The puzzle of the crashes which have cost 19 lives
Noel Wilson this week became the 19th person to die in a Robinson helicopter crash in New Zealand. The unresolved mystery is whether all the pilots were at fault or whether there’s a catastrophic issue with the aircraft.
Farmers in the valley reported no discernible wind. Without wind, you don’t get turbulence and turbulence is often a factor in helicopter mast- bump crashes where a main rotor blade can slice through the cabin or tail boom.
Yet, there on a mountainside near Queenstown, strewn among the trees lay the wreckage. The helicopter had broken up in flight. Two lives were lost.
It was a Robinson.
The American company, founded by Frank Robinson, made its first helicopter in 1979 and 12,000 more have since rolled off its production lines. Robinson is acclaimed, the recipient of the Daniel Guggenheim Medal for his “conception, design and manufacture of a family of quiet, affordable, reliable and versatile helicopters”.
Yet, according to crash data, people are dying in these helicopters at an inordinate rate.
The families of those who died on the mountainside say Robinson helicopters have pushed too far towards lightness and affordability for New Zealand conditions.
It is a vexing issue. Whether the high accident rate is due to operator error, or because the unique Robinson rotor design makes them more prone to catastrophe when things go wrong, or both, is a question that carries obvious commercial implications and an emotional load for those who are grieving loved ones.
But officials expected to be dispassionate also hold concerns. In a decision heard around the world of aviation, New Zealand’s Transport Accident Investigation Commission ( TAIC) last October put Robinson helicopters on its watch list: the highest alert it can give.
The commission’s role is to inquire into a marine, rail or air incident when it believes safety lessons can be learned. But it has no power to compel entities to apply its recommendations, and there is room for doubt that our other aviation safety agency, the rule- making Civil Aviation Authority ( CAA), sees eye- to- eye with the accident investigation commission.
Citing 14 mast- bumping accidents costing 18 lives since 1991, the commission called for renewed testing of Robinson helicopters ( among other recommendations aimed at promoting safe handling of the machines).
The commission’s action was described as an “outburst” in an email exchange between a staff member of Robinson Helicopter Company and, surprisingly, a CAA official. After Newshub published the emails, the CAA said the comment was “banter”.
The Department of Conservation ( DoC) has stopped its staff flying in the helicopters ( pending receipt of a report it has commissioned), so have Tourism New Zealand and TVNZ.
Mast bumping is contact between the inner part of a main rotor blade or the rotor hub and the drive shaft or “mast”.
Helicopters are not yet required to have recording devices and there is rarely eyewitness testimony or other direct evidence about what led to a mast bump. Statements in investigation reports about probable cause are essentially the same: “The divergence of the main rotor from its normal plane of rotation for an undetermined reason.”
Many mast- bump accidents are known to have occurred in a low- G situation ( a feeling of lightness or weightlessness, like when a car speeds over a hump). That can result from turbulence or large or abrupt flight- control movements.
A Weekend Herald review of a decade of helicopter accident data released by the CAA under the Official Information Act shows Robinson helicopters are involved in a disproportionate number of crashes.
ROBINSON HELICOPTERS make up 35 per cent of the New Zealand fleet but have been involved in 49 per cent of accidents in the 10 years to last November, including 64 per cent of fatal accidents.
Notably, all seven fatal mast- bump accidents were Robinson aircraft.
California- based Robinson Helicopter Company makes lower- cost, lightweight helicopters.
The smallest, the two- seater R22, makes up 14 per cent of the fleet and was involved in 28 per cent of accidents and 36 per cent of fatal accidents.
This model is the popular choice for training ( with more than half of all training hours) and i s flown by a higher proportion of low- hour pilots. It is, depending on the point of view, nimble or sensitive.
The four- seater R44, the most popular model in New Zealand, makes up 20 per cent of the fleet, a similar proportion of accidents, and 23 per cent of fatal accidents.
There has been one fatal accident involving the biggest of the Robinson stable, the five- seater R66. There were six of these craft in the country as at the end of last year. All three models share the unique Robinson rotor head design and have all been involved in catastrophic mast- bump accidents in New Zealand and internationally.
The potential for mast bumping is inherent in all semi- rigid two- bladed main rotor systems that teeter around a central rotor mast. With 295 helicopters, Robinsons make up three- quarters of helicopters with teetering systems registered here. The others are the Bell 206 ( 79), Bell 47 ( seven), and UH- 1 Iroquois ( 10).
But only Robinsons have been involved in mast- bump accidents here in the past decade and CAA confirmed only Robinsons were involved in fatal mast- bump crashes in the past 25 years.
The Robinson rotor head differs from other teetering systems in that it has three pivot points rather than one. The rotor system i s lighter and more responsive to control movements but also to turbulence. A mast bump is usually catastrophic.
