Incident Description
A helicopter pilot was returning from an external load long-line firefighting operation. During the flight, the pilot noticed a vertical vibration when the aircraft exceeded 90 knots. After landing at Troy, the pilot inspected the helicopter and discovered damage to the main rotor blades.
Pilot Observations
Following the discovery of main rotor blade damage, the pilot noted that pine needles had been ingested by the helicopter's induction system. The pilot reported having no memory of striking any objects during the operation.
Weather Conditions
The weather at the time was clear with 20 miles of visibility. The sky was partially obscured by smoke, consistent with the firefighting environment.
Investigation Findings
There was no report of any mechanical failure or malfunction with the helicopter. The cause of the main rotor blade damage and the source of the pine needle ingestion were not determined in the available information.