Saab2000 From Switzerland, joined Jun 2001, 1148 posts, RR: 7 Posted (4 months 1 week 4 days 17 hours ago) and read 2295 times:
I don't know if this topic has been discussed much. But it seems like it is worthy of talk. LED lighting for exterior and interior lights seems as if it would cut by an order of magnitude the amount of electricity needed to power a large part of an airplane. This lower amount of electricity would put less strain on generators, lower fire risk, etc. LEDs are far more reliable, cooler, lighter and seem to have few drawbacks.
What are the major manufacturers doing WRT to LED lighting?
Avioniker From United States, joined Dec 2001, 1093 posts, RR: 9 Reply 1, posted (4 months 1 week 4 days 16 hours ago) and read 2297 times:
It's being used extensively for indicator and warning lights on all planes. It's going into a number of Biz and regional jets for interior and wash lighting.
As far as exterior lighing the directional nature of LED's is a problem but, like white LED's, I'm sure it'll be overcome.
One may educate the ignorance from the unknowing but stupid is forever. Boswell; Date unknown.
Saab2000 From Switzerland, joined Jun 2001, 1148 posts, RR: 7 Reply 2, posted (4 months 1 week 4 days 16 hours ago) and read 2299 times:
It's just stupid little stuff. I fly a CRJ-200 and the chart holder lights are tiny, tiny incandescent bulbs. Very often burned out or they flicker, etc. Crap. I have heard that LEDs can't really be dimmed and that might be a problem. But it seems like there's got to be a better solution than the lame incandescents. My Maglight LED flashlight shows that.
DALMD88 From United States, joined Jul 2000, 1676 posts, RR: 7 Reply 3, posted (4 months 1 week 4 days 15 hours ago) and read 2268 times:
Over time a lot of the indicator lights and the pax reading lights will all be LED. DL has switched out the pax reading lights on the MD88 and the 757 door slide arm lights are the first indicator lights I've seen. I doubt the cockpit indicator lights will be retofited. There isn't a big reason to spend the money on a retrofit. I think the reason for changing the slide lights is the delay driver. When one is out the plane is a no go. It is always found just as the plane is ready to push. Sure it is usually just a quick bulb change, but do to the timing of the find it is always a delay. A cockpit indicator bulb is usually found earlier in preflight and can be changed without taking a delay.
KELPkid From United States, joined Nov 2005, 3418 posts, RR: 3 Reply 5, posted (4 months 1 week 4 days 15 hours ago) and read 2263 times:
Anyone know what voltage the LEDs used for things like reading lights, etc. operate at?
One of the challeneges to extensive LED lighting usage is low voltage DC networks, which have high I^2R (I squared R) losses...I guess for now, the existing AC busses are used with the appropriate circuits in place on the LED for proper power conversion.
LEDs, as are diodes in general, most definitely DC devices (although zener diodes are used for rectification, the conversion of AC to DC).
Rulebooks and regulations are made from paper...and they do a poor job at preventing metal from contacting rock-Ernest G
Sprout5199 From United States, joined Feb 2005, 1427 posts, RR: 11 Reply 6, posted (4 months 1 week 4 days 15 hours ago) and read 2257 times:
Quoting KELPkid (Reply 5): LEDs, as are diodes in general, most definitely DC devices (although zener diodes are used for rectification, the conversion of AC to DC).
They normally use DC but you "can" run one on AC. And zener diodes are for voltage limiting and such. most diodes used for rectification are general purpose diodes unless you need a high speed diode for the higher freqs. as in a RF probe.
Quoting PlaneWasted (Reply 4): Not true. The best way to do it is with pulse width modulation, a little more complex than other dimming techniques but very efficient.
Very true, and when you use a multi color diode(red/bue/green) you can get some neat colors.
RoseFlyer From United States, joined Feb 2004, 5230 posts, RR: 17 Reply 7, posted (4 months 1 week 4 days 15 hours ago) and read 2249 times:
Quoting DALMD88 (Reply 3): doubt the cockpit indicator lights will be retofited. There isn't a big reason to spend the money on a retrofit.
Maybe not retrofitted, but we'll likely see flight deck indication systems go to LED.
Quoting Saab2000 (Thread starter): This lower amount of electricity would put less strain on generators, lower fire risk, etc. LEDs are far more reliable, cooler, lighter and seem to have few drawbacks.
The temperature aspect is a huge driver in the flight deck for making a change. A lot of cooling is needed in the flight deck. Going to more LED lights would reduce that requirement and thus allow less flow of air and save a few pounds. LEDs put out a fraction of the heat as bulbs do.
The maintenance aspect is also highly desirable. We'll see it happen.
