Senior military and defence department figures have confirmed a major design flaw with a Howard-era fleet of helicopters totalling nearly $3.8 billion has limited its operational capability even after attempted fixes.
Chief of Army Lieutenant General Richard Burr appeared before a Senate estimates committee on Tuesday morning and admitted the 47-strong fleet of MRH-90 Taipan helicopters suffered from a door flaw that limited its suitability for certain operations.
Upon questioning by Labor Senator Tim Ayres, General Burr confirmed the helicopter's design flaw meant that simultaneous suppression fire from a side mount gun while troops were rappelling was not possible.
General Burr said there had been "tactical workarounds" for mitigating the limitation but the Airbus-manufactured fleet would need to undergo a third round of adjustments to rectify the problem.
The workaround requires a second supporting helicopter to perform suppressive fire while the first helicopter allows its troops to rappel.
The committee heard Defence had initially replaced the original gun mount with a second one but it could not fit the preferred weapon, a minigun, or allow firing while troops rappelling. A third adjustment has been procured by Airbus Australia at the tune of $21.9 million.
First assistant secretary Shane Fairweather later confirmed it was the size of the door that was root of the problem.
"It's an issue of the width of the door," Mr Fairweather said.
"The door isn't wide enough to be able to exit safely while firing is taking place."
The third gun mount would minimise the time at which the firing couldn't take place but still wouldn't allow for simultaneous firing and rappelling. Mr Fairweather added it was "physically a limit of the door width" with the MRH-90 fleet.
The committee separately heard a tail rotor fault, which required the MRH-90 fleet to remain grounded for some of last year while it was modified, was the reason the fleet had only completed half of its expected flying hours.
Mr Fairweather explained it was an issue that affected a number of other nations as well.
The fleet, which cost $3.77 billion before sustainment costs are added, is scheduled to achieve its final operational capability by December 2021 with Navy using six MRH-90 helicopters but suffering a separate issue with its cargo hooks it is "very close" to resolving.
Defence minister Linda Reynolds said she and the Minister for Defence Industry Melissa Price had undertaken talks with Airbus in order to find a solution to the chopper's issues.
"I'm very, very aware of the issues that have plagued that part of this capability, which is why Melissa Price and I have met more than once with Airbus and with their CEO in relation to remediation of this project," Minister Reynolds said.
"We continue to monitor the project, very carefully with Airbus and with Defence."
Chief of Defence General Angus Campbell rushed to the defence of the MRH-90 fleet, describing it as "extraordinarily advanced".
"The MRH 90 is an extraordinarily advanced helicopter and it does do things that no other helicopter on the planet can do," General Campbell said.
"There is no perfect helicopter, there's no perfect machine or person and it is a matter of understanding how to fly that helicopter.
"You're quite right, there is an issue with the door guns. We know it. We're working on it."