Accident Narrative
During a takeoff over descending terrain in a mountainous area, the helicopter's rotor revolutions per minute (RPM) began to decay when the aircraft had accelerated to 40 knots and was approximately 75 feet above ground level (AGL). The pilot applied additional throttle and increased collective pitch in an effort to maintain rotor speed. However, the manifold pressure then decreased and the rotor RPM continued to decay. The helicopter subsequently settled to the ground, rolled onto its left side, and came to rest inverted.
Examination
A post-accident examination of the helicopter was conducted. The inspection focused on the engine, fuel system, ignition system, and other potential sources of power loss. No mechanical reason for the loss of power was identified. The density altitude at the time of the event was about 8,100 feet.