Military figures claim a software upgrade for the European-designed Taipan helicopter was not installed on Australia's entire fleet despite warnings it could be needed to prevent possible engine failures.
Last month's emergency ditching of an MRH-90 in Jervis Bay has put renewed scrutiny on the ADF's management of its Taipans and prompted several defence insiders to come forward to the ABC with concerns.
Defence is refusing to comment on the "ongoing" investigation into the March 28 incident, but several figures familiar with the Taipan fleet say a simple IT patch could prevent the potentially devastating "hot starting" of the aircraft.
A "hot start" occurs when a pilot restarts the engine during a mission, shortly after powering down, instead of simply leaving the engine to idle before taking off again.
Former Taipan pilots and mechanics say the helicopter's turboshaft engines are not meant to be switched on and off repeatedly during an operation and are instead supposed to be powered up at the start, then shut down at the end.
In April 2010 one of Australia's then relatively new Taipan aircraft suffered "catastrophic" mechanical failure during a training flight, with the pilot forced to return to Adelaide on one engine but landing safely.
Within three months, the MRH-90's prime contractor Airbus Helicopters, along with the engine manufacturer parent company Safran, had developed a software fix that would make it impossible for a pilot to unsafely perform a "hot start".
Several ADF sources, who declined to be identified so they could speak candidly, have told the ABC that the software upgrade was only ever installed on a handful of Australia's now 47-strong Taipan fleet.
Defence has declined to confirm or refute the suggestion or indicate whether a possible "hot start" had taken place before last month's engine failure, with a spokesperson instead telling the ABC the "investigation is ongoing".
"Defence Flight Safety Bureau is leading the investigation into the MRH-90 Taipan incident, with assistance from Airbus Australia Pacific and local representatives of the engine manufacturer," the spokesperson said.
The army's Taipan helicopters returned to normal flying operations on April 6 following a short grounding, with Defence confirming unspecified "risk mitigations" were in place for the fleet.
Earlier this year, the Albanese government confirmed a decision by the previous Morrison government to retire the MRH-90 fleet a decade early, replacing them with US-made Black Hawk helicopters in a multi-billion-dollar purchase.
