Defence and intervention frigate
The Defence and intervention frigate (French: Frégate de défense et d'intervention, FDI), also known as the Belharra class, is a family of multi-mission surface combatants designed by Naval Group for high-intensity operations across anti-air, anti-surface, anti-submarine, and asymmetric warfare domains.[1][2] Measuring 122 meters in length with a beam of 18 meters and displacing approximately 4,500 tons, the FDI achieves a maximum speed of 27 knots and features an inverted bow for improved seakeeping in rough seas.[3][2] The design incorporates advanced digital architecture, including integrated combat management systems and provisions for unmanned systems, enabling a reduced crew of 125 personnel while supporting up to 28 passengers.[1][2] Initiated in 2015 as part of the French Navy's fleet renewal to maintain 15 first-rank frigates, the program calls for five vessels, with the lead ship Amiral Ronarc'h delivered in October 2025 after keel-laying in 2021.[4][2] Armament includes 16 Aster 15/30 surface-to-air missiles, eight Exocet MM40 Block 3C anti-ship missiles, a 76 mm Oto Melara gun, and MU90 torpedoes, complemented by capabilities for helicopter and drone operations.[5] The platform has seen export success, with Greece ordering three Kimon-class variants in 2021—Kimon, Nearchos, and Formion—tailored with enhanced anti-air defenses, and approving a fourth, Themistocles, in September 2025 to modernize its fleet.[6][7] These frigates represent a successor to the FREMM class, emphasizing versatility, survivability, and interoperability in multinational operations.[1]Program Origins and Development
Strategic Requirements and Initiation
The French Navy identified a strategic imperative to sustain a fleet of 15 frégates de premier rang (first-rank frigates) by 2030, enabling sustained operations in contested maritime domains, crisis response, and support for national deterrence and alliance commitments, amid the obsolescence of legacy classes such as the Cassard- and Georges Leygues-class vessels.[8] This requirement emphasized multi-domain capabilities—including anti-air warfare, anti-submarine warfare, and surface strike—to address evolving threats like peer competitors in the Atlantic, Mediterranean, and Indo-Pacific theaters, while optimizing for deployability and interoperability with NATO and EU partners.[9] The FDI was conceived as an intermediate-sized platform to provide hull numbers and versatility at lower unit costs than the preceding FREMM (Aquitaine)-class, facilitating a high-low mix that balances advanced air defense with volume for distributed operations and potential exports.[10] Program initiation followed preliminary studies in the mid-2010s, driven by the 2013 Livre blanc sur la défense et la sécurité nationale and subsequent naval force structure reviews, which highlighted gaps in surface combatant capacity post-FREMM production.[9] On April 21, 2017, the Direction générale de l'armement (DGA) notified DCNS (now Naval Group) of the contract award for five FDI frigates, valued at approximately €3.8 billion, formalizing the program's launch under the interim designation Frégate de Taille Intermédiaire (FTI).[8] [11] This step aligned with budgetary provisions in the Loi de programmation militaire (LPM) 2019–2025, which committed funds for surface fleet renewal to achieve the 15-frigate target and enhance overall naval readiness. The design prioritized modularity for mission adaptability, cyber-resilient systems, and reduced crew requirements through automation, reflecting causal priorities of operational tempo, sustainment costs, and technological edge over sheer platform size.[12]Design Phase and Specifications
The design of the Frégate de Défense et d'Intervention (FDI) frigates emphasized modularity, digital integration, and multi-mission capabilities, drawing on lessons from the preceding FREMM-class while prioritizing a lighter displacement for versatility in defense and intervention operations.[1] Developed by Naval Group, the FDI incorporates a "digital native" architecture centered on integrated data infrastructure for the platform and combat systems, enabling enhanced automation and reduced crew size.[13] This approach includes native cyber defenses to withstand electronic attacks, with segregated networks and resilient software protocols embedded from the outset.[10] Key design specifications reflect a balance of performance and efficiency: the vessels measure 122 meters in length, with a beam of 18 meters and a standard displacement of 4,500 tonnes.[2] Propulsion systems achieve a maximum speed of 27 knots, supported by a range of 5,000 nautical miles at 15 knots and an operational endurance of 45 days.[12] The design supports a core crew of approximately 125 personnel, plus capacity for 28 additional passengers, facilitated by advanced automation that minimizes manning requirements without compromising combat effectiveness.[14] Modular block construction was integral to the design phase, allowing parallel assembly of hull sections to accelerate production rates, with plans for launching one FDI every six months once optimized.[15] Development efforts encompassed roughly one million hours of engineering and design work per vessel, focusing on interoperability across air defense, anti-submarine warfare, and power projection roles.[1] These features position the FDI as a resilient, high-sea platform adaptable to evolving threats in contested environments.[3]Key Milestones and Trials
