The use of light emitting diode (LED) technology on commercial and business aircraft is becoming more the norm than the exception. LEDs can be used to illuminate everything from airline logos on the tail to switches on the flight deck. The technology is being built or retrofitted into aircraft to improve appearance and boost energy efficiency. While technology and market issues remain, LED lighting is expected to supplant much, if not all, current technology on aircraft over the next few years.
“The pace of LED (technology) migration into aircraft is... accelerating for both the OEM as well as aftermarket,” said Andre Hessling, manager of advanced product development, lighting systems at Goodrich Interiors. “There is hardly any consideration of conventional lights anymore.” Goodrich makes a range of lighting systems using LED technology, including cabin wash lighting and passenger lighting.
The benefits of LEDs are well known, including weight savings, lower maintenance costs, ruggedness and increased system reliability. But now, the technology is further evolving, thanks to advancements in other industries, including automotive and consumer lighting systems, allowing for more applications of LED lighting solutions in aviation.
“Home lighting is the Holy Grail for LED manufacturers (and) while it is still in its infancy,” it is gaining momentum, said Rob Harshaw, president and CEO of Heads Up Technologies, of Carrolton, Texas. Developments in these markets will drive not only technology improvements but also customer expectations for this type of lighting, said Harshaw.
“It is slowly but surely encroaching everywhere,” said Bruce Maxwell, president of Luma Technologies, of Bellevue, Wash. “It used to be (thought) they would never be bright enough for outside lights.” But now LEDs are available for all exterior lights, including high-powered flood lights and landing light systems.
This use of the technology will continue to grow over the next several years as airlines and regional carriers look for ways to save on maintenance costs and weight, while providing an aesthetically appealing interior for their passengers, said Scott Sweet, interior lighting product manager at Emteq, of New Berlin, Wis.
The technology continues to improve as LEDs are being developed “to ever higher performance levels in terms of flux per bucks,” lumens per emitter and light output (flux) per watt, but the rate is declining, showing that LEDs are reaching a first level of maturity,” said Hessling. “Also, the light quality the homogeneity of emitted spectrum –– of white LEDs is improving.”
“Because we are seeing more (efficacious) light being emitted from the LEDs, we can package them differently” than earlier LED systems, which were mainly just “a straight line of light,” said Stephen Scover, vice president and general manager of the lighting division of B/E Aerospace, Wellington, Fla. “There are places that you can now put light or use lighting effects that you couldn’t in the past.”
B/E Aerospace is using these innovations to provide LED lighting for the new “Sky Interior” on Next Generation Boeing 737s. “The system is somewhat revolutionary,” said Scover. “It is a seamless type of product: You basically walk on the aircraft and experience lighting as opposed to (encountering) a bunch of lights staring at you from different or odd angles.”
The company has worked closely with Boeing to develop the interior design.
“We just didn’t come in at the back end of the program; we worked with some of the bin structures and on where light would be placed,” Scover said. “I think what that indicates is that there is an industry acceptance now that a LED system is the way to go.”
On the flight deck, thanks to the quality of the lighting its light, color and contrast “things are not quite so fuzzy anymore; they are nice and crisp and clear,” which translates to greater situational awareness and enhanced safety, said Maxwell. Last year, Luma Technologies introduced the LT-4500 Series Integrated LED Display System for King Air and Beechcraft 1900D aircraft. The system is designed to be a one-for-one, drop-in replacement for existing incandescent units, with immediate plug-and-play functionality.
With increases in power density and improvements in optical efficiency, “LED applications on the exterior that were more difficult to do before are really now becoming more realistic if they are designed properly,” said Vera Fosnot, Honeywell senior manager of product marketing for lighting.
The transition to LED began with lower-power products, such as position lights, but is now progressing toward the higher-power products, like landing light systems, she said. Currently, the greatest demand is for LED replacements for those lights with poor reliability, high cost or high impact of repair as well as “lights that are dispatch critical for the operators, such as navigation lights,” Fosnot said.
However, “all of the lights on the exterior can now be LED, if they are designed and integrated properly,” and Honeywell is developing a full suite of exterior LED applications that will be applicable on many different platforms, she said.
The exterior lighting market includes large and smaller niche companies offering LED products for a variety of aircraft types. For example, Goodrich touts its introduction last year of a product line of supplemental type certification certified exterior lights for the Airbus A320 series. Hessling said the line of runway turn-off lights, taxi lights and logo lights offers a return on investment within a year or less.
