The transition to light emitting diode (LED) lighting technology on aircraft is nearly complete, at least for new platforms. While some cost and technology issues remain, the advanced lighting systems can now be used almost everywhere from cockpit displays to landing lights to mood lighting in the cabins. The technology is providing an efficiency boost and aesthetic improvement, especially in the cabins of new and increasingly existing aircraft.
From a big picture perspective, “we see an almost universal adoption of LED lighting,” said Jim Kramer, senior vice president of Astronics. The East Aurora, N.Y-based company, offering exterior and interior aircraft lighting through its subsidiary Astronics Luminescent Systems Inc., (LSI), has recently been working with business jet OEMs, including Hawker Beechcraft, to come up with supplemental type certificates (STC) that allow them to offer LED landing and taxi lights to their customers. It is a technology that is suitable for aerospace lighting and airframe manufacturers and their major systems suppliers are looking to LEDs to “help reduce lifecycle costs … (and) weight all of the classic things you want to do when developing a new airframe,” he said.
The move to LEDs has been especially dramatic in new aircraft. In clean sheet designs, “we see an almost insignificant number of applications that are considering a technology other than LED,” Kramer said. An exception to the rule might be where an OEM is not doing a complete clean sheet design but the next-generation of an aircraft model that has a cockpit with a lot of incandescent lighting and a dimming control system in place, he said. In that case, “they may make a decision not to do a wholesale change that would require a lot of certification updates.”
In the aftermarket, vendors are reporting a boost in business spurred on by technology improvements and market demand especially for cabin upgrades. “LEDs are now available in miniature sizes with greatly increased power output and range of color … opening (up) many possibilities for lighting solutions not previously possible in the aircraft interior,” said Beth de Young, vice president and general manager at IDD Aerospace. The extensive use of the technology in the cabins of new aircraft, such as the Boeing 787 and the Next Generation 737-800, has helped spur greater interest in the technology.
“In addition, the response to the new aircraft LED lit interiors, such as the Boeing Sky Interior, operators are increasingly looking to retrofit to maintain consistency across its single- and now twin-aisle aircraft,” said Stephen Scover, vice president and general manager of the lighting division of B/E Aerospace, of Wellington, Fla.
There are, however, lingering cost and technology issues. There are the upfront costs; LED products themselves can cost more than older technologies they are replacing, so the benefits from adopting the technology are gained more from a product lifecycle than recurring standpoint, Kramer said.
Many of the technology issues are isolated but still can be significant. “If you are talking about exterior lighting, for example, there is a significant opportunity for retrofitting what were legacy filament base lights with solid-state or LED lights,” said Kramer. “The big reason for that is the existing fixtures are typically powered by a 28 Volt DC, sometimes AC, but a fixed voltage source and dimming are not significant issues; (therefore), it is relatively straightforward to use the same power inputs for your LEDs as your traditional incandescent fixtures.” However, there may be cases where the older incandescent lights are not mounted in areas that provide sufficient thermal control, he said. “LEDs get very hot, and you need ways to keep them cool.”
On flight deck, “dimming is critical … (and) having all of the devices in your cockpit dim consistently can be a challenge; in addition, when traditional incandescent lighting dims the color changes slightly,” and these changes have to be accounted for “when you’re putting LED components in the cockpit,” said Kramer.
“There are ways to address all these (issues),” Kramer said. For example, “we find that the airframe manufacturers who have the most success are those who recognize that having an integrated consistent dimming scheme between all of the suppliers of lighted products in the cockpit is critical.” However, sometimes costs will end up outweighing the benefits, Kramer said. For example, it would take much longer for a military fighter jet that may see up to 500 flight hours year to reap the reliability advantages from upgrading to LED than an Airbus A330B logging 4,000 hours for American Airlines, he said. “When we worked as subcontractor on the F-16 Night Vision Goggle Upgrade for the U.S. Air Force, they decided to keep it all incandescent.”
However, generally the argument for LED lighting is strong and getting stronger as the technology improves. In the cockpit, LED is being used to backlight LCD displays and control panels and the illuminate switches.
“We are incorporating of LED backlight technology … in the large format displays we have introduced in the air transport, business and regional markets,” said Matt Carrico, senior engineering manager, advanced concepts for Rockwell Collins. With LED, “the displays … are not life limited anymore by the lamp, so … if you design them right you can even sustain loss of a couple of the LEDs themselves and still not have to pull the display because there’s still plenty of brightness left,” he said. “A close second in terms of their benefits is the reduction of power,” he said, noting the LEDs help reduce the in the heat generated in forward glare shield and forward panel areas.
