Filament-Free Future

New lighting technology for general aviation

June 5, 2002 By Peter A. Bedell

If you do much flying at night, you probably have been stymied by a burned-out position (navigation) light or smoked landing light. Sure, the airplane still flies without a functioning position light but, technically, you will be thumbing your nose at the regulations. Or, if you run off the end of a dark runway with a defunct landing light, whom do you think the FAA will hit with a "careless and reckless" violation?

Thanks to technology that's been around for years but has only recently reached general aviation, the burned-out-bulb blues may become a rarity. Light-emitting diodes (LEDs) are being certified for use as replacement position lights in general aviation airplanes. In addition, landing lights that use halogen and xenon technology continue to find their way into more light aircraft. The xenon and LED lights promise bulb life measured in thousands of hours, making bulb replacement an event to occur once every generation. In addition, LED and xenon lights deliver more candlepower while simultaneously drawing less current from the airplane's electrical system.

LEDs

Whelen Engineering, of Chester, Connecticut, is the leading manufacturer of lighting products for road-bound emergency vehicles. If you get a close look at a police cruiser (and we hope it's not often) you'll see that Whelen likely manufactured its light bar and/or siren assembly. Tucked away in the corner of the manufacturing floor is the relatively tiny general aviation side of Whelen's business. There, employees create and repair lighting equipment for all general aviation aircraft — new and old — from taildraggers to jets. Several years ago, Whelen pioneered what is called CometFlash, the strobe systems that emit four quick flashes upon every firing of the strobe. You'll see these on all new and replacement Whelen strobe systems and, perhaps, in your rear view mirror if you get pulled over.

The latest entrants to the world of new-technology exterior lighting are the LED position lights offered by Whelen. LED lights are showing up everywhere these days. We see them used in buses, truck trailers, traffic signals, and any other place where regular incandescent lights take a beating. Many of you have likely purchased an LED flashlight by now. LEDs have shown a lifespan of as much as 100,000 hours. They also draw one-quarter the current of standard incandescent or halogen lamps, which reduces the workload on your airplane's electrical system. Finally, the LED lights have no filament to break. The bane of incandescent light bulbs in light airplanes has been short bulb life because of vibration that breaks the fragile filament. That's why landing lights mounted in the engine cowl have a shorter lifespan when compared to those mounted on the wing.

Realizing that the majority of GA sales are likely to be made in the aftermarket, Whelen is making LED position lights available to replace existing position light assemblies in aircraft with 14- or 28-volt electrical systems. The brains of the products are located within the light assembly itself, which means you won't need to mount a remote power supply anywhere in the airframe. Just clip the old lights off, splice in the new lights, and you're done. TSO approval for the red and green wingtip LED position light assemblies is expected by late summer. The aft-facing white LED position light (part number 70805) has TSO approval and lists for $565, although, like most of Whelen's products, it could be found for less at one of the company's distributors. It's a little pricey until you consider that position light bulbs last only about 25 operational hours and can retail for as much as $40 each. Of course there's also the peace of mind that comes from not being technically grounded by a burned-out position light bulb.

Xenon HID lamps

Most modern luxury cars use xenon light technology for headlights. Even if you haven't had any firsthand experience with these so-called high-intensity discharge (HID) lights, you've probably seen them coming at you on the highway. They cast a brilliant, bluish-white light precisely aimed ahead of the vehicle to illuminate the road without blinding the eyes of oncoming drivers. In addition to superior brightness, and therefore visibility, these light systems offer extremely long bulb life and low current draw.

An unlikely company latched on to this technology to bring HIDs to general aviation. Known more for its line of airframe speed modifications, LoPresti Speed Merchants, of Vero Beach, Florida, introduced its Boom Beam HID landing light system for light aircraft with 14- and 28-volt systems (see " Pilot Products: LoPresti Boom Beam," February 2001 Pilot. HID lights use xenon and mercury gases to create and maintain the light source. Applying 30,000 volts of current to two electrodes within a glass tube ignites the gases to create the light. Think of it as a steady-burning strobe. Once ignited, the light can be maintained on as little as nine volts. Since there is no filament, LoPresti warranties the system, including the bulb, for five years.

So far the Boom Beam has been installed in hundreds of individual aircraft and in fleets of airplanes at Embry-Riddle Aeronautical University, FlightSafety International, and ATP flight schools. Airplanes at these institutions fly hundreds of hours every month and make short work of standard incandescent bulbs. In the long run, the switch to the LoPresti HID bulbs will save these schools money by reducing aircraft downtime. Systems start at around $700.

LoPresti claims that the Boom Beam is two and one-half times brighter than a conventional 250-watt landing light. The company offers the Boom Beam with three reflectors ranging from spot to flood light. If you only have one landing light, the flood reflector provides a wider field of light compared to the narrow beam of the focused reflector. HID lights also run cool, so you need not worry about melting or deforming the plastic lenses that cover some landing lights. The HID light allows you to display a landing light at all times for maximum visibility day or night without worrying about saving your bulb for night operations.

HID lights only draw a fraction of the amps that the standard incandescent bulbs do. Flip the switch on the typical 250-watt landing light system and the ammeter or load meter jumps to life as the alternator struggles to power them. The Boom Beam uses less than half the power while simultaneously providing more light.

