On July 27, 2011, about 1540 Pacific daylight time, a Eurocopter AS 350 B3 helicopter, N808LF, sustained substantial damage after being struck by an object in cruise flight near Troutdale, Oregon. The commercial pilot and his five passengers were not injured. The helicopter was being operated by Air Methods Corporation of Englewood, Colorado. Visual meteorological conditions prevailed for the repositioning flight, which was being operated in accordance with 14 Code of Federal Regulations Part 91, and a flight plan was not filed. The flight departed the Aurora State Airport (UAO), Aurora, Oregon, about 1528, with Dallesport Airport (DLS), Dallesport, Washington, as its destination. In a report submitted to the National Transportation Safety Board investigator-in-charge (NTSB IIC), the Air Methods’ Aviation Compliance Manager stated that the aircraft departed from its maintenance facility at UAO to its normal base of operations located at DLS. The manager further stated that about 12 minutes into the flight the pilot reported that he felt something, like a bird strike, and elected to make a precautionary landing at TTD to inspect the helicopter for possible damage. Subsequent to an uneventful landing the pilot performed a walk-around inspection of the helicopter, during which it was discovered that a portion of the tail rotor drive shaft covering was missing. Upon further inspection of the helicopter, it was revealed that a single main rotor blade and two tail rotor blades had been damaged. In a statement provided to the IIC, the Air Methods’ Director of Maintenance (DOM) reported that as a result of his review of the maintenance that was performed on the helicopter prior to the accident flight, that all of the procedures for the 100-hour maintenance task were complied with, which included proper documentation of the work performed, including the required “Confirm Your Aircraft” (CYA) procedure, which was documented in the aircraft maintenance logbook. As provided to the IIC by Air Methods, the CYA requirements are as follows: • Any maintenance performed must be entered in the Air Methods’ Record of Maintenance. For all routine maintenance performed in the field by a company mechanic, a “Confirm Your Aircraft (CYA)” check will be performed. Whenever possible, a mechanic who did not sign off the maintenance action will perform the CYA. If a second mechanic is not available, a pilot will perform the check. • The CYA will include a thorough face-to-face briefing between the person who performed the work and the person performing the CYA. The person performing the CYA is required to do a general overview of the area in which the maintenance was performed. The person should look for disconnected lines, proper safeties (including safety wire, cotter pins, and lock tabs), oil or fuel, any cowlings/panels that were opened/removed, and any components/lines that were repositioned or removed in order to facilitate maintenance. • The CYA check shall be performed before the aircraft is returned to service and will include at a minimum, a general overview for the following: o Loose or missing hardware in the area of maintenance. o Obvious defects in the area of maintenance. o Loose hardware or foreign objects left on the aircraft. The DOM reported that during post-accident discussions with the maintenance staff and the pilot, both felt that the [tail rotor drive shaft] cowling was secured. The DOM further reported that a possible scenario was that the maintenance staff and the pilot looked at the cowling prior to the ground runs and the accident flight and presumed that it was secure and that the work had been reviewed by someone else. The DOM revealed that in order to improve their Air Methods’ operations, the company had implemented a new policy designating a Primary Mechanic when more than one mechanic is working on a maintenance task.