An added attraction has been the steady improvements in the LEDs. The rate of LED development is “almost on the same Moore’s Law Curve as the rest of the semiconductor industry, so every couple of years you can count on the light power doubling,” said Carrico. This translates into the need to use fewer LEDs. The company also has been able to reduce the thickness of its displays “since LEDs themselves are thinner” than the former technologies, a major plus considering that “space is always at a premium on the flight decks,” said Carrico. Rockwell is looking at whether “LED can be used as a component,” in its head-up dipslays (HUD). It already used on its HGS-3500 Compact Unit for light to mid-size business jets systems. That system, unlike traditional HUDs, “does not require overhead projector” and uses LEDs to help “generate an image with sufficient brightness (and) … manageable heat, so we don’t make it uncomfortable for the pilot.”
When it comes to the cabin, Boeing reports “more than 90 percent” of (its) backlog of more than 2,800 Next-Generation 737-800s will be delivered with the LED-lit Boeing Sky Interiors (BSI). The company delivered 500th 737 with Boeing Sky Interior late last year and continues to deliver the aircraft at a rate of about one a day, said Scover.
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“We are very pleased with the market acceptance of the BSI because certainly at the initial stages of (the program) customers did have an option … to stick with traditional type of product or … convert to the BSI,” and they nearly unanimously selected BSI.
In addition, both Boeing and B/E Aerospace “are extremely pleased with the with the rollout of product … so overall we’re looking to get … (BSI) onto more aircraft as time goes on,” Scover said. “This is clearly something to build on, and I believe we’re seeing the signs of that right now,” in the increasingly active retrofit market. “I think people who are receiving LED systems in their initial aircraft deliveries, predominantly BSI,” are looking to maintain some type of fleet identity that would include a common look throughout the aircraft both single- and twin-aisle platforms, he said. In fact, it has only been in the last year that LED manufacturers have been provided technology capable of “generating sufficient light for the twin aisle type of cabins,” he said.
“The main challenges now are the variety of configurations with aircraft” to be addressed, said Scover. Meeting the required light, weight or power levels are no longer difficult issues, he said. “I think the technical challenges have pretty much peeled away or become within our grasp; the challenge now is really getting on the aircraft and giving the customer a quick turnaround in terms of downtime, and … doing it rapidly and making due with least parts as possible,” he said.
B/E will be not alone in this growing market; in fact, IDD Aerospace last year joined up launching its interior product line, Zevan. “The demand is shifting from maintenance driven replacement of older technology incandescent, halogen or fluorescent to LED lighting becoming instrumental for the airlines’ cabin interior branding upgrade strategies,” said de Young. There is a “shift to full cabin retrofits including the complete array of cabin lighting from a single lighting integrator (who) replaces various component parts throughout the aircraft from a variety of niche suppliers,” de Young said.
Still to be announced, the company’s “North American launch customer is installing a full range of LED ‘plug and play’ replacement lights — nose to tail interior upgrade of the cabin interior lighting under a single STC,” de Young said. “Included in the LED lighting upgrade are ceiling and sidewall lights (wash lights), reading lights and PSU signs, lavatory lights, galley lights and various monument signs,” she said. “The lights for this installation are compatible with the 737 and 757, and by reusing the aircraft’s existing wiring and current Flight Attendant Panel the time required and cost of installation for the upgrade are greatly reduced.”
There are many initiatives underway exploring the ways in which the technology can be used to improve the aircraft environment including a European study by Osram, Bergische Universität Wuppertal, the Fraunhofer Institute for Building Physics, Airbus and Diehl Aerospace showed that “chronobiologically adapted lighting based on LED, particularly on long-distance, overnight flights, leads to a medically measurable improvement in sleep, enhances well-being and promotes higher alertness upon arrival.”
“We feel that there’s still room for maturity and … technology improvements of a relatively significant sort from the LED manufacturers,” said Kramer. “In the near-term we see continued developments both in the efficiency and thermal capacity … of LED products.”
However, the continuing improvement and changes in the technology does pose an issue related to obsolescence. For the incandescent-based lighting fixtures, “the light bulb you could buy … in 1959 was still available in 1999, so even though it wasn’t as reliable and thermally efficient as you’d like, when it failed it was pretty straight forward how to fix it,” Kramer said. “On the other hand, one of the challenges of LED lighting is that as it is becoming more efficient and in more effective packages … the LED die packages … that companies like ours designed into fixtures eight or nine years ago aren’t available anymore,” but the airplanes are still being flown will need those parts for many years, he said. This situation can be become quite problematic “if you don’t (or didn’t) have a real good plan in place to on a readily consistent basis upgrade (and certify) the LED technology in your existing product.”
While it is an issue, “it is kind of a good problem,” said Carrico. If you are developing a new system that might take two or three years to complete, “you kind of have to design (it to be) as upgradable as possible so you can you take advantage downstream of future improvements to the LEDs themselves.”
