An Australian Defence Force inquiry into the July 2023 crash that killed four servicemen is ongoing in Brisbane before former judge Margaret McMurdo.
The crew from the 6th Aviation Regiment based in Sydney was flying in a night training run during the ADF's annual Exercise Talisman Sabre alongside US forces.
Captain Danniel Lyon, Lieutenant Maxwell Nugent, Warrant Officer Class 2 Joseph "Phillip" Laycock and Corporal Alexander Naggs died when their MRH-90 Taipan crashed into waters off Queensland's Whitsunday Islands.
Major-General Stephen Jobson, former commanding officer of Army Aviation Command, was grilled on Wednesday about why the Taipan wasn't pulled from service earlier following years of under-performance.
The inquiry has heard that Army Aviation was working on the "rapid replacement" of the Taipan with new US-made Black Hawk helicopters when the 2023 crash happened.
Major-General Jobson told the inquiry the MRH-90 was an "immature and under-performing system" and since its acquisition in 2007 it had a high level of risk management.
Under questioning by counsel assisting Jens Streit, he agreed the "demanding and underperforming" Taipan posed "an elevated risk" to personnel flying in it.
He said he was only a junior officer at the time of the 2007 acquisition and he noted everyone in aviation command had worked to "the very best of their ability" to operate the helicopter successfully.
But over time it became apparent, following groundings of the aircraft and ongoing problems, that successful operation of the MRH-60 was unlikely, Major-General Jobson said.
The inquiry heard that a review of army aviation by retired Air Chief Marshal Angus Houston in 2016 identified significant challenges and recommended the Taipan should not be deployed to the 16th aviation regiment - but it was.
When asked why the Taipan was not swapped out earlier, Major-General Jobson said their retention was a "practicable outcome" with a lot of work put in to make it successful, which in the end was not achieved.
The major-general said those killed in the 2023 Taipan crash were "the finest of Australians" and their loss was a "great tragedy".
"That night we lost four good men".
