Nav light replacement bulb

[Cruiser]

the concept is solid. The idea is valid. 

"Certified" aircraft go through a process of testing and approval. Each aircraft must pass a final inspection and performance test, the logbook entry documents the acceptance as approved by the FAA for "certified" status. 

To maintain that "certified" status the aircraft must remain in the "as certified" condition. There are no exceptions to the component parts. If something is removed/replaced the exact same part must be put back in. 

Now there are many, many "ordinary" parts that we can point to and say.......... come on, really ? Why ? But in defense of the certification, how do you know ? Without some evidence, (STC) you are modifying the original "certified" aircraft to be something else. 

[EricJ]

4 minutes ago, JimB said:

Just to clarify, the current TSO for position lights is TSO-C30c. The TSO for these lights would be TSO-C30b dated 1957

 http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgTSO.nsf/0/cfa519bb271ee2df86256e93005f4e30/$FILE/TSO-C30b.pdf 

This one references SAE AS271, which shows up as "Cancelled" on the SAE site, although they'll still charge you $81 if you want a copy.

[Hank]

So my generic GE incandescent landing light has some sort of FAA approval, not indicated by packaging, labeling or package inserts??????

[skydvrboy]

On 5/3/2018 at 4:13 PM, Albatros said:

So, I had conversation with FAA, about legality of pilot/operator replacing aircraft navigation  Light bulb. 

Official FAA rules say that pilot can replaced any light bulb on aircraft without any need for mechanic to signe it off. Even if you are changing bulb to LED!!!!

only thing that matters you install correctly color where it should be. There is no such a thing as “that bulb is not aircraft/FAA approved” 

and don’t kill messengers (me)!

FWIW, right around the time I installed my Whelen LED landing light and my LED interior lights, we had the inspector from the Wichita FSDO come give a safety talk to our aviators group.  I asked the same question about my landing light and basically got the same answer.  His answer was something to the effect of "If we allow you to change tires and repack bearings, do you think we care about a light bulb."

[jetdriven]

2 hours ago, Hank said:

So my generic GE incandescent landing light has some sort of FAA approval, not indicated by packaging, labeling or package inserts??????

No, and if you can install an LED bulb like the grote tractor beam  on Amazon that is brighter,  Has a similar pattern, and has no glare and halation ir radio noise, I think  you’re OK. 

[philiplane]

9 hours ago, Hank said:

So my generic GE incandescent landing light has some sort of FAA approval, not indicated by packaging, labeling or package inserts??????

Yes, it was accepted during the certification of the airplane and the issuance of the Type Certificate. The parts manuals are not "approved", they are accepted with the data package Mooney provided to the FAA, so the parts listed therein are acceptable to the FAA. 

In addition, the landing lights in your Mooney were never tractor lamps to begin with. The PA36 size 4509 lamp, and the PAR46 size 4522/4581/ etc lamps were all designed for aircraft use first. 

Edited September 21, 2019 by philiplane

[cliffy]

13 hours ago, philiplane said:

Yes, it was accepted during the certification of the airplane and the issuance of the Type Certificate. The parts manuals are not "approved", they are accepted with the data package Mooney provided to the FAA, so the parts listed therein are acceptable to the FAA. 

In addition, the landing lights in your Mooney were never tractor lamps to begin with. The PA36 size 4509 lamp, and the PAR46 size 4522/4581/ etc lamps were all designed for aircraft use first. 

And because they conform to an industry standard design (4509, 4522, 4581) the design can be looked up in industry literature and can be made by any manufacturer to that design and qualify as a "standard part".  The FAA reserves the right to inspect the manufacturer at any time to make sure the part is being made to the industry standard in every way.  No PMA required. Read my previous post reference material. No different than AN bolts or hydraulic fittings. You can't replace a AN bolt with a Class 8 car bolt even though its many times stronger, you can't replace an AN oil fitting with a printed part even though its cheaper to do it that way. It has to conform to the industry standard design on how it is to be made.

To rcap and old thread, PMA only means that the maker has been approved to make a certain part and sell it for use on certified aircraft. That's all a PMA does. It doesn't specify that the actual use of the part is legal in a variety of applications. That is left up to your A&P. If the PMA'd part is an exact replacement for the part specified in the Type Certificated (or legally altered) airplane or appliance then its legal to use. If on the other hand it was made for one application but you are using it in some other application the mere fact that it is PMA'd does not make it legal to use. 

