1st Submarine Flotilla

The Swedish Navy's submarine arm consists of the 1st Submarine Flotilla based in Karlskrona. The submarine is a uniquely versatile platform capable of operating covertly, hidden in the surrounding water. With their wide range of sensors, submarines can maintain surveillance of large sea areas both on the surface and underwater. Maritime surveillance, intelligence gathering, the landing of special units and carrying out attacks on surface ships or other submarines are just some of the capabilities that the Swedish Navy's submarines possess. In the event of war the submarines can lay mines. With propulsion machinery that does not require an external air supply (Stirling engines), the Swedish submarines are capable of operating submerged for long periods, while at the same time being very difficult to detect.

The Flotilla includes the following:

• Gotland Class submarines,
• Södermanland Class submarines,
• Mini-submarine HMS Spiggen,
• Submarine rescue vessel HMS Belos with the submarine rescue vehicle URF,
• Torpedo recovery vessel HMS Pelikanen,
• Signals intelligence vessel HMS Orion.

The Södermanland Class consists of the submarines HMS Södermanland and HMS Östergötland. They were originally launched in 1987-1990 as two of the four boats in the Västergötland (Vgd) Class. The submarines have been modernized at Kockums, including the installation of the Stirling AIP system. HMS Södermanland was relaunched in 2003 and HMS Östergötland in 2004.

The submarines were cut and lengthened by the insertion of the Stirling AIP section. This section, fully fitted and equipped before installation, contains two Stirling units, liquid oxygen (LOX) tanks and electrical equipment. When the Södermanland Class has been completed, all operational submarines in the Swedish fleet will have Stirling air-independent propulsion - something quite unique among the world's navies equipped with conventional submarines. The fully equipped Stirling AIP section is inserted aft of the tower.

Swedish submarines are designed to operate mainly in colder northern waters. Higher water temperatures can lead to problems with high ambient temperatures and high levels of relative humidity on board. An important aspect of the Södermanland Class conversion is that the submarines will now be equipped to undertake international peacekeeping missions in warmer and more saline waters. In practice this involves fitting the boats with a completely new refrigeration system employing heat exchangers rather than the direct seawater cooling previously used.

The command and control system of the Södermanland Class submarines was updated to the latest standards and the boats' stealth properties are being further refined. The submarines are also equipped with a new air-lock for divers. With the conversion of the Södermanland Class, the Swedish Navy got two practically new submarines capable of operating for the next twenty years without further modernisation.