The operator of a skydiving plane that crashed west of Brisbane killing five people used unsafe practices, Queensland's coroner has found.
Volunteer pilot Anthony Winter, 22, from Brisbane, Irish skydiving instructor Nigel O'Gorman, 34, British instructor Colin Hicklin, 41, Briton Susanne Williams, 49, and Barbara McLelland, 40, of the Gold Coast died when a Cessna 206 aircraft clipped a tree and plummeted into a dam near Ipswich about 30 seconds after takeoff on January 2, 2006.
Two people, Brisbane Skydiving Centre owner Brian Scoffell and Gold Coast woman Mandy Best, survived the crash.
Queensland coroner Michael Barnes on Monday found the Brisbane Skydiving Centre had observed a number of unsafe practices in relation to the plane.
The aircraft was about 113kg overweight at the time of the flight and none of the occupants was wearing harnesses or helmets, Mr Barnes found.
He also found the aircraft's engine had malfunctioned on at least two previous occasions, which were not reported to the Australian Transport Safety Bureau (ATSB) as required.
Fuel used in the aircraft was incorrectly stored, leading to the possibility its serviceability could be compromised.
Mr Barnes found the primary cause of the crash was a partial engine failure which allowed the plane to take off but at diminished capacity.
He was unable to determine how the failure occurred, but noted in his findings that the plane had been modified to allow for the installation of a more powerful turbo-charged engine.
He urged the Civil Aviation Safety Authority (CASA) to issue an advisory bulletin to Cessna 206 operators about the dangers of such modifications.
Mr Barnes also recommended CASA take over responsibility for monitoring skydiving planes from the Australian Parachuting Federation, whose oversight he criticised as insufficient.
"I have concluded CASA's continued withholding of its flight operations, maintenance and safety experts from the surveillance, audit and oversight of publicly offered activities is contrary to the interests of public safety," the coroner found.
No recommendations for criminal charges were made and Mr Barnes said pilot Anthony Winter "could not be blamed" over the crash.