The military helicopter which likely caused the massive Orroral fire burning south of Canberra had issues with its landing light fixed more than three years ago.
However Defence says the problem or its rectification did not cause the fire.
Chief of joint operations, Lieutenant General Greg Bilton admitted on Tuesday the fire burning in the Namadgi National Park was likely caused by the heat generated from the landing light of the MRH90 helicopter.
The landing light was being used because of the smoky conditions. Defence will stop using the lights in extreme weather conditions due to the fire.
National emergency coordinator of the Australian Defence Force's response to the bushfires Major General Jake Ellwood said it was "absolutely regretful" the helicopter caused the fire.
He said the crew were lucky to escape with their lives.
"The helicopter came down to land and within 12 seconds the aircraft was almost engulfed in flames," Major General Ellwood said.
"If not for the actions of that crew it would have been a very different outcome so the crew have done a wonderful job in saving everyone aboard that aircraft."
A report from the Australian National Audit Office has previous noted issues with the landing lights on the MRH-90 helicopter.
The 2016-17 Major Projects Report Project Data Summary Sheet said the search and landing light was deemed not fit for purpose due to beam width and lack of covertness.
"This reduced the range of illuminations under which the aircraft under which the aircraft could conduct night flying and limited operational use," the report said.
The problem was fixed by November 2016, with a different kind of bulb.
A Defence spokeswoman said that replacement bulb did not contribute to the Orroral Valley fire.
"Defence can confirm that the issue outlined in the 2016 ANAO Major Project Report with respect to the MRH-90 Taipan landing lights, did not contribute to the incident in the Orroral Valley," she said.
"The issue flagged in the 2016 MPR referred to the MRH90's operational capability to achieve the necessary visual acuity when operating at night with the MRH90 Search and Landing Light. This issue restricted the conduct of night flying, limiting operational use."
The Australian National Audit office has chronicled a litany of problems with the MRH90 helicopters over many years.
The $3.77 billion helicopter program has been listed as a project of concern since 2011, which means it has a higher level of oversight.
The Chief of the Army delayed the introduction of MRH90 into the 6th Aviation Regiment by three years, because of reliability and design shortfalls, while aircraft had to be retrofitted to bring them up to contracted standard.
The program stopped accepting aircraft twice between 2011 and 2012 over technical and reliability issues.