Armidale-class

The Armidale class was developed to replace the Fremantle-class patrol boats. A 1993 joint project with Malaysia was cancelled after Malaysia withdrew, leading to the 1999 reopening of the replacement program under procurement project SEA 1444. In December 2003, the Royal Australian Navy (RAN) selected a proposal from Austal and Defence Maritime Services based on an enlarged version of the Bay-class patrol boat. Fourteen vessels were constructed by Austal at Henderson, Western Australia, between 2004 and 2007.

The vessels feature an aluminum alloy, semi-displacement vee hull. Design standards followed Det Norske Veritas specifications for high-speed light craft and specific RAN requirements. To facilitate seakeeping, the class incorporates hydraulic stabilizer fins and trim tabs. Propulsion is provided by diesel engines driving twin shafts. The class originally utilized a multi-crewing system, organized into four divisions, to maximize time at sea. Personnel accommodations include four-berth cabins for junior sailors and smaller shared or individual cabins for senior staff. A separate auxiliary compartment was included for transporting additional personnel. Onboard systems include surface search and navigation radar, electro-optical detection, and radar warning equipment. Boarding operations are conducted using two rigid-hulled inflatable boats launched from dedicated davits.

Based in Darwin and Cairns, the Armidale class was operated by the Australian Patrol Boat Group. Primary roles included border protection, fisheries enforcement, and intercepting unauthorized maritime arrivals under Operation Resolute and Operation Sovereign Borders. In 2017, vessels were deployed to the Sulu Sea for counter-terrorism patrols with the Philippine Navy.

Throughout their service life, the ships encountered technical issues, including fuel system contamination, gas accumulation in the auxiliary compartment, and hull fracturing attributed to high operational tempo and design factors. These issues led to a mid-life refit program in Singapore and the termination of the original maintenance contract in 2017. To maintain patrol availability during these refits, Cape-class vessels were chartered. One vessel, HMAS Bundaberg, was decommissioned in 2014 following a shipyard fire. The class began phased retirement in 2021, with the final vessels decommissioned in December 2025. The Arafura and Cape classes were selected as successors.