Incident Summary
A helicopter pilot reported experiencing a disturbing vibration shortly after liftoff. In response, the pilot initiated an autorotation to an open agricultural field. During the descent, the pilot executed a 180-degree turn to avoid a line of trees.
Pilot Actions and Outcome
The pilot noted that the rotor speed became too low, and he was unable to reduce the sink rate. This led to a hard landing. The pilot stated that additional practice in autorotation descents and landings might have prevented the accident.
Aircraft Damage
During the accident sequence, the main rotor contacted and separated the tail boom. Additionally, the right landing skid collapsed.