Bell 206B Jet Ranger II crash near 3 miles WNW of Wycombe Air Park, Buckinghamshire, United Kingdom

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. Bell 206B Jet Ranger II, G-OAMI 10-16