Bell 206 N518Z accident near Sanders, Kentucky

Probable cause

A partial loss of engine power for undetermined reasons, and a loss of main rotor rpm during the subsequent autorotation, which resulted in a hard landing.

NTSB analysis

The pilot and observer were conducting a powerline patrol flight in the helicopter. About 40 minutes into the flight, while flying at 35 to 40 knots about 120 ft above ground level, the pilot heard the main rotor losing speed; the low rotor rpm light subsequently illuminated, and the associated aural warning sounded. The pilot entered an autorotation, during which he raised the collective to avoid impacting a set of power transmission lines. The pilot reported that the rotor speed remaining upon reaching the touchdown point was insufficient to cushion the landing, and the helicopter landed hard, resulting in substantial damage. After landing, the pilot noted that the engine was still partially producing power, and he shut it down using the throttle.

Examination of the airframe and engine revealed no mechanical malfunctions or component failures that would have precluded normal operation. Based on the available information, the reason for the loss of engine power could not be determined.

Text from the NTSB. Open the NTSB docket for WPR18LA164 for the full record.