WASHINGTON — The U.S. Navy will end its work with Raytheon Technologies developing a sonar for littoral combat ships and frigates and will instead buy a sonar already in use by several navies around the globe.

Raytheon’s AN/SQS-62 Variable Depth Sonar, also called the Dual-mode Array Transmitter, was a key component of the LCS anti-submarine warfare mission package and was going to be carried into the Constellation-class frigate program to create commonality within the surface force.

But the sonar, though it had succeeded in tracking a submarine in test events, still had two remaining technical challenges: the hydrodynamic stability of the system that trails behind the ship, and the performance and reliability of the transducers.

Defense News previously reported the program office paused testing in September after realizing the hydrodynamic issues would require an active control system.

Program Executive Officer for Unmanned and Small Combatants Rear Adm. Casey Moton told Defense News on March 31 that around the same time the Navy became increasingly concerned about the risk this presented to the sonar development and whether the product would be a viable option for future ASW operations.

Coincidentally, the Navy was nearing a decision point with Fincantieri Marinette Marine on the final design of the frigate, as the ship’s critical design review and production readiness review are coming up.

“It really came down to our concern about the risk with the DART system … and risk to the design progress for frigate, and ultimately further on potentially down to if we got into production and had issues, production impact, performance impact,” Moton said in a phone interview.

At the same time, the Navy was considering cutting the number of LCS hulls in the fleet as part of cost-saving measures in the fiscal 2023 budget request. The service decided to nix the ASW mission package altogether, reducing the number of hulls needed to carry out the other two missions: surface warfare and mine countermeasures.

“As a result of increased risk and challenges experienced with the variable depth sonar,” the Navy released a sources sought notice in early February, Moton said.

After assessing the options, the service selected the CAPTAS-4, or Combined Active Passive Towed Array Sonar. The product is made by Advanced Acoustics Concepts, a joint venture between Leonardo DRS and Thales Defense & Security.

The rear admiral said CAPTAS-4 was chosen in part due to its proven performance in international navies and its high technical readiness, lowering the risk in integrating it into the Navy’s own undersea warfare combat system and frigate hull design.

Moton said that when shipbuilders were competing for the frigate design and construction contract Fincantieri won in 2020, they were allowed to pick between incorporating a hull-mounted sonar or the variable depth sonar towed along behind the ship.

While the shipbuilder could select the style of sonar they wanted — with Fincantieri electing the VDS — the Navy reserved the right to dictate the system the builder would use. Raytheon’s DART was previously the Navy’s VDS of choice so it could achieve the cost savings in production, training and sustainment associated with having common systems across multiple ship classes, Moton said.

But, he said, the Navy had worked with Raytheon to engineer, model and ultimately test several improvements to address the lingering technical problems with DART.

“In those tests, we did not see the improved performance that we had been anticipating, and so it became clear that it was going to be more complex to solve than our initial round of efforts,” he said.

Moton said Fincantieri supported the decision to move to a different sonar and helped look at the alternatives offered in responses to February’s sources sought notice.

Moton declined to say how many companies offered up sonar solutions, other than to say Raytheon’s DART was considered the incumbent and “several other” products were considered.

Thales’ website notes the CAPTAS-4 is fielded on the French and Italian FREMMS — the Fincantieri frigate design that serves as the parent design for the Constellation-class FFGs — as well as British Type 23 and Type 26 frigates, Chilean Type 23 frigates and Spanish F110 frigates.

Moton said the U.S. Navy had some familiarity with the system from working alongside these allies in Europe, as well as through using the related Thales Airborne Low Frequency Sonar as a dipping sonar for the MH-60 Sea Hawk helicopters.

He said the sources sought notice asked companies to explain the technical maturity of the sonar, its performance and reliability in past at-sea operations, its integration on other ship classes, its potential integration into the SQQ-89 undersea warfare combat system and how well its production schedule would match that of the Constellation frigate line, among other questions.

Moton said Advanced Acoustics Concepts and Fincantieri would still have to negotiate the price of the sonar, but he doesn’t expect the change to significantly affect the program cost. Similarly, he said the Navy would have to conduct integration work between the sonar and the combat system, but he didn’t expect that cost to be significantly different than planned.

Capt. Kevin Smith, the frigate program manager, said during the call that, with the new sonar selected to help reduce risk on the program, the frigate could move into its critical design review and production readiness review soon. Those milestones were previously expected to occur in the second quarter and third quarter, respectively, of FY22.

“We’re not going to start [production] unless we feel we have a mature design so we don’t relive some of the challenges we’ve had with lead ship construction. I expect we will still have challenges, because lead ships are very hard, but we’re trying to mitigate that as much as we can with a mature design,” he said.

Megan Eckstein is the naval warfare reporter at Defense News. She has covered military news since 2009, with a focus on U.S. Navy and Marine Corps operations, acquisition programs, and budgets. She has reported from four geographic fleets and is happiest when she’s filing stories from a ship. Megan is a University of Maryland alumna.

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