What happened
On May 23, 2010, a Fairchild Hiller FH 1100 helicopter was conducting its third sightseeing flight of the day from a private landing site in Moßbach, Germany. The flight, which included the pilot and three passengers, was flying at a low altitude near Mönchgrün when witnesses observed a sudden change in engine sound. The aircraft appeared to lose power, veered toward a wooded area, and was seen falling vertically from the sky. The impact was extremely violent, and the aircraft was destroyed. All four fatalities occurred at the scene.
The investigation
The BFU investigation focused on the mechanical state of the aircraft, the pilot's experience, and the fuel management practices. The investigation revealed that the helicopter, which was registered in the United States, had significant documentation discrepancies. Evidence suggested that several components lacked proper maintenance histories, and a previous inspection in 2003 had already flagged the aircraft as unairworthy due to expired components.
Investigators also examined the fuel used during the flight. The pilot had used a mobile refueling unit that was malfunctioning, leading to an improvised refueling process. Furthermore, the fuel used was diesel, which is not an approved fuel for the Allison 250-C18 engine; only turbine-grade fuels or AVGAS are permitted. Analysis of the cockpit warning lights indicated that several engine and fuel pressure lights were illuminated at the time of impact. Photos taken by passengers during the preceding flights provided a timeline of fuel depletion, showing a rapid decrease in fuel levels.
Findings
- The primary cause of the accident was an engine failure due to fuel exhaustion.
- The pilot failed to successfully initiate or complete an autorotation following the engine failure, leading to a total loss of rotor RPM and control.
- The pilot relied on an inaccurate understanding of fuel consumption, believing the engine used approximately 65 liters per hour, whereas modern data suggests a much higher rate of approximately 83 liters per hour.
- The use of non-approved diesel fuel may have negatively impacted engine performance and starting reliability.
- The pilot's flight experience on this specific model was limited to approximately 12 hours, and the flights on the day of the accident were his first without an instructor.
- Significant maintenance and registration irregularities were present, including the use of undocumented components.