Accident Overview
On November 15, 2021, at approximately 0819 mountain daylight time, a Bell OH-58A helicopter (registration N103WC) was substantially damaged in an accident near Molalla, Oregon. The pilot, who was the sole occupant, was not injured. The flight was conducted under Title 14 Code of Federal Regulations Part 133 as a rotorcraft external load operation.
Sequence of Events
The pilot reported that he was relocating Christmas trees using an external sling. About 30 minutes into the flight, while en route to refuel, the master caution light and fuel boost caution light illuminated. He landed without incident. On the ground, before hot refueling, he reduced the engine power to idle and attempted to reset the caution lights by cycling the fuel boost switch and circuit breakers, but the lights remained on. After refueling, the pilot increased engine power to 100% and cycled the fuel boost switch and breakers again, and the lights extinguished. The operator had previously informed the pilot that the fuel boost light would illuminate and extinguish intermittently.
The pilot then hovered and verified that the caution lights did not illuminate. Shortly after, he maneuvered to the loading site, where trees were attached to the sling. As the helicopter climbed through about 60 feet above ground level, the pilot heard a change in engine sound and felt a yaw. After confirming that ground personnel were clear, he released the external load. The helicopter lost altitude, and the pilot heard main rotor speed decay, prompting him to initiate an autorotation. During the landing, he raised the collective while maintaining heading. The skids contacted water-soaked soil, and the helicopter rocked nose-low, bounced, and came to rest upright. Subsequently, the main rotor blade struck the tailboom, separating the tail rotor and tail rotor gearbox assembly.
Postaccident Examination
A postaccident examination of the engine revealed no evidence of preimpact fire or postimpact damage. Fuel continuity was established from the tank to the nozzle, and no fuel leaks were noted. A ground idle engine run was performed using battery power and a normal start sequence, including use of the airframe-mounted boost pump. The engine started normally and ran at ground idle without hesitation for about 5 minutes; the FUEL BOOST light remained extinguished. When the fuel boost pump was turned off, the FUEL BOOST light illuminated, but the engine continued to run at ground idle with no observed anomalies for an additional 4 minutes. The operator reported that the fuel boost caution light illuminated randomly, regardless of boost pump operation, even after the most recent inspection.
The helicopter manufacturer's hover performance charts indicated that at 100% N2, a skid height of 50 ft, a gross weight of about 2,350 lbs, a pressure altitude of 250 ft, and 15°C, the helicopter would require about 58% torque to hover. The estimated gross weight at the time of the accident was 2,350 lbs.
No preimpact mechanical anomalies were observed when the engine was tested in a test cell according to the manufacturer's acceptance test procedure. The Fuel Control Unit was bench tested in accordance with overhaul manual procedures and met serviceable limits. A compressor case half was removed for visual assessment of the compressor flow path; no pre-existing conditions were found that would have precluded normal operation. A CT scan of the breakaway valve showed the mechanism intact and the valve open; the valve showed no anomalies during a fuel flow test.