Eurocopter AS 350 B2 N696BH accident near New York, New York

Probable cause

The failure of maintenance personnel to properly secure one tail rotor pitch change link to its respective tail rotor blade resulting in an in-flight separation of the link from the blade. Contributing to the accident was the lack of an adequate post-maintenance inspection procedure.

NTSB analysis

Shortly after takeoff, the pilot of the helicopter reported feeling a vibration through the airframe including the anti-torque pedals and cyclic. With positive control of the helicopter, he safely landed at a nearby heliport. After touchdown, while shutting down and applying the rotor brake, he noted that the vibration increased dramatically as the rotor speed decreased to a stop. Upon a cursory inspection of the helicopter after shutdown, the pilot noticed that one pitch change link of one tail rotor blade was separated from its respective attach point at the blade, and the blade was out of its normally installed position. Further inspection revealed a hole in the right side of the tailboom and the tailcone was damaged consistent with the tail rotor blade contacting the tailboom. The securing hardware (consisting of the bolt, castellated nut, and cotter pin) of the separated pitch change link were not found. The opposite tail rotor blade pitch change link was found properly connected at both ends, with both ends secured by cotter pins. Inspection of the tail rotor assembly by the Safety Board’s Materials Laboratory revealed no evidence indicating that the missing bolt had fractured or was properly installed and secured with a cotter pin.

Several days before the accident a mechanic had inspected the tail rotor pitch change links of the helicopter for end play and he was advised by the company's Director of Maintenance that the bearing of the tail rotor pitch change spider assembly needed to be replaced. The mechanic stopped his inspection and the work to the tail rotor pitch change spider assembly was completed the next morning at which point the tail rotor assembly was installed. There was no record of a post-maintenance inspection of the replaced pitch change link assembly at the tail rotor blade attach point. Additionally, the operator at the time did not have a Required Inspection Items (RII) program on their Federal Aviation Administration Approved Aircraft Inspection Program, and if they had, it is likely that a RII inspection by a trained mechanic would have detected the missing cotter pin upon completion of the replacement maintenance performed on the pitch change link assembly. Following the accident, the operator implemented a Lockout/Tagout procedure to ensure its aircraft are not returned to service before the RII program is completed.

Text from the NTSB. Open the NTSB docket for ERA10LA118 for the full record.