The Frégate de défense et d'intervention (FDI) program was initiated as part of a 2015 French Navy modernization effort to replace aging surface combatants with versatile, medium-sized frigates capable of multi-mission operations.[16] In 2017, the French Direction générale de l'armement (DGA) awarded Naval Group a contract valued at approximately €3.8 billion for the design and construction of five FDI vessels, with an initial delivery target for the lead ship in 2024.[17] Construction milestones for the lead ship, Amiral Ronarc'h (D660), commenced with keel laying on December 17, 2021, at Naval Group's Lorient facility, marking the integration of the hull's first structural blocks.[18] The frigate was launched on November 7, 2022, entering the fitting-out phase where weapon systems, sensors, and propulsion were installed.[19] Delays in outfitting, attributed to supply chain complexities and integration testing, shifted initial delivery timelines.[2] Sea trials for Amiral Ronarc'h began on October 7, 2024, from Lorient, focusing on hull form, propulsion, and basic seaworthiness in the Atlantic.[20] The initial phase lasted 14 weeks, validating the inverted bow design's performance in sea state 6 conditions, achieving sustained speeds of 27 knots, and confirming a range exceeding 5,000 nautical miles at 15 knots.[21] A second trial series from December 2 to 20, 2024, emphasized propulsion refinements and systems interoperability under operational loads.[22] Trials concluded in September 2025 upon arrival in Brest, demonstrating the platform's endurance and stability without major structural issues.[2] Naval Group delivered Amiral Ronarc'h to the French Navy on October 17, 2025, transitioning to operational evaluation trials led by the DGA and Navy crews, with full operational capability projected for summer 2026.[1] [18] Subsequent vessels, including exports to Greece, have followed parallel milestones, with the first Hellenic Navy unit (HS Kimon) initiating trials in May 2025.[23]Technical Design and Capabilities
Hull, Propulsion, and Performance
The hull of the Defence and Intervention Frigate (FDI) measures 122 meters in length, with a beam of 18 meters and a full-load displacement of 4,500 tonnes.[19][5] This design incorporates an inverted bow configuration to improve seakeeping in adverse conditions, enabling sustained operations in high-sea states.[24] Propulsion is provided by a combined diesel and diesel (CODAD) arrangement, utilizing two diesel engines delivering a total output of 32,000 kW.[25][13] This system supports a maximum speed of 27 knots and a cruising speed of 15 knots.[19][9] Performance metrics include a range of 5,000 nautical miles at 15 knots, facilitating extended deployments in remote areas.[5][9] The frigates achieve an endurance of 45 days, supporting multi-mission profiles with high interoperability for joint operations.[19][26]Armament and Weapon Systems
The Frégate de Défense et d'Intervention (FDI) is equipped with a modular armament suite optimized for multi-role operations, including air defense, anti-surface warfare, and anti-submarine capabilities. The primary surface-to-air missile system consists of 16 Aster 15 and Aster 30 missiles housed in two Sylver A50 vertical launch systems (VLS), each with eight cells, providing medium- to long-range interception against aircraft and missiles.[5][27] These missiles, developed by MBDA, enable the FDI to engage threats at ranges up to 100 kilometers with the Aster 30 variant.[2] For anti-surface warfare, the frigate carries eight Exocet MM40 Block 3c missiles, which offer sea-skimming flight profiles and a range exceeding 180 kilometers, suitable for striking coastal and maritime targets.[2][5] The main gun is a Leonardo 76 mm Super Rapid in a stealth cupola, capable of firing 120 rounds per minute with programmable ammunition for versatile engagement of surface, air, and land targets up to 40 kilometers away.[3][28] Anti-submarine armament includes two twin torpedo tubes launching MU90 lightweight torpedoes, effective against submerged threats with advanced acoustic homing and a speed over 50 knots.[2][29] Close-in defense is provided by two Nexter Narwhal 20 mm remote weapon stations, armed with 20 mm cannons for countering small boats, drones, or missiles at short ranges.[2][28] Export variants, such as those for the Hellenic Navy, may incorporate additional capabilities like cruise missiles, but the baseline French configuration prioritizes balanced, scalable firepower without such extensions.[30]Sensors, Electronics, and Digital Integration
The FDI frigate's primary radar is the Thales Sea Fire, a four-panel fixed-array active electronically scanned array (AESA) operating in the S-band, providing 360-degree coverage for air and surface surveillance, target tracking, and fire control without mechanical rotation.[31][5] This system supports simultaneous multi-mission functions, including horizon search, low-altitude tracking, and integration with Aster missile engagements, with testing commencing in 2019 at shore facilities prior to shipboard integration.[32] The combat management system employs Naval Group's SETIS 3.0, which fuses data from sensors, weapons, and external networks for real-time decision-making and automated fire control, featuring a dual-redundant digital core to enhance reliability in high-threat environments.[33] This architecture enables seamless integration of anti-air, anti-surface, and anti-submarine warfare domains, with modular software updates supporting future upgrades without hardware overhauls.