The Type Certificate Data package that the airplane manufacturer submits to the FAA for approval includes call outs for every bolt, washer, nut, rivet, sheet of aluminum, light bulb, wire, hose, engine (down to dash number) propeller, etc, etc. Its all included in the approved type  design package submitted saying that if the manufacturer makes another copy the same way it will be approved. Any deviation from that package by them or you require some kind of further approval.  Is the bolt you are substituting an approved substitute? MS for AN comes to mind as there are several kinds of "pieces" that can be used on certified aircraft (that's all in another AC- AN, MS, Space qualified all come to mind). Is that light bulb you are putting in is it qualified in some other manner than the original Type Certificate part if it doesn't match the called out part exactly? Would you put in a Chevy fuel pump because it will do the exact same thing the approved part will do only cheaper? To go by " meets performance" standard is specifically called out in my above reference as needing SPECIFIC FAA APPROVAL to use.   That's why Whelen Chroma bulbs are for experimental use only right now. They don't have approval for their use on certified airplane yet EVEN THOUGH THEY ARE BASICALLY DROP IN BULBS. Go read their own catalog (I did last night). They have no approvals yet. 

There is a bottom line that says "what are my chances of getting caught?" or am I correct in my assumption that its legal to use this and can I defend it if I'm questioned? Chances may or may not be slim. We've had cases here on MS where planes have been ramp checked and grounded and in one case scrapped because of a ramp check. Its a roll of the dice. One FAA inspector may let it pass and another may bring the hammer down. If you are REALLY legal they can't touch you. 

I'm not telling you what to do I'm just showing the possibilities  of what can happen You can do what you want to your airplane,  I don't care. 

There is a reason why approved parts are so expensive. They went the extra mile and got them approved for use. Same with any approved aircraft part. If you want to be your own engineer then go experimental then you are in control of what goes into your airplane otherwise we are stuck with (in some cases) archaic rules and regulations to abide by. 

I'll go back to my many times posted question- if what you contemplate doing you feel is legal go to your local FSDO and ask them or better yet if you are so confident that it is OK,  then install the part, sign it off in your log book and then go to your local FSDO and show them your log book and see what they say. I'll be happy to eat any of what I have said here  if they agree with you- because your mechanic has to sign HIS name to your log book for eternity for what he does. No guts to sign it off and show it,  no glory. 

 

 

 

[philiplane]

1 hour ago, cliffy said:

   That's why Whelen Chroma bulbs are for experimental use only right now. They don't have approval for their use on certified airplane yet EVEN THOUGH THEY ARE BASICALLY DROP IN BULBS. Go read their own catalog (I did last night). They have no approvals yet. 

 

 

 

Whelen has had FAA TSO-C30c approval for the Chroma series lamps since early 2018.

[cliffy]

Then why does their website catalog say something different? 

 

• All electronic logic conformal coated for weather resistance • O Ring allows for a more secure connection to lamp socket, reducing wear over time • Nickel Plated hard contact eliminates premature wear • Keeps original lens configuration to maintain FAA approvals of light assembly • LED bulbs have a 10,000 hour operating life, while incandescent bulbs have a fragile filament and a 300 hour average life • NO EMI / RFI interference, as Chroma bulbs are built using fixed current sources • 85% reduced current draw • Five year warranty • FAA Approvals Pending

Edited September 21, 2019 by cliffy

[philiplane]

that's an old catalog. The product data sheet printed August 2018 shows the approval. They had it before then, but I don't recall the date. I find out about new products first because I have high level contacts at Whelen Aerospace Technologies.

https://www.whelen.com/pb/Aviation/Product Sheets/Chroma_Series.pdf

[cliffy]

OK game set match to philiplane!

[Bob E]

Ok, I'll keep the pot boiling a bit longer.  What the heck.

TSO-C30b is an ancient TSO dating back to 1957.  It's an “active historical” TSO, not even available for new designs.   And as EricJ points out, the SAE specification to which it refers, SAE AS271, shows up as "Cancelled" on the SAE site.  How can Whelen claim to have TSO approval for a position light bulb when the spec is cancelled and approval is no longer available?

From the FAA website:

 

 

[cliffy]

SO that begs the question- Is there a newer TSO that is used for compliance today ?

Or is everything just "performance" based with specific approvals  to the old TSO numbers?

 

 

[markgrue]

4 hours ago, Bob E said:

Ok, I'll keep the pot boiling a bit longer.  What the heck.