I design airplane parts for a living and am that guy that mechanics hate and blame for everything... the Design Engineer
PlaneWasted From Sweden, joined Jan 2008, 245 posts, RR: 0 Reply 8, posted (4 months 1 week 4 days 14 hours ago) and read 2240 times:
Quoting KELPkid (Reply 5): Anyone know what voltage the LEDs used for things like reading lights, etc. operate at?
One of the challeneges to extensive LED lighting usage is low voltage DC networks, which have high I^2R (I squared R) losses...I guess for now, the existing AC busses are used with the appropriate circuits in place on the LED for proper power conversion.
LEDs, as are diodes in general, most definitely DC devices (although zener diodes are used for rectification, the conversion of AC to DC).
They run on 2-5 Volts. But you can connect them i series without any problems. Switching up and down voltages is also becoming cheaper and cheaper every day.
Litz From United States, joined Dec 2003, 1422 posts, RR: 0 Reply 9, posted (4 months 1 week 4 days 13 hours ago) and read 2196 times:
Don't forget, for existing systems you can often just plug a 'compatible' led bulb module in place of an existing light bulb ... let's say it's a bayonet base 14vdc lamp; you put the appropriate LED replacement in, and you're done.
The module is already configured to run off 14vdc (it does the voltage dropping for the LED elements internally) and because it's designed as a plug-in replacement, it fits into the same space, too.
You'll see this in a lot of places ... airplanes, trains, cars, etc.
Heck, there are even replacement LED elements for the lamps in pinball machines.
DALMD88 From United States, joined Jul 2000, 1676 posts, RR: 7 Reply 10, posted (4 months 1 week 4 days 12 hours ago) and read 2177 times:
Quoting Litz (Reply 9): Don't forget, for existing systems you can often just plug a 'compatible' led bulb module in place of an existing light bulb ... let's say it's a bayonet base 14vdc lamp; you put the appropriate LED replacement in, and you're done.
This is exactly what we did on the 757 door slide indicators.
Bond007 From United States, joined Mar 2005, 4276 posts, RR: 6 Reply 11, posted (4 months 1 week 4 days 12 hours ago) and read 2177 times:
Quoting Litz (Reply 9): The module is already configured to run off 14vdc (it does the voltage dropping for the LED elements internally) and because it's designed as a plug-in replacement, it fits into the same space, too.
Correct. Since LEDs are generally much smaller than the comparable incandescent fixture, the voltage regulation can be built in - to a certain extent anyway.
I can see a time in the not too distant future, where the majority of all lighting will be LED based.
Jimbo
I'd rather be on the ground wishing I was in the air, than in the air wishing I was on the ground!
KELPkid From United States, joined Nov 2005, 3418 posts, RR: 3 Reply 12, posted (4 months 1 week 4 days 11 hours ago) and read 2168 times:
Quoting PlaneWasted (Reply 8): Switching up and down voltages is also becoming cheaper and cheaper every day.
But how effecient is the process?
Traditionally, changing DC voltages entailed lots of effeciency loss in the circuits that did the voltage change...you used resistors to go down and switching circuits to go up, and the heat would flow from these circuits
Rulebooks and regulations are made from paper...and they do a poor job at preventing metal from contacting rock-Ernest G
RoseFlyer From United States, joined Feb 2004, 5230 posts, RR: 17 Reply 13, posted (4 months 1 week 4 days 11 hours ago) and read 2163 times:
Quoting Litz (Reply 9): Don't forget, for existing systems you can often just plug a 'compatible' led bulb module in place of an existing light bulb ... let's say it's a bayonet base 14vdc lamp; you put the appropriate LED replacement in, and you're done.
You can't do that in the flight deck. Certification requirements won't allow you to just switch them. The new ones have to be qualified. At least that's what I think.
I design airplane parts for a living and am that guy that mechanics hate and blame for everything... the Design Engineer
PlaneWasted From Sweden, joined Jan 2008, 245 posts, RR: 0 Reply 14, posted (4 months 1 week 4 days 10 hours ago) and read 2139 times:
Quoting KELPkid (Reply 12): But how effecient is the process?
Traditionally, changing DC voltages entailed lots of effeciency loss in the circuits that did the voltage change...you used resistors to go down and switching circuits to go up, and the heat would flow from these circuits
We used 48 V to 3.3 V converters in a project i worked in before. We got 100 A from two regulators, and I think the heat from the converters was around 10-20 W. That gives an efficiency of 93-97%.
