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© Mechanik / Airfield Lighting The long-term performance of LEDs Jean Paul Freyssinier provides a detailed summary of the Lighting Research Center – Rensselaer Polytechnic Institute’s work on understanding the useful life of airfield LED luminaires In just the past few years we have seen light- generation LEDs were able to provide suitable makers because it can translate into more emitting diodes (LEDs) make impressive solutions compared to traditional reliable operations and reduced maintenance progress in terms of light output, colour incandescent sources. Thus, with the potential costs, especially considering the demanding properties, efficacy (measured in units of light to improve visibility to pilots (see ‘LEDs and conditions found in airports. However, (lumens, lm) per electric watt, or lm/W), and human factors’ on page 40), energy savings, LED luminaires (fixtures), and in particular potential for long life. These improvements, and long life, airports throughout the world are airfield luminaires, are relatively new to the paired with significant reductions in costs, have transitioning to LED-based solutions at an market and no sufficient long-term performance resulted in many more applications using LEDs, increasing rate 1,2 . test results are currently available 2 . Notably, at from consumer electronics to cars to general illumination indoors and out. For aviation lighting, the use of LEDs has Now that the light output and efficacy of LEDs has met or surpassed those from other this time there is no definition of ‘useful life’ specific to aviation lighting products. light sources, the focus in most applications, always been a sensible option because LEDs including aviation lighting, has shifted to other are particularly suited for applications in need important issues, such as long-term Why do we need a definition of useful life? of coloured light and because signals and performance, system reliability, and initial While LEDs could last for many thousands of other visual aids in airports do not require cost. The potential for long life is particularly hours under certain conditions, the life of much light output necessarily, so even early relevant to airport administrators and decision- the LED itself, and more importantly, that of 38 Volume 18 · Issue 2 · 2014