Another "What the Heck is This Thing"

[johnsunday]

Sorry I can't post a pix of the thing, I've already taped it up and tied it off.

My turn coordinator quit working so I got my 6'4" 230# frame under the instrument panel and found a couple of surprises.

One was that there is an electrical bus bar that connects all the fuses. The next was, there was a loose wire that I determined was the ground wire for the electric turn coordinator. The third was and is still a puzzle.

Hanging loosly, resting on the common bus bar was a small metal cylinder that someone had insulated by putting electrical tape around it...poorly....the tape was falling off. The small cylinder is approximately 1" long X 1/4-3/8" in diameter. There are two wires going into one end. The other end of the cylinder has a knurled cap. I unscrewed the cap, and to my amazement, the cap has a small light bulb inserted into it???? The bulb faces into the cylinder...The end cap presents a solid flat top to the cylinder...no possibility of light peeking out.

Anyone got any ideas on that one?

John

N2786C, Ratty ole Alaska Bush Plane

[johneeb]

John,
Sounds vaguely like the Cessna 170 Stall Warning light-horn.

[johnsunday]

John,

Thanks...now I'll have to see if there's a corresponding insertion point in the stall warning horn...

John

[johnsunday]

....but I still haven't a clue as to how light escapes the thing....

[Bruce Fenstermacher]

I was thinking the stall warning horn as well. Do you have one in you panel? Does it have a light the works.? Are you sure that nurled knob your describing isn't really a very very dark and dirty red lens?

[hilltop170]

I was going to guess at one time it was an instrument light of some sort, maybe a post light. But if it's totally solid metal, that could not be it. Could it have been some sort of heater, maybe to de-fog an instrument? Or maybe a resistor for some device that needs a little voltage drop? Is one wire going to ground?

[johnsunday]

Guys,

I have not traced the wiring. The wiring I was concerned about was to my Turn Coordinator. My other concern was that this metal cylinder was sitting on top of my copper buss bar.

Regarding could the cap be a really dirty red plastic thing....I don't think so...but it's a possibility....Looked steel to me....

Going back to the hangar tomorrow. Will take another look-see.

John

[johnsunday]

Bruce,

I do have a stall warning thingy in my panel. I've heard it go beep once before and it does have a center that looks like it may have a light in in, but I've never seen the light. Only time it ever went off it was in bright daylight.

John

[Bruce Fenstermacher]

Well it's probably not a stall warning. I reread you description and it seems to small for one anyway.

Why can't you post a picture? If it's easier send it to me directly at brucefenster@gmail(dot)com and I can post it.

[johnsunday]

Bruce,

Cause I've already taped the thing up and I'm not about to unwrap it. My shoulders don't fit on the floor under the panel....need a thin wiry guy for that and I'm neither....and...cause I've never been successful in posting a pix on this website....

John

[Bruce Fenstermacher]

Understandable John but I'll bet curiosity gets the better of you sooner or later. And when it does you can send the pic to me. I'm also wondering if there isn't a wiry guy locally who may be knowledgeable enough of aircraft components who might take a peak for you and venture a guess.

It sounds more like some type of light fixture like a post light though how the light escapes is not readily apparent. In any case best practice is probably not just taping it to protecting it from shorting to the bus bar and then letting it lay on the bus bar. What ever it is I would at least wire tie it off the bus bar.

[GAHorn]

The stall warning and the T&B in most 170's use the same C.B. or fuse. Some of the later installations do NOT present the light to the pilot but only the horn. It sounds as if someone has "cobbled" an repair to an existing unit, or added one to the present one.

[johnsunday]

I crawled up under the panel today and tied the mystery cylinder off to a remote wiring harness where it'll never get close to the buss bar again. I examined the rear of my stall warning horn and there's no place for the thing to fit into.

I quit. Don't know what it is, don't know what it does...only thing I know is it's under there, it ain't going to touch anything else, and I'm not going to worry about it anymore.

Thanks for trying to help!

John

N2786C, Ratty ole Alaska Bush Plane with an unknown doohickey cable tied out of the way behind the panel

[GAHorn]

Awwww....you're giving up too early! We sometimes NEED this sort of discussion!

It's an all-metal cylinder? Did you test the bulb? Some early smoke-detectors used a peanut-type bulb and a photo-electric cell, and when smoke diminished the view of the bulb (or the bulb burned out) the horn would blow. Is it a horn? that has failed?

[johnsunday]

LOL....

Yeah George, I'm giving up. I'm not flexible or small enough to twist around and trace what the wires are attached to.

When I first looked it (me being upside down and twisted), my first impression was it was a some kind of a wire connector. Then I noticed the end had knurling cut onto it. I tried unscrewing it. The top unscrewed. My initial reaction when I looked into the cylinder was that it was a fuse holder. Inside it was metal and had a shiny end inside, but there was no fuse. I looked at the inside of the cap and in a recessed pocket there was a very small peanut light bulb that faced the inside of the cylinder. In my opinion, the only way for light to get out of it was if one of the wires were actually an optical cable that went up to something in the panel. Another opinion I had was this bulb was probably not powered, but the cap performed the purpose of being a spare bulb holder.

Another thing I know in addition to the list in my previous post is, that I never used it before, I never missed it, and I'll never use it again.

And the first thing you know.....







Ole Jed's a millionaire...


John