# Experimental Aircraft Landing Light



## mn velocity pilot

Hi Team, 

Last fall I discovered that the incandescent landing light installed in the nose of my experimental Velocity aircraft had failed. I had two choices - I could either spend six bucks and buy a new one, or I could roll my own... well, winters are long here in Minnesota, and I needed something to do, so I went at it. 

I used three Cree CXA-1304 9.6V LEDs mounted on a heat sink and then mounted into the original incandescent bulb reflector on a heat sink. I'm driving these three LEDs with about 1.9 amps total (around 640ma/LED), which, according to the datasheet, should provide me around 2000 lumens total. The driver I designed is using a LM338 linear regulator for current limiting, and an IRF1501 mosfet controlled by a PIC controller to allow either a flashing or a steady-on mode. 

I've got two problems... I sure appreciate some help...

First... I think I've chosen the wrong LED, because I can't get the full 1.9 amp drive current on the 14V supply I've got available on the airplane. The problem appears to be that I don't have enough voltage margin to completely turn the mosfet on. Here's the simple math... 14V supply minus 9.6V turn on voltage for the LEDs leaves 4.4V that gets dropped across the LM338 regulator and the mosfet. The LM338 drops about 1.4V of that 4.4V... so the mosfet only sees about 3V... which isn't enough to completely turn it on...

So... I think I need a different LED - one with high efficency, high light output, and much lower voltage... Any suggestions?

Second problem - even when I fully drive the LEDs with 1.9A, the resulting brightness just isn't that great. I suspect the problem here is that the reflector I'm using (the old shell from the incandescent bulb) isn't working... or, perhaps, I need a lens? I can do the electronics, but I could sure use some help on the optics!

Here's a picture of the bulb I created:






Here's the plane it goes in:


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## TEEJ

mn velocity pilot said:


> Hi Team,
> 
> Last fall I discovered that the incandescent landing light installed in the nose of my experimental Velocity aircraft had failed.  I had two choices - I could either spend six bucks and buy a new one, or I could roll my own... well, winters are long here in Minnesota, and I needed something to do, so I went at it.
> 
> I used three Cree CXA-1304 9.6V LEDs mounted on a heat sink and then mounted into the original incandescent bulb reflector on a heat sink.  I'm driving these three LEDs with about 1.9 amps total (around 640ma/LED), which, according to the datasheet, should provide me around 2000 lumens total.  The driver I designed is using a LM338 linear regulator for current limiting, and an IRF1501 mosfet controlled by a PIC controller to allow either a flashing or a steady-on mode.
> 
> I've got two problems... I sure appreciate some help...
> 
> First... I think I've chosen the wrong LED, because I can't get the full 1.9 amp drive current on the 14V supply I've got available on the airplane.  The problem appears to be that I don't have enough voltage margin to completely turn the mosfet on.  Here's the simple math... 14V supply minus 9.6V turn on voltage for the LEDs leaves 4.4V that gets dropped across the LM338 regulator and the mosfet.  The LM338 drops about 1.4V of that 4.4V... so the mosfet only sees about 3V... which isn't enough to completely turn it on...
> 
> So... I think I need a different LED - one with high efficency, high light output, and much lower voltage... Any suggestions?
> 
> Second problem - even when I fully drive the LEDs with 1.9A, the resulting brightness just isn't that great.  I suspect the problem here is that the reflector I'm using (the old shell from the incandescent bulb) isn't working... or, perhaps, I need a lens?  I can do the electronics, but I could sure use some help on the optics!
> 
> Here's a picture of the bulb I created:
> 
> 
> 
> 
> 
> Here's the plane it goes in:



Your pics didn't post.  (Wrong format, too long an address?)

Are there FAA specs for the cd or lumens, etc, for  this type of light?

IE: Is an experimental aircraft held to the normal FAA specs for this sort of thing?

There are LED upgrades, but I don't know what you application is.  Places like:  hoffmanengineering.com/home1(dot)php have PAR64 type swaps with LED's for example.  

(dot) = .


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## idleprocess

TEEJ said:


> Your pics didn't post.  (Wrong format, too long an address?)



Looks like the OP tried to upload the image to CPF or encode it in text somehow - will need to use an image host.


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## mn velocity pilot

Hey, sorry, I hopefully now understand how to post images.  Here's the modified incandescent bulb:





And here's the airplane in the hangar:




If you look carefully at the bottom side of the nose of the aircraft, you can see the plexiglass cover for the landing light.

Any & all help will be greatly appreciated!

Dave


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## mn velocity pilot

Sorry, forgot to answer the other question from TEEJ.