TSO-C30b is an ancient TSO dating back to 1957.  It's an “active historical” TSO, not even available for new designs.   And as EricJ points out, the SAE specification to which it refers, SAE AS271, shows up as "Cancelled" on the SAE site.  How can Whelen claim to have TSO approval for a position light bulb when the spec is cancelled and approval is no longer available?

From the FAA website:

 

 

If you look closely you will see a small "b" at the end of the TSO number.  The new TSO has a "c" at the end

 

Mark

[EricJ]

You can look up TSOs on the FAA site, just like you can look up ADs, STCs, etc.   You can look under each TSO and see who has approval for it and for which of their part numbers:

http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgTSO.nsf/MainFrame?OpenFrameSet

As mentioned, TSO-C30b has been superceded with TSO-C30c.   I'm not sure whether aircraft certified with a previous TSO (TSO-C30b) can automatically just use components from a superceding TSO, although AC 20-41A talks about substituting TSO equipment with a "similar" TSO.   Maybe that's what they mean. 

[cliffy]

Here's another rabbit hole to go down-

Are CAR3 airplanes required to use only TSO'd equipment?

What is the requirement for the use of TSO'd equipment? 

Can non TSO'd equipment be used in CAR3 airplanes ?

I seem to remember something way back about rotating beacons and strobe beacons that said CAR3 didn't need TSO'd beacons because they were built before the Pt 23 requirements. 

Do all radio installations have to conform to TSO units? Do KX 170 radios have a TSO? I don't think so

I also seem to remember that certain equipment because of its function has to be TSO'd to be used in any airplane (GPS and transponders come to mind)

Just random thoughts while siting here.   

[Bob E]

57 minutes ago, EricJ said:

You can look up TSOs on the FAA site, just like you can look up ADs, STCs, etc.   You can look under each TSO and see who has approval for it and for which of their part numbers:

http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgTSO.nsf/MainFrame?OpenFrameSet

As mentioned, TSO-C30b has been superceded with TSO-C30c.   I'm not sure whether aircraft certified with a previous TSO (TSO-C30b) can automatically just use components from a superceding TSO, although AC 20-41A talks about substituting TSO equipment with a "similar" TSO.   Maybe that's what they mean.

As MarkGrue said: "If you look closely you will see a small "b" at the end of the TSO number.  The new TSO has a "c" at the end."

That's true.  So then why does Whelen claim that its position light bulbs are TSO's under C30b? 

 

[Bob E]

It gets interestinger and interestinger.

The "newer" C30c, is itself is more than 30 years old; LEDs hadn't been invented yet.

But I have some questions.

1.  I read through TSO C30c. (Thanks for the link EricJ!)  When this TSO refers to "position lights" it clearly refers to the entire position light assembly, not to a light bulb.  It includes standards for "installation procedures," "wiring diagrams," and "list of the major components."  That clearly isn't a TSO for a light bulb.

2.  TSO C30c says it "prescribes the minimum performance standards that aircraft position lights must meet in order to be identified with the applicable TSO marking."  If the position light assembly, not just the bulb, is what's being TSO'd, what basis is there for TSO'ing an individual light bulb separate from the assembly?  If the actual bulbs themselves must be TSO'd, why is it that the incandescent position light bulbs specified for the M20C (which I still have, and which are identical to those in the photo of the original post at the top of this thread) are NOT marked as TSO'd?  There is no "applicable TSO marking" on them.  Does that mean the exact-replacement-spec incandescent light bulbs are not TSO'd and therefore not legal?

3.  Light bulbs are generally cross-referenced; different manufacturers have different part numbers.  The part number on the incandescent position light bulb for my M20c is WL-A-7512-12.  That's a RAPCO bulb. The same bulb is made by made by different manufacturers; each has a different part number.  See for example this cross-reference chart:  www.csobeech.com/files/LampCrossReference.pdf.   What they all have in common (other than Whelan, which has a completely different part number) is 7512-12.  There are plenty of 7512-12 LED position light bulbs on the market.  If light bulbs themselves are not (or at least do not have to be) TSO'd, and if under current FAA interpretation of the regs the owner can replace light bulbs (see my earlier post, including the reference to the article in the October 2019 issue of AOPA Pilot), what basis is there for saying it is not permissible for a pilot to replace a 7512-12 incandescent bulb, with a 7512-12 LED bulb? 

