HMAS Maitland (ACPB 88)

PBAT Sentinel, formerly HMAS Maitland (ACPB 88), named for the city of Maitland, New South Wales, is an Armidale-class patrol boat of the Royal Australian Navy (RAN).

Design and construction
The Armidale-class patrol boats are 56.8 m long, with a beam of 9.7 m, a draught of 2.7 m, and a standard displacement of 270 tons. The semi-displacement vee hull is fabricated from aluminium alloy, and each vessel is built to a combination of Det Norske Veritas standards for high-speed light craft and RAN requirements. The Armidales can travel at a maximum speed of 25 kn, and are driven by two propeller shafts, each connected to an MTU 16V M70 diesel. The ships have a range of 3000 nmi at 12 kn, allowing them to patrol the waters around the distant territories of Australia, and are designed for standard patrols of 21 days, with a maximum endurance of 42 days.

The main armament of the Armidale class is a Rafael Typhoon stabilised 25 mm gun mount fitted with an M242 Bushmaster autocannon. Two 12.7 mm machine guns are also carried. Boarding operations are performed by two 7.2 m, waterjet propelled rigid-hulled inflatable boats (RHIBs). Each RHIB is stored in a dedicated cradle and davit, and is capable of operating independently from the patrol boat as it carries its own communications, navigation, and safety equipment.

Each patrol boat has a standard ship's company of 21 personnel, with a maximum of 29. The Armidales do not have a permanently assigned ship's company; instead, they are assigned to divisions at a ratio of two vessels to three companies, which rotate through the vessels and allow the Armidales to spend more time at sea, without compromising sailors' rest time or training requirements. A 20-berth auxiliary accommodation compartment was included in the design for the transportation of soldiers, illegal fishermen, or unauthorised arrivals; in the latter two cases, the compartment could be secured from the outside. However, a malfunction in the sewerage treatment facilities aboard Maitland during pre-commissioning trials in August 2006 pumped hydrogen sulphide and carbon monoxide into the compartment, non-fatally poisoning four sailors working inside, after which use of the compartment for accommodation was banned across the class.

Maitland was constructed by Austal at their shipyard in Henderson, Western Australia. She was commissioned into the RAN in Newcastle, New South Wales on 29 September 2006. A day later, the ship was granted the right of Freedom of Entry to her namesake city, Maitland.

Operational history
Maitland was assigned to Assail Division, and was based in Darwin. She was decommissioned on 29 April 2022.

After being decommissioned the ship was selected for conversion to an uncrewed autonomous vessel as part of a trial of artificial intelligence. Austal will refit the ship over 18 months. Once this work is completed, the ship will be used for a range of tests and trials.

On 24 April 2024, it was announced that PBAT Sentinel had successfully completed sea trials.