Primary finding
Probable cause
The pilot’s failure to maintain sufficient altitude to clear power lines while maneuvering at low altitude. Contributing to the accident was the pilot’s failure to follow company operating specifications for minimum altitude.
Investigator assessment
Analysis narrative
The helicopter crewmembers were returning to their home base after transporting a patient. The pilot was flying the helicopter at en route altitudes of around 80-100 feet above ground level and struck power lines; he was not following company operating specifications of a minimum altitude of at least 300 feet. The pilot reported that he did not observe the wires until after the initial impact and was able to land the helicopter off airport without incident.
Source record
Factual narrative
On November 15, 2012, about 0700 mountain standard time, a Bell 407 helicopter, N7160V, sustained minor damage when it struck high tension power lines during cruise flight near Riverton, Wyoming. The helicopter was registered to Classic Medical Inc., and operated by Classic Helicopter Group, LLC, under the provisions of Title 14 Code of Federal Regulations Part 135. The airline transport pilot and two medical crew members were not injured. Visual meteorological conditions prevailed and a company visual flight rules flight plan was filed for the flight. The flight originated from the Wyoming Medical Center Heliport (WY57) Casper, Wyoming at 0633 with a planned destination of Riverton Regional Airport (RIW) Riverton, Wyoming. The helicopter medical crew members reported that they were returning to their home base after transporting a patient. One medical crew member reported that the ambient lighting conditions were good and no night vision goggles were in use. The pilot reported that he did not observe the wires until after the initial impact and was able to land the helicopter off airport, without incident. The medical crew member seated in the front left seat observed the wires but did not have sufficient time to warn the pilot prior to impact. Examination of the helicopter by a Federal Aviation Administration inspector revealed that the main rotor blades, tail rotor and swashplate sustained minor damage. The company investigation revealed that the pilot was flying the helicopter at en route altitudes of around 80-100 feet above ground level. The company Operations Specifications (OPSEC) require an altitude of a least 300 feet above terrain and obstacles during day operations.