Event Details
On July 27, 2011, at approximately 1540 Pacific daylight time, a Eurocopter AS 350 B3 helicopter, registration N808LF, was in cruise flight near Troutdale, Oregon, when it was struck by an object, resulting in substantial damage. The commercial pilot and five passengers were not injured. The helicopter was operated by Air Methods Corporation of Englewood, Colorado, and was being repositioned from Aurora State Airport (UAO) in Aurora, Oregon, to Dallesport Airport (DLS) in Dallesport, Washington. The flight departed UAO at 1528 under visual meteorological conditions in accordance with 14 Code of Federal Regulations Part 91, and no flight plan was filed.
Pilot Report
According to a report submitted to the National Transportation Safety Board investigator-in-charge (NTSB IIC) by Air Methods' Aviation Compliance Manager, about 12 minutes into the flight, the pilot reported feeling something akin to a bird strike and elected to make a precautionary landing at Troutdale Airport (TTD) to inspect the helicopter. After an uneventful landing, a walk-around inspection revealed that a portion of the tail rotor drive shaft covering was missing. Further inspection showed damage to one main rotor blade and two tail rotor blades.
Maintenance Procedures
In a statement to the IIC, Air Methods' Director of Maintenance (DOM) reported that a review of the maintenance performed on the helicopter prior to the flight indicated all procedures for the 100-hour maintenance task were complied with, including proper documentation and the required "Confirm Your Aircraft" (CYA) procedure. The CYA requirements, as provided by Air Methods, include documenting any maintenance in the Record of Maintenance, performing a CYA check for routine field maintenance by a mechanic different from the one who performed the work (if possible, otherwise a pilot), and conducting a thorough face-to-face briefing followed by a general overview of the maintenance area to check for disconnected lines, proper safeties, oil or fuel, opened cowlings, and any repositioned components.
Post-Accident Findings
The DOM reported that during post-accident discussions with maintenance staff and the pilot, both indicated that the tail rotor drive shaft cowling was believed to be secured. The DOM described a possible scenario where the maintenance staff and pilot looked at the cowling prior to ground runs and the accident flight and presumed it was secure and that the work had been reviewed by someone else. To improve operations, Air Methods implemented a new policy designating a Primary Mechanic when more than one mechanic works on a maintenance task.