minehunters developed from an agreement between the navies of Belgium, France and the Netherlands. A total of 35 ships were constructed for the three navies. The class was constructed in the 1980s–1990s in all three countries, using a mix of minehunting, electrical and propulsion systems from the three member nations. In France, where they are known as the Éridan class they are primarily used as minehunters, but have been used for minesweeping and ammunition transport in Belgium and the Netherlands. In the Netherlands, the Tripartites are known as the .
In 1992, the Pakistan Navy acquired three vessels from France, one that was already built, one to be built in France and one built in France and Pakistan. Known as the Munsif class, all three are still in service. The Indonesian Navy acquired two minehunters in the 1990s from the Dutch to a modified design. Known as the Pulau Rengat class, the two ships are still in service. In 1997, France purchased three of the Belgian vessels. In 2007, the Latvian Naval Forces acquired five ships from the Netherlands which had been taken out of service at the beginning of the decade. The Bulgarian Navy acquired a former Belgian minehunter in 2007. The Netherlands and Belgium had a competition in 2018 to build a replacement class for their Tripartite/Alkmaar-class ships.
Design and development A joint venture of the navies of France, Belgium, and the Netherlands, the Tripartite class of minehunters were a follow on design to the French s. All three nations would build their own hulls while each country was responsible for a different aspect of the vessels; France provided the minehunting and electronic systems, the Netherlands provided the main propulsion systems and Belgium supplied the minehunting propulsion system as well as the electrical generating systems. Each country intended to order 15 of the vessels, with Belgium's initial order being 10 with the option of 5 more. However, France cut their initial order to ten due to budgetary reasons.
Ships France
In France the class is known as the Éridan class. Each hull was created from fibreglass, moulded in a steel shell. The hulls were long overall with a beam of and a draught of . The ships had a standard displacement of and at full load. This later increased to at full load. A container can be stored aboard the ships for additional supply room. The minehunters had an initial complement of 55, this was later reduced to 49.
The Éridan-class minehunters have two independent propulsion systems. In normal operations the minehunters are powered by a Brons-Werkspoor (later Wärtsilä) A-RUB 215V-12 diesel engine turning one shaft with a LIPS controllable pitch propeller. Using the conventional system, the minehunters have a maximum speed of and a range of at . For use when minehunting the vessels have two ACEC active rudders and a bow thruster. These are energised by three Astazou IVB gas turbine alternators rated at 150 kW. A fourth diesel-driven alternator rated at 160 kW supplies power during normal operations. Both systems can be operated from the bridge or from a soundproof control centre above the main deck. The maximum speed using the minehunting propulsion system that can be achieved is .
The minehunters were equipped with DUBM 21B sonar that could detect and classify ground and moored mines to a range of . The sonar was retracted during normal operations. The vessel was also equipped with Racal Decca 1229 radar. The vessels carried two ECA PAP 104 remotely operated underwater vehicles (ROVs). In 2001, the minesweepers underwent modernisation and the sonar was replaced with the TUS 2022 Mk III type, the radar with the Bridgemaster E250 type and a TSM 2061 combat data system and a Bofors Double Eagle Mk2 ROV were fitted.
The Éridan class is armed with one 20 mm modèle F2 gun capable of firing 720 rounds per minute to a range of . The minehunters also mount one machine gun and two machine guns. The French vessels have limited minesweeping ability and were initially only fitted with mechanical sweep gear. In 1985, the Éridan class received AP4 acoustic sweep gear.
The initial order of ten was constructed for the French Navy in the 1980s by the Arsenal de Lorient. After the sale of Sagittaire to Pakistan in 1992, a replacement hull bearing the same name and hull number was constructed. Three Belgian versions of the class were acquired between March and August 1997.
Éridan class construction data Pennant no. Name Builder Launched Commissioned Status M 641 Arsenal de Lorient, Lorient, France 20 December 1977 2 February 1979 16 April 1984 Decommissioned in 2018 M 642 26 March 1979 26 September 1981 5 May 1984 Decommissioned 1 July 2022 M 643 6 March 1980 22 May 1982 18 October 1984 M 644 22 December 1980 23 April 1983 30 May 1985 M 645 17 August 1981 6 February 1985 14 January 1986Out of service 2023 M 646 22 April 1982 6 February 1985 14 November 1986 M 647 2 December 1982 8 March 1986 1 July 1987 M 648 13 October 1983 14 November 1986 16 December 1987 M 649 30 October 1984 19 April 1988 4 November 1988 Decommissioned in August 2009 M 650 13 November 1985 9 November 1988 28 July 1989 Sold to Pakistan in 1992, renamed Munsif. M 650 1 February 1993 14 January 1995 2 April 1996 Replacement for Sagittaire (1988). M 651 Béliard Shipyard, Ostend and Rupelmonde, Belgium 20 May 1986 21 June 1987 Former Belgian Iris, decommissioned in February 2010 M 652 28 October 1985 23 October 1987 Former Belgian Fuchsia M 653 17 April 1985 26 February 1987 Former Belgian Dianthus
Belgium
Originally ten ships were ordered for the Belgian Navy, with the option for five more that was never activated. The Polyship consortium was organised to direct the building programme, however the consortium was dissolved, leading to delays in the construction of the minehunters. This led to the vessels being reordered this time from Béliard Shipyard, which constructed the hulls at their yard in Ostend, Belgium before completing the minehunters at Rupelmonde. Differences between the Belgian and French versions of the class include a smaller displacement at standard and at full load. They are equipped with an Atlas Elektronik IMCMS combat data system. When minehunting, the Belgian vessels carry six divers and can have a portable decompression chamber installed abaft the forecastle break.
