Robinson helicopter dilemma
Why do Robinson helicopters keep crashing? The manufacturer blames pilots, but the design of the aircraft is increasingly being questioned. Debbie Jamieson reports.
In 2015, Louisa ‘‘Choppy’’ Patterson, owner of Queenstown helicopter company Over The Top, brought her son James home in a body bag.
A year earlier, Christine McConway remembered her Blenheim-based helicopter pilot son Damian Webster eating bacon and eggs. And then she never saw him again.
In 2018, Jonathan Wallis spotted the oil slick and debris in Lake Wa¯ naka that signalled something disastrous had come of his helicopter pilot brother Matt, who was flying home at the time.
The men are among 19 people killed in mast-bumping crashes in Robinson helicopters in New Zealand. Mast-bumping, sometimes called rotor blade divergence, occurs when an inner part of the main rotor mechanism hits the main rotor drive shaft. Pilots have less than a second to react before the blades slice through the cabin, causing the chopper to break up in flight.
It can happen in any helicopter, usually in turbulent or low-gravity conditions, but in Robinsons it is almost always fatal.
Nobody knows exactly how many deaths there have been worldwide, although it has been reported that there have been 313 Robinson R44 crashes, resulting in 176 deaths. The cause of the crash was unknown in nearly 60 per cent of the cases.
The Californian-based Robinson Helicopter Company attributes the crashes to ‘‘excessive or inappropriate pilot inputs’’. In other words, the pilot’s response in a sudden lowgravity situation has been incorrect.
However, there has long been a concern that the unique design of the Robinson helicopter rotor head may be responsible for the crashes, and that studies undertaken so far have been inadequate or incomplete.
In New Zealand there are 225 Robinson helicopters registered, making up one-quarter of the total number of helicopters.
Their popularity is due in large part to their low cost. A four-seater R44 costs about
US$500,000, less than half the price of competing models. They are cheaper to run, and are commonly used for flight training, agricultural, tourism, and commercial operations.
Choppy Patterson bought her
R44 in 2005 and used it for small group tourist flights and for training from the Over The Top Queenstown base.
On February 19, 2015, her son James Patterson Gardner, 18, headed out in the helicopter for a final training flight before heading off to university in Sydney.
He was with instructor Stephen Combe, 42, an eminently qualified and experienced instructor who had done more safety courses in Robinson helicopters than was required.
The dead men and the wreckage of their helicopter were found hours later in dense bush in the Lochy Valley.
In 2016, a Transport Accident Investigation Commission (TAIC) report into the crash found no clear reason for the mid-flight break-up of the helicopter, but identified that mast-bumping had occurred.
At that time, the men were the 17th and 18th people to die in unexplained mast-bumping crashes in Robinson helicopters in New Zealand, close on the heels of Damian Webster in the Kahurangi Forest.
TAIC responded by putting the helicopters on its watchlist, leading key organisations, such as the Department of Conservation, to stop using them.
It also made several recommendations, some of which the Civil Aviation Authority (CAA) adopted, including new safety awareness measures for Robinson helicopters.
However, many critics are concerned the measures do not go far enough, including Patterson, who pushed for an inquest into the crash that killed Combe and her son. The inquest took place in Queenstown over the past two weeks.
What the court heard
The weather on the day of the 2015 crash was good, chances of turbulence were low, and the pilot and student had more than adequate experience and skills, the court heard.
Given the lack of an obvious cause, legal counsel Garth Gallaway told coroner Alexandra Cunninghame: ‘‘Lay people like me struggle to understand how these accidents with these devastating
consequences can keep occurring.’’
Robinson Helicopter Company safety notices stated that low-gravity situations were almost always fatal, he said.
The company said that even experienced pilots should never attempt the type of low-gravity manoeuvres that led to mastbumping, even in training.
If pilots did encounter a lowgravity situation, they should apply aft cyclic, or push the control lever to the rear of the aircraft, the company said.
However, the court heard that pilots had less than a second to react in low-gravity situations, and the controls in Robinson helicopters are known to be extremely sensitive.
Over The Top deputy standards pilot James Forward told the court the prohibition on practising the life-saving manoeuvre meant pilots would not be sure what action to take in the event of an unexpected lowgravity situation.
Further complicating matters is a 2017 Robinson R22 crash on the West Coast, which was the subject of the only TAIC investigation into a Robinson helicopter that survived a mastbump.
In that case, the experienced pilot instinctively ignored Robinson advice and applied pressure to follow the right roll of the helicopter, an action that successfully saved it.
‘‘There’s a number of different suggestions, and there’s no way of trialling it to see if it works or not,’’ Forward told the court.
The 2015 crash, and what he had learned since, had put him off flying Robinson helicopters, Forward said. ‘‘Until there is some certainty as to what was causing [mast-bumping], and what could be done to stop it happening, then I don’t think I would ever hop in one again.’’
Lack of information
The court heard that attempts to understand mast-bumping crashes were frustrated by a lack of information.
In 2016 TAIC recommended that in-flight visual and data recorders similar to the ‘‘black box’’ on commercial planes be required in small aircraft.
However, five years later, the Ministry of Transport is still working on the issue.
‘‘In the meantime, accidents continue to occur and the footage and data that could assist . . . is not available,’’ Patterson told the court.
In the United States in the
1990s, the National Transport Safety Board undertook a special investigation into 34 Robinson crashes, all involving mastbumping, and new rules were implemented, including increased training and experience requirements for pilots.
New Zealand authorities picked up on this recommendation, but cancelled the rules for
R44s in 2004, reintroducing them only after the deaths of Combe and Patterson Gardner in 2015.
Also in the 1990s, a Georgia Tech School of Aerospace Engineering study, developing a simulation model to further understand the effects of the helicopter design, fell over when funds ran out.
This year the Robinson Helicopter Company declined an invitation to take part in the Queenstown inquest, but did provide a few details on a 2018 study at the University of Maryland, which was to update the Georgia Tech work.
The project had also been wound up before it finished, and the company said it was now continuing the study with a professional engineering firm.
Andrew McGregor, director of forensic engineering company Prosolve, who was tasked with investigating the Queenstown crash on behalf of the coroner, said it appeared unlikely that details of the work would be released.
There were many significant unresolved questions about the problem of mast-bumping in Robinson helicopters, and an analytical model of the rotor blade system needed to be developed by an independent body to investigate the effects of all the variables, he said.
It would be expensive, but was more feasible now than when the 1996 Georgia Tech study was attempted.
Patterson wanted such a study to happen with speed, to ensure no other mother would have to experience the loss she had.
‘‘No other aircraft type has these atrocious statistics,’’ she told the coroner.
‘‘Let’s put a stop to these unexplained in-flight break-ups by raising awareness, gathering evidence, fixing the problem, enhancing aviation safety.’’