Currently the system can be installed on certain Mooneys and Beech Bonanzas under a supplemental type certificate. Other airframe installations require a field approval.

Halogen systems

Halogen headlamps have been in cars for years. Their durability and brightness are far superior to standard incandescent bulbs that were used in automobiles prior to the mid-1980s. Like incandescent bulbs, halogen lamps use a filament, but it is mounted inside a quartz bulb and surrounded by halogen gas. The gas works as a light amplifier making halogens much brighter than standard bulbs for the same wattage.

In addition to being brighter, the halogens last about 10 times longer than standard incandescent lights. Whelen and General Electric produce halogen lamps that are direct replacements for existing landing and taxi lights in most GA airplanes. For example, to obtain the halogen version of the GE 4509 light bulb for a Cessna 172, you simply order a Q4509. Although you will pay about two to three times as much for the halogen bulb, you'll enjoy longer bulb life and more candlepower without the requirement of an STC or modification to your airplane.

The future of lighting for GA aircraft promises long bulb life, low power draw, and better pilot visibility and conspicuity. In addition, the possibility of being grounded by a burned-out bulb will be all but eliminated.

Peter A. Bedell, AOPA 1136339, is a captain for a regional airline and is a former technical editor of AOPA Pilot.

What is required and what to buy?

To fly at night, an airplane must have approved anticollision and position lighting systems. (Airplanes certified prior to 1957 can legally get away with only position lights.) Position (or navigation) lights are steady-burning lights that allow you to quickly ascertain whether another airplane is coming, going, or crossing your path. The red and green wingtip position lights shine forward and out to the side while a white light covers your rear. Since steady-burning lights of only 40 watts or so don't draw much attention, anticollision lights are a must for anyone who does any measurable amount of night flight.

Anticollision lights are typically strobe lights with clear (white) lenses. White strobes are the brightest anticollision lights and therefore draw the most attention. On the downside, these lights are often annoying to you when flying in the clouds and to other pilots if used on the ground in close proximity to others.

Flashing beacons, such as those mounted on the vertical fin of most Cessna singles, or rotating/oscillating beacons are primarily used for ground recognition purposes. Strobes also can be used as a beacon, but it's recommended that you use a red lens to tone down the brightness so the light is not distracting to other pilots on the ground.

Advantages to a flashing beacon or strobe unit are longer bulb life and no moving parts, unlike the old-technology rotating beacons that use expensive electric motors and lots of moving parts to create a flashing effect. Replacing the old rotator with a flasher or a strobe is likely the most cost-effective solution.

Strobe users aren't immune to their lights wearing out. Over the years, strobe tubes become clouded with carbon particles, reducing their effective candlepower. Periodic replacement of the strobe tube is necessary to keep the lights bright. — PAB

Lights bring awareness to pilots at large airports

During flight training, little if any mention is made to students about what aircraft lights should be used under what circumstances. Professional pilots, however, are trained that standardized usage of certain lights can increase situational awareness, especially on the ground at large airports.

Airlines have specific guidelines that pilots follow to make sure that the airplane — as well as the company logo — is seen. More important, this standardized usage of exterior lighting allows ramp personnel, fellow aircrews, as well as controllers in the tower to visually ascertain your intentions in the sea of lights on a large airfield. Airline techniques are also considerate to the night vision of fellow pilots and ground personnel. To better illustrate this technique we'll follow an airline crew from the gate to takeoff.

Whenever the aircraft is powered up, the position (navigation) lights are illuminated. If the airplane is equipped with tail floodlights (sometimes called logo lights since they illuminate the company logo on the tail), they should be on as well. Prior to engine start, the red beacon lights (usually on the top and bottom of the fuselage or atop the vertical stabilizer) are turned on to alert the ground crew and other pilots that the airplane is ready to move out of the gate either under its own power or that of a tug. In addition, when the crew calls ground control for a taxi clearance, the ramp or ground controller can quickly distinguish the airplane from the many others since it will be the one with the beacons flashing.

Once out of the gate area and out of eyeshot of the marshaller, the captain will illuminate the taxi light so he can see where he's going. When not in motion, many airline crews turn the taxi light off to make it easy to ascertain whether an aircraft is moving or not. With the heightened awareness regarding runway/taxiway incursions, it's reassuring to see the taxi light of a jumbo extinguished when you cross its path. It's also nice not to be flooded with hundreds of watts of GE's finest as you slink by.

Only when cleared onto the runway are strobe lights added to the array. When multiple airplanes are holding in the number-one position on multiple taxiways, it's easy to determine who has been given clearance onto the runway — the airplane with the taxi and strobe lights on. And with position-and-hold clearances still the norm at large airports, it's good to have bright, obnoxious strobe lights to cover your rear while sitting on an active runway. Finally, when cleared for takeoff, every exterior light (landing, recognition, and even ice-detection lights) is turned on for maximum visibility for the crew and all those around the airplane.

Because of varying degrees of lighting equipment in general aviation aircraft, these procedures may not be followed to the letter. For example, many GA airplanes don't even have a beacon light. Under such circumstances, it may be prudent to use your strobes for ground recognition. At a large airport, you may be flying the littlest fish in a sea of whales. When in doubt, use your judgment. The main goal is to see and be seen. — PAB