Captain Danniel Lyon, Lieutenant Maxwell Nugent, Warrant Officer Class Two Joseph Laycock and Corporal Alexander Naggs were killed when their MRH-90 chopper crashed off Queensland's Whitsunday Islands on July 28, 2023.
The senate inquiry into the crash, which began in June, heard claims from former test pilots Major Ian Wilson and Major David Lamb that an independent Defence Flight Safety Bureau report exhibited an obvious conflict of interest and contained fabricated evidence.
In its report released on Friday, the committee recommended the government review the safety bureau's report to ensure the investigation or its conclusions were not improperly influenced.
"The poor handling of the conflict of interest by the DFSB has brought into question the independence and veracity of its report and findings," the committee found.
Testifying before the inquiry in August, senior defence officials denied claims of a cover-up and noted there was a full aviation investigation safety report publicly available.
"I'm not aware of any cover-up of any sort," Air Vice-Marshal Tim Innes, representing the Defence Aviation Authority, said at the time.
Sue Lyon, the stepmother of Captain Lyon, said Defence had shown little empathy to the families of those killed in the crash, criticising the department for appearing determined to attribute responsibility for the accident to Captain Lyon through a finding of human error.
"As a grieving stepmother, I have personally witnessed and experienced behaviour from Defence personnel that I consider unacceptable, insensitive and dismissive," her written statement to the inquiry read.
Other recommendations in the report include the government scrutinising the safety bureau's independence and that the bureau establish a conflict of interest disclosure and exclusion process.
The committee also recommended the auditor-general conduct an audit into army aviation's compliance with workplace health and safety regulations, particularly its management of fatigue.
The ADF regularly looked at its schedule of activities to make sure personnel were able to take time off, Commander Army Aviation Command Major-General David Hafner told the inquiry.
Comcare officials told a previous inquiry Defence should face prosecution, identifying two alleged breaches of the law relating to fatigue management and the TopOwl helmet system worn by the pilots.
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