Meanwhile, the industry continues to study the potential of organic LEDs (OLEDS). “It is still early on, but … we think there’s a lot of potential for that technology in a variety of applications, and we’re making sure that we stay on top of that,” said Kramer. It has the potential for use, for example, as “what you could call programmable signage in cabin.”
“We certainly see the advantages of the OLEDs especially in allowing (for) … thinness in the displays,” said Carrico. When they are brand new, they seem to have a nice brightness and ‘good enough’ I’ll say resolution; at the moment, the real issue with them is the aging characteristics,” he said. “They still are not meeting the specifications that industry needs for use on the flight deck: partly it’s an issue of the entire display getting dimmer, but it is also the different colors age at different rates, so color stability over time is something that is difficult to maintain.”
Other technologies that may not be quite ready for primetime when it comes to boosting aircraft lighting systems but worthy of keeping your eye on are remote phosphor, electroluminescence and fiber optics, said Scover.
Next month: Databus and Connector Technologies
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 firstname.lastname@example.org.
The following are some new contracts and technology developments from developers of aircraft lighting systems.
Ã¢âÂ¶ The Naval Air Systems Command (Navair) at Patuxent River, Md., has developed a dimmable LED bulb that, it says, has the potential to improve products in the aircraft and automotive industries. Designed and patented by Naval Air Warfare Center Aircraft Division engineer David Kayser over the past three years, the Variable Intensity LED Illumination System bulb can last more than 40,000 hours, Navair said. The Aircraft Division partnered with the Defense Logistics Agency to create the bulb for backlighting cockpit panels in naval aircraft, but found it has broader applications for other industries, such as auto, mining and construction. “We still have a huge number of legacy aircraft that use the common mini bulb,” Kayser said. “All the backlighting and mastery cautionary panels are all backlit with the 327 lamp.” Kayser’s LED allows pilots to adjust the panel lighting without a dimmer circuit. It duplicates the same dimming pattern as the incandescent, allowing more flexibility in the amount of light to the panel Controlling the amount of light results in better visibility within the cockpit. The LED lens was tailored for night vision, resulting in panel lighting that can be dimmed for either day or night flights.
Ã¢âÂ¶ STG Aerospace in 2012 completed the first five aircraft installations of its WhiteHawk replacement LED lighting system as part of a major order from Swiss International Air Lines. The LED lighting system will be retrofitted across the airline’s 20-strong Avro RJ100 fleet, replacing existing fluorescent tubes.
Ã¢âÂ¶ Heads Up Technologies, based in Carrollton, Texas, added RGB and Variable White LED lighting systems to its family of cabin lighting products. “Our new RGB and Variable White LED lighting systems allow designers to create sophisticated lighting effects that actually use less cabin space,” said Rob Harshaw, president and CEO of Heads Up Technologies. “Custom sizes and shapes of lighting elements offers sophisticated options for the interior lighting design.” The RGB and Variable White LED lights communicate with the cabin management system via RS-485 data bus protocols. The onboard intelligence provides a greater degree of control over real time color control and dimming, creating noticeably better responsiveness than previous designs.
Ã¢âÂ¶ Astronics wholly owned subsidiary, Luminescent Systems Inc. has been selected by Embraer Defense and Security as a supplier for its KC-390 military transport and tanker program. Astronics will provide a complete exterior lighting system, including navigation, anti-collision, landing, taxi, aerial refueling and formation lights. The system will feature Astronics’ LED technology to provide enhanced optical performance, high reliability and reduced power consumption. The KC-390 is expected to enter service in 2016.
ADB Airfield Solutions www.adb-airfield.com
Aerospace Optics www.vivisun.com
Astronics Corp. www.astronics.com
AvtechTyee Corp. www.avtcorp.com
B/E Aerospace www.beaerospace.com
Bruce Aerospace Inc. www.bruceind.com
Carmanah Technologies Corp. www.carmanah.com
Dallas Avionics, Inc. www.dallasavionics.com
Day-Ray Products, Inc. www.day-ray.com
DeVore Aviation Corp. of America www.devoreaviation.com
Diehl Aerospace www.diehl-aerospace.de
Ducommun Technologies www.ducommun.com
Eaton Aerospace www.eaton.com
Electro-Mech Components, Inc. www.electromechcomp.com
Endicott Research Group www.ergpower.com
Esterline Control Systems www.esterline.com
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
Page Aerospace www.pageaerospace.co.uk
Panelight Components Group, LLC www.panelightcomponents.com
Precise Flight, Inc. www.preciseflight.com
Rockwell Collins www.rockwellcollins.com
Sirio Panel S.p.A www.siriopanel.it
STG Aerospace www.stgaerospace.com
Talon Aerospace www.talonaerospace.com
UTC Aerospace Systems http://utcaerospacesystems.com