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Airports Alaska Airlines at Seattle Tacoma Airport

Alaska Airlines boosts visibility,
saves energy with prismatic luminaires
operated in electronic ballasts


Aircraft maintenance hangars must have high levels of visibility and good color rendering in order for personnel to detect defects in airplanes and make repairs. Alaska Airlines recently retrofit the lighting in two of its maintenance hangars at Seattle Tacoma International Airport so the light levels would be consistent with Illuminating Engineering Society (IES) standards.

“Poor illumination levels and color rendering can obscure or mask the appearance of items that would otherwise be perceptible,” said Ray Wuco, manager, special projects, Alaska Airlines. “Additional, proper illumination levels and color accuracy have a positive affect on workers’ energy levels and their productivity.”

The older of the two hangars, which is 32,000 square feet, was originally illuminated with twin-pack 800-watt mercury vapor fixtures that had been installed during the 1960s. The fixtures were later retrofit with new Holophane ballasts that allowed the units to be used with single 400-watt high-pressure sodium (HPS) lamps. Eventually, the fixtures were re-lamped with metal halide lamps compatible with the high-pressure sodium ballasts and igniters. According to Wuco, the latter change improved the color rendering, but the illumination levels remained low.

The newer hangar, which is 66,000 square feet, was initially illuminated with 1,000-watt HPS fixtures. While the illumination levels in this facility were higher than in the older hangar, they were still below acceptable levels. The HPS lamps were also unable to provide the color accuracy desired.

Foy Industrial Electric Corp. of Seattle, Washington installed tandem Prismpack V‚ luminaires from Holophane with pulse start Prismatron‚ electronic ballasts in both Alaska Airlines hangars. The luminaires are used with General Electric Lighting 400-watt Constant Color ceramic metal halide lamps, which have a color-rendering index of 92.

Steffen Teichmann P.E., electrical engineer, Casne Engineering, Bellevue, Washington, indicated the Prismpack V luminaires with the Prismatron ballasts were selected because General Electric offers an extended warranty when its lamps are used with the Prismatron ballast.

“General Electric guarantees higher lumen maintenance when the lamps are operated on the Prismatron ballasts,” Teichmann said.

Luminaires in the older hangar are spaced approximately 17 feet between rows and 15 1/2 feet between fixtures in each row. Fixtures in the newer hangar are spaced approximately 18 1/2 feet between rows and 14 feet between the luminaires. Mounting heights are 45 feet in the older hangar and 65 feet in the newer facility.

According to Wuco, some of the fixtures in the newer hangar had to be repositioned because of the location of seismic bracing, a bridge crane and a teleplatform system. The luminaires were moved so they were not shaded by these overhead structures.

Illumination levels in the older hangar are 105 footcandles, which is about 10 footcandles higher than expected. The system was designed with higher illumination levels than required to ensure that the levels would not drop below the targeted minimum of 75 footcandles when the luminosity of the lamps degrade as they approached the end of their rated life.

“When we designed the lighting system, we were not as concerned about reducing energy as much as achieving the higher illumination levels,” said Wuco. “However, the energy savings resulting from using the solid state electronic ballast rather than a standard magnetically ballasted system will result in annual savings of nearly $16,000. This is based on a conservative consumption rate of 30 watts per Prismatron ballast compared to 65 watts per standard magnetic ballast on a one-to-one basis. Additional savings will be realized as a result of daylight photo sensors that were installed. These photo sensor will sequentially shut down banks of lights depending on the amount of light coming into the hangars from outside.”

Except for a weekly rest period as recommended by the lamp manufacturer and photo sensor shut downs, the Prismpack V luminaires are illuminated 24 hours a day, seven days a week throughout the year.

“Using the Prismpack V luminaires with the GE lamps allowed us to provide higher levels of illumination to create a brighter and more comfortable environment,” said Wuco. “Because of the increased lumen output and lamp life, we were able to design the system with considerably fewer fixtures than would have been required if we had used a standard magnetically ballasted system. Again, additional savings in recurring energy consumption as well as lighting system cost were realized with this system.”


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