For an experimental aircraft, there are no rules or requirements as to what I can use for a landing light.  I'm free to innovate.  Basically, brighter is better, and the rear end I save with a good landing light just might be my own.


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## idleprocess

I'm guessing that's some sort of light sport aircraft, but not familiar with the type.

I doubt you're going to get equivalent performance with that kind of arrangement - stuffing LED's into the salvaged reflector assembly roughly where the filament used to be.  You'll likely need to improvise new optics to get anything close to what the incandescent used to be ... or just spend that $6 and replace it with another like unit.


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## mn velocity pilot

It's actually a four place high performance bird... it's been lots of work but lots of fun.  

Part of the reason for rolling my own, outside of the enjoyment I get out of building, is that there is a potential safety advantage of having a strobing light in the front (in addition to the wingtip mounted strobes).  That's the main reason I set out on this path... 

I think idleprocess is correct, that I'm going to need to work on optics - a better reflector and a lens - in addition to choosing a different LED.  That's part of why I came to this forum... I'm the kind of person that enjoys a good challenge, which is why I built the airplane in the first place.  So... any good suggestions?  Again, my two key issues are:
- I need a different, low voltage (let's say 3-5V) LED ... what do folks suggest?
- I think I will need optics and a better reflector to make this work ... again, any suggestions?

THANKS!  I really appreciate any and all comments!

Dave


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## inetdog

Rather than change the LED or the battery voltage, you should use a different type of FET as the switching element. You should be able to get one with close to zero voltage drop and no need for a voltage higher than your +14V to drive it.

But the existing reflector was designed to work with a filament that is close to a point source and is at a very specific position relative to the reflector.
This is why your typical 3 LED light will have three individual reflectors taking up the space that would otherwise be one large reflector.
And the electronics need to be behind the reflector with only the LED mount sticking out in front of the hole in the reflector.


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## mn velocity pilot

Thanks, inetdog.  The issue with the mosfet isn't the "on resistance", which is spec'd out as around 0.5 ohms when the device is fully on... the problem is that it requires more than the 2-3 volts available to fully turn on.  That's unfortunately going to be the case with any mosfet I've looked at.  The problem with any solid state device I can find really boils down to the math: 14V minus the LM338 linear regulator drop, minus 9.6V for the LED, just doesn't leave much for the switch voltage.

Other alternatives that I've looked at, like solid state relays, switching transistors, etc., all have their own drawbacks (cost, heat, similar Vds requirements, etc).  

On the other hand... I'm certainly no deep expert ... if you have any specific PNs in mind, I'd love to investigate - Thanks!

I'm sure you're correct regarding reflectors.  I'm not necessarily limited to the form factor of the old bulb.  Are there any commercially available reflectors?  I'm not even sure where to look!  Any insight would be very welcome.

Thanks again!

Dave


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## calflash

My dad has an rv-9 and I built two landing lights for it. I used different LEDs than you but I used optics from cutter electronics. They might have something that would work for you optic wise.

A wrinkle I ran into was radio interference on FM bands from the driver when I was testing it which concerned me about use in the plane. The driver was from taskled and the builder said that some interference would be present. So I have been looking for a solution.  Have you experienced anything like that?

one other thought: Have you looked at something like a Cree XM-L? I think the voltage is in your target 3-5V.


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## TEEJ

mn velocity pilot said:


> Sorry, forgot to answer the other question from TEEJ.
> 
> For an experimental aircraft, there are no rules or requirements as to  what I can use for a landing light.  I'm free to innovate.  Basically,  brighter is better, and the rear end I save with a good landing light  just might be my own.




Brighter can mean a lot of lumens, or, a high cd.

Lumens would be the total output, and the cd would be a rating of how far the beam can be projected.




Is the landing light primarily to see where to land with, like a car head light, or, a primarily marker light so others can see you?

The reason is that the cd of the landing light would need to be high to project a useable beam far enough to illuminate what you needed to see (The ground you wanted to land on, far enough ahead to tell if you were going to hit a cow before you could stop, etc...), or, to search for the landing area, and so forth.

Many landing lights are rated ~ 600,000 cd, or much much higher,....and your set up would be lucky to hit 20,000 cd.  That would make yours OK to be SEEN, but, about useless to SEE with.



How far away do you need the beam to be able to illuminate what?


The shape of a reflector to project an LED is not the same as what is needed to project an HID or halogen light, etc.  The depth of the "bulb" relative to the reflector bowl, and the diameter of the bowl, and other factors, are simply wrong for other illumination sources.

