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New Zealand accident investigators find R66 experienced mast bumping in turbulence

Transport Accident Investigation Commission Press Release | May 5, 2016

Estimated reading time 4 minutes, 25 seconds.

The R66 was certificated by the FAA without any special training requirements like those that are mandated for pilots of the R22 and the R44 to reduce the risk of mast bump accidents. Robinson Helicopter Photo
On March 9, 2013, a Robinson Helicopter Company (Robinson) R66 helicopter crashed in the North Island’s Kaweka Range after experiencing an occurrence known as a ‘mast bump’. A main rotor blade then struck the fuselage, causing the helicopter to break up in flight. The pilot, who was the only person on board, was killed.
The weather was suitable for the flight, which was conducted under visual flight rules in uncontrolled airspace. However, the wind strength had increased during the day, leading to patches of moderate turbulence in the mountainous terrain. It was very likely that turbulence was a factor in the accident. 
The helicopter’s light gross weight and relatively high speed at the time would have exacerbated the effects of any turbulence.
The New Zealand Transport Accident Investigation Commission found that this accident, when considered alongside four other R66 accidents that have occurred globally in the five years since the helicopter type was introduced into service in 2010, suggested that the R66 was as vulnerable as the smaller Robinson R22 and R44 types to a catastrophic mast bump under certain conditions. The R66 has the same main rotor system design as the R22 and the R44.
The R66 was certificated by the Federal Aviation Administration (FAA) of the United States without any special training requirements like those that are mandated for pilots of the R22 and the R44 to reduce the risk of mast bump accidents. That was in spite of having the same main rotor design and a similar response to low G conditions as the R22 and R44. 
The Civil Aviation Authority of New Zealand accepted the Federal Aviation Administration type certificate for the R66 in April 2011, and also did not require special training for R66 pilots.
A safety issue arose as a result of there being no special training. A helicopter pilot (or trainee) with no prior experience of flying one of the smaller Robinson types could fly the R66 without necessarily having the knowledge and training that the FAA acknowledged was essential for pilots of all Robinson types. 
There was also a risk that a pilot who did have prior R22 or R44 experience would infer, from the lack of any special training requirement, that the R66 did not require the same careful handling as the smaller types.
Recommendations were made to the administrator of the FAA and the director of Civil Aviation to require additional training as a prerequisite for an R66 type rating.
It is likely that mast bump accidents with Robinson helicopters will continue to happen unless the dynamic behavior of the main rotor preceding such a catastrophe is fully understood. A recommendation was made to the administrator of the FAA to reinstate uncompleted research into the dynamic behavior of lightweight helicopter main rotor systems.
A further recommendation was made to the director of Civil Aviation to publicize the recent amendments to the Robinson R66 and R44 Pilot’s Operating Handbooks that caution against flight in high winds and turbulence.
The complete report can be found on the Transport Accident Investigation Commission website.

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