Primary finding
Probable cause
The inflight collision with a bird(s).
Investigator assessment
Analysis narrative
The pilot said the helicopter was in cruise flight when it yawed suddenly and began vibrating. After making a precautionary landing, the pilot inspected the helicopter and found two of the three tail rotor blades were bent, and the drive shaft was bent 24 degrees. Feathers and bird remains were found in the tail rotor system. A Denver Zoo avian said they were down feathers but could not identify the bird species.
Source record
Factual narrative
The pilot said the helicopter was in cruise flight at 7,800 feet msl (mean sea level), or approximately 300 to 400 feet above the ground, when it suddenly yawed and began vibrating. After making a precautionary landing, the pilot inspected the helicopter and found two of the three tail rotor blades were bent, and the drive shaft was bent 24 degrees. Feathers and bird remains were found in the tail rotor system. A Denver Zoo avian said they were down feathers but could not identify the bird species.