What happened
The pilot placed the helicopter at Triad for a scheduled fifty-hour inspection. The aircraft was reportedly defueled to dry tanks prior to the work. Six days later, a fuel truck log indicated that the aircraft was refueled with twenty-three point two gallons as payment for the previous service. According to information furnished by the owner and Triad, the helicopter was operated for a total of one hour and twenty-five minutes at various power settings.
While on the base leg of the flight, the engine shut off abruptly, described by the owner-pilot as similar to turning a switch off. During the ensuing autorotation, the pilot had to bleed off rotor energy to clear trees. After clearing the trees, the pilot saw abandoned power lines and thought he had hit them with the bottom of the skid. The helicopter touched down in a plowed field and rolled over.
The pilot did not visually check the fuel after landing but saw no leaks. An FAA inspector added five gallons of fuel to the dry tanks after recovery and ran the engine for about thirty seconds. The engine shut down due to a crack in the fuel line which was crimped. The inspector indicated the crimp was impact damage.
The investigation
The investigation focused on the mechanical state of the aircraft following the accident. Key findings included:
- fuel exhaustion resulting from a compromised fuel delivery system.
- A cracked and crimped fuel line that prevented proper fuel flow.
- Evidence that the damage to the fuel line was caused by impact damage, likely occurring during the initial contact with the abandoned power lines or the subsequent ground impact.
Findings
The sequence of events indicates that the engine failure was not due to mechanical malfunction but rather a physical obstruction in the fuel system. The pilot's decision to continue flying after suspecting contact with power lines, without verifying fuel status, contributed to the severity of the outcome. The lack of visual fuel checks after landing further delayed the identification of the issue.
Safety message
Pilots should always verify fuel quantity and condition after any refueling event, especially if there is a discrepancy in logs or previous defueling. Any suspected contact with obstacles during flight requires an immediate and thorough inspection of fuel lines and tanks before continuing operations.