Home Europe Fifth Royal Navy Astute-class submarine completes first trim dive

Fifth Royal Navy Astute-class submarine completes first trim dive

HMS Anson trim dive trial
Photo: BAE Systems

The Royal Navy’s fifth Astute-class submarine, future HMS Anson, achieved an important milestone on its path to the fleet by completing its first trim dive.

Under the control of its Royal Navy crew, Anson completed the dive in the Devonshire Dock, submerging completely beneath the surface of the water while crew tested on-board systems.

BAE Systems, the boat builder, says the successful exercise “proved the safety and stability of the 7,400-ton, 97 meter-long attack submarine.”

A ‘trim dive’ is done to complete a number of tests. The most important is to help engineers establish the vessel’s center of gravity and precise weight.

More than 60 crew members were on board as part of the exercise, which saw 16 tons of ballast, split across four trollies, taken aboard to assist in testing the vessel’s stability. As the submarine dives to a depth of 15 meters, the trollies are moved across the vessel so naval architects can confirm the stability of the vessel at sea.

Commanding Officer of Anson, Commander David ‘Bing’ Crosby, said: “The trim and basin dive is a key step in the commissioning of HMS Anson. This period will enable us to set the boat’s internal weight, prove her water-tight integrity, test sensors and put some of our systems through their tests ahead of sailing for the first time.

The trial was completed a little under a year after the submarine was launched in April 2021. The submarine was officially named at a ceremony in December 2020, after the 18th Century Admiral George Anson who delivered victory over the French at Cape Finisterre in 1747 and went on to reform the Admiralty. HMS Anson is the first submarine to bear the name, while eight naval vessels previously carried the name.

The Royal Navy expects to have a total of seven Astute-class submarines in service by 2026. The boats feature advanced nuclear technology which eliminates the need for the to ever be refueled. Crewed by 98 submariners, they carry both Tomahawk Land Attack Cruise Missiles (TLAM) and Spearfish heavyweight torpedoes.

“The successful trim dive of Anson is a significant milestone in the submarine’s test and commissioning phase. It demonstrates the continued successful collaboration between BAE Systems, the Submarines Enterprise, and our suppliers on delivering this national endeavor for the UK Royal Navy,” BAE Systems Submarines Astute program director, John Moorby, said.