Issues With Use of Airfield LED Light Fixtures (2012)

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10 Summary In general, both the responses to the survey questionnaire (Appendix B) and the published literature suggest that there are some important issues that might be considered when an airport is preparing to install LED airfield lighting: • Installation of LED airfield lighting fixtures appears to be no more difficult than installation of incandescent fixtures. Training programs and technical symposia with information about LEDs are available, and several of these are listed in Appendix D. • Compatibility between LED airfield light fixtures and existing electrical infrastructure designed to operate incandescent lighting systems can arise. Checking with the manufacturer of the LED systems before installing to ensure compatibility with existing regulator and con- trol equipment is important. • It is often important to develop a strong working rela- tionship with the manufacturers of LED lighting fixtures to assist with troubleshooting and potential unforeseen issues during the installation process. Pittman (2010) reports that at Raleigh–Durham International Airport (North Carolina) the manufacturer became a key mem- ber of the LED installation team and was frequently consulted throughout the process. LED InStaLLatIon ExpEctatIonS According to the individuals who participated in the synthe- sis survey, the primary reasons for installing LED airfield lighting were to reduce maintenance costs (20 respondents), to reduce energy use (18 respondents), and to improve vis- ibility of airfield lighting (13 respondents). Interestingly, none of the survey respondents indicated that the reasons included any legislative mandate. Although national energy legislation, such as the EISA of 2007, increasing the lumi- nous efficacy requirements for general service lamps will make many existing incandescent lamps noncompliant over the next decade, this legislation appears to have little impact on the decision making of airports with respect to lighting. This is likely in part because the legislation contains exclu- sions for specialty light source types such as rough service and for some critical applications, such as airfield lighting (NRDC 2011). reduced maintenance Anticipation of reduced maintenance was also referred to fre- quently in the literature. At Copenhagen Airport, it was stated that recently installed LED obstruction lights were expected to last 100,000 hours, substantially longer than the 2,000-hour life reported for their incandescent counterparts (Stegmann 2010); and an operating guarantee from the manufacturer of five years was reported. The Airports Council International (2007) re- ported that LED taxiway lights were expected to reduce main- tenance costs over incandescent versions at Vancouver Air- port. LED stop bars at Newcastle International Airport (United Kingdom) were expected to increase maintenance cycles for these systems from a few months to six years (Marsh et al. 2008). Similar expectations were in place for LED taxiway and run- way lighting at Burlington (Vermont) International Airport (Edelstein 2009), Stewart International Airport (Little Rock, Arkansas) (States News Service 2009a), Trenton–Mercer Air- port (New Jersey) (TendersInfo 2010a), San Bernardino (Cal- ifornia) International Airport (TendersInfo 2010b), Raleigh– Durham International Airport (News and Observer 2010), and Tulsa (Oklahoma) International Airport (Stewart 2011a). reduced Energy use Reducing energy use was another primary reason for install- ing LED lights instead of incandescent airfield lighting sys- tems. Similar expectations are found in the literature about LED airfield lighting (Airports Council International 2007; Rainey 2007; Nowak 2011). The U.S. General Accounting Office (U.S. GAO 2010) lists LED airfield lighting as one of four common energy conservation devices at airports. Reduced energy use is stated as a justification for installation of LED taxiway lights at Stewart International Airport (States News Service 2009a; Targeted News Service 2010) where LEDs were expected to use only 25% to 33% of the energy of incandescent lights. Burlington International Airport (Edel- stein 2009; States News Service 2009b), Little Rock National Airport (States News Service 2009c), and Trenton–Mercer Airport (TendersInfo 2010a) also expected to realize energy reductions with LED taxiway lighting. San Bernardino Interna- tional Airport was replacing taxiway and runway lighting with LEDs in part because LEDs are purported to use only a frac- tion of the energy used by incandescent lighting (TendersInfo 2010b). Montreal–Pierre Elliott Trudeau International Airport expected its LED taxiway and runway lighting to use one-third chapter three InStaLLatIon ISSuES

