WPR22LA034

On November 15, 2021, about 0819 mountain daylight time, a Bell OH-58A helicopter, N103WC, was substantially damaged when it was involved in an accident near Molalla, Oregon. The pilot was not injured. The helicopter was operated as a Title 14 Code of Federal Regulations Part 133 rotorcraft external load flight. The pilot reported that he was on an external sling load flight, relocating Christmas trees. About 30 minutes into the flight, while enroute to refuel, the master caution light and the fuel boost light illuminated. He landed the helicopter without incident. While on the ground, prior to hot refueling, he reduced the engine power setting to idle and attempted to reset the master caution light and cycled the fuel boost switch and circuit breakers, but the lights remained illuminated. After the helicopter was refueled, the pilot increased the engine power setting to 100% and recycled the fuel boost switch and circuit breakers again and the lights extinguished. The pilot added that the operator reminded him that the fuel boost light would intermittently illuminate and extinguish. The pilot then hovered the helicopter and verified that the master caution and fuel boost lights did not illuminate. Shortly after, he maneuvered the helicopter to the loading site and trees were hooked to the external sling. The pilot lifted off and as the helicopter climbed through 60 ft above the ground, he heard a change in sound from the engine and felt the helicopter yaw. Immediately after he verified that the people on the ground were clear, he released the external load. The helicopter lost altitude and the pilot heard the main rotor speed decay, so he initiated an autorotation. As the helicopter approached the ground, the pilot raised the collective while maintaining heading. The skids contacted the water-soaked soil, and the helicopter rocked nose-low, bounced, and came to rest upright. Subsequently, the main rotor blade struck the tailboom and separated the tail rotor and tail rotor gear box assembly. Postaccident examination of the engine revealed no evidence of preimpact fire or postimpact damage. Fuel continuity was established from the fuel tank to the fuel nozzle; no fuel leaks were noted. A subsequent ground idle engine run was performed. The engine was started using battery power and a normal start sequence, which included use of the airframe mounted boost pump. The engine started normally and ran at ground idle without hesitation for approximately 5 minutes. The FUEL BOOST light on the annunciator panel remained extinguished during the entire time. After 5 minutes, the fuel boost pump was turned off, the FUEL BOOST light illuminated, and the engine continued to run at ground idle with no observed anomalies for approximately 4 additional minutes. The operator reported that the fuel boost caution light illuminated randomly, independent of whether the boost pump was operating, even after the helicopter’s most recent inspection. According to thehelicopter manufacturer’s hover performance charts, at 100% N2, at a skid height of 50 ft, at a gross weight of about 2350 pounds, and at a pressure altitude of 250 ft and 15°C, the helicopter would need about 58% torque to hover. The estimated gross weight of the helicopter was 2,350 pounds. No preimpact mechanical anomalies were observed when the engine was run in a test cell using the manufacturer’s acceptance test procedure. The Fuel Control Unit was bench tested in accordance with manufacturer overhaul manual procedures and it tested successfully by meeting serviceable limits. A compressor case half was removed to facilitate visual assessment of the compressor flow path. No pre-existing conditions were found that would have precluded normal operation. A breakaway valve CT scan showed that the breakaway mechanism was intact, and the valve was open. The breakaway valve did not show any anomalies during a fuel flow test.