Accident Overview
On March 18, 2024, at approximately 1720 eastern daylight time, a Hughes 369D helicopter (registration N102SU) was substantially damaged when it collided with terrain near Belleville, West Virginia. The commercial pilot, who was the sole occupant, sustained serious injuries. The helicopter was being operated under Title 14 Code of Federal Regulations Part 133, conducting rotorcraft external load operations.
Pilot Account
According to the pilot, he had completed several tree trimming flights earlier that day without encountering any anomalies. During the accident flight, while trimming trees above a creek, he noticed encroaching tree limbs and was assessing whether it was safe to continue trimming. He then heard a loud "boom," after which the helicopter entered a rapid descent. The pilot maneuvered toward smaller trees to minimize the impact. He briefly lowered the collective to preserve rotor rpm and raised it just before ground contact. He reported that he intentionally retained the external cutting saw, believing it might help absorb some of the impact forces.
Wreckage and Damage
The helicopter was found inverted in mountainous, hilly terrain. The aerial saw assembly remained attached, but its support pipe was fractured at the midpoint. The tail boom was separated from the fuselage. The main rotor blades were severely damaged and scattered throughout the area, along with various rotor head components. The nose section exhibited crushing damage consistent with contact with trees or branches during the descent.
Postaccident Examination
Examination of the helicopter's drivetrain revealed no evidence of pre-impact mechanical failure. The Kaflex driveshaft and associated components showed no cracks, fractures, or abnormal wear. The driveshaft was intact, with torque striping present on all fasteners except one, which had partial stripe loss. The main transmission input coupling and clutch subassembly exhibited no anomalous damage. All splined connections were well-lubricated and free of wear or missing teeth. The clutch functioned properly, and both bearings adjacent to the sprag assembly rotated freely. The grease and oil appeared dark, consistent with normal use, with no metallic particles or abnormal odors. Fluid levels were within specified limits.
A follow-up examination of the engine found no evidence of pre-impact fire, damage, or malfunction. The engine remained securely mounted, and the engine compartment was intact. Continuity was confirmed through both the N1 and N2 rotor systems, although neither could be rotated by hand due to significant carbon deposits and coking on the turbine seals. The compressor inlet and rotor assembly sustained severe damage, with blades from stages 1 through 5 fractured near the hubs, consistent with hard-body ingestion. Metallurgical analysis revealed no signs of fatigue failure. A pressure control system check showed no leaks.