Event Details
On 8 July 1998, a Bell 47 G-3 Soloy helicopter operating pest control flights in vineyards near Bernkastel, Mosel, experienced a sudden power loss. Approximately eight minutes into the flight, the pilot heard a decreasing turbine sound and received acoustic and optical low rpm warnings. The helicopter was flying at an altitude of 3–4 meters above the vines at a speed of about 30 knots. The pilot managed to reduce speed before the helicopter touched down in a vineyard. After landing, the pilot shut down the engine, which was still idling.
Investigation Findings
The investigation was conducted by a German federal accident investigation authority. At the accident site, contamination was found within the fuel system, but the fine filter upstream of the fuel regulator showed no issues. The helicopter was recovered, and the fuel system and engine were removed and sent to a maintenance company for technical examination. The examination revealed serious defects in the N1 regulator of the engine, which led to a significant reduction in fuel delivery and explained the pronounced power loss. Further examination at a specialized maintenance company determined that a pressure capsule inside the regulator had broken. The contamination found in the fuel system was determined to have no influence on the accident.
Conclusion
The accident was attributed to a technical defect within the N1 fuel regulator of the engine. The power loss made the accident unavoidable, as no suitable emergency landing site was within reachable distance. No safety recommendations were issued because the problem had already been identified, and the manufacturer had recommended the installation of improved pressure capsules.