Wiring Question

[spduffee]

Bear in mind I have been concentrating on other problems and haven't become operationally intimate with my 170A. My question is related to adding the second light on the right wing. I have a 337 that I will copy and submit, which will hopefully be approved. It is from a C-172.
I am looking at a photo of my panel which has one switch for "Landing Light". Does this one switch light up both bulbs at the same time? I haven't even looked at these burning except once or twice to see if they work. The corresponding fuse is a 25 Amp that is labeled "Land Lt / Dome Lt".
The 337 states the mechanic installed two switches, p/n 0713026-4, one for the outboard and one for the inboard, each fused with a 20 Amp fuse.
How could I do that, power all four lights, with the circuitry I have? I have a standard 35 Amp generator.
If not I could install just one bulb in each bay until I can make a major change to the electrical system.
Thanks for any input.

[spduffee]

Oh duh...yes, you're right...Ok, so plan B is solved, if I need to stick with two lights.
Any ideas on the 4-light scenario? I'm guessing my 35 Amp generator just won't handle it?

[bigrenna]

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[hilltop170]

The Aeroleds can be purchased with or without the pulse feature. If you already have the Pulselight feature you would want to buy the non-pulsed Aeroleds.

[spduffee]

Thanks guys. I haven't studied up much on LEDs due to their initial cost. We were going to use LED spotlights on a border crossing station, which would have saved $$ in the long run, but the sticker shock was too much. Eventually they have to get cheaper....
My intent is to install a wig-wag/pulse switch. Again, I don't know anything about the Aeroleds - once turned on, do they automatically pulse? Can you control the pulse? I wouldn't necessarily want to pulse all the time, just near aerodromes or when conditions call for them.

[bigrenna]

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[n2582d]

I'm sure George will jump in on this conversation soon. In the meantime take a look at his installation here.

[GAHorn]

I did not want to mess with the cockpit switching. I did not want to try to find some logical place to install another switch, nor to deal with placarding issues. I wanted a clean, dependable, and simple cockpit switching solution. So here's what I did:

I kept the original switch and placard and operation. But I changed the actual function of that switch. Instead of having the (original) switch supply POWER to the lamps...I had it provide a GROUND to a solenoid/relay (exact same one as used for a battery Master). I (Del actually, following my instructions) installed two battery master relays on the firewall, one of which supplies power to the taxi lamps, the other supplying power to the landing lamps. The original cockpit switch, in the taxi position, activates the taxi-solenoid, and in the landing position, also grounds the landing lamp solenoid, thereby lighting up all lamps, just like the original operation did. (ISee the two schematics below).

The solenoids are available from NAPA or from Spruce for about $17-$25 each. No change to the cockpit switching or placarding is required.

Existing Schematic.JPG

Modified Schematic.JPG

AS for the electrical load, I don't know about YOUR airplane, but mine has the original 35 Amp generator and powers everything just fine. Keep in-mind that landing/taxi lights are not continuous loads. They are intermittent, and for the short time that all FOUR lamps are powered ...roughly just the time on final approach and landing, ...any excessive load is supplied by the battery.
(Your generated electrical power only needs to exceed total continuous demands. Continuous loads should not exceed 80% of generated capacity.) While running around using them as recognition lighting, I only use the dual taxi lamps...which draw less (120 watts) than the original dual lamps (200 watts) set up. (The taxi lamps are Fresnel-lensed military motorcycle headlamps.,,,(dual) GE 4461, 12.8 volts, 60 watts, rated 300 hours. They put out a WIDE trapezoid pattern, about 45-degrees wide X 20-degrees high, with the highlighted beam rated 6,000 CP.)


While running around the Houston/Austin/Dallas-Ft Worth areas, I commonly receive comments like "looks like a 737 on final" with only the taxi lamps illuminated, so I have avoided the "wig-wag" mods that I hate. (Drives me nuts in fog, clouds, etc. and if you're in a green airplane, it'll drive you nuts in the dust left behind by red airplanes.)

[bigrenna]

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[GAHorn]

No argument from me, they DO grab attention. I just find them so distracting that I rarely use them even when I fly airplanes that have them. Chevy vs Ford, I suppose.

As for the LED's...yes they are a fine product which reduces electrical demands. But they don't light up objects like ordinary incandescent lamps do. They shoot a cool/blue spot which, due to lack of "scatter" fails to illuminate nearby objects that are out of the main beam. This provides a "tunnel vision" appearance and reduces depth-perception capability. They are an expensive loss of illumination, in my experience of the models I've used. I like LEDs in other services, but not in land/taxi lamps. (I believe AvWeb had a video of the differences at one time which might prove useful. I certainly recommend that anyone considering LED land/taxi lamps go fly and taxi them at a rural airport at night before purchase.)

[spduffee]

That's a clever install George. I think that's the way to go. I was trying to figure out where to put two additional switches. As Mies van der Rohe stated - Less is More.
I will eventually move up to halogens, when I can afford it, and I do want the wig-wag because I believe in the safety they provife, especially here in the NW where radios seem to be optional....

Edit: George- are those master relays you installed? Is it possible to snap a photo of them on your firewall, please?

[GAHorn]

Thanks. And the (electrical) work can be done per AC43.13 with only logbook entry. (I admit I'm anal about the wig-wag. Being seen is important.) Inexpensive wig-wag is available if you want it, you don't have to spend huge AMUs to get it done. Several cheap methods have been discussed in other threads.

[n3833v]

Make sure you get continuous duty relays for longevity.

John

[n2582d]

... Keep in-mind that landing/taxi lights are not continuous loads. They are intermittent, and for the short time that all FOUR lamps are powered ...roughly just the time on final approach and landing, ...any excessive load is supplied by the battery.
(Your generated electrical power only needs to exceed total continuous demands. Continuous loads should not exceed 80% of generated capacity.)

George, I have some question about what is considered a continuous load and what is considered an intermittent load. In the Cessna Service Letters that I've seen landing lights are always listed as an intermittent load. However, in AC43.13-1B, Paragraph 11-68, Step 3, (d.) intermittent operation is defined as a maximum of two minutes. Who uses their landing/taxi lights for only two minutes? It's interesting that the 170B prior to s/n 25372 uses a 14 ga. wire to power both the landing and the taxi light. If this were to be considered a continuous load it should have a 10 ga. wire. With a separate wire to each 100W bulb, as in the post s/n 25372 170's, 14 ga. wire is adequate for continuous load.

[Bruce Fenstermacher]

Who uses their landing/taxi lights for only two minutes?

Gary, to answer your question, I only use my landing lights for two minutes or less. In fact I probably use them for less than a minute just as I touch down and intermittently while I taxi. And only on those rare occasions when I find myself flying my 170 at night.

Why do I do this? Because my charging/electrical system is not designed to keep them on continuously which is pretty obvious to me viewing the amp meter showing a large negative current with them on.