The U.S. Naval Institute (USNI) News reported that, the U.S. Navy has determined a flaw in the Freedom-class Littoral Combat Ship’s combining gear, a complicated gearing mechanism that links the engines of the ship, is an engineering defect that shipbuilder Lockheed Martin now has to fix. The U.S. Navy has linked propulsion failures in USS Detroit (LCS-7) and USS Little Rock (LCS-9) to a latent engineering defect in the bearings system that links the ship’s Rolls Royce MT30 gas turbines and the ship’s Colt-Pielstick diesel engines, which power the main drive shaft to achieve the ship’s 40-knot top speed.
As part of the defect determination, Lockheed Martin has been notified by the Navy that the service would not accept delivery of additional Freedom-class hulls until the company fixed the problem in the design, and that the company is responsible for the fix. Over a period of time, the bearings wear faster than anticipated and result in a failure of the combining gear. The problem was independent of the software glitch that resulted in the damage of the propulsion plant of USS Milwaukee (LCS-5) in 2015 or operator error that led to the damage of a different combing in gear on LCS USS Fort Worth (LCS-3). In a statement, Lockheed Martin said it was committed to a fix for the program.
Following the land-based testing, the Navy will likely test the fix at sea with the future Minneapolis-Saint Paul (LCS-21). Minneapolis-Saint Paul and Cooperstown (LCS-23) completed acceptance trials last year and both ships will remain in Wisconsin until their combing gear fixes are complete. Both ships will also undergo additional work that was slated for the ships’ post-delivery maintenance periods at their planned homeports in Mayport, Fla., to minimize delay in getting the ships operationally ready. The delay will also mean Minneapolis-Saint Paul will likely miss its planned commissioning ceremony in Duluth, Minn., scheduled for May.
While the U.S. Navy and the companies know what to fix, they are now figuring out how to most efficiently access and replace the gearing mechanism found deep in the ship. Lessons learned from the initial repairs after the combining gear failures on Detroit and Little Rock have shown that the repairs can happen without having to put the ships in a dry dock; instead, the repair yard could build a cofferdam around part of the hull that needs to be cut and then navigate through the piping and wiring to get to the gear. Lockheed Martin is also testing a method the company developed internally that would allow the repair to occur without cutting into the hull of the ship and could save months on the process
