US and UK Navies to sink Cold War frigate USS Klakring in Atlantic Thunder 26 joint live-fire exercise.

The British Royal Navy and the U.S. Navy are preparing to sink the decommissioned Oliver Hazard Perry-class frigate USS Klakring (FFG-42) during Atlantic Thunder 26 (AT26) off north-west Scotland between September 17 and 21, 2026. The live-fire exercise tests surface warfare kill chains and weapon effectiveness against a complex, highly compartmentalized 4,200-tonne combat ship hull. Unmanned underwater vehicles will subsequently conduct high-resolution surveys at depths exceeding 1,900 meters to evaluate structural failure, blast propagation, and progressive flooding.

The Atlantic Thunder 26 sinking exercise targets a 138-meter-long hull frigate featuring multi-compartment reserve buoyancy, a single propulsion shaft, and a reinforced military architecture. Exercise objectives combine multi-domain anti-surface strikes with post-sinking seabed exploitation to collect empirical data on cumulative weapon impact and hull-girder integrity.

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The USS Klakring (FFG-42) was the 32nd Oliver Hazard Perry-class guided-missile frigate built for U.S. Navy service, commissioned on August 20, 1983, and decommissioned on March 22, 2013. (Picture source: US Navy)

According to Navy Lookout on August 19, 2026, the British and American navies are preparing to sink the decommissioned Oliver Hazard Perry-class frigate USS Klakring (FFG-42) during Atlantic Thunder 26 (AT26), a live-fire exercise scheduled for September 17-21 at the QinetiQ Hebrides range off north-west Scotland after its postponement from May. The target is a 138 m-long, 14 m-wide frigate displacing 4,100 long tons, or 4,200 tonnes at full load, with a 6.7 m draft. The USS Klakring was commissioned on August 20, 1983, decommissioned and stricken on March 22, 2013, then retained at the Naval Inactive Ship Maintenance Facility in Philadelphia before being moved down the Delaware River on August 12, 2026, for its Atlantic crossing, initially toward Campbeltown.

The exercise will not end when the frigate disappears below the surface; the USS Klakring is expected to settle at a depth exceeding 1,900 m, where unmanned underwater vehicles (UUVs) will conduct high-resolution surveys of the wreck to determine its final orientation, hull condition, and visible weapon damage after impact, progressive flooding, descent, and seabed contact. That sequence makes AT26 a combined strike, sinking, and post-strike exploitation event rather than a simple weapons firing against a disposable target. The USS Klakring (FFG-42), a full-size Cold War escort ship. was ordered on April 27, 1979, laid down by Bath Iron Works on February 19, 1982, launched on September 18, 1982, and commissioned on August 20, 1983.

The ship measures 138 m overall, with a 14 m beam, a 6.7 m draft, and a full-load displacement of 4,200 tonnes. Propulsion consisted of two General Electric LM2500-30 gas turbines producing 41,000 shp (31 MW) combined, driving a single shaft and variable-pitch propeller. Maximum speed exceeded 29 knots, while endurance was 5,000 nautical miles at 18 knots, equivalent to more than 11.5 days of continuous steaming at that speed if fuel were the only constraint. Two retractable 350 hp (260 kW) electric azimuth auxiliary propulsion units supported docking and low-speed maneuvering. The ship normally carried 15 officers and 190 enlisted sailors, while the embarked SH-60 helicopter detachment added six officer pilots and 15 maintainers, bringing the total to about 226 personnel.

For the SINKEX, the important point is not simply that the target weighs 4,200 tonnes, but that its reserve buoyancy is distributed across a multi-compartment hull, so local penetration alone does not guarantee sinking unless enough watertight volume is lost or structural integrity is degraded beyond recovery. The Oliver Hazard Perry-class layout makes the USS Klakring especially relevant for studying cumulative damage because the class combined a narrow 14 m beam, a relatively high internal density, and an extensive compartmentation within a relatively short hull. Moreover, the USS Klakring belongs to the long-hull variant, developed to accommodate the SH-60B Seahawk LAMPS III rather than the smaller SH-2 Seasprite used by earlier short-hull ships.

