Speed, turbulence in chopper crash
Wa¯naka helicopter pilot Matthew Wallis may have been flying too fast when he hit turbulence and crashed into a lake, a new report has found.
Wallis died when his Robinson R44II broke up in-flight over Lake Wa¯naka on July 21, 2018.
An interim Transport Accident Investigation Commission (TAIC) report found the wreckage showed evidence of mast bumping.
A final report from the agency has confirmed the finding. Mast bumping is when an inner part of the main rotor mechanism hits the main rotor drive shaft; it usually results in the helicopter breaking up in-flight. Turbulence is a known contributor to mast bumping.
Three months after Wallis died, his brother, pilot Nick Wallis, and Department of Conservation workers Paul Hondelink and Scott Theobald were killed in a helicopter crash near Wa¯naka Airport.
Investigators said a pair of over-trousers flew from the cabin of the helicopter and became tangled in the tail rotor, causing it to crash. Matthew and Nick Wallis were the youngest of four brothers in a well-known Wa¯naka family. Both were helicopter pilots in the family’s aviation and tourism businesses. The TAIC report said the key lesson from Matthew Wallis’ crash inquiry was that pilots needed to exercise caution when planning and conducting flights into areas of potential turbulence.
‘‘Pilots should seek to avoid these situations,’’ it said.
Wallis was on a short solo flight from Wa¯naka Airport to Mt Aspiring National Park when the crash happened. Police and navy divers found his body in the Stevenson’s Arm area of the lake two days later.
A passing cold front on the day of the crash brought wind, forecast turbulence and reduced visibility, which were not ‘‘good’’ flying conditions, the report said.
‘‘This meant that the decision on whether to fly was ambiguous and required the pilot to exercise judgement based on the available weather information, their own knowledge and weather limits, and the capability of the helicopter.’’
It was likely the helicopter hit unexpected turbulence, which led to the mast bumping. The commission also found the helicopter’s speed likely increased the risk.
In the 10 years prior to the crash, the commission had investigated five Robinson Helicopter Company (RHC) mountain crashes where mast bumping led to helicopters breaking up inflight. The Civil Aviation Authority had investigated onemore.
All the crashes happened while the helicopters were in flight and weighed less than the maximum allowable weight.
RHC advised the commission that pilot actions were most likely the primary reason for the crashes. Wallis’ brother, Jonathan, said the family was relieved the investigation was finished.