The Navy’s two amphibious assault ships HMAS Canberra and HMAS Adelaide remain tied alongside at Fleet Base East, Sydney while Defence investigates issues with the LHDs’ azimuth propulsion systems.

The issue first came to public attention almost a month ago on March 29 when ABC defence reporter Andrew Green reported that both vessels were out of service after propulsion issues were discovered with HMAS Canberra while it was undertaking first of class flight trials with Army and Navy helicopters off the coast of Queensland in March.

“During these activities, a propulsion issue was identified aboard HMAS Canberra and she is currently alongside in Sydney being inspected,” Chief of Navy Vice Admiral Tim Barrett wrote on the Defence website on March 28.

“As a prudent measure, the same inspections were conducted on HMAS Adelaide and identified emergent issues.

“Having identified these emergent issues the ADF has put in place a very deliberate plan to investigate the issue and resolve it.”

However, the issues with the azimuth propulsion systems remain unresolved, with an April 25 news story in the Daily Telegraph by Matthew Benns reporting that “an investigation found maintenance and oil changes were not being done properly”.

This assertion was disputed by Deputy Chief of Navy Rear Admiral Michael Noonan, who wrote a clarifying “On the Record” statement subsequently posted on the Navy Daily website.

“Defence has maintained and operated HMA Ships Canberra and Adelaide in accordance with the builder’s specifications, including the oils and lubricants used in their operation,” RADM Noonan, who is Acting Chief of Navy, wrote.

“Defence’s leadership is not “baffled” by these emergent issues, but it is still too early to determine the full extent of this emergent work. Defence has, and continues to work closely with industry and the original equipment manufacturers, Navantia, Siemens and BAE, to identify the root cause of the issues and develop the most appropriate repair strategy.”

HMAS Canberra was commissioned in November 2014 with HMAS Adelaide following in December 2015, but both ships are yet to be declared full operational.

“Defence has taken prudent measures to ensure the operational test and evaluation period of the vessels is sufficiently thorough to ensure they will serve the nation for decades to come,” wrote RADM Noonan.

He continued that “it remains too early to determine the extent of this emergent work and Defence is working to identify the causes and develop a repair strategy.”

The 27,500 tonnes displacement LHDs are powered by two 11-megawatt Siemens azimuth propulsion system thrusters with dual propellers mounted on 360-degree steerable pods driven by onboard electric motors – electricity for which is generated by the ships’ combined diesel and gas powerplant system. The LHDs’ azimuth propulsion systems and plus their twin bow thrusters – similar configurations are fitted to large cruise ships – greatly improve ship manoeuvrability compared to conventional fixed-screw arrangements.