Accident Overview
A helicopter experienced a loss of engine power during takeoff, leading to a forced landing and rollover. The helicopter sustained substantial damage upon impacting terrain and rolling onto its left side.
Pilot Report
The pilot reported that the engine was producing 3,000 rpm while hovering. During the transition to forward flight, after clearing a fence, the engine lost power. The pilot suspected a stuck exhaust valve and attempted a run-on landing to a field. The helicopter touched down on its left skid twice but was not aligned straight. On the third touchdown, with low rpm, the pilot stated he ran out of tail rotor authority, and the helicopter rolled over onto its left side.
Engine Examination
An inspection and engine run were conducted. The engine ran at 1,800 to 2,000 rpm and then at 1,110 to 1,200 rpm, during which it popped and ran unevenly. A subsequent re-inspection revealed that a 1/8-27 NPT Allen plug for the number four cylinder was missing. When the hole was plugged, the engine ran smoothly.