NTSB Factual Report

On November 7, 2017, at 0934 central standard time, a Hughes 369D helicopter, N138WH, was not damaged when its external cargo long line severed after contacting a shield wire suspended between power transmission towers located near Sulphur, Louisiana. The two linemen who were being hoisted on the long line were fatally injured when they fell about 100 ft to the ground. The helicopter was registered to and operated by Winco, Inc., under the provisions of 14 Code of Federal Regulations Part 133 as an external load flight without a flight plan. Day visual meteorological conditions prevailed for the local flight that departed at 0932 from a temporary landing zone located near the accident site.

According to the power company, the purpose of the flight was to install guard ropes between the deenergized power transmission lines before the existing shield wire from the nearby transmission tower was unsecured. The east/west power transmission lines crossed perpendicular over North Claiborne Street. There were three sets of bundled conductors (northern, center, and southern). The pilot reported that following a preflight safety briefing he and one of the linemen discussed the expected work tasks. The pilot stated that following his discussion with the lineman he brought the helicopter into a hover above the linemen to allow them to hook onto the external cargo long line. He then repositioned the helicopter to allow the linemen to work on the center conductor bundle. The pilot reported that after the linemen had tied-off the guard rope to the center conductor bundle, he repositioned the helicopter to allow work on the northern conductor bundle. The pilot reported that he saw one of the linemen grab hold of the conductor, and at the same time he also observed the long line in contact with the shield wire. The pilot stated that the long line severed as he turned the helicopter into the wind and attempted to coax the linemen away from the northern conductors. The pilot reported that immediately before the long line severed he observed one of the linemen tugging at the conductor in an attempt to reposition the guard rope perpendicular to the conductors. After the long line severed, he returned to the landing zone and made an uneventful landing. The pilot did not report any malfunction or failures with the helicopter that would have prevented normal operation. According to postaccident measurements made by local law enforcement and witness video footage of the flight, the 60 ft long unsheathed long line separated about midspan while it was in contact with the braided steel shield wire suspended between power transmission towers.

The nearest aviation weather reporting station was located about 9 nautical miles south of the accident site at Southland Field Airport (UXL), Sulphur, Louisiana. At 0935, the UXL automated surface observing system reported: wind from 210 degrees at 8 knots; visibility 10 miles; broken ceilings at 1,400 ft above ground level (agl), 2,400 ft agl, and 3,000 ft agl; temperature 27°C; dew point 23°C; and an altimeter setting of 30.11 inches of mercury.