A Rural Fire Service (RFS) commander has told an inquest he did not ignore concerns raised by a pilot about a back-burn during the Black Summer bushfires, which jumped containment lines and destroyed 100 homes west of Sydney.

New South Wales Coroner Teresa O'Sullivan has started examining the planning and execution of back-burning operations during the 2019-20 emergency as part of wider inquest into the deadly fires.

James Carter, a qualified fire behaviour analyst with the RFS, had been deployed to the Gospers Mountain Incident Management Team (IMT) as a divisional commander.

On Tuesday he was questioned about the decision to start a back-burn around the Grose Valley Mount Wilson area on December 14, 2019, which was conducted with the aim of helping to contain the southern edge of the fire in the Blue Mountains.

Mr Carter told the court fire crews had a small window of opportunity to conduct the burn because volatile weather conditions had been forecast for the following days and residents wanted the RFS to act.

"There was a lot of anxiety in the community to commence the burning as early as possible," he said.

Mr Carter said the location was chosen after two and six millimetres of rain fell across the fire ground in the days prior.

"If the fuel is not in a state to be fully consumed, what you do is you end up with what we would call a patchy burn," he said.

"Given the potential for extreme fire danger that year, once the fuels had dried out, we were very clear that we needed to put a high-quality burn in to remove as much fuel as possible to make sure the fire couldn't run through remaining unburnt fuels."

Mr Carter said that short of a large air tanker, he felt "very comfortable" about the amount of resources available at the time to conduct the burn, despite more than 100 fires burning across other parts of the state.

But Mr Carter said the weather changed within hours of the back-burn starting and the fire broke containment lines.

It eventually burned through more than 1 million hectares and destroyed 100 homes at Lithgow, Clarence, bell, Dargan, Bilpin, Currajong and Blackheath.

Pilot 'raised concerns'

In a written statement tendered to the court, National Parks and Wildlife Service pilot Chris Banffy claimed he "raised concerns" with the IMT about the speed at which the back-burn was moving and alerted the team to spotting outside of containment lines.

In the statement, Mr Banffy said he communicated through radio messages and had landed his plane to speak with the team in person about what he had seen from the air.

Mr Carter told the court no entry was made in his log about the interaction because it had not seemed significant enough at the time.

"My log was being kept by the comms van … I wasn't physically writing my log myself," he said.

Under cross-examination by Mr Banffy's legal representative, Jennifer Single SC, Mr Carter denied that he had ignored the pilot's concerns.

"I don't see it as a concern being raised," he said.

Mr Carter also disputed claims that local knowledge from some brigade captains was not considered when the decision to conduct the back-burn was made.

"We were aware that we needed everybody to be on the same page in order to make the strategy work," Mr Carter said.

"I would say that [the strategic backburn] was a strongly vocalised preferred option by every stakeholder."

A million hectares razed

The Gospers Mountain fire ended up burning through one million hectares of bushland over 79 days and became the largest bushfire in Australia's recorded history.

It was first ignited by a lightning strike in remote bushland in October 2019.

Mr Carter told the court he believed that the "best decisions" had been made in relation to the back-burn, given the circumstances.

"I've had many sleepless nights over this and there's very little I can point to and say I wish we'd done, or I think we could have done things better," he said.

"I stand by making those decisions and taking that action as opposed to not doing anything … which I believe, ultimately, would have exposed far more areas to fire impact."