In April, seven helicopters took off in a group from the Canberra heliport near Mount Majura, heading for Mangalore north of Melbourne in atrocious weather.

Six of them diverted - two to Wagga Wagga and four to Wee Jasper - but the pilot of the seventh initially landed to the west of Canberra.

But he then made the fateful decision to take off and keep going - only to crash in zero visibility, killing himself and his passenger.

The newly-released final report of the Australian Transport Safety Bureau says: "At 1453 local time, the helicopter departed the interim landing site at low level, in overcast conditions with low cloud and light rain.

"At about 1525, recorded data showed that the helicopter commenced a rapid climb and shortly after, entered a steep left descending turn which continued until it impacted terrain at an elevation of 4501 feet.

"A search was initiated the next day with the accident site located later that evening. The helicopter was destroyed, and both occupants were fatally injured."

The victims of the crash were 75-year-old Sydney businessman Peter Woodland and his 64-year-old passenger, thought to be his partner.

According to the safety bureau's report, the pilot was not qualified to fly using the navigation instruments, which were essential in bad weather.

"The pilot held a private pilot licence (helicopter) and did not hold an instrument rating, and the helicopter was not approved for instrument flight," the bureau said.

"The pilot initially made the right decision and landed the helicopter," bureau chief commissioner Angus Mitchell said.

"However, you're only as safe as your last decision, and the pilot's then decision to launch again and push on - for reasons that we will never fully comprehend - put the helicopter into a dangerous environment with powerful and misleading orientation sensations and no visual cues.

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

"Tragically, this led to a loss of control of the helicopter and an unsurvivable collision with terrain."

The burea said it was also investigating other fatal helicopter crashes where the weather conditions were relevant, including one in March near Mount Disappointment in Victoria where five people were killed.

"Don't push on," the safety commissioner urged pilots who didn't have the right bad-weather qualifications.

"Pushing on into cloud and low visibility when you do not hold the appropriate rating and experience carries a significant risk of severe spatial disorientation and can affect any pilot, no matter what their level of experience."

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