Aircraft Lighting

Getting the right flight light

It was nighttime and, according to reports, the Cessna 441 Conquest II was cleared to hold on Runway 31 at Lambert-St. Louis International Airport. Instead, the pilot taxied into position to hold on the parallel runway 30R at an intersection about 2,000 feet down the runway. Meanwhile, a McDonnell-Douglas MD-80 was cleared to take off on Runway 30R. As the airliner reached about 90 knots, the pilot saw the Conquest and attempted to swerve left to miss it. He didn't. The right wing of the MD-80 sliced off the top half of the 441's fuselage longitudinally at the windows, killing both pilots.

According to a National Transportation Safety Board accident report, the 441's taxi light switch was in the On position, while the position (navigation), anti-collision, and rotating beacon light switches were found in the Off position. This left the airplane virtually undetectable from the side and rear. It would have been hard for the tower, and nearly impossible for the pilot of the MD-80, to see the Conquest in time to take evasive action.

Obviously, more mistakes were made than simply forgetting to turn on the lights. But had the Cessna pilots turned on the strobes and position lights, the MD-80 pilots would have had a white light and two strobes to alert them that somebody was where he shouldn't be.

Lights are a cheap defense. For such a simple system, they display lots of information to other pilots — such as position, direction of flight, and even intentions. Today, lighting systems on general aviation aircraft are exponentially better than they used to be.

New GA aircraft now offer more lights, as well as fancy multiple- flash strobes, to greatly enhance visibilities, day or night. There is also an increase in the use of recognition lights that are spaced far apart on the wingtips to give the airplane a larger appearance than just a single nose-mounted landing light would. Basically, a recognition light is a lower-powered landing light, generally drawing less than 50 watts. The lower power requirements allow the pilot to burn them for long times without straining the electrical system the way conventional landing lights do. Make them pulse alternately from side to side with an aftermarket system, and the GA aircraft becomes as stealthy as Las Vegas on a clear night.

A pulsing system attracts attention and cuts power usage by alternating each light's intensity. Precise Flight's Pulselite system can work from one light in a Cessna 150 to multiple landing, taxi, or recognition lights on a Gulfstream IV. It works like a dimmer switch in your home. The lights don't actually turn off but just dim to a low intensity — about 30 percent of the bulbs' capability. If used in a two- light system, the Pulselite essentially burns only one light at any given time. Since the $200 system gradually increases and decreases power to the bulbs, the bulbs can last up to 10 times longer than those on a standard switch, said Precise Flight's Mike Demith.

General aviation airplanes have traditionally been poorly lit — most offer only position lights, a rotating beacon, and maybe a landing light. Even some big twins have no landing or taxi light visible unless the gear is down, because they are both located on the nose gear strut. In addition, many airplanes have no rotating beacon high up on the vertical stabilizer to alert others on crowded ramps.

Whelen Engineering Company of Chester, Connecticut, hopes to change general aviation's lack of brightness. Whelen is now the sole supplier of lighting systems to Piper Aircraft. For the Piper Archer III, Whelen supplies a combination light assembly that is installed in each wingtip. The assembly consists of the appropriate left or right (red or green) position light, a strobe light, and a rear-facing position light that gives the Archer III and other new Pipers the required coverage without having to mount a position light on the tail.

"That light assembly appeared in 1976 or 1977 and has become a real popular unit for homebuilts," said Fred Frazier, Whelen's vice president of aviation products. It saves the owner or builder from routing wires back to the tail and eliminates hassle and weight. Because of the canard's lack of tail installation points, the unit was also used on the Beech Starship and other Rutan designs.

According to Federal Aviation Regulations, besides the red, green, and white position lights, at least one anti-collision light is required for night flight under current certification requirements. Basically, the light must be either aviation red or aviation white and can be in the form of a rotating, flashing, or oscillating beacon or a strobe. The anti- collision light cannot be mounted so as to "impair the flight crewmembers' vision or detract from the conspicuity of the position lights...." The anti-collision light must also cover a field of view 75 degrees above and below the aircraft's horizontal axis.

Whelen's newest anti-collision light system, dubbed CometFlash, was introduced more than a year ago: If you see a strobe quickly flash four times, it's a CometFlash. Ordinary strobes flash only once or twice in the same time the CometFlash fires four times.

The CometFlash emits an initial burst of light (20 joules) followed by three smaller flashes (eight joules each), explained Frazier. The old double strobes emitted an initial burst (25 joules) followed by a small (two joules) flash. More light in the same amount of time means more visibility, said Frazier.

By press time, every new strobe that Whelen sells for GA airplanes should be of the CometFlash variety. The HR model beacon/strobe fits in most holes where a rotating beacon used to fit. With about 3,000 units a year being sold, the HR is Whelen's most popular light. It lists for $360 but can be had for less through Whelen's distributors.

Despite being traditionally a low-maintenance item, strobe lights require periodic replacement of the flashtubes. Every time a strobe fires, metal from the electrodes vaporizes and leaves tiny carbon particles on the inside of the xenon-gas strobe tube. Over time, these turn the tube brown and reduce the light's brightness. For this reason, a new regulation requires airlines to periodically replace or test the brightness of strobes installed on their aircraft. For less-regulated fliers, Whelen's Frazier recommends replacing strobes every 1,000 to 1,500 hours of light use.

