Speed and turbulence believed to be behind fatal helicopter crash

Thursday, 26 November 2020

Matthew Wallis was killed when his helicopter crashed over Lake Wānaka in July 2018.

Wānaka 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 Wānaka 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.

Wānaka pilot Nick Wallis died alongside two Department of Conservation workers when his helicopter crashed near Wānaka Airport in October 2018.

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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 Wānaka 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.

Jonathan Wallis has made a promise to his missing brother, helicopter pilot Matthew Wallis: 'we will bring you home soon'. (Video published July 2018)

Matthew and Nick Wallis were the youngest of four brothers in a well-known Wānaka 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 Wānaka 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 in-flight. The Civil Aviation Authority had investigated one more.

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.

“However, with no survivors or witnesses, it has been impossible to confirm or counter this assertion definitively,” the TAIC report said.

The lack of reliable evidence limited the effectiveness of safety investigations, it said.

“Several parties, including RHC, are currently developing suitable recorders for installation on the various types of RHC helicopter.”

In a statement, Wallis' brother, Jonathan, said the family was relieved the investigation had finished.

They accepted the report's findings that lack of reliable evidence about what caused mast bumping in Robinson helicopters “continues to limit the effectiveness of safety investigations”, he said.

“Our focus remains on moving forward as a family and in particular supporting Matthew’s young son Arthur.”