WASHINGTON — The U.S. Navy has halted deliveries of Lockheed Martin’s Freedom-class littoral combat ship, citing a design flaw with the ship’s transmission.

In a statement to Defense News, the Navy pointed to “a material defect” with the ship’s combining gear, a complex transmission that transmits power generated by the ship’s engines to its waterjet propulsion system, and said it is working to design a fix for in-service littoral combat ships while holding off on taking delivery on new ships.

The Freedom LCS was designed by Lockheed Martin and built by Fincantieri’s Marinette Marine shipyard. The combining gear with the defect was designed by the German firm RENK AG. The Navy, Lockheed and RENK AG have worked together on a fix, which will likely take months to install for each ship, according to a senior Navy official who spoke on condition of anonymity.

The acknowledgement of the design flaw — early failure of the ship’s high-speed clutch bearings — confirms the Navy’s suspicions first reported by Defense News in December. Navy officials have expressed confidence, however, that the service is on a good path to fixing the defect and getting the ships to a useful place.

In a statement, the Navy said it is working to ease the burden on commanders and enable them to still make use of the ship, even as the Navy works through the process of testing the proposed fix.

“A design fix has been developed and is in production, to be followed by factory and sea-based testing,” a Navy statement read. “The Navy is determining the plan to install this fix on ships in the Fleet.

“The fix will be installed and tested on new construction ships prior to the Navy taking deliveries of those ships. Measures have been implemented to mitigate risk to the in-service Freedom variant ships while the Navy moves swiftly to correct the deficiency and minimize operational impacts.”

The modified combining gear will be tested at the RENK AG factory and on a new ship at sea before it is accepted, said Rear Adm. Casey Moton, the head of the unmanned and small combatants office at Naval Sea Systems Command.

“The planned redesign of the defective bearings will be rigorously tested both on land at the manufacturing facility and at sea on a new construction ship before it is accepted and installed in-service,” Moton said in a statement.

The Navy told Lockheed Martin it believes the combining gear issue was a “latent defect,” meaning the service expects the company will be responsible for the repairs, according to a senior Navy official. Lockheed has not yet responded to the the Navy and no agreement has yet been reached over how those repairs will be paid for.

But just how much those repairs will cost is not yet know, said Capt. Danny Hernandez, spokesman for the assistant secretary of the Navy for research, development and acquisition.

“The cost of the repair will be determine once a government-approved solution has been identified,” Hernandez said.

Lockheed Martin said in a statement that it is committed to fixing the combining gear issue.

“In partnership with the U.S. Navy, Lockheed Martin is aggressively pursuing a resolution to the gear issue the Freedom-variant Littoral Combat Ship is currently experiencing,” the statement read.

The Navy has put out a class advisory on the Freedom variant, which restricts some operations of the ship. But a source familiar with the issue told Defense News that as designed, it can operate up to 34 knots even with restrictions in place in various configurations. The advisory restricts certain configurations that put stress on the failing clutch bearings, two sources confirmed to Defense News.

The Freedom-class LCS has been bedeviled by issues with its combining gear, which is arguably an imperfect solution engineered to meet the 40-knot-plus speed requirement.

The string of combining gear casualties dates back to at least late 2015, when the LCS Milwaukee broke down on its maiden voyage to its home port in Mayport, Florida, and had to be towed into the Little Creek base in Hampton Roads, Virginia. Early the next year, the LCS Fort Worth suffered a casualty to the combining gear in port when sailors accidentally ran the system without lube oil running through it.

The early issues, however, are likely not the same as the clutch bearing failures that prompted the Navy to halt deliveries, however.

Early in 2020, LCS-9 (USS Little Rock) suffered a breakdown of its combining gear, which was followed in October by the casualty to LCS-7 (USS Detroit). Detroit was forced to hobble back to port from a deployment to Latin America, but a power failure en route, forcing the Navy to have it towed to port.