Note that landing lights are not required equipment for night flight under FAR Part 91. On a well-lit runway, perhaps, you can get away without a landing light. But for emergency landings, taxiing on unfamiliar ramps, or landing on poorly lit runways, the landing light makes a huge difference.

Many single-engine aircraft have landing or taxi lights mounted in the cowl which, in some cases, is a poor place to mount them. The high vibration in the cowl area does its best to rattle the filaments in a bulb, limiting life. Mounting the lights out on the wings, far from the source of vibration, can extend the life of a bulb exponentially.

The bulb's wattage affects its life expectancy nearly as much as where the bulb is located. A more powerful bulb requires a thicker filament, thus making it harder to break and, in theory, increasing its life. But be careful not to put a 250 watt bulb into a system that can handle only 150. Circuit breakers may pop, wires could melt, or the switches might weld themselves in the On position. Plus, if the bulb does work, it probably will not produce its rated brightness.

Inevitably, as the airplane fleet ages, lighting assemblies will need periodic replacement. Your options lie in replacing the original unit, overhauling it, or replacing it with an approved aftermarket replacement. Recently, the owners of a 1968 Beech Baron discovered it would cost $1,500 to replace the original Grimes rotating beacon that was located atop the vertical stabilizer. With no luck getting the light repaired in a reasonable amount of time, the owners replaced it with a red HR strobe from Whelen that cost less than $200.

Grimes is the lighting original equipment manufacturer for Beech and Cessna, but mainly provides units for the military and airlines. When asked about the steep price, a Grimes spokesman admitted their ignorance of GA but promised Grimes would become more competitive within the general aviation market in both new product sales and service of existing products.

The advantages of the Whelen strobe unit as installed in the Baron are low cost and virtually no maintenance, but the light's visibility and appearance after its installation left a lot to be desired. Nighttime visibility was adequate, but the red lens made it more or less invisible during the day. As for appearance, in this application, the bowl that the unit fit into was not deep enough and allowed the strobe's red lens to tower about six inches above the tail.

On the other hand, the original-equipment Grimes rotating beacon was clearly visible during the day and even better at night. It's a nice- looking unit that appears to belong there.

But although it's slick-looking and bright, the original Grimes unit and similar oscillating or rotating beacons can cause problems. These units have electric motors turning gears and other linkages that will eventually wear out and, of course, the light bulbs themselves will need occasional replacement.

If you're after low cost and forget-about-it maintenance, the strobe or flasher-type beacon is the right choice. If high visibility and appearance are important, try having your original equipment light replaced or overhauled.

The Baron owners finally contacted Aero Electric in Wichita and got the original Grimes beacon rebuilt for $170. What happened to the Whelen strobe? The red lens was replaced with a white one and installed as a belly strobe. With the white lens, the Whelen unit is almost blinding.

Whelen's current version of the HR strobe is offered with a new red or white lens and would fit the holes in many popular airplane types. The red lens that was so ineffective and unattractive on the Baron is now shorter, better-looking, and more transparent, greatly improving the strobe's brightness.

If a strobe or rotating beacon is not what you want, consider a flasher unit similar to those often found on Cessna singles. Their operation is similar to the turn signal system in a car; they employ a relay to interrupt the power flow to the bulb. Flashers will burn out too, but less readily than a standard light bulb because of their gentle pulsing rather than the "all or nothing" operation of a standard light.

Thanks to DeVore Aviation, tail lights are no longer limited to cars. The company's Tel-Tail floods are used on anything from Cessnas to Boeings. The system uses floodlights mounted in the horizontal stabilizer or rear fuselage that project their beams onto the vertical stabilizer and rudder. This system is especially handy for ground operations at busy airports. Airlines like tail floods because they show off company logos, while smaller airplanes generally desire the safety advantages. Tel-Tail lights range in price from $1,000 for a typical single-engine installation to $2,000 for larger multiengine piston airplanes.

Cessna, Piper, Beech, and even Merlin owners and operators who are considering replacement of their wingtips should check out RMD Aircraft Lighting's integrated wingtip landing lights. These units replace the existing wingtips with new ones that have integrated landing or taxi lights.

If you own an aircraft with a relatively poor lighting system, consider a lighting overhaul. If there is no easy or cost-effective way of replacing your existing lights, consider supplementing them with a pair of wingtip recognition or landing lights or possibly tail floodlights. Day or night, it is better to be seen than not.

Who to call when the lights go out:

Aero Electric, 3414 West 29 Street South, Wichita, Kansas 67217; 316/943- 6100.

DeVore Aviation Corporation, 6401-B Jefferson N.E., Albuquerque, New Mexico 87109; 505/345-8713.

Grimes Aerospace Company, 240 Twain Avenue, Urbana, Ohio 43078; 513/653- 5225.

Precise Flight, Post Office Box 7168, Bend, Oregon 97708; 800/547-2558.

RMD Aircraft Lighting, Incorporated, 3648 S.E. Roanoke Court, Hillsboro, Oregon 97123; 503/681-0685.

Whelen Engineering Company, Route 145, Winthrop Road, Chester, Connecticut 06412; 203/526-9504.