Helicopter pilots play chicken with high-voltage power lines so crews can work on live wires.
- By James R. Chiles
- Air & Space magazine, March 2001
(Page 2 of 5)
It sounds insane, especially to pilots, who are taught to steer well clear of power lines. Live-line maintenance was featured on the History Channel’s “Suicide Missions” series last year. “TV shows portray this as seriously dangerous work, like lion taming, but that is not at all the case,” says Bob Feerst, president of Utilities/Aviation Specialists, a company that trains crews and audits flight operations for safety. “It’s very safe if the crews follow procedures and the people are trained.” Done right, Feerst says, it’s no more dangerous than working from the bucket trucks that raise linemen to the wires.
Which is not to say that it offers room for mistakes. In the last six years, helicopter live-line maintenance accidents have claimed three lives. “If you factor out deep space and covert military action under enemy fire,” Feerst says, “operating in the utility wire environment is the most demanding flying, by far, and needs the most skill from the pilot and crewman.”
In 1979, Michael Kurtgis was transporting Florida Power and Light employees as the company’s chief helicopter pilot. He considered the time that conventional crews spent setting up and breaking down for even simple power line tasks, and figured that a helicopter could speed things up immensely. He approached his managers and two helicopter manufacturers with the idea of working on live transmission lines from a helicopter and proposed some trial runs, since no one had ever tried flying so close to wires—not on purpose, that is. “They thought I was out to lunch,” he says. Kurtgis resigned to start his own power line maintenance contracting company, USA Airmobile in Fort Lauderdale, and patented his methods, but couldn’t prove his idea would work because no power company would allow him to connect his helicopter to an energized power line—that is, establish an electrical connection between the conductive helicopter frame and power line, equalizing the electrical potential so that whatever—or whoever—touches the line won’t get shocked.
Nearly two years went by before Kurtgis got his chance. In early 1981, USA Airmobile won a contract to power-wash insulators on a 115,000-volt line in Dammam, Saudi Arabia. One day during the job, Kurtgis, ready to start work in a Bell 206 JetRanger, had an impulse: He called over the intercom to crewman Jim True, “It’s now or never.” Out here, there was no one to put up roadblocks. “We’ll never get this kind of chance again,” Kurtgis said.
True asked Kurtgis whether he was really sure this would work. Kurtgis said he was pretty sure.
Nobody in a helicopter had physically connected with a live, high-voltage conductor, and the people that Kurtgis had talked to weren’t sure what would happen. A short circuit from high-tension lines to the ground, perhaps through a fallen tree, is enough to blow the tree apart. Would connecting the line to a helicopter stun the crew, or ignite fumes in the fuel tank? A Florida Power manager predicted that a voltage surge would short out the helicopter’s electrical bus.
Airmobile crews had already worked close enough to energized lines to learn that protective clothing is a must. Kurtgis had a close encounter with a 500,000-volt line before he had even tried to touch any energized lines from a helicopter. “It was like a whole bunch of fire ants were biting you,” he recalled. What had bitten him was “induced current.” High-voltage power lines create a very strong electromagnetic field that reaches far beyond the three conductor wires. This field is not so much a byproduct of the current as a carrier of the current itself. Anyone in the immediate vicinity, like the pilot in a hovering helicopter, is in this field and will feel an induced current along his skin regardless of whether he touches the power line. The sensation is itchy at lower voltages and distinctly painful at higher voltages. Kurtgis learned that a suit of conductive clothing—Nomex fabric with a weave of 25 percent fine-mesh stainless steel wire—allows the current to flow around the skin.
When Kurtgis sidled the JetRanger close enough, True swung the conductive metal boom of the power washer over to the 115,000-volt power line, causing an arc and the attendant buzzing noise as the arc hit the boom. The arc jumps because the helicopter has a different electrical potential than the power line, and the voltage wants to jump across the air gap to equalize them. Even though he expected an arc, True yelped in surprise, but they were still in the air. Once that connection was made, it was easy to “bond” to the line—attach a cable from the helicopter frame to the line to maintain a good electrical connection between the two. Using such techniques, crews have connected the frames of their helicopters to power lines carrying a million volts.