 

[cliffy]

Because as mentioned, the bulb itself meets an industry standard for design with a glass globe, filament, wattage, reflector, etc, and is considered a  "Standard Part"  by DESIGN not operation. The bulb when used in conjunction with a TSO'd tip light assembly meets the TSO requirements for use on aircraft as an assembly. If the bulb is different then the TSO is not complete.  The industry standard that the bulb meets is probably MS-25309-7512/12  (24). This is a military standard for design and legal to use on certified airplanes because it does meet a military standard just like AN bolts. You do realize that AN bolts are "Army-Navy" specification hardware,  (AN 4-15A). Again, legal to use because they meet the military (industry) standard for manufacture. 

Standard parts require no PMA either because they are made to a widely available industry standard. for manufacture. 

There is no comparable 'industry standard" for the LED bulb that has been checked to be in compliance with the TSO'd tip light assembly.

Its made an entirely different way than described in the "industry standard"  (Read my previous reference material)

Each LED bulb or assemble has to have its own approval or show that it meets the TSO requirements to be used. 

That's why if a bulb says its in conformance to the TSO by performance (and not meeting the called for design) it has to have specific approval by the FAA. Hence the price difference between the approved bulbs and the also rans.

There is a big difference in "built to the approved design" and "performs the same as the design".  Its all in the legalize. 

This is all applicable to "Certified" airplanes. Experimentals are another breed.

[EricJ]

Without access to the SAE standard that the TSO references I couldn't say for certain what's what, and I spent a lot of my engineering career developing and working with standards.  Without the SAE standard or it's contents or specs in front of you, I don't know how one could say what the TSO requirements are.

Given that the associated FARs specify light intensity and color and visible angle relative to the installed airplanes, I can easily see how the bulb and assembly *might* be jointly specified, but without the specs I'm just *spec*ulating. 

As previously speculated, I suspect the brightness (intensity, whatever) and color and viewing angles are the issue.   The bulb will drive the brightness and contribute the angle spec as long as it radiates a pattern compatible with the spec.  e.g., if the spec requires lateral viewing over 90 degrees and the bulb provides 120, you should be able to make it work in an installation.   If the spec requires 90 degrees and the reflector in the bulb only gives you 45, well, then that *bulb* can't be compliant with the spec.   Likewise on brightness, if it's too dim, it won't make the spec.    Most of the plug-in LED replacements don't have reflectors and radiate 360 (omnidirectionally) along their axis as well as out one end, so meeting the directional requirements is probably easier with an LED since they don't have reflectors, and as long as it meets the brightness requirement it's probably easier to meet the angular and brightness requirements in any assembly.

For the color requirement, with an incandescent lamp that is met by the lens in the assembly filtering to the proper color.   With an LED, the *bulb* (or whatever you want to call it), provides the color, so now it is the part meeting the requirement, not the lens in the assembly.   The lens, whether colored for an incandescent or clear for an LED, must not attenuate the light too much so that the assembly no longer meets the brightness spec.

So, as has been mentioned, I suspect that with an LED the bulb is what meets most of the requirements, so that's what gets the TSO, and the assembly just has to not block the light in the required angular directions.   Since the assembly plays a part, it must also meet the TSO which would indicate that is meets the angular requirements.   With just a bulb stuck in the wingtip with a lens over it, i.e., no assembly to speak of, as long as the light and intensity and angles are met, it's probably fine. 

The assembly alone without a compliant bulb can't be counted on to meet the spec since it doesn't provide the brightness, and maybe not the color in the case of an LED light.  The light alone may not meet it if it is incandescent since it can't meet the color spec by itself. 

So if an LED lamp says it meets the TSO, I suspect that means that it meets the brightness and color requirements and has wide enough viewing angles as well.  I don't know how a compliant lamp could be put in a compliant assembly and not be compliant.   A compliant lamp put in an assembly that attentuates the light too much or blocks the angles too much would not longer be compliant.

This is just me speculating without being able to see the actual requirements in the TSO, but it's my best guess at what's going on and it also explains why *both* the lamp and the assembly can be marked compliant.

On another point, I've no idea why Whelen shows parts being TSO-C30b compliant for part numbers that don't appear on the FAA lists for either TSO-C30b or TSO-C30c.   That does seem a little weird.

[EricJ]

58 minutes ago, cliffy said:

There is no comparable 'industry standard" for the LED bulb that has been checked to be in compliance with the TSO'd tip light assembly.

Its made an entirely different way than described in the "industry standard"  (Read my previous reference material)

Bulbs have standardized bases so that they can all plug into the same sockets, with the same voltages and currents, put out the expected amount of light, etc.   In this case the construction of the base also determines the clocking of the reflector in a relevant incandescent lamp, so that's important to meet the angular radiation specs (I'm assuming, since I've no access to the relevant SAE spec) since the reflector cannot block the light across the required angles.

