An investigation into a mechanical failure that caused a 2019 helicopter crash in Kakadu has found a number of oversights in Parks Australia's safety procedures worsened the accident that three crew were lucky to survive.

Two park rangers and the pilot were flown to Royal Darwin Hospital with serious back injuries and chemical burns from spilled fuel.

The Australian Transport Safety Bureau has now released its report into the incident, blaming the crash on a mechanical failure.

But its investigation also found a number of issues with safety procedures overseen by Park Australia, which jointly manages the sprawling park with traditional owners.

It found those oversights were among "a range of factors exacerbating the occupants' injuries or increasing risk".

Parks Australia required park rangers to wear helmets during culling tasks, but the ATSB found that helmets had not been provided and were not regularly used.

The ATSB also found that the relevant risk assessment was three years out of date and incomplete, and the helicopter model, operator and crew had all changed since the assessment was last updated in 2015.

It said high turnover in park management meant there was limited oversight of culling operations and some other relevant documentation had not been completed since 2015.

The park's radio network, which was cited as a key safety feature of park operations such as the cull, was also found to cover just 10 per cent of the park.

Parks Australia admits limited oversight

Parks Australia told the ATSB that it has since upgraded the radios used in the park and admitted that staff turnover had limited its oversight.

"A Parks Australia representative stated that they did not have visibility of the aerial platform shooting management process and that high turnover in the management role over the preceding years had hampered Parks Australia's ability to provide oversight in that regard," the report said.

"The culling team had no permanent manager in place."

The shooter's harness, provided by Parks Australia, was also found to be three weeks past its 10-year retirement date.

Since the accident, Parks Australia has recruited specialist staff to oversee and develop new safety procedures and suspended aerial culls until adequate safety procedures are in place.

A spokeswoman from Parks Australia said the body is dedicated to reviewing and improving its safety systems to address areas for improvement identified following that incident and has already taken a number of steps to do so.

The ATSB investigation report follows a recent internal review commissioned by Parks Australia that revealed a string of safety and communication problems.

The handling of the incident by Parks Australia and its former director, James Findlay, became a flashpoint in ongoing disputes between traditional owners and Parks Australia.

The relationship continued to deteriorate and Mr Findlay eventually resigned.