Don't fly in bad weather: pilots warned

The nation's aviation authority has issued a warning to helicopter pilots on the dangers of flying through clouds and rain in the wake of an investigation into a fatal NSW crash.

The Australian Transport Safety Bureau (ATSB) probe, which examined the April 3 Kosciuszko National Park tragedy, apportioned blame to a decision to take off amid overcast conditions and low visibility.

Seven helicopters were taking part in a flying tour that morning.

However two diverted to the Riverina centre of Wagga Wagga, while four others landed in Wee Jasper, northwest of Canberra, when the weather worsened.

One pilot continued until the poor conditions forced a landing in the Brindabella region, west of Canberra.

Three hours later the helicopter took off again in overcast conditions with low cloud and light rain, crashing about 30 minutes later, killing the pilot and passenger.

It is highly likely cloud and poor visibility resulted in the pilot experiencing a loss of visual reference and probably becoming spatially disoriented.

The pilot held a private licence and was not supposed to fly through clouds, while the aircraft was built to be flown only through clear skies.

ATSB chief commissioner Angus Mitchell said the pilot initially made the right decision to land but taking off again "put the helicopter into a dangerous environment with powerful and misleading orientation sensations and no visual cues".

"Pushing on into cloud and low visibility carries a significant risk of severe spatial disorientation and can affect any pilot, no matter what their level of experience," he said.

"Know your limits. Don't push on."

Some 97 incidents involving pilots flying in bad weather have been reported to the ATSB in the past decade.

Of them, 11 resulted in a total of 22 deaths.

The report into the Kosciuszko crash is the second published by the ATSB this month into a fatal weather-related helicopter collision.