UF Researchers Build A Runway As A Landing Zone For Lightning Bolts

Source: Vladimir Rakov (352) 392-4242E-mail: rakov@admin.ee.ufl.edu

GAINESVILLE, Fla. --- After designing and building their own runway, equipped with typical lighting, signs and surface area, University of Florida engineers now plan to wreak electrical havoc on their new creation by causing lightning to strike it.

The provoked bolts of electricity will help researchers study the effects of lightning strikes on existing runway lighting systems and develop new protective measures.

The 300-foot experimental runway, built at UF's lightning research facility at Camp Blanding near Starke, is a fraction of the size of a typical runway. Part of its surface is paved with asphalt and the other part with concrete.

The Florida Department of Transportation's Aviation Division is sponsoring the study, asking UF scientists to recommend improved standards for lightning protection. Officials are concerned not only with the expensive damage caused by lightning, but also with the potential danger to pilots, especially at small airports.

"At most small airports, there are no personnel and runway lights are operated by the pilots with remote control," said Vladimir Rakov, associate professor of electrical and computer engineering at UF and lead investigator of the project. "If someone tries to land at night after lightning has knocked out the power, what happens next will depend on how much fuel the pilot has left."

During Florida's peak summer thunderstorm season, researchers will launch rockets into dark, threatening skies from various positions on the runway. Each rocket will trail a grounded thin wire coated with Kevlar, a strong material used in things such as bulletproof vests. When a rocket initiates lightning, the bolt of electrical current follows the wire down to the runway through a lightning rod attached to the launcher.

Before launching, engineers measure the electrical field at ground level to determine if a sufficient electrical charge has accumulated in the clouds.

"It's true that tall objects are more likely to be struck by lightning," Rakov said. "We just create a temporary tall object by shooting the wire toward the clouds."

The two surfaces, as well as two lighting systems, were designed to simulate different airport conditions, said Ralph Ellis, an associate professor of civil engineering at UF who was responsible for the design and construction of the model runway. He said the installation conforms to current Federal Aviation Administration (FAA) standards.

Design and construction of the project took about one year, said Ellis, whose team included faculty and students from UF's civil engineering department.

Two runway lighting systems are accepted by the FAA, Rakov said. With one, each light is placed on a stake in the ground with its transformer and the power cable buried in a trench along the runway perimeter. The more expensive system calls for each light to be mounted on a metal can housing the transformer. The power cable is placed in protective PVC piping before it's buried in the soil.

Most small Florida airports use direct buried cables and stake-mounted lights, Rakov said. Both lighting systems were installed for UF's project to determine if one is better at surviving lightning.

The FAA currently requires all airports to use a specific lightning protection procedure designed to draw the lightning away from the electrical circuit. It consists of a bare copper wire buried 4 inches above the power cable and attached to vertical rods installed around the entire circuit. The required wire, called a counterpoise, is connected to each light fixture and to the power source grounding system. But, Rakov said, such a configuration could make things worse.

"There is no consensus on if it's protecting or not," Rakov said. "This is the first thing we'll find out. We'll test the FAA standard, and then we'll install an alternative protection system and test again to see if it does any better."

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