Incident Overview
A helicopter pilot reported a brief, minor vibration in the cyclic shortly after takeoff at an altitude of approximately 400-500 feet above ground level. The vibration intensified but decreased when the pilot lowered the collective. Facing obstructions in the flight path, the pilot intentionally collided with trees.
Preflight and Previous Maintenance
No discrepancies were found during the preflight inspection. Weeks before the flight, the pilot had observed a crack in the laminate on the top of the blue main rotor blade, which extended through to the bottom of the blade. Two mechanics inspected the blade; one determined the presence of water, while the other reported that the crack was confined to the laminate. A mechanic repaired the crack by applying a two-part adhesive externally to cover it.
Maintenance Manual Information
According to the helicopter maintenance and overhaul instructions manual, there was no mention that epoxy-type material could be applied to the surfaces of damaged fiberglass cloth. This absence of guidance contrasts with the repair method used.
Post-Accident Examination
Examination of the flight controls revealed no evidence of preimpact failure or malfunction. Inspection of the blue main rotor blade showed a segment of blade missing. However, no determination could be made as to the reason for the separation.