Former Justice the Honourable Margaret McMurdo is conducting an independent inquiry into the crash of an MRH-90 Taipan helicopter, off the north Queensland coast in July 2023.
The fifth public hearing into the deaths of Captain Danniel Lyon, Lieutenant Maxwell Nugent, Warrant Officer Class Two Joseph Laycock and Corporal Alexander Naggs began in Brisbane on Monday.
Their aircraft, callsign Bushman 83, was one of four choppers tasked to fly to Lindeman Island to collect Australian Defence Force personnel who were conducting an exercise.
An aircrewman identified by the pseudonym D4, who was on board Bushman 81, was questioned by counsel assisting Flight-Lieutenant Alexandra Rose about a statement in which he asserted that "junior personnel in the army generally are promoted to leadership positions prematurely because experienced soldiers and officers are leaving".
Army Aviation was haemorrhaging experience and corporate knowledge at a non-recoverable rate without serious intervention, the corporal said in a statement.
"I think we are losing people at a tremendous rate," he told the inquiry.
"The experience across our aircrew workforce is continuing to slide, and something does need to be done, otherwise we're just not going to have the experience required to grow and foster future generations."
He did not believe that any members were out of their depth or not suited to those positions.
"I just think that when they're compared to the experience levels that we've had previously in defence, the depth isn't there."
The inquiry has previously heard that the helicopters took off from Proserpine airport, entering a holding pattern while waiting for confirmation the ADF personnel on the island were ready to be picked up.
The helicopter was seen gaining altitude before nosediving into the ocean, killing all four crew members.
Earlier on Monday, another aircrewman known as D8 told the inquiry he had previously held concerns about the safety of the fleet, after an incident over Jervis Bay, when an MRH-90 suffered an engine failure in March 2023, causing it to ditch into the sea.
D8 told the inquiry he had "very little confidence" in the aircraft because he was worried there were unknown issues or problems that crewmen weren't told about.
"I had concerns that there were other faults that were known that … we didn't know about," D8 said.
He said there had been two groundings because of technical failures and one because of a software problem.
"When you have those in an aircraft and someone doesn't tell you it's a problem, as an operator, had I known that those engines were not modified to be as safe as possible. I probably wouldn't have got on the aircraft (before the Jervis Bay incident)."
Australia's MRH-90 Taipan helicopter fleet was pulled from service soon after the fatal crash, more than a year before its intended withdrawal date.
The inquiry continues on Tuesday.
