Accident Overview
On May 20, 2020, at approximately 0933 eastern daylight time, an experimental exhibition category Bell OH-58A helicopter, registration N153SA, was substantially damaged during a landing near West Bank, Michigan. The commercial pilot and passenger were not injured. The flight was conducted under Title 14 Code of Federal Regulations Part 91 as a personal flight.
Flight History
The pilot reported departing Peach Lake Heliport (89MI), his private heliport, for a local flight to Midland, Michigan, to observe recent flood damage. On the return leg, while at an altitude of about 500 feet above ground level, the pilot felt an airframe vibration. He immediately initiated a precautionary autorotation. The pilot noted that no caution or warning lights or horns had activated in association with the vibration.
During the autorotation, the pilot made a 200° left turn toward an open field. After clearing some trees on approach, the low rotor rpm horn activated. The pilot reduced collective and executed a hard run-on landing. The helicopter slid approximately 20 to 30 feet on its skids before coming to rest upright.
Damage
The main rotor blades drooped, and one blade struck the tail boom, severing the tail rotor drive shaft. The underside of the tail boom also sustained impact damage. The helicopter was substantially damaged.
Postaccident Examination
The pilot was unable to describe the location or frequency of the vibration to FAA inspectors. The passenger reported feeling no vibration. Postaccident and follow-up inspections conducted by the pilot's mechanic found no evidence of the source of the vibration.
Conclusion
The accident resulted in substantial damage to the helicopter but no injuries to the occupants. The cause of the initial vibration was not determined.