So I think they're standard parts.   Digging up the exact standard that shows the reference drawing for the base might be tricky, but there are definitely standards.

How the light is produced, to your point about being made differently, in the context of most standards is probably irrelevant and left to the implementer.   e.g., a light might be incandescent, halogen, LED, CFL, whatever.   If they meet the specs, whatever the specs are, how they got there is up to the implementer and in many standards is kept secret for proprietary reasons.    There's nothing inherent about LEDs that would suggest that they couldn't meet or be a part of the usual standard, as long as it meets the specs for that standard, e.g., a compatible base, electrical characteristics, brightness, etc., etc.  

[carusoam]

You guys are good!

 

Some of this is beyond compliant, but clearly says... FAA/TSO approved...

Is there an organization called the FAA/TSO... And did they actually approve something?  The unit, the bulb, or the installation?

 

I am familiar with some gov approvals...

• FDA approved carries intense meaning... even for stuff made since before the 1950s...
• FDA compliant has a lesser meaning... but still important.
• If something said FDA/TSO approved... the added letters would make me ask deeper questions... like what does that mean?

PP thoughts only, not a compliance officer...

Best regards,

-a-

[cliffy]

I guess its hard to understand that the STANDARD is THE DESIGN AND how to make it. AGAIN, you need to read the previous sheet on what constitutes a STANDARD PART.   A STANDARD PART is NOT the PERFORMANCE ONLY it INCLUDES HOW IT IS BUILT (globe, filament reflector etc ) They are built to specific plans. Every part of the part has to be exactly like the design specifies or its not a standard part. (NOT just the base). 

Again AN bolts are made to specific plans (industry standard design) as to type of steel, heat treat tolerances sizes and shapes  You cant make AN bolts from titanium and call them AN bolts just because they look like AN bolts. They have to be made the exact way from the same materials  the DESIGN says. 

Published specs that someone can build and REPLICATED the exact way the part was built and qualified as. 

I'll try a last time. In the above reference on STANDARD PARTS it specifically says that any part qualifying by PERFORMANCE and NOT DESIGN has to have a specific FAA approval. Please read the foregoing material. 

In the case of the Whelen bulbs THEY ARE compliant  Other LED bulbs are not even if the y say they "meet the PERFORMANCE of the TSO" Those need specific FAA approval because they are trying to qualify by PERFORMANCE and NOT DESIGN MATCH to the aforementioned TSO article. 

One last question, in any LED bulb you want to try what is the color temperature that they emit? And how does that affect the color wavelength emitted by the tip light you use it on as both the red and green has specific wavelengths that they have to meet and there are numerous color temperatures of LEDS. What LED emits the same wave length as a 12 volt incandescent bulb? Can someone tell me?

Edited September 22, 2019 by cliffy
add text

[EricJ]

3 hours ago, carusoam said:

Some of this is beyond compliant, but clearly says... FAA/TSO approved...

Is there an organization called the FAA/TSO... And did they actually approve something?  The unit, the bulb, or the installation?

I am familiar with some gov approvals...

• FDA approved carries intense meaning... even for stuff made since before the 1950s...
• FDA compliant has a lesser meaning... but still important.
• If something said FDA/TSO approved... the added letters would make me ask deeper questions... like what does that mean?

PP thoughts only, not a compliance officer...

Best regards,

-a-

That's a good question, as a lot of industry standards have private certification organizations that go with them, e.g., IEEE 802.11 is an IEEE standard, and the WiFi Alliance is an industry organization that does testing and certification of that standard.   Once they test it and bless it, it can have the WiFi logo and trademark.    That sort of thing is fairly common in industry, but in the case of TSOs and STCs and all that stuff I think it all flows from the FAA.

As far as greater or lesser degrees of blessedness from the FAA, there is a doc here:

http://fsims.faa.gov/WDocs/8900.1/V04 AC Equip & Auth/Chapter 09/04_009_001_CHG_198A.htm

that contains this definition:

"Meet Minimum TSO-Established Standards. Means that the equipment need not have TSO approval, but only meet requirements set by the TSO."

FWIW, that document doesn't use that phraseology anywhere, and I don't know whether any other FAA documents do or not, but at least the concept is known and recognized within the FAA.

