Joy riding operations had been delayed by strong north west winds but after the wind had moderated some six flights were completed uneventfully. The operators normal pad was being resurfaced so the pilot was using a small paddock about 70 m square. The paddock was bounded to the west by 80 foot trees, with power wires to the east and south, and buildings and horses to the north. On the last departure the pilot was accelerating through 20 kts above the trees when a strong northerly gust was encountered which rolled the helicopter to the left and caused it to descend rapidly downwind. The pilot was unable to prevent a subsequent collision with a high fence and a heavy landing. The two passengers received minor injuries.
