Avionics News February 2016 - 70
Continued from page 69
But the LED is a solid-state semiconductor - a form of
transistor, in truth - and is far more resistant to vibration
and, as an added bonus, moisture.
Absent the energy waste that makes filaments hot,
and the combination yields a light source likely to last
thousands of hours - even tens of thousands of hours.
Whether in wingtip recognition- or position-light
fixtures, cowl- or wing-mounted landing light, or a landinggear-mounted taxi light, nothing can move inside the
individual LED. The outcome: Lights likely to outlast the
airframes carrying them and multiple owners downstream.
An aviation LED for every need
Landing and taxi lights stand among the earliest
attempts at giving LEDs options to general aviation
aircraft owners; the results were uneven and
disappointed some. But they did show early adopters
the big difference in alternator load - it dropped
significantly. Early qualitative problems quickly yielded
to products that deliver on their promises of long life.
All these points were enough to keep LEDs in a pilot's
mind - and to attract later adopters to the improved
products available today.
And improved they have, with output levels meeting
or exceeding the performance of the older-technology
units they replace. Consider the range of options.
Landing and taxi lights
Among the most-frequently changed bulbs of our
aviation history, the landing light should stand out as one
new owners quickly learn to do for themselves. Given
the short lifespan of the bulbs standard in aircraft for
decades, some operators opt to make the change solely
for the huge gain in life expectancy of the replacement
LED "bulb" assemblies.
A huge variety in illuminating power, the number of
LED elements and prices give pilots across the spectrum
options for replacing their once-standard units.
What's to gain? Over straight incandescent, only
dozens of bulb changes skipped due to the higher
durability and longer lifespan of the LED units.
Those changes not made means less shop time and
fewer instances of invading the fixture to swap out an
expended bulb, fewer opportunities to do damage - and
fewer dollars, ultimately, spent on replacement bulbs.
Options exist for virtually every fixture using standard off70
the-shelf landing and taxi bulbs. Other options replace the
entire fixture with a new one integrating the LED elements,
reflector, lens and the electronics to fire up the LEDs.
Some owners will debate the cost effectiveness, what
with standard bulbs running less than $20 and the leastexpensive LED options running upward of $200. Prices
go up with the aircraft type and installation.
But most owners and personal experience teach us that
conventional incandescent landing light bulbs - and to a
similar extent, taxi light bulbs - typically last less than 25
hours; even quartz halogen options, which last about twice
as long, fall multiple replacements short of that LED option.
Take a common PAR64 bulb - a Q4559 incandescent
and Q4559X halogen version. Used in many commercial,
business and military applications, the bulb boasts a 100hour life expectancy. The most-commonly used version
draws huge power - it's a 600-watt bulb - while providing
performance that quickly degrades with use. At 30 hours
into its life, its light output is down about 50 percent.
But a recently approved replacement LED version boasts
a 50,000-hour life expectancy - and it puts one-tenth the
load on the electrical system, drawing a mere 60 watts.
Take into account the time needed to replace an expired
landing light - even for the pilot who enjoys performing the
owner-allowed maintenance - those interruptions add up.
A decade after installing it, that LED unit should still
be working, while the incandescent and quartz-halogen
bulbs have been replaced multiple times.
When did a landing or tax light ever burn out while
the pilot was still at home field?
One often overlooked advantage of LED units over
their predecessors is the quality of light they produce.
Incandescent bulbs produce a light more yellow in color,
while quartz-halogen bulbs produce a whiter light.
The best of the LED replacements for landing and taxi
lights produce a far whiter, almost blue light that not only is
easier to see but also more stable over the life of the bulb.
Position and recognition lights ...
avoiding things that go bump in the sky
Owners should know they can now find options for
replacement LED fixtures designed to replace bulbs in
both position and recognition lights - or they can replace
the entire fixture with a unit that does everything.
Yes, position, recognition and anti-collision strobe
functions are available in sets for most aircraft installations.
Within these individual combination fixtures are green
or red LEDs for the position lights, rear-facing white
LEDs for recognition lights, and arrays of super-bright,