An inquest was launched last year after 18-year-old James Patterson-Gardner of Arrowtown and highly experienced Wanaka pilot Stephen Combe (42) were killed when the Robinson R44 helicopter broke down while flying over the Lochy River valley in the Eyre Mountains, southwest of Queenstown, on February 19, 2015.
The men were employees of the Queenstown company Over the Top, which operated the helicopter. Patterson-Gardner was the son of Over the Top CEO Louisa “Choppy” Patterson.
In her findings released today, coroner Alexandra Cunninghame said the weather was good on the day of the crash, but it was likely the machine experienced an abrupt wind change or gust.
It caused a “main rotor blade divergence sequence” also known as mast thrusts, where the helicopter’s blades hit the cabin and broke in mid-air.
It happened in a matter of seconds and both pilots were killed instantly.
The coroner said that in a different type of helicopter, the accident would not have occurred under these circumstances.
She determined that mechanical error, pilot behavior and training, or intentional initiation of a low-G sequence did not contribute to the accident.
“The Robinson rotor head design makes the R44 (and the R22) particularly vulnerable to gusts, turbulence and changes in wind direction, even at relatively conservative speeds,” Cunninghame said.
“Until more research is done that can provide more certainty about the cause of the main rotor blade divergence, Robinson helicopters should not be flown more than 70 KIAS. [knots indicated airspeed] in areas where moderate to severe turbulence is likely.”
She found that the helicopter was flown by an experienced pilot well within the then current recommendations and safety advice.
However, the evidence indicated that the airspeed of 102 knots was likely too fast to be safe, as it “increased the risk of right roller and/or main rotor blade divergence during a low-G event, which can occur due to turbulence”.
The coroner ruled that it was appropriate to make recommendations so that New Zealand regulators and the owners and users of Robinson helicopters are aware of the specific considerations that arise when flying on New Zealand premises.
Recommendations have been made to reduce the chances of other deaths in circumstances similar to those in which Combe and Patterson-Gardner died.
The coroner called for mandatory data recording systems in all helicopters and asked the Civil Aviation Authority (CAA) to ban Robinson helicopters from forecasted moderate or severe turbulence and to limit the helicopters’ speed to 70 knots in mountainous areas.
-By Kurt Bayer