If you’ve ever spotted those colorful balls hanging from power lines and wondered what they were for, you’re not alone. These objects, known as visibility marker balls or marker balls, serve an important purpose for aircraft safety.
According to electric utility company Edison International, marker balls are used to make power lines more visible to low-flying planes and helicopters. These marker balls are typically found near mountain passes, deep valleys, major freeway crossings, and airports – places where aircraft often fly at lower altitudes and are at risk of colliding with hard-to-see cables.
The Federal Aviation Administration (FAA) regulates marker balls and has specific guidelines for their use. For example, marker balls must be at least 36 inches in diameter on wires that cross canyons, lakes, and rivers. But the FAA allows 20-inch marker balls on power lines that are less than 50 feet above the ground and within 1500 feet of an airport runway end. Marker balls should also be spaced evenly at roughly 200-foot intervals along regular wires, and with closer (30- to 50-foot) intervals on wires near runway ends.
In addition to their size, marker balls are also required to be a specific color depending on the number on a given wire. If there are fewer than four marker balls on a wire, they should all be “aviation orange,” the fluorescent hue commonly seen on communication towers. Otherwise, marker balls should alternate between orange, white, and yellow to provide the highest level of visibility to approaching aircraft.
According to a 1983 article from United Press International, marker balls first gained popularity in the 1970s when Arkansas’s then-governor, Winthrop Rockefeller, noticed electric wires while landing his aircraft and realized they needed to be more obvious to pilots. In addition to their benefits for aviation, marker balls also help geese and boats avoid inconspicuous cables.
But how are these marker balls installed on hard-to-reach power lines? It’s a job that requires the help of a helicopter and a skilled technician. The technician is hoisted up by the helicopter and uses specialized equipment to attach the marker balls to the wires. It’s a challenging and potentially hazardous task, but someone has to do it to ensure the safety of both aircraft and the electrical infrastructure.
So, the next time you see marker balls on power lines, you’ll know they serve an important function for aircraft safety and the protection of electrical infrastructure. And the next time you spot a helicopter hovering near power lines, you’ll know a dedicated technician is hard at work installing these vital marker balls.
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