Tripartite-class minehunter

Sagittaire (fore) with USS Sentry and HMS Shoreham in the Persian Gulf

In France the class is known as the Éridan class. Each hull was created from fibreglass, moulded in a steel shell. The hulls were 51.6 metres (169 ft 3 in) long overall with a beam of 8.9 metres (29 ft 2 in) and a draught of 3.8 metres (12 ft 6 in). The ships had a standard displacement of 571 tonnes (562 long tons) and 605 t (595 long tons) at full load.[1][2] This later increased to 625 t (615 long tons) at full load.[2] A 5.1 tonnes (5 long tons) container can be stored aboard the ships for additional supply room. The minehunters had an initial complement of 55,[1] this was later reduced to 49.[2]

The Éridan-class minehunters have two independent propulsion systems. In normal operations the minehunters are powered by a 1,400-kilowatt (1,900 bhp) 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 15 knots (28 km/h; 17 mph) and a range of 3,000 nautical miles (5,600 km; 3,500 mi) at 12 knots (22 km/h; 14 mph).[1][2] For use when minehunting the vessels have two 180 kW (240 hp) 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 7 knots (13 km/h; 8.1 mph).[1]

The minehunters were equipped with DUBM 21B sonar that could detect and classify ground and moored mines to a range of 80 metres (260 ft). The sonar was retracted during normal operations.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.[3][2]

The Éridan class is armed with one 20 mm modèle F2 gun capable of firing 720 rounds per minute to a range of 2 kilometres (1.2 mi). The minehunters also mount one 12.7 mm (0.5 in) machine gun and two 7.62 mm (0.30 in) machine guns.[2] 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.[4]

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.[2]

Primula

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 519 tonnes (511 long tons) standard and 574 tonnes (565 long tons) 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.[8]

All vessels in the class are named after flowers and are thus sometimes called the "Flower" or Aster class.[8][9] 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.[9]

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.[8][9] Myosotis was converted to an ammunition transport before being taken out of service in 2004 and was sold to Bulgaria in 2009.[10]

HNLMS Schiedam

In the Royal Netherlands Navy, the Tripartites are known as the Alkmaar class. The Alkmaars were originally of similar design to the Belgian and French versions, with a standard displacement of 520 tonnes (510 long tons) and 553 tonnes (544 long tons) at full load.[13] The displacement later increased to 571 tonnes (562 long tons) standard and 605 tonnes (595 long tons) at full load[14] and then 630 tonnes (620 long tons) standard and 660 tonnes (650 long tons) at full load.[15] 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.[13][15]

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.[14] Two ships of a modified design were built for the Indonesian Navy which led to the delay of Vlaardingen and Willemstad's construction.[15]

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.[16] Four more ships, (Haarlem, Maasluis, Middelburg and Hellevoetsluis) were decommissioned in 2011 following a series of deep budget cuts to the navy.[17] Two of them (Maasluis and Hellevoetsluis) were sold to Bulgaria with handovers in 2020.

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 Tsibar. [10] The ex-Maasluis and ex-Hellevoetsluis were transferred in 2020 and renamed Mesta and Struma, respectively.

KRI Pulau Rengat

The Indonesian Navy ordered two minehunters based on the Alkmaar class from the Netherlands on 29 March 1985.[19] Known as the Pulau Rengat class, the vessels have a standard displacement of 520 tonnes (510 long tons) and 594 tonnes (585 long tons) at full load. They have a different layout than European Tripartite minehunters due to their mission profile being larger, with the vessels intended to operate as minehunters, minesweepers and patrol ships. For conventional missions the vessels are powered by two MTU 12V 396 TCD91 diesel engines turning one shaft with a LIPS controllable pitch propeller rated at 1,400 kilowatts (1,900 hp) for a maximum speed of 15.5 knots (28.7 km/h; 17.8 mph). The minehunters are also equipped with two 56-kilowatt (75 hp) bow thrusters and two retractable Schottel 89-kilowatt (120 hp) rudder propellers energised by three Turbomecca gas turbine generators. Using the auxiliary propulsion system, the Pulau Rengat class has a maximum speed of 7 knots (13 km/h; 8.1 mph). They have a range of 3,500 nautical miles (6,500 km; 4,000 mi) at 10 knots (19 km/h; 12 mph).[19][20]

