Accident Summary
On June 21, 2022, about 06015 Pacific daylight time, a Bell 206B helicopter, registration N90326, sustained substantial damage when it crashed near Stockton, California. The pilot was not injured. The helicopter was being operated as a ferry flight under Title 14 Code of Federal Regulations Part 91.
Pilot's Account
The pilot reported that he was en route to a field and was not carrying any chemicals. Approximately 12 minutes into the flight, he felt a vibration that lasted no more than 10 seconds. He then heard a bang followed by a sharp right yaw. The pilot lowered the collective and rolled the throttle down to regain controlled forward flight. He maneuvered the helicopter for about half a mile to a young orchard, intending to perform a run-on landing between the small trees. When the helicopter had slowed to about 25 mph and was about 20 feet above ground level, it began an uncommanded rotation to the right. The pilot rolled off the throttle and attempted to cushion the landing. The helicopter landed level but continued to rotate, rolling onto its left side. The pilot shut down the engine and turned off the fuel switch before exiting through the co-pilot's windshield. He stated that he did not know if he had hit a bird.
Postaccident Examination
An examination conducted by the Federal Aviation Administration (FAA) revealed structural damage to the fuselage, transmission mount, main rotor, and tail rotor assemblies. The tail rotor gearbox had separated from the tailboom at the four mounting bolts, with the gearbox mounting shims found scattered on the ground about 10 feet behind the tail rotor mount. The tail rotor control bellcrank rod end was sheared off near the gearbox. One tail rotor blade remained attached to the hub but was damaged; the other blade fractured and separated, with about 80% of the blade missing. The missing sections were found about 2,000 feet north of the main wreckage. The tail rotor assembly, gearbox, and mounting hardware were sent to the NTSB materials laboratory for further examination. Metallurgical analysis showed that the pitch change control rod and the four gearbox mounting bolts had overstress fractures. The blade grips, hub, and pitch change links exhibited no witness marks or indications of preexisting damage.
Tail Rotor Blade Examination
The tail rotor blades, manufactured by Van Horn Aviation, LLC, were FAA PMA components with serial numbers C548 and C549. Blade C548 had partially separated along the centerline, with loss of outboard skin. The fracture exhibited a zig-zag pattern oriented 45° in some locations and parallel with the blade direction in others, consistent with fracture along the fiber direction of the composite across different plies. The fiber composite also showed irregular fracture patterns consistent with overstress translaminar fracture. Blade C549 had wholly fractured into three major remnants. It fractured along the root, with the outboard portion cracking along the interior foam core. Only the base remained installed on the tail rotor hub. Like blade C548, fracture directions were consistent with fiber direction. The tip was missing, with the outboard 2.5 inches of material absent. The abrasion strip on the fractured tip exhibited denting, folding, debonding/delamination along the aft edge, and discoloration from foreign material, consistent with a high energy impact on the leading edge. Manufacturer inspection identified multiple scrapes and material transfer on blade C548 and discoloration from foreign materials on blade C549. A small amount of nitrile rubber was found lodged in the fractured blade end.