Hughes 369D N102SU accident near Belleville, West Virginia

Probable cause

The ingestion of foreign object debris into the engine, which resulted in a sudden loss of engine power and a subsequent collision with trees and terrain during the forced landing.

NTSB analysis

The pilot was conducting low-altitude, external-load tree-trimming operations when he heard a loud “boom,” and the helicopter entered a rapid descent. He maneuvered toward smaller trees to minimize the impact and briefly lowered the collective to preserve rotor rpm before raising it just before ground contact. The helicopter contacted trees and branches during the descent, becoming inverted after impacting the ground. The tail boom separated from the fuselage, and the main rotor blades were severely damaged and scattered throughout the area, as were various rotor head components.

Postaccident examination of the drivetrain, clutch, and associated components revealed no evidence of pre-impact mechanical failure or malfunction. Examination of the engine revealed severe damage to the compressor inlet and rotor assembly, with multiple fractured blades from stages 1 through 5, consistent with pre-impact hard-body ingestion. Metallurgical analysis found no evidence of fatigue or manufacturing defects, and all other engine systems and components were free of pre-impact anomalies. Although the source of the ingested material could not be determined, the low-altitude operating environment near trees made it likely that debris from the trimming operation was ingested into the engine, resulting in a sudden loss of power.

Text from the NTSB. Open the NTSB docket for ERA24LA148 for the full record.