After  that, there's the question of the size of the beam, as a tightly focused small circle of light can be projected farther than the same out put spread out to cover a wider beam angle...so the total out put, and its distribution, will all need to be considered when you are designing/purchasing, a lighting system.

All of that gets rolled into the "How far away do you need the beam to be able to illuminate what?" question....as the specs will then be designed to ACHIEVE the answer to that question.


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## idleprocess

I would suggest looking at number of single-die LED's (such as Cree's XM-L2) rather than array LED's (such as you originally experimented with) using individual optics/reflectors to try to replicate the beam pattern of the OE landing light.  You might find that typical LED tints (5000K+) don't replicate your experience with the original incan light, so you might look at neutral or warm tints when selecting LED's.


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## mn velocity pilot

Thanks for all the input!  Here's some responses... 

To calflash - the off the shelf drivers I've looked at all use switching regulators, which are more efficent, but which can throw quite a bit of electrical noise.  That's part of why I chose a linear regulator.  The other big factor was simplicity... a linear regulator just requires a resistor...

Teej - wow... much to think about, and I really appreciate the detailed input.  I've been focused on lumens, since in the small amount of reserach I did on the topic of measuring light output, I quickly realized that standards are not all, well, standards... candlepower in particular seemed like a very weak way for comparative measurements.  Again... I'm certainly no expert... I need guidance here.  

I seldom fly at night... in my 1100+ hours in this airplane, I've logged just a handful at night.  Further, the existing "standard" landing light, a 250W bulb, really doesn't do much AFA lighting up the runway on short final.  Where it is important is when you're taxiing in the dark... which, again, I don't do that much.  So, the primary purpose in my mind is for air to air visibility.  That's why I've been working on a strobe system as opposed to just a landing light.  If all I wanted was a landing light, I'd just have bought a bulb.  So... to try to answer your question, I'd like to be able to see obstructions perhaps 50-100 feet directly in front of me.  Note that airports usually have pretty good lighting for runways and taxiways, which helps.  

Having said all of that, projecting the light in a wide angle in front of the plane is really pretty useless.  Even for air to air visibility, the problems are going to be directly in front of me, not off to the sides.  Given that I'm moving forward pretty fast (usually around 200 mph), sending photons off to the sides doesn't do much good.  

I do have a reasonable amount of room for an optics system (as long as reasonable is... reasonable).  Where would I look to find options or ideas for an optical system?

idleprocess - thank you sir!  I'll take a look at the XM-L2s.  I had been assuming that a bright white bulb would be preferred - sounds like you think a warmer light would be more visible?

THANKS TO ALL!  I really appreciate all of your input!

Dave


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## TEEJ

A warmer light is generally less visible,  and, for a given source, the cooler beam will have more lumens.

In wet weather,  a warmer beam will typically work better than too cool a beam though,  if foul weather might be a factor.  

You are 100% right about CP ratings, hence my suggestion about cd instead, which at least can be traced to an ANSI standard. 

If you only need a few hundred feet of illumination,  for taxiing etc...that's easier to obtain. 

To BE SEEN, you need the beam angle to be wide if you are counting on one light for protection.   You need visibility to the side too.
If you only need 200' ahead...you can spare some beam width.

Will your vision be night adapted in use?  If so, you need far lower lux levels to see.

The cd of the light is used to calculate the lux for any given distance.

Most people with night adapted vision need at least 1 - 5 lux on something to tell anything about it, for example....unless very close. 

The ANSI standard uses 0.25 lux to state a lights range in meters. ..The range at which the lux has dropped to that.  To get 1 lux, you'd need to be at half the distance stated for 0.25 lux.


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## idleprocess

mn velocity pilot said:


> idleprocess - thank you sir!  I'll take a look at the XM-L2s.  I had been assuming that a bright white bulb would be preferred - sounds like you think a warmer light would be more visible?


It's really a matter of what you're used to and what works for you.  An often-mentioned issue with cooler color temperatures is a perceived _flattening_ of the scene and resultant lack of depth perception and recognition of objects.  While CRI (Color Rendering Index) for the more lumens-per-watt cool tints has improved, they still lag behind neutral and warm tints.  Lack of light is obviously a big problem that needs to be addressed without a doubt, but light quality also matters.

Suggest you start by getting those existing LED's working and deciding how you like the tint and color rendition in general - perhaps a few outdoors tests to see if you like them.

