Avionics News February 2016 - 69

AN INSTANTLY REALIZED BENEFIT,
AND TOP APPEAL OF AN LED LIGHT,
IS ITS LOW POWER DRAW.

among the most cost-effective, budget-challenging
upgrades an owner can make. Up front, the costs are
going to be higher than sticking with the old, original
light sources.
Some owners may look at the costs as out of line for
the benefits; knowledgeable operators often make the
choice after recognizing the long-term advantages of
these special little diodes. But compared to the various
incandescent and high-capacitance discharge options,
LEDs today deliver gains on multiple levels. Once
completed, the changeover should never again happen.
Lifespan. It's the biggest gain owners receive when
new-generation LEDs replace old-technology lighting.
As quoted by numerous LED vendors and suppliers,
most of what aircraft owners install should outlast the
airframes in which they fly.
The LED: It works quite differently ...
longer, cooler, lower and more
The original successful light-bulb design works about
the same today, albeit better: Current directed through
a medium causes gas or a solid conductor to glow;
straight incandescent lights - resister-type bulbs - glow
with heat the current generates because of the filament's
resistance. Florescent lights use a gas conductor in a tube
that glows when current flows.
LEDs? Well, a light-emitting diode is more like a
transistor than a conventional light bulb. Basically, the LED
is a two-lead semiconductor, a p-n junction diode. Apply
a suitable voltage to the two leads and electrons are able
to recombine with electron holes within the device. That
recombination releases energy in the form of photons - light.
Ordinary incandescent bulbs emit light across a broad
spectrum, much of which humans can't see; they also
waste a huge percentage of the energy they use in the
form of heat.
LEDs lack the filament that glows in incandescent

bulbs, so they don't become particularly hot. Similarly,
since there's no filament glowing white hot, LED lifespans
exceed incandescent bulbs by thousands of hours.
Best of all for power-challenged electrical systems,
LEDs consume a fraction of the energy needed by
aircraft bulbs - in recognition lights, landing and taxi
lights, even strobe-quality anti-collision lights.
As long expected, they've become more available
and prices have dropped. And their range of rolls has
expanded, covering the aircraft landscape inside and out.
Power to the panel
An instantly realized benefit, and top appeal of an
LED light, is its low power draw.
That old 100-watt landing light used on most 14-volt
aircraft draws 8.33 amps at 12 volts. Some aircraft employ
two of those 100-watt incandescent bulbs; some pilots opt
for halogen bulbs of lower power but equal illumination,
and they still draw more than 4 amps - each.
But a typical current draw for a 14-volt-system replacement
landing light draws down around 1.2 to 1.4 amps.
For aircraft with two landing lights - as found in
many Bonanzas and Comanches - the draw of two LED
landing lights is less than half of what a single quartzhalogen bulb draws and about one quarter of what two
standard 100-watt incandescent bulbs draw.
For an aircraft owner considering going all glass, first
going all LED could save juice enough to spare the owner
an alternator upgrade to meet the needs of that digital panel.
Shakin' won't break 'em
The major threat to filament-driven bulbs in aircraft
is twofold - the heat of the filament and the vibration it
endures. The combination helps assure the steady turnover
in standard landing-light and recognition-light bulbs.
Continued on following page
avionics news

february

2016

Table of Contents for the Digital Edition of Avionics News February 2016