Having departed Wycombe Air Park and in level flight, the helicopter suffered a rapid and uncommanded loss of altitude. The pilot, believing that there had been a loss of engine power, carried out an autorotation. The helicopter touched down with a high rate of descent which resulted in the failure of the tail boom and landing gear.
Data recorded by on-board systems showed that the engine operated normally throughout the event. A limited examination of the helicopter was unable to identify a defect within the engine or flying controls which might have caused the uncommanded loss of altitude.