Incident Overview
A helicopter pilot landed on a bluff to discharge two passengers but decided to take off again before discharging them to find a better landing area. When the helicopter was approximately 10 to 20 feet from the takeoff point and about 200 feet above ground level, a decrease in RPM occurred.
Pilot Actions
Initially, the pilot thought he was experiencing settling with power. He lowered the nose and collective but was unable to regain RPM. He then felt the helicopter yaw to the left and sensed mast-bumping, realizing he must be cross-controlling with too much right pedal and left cyclic. Subsequently, he entered an autorotation.
Collision and Examination
During the autorotation, the helicopter collided with trees on the side of the bluff and rolled to the bottom of the hill. An examination of the engine revealed that the No.2 cylinder compression was low. The No.2 intake valve had become tuliped and was leaking, with evidence of pounding. Additionally, there were indications of high engine RPM and temperature. The helicopter had been flown 38 hours since the last inspection.