Eric M. Jones
Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts
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 Posted: Tue Oct 16, 2012 6:27 am Post subject: Wig Wag Color and Frequency |
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Lest we forget, the feds have regulations for this stuff:
(c) Flashing characteristics. The arrangement of the system, that is, the
number of light sources, beam width, speed of rotation, and other characteristics, must give an effective flash frequency
of not less than 40, nor more than 100, cycles per minute. The effective
flash frequency is the frequency at which the airplane’s complete anticollision light system is observed from a distance, and applies to each sector of light including any overlaps that exist when the system consists of more than one light source. In overlaps, flash frequencies may exceed 100, but not 180, cycles per minute.
(d) Color. Each anticollision light must be either aviation red or aviation
white and must meet the applicable requirements
of § 23.1397.
Comments:
Aviation Red is orange-red to deep red, and for LEDs the CIE numbers equate to 610 nm and longer wavelengths. Although it is legal to make the red 650-680 nm or so, lot's of people are almost blind above 650 nm (including this writer). Scotopic (dark adapted) Luminous Efficacy (how well you can see it) at 610 nm is 23X what it is at 650 nm--for people who aren't red-green color-blind! Unfortunately 640 nm and 660 nm LEDs are real boomers so it’s a toss up. Aviation red for flashing reflects the FAA long-term love affair with neon lamps which predate xenon lamps. Nobody uses them but they remain legal.
Aviation Green is 495-534 nm. LED "true green" is 525 nm and they are very efficient and a good choice. But be careful, advertising gimmickry is everywhere. There are “greens” at 555 nm, and “greens” at 565 nm, but are not FAA legal. As of this writing there is ONE single FAA-legal green led color—525 nm. What gives? Well, green leds are simply not as evolved as red leds. The selection is poor and the prices are higher. You can get the right ones but they are more expensive—often several times as much as similarly constructed red LEDs.
Aviation White is not really on any spectrum. Aviation white is based on the allowable colors provided by tungsten filament lamps that approach what are called blackbody radiators (so we refer to them in Kelvin temperatures like very hot little iron stoves). The FAA allows white from very orange 1800K to 5000K but oddly, no higher! By the rules, xenon-white and some HIDs cannot legally be used as a tail-light color, but may be used as a landing light (weird...landing lights are options). The ICAO and SAE are much more generous with the white specs. This writer believes that the FAA is due to revise this to reflect the reality of new light sources, and it will probably accept the ICAO colors as their own.
Also, please note my earlier posting that said Wig wags are the more successful method of preventing bird strikes--other than staying home, of course.
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_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net |
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