Robinson Helicopter R22 BETA N10786 accident near West Palm Beach, Florida

Probable cause

Separation of the auxiliary fuel tank cap, which entered the tail rotor system. Contributing to the accident was the lack of a fuel tank cap restraint.

NTSB analysis

During initial climb, about 200 feet above the ground, the helicopter's auxiliary fuel tank cap separated and entered the tail rotor system. The tail rotor became unbalanced and partially separated. The pilot subsequently entered an autorotation as the horizontal and vertical stabilizers also separated, and the helicopter landed hard. The auxiliary fuel tank cap was not serviced prior to the accident flight and the pilot reported that he checked the security of the auxiliary and main fuel tank caps during preflight inspection. The separated fuel cap was recovered and did not contain a restraining chain and gasket. The main fuel tank cap remained secured throughout the accident sequence and examination of that cap revealed that it did contain a gasket but not a chain. The helicopter manufacturer ceased installing restraining chains about 18 years prior to the accident; however, the accident helicopter was produced about 10 months before that and should have left the factory with fuel tank cap restraining chains. Review of the helicopter's maintenance records did not reveal any instance of the fuel cap restraining chains being removed in the field. Additionally, the investigation could not determine if the auxiliary fuel tank cap gasket was absent prior to the accident flight or separated during impact with the tail rotor.

Text from the NTSB. Open the NTSB docket for ERA11LA392 for the full record.