Insofar as optics go, you will probably be able to find suitable 25mm (or smaller) diameter TIR (Total Internal Reflection) lenses or reflectors that can be fit to individual LED's.  You'll likely want a mix of narrow, wide, and flood patterns - and perhaps some elliptical floods (available from most TIR suppliers) as well for side spill - in order to get something that does what you want for in-air visibility, final approach lighting, and taxiing.  Heatsinking this beast will be an issue unless you plan on only running it for brief periods.



TEEJ said:


> A warmer light is generally less visible,  and, for a given source, the cooler beam will have more lumens.
> 
> In wet weather,  a warmer beam will typically work better than too cool a beam though,  if foul weather might be a factor.


The lumen loss is going to be hard to perceive and the added color rendition and/or familiarity of a warmer tint relative to the existing landing light could be more important.

I'm not sure that a warm 2700-3000K tint is really necessary, but 5000K+ just seems to have _issues_ outdoors and I tend to like neutral and cool tints.


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## idleprocess

Also, if you're looking to go more exotic with fewer emitters, there are some powerful options out there from Luminus capable of 2000+ lumens from a single die (makes focusing in an optic or reflector much easier).  The downside is the staggering heat production, low efficiency, and lack of options when it comes to optics relative to Cree and the like (although it looks like Luminus has compiled a list).


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## TEEJ

idleprocess said:


> It's really a matter of what you're used to and what works for you.  An often-mentioned issue with cooler color temperatures is a perceived _flattening_ of the scene and resultant lack of depth perception and recognition of objects.  While CRI (Color Rendering Index) for the more lumens-per-watt cool tints has improved, they still lag behind neutral and warm tints.  Lack of light is obviously a big problem that needs to be addressed without a doubt, but light quality also matters.
> 
> Suggest you start by getting those existing LED's working and deciding how you like the tint and color rendition in general - perhaps a few outdoors tests to see if you like them.
> 
> Insofar as optics go, you will probably be able to find suitable 25mm (or smaller) diameter TIR (Total Internal Reflection) lenses or reflectors that can be fit to individual LED's.  You'll likely want a mix of narrow, wide, and flood patterns - and perhaps some elliptical floods (available from most TIR suppliers) as well for side spill - in order to get something that does what you want for in-air visibility, final approach lighting, and taxiing.  Heatsinking this beast will be an issue unless you plan on only running it for brief periods.
> 
> 
> The lumen loss is going to be hard to perceive and the added color rendition and/or familiarity of a warmer tint relative to the existing landing light could be more important.
> 
> I'm not sure that a warm 2700-3000K tint is really necessary, but 5000K+ just seems to have _issues_ outdoors and I tend to like neutral and cool tints.



Oh, I agree that 5000 ºk is a good target. To me, that's as cool as you want to go.

I just wanted to get the focus onto the lux needed at what range issues.


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## idleprocess

TEEJ said:


> Oh, I agree that 5000 ºk is a good target. To me, that's as cool as you want to go.
> 
> I just wanted to get the focus onto the lux needed at what range issues.



With best-in-class CRI, sure.  With the maybe-65 stuff that's widely available, not so sure that's a good plan.

Cree X-ML2 datasheet.  CRI's for the more pedestrian bins are 65/75/80 for cool/neutral/warm; minimum CRI 80 in 2600-4300 and minimum 90/95 in 2600-3200.

Again, better than just a few short years ago when CRI wasn't even specified, and up to the OP's preferences.

Actually, 3200 sounds excellent ... wonder if there are any discounts available on the far edge of the bin since most people so love their 2700K incan-like tint.


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## emtiv09

mn velocity pilot said:


> And here's the airplane in the hangar:
> 
> 
> 
> 
> 
> Dave



what plane is this??


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## TEEJ

emtiv09 said:


> what plane is this??



It's the plane he built....as described in this thread, and then showed a picture of in its hangar.


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## mn velocity pilot

I completed my work (or at least for now)... here's a link to an Instructable documenting what I did:

http://www.instructables.com/id/LED-Landing-Light-for-Experimental-Aircraft/

At some point I start thinking about even more power...!


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## TEEJ

mn velocity pilot said:


> I completed my work (or at least for now)... here's a link to an Instructable documenting what I did:
> 
> http://www.instructables.com/id/LED-Landing-Light-for-Experimental-Aircraft/
> 
> At some point I start thinking about even more power...!



XML2 LED can be pushed a lot harder than the ~ 300 lumens you are getting from them. You could be getting up to 500-700 lumens from each LED for example, about doubling your output. When pushed hard, you can get up to ~ 1,200 L from each LED, instead of ~ 2k L for all of them combined, and so forth.

Heat management does become an issue of course as you up the performance. 

