USS St. Louis littoral combat ship makes U.S. Navy history with first engine repair at sea.

The U.S. Navy’s Freedom-class littoral combat ship, USS St. Louis (LCS 19), has completed its first self-sufficient engine repair at sea, restoring propulsion without the need for contractor assistance.

The Freedom-class littoral combat ship USS St. Louis (LCS 19) has achieved a first-of-its-kind milestone by completing a self-sufficient engine repair at sea, according to the U.S. Navy. On August 21, 2025, while deployed in Tampa Bay, the crew restored propulsion without contractor support, allowing the ship to remain on mission without returning to port. The Navy said the breakthrough highlights ongoing efforts to make Freedom-class ships more resilient and less dependent on shore-based maintenance, a key factor for operational readiness.
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The crew-led repair restored propulsion without contractor assistance, allowing the USS St. Louis to remain on mission during counter-drug operations and partner exercises in the U.S. Second Fleet. (Picture source: Fincantieri Marine Group)

The repair was executed after several hours of diagnostic work, corrective actions, and operational testing by the ship’s engineering team. The supply department played a critical role by coordinating the rapid delivery of required spare parts and equipment, which allowed the enginemen to complete the repair within the deployment timeline. The chief engineer of St. Louis stated that sailors were able to apply training and technical knowledge to return the engine to operational condition without external intervention. The commanding officer added that the Freedom-class design had originally envisioned heavier reliance on off-hull personnel, but the Navy’s current approach is to increase onboard capacity so preventive and corrective maintenance can be performed when needed.

The US Navy links this milestone to a two-year effort to pre-position high-demand spare parts on board Freedom-variant ships and to provide additional training aimed at reducing dependence on shore facilities. Squadron leaders report that every successive Freedom deployment over this period has produced greater operational availability, with more capable ships being delivered to Fleet Commanders. The commodore of Littoral Combat Ship Squadron Two emphasized that this approach is allowing deployed units to conduct missions in the Second and Fourth Fleets while freeing other surface assets for different global tasks. USS St. Louis, currently deployed with an embarked Coast Guard Law Enforcement Detachment, is engaged in counter-illicit drug trafficking operations and partner exercises in the U.S. Second Fleet area. By restoring propulsion capability at sea, the ship avoided schedule disruption and preserved its assigned mission set.

The operational meaning of this repair is that it illustrates a shift in the Navy’s broader maintenance strategy. By carrying out diesel engine repairs at the lowest capable level, deployed units can resolve propulsion issues without leaving station, which supports continuity of tasking and reduces knock-on effects on escorts, logistics, and port infrastructure. Navy maintenance policy continues to rely on Regional Maintenance Centers and industry partners for more complex casualties, but the intent is to push as much work as possible to the ship’s force. Industry initiatives, such as compressed overhaul “pit stop” models for Colt-Pielstick engines on amphibious ships, are also part of the effort to reduce time in dock. Cases like the in-situ machining required for USS Pearl Harbor after a journal bearing failure show that specialized vendor procedures remain necessary, but they are being reserved for tasks beyond shipboard scope. The combination of crew-led repair at sea and industrial-level innovations is designed to stabilize employment cycles and reduce unplanned downtime across surface forces.

USS St. Louis is a Freedom-class littoral combat ship built by Marinette Marine in Wisconsin. The ship was laid down on 17 May 2017, launched on 15 December 2018, and commissioned on 8 August 2020. It is the seventh U.S. Navy ship to carry the name St. Louis and is assigned to Littoral Combat Ship Squadron Two. At full load, the ship displaces approximately 3,500 metric tons, measures 115.3 meters in length with a beam of 17.5 meters, and has a draft of 4.0 meters. Propulsion is provided by two Rolls-Royce MT30 gas turbines and two Colt-Pielstick diesel engines driving four waterjets, delivering speeds of over 45 knots and a range of about 3,500 nautical miles at 18 knots. Electrical power comes from four Isotta Fraschini V1708 diesel generators rated at 800 kW each, and endurance is estimated at 21 days.

The Freedom class is designed around modularity and includes a large mission bay, a flight deck, and hangar space for MH-60R/S Seahawks and MQ-8 Fire Scout unmanned helicopters. Baseline armament consists of a Mk 110 57 mm naval gun, Rolling Airframe Missiles, and .50 caliber machine guns, with options to add 30 mm Bushmaster cannons and other weapons in mission packages. The class has received incremental updates based on early deployment experience, including the rotating TRS-4D AESA radar on later hulls. The Navy has also addressed propulsion-train vulnerabilities through a combined gear modernization program, which has been applied to USS St. Louis and subsequent ships. These measures provide context for the importance of restoring diesel propulsion at sea, as reliable engines remain central to maintaining mission capability for this class.

The operational role of USS St. Louis and its sister ships includes maritime security, interdiction, counter-illicit trafficking, and exercises with partner nations in littoral environments. The ability to restore propulsion capability at sea reinforces this role by avoiding interruptions that would have previously required port access or contractor intervention. For the Navy, the broader meaning is that each verified shipboard repair contributes to greater predictability in deployments and reduces pressure on industrial maintenance facilities. By combining crew-level repair capacity with selective industrial upgrades, the Navy aims to achieve steadier availability across small combatants and amphibious platforms, supporting distributed maritime operations with fewer delays caused by propulsion casualties.

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, 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.