The aviation section incorporated two helicopter hangars and the RAST hauldown system, allowing the SH-60B to be secured to the deck and moved into the hangar under higher pitch-and-roll conditions than would otherwise be practical. The machinery arrangement used two LM2500 turbines but only one propulsion shaft, concentrating the final drive into a single variable-pitch propeller and creating a different survivability problem from twin-shaft frigates and destroyers. At the same time, the hull enclosed propulsion machinery, generators, magazines, combat system rooms, crew spaces, fuel tanks, aviation spaces, and a large stern flight deck. The class has already demonstrated substantial damage tolerance under combat conditions. The USS Stark remained afloat after two AM39 Exocet impacts on May 17, 1987, despite 37 fatalities, while the USS Samuel B. Roberts survived a mine strike on April 14, 1988, and remained afloat after two days of firefighting and flooding control before later returning to service.

These cases are useful benchmarks because they show that catastrophic local damage to a Perry-class frigate does not necessarily translate into immediate sinking, making the number, location, spacing, and sequence of hits central to determining how quickly buoyancy and longitudinal strength are lost. The USS Klakring's former weapons and sensors also indicate how much internal volume and structural support was originally devoted to combat functions. Air surveillance was provided by the AN/SPS-49, surface search by the AN/SPS-55, and the Mk 92 fire control system used CAS and STIR radar components for weapon guidance and tracking. Underwater detection included the AN/SQS-56 sonar, while the electronic warfare fit included the AN/SLQ-32. The principal missile installation was a Mk 13 Mod 4 single-arm launcher linked to a 40-round magazine carrying SM-1MR Standard and Harpoon missiles.

Gun armament comprised one OTO Melara Mk 75 76 mm/62-calibre gun, one 20 mm Phalanx CIWS and four 12.7 mm machine guns, while two Mk 32 triple 324 mm launchers carried Mark 46 anti-submarine torpedoes. The aviation facilities supported two SH-60 LAMPS III helicopters, giving the ship an embarked anti-submarine and surveillance element in addition to its organic hull-mounted sonar. The Mk 13 system began disappearing from active U.S. Navy Perry-class frigates in 2004-05, removing both the SM-1MR launcher and the ship's Harpoon capability, but the structural features associated with that earlier combat fit remained part of the hull. Former magazine spaces, equipment foundations, bulkheads, cable routes, deck penetrations, and machinery compartments create a much more realistic environment for blast propagation, fragment travel, and flooding than an empty target hull of comparable external dimensions. 

The USS Klakring was also heavily used during its service life. Its first overseas deployment began on June 7, 1985, taking the ship through the Mediterranean, Suez Canal, and Red Sea into the Persian Gulf. During that deployment, temperatures reached 117°F (47°C) with 90% humidity, while the embarked SH-60B averaged two sorties per day. In 1987, the USS Klakring returned to the Gulf during Operation Earnest Will, when the United States escorted reflagged Kuwaiti tankers through the Strait of Hormuz and Persian Gulf during the Iran-Iraq War's Tanker War. On August 30, 1987, the frigate escorted the Bridgeton, formerly Al Rekkah, through the Strait of Hormuz after the tanker had struck an Iranian mine on July 24 and survived. The USS Klakring subsequently conducted Mediterranean operations, NATO exercises, Caribbean law enforcement missions, and multinational deployments around Latin America.

It participated in UNITAS 41 from August to November 2000, including a circumnavigation of South America, and later operated in the Mediterranean, Black Sea, Latin America, and western Indian Ocean. From commissioning to decommissioning, the ship accumulated 29 years and seven months of active service, followed by more than 13 years in inactive status before its August 2026 movement. That matters structurally because the target has experienced decades of hull flexing, propulsion vibration, thermal cycling, maintenance periods, and localized repairs before entering reserve. Atlantic Thunder 26 (TA26) also permits a comparison with Atlantic Thunder 22 because the 2022 target, the ex-USS Boone (FFG-28), belonged to the same Oliver Hazard Perry class. The USS Boone was subjected to a sequence of different weapon types from multiple launch points, giving the 2022 event value as a baseline for cumulative damage against a comparable hull.

