Eurocopter AS 350 B3 N808LF accident near Troutdale, Oregon

Probable cause

The in-flight separation of the tail rotor drive shaft cover as a result of maintenance personnel not ensuring that it was secured after a maintenance inspection; also causal was the pilot’s inadequate preflight inspection of the helicopter.

NTSB analysis

The pilot reported that, about 12 minutes into a repositioning flight following a maintenance task performed by a company mechanic, he felt something that he described as similar to a bird strike. The pilot subsequently elected to make a precautionary landing in order to assess the situation. During an examination of the helicopter after the uneventful landing, the pilot discovered that a portion of the tail rotor drive shaft cover was missing and that one main rotor blade and two tail rotor blades had been damaged. Postaccident discussions with the company’s director of maintenance determined that the maintenance staff (who had recently performed a maintenance inspection) and the pilot likely looked at the tail rotor drive shaft cover prior to the accident flight and presumed that it was secure or had been secured by someone else; however, it was not secure and came off during flight. Following the accident, the company implemented a primary mechanic position into its Field Mechanic Procedures in order to mitigate a similar occurrence.

Text from the NTSB. Open the NTSB docket for WPR11LA352 for the full record.