Accident Overview
On November 7, 2017, at 0934 central standard time, a Hughes 369D helicopter, registration N138WH, was not damaged when its external cargo long line severed after contacting a braided steel shield wire suspended between power transmission towers near Sulphur, Louisiana. The two linemen being hoisted on the long line fell approximately 100 ft to the ground and sustained fatal injuries. The helicopter was operated by Winco, Inc. under Title 14 Code of Federal Regulations Part 133 as an external load flight. Day visual meteorological conditions prevailed, and no flight plan was filed. The flight departed at 0932 from a temporary landing zone near the accident site.
According to the power company, the flight's purpose was to install guard ropes between deenergized 500-kilovolt power transmission lines before replacing an existing shield wire. The pilot reported that after a preflight briefing and discussion with one lineman, he hovered to allow the linemen to hook onto the long line, then repositioned to work on the center conductor bundle. After the linemen tied off a guard rope to the center bundle, the pilot moved to work on the northern bundle. The pilot saw the long line contact the shield wire as one lineman held the northern conductor. The long line severed as the pilot turned into the wind and attempted to move the linemen away. The pilot reported that immediately before the severance, one lineman tugged at the conductor to reposition the guard rope. After the line severed, the pilot returned to the landing zone and landed uneventfully. No helicopter malfunctions were reported. Postaccident measurements and witness video indicated the 60-ft long line separated about midspan while in contact with the shield wire.
Pilot Information
The pilot, age 71, held a commercial pilot certificate with ratings for airplane single-engine land, rotorcraft-helicopter, and instrument airplane and helicopter. His most recent FAA second-class medical certificate was issued on June 19, 2017, with no limitations. He had accumulated 25,090 total flight hours, including 21,063 hours as pilot-in-command and 11,286 hours in Hughes 369 helicopters. He flew 26 hours in the 90 days before the accident and 17 hours in the 30 days prior. He had flown less than 1 hour on the accident day. His most recent flight review was completed on August 29, 2016, in a Hughes 369D.
Aircraft Information
The helicopter, serial number 911027D, was manufactured in 1981. It was powered by a 450-horsepower Rolls-Royce 250-C20R/2 turboshaft engine (serial number CAE-295387) and had a maximum gross weight of 3,000 pounds. It was equipped for external load operations and received a standard airworthiness certificate on December 29, 1981. At the time of the accident, the helicopter had accumulated 9,595.1 total airframe hours. The last recorded maintenance was a 100-hour inspection completed on October 29, 2017, at 9,552.7 hours.
Meteorological Information
Day visual meteorological conditions prevailed at the accident site. The nearest weather reporting station, Southland Field Airport (UXL) in Sulphur, Louisiana, about 9 miles south, reported at 0935: wind from 210° at 8 knots, 10 miles surface visibility, broken ceilings at 1,400 ft, 2,400 ft, and 3,000 ft above ground level, temperature 27°C, dew point 23°C, and an altimeter setting of 30.11 inches of mercury.
Additional Information
Local law enforcement reported that the 60-ft synthetic long line severed about midspan. It was not equipped with an abrasion-resistant cover. A 100-ft synthetic long line with an abrasion-resistant cover was found on the ground at the temporary landing zone near the operator's support vehicle.
The operator reported that the flight was conducted under Part 133 Class B, with the linemen considered crewmembers during powerline construction operations. The FAA had approved the helicopter's hook installation, but under Part 133 Class B, the FAA did not regulate, specify, or approve the long line or harnesses used to hoist the linemen.
The operator reported that the long line was a 7/16 inch Amsteel Blue synthetic rope made of Dyneema SK-75 synthetic fiber with a break strength of 21,500 lbs. The operator stated that such synthetic rope had been an industry standard for 15–20 years and is advantageous for powerline work because it is non-conductive and has higher break strength than similarly sized braided steel cable. The operator noted that an abrasion-resistant cover is typically used to protect against incidental contact with sharp tower edges but would not offer much protection during prolonged lateral contact with a braided steel cable. The operator also noted that a braided steel long line is impractical for powerline work due to electrocution risk. The pilot selects the long line length for each mission based on required positioning and obstacle clearance, choosing the shortest available to increase positive control.