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More than 50 helicopter pilots, including members of the New Zealand Defence Force, are being trained this week how to avoid a dangerous phenomenon which may have caused a fatal helicopter crash in 2014.
The Helicopter Line organised the vortex ring state (VRS) training after one of its Squirrel helicopters crashed on Mt Alta while coming in to land, killing Auckland businessman Jerome Box (52).
The helicopter split in two and somersaulted 700m down the mountain while a snow landing was attempted.
Mr Box was one of seven passengers in the helicopter, five of whom were thrown from the cabin.
THL was fined $47,600 after being convicted in the Queenstown District Court of two charges brought by the Civil Aviation Authority under the Health and Safety in Employment Act. However, Chief Judge Jan-Marie Douge said the parties agreed THL's failings did not cause the crash.
THL chief executive Mark Quickfall said vortex ring state was identified as a ''potential causative factor'' through an internal investigation. Director Grant Bissett had since been in ''constant contact'' with Swiss pilot and former flight instructor Claude Vuichard.
The founder of the Vuichard Recovery Aviation Safety Foundation created an alternative VRS recovery technique which enabled pilots to exit the state more quickly and safely.
Mr Quickfall said VRS often occurred on fine days when there was ''fickle wind'' not picked up by the pilot.
''Instead of the wind pushing over the nose of the helicopter and getting lift under the blades, you're basically making a column of messy air and you lose the lift,'' he said.
Any increase in power makes the helicopter descend faster.
Mr Bissett said the traditional recovery technique involved ''significant height loss'' of about 200 feet and meant the helicopter exited at a high rate of descent.
Using the Vuichard technique, a helicopter exited with height loss between 20 and 50 feet and climbed under control, ''which is critical if you are close to terrain''.
Mr Quickfall said the aircraft could ''recover a lot quicker and then hopefully fly away''.
The training, which began yesterday, aimed to prevent future similar accidents and was opened up to the wider industry.
''The onus is on all of us to investigate improvements to helicopter flying,'' Mr Quickfall said.
''We have invited other parties to join the training. It's a safety issue and we are more than happy to include anyone who flies helicopters.''