The Pulau Rengat class mounts two Rheinmetall 20 mm guns and have the capability to have Matra Simbad surface-to-air missile launchers installed or a third 20 mm gun. The Pulau Rengats are equipped with OD3 Oropesa mechanical sweep gear, Fiskar F82 magnetic sweep and SA Marine AS 203 acoustic sweep gear for minesweeping duties. They also have an Ibis V minehunting system and two PAP 104 Mk 4 mine disposal systems along with the Signaal SEWACCO-RI combat data system, Racal Decca AC 1229C radar and Thomson Sintra TSM 2022 sonar. The ships have a complement of 46.[19]

Initially, Indonesia intended to order ten hulls. However, funds were lacking and only two were built. The first was ordered on 29 March 1985 and the second on 30 August 1985. The two ships were initially part of the Royal Netherlands Navy production and were given Dutch names. They were renamed upon sale to Indonesia.[20]

Imanta in Belfast

In 2007, the Latvian Naval Forces acquired five Alkmaar-class minehunters (Alkmaar, Delfzijl, Dordrecht, Harlingen and Scheveningen) from the Royal Netherlands Navy. These five use the Signaal Sewaaco IX combat data system and the Thomson Sintra DUBM 21A sonar. Harlingen was the first handed over and renamed Imanta on 6 March 2007, followed by Scheveningen on 5 September 2007 which was renamed Viesturs. Dordrecht was handed over in January 2008 and renamed Tālivaldis and Delfzijl in October 2008 and renamed Visvaldis. Alkmaar was the last to transfer in June 2009 and was renamed Rūsiņš.[16] In 2020, the Latvian Naval Forces signed contract with ECA Group for the modernization of three of its Alkmaar-class minehunters, replacing the conventional detection system based on a hull sonar for mines with a smaller unmanned system consisting of the underwater drones AUV A18-M for detection and underwater robots Seascan MK2 and K-STER C for identification and clearance of the mines.

On 17 January 1992, Pakistan signed an agreement with France acquiring three Éridan-class minehunters, one of which was already built, one to be constructed in France and the third in Pakistan. Sagittaire, which was on duty in the Persian Gulf, sailed to Pakistan in November 1992. In Pakistan Navy service, the three ships have Elesco MKR 400 acoustic sweep and MKR 960 magnetic sweeps for minesweeping duties.[21]

The class is known as the Munsif class in Pakistan Navy service. The first of the class Munsif sailed to Pakistan from the Persian Gulf. The second, Muhafiz was delivered in April 1996 and the third was carried aboard a transporter ship in April 1995 to be completed in Pakistan.[21]

The Netherlands and Belgium are doing a joint procurement for the replacements of the Tripartite-class/Alkmaar-class minehunters. Both countries want to procure six new mine countermeasure (MCM) vessels, which makes for a total of 12 MCM ships. The new MCM ships will include a range of unmanned systems including unmanned surface, aerial and underwater vehicles alongside towed sonars and mine identification and neutralization ROVs.[23]

Belgium gave the green-light to start the procurement on 26 January 2018 and approved a budget of 1.1 billion euros for the six Belgian MCM ships. Besides the Tripartite-class minehunters, the ships will also replace the Belgian logistical support ship Godetia.[24]

• The Franco-Belgium consortium made up of French shipbuilders STX France and Socarenam together with Belgium's EDR are bidding for the 12 new MCM vessels. Their plan includes the construction of MCM vessels named Sea Naval Solutions and a multi-role frigate named Deviceseas, which will serve as mothership to the MCM vessels. All ships will have a strong focus on autonomous systems operations.[25]

• France's Naval Group and ECA Group established Belgian subsidiary Naval & Robotics and bid for the program.[26][27]

• Imtech Belgium and Damen Group bid for the program.[26][27]

On 15 March 2019, the team led by Naval Group was selected to produce the 12 new vessels.[26][27]