 

1 hour ago, cliffy said:

I guess its hard to understand that the STANDARD is THE DESIGN AND how to make it. AGAIN, you need to read the previous sheet on what constitutes a STANDARD PART.   A STANDARD PART is NOT the PERFORMANCE ONLY it INCLUDES HOW IT IS BUILT (globe, filament reflector etc ) They are built to specific plans. Every part of the part has to be exactly like the design specifies or its not a standard part. (NOT just the base). 

Again AN bolts are made to specific plans (industry standard design) as to type of steel, heat treat tolerances sizes and shapes  You cant make AN bolts from titanium and call them AN bolts just because they look like AN bolts. They have to be made the exact way from the same materials  the DESIGN says. 

Published specs that someone can build and REPLICATED the exact way the part was built and qualified as. 

I'll try a last time. In the above reference on STANDARD PARTS it specifically says that any part qualifying by PERFORMANCE and NOT DESIGN has to have a specific FAA approval. Please read the foregoing material. 

In the case of the Whelen bulbs THEY ARE compliant  Other LED bulbs are not even if the y say they "meet the PERFORMANCE of the TSO" Those need specific FAA approval because they are trying to qualify by PERFORMANCE and NOT DESIGN MATCH to the aforementioned TSO article. 

One last question, in any LED bulb you want to try what is the color temperature that they emit? And how does that affect the color wavelength emitted by the tip light you use it on as both the red and green has specific wavelengths that they have to meet and there are numerous color temperatures of LEDS. What LED emits the same wave length as a 12 volt incandescent bulb? Can someone tell me?

There are all kinds of standards, and the definition of "standard part" in the link that you posted earlier is pretty basic and pretty much just says if there is a recognized industry standard and the part is compliant, it's a "standard part", and then gives examples like NAS, AN, SAE, JEDEC, and ANSI.   Some standards include manufacturing direction, but most don't.   Usually the spec is just a description of features that can be tested to assure that the part complies with the spec, whether those be physical dimensions, hardness, brightness, output power, frequency, temperature or whatever depends on the spec or the item being described, but usually how to build it is not part of the spec.  It is the job of the standards body to make certain the specification is complete enough to include all of the features that matter for that spec and how they are measured.   If reliability is important and some features or functions must be tested to demonstrate the reliability, then that should be included in the spec.    How the device manages to meet those specs is typically up to the manufacturer.   

To the case in point, things like brightness and color matter, because they must be recognizable from a certain minimum distance determined by the standards body (in this case presumably the SAE, unless the SAE doc just references something else).   Whether that color and brightness is obtained from an incandescent filament filtered by a colored lens, or by a colored LED, if the specifications are met the functionality is there.  If the "how to" is specified, then future innovations of obtaining the desired functionality with less power or less cost or higher reliability or something else can be stifled, and that's generally not desirable.    Hence the old-and-busted incandescent stuff and the new hotness LED stuff both are used and both have examples of fully meeting TSO-C30c.   The "how-to" probably isn't spec'ed to be incandescent, or the Whelen LED stuff couldn't meet the spec.

IIRC the FARs do spec wavelength for the light color, but I don't know whether the TSO does or not since I don't have the SAE spec.   For the old-school incandescent stuff the color wavelength is met by the lens filter color.   In the LED it can be met by the LED materials.  But, yeah, somehow color is specified, I'd guess by wavelength with some tolerance.   It's not that big of a deal to make a color lens for an incandescent that provides a certain color, and LED chemistry/materials can do the same thing.

 

[Steve W]

18 minutes ago, EricJ said:

IIRC the FARs do spec wavelength for the light color, but I don't know whether the TSO does or not since I don't have the SAE spec.   For the old-school incandescent stuff the color wavelength is met by the lens filter color.   In the LED it can be met by the LED materials.  But, yeah, somehow color is specified, I'd guess by wavelength with some tolerance.   It's not that big of a deal to make a color lens for an incandescent that provides a certain color, and LED chemistry/materials can do the same thing.

 

The very very old AC 20-74 does talk about how color is measured. Basically where it falls on the CIE Chromacity Diagram. Not sure how much a meter would cost these days, a non-certified meter looks to be about $300... Of course if we're talking about standard parts then the manufacturer of the emitter should be able to provide the necessary data. Probably something like this: http://www.nichia.co.jp/en/product/led_color.html

Which leads to an interesting question. Can I produce/have produced an LED bulb under owner produced parts? If I take the FAA specs to my local LED bulb maker and ask them to meet the following specs using these emitters, and test it after for proper color and brightness, does that make it legal? 

 

Edited September 23, 2019 by Steve W