Mt Pirongia, where a helicopter was heading to rescue two trampers before being forced to make a heavy landing. Photo: Susan Murray/RNZ
A report on a helicopter crash in Waikato has vital information for manufacturers, pilots, operators and flight schools around the world, the Transport Accident Investigation Commission says.
Nobody was hurt when the Hamilton-based Westpac rescue helicopter crashed on Mount Pirongia in 2023, while on a mission to rescue two trampers.
The TAIC investigation found that the helicopter almost certainly entered a hazardous aerodynamic condition called vortex ring state (VRS) - marking what may be the first time a helicopter accident has been proven to have occurred as a direct result of VRS.
TAIC chief investigator of accidents Naveen Kozhuppakalam said VRS caused a helicopter to lose lift and drop fast.
He said the report showed how VRS could take hold quickly and with little warning, especially in mountainous terrain.
"Helicopter pilots receive general training on VRS, but each helicopter type behaves differently," said Kozhuppakalam. "In this case, VRS onset occurred just 291 feet above ground level - neither the height nor enough time to successfully recover. And the helicopter's flight manual contained very limited information about the flight conditions and parameters conducive for VRS, or how to avoid and recover from it.
"All helicopter pilots need to clearly understand how VRS develops and how to avoid it," he said.
TAIC has recommended the Civil Aviation Authority promote awareness of the risk and advocate for more detailed information in helicopter fight manuals.
The Commission also wants the International Civil Aviation Organisation to consider requiring VRS alert systems in new helicopters.
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