All vessels in the class are named after flowers and are thus sometimes called the "Flower" or Aster class. In 2001 the remaining Belgian minehunters had their engines upgraded. All remaining Belgian vessels have undergone an extensive upgrade during 2004–2008 involving replacement of the anti-mine warfare equipment. This included receiving the same sonar package as the French versions. The complement of the Belgian ships varies between 33 and 46 depending on mission.
In 1993, three of the vessels (Iris, Fuschia and Dianthus) were paid off and laid up until being sold in 1997 to France. Crocus was modified into an ammunition transfer vessel the same year. Myosotis was converted to an ammunition transport before being taken out of service in 2004 and was sold to Bulgaria in 2009.
+Tripartite class construction data Pennant no. Name Builder Launched Commissioned Status M 915 Béliard Shipyard, Ostend and Rupelmonde, Belgium 24 February 1983 6 June 1985 16 December 1985 Sold to Pakistan in 2018 M 916 15 February 1984 14 February 1986 13 August 1986 To be donated to Bulgaria M 917 15 October 1984 5 September 1986 5 July 1987 To be donated to Bulgaria M 918 17 April 1985 26 February 1987 14 August 1987 Laid up 1993, sold to France 1997 M 919 28 October 1985 23 October 1987 18 February 1988 Laid up 1993, sold to France 1997 M 920 20 May 1986 21 June 1987 6 October 1988 Laid up 1993, sold to France 1997 M 921 27 November 1986 25 February 1988 8 July 1989 To be donated to Bulgaria M 922 6 July 1987 4 August 1988 14 December 1989 Converted to ammunition transport. Taken out of service in 2004 and sold to Bulgaria in 2009. M 923 22 February 1988 30 March 1990 27 September 1990 Gifted to Ukraine in 2025, renamed to Mariupol. M 924 7 November 1988 17 December 1990 29 May 1991 To be donated to Bulgaria
Netherlands
In the Royal Netherlands Navy, the Tripartites are known as the . The Alkmaars were originally of similar design to the Belgian and French versions, with a standard displacement of and at full load. The displacement later increased to standard and at full load and then standard and at full load. The 20 mm gun that was initially mounted was removed, leaving only three 12.7 mm machine guns. Beginning in 2003, the remaining Dutch Alkmaar-class minehunters were upgraded with improved electronics, including Atlas Elektronik INCMS combat data system, Thales 2022 Mk III hull-mounted sonar, Atlas Seafox Mine Identification and Disposal System and a Double Eagle Mk III Mod 1 ROV.
The minehunters were constructed at the Van der Giessen-de-Noord yard in Amsterdam, a specially constructed site completed in 1978. Middelburg and Hellevoetsluis were optioned by Egypt, but due to financial issues, were instead completed for the Royal Netherlands Navy. Two ships of a modified design were built for the Indonesian Navy which led to the delay of Vlaardingen and Willemstads construction.
In 2000, three ships (Alkmaar, Delfzijl and Dordrecht) were withdrawn from service, followed by two more (Harlingen and Scheveningen) in 2003. All five were sold to Latvia with handovers beginning in 2007. Four more ships, (Haarlem, Maassluis, Middelburg and Hellevoetsluis) were decommissioned in 2011 following a series of deep budget cuts to the navy. Two of them (Maassluis and Hellevoetsluis) were sold to Bulgaria in 2019. In 2021 it was indicated that a further two ships would be sold to Pakistan. Haarlem and Middelburg were transported via a heavy-lift ship to Pakistan in late 2022.
, the Netherlands is planning to transfer two Alkmaar-class ships to Ukraine in 2025. The vessels would be used to clear mines dropped into the Black Sea during Russia's invasion of Ukraine.
+Alkmaar class construction data Pennant no. Name Builder Launched Commissioned Status M 850 Van der Giessen-de-Noord,Alblasserdam, Netherlands 30 January 1979 18 May 1982 28 May 1983 Decommissioned in 2000, sold to Latvia M 851 29 May 1980 29 October 1982 17 August 1983 Decommissioned in 2000, sold to Latvia M 852 5 January 1981 26 February 1983 16 November 1983 Decommissioned in 2000, sold to Latvia M 853 16 June 1981 6 May 1983 12 June 1984 Decommissioned in 2011, sold to Pakistan M 854 30 November 1981 9 July 1983 12 April 1984 Decommissioned 2003, sold to Latvia M 855 24 May 1982 2 December 1983 18 July 1984 Decommissioned 2003, sold to Latvia M 856 7 November 1982 5 May 1984 12 December 1984 Decommissioned in 2011, sold to Bulgaria M 857 25 February 1983 27 September 1984 13 May 1985 Decommissioned in 2024, donated to Ukraine in 2025, renamed Henichesk M 858 11 July 1983 23 February 1985 10 December 1986 Decommissioned in 2011, sold to Pakistan M 859 12 December 1983 18 July 1985 20 February 1987 Decommissioned in 2011, sold to Bulgaria M 860 6 May 1984 20 December 1985 9 July 1986to be donated to Bulgaria in 2027-2028 M 861 1 October 1984 2 May 1986 10 December 1986 Decommissioned in 2022 use for spare parts M 862 25 February 1985 4 October 1986 7 May 1987to be donated to Bulgaria in 2027-2028 M 863 6 May 1986 4 August 1988 15 March 1989 Decommissioned in 2024, donated to Ukraine in 2025, renamed Melitopol M 864 3 October 1986 27 January 1989 20 September 1989to be donated to Bulgaria in 2027-2028
Export Bulgaria The Bulgarian Navy acquired one Tripartite-class minehunter from Belgium in 2007 and two from the Netherlands in 2019. The ex-Myosotis was transferred in 2009 and renamed . The ex-Maasluis and ex-Hellevoetsluis were transferred in 2020 and renamed Mesta and Struma, respectively.