What could be more basic than cockpit illumination? Simple white light bulbs for map reading and other flightdeck chores. For years incandescents have dominated the cockpit, while cabins began to change. But now this last bastion of the older technology is beginning to give way to longer-lasting solid state, light-emitting diodes (LEDs).
Cockpit lighting is a niche market: it requires numerous illuminators in very small quantities. Still a customer can spend $5,000 to $15,000 or more to place light where it is needed, excluding displays, switches and annunciators. There are map and chart lights, table lights, utility, stowage and aisle lights. There are glareshield lights to floodlight the instrument panel, dome lights, floor lights, emergency lights and oxygen mask lights.
According to Goodrich Hella Aerospace Lighting Systems, a unit of the U.S. corporation based in Germany, three or four cockpit zones typically require illumination: the pilot’s lap, knees or table for map reading, the instrument panel area, the cockpit entrance, and the area where the maps are stowed.
UK-based Page Aerospace even offers optional, cockpit mood lighting. Tinted lighting in the cockpit could make the area look attractive to buyers. But experts also believe this type of illumination–which can be programmed to redden at dawn and dusk to simulate sunrise and sunset–can reduce pilot fatigue during long-haul flights. Carriers want mood lighting in their first-class cabins to enhance the passenger experience. Cabin mood lighting has been introduced on some international carriers and in some business jets.
Cockpit lights come in a range of shapes and sizes. High-brightness halogen or conventional incandescent reading lights can be installed in the cockpit ceiling. LEDs can be embedded in a chart holder attached to the pilot’s yoke. Small, glareshield-mounted LED or incandescent lights can illuminate the instrument panel.
Incandescent Lights
Incandescents represent about 90 percent of the cockpit lighting market across aviation sectors, says Benno Heissig, military segment leader-Europe, for Goodrich Hella. The company provides incandescent designs, including a fixed-base, cylindrical utility lamp that is adjustable in every axis. Employed on European combat aircraft such as the Tornado and Jaguar, the mil-spec, conformal unit can be detached from its base and carried up to 6.5 feet (2 meters) away or moved and reattached in prepositioned brackets. Goodrich thought the product would go out of production 10 years ago, Heissig says, but it still sells in volume.
Honeywell Lighting and Electronics also makes incandescent products, including a map light used in many military aircraft. Adjustable in intensity, the lamp is mounted on a flexible, gooseneck arm in the sidewall of the cockpit. It can be pulled out and moved to different positions.
Halogen
But incandescent lights don’t last that long. Halogen lamps, using a specialized type of incandescent technology, are replacing conventional bulbs in certain applications. Halogen technology allows tungsten to be redeposited on the lamp’s filament, extending its life. Heissig cites an external navigation light, the incandescent version of which lasts 300 hours, while the halogen version lasts 2,000 hours.
Of course a light’s life span depends on its circumstances and characteristics. Incandescent "microbulbs" used in cockpit panels theoretically could last 10,000 to 20,000 hours. But life expectancy on a wingtip pulling up to 22 Gs would be shorter.
Goodrich Hella’s 2LA 455 453-00 line of halogen flight crew reading lights provides 2,000 hours of life. The company has sold 10,000 of these units, which represents a lot of aircraft since there are only one or two per cockpit. The product features a simple, reliable optical dimmer and provides "rectangular light distribution with sharp border lines," Heissig says.
Fluorescent lights last longer than incandescents. Honeywell provides a glareshield-mounted, fluorescent light to illuminate instrument displays. This dimmable "thunderstorm" light helps the pilot to adjust his eyes to various conditions outside.
Light-Emitting Diodes
New aircraft and retrofits use LEDs in the cockpit to increase reliability and reduce life-cycle cost. These solid state parts consume less power and have no coiled filaments, which can weaken from vibration and temperature extremes. Their downside is obsolescence.
Goodrich’s 2LA 455 065-10, an LED glareshield light, for example, lasts long enough to be "scrapped with the aircraft," Heissig says. The narrow-spectrum, 6-LED packages generate a small floodlight for night instrument reading. The radiation is too high to be "night vision-compatible," but the product is considered "night vision-friendly." The ARJ21 Chinese regional jet will use Goodrich LED-based cockpit lights. Page Aerospace supplies cockpit lights to the Airbus A380.
But long life isn’t necessarily guaranteed. Proper heat management, among other things, is essential, Honeywell stresses. Designers also need to compensate for variation in LED performance, says Nico Machi, technical manager for Honeywell’s lighting business in Urbana, Ohio. LED makers sort parts into bins based on characteristics such as light intensity, forward voltage and color, but performance may vary up to 20 percent between the LEDs in a single bin.
Because these solid state, semiconductor devices are like a computer chip, they can be monitored via closed-loop systems more easily than analog light sources can. Users therefore can assess variations in output and color. If an operator needs to swap out a section of an LED light at some later time, he can compare the output of the new section with the output of the sections to the left and right of it. The replacement part can automatically compensate to make the lighting uniform.
Some suppliers, such as Emteq, offer only LED products. Emteq units are found in retrofits of Gulfstream IIIs and IVs, Falcon 50s and 900s, and Learjets, says Scott Sweet, product sales manager. The company provides fixed dome and gooseneck lights, among others. Its yoke-mounted, 8-LED lighted clipboard is being used on the Global Express. Emteq employs through-hole LEDs, which typically burn 20 percent brighter than surface-mount LEDs, says Sweet.
A key factor in extending LED life is controlling the temperature of the LED junction, the area of the semiconductor device that emits light. Honeywell has developed "smart circuits," which control the current running through the light-emitting diodes and monitor their cumulative operation, allowing the LEDs to degrade gracefully over time.
Use of fast-moving LED technology also risks product obsolescence. Engineers have to anticipate these changes as much as possible in their initial design. LEDs, for example, are getting brighter. Optics systems can be designed as modules to accommodate this trend and make upgrades easier as the technology progresses, says Scott Hamilton, Honeywell’s lighting engineering leader.
COMPANIES
Aerospace Optics www.vivisun.com
Astronics Corp. www.astronics.com
BAE Systems www.baesystems.com
B/E Aerospace www.beaerospace.com
Ducommun Technologies www.ductech.com
Emteq www.emteq.com
Gables Engineering www.gableseng.com
Goodrich Hella Aerospace www.goodrich-hella.com
Honeywell www.honeywell.com
IDD Aerospace www.iddaerospacecorp.com
Intertechnique www.intertechnique.fr
Koito Manufacturing Co. www.sp.koito.co.jp
Korry Electronics www.korry.com
Lamptronix www.lamptronix.thomasregister.com
Page Aerospace www.pageaerospace.co.uk
Smiths Aerospace www.smiths-aerospace.com
Spectra Lux www.spectralux.com
Staco Switch www.stacoswitch.com