[9] Underwater sensing includes Thales hull-mounted and variable-depth sonars, such as the CAPTAS family for towed array operations, delivering active and passive detection capabilities against submarines across littoral and blue-water scenarios.[34] Electronic warfare systems incorporate Thales jammers, decoys, and interceptors like the Sagaie or Dagaie Mk2, coordinated through the SETIS framework for threat identification and countermeasures.[35] Digital integration is foundational to the FDI's design, with a centralized data infrastructure linking platform management, propulsion, and combat subsystems via high-speed networks, enabling predictive maintenance, reduced crew workload, and interoperability with allied forces through standardized protocols.[13] This "digital native" approach, first implemented on a French surface combatant, prioritizes cybersecurity and fault-tolerant computing to sustain operations amid electronic warfare disruptions.[2]Crew Accommodation and Automation Features
The Defence and Intervention (FDI) frigates are equipped to accommodate a core crew of 125 personnel, supplemented by capacity for up to 28 additional passengers, such as aviation or special operations detachments, enabling sustained operations over 45 days at sea.[19][5] This berthing arrangement prioritizes habitability for extended missions, with modular living quarters designed to meet French Navy standards for ventilation, sanitation, and personal space amid the vessel's compact 4,500-ton displacement.[9][13] Advanced automation features significantly mitigate manpower demands, allowing the FDI to operate efficiently with its 125-person complement despite multi-domain combat responsibilities that would traditionally require larger crews on comparable platforms.[36][21] Integrated Platform Management Systems (IPMS) automate propulsion, power distribution, and auxiliary functions, reducing manual oversight and enabling predictive maintenance through real-time diagnostics.[9] The SETIS combat management system further enhances automation via intuitive man-machine interfaces that consolidate sensor data, weapon controls, and decision-support tools into a unified digital environment, minimizing watchstanding requirements across air, surface, subsurface, and asymmetric warfare domains.[9][13] Cyber-secure networking and modular software architectures support remote monitoring and automated fault isolation, contributing to the frigates' projected 3,500-hour annual operational availability while allocating crew resources toward mission-critical tasks rather than routine upkeep.[2] This design philosophy reflects a shift toward "digital native" vessels, where automation offsets crew size constraints without compromising resilience or flexibility in high-threat scenarios.[13][37]Construction and Fleet Composition
Shipbuilding Contracts and Facilities
The primary shipbuilding contract for the Frégate de Défense et d'Intervention (FDI) program was awarded by the French Direction générale de l'armement (DGA) to Naval Group in 2017 for the construction of five frigates for the French Navy.[38] This contract encompasses design finalization, construction, and integration of combat systems, with deliveries scheduled through 2029.[16] Construction occurs at Naval Group's Lorient shipyard in Brittany, France, which has undergone significant modernization to enable serial production rates of up to two FDI frigates per year.[2] The facility supports advanced modular construction techniques, including pre-outfitting of hull sections, to streamline assembly and reduce build times.[1] Keel laying for the lead ship, Amiral Ronarc'h, took place in December 2021, followed by launch in November 2022 and delivery on 17 October 2025.[2] Naval Group's Lorient yard also handles initial construction phases for export variants, such as the three Kimon-class frigates for the Hellenic Navy under a separate 2021 contract, incorporating technology transfer elements like block fabrication at Greek facilities including Salamis Shipyards.[39] This shared infrastructure facilitates economies of scale and standardized production processes across domestic and international orders.[40]French Navy Vessels
The French Navy operates the Frégate de Défense et d'Intervention (FDI) as its intermediate-sized, multi-mission surface combatants, with five vessels ordered under the Amiral Ronarc'h class to replace the aging La Fayette-class frigates.[24] These ships, constructed by Naval Group at the Lorient shipyard, emphasize modularity for anti-air, anti-submarine, and anti-surface warfare, supporting extended deployments in contested zones.[2] The program aligns with France's objective to sustain 15 first-rank frigates by 2030, enhancing fleet versatility amid evolving threats.[28] The lead vessel, Amiral Ronarc'h (D660), was laid down on 17 December 2021 and delivered to the French Navy on 17 October 2025 following sea trials in Brest.[2] Measuring 122 meters in length with a displacement of approximately 4,500 tons, it accommodates 125 crew and features a CODAD propulsion system yielding 27 knots.[33] The remaining ships—Amiral Louzeau (D661), Amiral Castex (D662), Amiral Nomy (D663), and Amiral Cabanier (D664)—are under construction, with deliveries projected through 2032 to complete the series.[27] [14]| Ship Name | Pennant | Builder | Status (as of October 2025) |
|---|---|---|---|
| Amiral Ronarc'h | D660 | Naval Group | Delivered |
| Amiral Louzeau | D661 | Naval Group | Under construction |
| Amiral Castex | D662 | Naval Group | Under construction |
| Amiral Nomy | D663 | Naval Group | Under construction |
| Amiral Cabanier | D664 | Naval Group | Under construction |