A Royal Navy Wildcat helicopter fired Martlet missiles, the HMS Westminster launched the Royal Navy's final Harpoon missile, the USS Arleigh Burke (DDG-51) fired SM-6s, and a U.S. Air Force F-15E Strike Eagle delivered maritime JDAMs. Those weapons imposed different attack geometries and damage mechanisms: The Martlet used a much smaller warhead than the Harpoon, the SM-6 approached the engagement with a high-energy missile, and JDAMs added heavy air-delivered explosive effects. The value of the USS Klakring is therefore not simply that another frigate will be sunk, but that a second long-hull Perry can be subjected to a new attack sequence four years later while keeping hull family, displacement class, beam, propulsion layout, and much of the internal architecture broadly consistent. That reduces one major source of variation when comparing the effects of different weapon combinations.

The target choice is also significant because several retired Royal Navy frigates were available at the time: HMS Monmouth departed for Turkey in April 2025, HMS Westminster followed in July 2026, and HMS Northumberland was scheduled to leave in September, showing that the USS Klakring was selected despite an existing British inventory of decommissioned frigate hulls. The post-sinking survey is likely to produce some of the most useful engineering information from AT26 because the USS Klakring is expected to come to rest at more than 1,900 m (6,200 ft), where diver inspection is not feasible. UUVs will have to locate the wreck, determine whether it rests upright, on its side, or in a broken configuration, and image the hull at sufficient resolution to identify major openings, torn plating, collapsed superstructure, separated structural members, and possible breaks in the hull girder.

The exercise will include long-endurance UUVs, low-signature vehicles, autonomous and AI-enabled mission functions, high-resolution scanning, novel launch-and-recovery methods, and communications suited to limited-bandwidth underwater operations. At 1.9 km depth, acoustic communications offer far lower data rates and much higher latency than radio links used by surface or airborne systems, so underwater vehicles must execute significant portions of the survey autonomously and store large imagery datasets onboard. The resulting survey can help separate primary weapon damage from secondary damage that occurred after the ship began to flood. A missile may open compartments or weaken major structural members, while later bending loads during sinking, implosion of internal spaces, impact with the seabed, or collapse of the superstructure can produce additional fractures that were not caused directly by the strike.

Mapping the final wreck against the recorded impact sequence therefore gives investigators a better basis for identifying which weapon effects contributed directly to mission kill, loss of buoyancy, and structural failure. A SINKEX (sinking exercise) is most useful when treated as a controlled destructive experiment rather than as a demonstration of whether a missile can hit a stationary ship. Before firing begins, the target must be stripped of substances that could create unacceptable environmental contamination, including liquid PCBs from electrical equipment, petroleum from tanks and pipework, mercury, fluorocarbon material, refuse and items capable of floating away after sinking.

Once prepared, a frigate such as the USS Klakring offers a target with several decks, numerous watertight compartments, fuel and machinery spaces, former magazines, aviation facilities, structural bulkheads and longitudinal framing. This allows the exercise to measure more than weapon accuracy. The sequence can show whether one hit remains confined to a local compartment, whether blast ruptures adjacent boundaries, how quickly flooding spreads, whether repeated impacts destroy watertight integrity, when reserve buoyancy falls below a sustainable level, and whether accumulated damage produces hull-girder failure before or during sinking.

It also tests the operational chain that precedes impact, including target detection, identification, track generation, transfer of targeting data between units, assignment of individual weapons, timing of attacks from ships and aircraft, and post-strike assessment. Atlantic Thunder 26 extends that process below the surface by inspecting the target after it settles beyond 1,900 m depth, creating a rare opportunity to compare the known weapon sequence with the actual physical end-state of a full-size frigate hull.

Written by Jérôme Brahy

Jérôme Brahy is a defense analyst and documentalist at Army Recognition. He specializes in naval modernization, aviation, drones, armored vehicles, and artillery, with a focus on strategic developments in the United States, China, Ukraine, Russia, Türkiye, and Belgium. His analyses go beyond the facts, providing context, identifying key actors, and explaining why defense news matters on a global scale.

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