Incident Overview
On August 5, 2013, at 0915 central daylight time, a Hughes model 369D helicopter, registration N8688F, was not damaged when its external cargo long-line was severed after colliding with a shield wire suspended between power transmission towers near Ackerly, Texas. Two linemen being hoisted on the long-line were fatally injured after falling approximately 200 feet to the ground. The helicopter was registered to and operated by Haverfield Aviation Inc., under 14 Code of Federal Regulations Part 133 as an external load flight. No flight plan was filed. Day visual meteorological conditions prevailed for the local flight, which operated from a landing zone near the accident site.
Flight Details
According to the operator, the helicopter was equipped with a 100-foot external cargo long-line used to hoist linemen onto power transmission towers. Shortly after departure, as the helicopter climbed toward the transmission tower, the long-line collided with a shield wire suspended between towers. The operator reported that the long-line severed about 5 feet above the linemen. The pilot returned to the landing zone and made an uneventful landing. The operator did not report any malfunctions or failures with the helicopter that would have prevented normal operation.
Pilot Report
The pilot reported that during his repositioning flight, he noticed multiple power lines and shield cables erected on tower structures located to the north and west of the tower to be serviced. After landing, he completed a preflight briefing with the two assigned linemen. The helicopter was then brought into a 100-foot hover above the landing zone while the linemen secured themselves to the long-line. As the pilot maneuvered toward the tower, he briefly noticed a slight kink in the long-line before it was severed. The pilot stated that the shield wire installed on the tower had not been identified or discussed during the preflight briefing. He reported that the clear sky and morning light made the shield wire impossible to see from the ground, and that it was uncommon for shield wire to be installed on upper tower structures before lower line work was completed.
Weather Conditions
The nearest aviation weather reporting station was Big Spring McMahon-Wrinkle Airport (KBPG), Big Spring, Texas, about 20 miles southeast of the accident site. At 0915, the automated surface observing system reported wind from 160 degrees at 11 knots, visibility 10 miles, sky clear, temperature 28 degrees Celsius, dew point 16 degrees Celsius, and altimeter setting 30.10 inches of mercury.