Emteq offers a variety of exterior LEDs including the combined tail position and anti-collision lights for the Bombardier CRJ. Designed to replace current halogen and xenon products, the LED products include an integrated power supply, eliminating the need for an existing external power supply, said Sweet.
Heads Up Technologies has developed and qualified high intensity LED exterior lights for the Cessna Citation Jet series including the landing lights, wing inspection lights, tail flood lights and overwing exit lights, said Harshaw. He said the landing light outperforms the incandescent source it replaced and provides “huge weight savings.” Heads Up also provides the LED cabin lighting for the Beechcraft King Air 350i.
Emteq is capitalizing on technology improvements, such as better color control and greater intensity, developed in other industries, said Sweet. “It has opened up the possibility for significant innovation with our most recent examples being the Daylight Variable White Wash lighting product and exterior landing lights.” The Daylight system offers a variable white LED lighting system capable of outputting multiple shades of white light and is controlled through a control management system.
However, this surge in demand has its downside. LED has “gone ballistic in every market and anytime anything goes ballistic there goes source of supply (and) consistency,” said Maxwell. It is also a challenge for component developers, like Luma, to keep up with the changing technology. “It’s a good problem, but still a challenge,” he said.
For all the advancements, challenges of LEDs, including heat management, color consistency and cost remain.
“Thermal management is really the key to the longevity of LEDs,” Fosnot said. It is critical to design the LEDs properly and seek “the full FAR compliance over their entire rated life.”
Companies use different approaches to handle the excess heat from the lights, including using plastic and metal heat sinks. From early on, “our products had metal or aluminum heat sinks (and) we have made something like 20 miles of LED lighting now and have had very few failures,” said Harshaw.
With more airplanes being made of composites, LED systems have to be carefully designed “to withstand HERF (high-energy radio-frequency) and lightning induced transience,” said Maxwell. “LEDs are very delicate things. They have all these great benefits, but they have to be nurtured and packaged.”
“The physical integration remains a challenge for our general cabin lighting (indirect wash) from time to time,” said Sweet. “We still have to be careful in ensuring the angles and orientation of the light is just right.”
Electrical integration, specifically control, can be a challenge, he said.
In addition, color consistency of the LEDs “is a huge problem,” said Harshaw. “Even on a single reel of 2,000 to 5,000 LEDs, there are subtle variations in all the lights.” This requires techniques to put them together, so the color variation can’t be seen.
On the flight deck, a key remaining challenge is getting human factors and industrial design groups to craft a definition of “what light colors are required in terms of cool work-lights and warm‚ ambient lights,” Hessling said.
Dimming groups of lights also might pose a few challenges, since the differences between the current-driven LED and easier-to-dim voltage controlled filament lights must be accounted for, he said.
Cost is also a key issue, especially when it comes to retrofitting. “Airlines have really been watching their discretionary funds. When you think of a retrofit for lighting that certainly would be discretionary,” said Fosnot.
The cost of the technology and implementation is coming down. “However, as the technology improves costs may rise,” advised Hessling.
The business case can differ from application to application. For example, “incandescent lights that fail often and are annoying to replace, like reading lights, allow for a fairly easily justifiable business case,” Hessling said. On the other hand, replacing sophisticated halogen reading lights with very different electronic characteristics than LEDs may not be so easy to justify.
Companies generally concede technology changes in the near future will be more evolutionary than revolutionary, at least for aircraft applications. However, they are keeping an eye on the development of organic LEDs.
“We have been a bit disappointed by the slow progress in this area,” said Hessling. “There are some (first) applications in sight for the business jet clients now, which we will integrate in our VIP product line-up, where performance and lifetime is less of an issue and experience is the key attribute.”
Next month: Synthetic Vision Systems
Avionics Magazine’s Product Focus is a monthly feature that examines some of the latest trends in different market segments of the avionics industry. It does not represent a comprehensive survey of all companies and products in these markets. Avionics Product Focus Editor Ed McKenna can be contacted at [email protected]
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Aerospace Optics www.vivisun.com
Airtechnics, Inc. www.airtechnics.com
Astronics Corp. www.astronics.com
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Carmanah Technologies Corp. www.carmanah.com
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Heads Up Technologies www.heads-up.com
IDD Aerospace www.iddaerospacecorp.com
Interface Displays & Controls www.interfacedisplays.com
Luma Technologies www.lumatech.com
Northrop Grumman www.northropgrumman.com
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Panelight Components Group, LLC www.panelightcomponents.com
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STG Aerospace www.stgaerospace.com
Talon Aerospace www.talonaerospace.com