anonymous coward wrote:
Jim Weir wrote:


I'm not sure anybody really "knows". We've seen some subjective comments
like "boy they are really bright" and "gee, they sure are green", but I do
not believe anybody has quantitative data as to whether the actual FAR
optical specification has been met.

OTOH, I've seen some comments in here about the FAR specification being so
loosey-goosey that two birthday candles inside a wine bottle strapped to
the wingtip would be OK.

As you say, I'd like to see some hard photometric data taken with
calibrated equipment and a checklist of HOW this particular installation
meets the FAR.


I'm just browsing (i.e. not building a plane) so I haven't got the FAR
regulations to hand. But I've played with Luxeons quite a lot so this
piqued my interest. What exactly are the FAR requirements?

Luxeon provide some good photometric data on their LEDs on their website.
http://www.lumileds.com/products/doc...ion_index.html
They give peak wavelengths, CIE chromaticity co-ordinates,
spectrophotometric measurements, deviation with temperature, luminous
efficiency...

IIRC the red-orange 1w LED gives out 55 Lumens of light output - which is an
order of magnitude better than a filtered lightbulb. Other colours give out
considerably less light - but even the green LED will be more efficient
than a green-filtered xenon-flash tube, for example.

Then there's the matter of making sure the right amount of light goes in the
right directions.

AC

Jim



(Bill)
shared these priceless pearls of wisdom:

-To Jim Weir and Group
-
-I am interested in using the new (to me) 1 watt and 5 watt LEDs for
-nav lights.



Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com



The problem is that everyone uses a different yardstick to measure the
light output, and not all the yardsticks measure length.

Which would you rather have over your shop bench, one of those tiny LED
that are so bright you have to blink, or an 8ft flourescent that you can
stare at all day? Candles, watts, candella, lux, lumens...the terms go
on and on and what the FAA specifies may have more to do with
measurement convenience than they do safety. It's been a while, but the
FAA chose measurements that emphasize total light output, while all the
LED manufacturers use metrics that emphasize intensity.

Your tail light will cover the rear out to a 70* angle on each side, for
a 140* sweep. The marker light cover from directly ahead, back to the
70* mark.(Draw a circle and mark it off in 3 quadrants and you'll see
hwo this makes sense). Allmost all the ouput intensity is concentrated
on the level with it tapering to about 5% of the max at 85* up and down.
Note these are minimum values. More intensity is always a good thing.

I'm at work, but I'm thinking that it is all in FAR23-1490 (or within a
few paragraphs thereof).


--
http://www.ernest.isa-geek.org/
"Ignorance is mankinds normal state,
alleviated by information and experience."
Veeduber