Flight rules challenged after ‘mastbumping’ factor in fatal crash

WELLINGTON: The Civil Aviation Authority says there may be changes to rules around the flying of Robinson helicopters, after a report into a fatal 2014 crash found mastbumping was to blame.

The accident killed pilot Damian Webster (37) when his Robinson R44 ploughed into steep bushland northeast of Mt Arthur in the Kahurangi National Park.

The aircraft broke into pieces in midair when one of the rotor blades struck the cabin due to a phenomenon known as ‘‘mast bumping’’, the Transport Acci dent Investigation Commission said in a report released yesterday.

Robinson Helicopter Company president Kurt Robinson rejected much of the report, saying Mr Webster was inexperienced.

‘‘TAIC suggests somehow that there may have been conditions or something that no pilot, no matter the experience level, could have survived — and we don’t agree with that at all,’’ he told RNZ. Mr Webster had logged 287 flying hours, but only 11 in the Robinson R44, the TAIC report said.

While not ruling out the pilot may have contributed to the accident, investigators said all Robinson helicopter models were susceptible to mast bumping in lowgravity conditions.

TAIC recommended safety limitations and requirements applying to R22s and their pilots be extended to all Robinsons and their pilots, regardless of their experience, saying Mr Webster would not have been allowed to fly at the time of the 2014 crash if the rules applied to R44s.

A statement released by the Robinson company yesterday said: ‘‘Robinson disagrees with much of the report’s technical background, several of the TAIC findings, and with the TAIC’s recommendations that special wind and turbulence limitations be placed on all Robinson helicopters.’’

The Civil Aviation Authority, which sets aviation rules, said recent rule and training changes had meant there had been no mastbumping accidents in New Zealand the past two years. But CAA general aviation deputy director Steve Moore said TAIC’s recommendations could still be taken up in some form, after the authority’s specialists met Robinson representatives and the Federal Aviation Administration in the US.

The Robinson statement said the report’s description of the rotor system and the mechanics of mast bumping ‘‘contain numerous technical errors and incorrect assumptions’’.

‘‘All teetering rotor systems are subject to mast bumping.

‘‘There is no unique design feature on the Robinson rotor head which makes the Robinson more susceptible to lowg mast bumping.

A US Federal Aviation Administration technical panel formed in 1994 investigated lowg mast bumping in Robinsons and found the trihinge design of the Robinson main rotor hub does not affect susceptibility to lowg mast bumping, the company said.

‘‘Although winds and turbulence alone do not cause lowg mast bumping, they can have an additive effect if combined with improper control inputs.

‘‘An inappropriate aggressive control response to turbulence is more likely with an inexperienced pilot.

‘‘The accident pilot’s very low experience level flying helicop ters and the fact the flight was conducted at the behest of a potential future employer may have combined to make the pilot attempt a flight beyond his experience and skill level.

‘‘Additionally, the accident helicopter was equipped with external cargo pods which are not factory tested or approved and may have affected the handling of the aircraft in strong winds.’’

There are about 300 Robinson R22, R44 and R66 helicopters flying in New Zealand, making up about 40% of the country’s fleet. — NZN