Primary finding
Probable cause
the pilot's failure to maintain clearance with the wires due to an inadequate visual lookout.
Investigator assessment
Analysis narrative
The helicopter collided with power lines during aerial application operations. The pilot was returning to the service truck for another load [of chemicals]. At the top of a ridge, approximately 500 feet mean sea level, there were two power lines of which he was unaware. During a descent at 60 knots, the helicopter impacted the top wire "about the middle of the bubble." As a result, it pitched forward and the main rotor blade cut the wire and tail boom off in sequence. The helicopter began spinning to the right and the pilot performed an autorotation.
Source record
Factual narrative
On September 9, 2003, at 1215 Hawaiian standard time, a restricted category Hiller UH-12E helicopter, N9792C, collided with power lines during aerial application operations near Kekaha, Hawaii. Murray Ag, Inc., the registered owner, was operating the helicopter under the provisions of 14 CFR Part 137. The helicopter sustained substantial damage; the commercial pilot was not injured. The flight departed a local field at 1200. Day visual meteorological conditions prevailed, and no flight plan had been filed. In a written statement, the pilot reported that he was returning to the service truck for another load [of chemicals]. At the top of a ridge, approximately 500 feet mean sea level, there were two power lines of which he was unaware. During a descent at 60 knots, the helicopter impacted the top wire "about the middle of the bubble." As a result, it pitched forward and the main rotor blade cut the wire and tail boom off in sequence. The helicopter began spinning to the right and the pilot performed an autorotation.