Life-of-type extension for RAN's Collins subs will not include AIP system

An air-independent propulsion (AIP) system will not be installed in the Royal Australian Navy's (RAN's) six Collins-class submarines as part of their future ‘Life-of-Type Extension (LOTE)' programme, Commodore Tom Phillips, the RAN's Director-General of Submarines, disclosed on 9 November.

Addressing a conference in Adelaide organised by the Submarine Institute of Australia, Cdre Phillips said such a system works well for countries that deploy submarines for short distances to their operational areas.

However, “If you put AIP into a [conventionally-powered] submarine, you necessarily either make the submarine larger, which reduces range and endurance, or you keep the submarine the same size and reduce battery and fuel capacity, which again affects endurance and range”, he noted.

Modelling had found the optimum for Australian circumstances was diesel-electric propulsion. “Even better than that would be nuclear propulsion. Based on that, AIP will not be in the LOTE going forward,” said Cdre Phillips.

His remarks follow speculation that installing an AIP system would enhance the stealth capabilities of the Collins-class fleet, given the type's range of around 10,000 n miles (18,500 km) and endurance of around 70 days, enabling it to deploy, remain on station, and return from areas of operational interest in Northeast and Southeast Asia.

The two-year per boat LOTE activities, scheduled to begin with HMAS Farncomb in 2026, will extend the life of the Collins-class through to 2048, or later if required, prior to the anticipated arrival of nuclear-powered submarines to be acquired via the AUKUS tri-partite security pact between Australia, the United Kingdom, and the United States announced in September.