It was hard to tell in your pics, but, does any part/enough of your exterior nose lens protrude enough to be visible in profile/from the side?


If so, a simple nose reflector that would reflect some light to the sides, and/or removing and/or re-aiming the optics from some of the LED (If any are forward enough to be visible from the side, etc...) to increase lateral dispersion, etc, could help with lighting to the sides.

It could be an artifact of the pics, but, in the pic at least, your light's cover appeared to be cloudy.

This can greatly reduce transparency and output....and, if it wasn't cloudy, and the apparent cloudiness was due to reflections, that typically means you could benefit from an AR coating (to reduce reflection and increase transparency/transmission).


For a nose reflector, think of a simple reflective strip aligned so that its thin edge faces the light, and the light passes along its reflective width on either side. That minimizes its shadow, and, maximizes the lateral visibility.


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## mn velocity pilot

Thanks, TEEJ! 

Yes, for sure, I can drive the LEDs much harder. The issue became that to do so would really force the shift from a linear regulator to a switcher. Switcher's are more efficient, but are more complex and can create electrical noise (which can be an issue in an airplane)... so I took the easy way out (for now). The lamp assembly itself can handle much more power, so I'm all set for when I can get back to thinking about more power. 

Yes, the plexiglass lens on the aircraft nose was cloudy when I took the picture. It was a very humid day, and there was condensation all over everything. Normally it's quite clear.

Some side dispersion would be OK, but it's really forward visibility that I'm after. At 200 mph it's what's pretty much directly in front of me that I worry about. The closure rate is very fast. Also, the light is set back far enough into the nose that it'd take more work than I'm up for right now to gain more side dispersion. 

Anyway, thanks for taking a look. Any suggestions on a, say, 10amp switching regulator that can be controlled to create a programmable flashing mode?

Thanks again!


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## mn velocity pilot

Me again!

I've had the flashing landing light deployed in my airplane since this spring, and it seems to be working OK... but, as winter is coming, and I'll have time on my hands, I'd like to think about improvements. 

I published an instructable on my implementation here: http://www.instructables.com/id/LED-Landing-Light-for-Experimental-Aircraft/

As winter is coming, and I'll have time on my hands, I'm starting to think about the next generation of this setup. My questions to the forum are:
- There are nowadays many "off the shelf" LED based aircraft strobe systems. The ones I've seen are incredibly bright, but don't have much circuitry at all, especially the big, bulky current limiters that I've got, and certainly don't seem to generate much heat. What gives? _*What are most manufacturers doing for flashing current limiters?*_
- I'm using 10W CREEs, with either 7 or 9 in parallel - i.e., in theory, I can drive it with between 70 and 90 watts, or between 21 to 27 amps of current. The linear regulator I'm using (an LM338) maxes out at 5 amps. _*How can I increase the current to get more brightness?*_
and 
- I'm flashing these CREEs with 5 x 100ms pulses / second. The pulses are in a rapid burst: flashflashflashflashflash .... pause ... flashflashflashflashflash. One idea that's crossed my mind is to just, gulp, eliminate the current limiter and just plain flash 'em. My thinking is that what really kills the LEDs in an overcurrent situation is heat, and that because my average current, or average power, is low due to the flashing, and also because of the inherent current limiting effect of the flash circuit and all the wiring, the instantaneous power will be far less than the average power, and so the heat may not be an issue. _*Is just flashing the LEDs and hoping I don't fry them just plain dumb?*_

I'd be grateful for any input... _*in net, how are the other guys doing this???*_

THANKS!

Dave


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## cujet

mn velocity pilot said:


> Me again!
> 
> I've had the flashing landing light deployed in my airplane since this spring, and it seems to be working OK... but, as winter is coming, and I'll have time on my hands, I'd like to think about improvements.
> 
> 
> 
> Dave



I'm a pilot, A+P and engineer. I've installed the Whelen Parmetheus in both PAR 36 and PAR 46. I even recently purchased a Parmetheus plus (supposedly 40% brighter) Taxi light. All of them have been underwhelming. I'm not happy with the light output, of approx 1200-1700 lumens, depending on model. 

So, with that in mind, I recently purchased some motorcycle aux lights made in China. They are truly amazing lights due to the very small size (about 2 inches in diameter) and outright power, claimed 3600 lumens. Each light contains 4ea Cree XM-L-T6 emitters, generally considered to be 1080 lumens each. 

I've installed one on our Extra 300L experimental/exhibition stunt plane. That single "toy" of a light is worlds better than the Parmeteus and GE4509, both on at the same time, in my Cessna.


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