Primary finding
Probable cause
A loss of engine power due to fuel starvation as a result of blocked fuel vents.
Investigator assessment
Analysis narrative
The pilot topped off the fuel tanks prior to takeoff. Approximately two hours later, a loss of engine power was experienced. The pilot performed an autorotation to a field; however, the tail rotor contacted a 4x4 wooden post during the landing. This resulted in substantial damage to the tail boom. Inspection of the helicopter revealed the left fuel tank was empty and the right fuel tank was full. Inspection of the fuel system revealed the right tank fuel vent was completely blocked by mud dauber debris along with the remains of two mud daubers. The left fuel tank vent was partially blocked by mud dauber debris. Both tanks feed to a central line which provides fuel to the engine. In addition, the nut on the T-fitting from the left tank fuel line was found finger tight.
Source record
Factual narrative
The pilot topped off the fuel tanks prior to takeoff. Approximately two hours later, a loss of engine power was experienced. The pilot performed an autorotation to a field, however, the tail rotor contacted a 4x4 wooden post during the landing. This resulted in substantial damage to the tail boom. Inspection of the helicopter revealed the left fuel tank was empty and the right fuel tank was full. Inspection of the fuel system revealed the right tank fuel vent was completely blocked by mud dauber debris along with the remains of two mud daubers. The left fuel tank vent was partially blocked by mud dauber debris. Both tanks feed to a central line which provides fuel to the engine. In addition, the nut on the T-fitting from the left tank fuel line was found finger tight.