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
To some people, it would be cause for much grief, this Hughes MD 500 helicopter sitting in the hangar, rotor blades snapped, tail boom sheared off, Plexiglas cockpit nose broken. Repairs will cost at least $160,000.
But to Darryl Ed, president of Haverfield Corporation of Gettysburg, Pennsylvania, a helicopter company that maintains power lines, it’s nothing to mope about. He says the fact that the two men on board walked away largely unscathed was due to world-class piloting—under the circumstances.
The circumstances were this: Pilot Dennis Anderson’s job that day last April was to hover the MD 500 a few inches from a live 230,000-volt power line west of Chicago so that an electrician sitting on a platform on the side of the helicopter could work on the line from the air. The helicopter’s rotor blades overlapped the power line. The Allison turbine engine quit suddenly, leaving the rotors spinning only from inertia. In the second or two before the Hughes settled enough to put the rotors into the power line, the lineman disconnected his equipment from the line. At the same moment, Anderson banked the aircraft sideways. It whirred toward the ground a hundred feet below, gathering speed.
When an engine quits, helicopter pilots wish for a surfeit of altitude or speed. In an unpowered descent—called an autorotation—either will allow the free-spinning rotor to build up enough rpms for the pilot to soften the landing by pulling up the collective lever at the last moment. This causes the rotor blades to dig into the air and slow the descent. But when an engine quits at 100 feet, the options are few.
Anderson aimed toward a patch of swamp, the softest spot in the immediate area. The MD 500 hit the ground so hard the rotor blades bowed downward and chopped off the tail boom. The front of the skids sank into the mush, leaving the helicopter in a showy headstand. It was a fortunate anticlimax. Anderson had missed the power line and even saved the helicopter fuselage. It was not a routine day, but little is routine in the live-line bare-hand maintenance business.
The U.S. power grid has nearly 160,000 miles of high-tension transmission lines, each line carrying 230,000 volts or more. Sooner or later such lines need attention, which might entail changing out hardware hanging on the lines, stringing fiber optic cable, or excising short sections of worn wire and splicing in new.
Big transmission lines usually have three “conductors” consisting of two or more closely spaced wires. The conductors run parallel, separated by 20 feet or so, and hang from bell-shaped ceramic insulators, which are suspended from the arms of steel towers. Previously, linemen climbed up the towers and clambered along the conductors, but this required the power company to shut the power off first. Today, power companies prefer not to shut down transmission lines for routine maintenance, because closing down a 500,000-volt line, for example, can run as high as $50,000 per megawatt hour in replacement power costs.
That’s where helicopters come in, flitting from span to span like big hummingbirds—a sight that often prompts onlookers to call police and report that helicopters are stuck in the power lines. A lineman can perform many operations from a helicopter—while the juice is on. Today, hundreds of crews worldwide are doing “helicopter live-line bare-hand maintenance.” In this country, the work is done by a handful of contractors and by utility companies.