If Taz-Zorb had used eight star pickets to secure the jumping castle it provided for the Hillcrest Primary School's activities day in 2021 it would have survived the wind event which claimed six children's lives, a hearing has been told.
The parents of the deceased children reacted with despair as engineer Roderick McDonald told the criminal proceedings against company owner Rosemary Gamble the jumping castle's anchorage system had already failed by the time the dust devil was directly over the inflatable device.
Just four pegs, which did not meet Australian Standards, were used to anchor the device which had seven children on board when it was flung more than 10 metres into the air.
A little girl waiting for her turn in the zorb balls was killed when the blower used to keep the jumping castle inflated hit her.
Ms Gamble has pleaded not guilty to failing in her health and safety duty.
Mr McDonald told Magistrate Robert Webster he believed if eight star pickets had been used on the device's eight anchorage points, the castle would not have lifted into the air in the wind.
The court had been told previously that Ms Gamble had extra pegs, including star pickets, in her work ute that day.
"When the system was tested it was overwhelmingly - less than half - under the capacity intended," Mr McDonald said.
"Because only four pegs had been used, which did not meet specifications, the open edges of the castle allowed air to get under the mattress and there was lift."
He said in evidence that if a jumping castle was to be used outside there was an ever-present risk of wind.
"You cannot eliminate it so there is a duty to minimise it," Mr McDonald said.
"The installation of the anchoring system on the day provided a significantly different response to the wind which arrived."
The court was told that experts believed that the castle was held down by just one remaining peg when the dust devil hit bringing winds of between 60-80kmh.
Mr McDonald said eight star pickets would have provided a resistence to winds of over 100kmh.
He said the whole front face of the jumping castle was not anchored exposing it on multiple fronts.
"Decisions were made without competence," he said.
"Big, deep, long pegs would take time to get out. The wind event lasted perhaps one or two seconds."
