Aircraft LED Lights
Several manufacturers are selling LED position and landing lights (including LED strobes too), these are very reliable with a long service life, probably longer than the aircraft. Current draw is much less resulting in thinner cables and there is a weight savings too because the high voltage unit is no longer necessary.
LEDs are semiconductors, basically a diode and with a small forward current flow it emits visible light in a different range of colors. Their potential is enormous as a replacement for the incandescent light bulb from the past.
We are going to take a look at this revolutionary semiconductor as a source of light in aircraft and around the house too where energy can be saved and enjoyed.
Light, Aviation & LEDs
Light is just a stream of photons originating from one point and it has a certain amount of power too (lasers are good example of this). And as such we can describe some properties of light.
Lumens & candela
The power emitted in a particular direction (as is done in aircraft) is called candela (luminous intensity). For example: one candle will emit one candela of light. Lumen (luminous flux) is the power of light perceived by the human eye and the relation with candela can be defined by: 1 lm = cd.sr. Or: one candela in all directions (our candle) equals 4π lumens.
Sometimes the term lux is used. Lux (area of luminous flux) is the amount of lumens per m2 or 1 lx = 1 lm/m2, useful for indoor lighting.
Aviation light requirements
For an aviation strobe light (white or red) we need 400 cd (candela) 360° around the aircraft vertical axes and 30° above and below the horizontal plane (some 2000 lm). The navigation lights are a 25 watts incandescent lightbulb producing some 15 lm/W, thus 375 lm in total per bulb. This can be done with 5 watt LEDs from Lumileds producing 18 - 22 lm/W.
You can see that we need high power LEDs to be able to produce this amount of light. As you can expect these are expensive, although by using GaN (Gallium Nitride) LEDs on a six inch Si (Silicon) waver, production cost is much lower. Which should result in lower prices in the end.
LED schematic symbol
LED Symbol and Connections
A LED is basically a diode, so in schematics you will see the symbol to the right. The current flows from the anode to the cathode. Forward voltage drop varies between 1,7 V to 4,4 V, depending on the color. Aviation uses normally red, green and white LEDs. For the interior other colors, blue, are used too.
LEDs are fed by a small voltage and constant current. So connecting them to the aircraft bus without any form of regulation would burn them out almost immediately. They are usually connected in series with a resistor (string) or in parallel strings of series switched LEDs for redundancy. The high power types also need proper cooling if they are to last a long time.
Whelen has a number of LED assemblies in their program. For experimental aircraft the MicroBurst™ Series Lighting is of interest, they also have full range or LED lighting for certified aircraft.
But if you are totally into designer aircraft lights then take a look at the Galatica and Aurora series LEDs from Aveo Engineering. They are a beauty for the eye and a must have for your aircraft. Below some examples:
Compared to others Aveo lights have the lowest drag of all external lights. This might be an important factor for you, plus they look great!