Inquest told army helicopter started blaze

The crew on an army helicopter that started Canberra's devastating 2020 bushfires were landing for a toilet break when they inadvertently ignited the monster blaze.

One of the pilots says he didn't think to have one of his passengers contact emergency services about the fire even after noting its size, insisting he was "concerned we were going to fall out of the sky" due to aircraft damage.

An inquest began at the ACT Coroners Court on Monday, focusing on the 45 minutes it took for the MRH-90 Taipan helicopter's crew to alert the ACT Emergency Service Agency to the fire's location.

The helicopter - codenamed ANGEL21 - was scouting remote helipads that could be used by outside firefighting teams on January 27, when its searchlight ignited the blaze in the Orroral Valley.

The court was played a tape recording of communications on board the helicopter, which included the army major in charge - who cannot be named for legal reasons - asking if the crew could land to use the bathroom.

"Are we authorised to land in some of these areas for the guys to get out and have a piss?" he said.

They then landed at 1.38pm on a remote helipad that did not form part of their reconnaissance plans for the day.

He admitted he hadn't turned off the searchlight before landing, which the court heard can be as hot as 550C.

The on-board recording heard one passenger - another army member - yell "come up, come up, we've started a fire, turn the searchlight off".

The helicopter only stopped for around one minute.

They returned to Canberra Airport and made a distress call indicating urgency but no immediate threat to life.

Counsel assisting Kylie Nomchong told the court there'd been regular communications between ANGEL21 and air traffic control on the 17-minute flight to the airport, but no mention of the fire.

Admitting he'd quickly known the blaze could be substantial, the major made no steps towards either locating the fire with emergency services or having one of his passengers do it.

"We didn't know if we were going to fall out of the sky at any second ... we were focused on trying to stay alive," he said.

The other pilot on the helicopter agreed, admitting they could have delegated the task to one of the passengers but "in the context it wasn't a priority".

One pilot told a passenger "we'll report that up" regarding the fire, but wanted him to focus on observing damage to the helicopter.

"In the valley there was no immediate threat to life ... on the aircraft there was," he said.

Asked if he'd do things differently if a similar incident occurred, the major said he was "very satisfied with the actions of my crew that day".

The fire, which burned for five weeks, was declared out of control after 6pm when more than 1000 hectares were alight and would eventually grow to burn 87,923 ha throughout the ACT.

ACT Chief Coroner Lorraine Walker opened proceedings stating the inquest wasn't about "crucifying any individual or decision made in the heat of the moment".

"We're here to explore how we can learn from it with a view to enhancing everyone's safety in the future," she said.

The inquiry is set to run until Friday.