inside a bulb interacts with a gas fill containing trace amounts of a halogen material to produce the white light and extend filament life. The source connects directly to the aircraft power source.
Retrofit and replacement
Because halogen sources have traditionally been used for aircraft interior lighting, the necessary fixturing, electrical systems, and backup systems to support them are already in place within most aircraft. Replacing halogen sources with LED clusters requires additional engineering design.
Replacing halogen sources can be easy or difficult, depending on the application. Although some halogen lamps are easily replaced by twisting a front cover off the fixture, some personal service units (PSUs) are difficult to access and disassemble. Retrofitting LEDs requires replacing an entire lighting module; here again, the complexity of the task depends upon the application. It is important to note, however, that if an LED source does not last the lifetime of the aircraft, very expensive labor and material charges will occur with a repair or replacement.
Cost of ownership
Evaluating the cost of ownership of each technology is a science in itself. The following list enumerates the factors that decision-makers need to consider before selecting a particular type of light source for a specific task:
- Source initial purchase price.Original installation cost, including labor.Cost of energy consumed by the light source.
- Cost of energy consumed by additional electronics required.
- Number of light sources required to generate a specific amount of light. (How many halogen sources vs. how many LED modules, to produce an equivalent result for a particular task?)
- Maintenance costs, both labor and material, for upkeep of source components throughout lamp lifetime. (Factors such as dust on the lenses, yellowing of lenses, and replacement of lamp electronics.)
- Replacement cost of failed unit.
- Inventory costs of holding repair parts.Labor costs associated with replacing a failed unit.
In selecting either a halogen or an LED source for a particular application, decision-makers must consider many factors. The emergence of LED technology provides additional options for interior aircraft lighting design, but maintenance issues over the lifetime of the aircraft require that the benefits and shortcomings of each technology be considered. Initial purchase price of a particular source is also an important consideration, but factors such as long-term cost of both labor and materials and complexity of maintenance must be factored in as well. Choosing a source for a particular aircraft interior lighting task should depend, ultimately, on a consideration of the illumination task in conjunction with a thorough cost and benefit analysis.
Doug Rutan is the Original Equipment Marketing Manager for the Lighting Products Group of Welch Allyn Inc., Skaneateles Falls, New York. He has more than 20 years of experience in electrical product engineering, design, and program management in the lighting industry, and has been granted multiple U.S. patents.
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