A manufacturing issue, not a design flaw, led to a six-inch crack along a weld seam on the hull of Littoral Combat Ship, USS Freedom, during heavy weather trials in February, Navy officials said today.
"We're still reviewing the design for weld improvements, as far as the analysis of [what led to the crack] we've completed the analysis and are in the process of working through the release of that information," said Capt. Jeff Riedel, the Navy's LCS program manager during a briefing at the Navy League's annual Sea, Air Space conference held just outside of Washington DC. "Both Lockheed and the Navy are going through their final review that should be available in the next couple of weeks."
He went on to say that ship's design wasn't at fault, but instead, a weak weld-job led to the cracks.
"The design is adequate, how I build it is a different story," said Riedel. "If I was able to weld it as it was designed to be welded, it wouldn't have been an issue. The real issue was, getting access to that area to be able to do the weld."
He added that beginning with LCS-3, welders are able to more easily reach the spot on the ship where the crack occurred, allowing them to lay an extra thick weld.
Other cracks were discovered in known stress points in the ship's superstructure that computer modeling predicted might be the location of cracks during rough seas, according to Riedel. These cracks have led to design tweaks in subsequent ships of the class.
"We modeled the superstructure and we found that we had areas that were high stress areas, so we would expect, potentially, a crack to occur in that high-stress area," said Riedel. "So we instrumented the superstructure and we used that instrumentation to validate the model and in fact, we're now using that to better the design...for LCS-3 and following we've gone back and changed the design so we can reduce those stress areas."
Navy Secretary Ray Mabus said later in the day that all lead ships of a class have "issues" and noted that the crack hasn't delayed sea trials for the ship.
"Things happen on every lead ship, what you do is learn how to avoid it on the following ships, which we have done," said Mabus during a press briefing at the conference.