Incident Description
During the advancement of the fuel control lever, the helicopter's engine revved and increased power, causing the aircraft to bounce uncontrollably on the landing pad. The pilot was unable to regain control of the bouncing motion.
Investigation Findings
Examination of the helicopter's airframe revealed no discrepancies that would have prevented normal operation of its flight and engine controls. Additionally, a test cell run of the engine did not reveal any discrepancies with its operation at various power settings.
Manufacturer Information
According to the engine manufacturer, if the fuel control lever is moved beyond the designated "Flight" detent, an emergency valve progressively opens to supply additional fuel to the engine. This design feature can lead to unintended power increases if the lever is improperly manipulated.
Possible Contributing Factor
The investigation noted that the pilot's incorrect operation of the fuel lever could have contributed to the engine over-revving. No definitive cause was identified, and the incident remains under review regarding pilot procedures.