Group : Attack Submarines
Status : Active
Also Known As : Archer (Republic of Singapore Navy), Sodermanland, Type A-17
Origin : Sweden
Contractor : Howaldtswerke-Deutsche Werft GmbH
Initial Operational Capability (IOC) : 1987
Total Production : 4

The Vastergotland class was introduced in 1987 by the Swedish Navy to perform attack missions in the coastal environment of the colder northern waters. Four boats of this class were procured between 1987 and 1990. Currently, only the last two ships remain in active service. Due to a modernization program applied to the remaining boats the class has been re-named Sodermanland. The Sodermanland class submarines have a stretched hull compared to Vastergotland class among other improvements.

The Sodermanland comprises the HMS Sodermanland and HMS Ostergotland boats which have been fitted with Stirling Air Independent Propulsion system. The Stirling section adds 12 meters to the submarine length and is installed aft of the boat's tower. The first boat will undergo the modernization program in 2003 and the second boat in 2004. In July 2004, Kockums announced that both ships were ready for operational service with the Swedish Navy acceptance of these ships expected by autumn 2004.

A state-of-the-art command and control system was added to the weapon system and stealth characteristics have been improved for enhanced survivability. The Sodermanland-class, like the Vastergotland-class, has 6 533mm torpedo tubes and 3 400mm torpedo tubes and can accommodate up to 18 torpedoes or 22 mines.

In addition to the Stirling AIP, the Sodermanland submarines have been fitted to undertake missions in warmer and more saline waters than those surrounding Sweden. This goal has been achieved replacing the refrigeration system by an entirely new one. That seems to be clearly aimed at performing international peacekeeping missions. Kockums hopes that updated Sodermanland-class boats will remain in service for the next 20 years.

The Ostergotland submarine equipped with Stirling AIP-air independent propulsion system was delivered to the Swedish Navy in October 2004.

Singapore's Ministry of Defense signed an agreement with Kockums for the supply of two Vastergotland-class submarines to the Republic of Singapore Navy on 4 November 2005. Under the terms of the contract Kockums would deliver the two boats retrofitted for operation in tropical waters.

In January 2006 the Swedish Defense Materiel Administration (FMV) awarded Saab a contract for the supply of four SESUB 960 command and control systems to the Swedish Navy's Gotland and Sodermanland submarines. SESUB 960 were designed to provide network-based defense capabilities. In addition, the order also included improvements to the navigation system, sensor management and weapons handling as well as a crew training facility on land.