NoWorries From United States, joined Oct 2006, 206 posts, RR: 0 Reply 15, posted (4 months 1 week 4 days 10 hours ago) and read 2110 times:
LED's aren't linear devices (linear relationship between current and voltage) -- they have a fixed forward voltage drop (determined by the material needed to make a particular color). Their intensity varies with current. So, in a typical LED lighting system, once you account for the fixed voltage drop, the amount of current that flows depends on the total voltage applied divided b the total resistance of the circuit. Most cheap systems just wire up an LED to a fixed voltage source that is close to it's forward drop -- usually shortens the life of the LED considerably. Also, like all semiconductors, their internal resistance drops as they heat up -- leading to greater current and potential damage. A good LED system will use some sort of electronic ballast to regulate the current flow.
The cost of ballasting an individual LED as a replacement lamp will tend to be higher than using a single ballast to regulate an entire string of LEDs -- though with IC costs being so low these days it isn't all that expensive to incorporate some sort of current regulator in an individual LED package.
Nomadd22 From United States, joined Feb 2008, 286 posts, RR: 0 Reply 16, posted (4 months 1 week 4 days 9 hours ago) and read 2096 times:
Quoting KELPkid (Reply 5): LEDs, as are diodes in general, most definitely DC devices (although zener diodes are used for rectification, the conversion of AC to DC).
Quoting KELPkid (Reply 12): But how effecient is the process?
Traditionally, changing DC voltages entailed lots of effeciency loss in the circuits that did the voltage change...you used resistors to go down and switching circuits to go up, and the heat would flow from these circuits hot
Zener diodes aren't used for rectification. They're for regulation.
Good Dc to Dc converters have been over 95% efficient and very cheap when bought in bulk for many years now. Adjustable current supplies that run off as high a voltage as you want, used for controlling LED output are also efficient and cheap.
Rwessel From United States, joined Jan 2007, 564 posts, RR: 0 Reply 17, posted (4 months 1 week 4 days 3 hours ago) and read 2051 times:
Quoting KELPkid (Reply 12): But how effecient is the process?
Traditionally, changing DC voltages entailed lots of effeciency loss in the circuits that did the voltage change...you used resistors to go down and switching circuits to go up, and the heat would flow from these circuits
Basically all DC-DC converters are little switching power supplies in a can. The use quite high switching frequencies, so the magnetics are very small. These go both up and down in voltage, and many provide regulation, isolation, and a wide range of input voltages. Many are nominally 1:1, and are used for regulation and isolation rather than actually changing the voltage. For example, you can get a 20W dual output (+/-5V) converter with an input range of 15-75V (48V nominal), with 1% output regulation, 65mV ripple, 86% efficiency, and with substantial voltage, resistive and capacitative isolation between the input and output. Typical switching frequencies in the range of 400KHz. If you can live with a 36-75V input range, and a single +5V output, you can get 89% efficiency and better regulation.
The smaller DC-DC converters (quarter watt) are typically in the 80% efficient range, while the bigger parts (100W range) commonly run at 97-98% for a fair range of input voltages). Now you can generally get better specs for more money, and in some cases, you can get devices with narrow input ranges with better efficiency.
Edit: and if you're just driving LEDs, you basically don't care about regulation, ripple, or a bunch of other stuff, and you can simplify the converter and improve its efficiency.
Even so, this is a huge win over incandescents. For example, a 20W tungsten incandescent will be about 1-1.5% efficient. IOW, 1.5% of the energy going into the bulb comes out as light, the rest comes out as (direct) heat (in the end, even the light ends up as heat, but spread over the surfaces it's lighting). Bigger tungsten's get to about 2.5%.
Compare that to an equivalent white LED, which will likely be 9-10% efficient, even if you knock that down with a 85% efficient DC-DC converter, you still reduce your total power from 20W to about 4W, and reduce the net heat output by the same factor of five. Now small quartz halogens do a little better (a bit over 3%), but still rather worse than LEDs.
Good fluorescents still do better for area lighting than LEDs, however, but it's not a huge advantage. OTOH, fluorescents are big and fragile, and can't really have their output adjusted.
I realize that this is not aircraft lighting, but it shows what can be done by switching from incandescent to LED. The E3 LED has a MTBF of 100,000 hours. The halogen E6 bulbs have to be changed every 100 hours or so. It's really inconvenient when they blow out on a dark road, that's for sure!
Firings, if well done, are good for employee morale.
T prop From United States, joined Apr 2001, 804 posts, RR: 1 Reply 19, posted (4 months 1 week 3 days 22 hours ago) and read 1954 times:
I posted this in the thread about flashlights for mx.
Quoting T prop (Reply 122): The next gen Q400's and the CRJ 1000 use LED lighting in the cabin and LED nav lights are what the A380 comes with from the factory. LED nav lights are also STC'd for Airbus narrow bodies. Incandescents are fast becoming yesterdays technology.
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