Challenger-class submarine

The Challenger class is one of the submarine classes of the Singapore Navy. They are extensively modernized versions of ex-Sjöormen class submarines.

History
In 1995, the RSN acquired a Challenger class (formerly known as Sjöormen class) submarine from the Swedish Navy and another three in 1997, making them Singapore's first underwater platforms. It is believed that the Challenger class were purchased to develop the required submarine operations expertise before selecting a modern class of submarines to replace them, since all the boats are over 40 years old.

Modernisation
The Challenger class submarines have undergone the Riken modernisation programme tailored to the specific operational conditions of the Singapore Navy. As the submarines were designed by the Swedish for operations in the Baltic Sea, various modifications were required to suit them to tropical waters. A comprehensive tropicalisation programme was carried out for all four submarines, which involved installing air conditioning, marine growth protection systems and corrosion-resistant piping.