What happened
On 21 July 2018, a Robinson Helicopter Company R44 helicopter, registered ZK-HTB, was
en route from Wanaka to Upper Estuary Burn Valley when it suddenly departed
controlled fight and crashed into Lake Wanaka, killing the pilot who was the sole
occupant.
Why it happened
The Transport Accident Investigation Commission (Commission) found that the
helicopter was likely to have encountered unexpected turbulence of a magnitude
sufficient to result ultimately in the in-flight break-up of the helicopter.
The Commission also found that the helicopter’s speed at the last position report likely
increased the risk of an adverse outcome in the mountainous operating environment.
The Commission further found that investigations into loss-of-control or mast bumping
accidents involving Robinson Helicopter Company helicopters continue to be hampered
by a lack of data. Allied with this is a lack of understanding of how the main rotor
performs in adverse conditions. This lack of factual information has limited the
effectiveness of safety investigations.
What we can learn
The R44 Pilot Operating Handbook used the non-standard term ‘significant’ to describe
turbulence. The Commission found that the R44 Pilot Operating Handbook did not
explain the meaning of this term. In June 2020, Robinson Helicopter Company amended
Safety Notice 32: High Winds or Turbulence, contained within the R44 Pilot Operating
Handbook, to define the term ‘significant’. The added definition aligned with
commentary in a Robinson Helicopter Company safety video regarding Safety Notice 32.
The key lesson from this inquiry is that pilots need to exercise caution when planning
and conducting flights into areas of potential turbulence. Pilots should seek to avoid
these situations. Should turbulence of any strength be encountered, pilots need to take
immediate action to minimise its effects. Also, pilots of Robinson Helicopter Company
helicopters need to be familiar with Safety Notice 32 and the associated video and avoid
flying in high winds and turbulent conditions.
Who may benefit
Pilots, operators and all potential users of Robinson Helicopter Company helicopter
types may benefit from the findings and lessons learned.