11 of the energy used by incandescent lights (Canadian Cor- porate Newswire 2008a). LED runway centerline lighting at Prince George Airport (British Columbia) is expected to use less energy than older lighting (Nielsen 2008). Improved Visibility As stated earlier, a majority of survey respondents noted that improved visibility of airfield lighting was one of the reasons for their decision to install LED airfield lighting. In general this is borne out by observations of the rapid onset and offset times of flashing LED signal lights (Rainey 2007), which is expected to improve conspicuity for runway guard lights (RGLs). Bullough et al. (2007) reported that blue, green, and white LEDs appear brighter than incandescent sources hav- ing the same luminous intensity, largely because of increased color saturation, but that this effect is reduced when view- ing lights in foggy atmospheres because the fog scatters light from the ambient environment that reduces the apparent saturation of light. The saturated color of green LED sources can also assist pilots in identification of the colors of signal lights (Skinner and Bullough 2011). Both color-normal and color-deficient pilots could sometimes identify a green incandescent signal light incorrectly as white, because of the relatively desatu- rated appearance of the green incandescent signal. Such mis- identification did not occur when a green LED signal light was used. Many white LED sources have a “bluer” appearance than unfiltered incandescent lamps. Because incandescent lamps appear “yellower” when they are dimmed, such as on lower intensity steps for airfield lighting, they can sometimes be misidentified as yellow lights. LEDs undergo very little color shift when dimmed, and this can improve correct identifica- tion of the light as white by pilots (Bierman et al. 2009). Although not mentioned by the survey respondents, the relatively rapid onset and offset times of LED sources com- pared with incandescent lamps can be advantageous in terms of conspicuity. The rapid flashing of LEDs, unlike the more gradual increase and decrease in light output of an incandes- cent source, can result in shorter response times to a flashing light (Sivak et al. 1994; Bullough et al. 2002). Radetsky et al. (2009) and Skinner and Greenfield (2011) reported that RGLs using LED sources could have lower luminous inten- sities than incandescent RGLs while still having the same conspicuity and visibility, largely because the faster onset and offset times resulted in a more effective warning signal. EaSE of InStaLLatIon Compared with conventional (mainly incandescent) airfield lighting, the majority of respondents (16 of 22) to the sur- vey questionnaire (Appendix B) indicated that installation of LED lighting systems was easy, and five respondents indi- cated that effort was moderate. None of the survey respon- dents indicated that LED airfield lighting installation was dif- ficult. When asked about unanticipated costs (Question C4 in Appendix B), survey respondents mentioned a few items that suggested that certain issues sometimes arose. These focused on components within the electrical regulation and control systems, such as requiring circuit board modifications for LED fixtures to ensure compatibility with thyristor-type constant-current regulators (CCRs), or the decision to replace isolation transformers to account for the lower electrical load of LED fixtures. In a separate survey question (Question C8 in Appen- dix B), participants were asked whether the installation of LED airfield fixtures required any special tools, equipment, staffing, or training. Most respondents (16 of 22) indicated that no special equipment or training was needed. One respondent noted that airport electrical staff participated in a training course provided by the LED system supplier and another stated that airfield technicians needed to be trained on the operation of the new system. One respondent stated that connections to the communications and control equip- ment were performed by the manufacturer observed by air- port personnel. The results of the survey questionnaire regarding the ease of installation of LED airfield lighting fixtures were largely consistent with the published literature on this topic (News and Observer 2010; Stewart 2011a), which reported no evi- dence that LED airfield lighting systems were any more dif- ficult to install than conventional incandescent systems. compatIbILIty conSIDEratIonS Issues related to the compatibility of LED airfield lighting systems with existing electrical regulator and control equip- ment were also explicitly addressed in the survey question- naire (Questions C5 and C6). Overall, survey respondents reported few widespread problems with compatibility. Most respondents (19 of 22) reported that their LED systems were compatible with the existing infrastructure, and 17 stated spe- cifically that LED fixtures were compatible with the regula- tor, control, and monitoring equipment. Only a few reported issues related to how well the LED fixtures worked with silicon controlled rectifier (SCR) regulators. One respondent stated that ferroresonant regulators were eventually installed to improve compatibility with their LED fixtures, and one respondent stated that the airport had to adjust some regula- tors to correct issues with flicker. Some compatibility issues are mentioned in the literature on LED airfield lighting. It is stated by Hough and Gilbreath (2010) that RGLs using LEDs can be used with thyristor or

12 ferroresonant CCRs. Gallagher (2008) pointed out that early LED taxiway edge lights did not appear to dim appreciably when operated on lower intensity steps. In response to these early dimming issues, the FAA in its version “C” revision to EB No. 67, “Light Sources Other than Incandescent and Xenon for Airport and Obstruction Lighting Fixtures,” defined a dimming curve to ensure that LED intensity would behave similarly to incandescent systems when operated at different currents (see Appendix D). To maximize compatibility, a number of airports replaced some electrical regulation or control components in the instal- lation of their LED lighting systems. Springdale Municipal Airport replaced their taxiway lights with LEDs, and simulta- neously installed lower power isolation transformers (Hough and Gilbreath 2010). When replacing more than 800 airfield lights with LEDs, Will Rogers World Airport (Oklahoma City, Oklahoma) replaced 45 W isolation transformers with 10 and 15 W transformers (Hough and Gilbreath 2010). Runyon and Chapman (2009) point out that LED air- field lighting systems can be designed to be compatible with SCR regulators as well as ferroresonant high crest factor regulators, but not all systems may be optimized for such compatibility. Confirming compatibility with the electrical system components that an airport plans to use is important before LED lighting systems are purchased. InStaLLatIon pErSonnEL Survey participants were asked (Question C7) who performed the installation of LED light fixtures at their airports. The majority of respondents (18 of 22) indicated that a contrac- tor installed the LEDs. Nearly half (ten of 22) reported that electrical staff at the airport participated in the installation, either alone or in conjunction with a contractor. As noted in a previous section of this chapter (“Ease of Installation”), no respondents indicated that the manufacturer or vendor performed the installation; however, one respondent pointed out that the manufacturer led the connection of control and communications equipment to the LED airfield lighting system.