What happened
On 10 February 2016, a Bell 206B Jet Ranger II, registration G-OAMI, was conducting a private flight departing from Wycombe Air Park. While maintaining level flight, the helicopter experienced a sudden and uncommanded reduction in altitude.
Believing the aircraft had suffered a loss of engine power, the pilot initiated an autorotation procedure. The subsequent touchdown occurred at a high rate of descent. The impact caused the landing gear to collapse and resulted in the failure of the tail boom. There were no fatalities and no injuries to the pilot or the three passengers on board.
The investigation
Investigators examined the aircraft's on-board systems and the engine performance during the incident. The data recorded by the aircraft's systems indicated that the Allison 250-C20 turboshaft engine had operated normally throughout the entire sequence of events.
A technical examination of the helicopter was conducted to identify any mechanical failures. This inspection was unable to find any defects within the engine or the flight control systems that could account for the sudden loss of altitude.