Siemens Helps Solve Taxiway Lighting Challenge at O'Hare

Author: 
Rebecca Douglas
Published in: 
July-August
2008

When a light goes out at home, a quick bulb change usually fixes the problem. On an airfield, it's rarely that simple. At O'Hare International Airport, it's even more challenging.

A system that keeps snow and ice off two taxiway bridges at the bustling Chicago airport presents the unique challenge. The system pumps oil through a series of pipes just under the surface of the bridges to keep the pavement warm. It also, however, limits the depth of in-pavement lighting fixtures that can be used.

For years, the shallow 1 ¼-inch deep bases didn't present a problem. As the original in-pavement fixtures aged, however, they became more susceptible to leaks, which eventually required maintenance crews to be out on the taxiway multiple times a month. More recently, replacement parts for the approximately 25-year-old system became increasingly difficult to find, so O'Hare needed a new strategy. The Department of Aviation consequently asked Siemens Airfield Solutions to design a new system specifically for O'Hare.

No More Square Pegs

Siemens engineers devised a way to use the existing bases and improve the quality of lighting on the taxiway bridges at the same time.

"Current fixtures wouldn't fit into the shallow bases, which were designed for old halogen bulbs; so we modified a Light Emitting Diode (LED) fixture by removing the electronics and relocating them to a separate metal box further underneath the bridges," explains Glenn Morrow, Siemens' product engineering group leader and lead engineer for the O'Hare project.

The new LEDs, he explains, provide narrow bands of green light - a dramatic improvement over the previous white halogen lights that were covered with green filters.

"The old technology produced a washed out green," he notes. "The new LEDs provide a crisp, more saturated green. This provides better continuity from the LEDs on the regular taxiway to the bridge. It's just one less thing for pilots to worry about when visibility is bad."








Facts and Figures

Project: Taxiway bridge lighting

Location: O'Hare International Airport

Supplier: Siemens Airfield Solutions

Installation: Three nights

Of Note: Existing in-pavement bases were too shallow for current fixtures, so electronics were separated to make lights fit.

After Siemens' system was approved by the FAA, electrical staff from the Department of Aviation installed 46 new lighting fixtures - 23 on each bridge - last September. Crews worked for three nights when aircraft operations were at a minimum due to noise abatement policies.

Siemens delivered the modified fixtures to the airport with upgraded cable already attached to facilitate a smooth installation and prevent problems from moisture wicking into the fixtures.

"They mounted the new fixtures on the existing bases and pulled our cables through the conduit and hooked them into the electrical boxes underneath the bridges," explains Morrow.

Eyes on the Horizon

A less-frequent maintenance cycle for bulb replacement is another benefit O'Hare will experience with its new in-pavement bridge lighting. Each LED is expected to last more than 150,000 hours under typical airport conditions - years of use, according to Siemens.

While the LED system has resolved the airport's initial problem, there is still an issue to be addressed. Despite the liberal use of a resin potting compound to seal the bottom of the fixtures, moisture has occasionally intruded. Preliminary tests lead Morrow to believe the problem stems from an inconsistent fixture interface surface on the existing bases.

"Some of the old bases were installed a little deeper than others," he explains. "Over the years, a variety of non-standard spacers have been used to get the fixtures to a FAA-specified installation height. When aircraft roll over the top, the unit may flex, and the flexing can compromise the seals used to eliminate moisture penetration. The fixture mounting interface to the base must be evenly distributed 360° over a base's entire mounting flange. We are currently conducting tests to confirm this is the problem. If so, reworking the bases to provide the 360° evenly distributed mounting surface should resolve the issue. "  

Subcategory: 
Runway/Ramp

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