Wanaka helicopter crash that killed Matt Wallis caused by mast blow

A tragic helicopter crash over Lake Wanaka that killed pilot Matt Wallis, three months before his brother Nick Wallis was also killed in a helicopter crash, was caused by a blow to the mast.

The Transportation Accident Investigation Commissions (TAIC) today released their findings on the July 2018 accident.

It found that the mast strike caused the Robinson R44 helicopter to rupture in flight while navigating over mountainous terrain in conditions and at a speed that put the craft at risk of an “adverse outcome” due to heavy turbulence.

Mast bump is the contact between an inner part of a main rotor mechanism and the main rotor drive shaft.

It can happen in a fraction of a second, which usually causes the helicopter to break down in flight and is fatal to those on board.

“In this case, the blow from the mast caused a main rotor blade to bend so much that it struck and entered the helicopter cabin, the helicopter broke in flight, descended, hit the lake and sank,” said the commissioner in head of TAIC, Jane Meares.

It was likely strong unexpected turbulence that caused the main rotor disc to swing excessively and the mast to bump, he said.

“Helicopter operators, owners and pilots with this type of main rotor should know that the risk of mast bump increases with the likelihood of turbulence, mountainous operating environments, high power settings, increased speed and light weight.”

Wallis, 39, was the sole occupant of the ship when it crashed. His body was found in Lake Wanaka three days after the accident.

He had traveled on what was supposed to be a short 15-minute flight, but his family’s company, Alpine Helicopters, reported that he had disappeared when he did not return as expected.

Wallis’ brother and two other people were killed in another helicopter crash near the Wanaka airport in October 2018, also believed to be caused by mast blows.

The final report on that accident is still pending publication, but a previously published interim report on the accident highlighted a significant safety concern regarding the risk posed by loose items in helicopter cabins.

“There is evidence that a pair of pants that were packed in the cockpit came out of the helicopter and got tangled in the tail rotor,” Meares said at the time the interim report was released.

TAIC has previously expressed concern about the number of accidents in New Zealand in which Robinson helicopters have experienced mast strikes.

He did not make any new recommendations in today’s report, having previously made three recommendations that address security issues.

Robinson Helicopter Company has updated its R44 Pilot Operation Manual to define the non-standard term “significant turbulence” after TAIC noted the potential for misinterpretation.

Investigations into Robinson helicopter mast strike or loss of control accidents continued to be hampered by a lack of data, according to the report.

There was also a lack of understanding of how the main rotor works under adverse conditions.

The key lesson from the research was that pilots should be careful when planning and flying in areas of potential turbulence, and that they should try to avoid these situations.

“If turbulence of any intensity is encountered, pilots must take immediate action to minimize its effects,” the report said.

They should also be familiar with Safety Advisory 32 and associated video, and avoid flying in high winds and turbulence.