A group of experienced bushfire experts wants answers about how a backburn at Mount Wilson last December got out of control and eventually burnt homes in the Upper Mountains.
The NSW RFS has investigated the December 14 burn and found that, while the weather forecast was initially favourable, the humidity dropped and the wind changed, blowing embers back behind the firefighters.
Inspector Ben Shepherd said: "Introducing a backburn is never a zero risk but it is done in agreement with planning and operations officers. Of course, there was local knowledge as well," he said, including from the captain of the local RFS.
"It was unfortunate that it did escalate but ... it was the right strategy and the right time to implement that burn."
But the Independent Bushfire Group, a newly formed organisation of former bushfire managers with more than 400 years of experience between them, believes there are questions still to be answered.
Ian Brown, who worked in national park management for over 20 years and has managed bushfire programs across the Blue Mountains parks system, said: "The weather was already threatening at 10 o'clock when the burn was lit, so we need to see the investigation report with full details of how that decision was made, and the special fire weather forecast for that location on that morning.
"Eight months after it happened, the impacted communities and firefighters deserve nothing less than a full explanation."
The NSW bushfire inquiry report released a fortnight ago found that conditions on the day "rapidly deteriorated" when the wind changed.
A week later, it threatened (and destroyed) properties in Bilpin, Kurrajong Heights, Bell, Mt Victoria and Blackheath.
Mr Brown said the Bushfire Group recognised that in firefighting "things can always go wrong. The important thing is to learn from them and go foward with better processes."
Inspector Shepherd said there were "thousands of backburns done last season and only a handful ended up escaping".