THOSE WHO died that summer’s day two years ago near Lochy River, a short hop from Queenstown, were Stephen Combe, 42, and student James Patterson- Gardner, 18.
Combe had 4500 flight hours in helicopters and was regarded by former students interviewed by investigators as “a very thorough and professional instructor and pilot”.
He flew Gazelle helicopters with the British Royal Marines in the war in Iraq and was awarded a “Best Overall Pilot Award”.
Patterson- Gardner was a trainee with a pedigree. His forbears include a World War II Spitfire pilot and a great- uncle who was a pioneer with NAC ( now Air New Zealand). His father, Murray “Mo” Gardner, was an Olympic skier and also an aviator.
His mother, Louisa “Choppy” Patterson, is renowned in the helicopter industry. She is one of five pilots in New Zealand to have gained a platinum safety award for 25 consecutive years without a serious accident. Her company, Over The Top, had a similar safety record.
Among framed certificates on the walls of its Queenstown office is a Gold Safety Award recognising 19 years of continuous service by the company without an accident. The award covered the period ending 2013. On another wall is the framed photograph reproduced above. In February 2015, 13 months after the period covered by the safety award, her senior pilot and her only child died in a Robinson R44 operated by her company. The accident report concluded that the helicopter broke apart in mid- air when a main rotor blade struck the cabin after a mast bump. It was flying across mountainous terrain at relatively high speed, estimated at 102 knots.
Patterson and staff flew into the Lochy River area about 20 minutes after the R44 broke up.
They searched without thinking about which way to hover. You hover into wind but there was no wind, she told the Weekend Herald. “Without wind, you don’t get turbulence.”
Patterson suspects something happened to the aircraft to cause it to instantaneously roll to the right and mast bump — a pitch link failure, a blade crack? An early suspicion it may have been the result of main rotor- blade fatigue was not borne out by the investigation — a metallurgist concluded that blade fracturing was a result of the accident rather than a cause.
The head of Robinson Helicopter Company, Kurt Robinson, visited Patterson last year. He believes it was the result of pilot error.
“I do believe it was a very tragic training accident and that the instructor did not get back on the controls soon enough,” Robinson told the Weekend Herald by phone from Torrance, California. “They were flying through an area [ where there was] turbulence, a student pilot on his second training flight, and something happened. It was tragic but there was nothing wrong with the aircraft.”
The finding of the investigation, however, was that it was “as likely as not that the aircraft had hit a pocket of light to moderate turbulence”. The report was equally inconclusive about who was on the controls.
An abrupt control movement ( particularly in turbulence) can result in a sudden roll to the right and a low- G situation from which recovery can be tricky and can result in mast bump.
Patterson, whose company had operated a Robinson helicopter without incident for some years before the accident, says her son was “a measured boy” unlikely to make rash control movements.
In her opinion, the aircraft is not fit for purpose and should be redesigned. How come, she asks, other types are not as problematic?
“The Robinson rotor head will mast bump sooner than other types and the reaction from mast bump will be much quicker and more severe,” Tom McCready, an engineer and veteran accident investigator, told the Weekend Herald.
In other helicopters, you may walk away with a fright and a dented mast, says the former CAA investigator. Mast- bump accidents in Robinsons in New Zealand have been catastrophic. A new TAIC investigation i s now under way after the death of sole pilot 51- year- old Noel Edward Wilson, who was killed when his R22 crashed into a remote hilly area about 9km northeast of Reefton on Monday night.
Robinson Helicopter Company does not believe there i s anything wrong with the design. Its view i s these accidents can be avoided by pilots following the flight safety guidelines for these aircraft, and that has also been the tenor of CAA’s safety training recommendations.
The helicopter company has responded to TAIC putting Robinsons on its watchlist by posting safety alerts stressing what pilots must do to avoid low- G situations that could lead to mast- bumping, such as slowing down to 70 knots when distracted and in turbulence and to respond to buffeting with gentle control inputs.
The commission, noting that the three Robinson models share the same rotor system, recommended that US safety authority, the FAA, “reinstate research into the dynamic behaviour of the Robinson rotor system under conditions of low- G”.
McCready has attended about 30 fatal accidents, done the Robinson factory course for maintenance and made a study of the company’s helicopters. “I’ve worked on teetering systems since 1978. Of the helicopters with teetering systems you will be in trouble in a Robinson way before the others and you will have a nastier reaction.”
He is concerned that the Robinson rotor head has been “normalised” and many pilots are unaware that it is “unusual”. If it was up to him, he would redesign the head, he says.
McCready points out that he has
The Robinson rotor head will mast bump sooner than other types and the reaction will be much quicker and more severe.
Tom McCready