Incident
A helicopter experienced an engine flameout shortly after takeoff, necessitating a forced autorotative landing. The pilot reported that at an altitude of 4,500 feet MSL, the engine's N2 indication dropped to 92%. Approximately 15 seconds later, the engine flamed out. During the subsequent forced autorotative landing, the main rotor blades struck the tail boom, causing damage to that structure.
Investigation
The investigation into the incident revealed that before departure, the helicopter had been fueled with AVGAS instead of the required turbine fuel. The engine operating manual permits the substitution of AVGAS for turbine fuel in emergency situations, but it advises that the fuel boost pump must remain on when using this alternate fuel. The pilot was unable to recall whether the fuel boost pump was activated during the flight.