The Australian Transport Safety Bureau's preliminary report into the October 6 smash found the five-seater Cirrus aircraft had low or no power when it hit the ground in a paddock at Gundaroo, north of Queanbeyan.
A number of onlookers below the plane heard a "rough-running or surging" engine, and saw the plane descending rapidly at a low altitude and with its nose "rotating like a corkscrew".
Peter Nally, 65, was flying the plane with grandchildren aged 11, nine and six on board.
The report found he'd held his licence since 1985 and had racked up 800 hours of flying experience, while completing an official flight review as recently as August.
ATSB director of transport safety Kerri Hughes said the plane "abruptly departed from controlled flight" 12 minutes after it took off from Canberra.
"Impact marks and wreckage distribution at the accident site indicated that the aircraft impacted with terrain upright, with a slight nose low attitude and with little forward momentum, suggestive of a spin," she said in a statement.
"Key components of the aircraft's airframe parachute system were all located within the wreckage, however based on the available evidence the ATSB was unable to determine if an attempt had been made by the pilot to deploy the parachute system before the impact."
The preliminary report didn't attempt to analyse the crash but rather focused on the factual information the agency had found so far.
"As the investigation continues, the ATSB will continue an assessment of the recovered components, review pilot and operator documentation and pilot medical information, and analysis of the aircraft's performance based on flight track data and meteorological information," Ms Hughes said.
"However, if at any stage we identify a critical safety issue, we will immediately alert the relevant parties so that they might take safety actions."
The aircraft crashed on an open field next to a dam on a private property, and was destroyed in a post-impact fire.
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