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Crash body escalates chopper concerns

NZ NewswireNZ Newswire 27/10/2016

Four in 10 helicopters operating in New Zealand could be at risk of "catastrophic" in-flight break-ups because of an issue that has killed 18 people in 20 years.

The Transport Accident Investigation Commission says there is a "real risk" here will be more mast bumping accidents involving Robinson helicopters, which make up 40 per cent of the choppers registered in New Zealand.

Mast bumping involves contact between the inner part of a main rotor blade and the main rotor drive shaft, often having fatal consequences.

The commission has added the issue to its watchlist, reserved for its most pressing concerns, saying four of its previous recommendations are yet to be actioned and as a result there is concern that more of these accidents could occur.

New Zealand authorities have investigated 14 mast bumping incidents that have claimed 18 lives since 1996.

One suspected cause of mast-bumping is low-G, a condition caused by turbulence that Commissioner Stephen Davies Howard described as like leaving your stomach behind going over a hill on a bumpy road.

Ordinarily it's not cause for concern, he says.

"It is particularly important for Robinson pilots to be aware of the risks of flying a lightly loaded helicopter at high speed in turbulence. Prohibitions on low-G demonstrations must be observed and low-G recovery training must be conducted on the ground," his watchlist warns.

There are currently around 300 Robinson helicopters registered in New Zealand.

The watchlist has also been updated to include safety concerns for pedestrians and vehicles using level crossings, including a warning that systems designed to reduce the risks have not kept pace with change.

One example was the pedestrian mazes which were initially designed to force a person to face the direction a train would approach from, which no longer applies as trains now travel from both directions.

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