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I have a little bit of inside information on this specific model of LED position lights. Please forward this to the Cozy list.
The DAR, in this case, is doing the airplane owner a big favor. It is not at all surprising to me that a pair of GS-Air lights have failed FAA inspection.
As you may already know, I sell LED position light kits specifically for experimental aircraft. Thus, I am one of the few people in the experimental community that have the equipment, knowledge, and motivation to measure the actual light output of non-TSO'ed LED position lights.
GS-Air sells several models of LED position lights. The problem (from my measurements of one set of lights) is with their first-generation model, now called the "Ultra Light". They don't put out nearly enough light. (More on this later.)
I have corresponded with the owner of GS-Air frequently over the past few months about the light output of this particular model. He has agreed to either pull the model off the market, or at least label it as "Ultralight Aircraft Use Only." I convinced him of the wisdom of doing this. I guess I convinced him a bit too late.
I have not measured the output of any of his other models, so I cannot comment on them.
My goal in needling the GS-Air folks was three fold. 1) Safety of the experimental community. 2) I didn't want LED position lights in general to get a bad name in the market place, and drag my sales down in the controversy. 3) My lights meet FAA specs. My development costs and parts cost reflect that, so I want competing products to meet the same standards.
The specific pair of GS-Air lights that I measured showed, at most, 14 candlepower, in any direction. The light did not put out nearly what the FAA requires in nearly all directions. (The FAA requires a minimum of 40 candlepower in the forward direction, for example.) Only at a few spots on the outer edges where the requirements are low (0.25 cp) did the light meet the FAA standards.
The LED position light kits that I sell have never had any difficulty passing FAA inspection. Routinely, the DAR comments, "Holy crap those are bright!" :^)
>>>>> Why these companies have trouble meeting FAA specs <<<<
It seems easy to build an LED light. I thought it would be easy when I started in on the project. It turns out to be very difficult to fill the required FAA light output pattern simply and economically with LEDs. I ended up making a 3-D computer model that summed the output of each of the LEDs that I put in each light. The model compared the LED array output with the FAA required output. I then added LEDs and twisted them around until I managed to cover the FAA pattern with a good safety margin in all directions. (As an engineer, I knew that I had to leave in a good margin to allow for variations in manufacturing and the effect of aging of the LEDs.)
There is also the complication that the LED suppliers lie about the light output, and that there are variations in the light output between batches of LEDs. I measured the light output many LEDs before I selected the specific brand and model to use in my lights.
I still spot check the output of my lights to make sure that the LEDs I'm getting are up to spec.
This took pretty much all of my skills to accomplish (and I learned a few more on the way.) I think that other folks that have tried to design LED lights just didn't go through the full effort.
>>>> How to measure the light output yourself <<<
You can do a crude, but quite effective, measurement of the light output using an ordinary photographic light meter, a protractor, and a piece of string.
Set the lightmeter to measure "incident" light. Tape a string to the side of the lightmeter. Measure one foot of string and attach that end near the center of the position light (like to a hold-down screw.) The "Foot Candle" reading on the lightmeter will now read the candlepower output of the light. Straight ahead, (in the direction of travel) the meter should read at least 40. As you swing around to the side of the airplane, you should read 30 CP or more at 15 to 20 degrees off the nose. At 25 degrees all the way to 110 degrees off the nose, you should read 5 cp or more. (These are all on the horizon.)
I've attached MS Word file with chart showing the angles and candlepower readings you should get. I supply this chart with every light I sell so folks can check to make sure they built the light correctly.
Using a photographic lightmeter, the reading might be as much as 20% off. Thus, it is a useful, but crude measurement. It lets you know if your lights are WAY off.
At 05:52 AM 12/17/2005, you wrote:
Begin forwarded message:
From: "<mailto:iflycozy@bunchlaw.com>iflycozy@bunchlaw.com" <<mailto:iflycozy@bunchlaw.com>iflycozy@bunchlaw.com>
Date: December 16, 2005 10:48:39 PM EST
To: <mailto:cozy_builders@mailman.qth.net>cozy_builders@mailman.qth.net
Subject: COZY: DAR Update on my LED/Strobe lights for Phase II
For all of you who have read my posts since June 05 relating to my very tough DAR on my wingtip LED/strobe lights, here is an update.
As you will recall, I have non-TSO'ed lights from gs-air.com. They are really cool, bright and uses 4 amps for two strobes and four position lights. My DAR would not sign off Phase II with those lights with the language of "Unless appropriately equipped for night or IFR flight, ..." which would allow me to make a logbook entry to fly at night. My DAR would only give me Phase II with VFR day only restriction because he interpreted the words "approved anti-collision light system" in FAR 91.205(c) to mean only approved by the Administrator. My DAR's boss in the Louisville FSDO office sent me an email saying that their position is that I must have "approved" anti-collision lights, i.e., TSO or PMA or a field approval. Since PMA does not exist for experimentals and Atlanta or any DER would not give me a field app roval, I was told that if I wanted to flight at night, all of which night equipment is required for IFR, I must have TSO'ed wingtip lights. Nat and everyone else said to get another DAR, so the following is my report.
I have talked with EAA in Oshkosh (Joe Norris who was very helpful) and they put my in touch with a DAR in Illinois in the MIDO office, whose boss/Prinicipal Investigator (PI) is in Vadalia, OH. Vadalia is in my region or district. They told me today that although my analysis of the FARs and evidence showing that my wingtip lights meet or exceeds the airworthiness standard for approved position/anti-collision lights, that they would have issued me the above quoted language if I had originally applied for my airworthiness certificate from them, BUT that since I started out in FSDO, I am subject to their mercy as I can not escape from the FSDO office in Louisville. So, there you have it. I must change my very cool, slick LEDs for old technology which draws about 15 amps (strobes and nav lights) from Whelen as they are the only TSO'ed lights that I have found. Of course, Whelen lights are almost $900. So, the little man has lost and the moral to this story is GO TO THE NATIONAL EAA TO GET A DAR FROM YOUR LOCAL MIDO OFFICE BEFORE YOU APPLY FOR AN AIRWORTHINESS CERTIFICATE, even if a local FSDO DAR was recommended to you. After my problem with my lights, need I say more. All of you guys still building (which I am after flying 25 hours--you know, still tweaking) MUST learn from my mistake. Don't get involved with the FSDO office as you will be in a world of hurt ($$$$) very fast.
Matt Bunch
Lexington, KY
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Bill Dube <LED@Killacycle.com>
http://www.killacycle.com/Lights.htm
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