Pre-Flight and Takeoff
After completing a normal run-up and magneto check, the pilot hovered the helicopter in ground effect. A normal takeoff was then performed, remaining in ground effect during the initial climb.
Loss of Rotor RPM
At an altitude of approximately 200 feet above ground level (AGL), the pilot observed the rotor RPM decreasing from 2900 to about 2700. In an attempt to restore rotor speed, the pilot lowered the collective and increased throttle. However, these inputs produced no response, and the RPM continued to decline.
The pilot then raised the collective to achieve 33–34 inches of manifold pressure, but the RPM still continued to drop. By the time the helicopter reached approximately 300 feet AGL, the RPM had fallen to 2300.
Forced Landing
With the rotor RPM continuing to decay and altitude limited, the pilot executed a forced landing onto a dirt pile with a 45-degree slope. The outcome of the landing or any damage sustained is not specified in the source material.
Investigation
The accident investigation source did not assign a probable cause or identify any contributing factors to the RPM loss or the powerplant's failure to respond to pilot inputs.