Sounds strange to me

Sounds strange to me

I just had an A&P, who I do not know, recommend modifying how my landing light is installed. He suggested turning the filament vertical so that the light will last longer.  Reason: Has to do with mode of vibration.  I have a C173M with the landing light in the front of the cowling.  He wants to add another 20 minutes of work.

It sounds plausible, but ... Anyone have comments? 

(I'm not going to do it unless I here that others know something about it.  Is this guy credible?)

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Re: Sounds strange to me

Yes!  And let us know how it works out.  When I first got my 172, I was learning to fly and I was breaking a landing light filament every other time I made a hard landing.  It's true.  Up under the cowling they get enough abuse from the vibration but why in heaven's name they set it up so the filament is horizontal and in the worst possible orientation to absorb loads is beyond me.

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Re: Sounds strange to me

its true, but there is a catch, if the cowl shock mounts are stuffed it wont make two bobs worth of difference, so check them also, and the cowl buffer above the lamp which bumps on a plate below the alt/starter.

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Re: Sounds strange to me

How long do they usually last.  I've put over 500 hours Mostly day flights on the plane in the last two years.  I've only owned it for that time.  Doesn't seem like it's doing to bad the way it is?

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Re: Sounds strange to me

If you have 500 hours on them I don't think you have a problem.  Have you tried turning them on lately?

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Re: Sounds strange to me

Steve,

Yes, I tried to turn them on after landing and while taxing that same night..  The filanment in the bulb does appear burned out, but that was just looking in during the day. I'll find out if it's a loose wire or the switch when I replace it.

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Re: Sounds strange to me

The breaker was out but no obvious reason could be found.  (I really need to be better at finding the breakers that pop (operate).)  One wire looked like it could have a bare spot, but there are no signs of arcing. 

Its a 20 amp breaker with a 250 watt bulb.  At 12 volts that means it draws 20.8 amps, at 14 volts it will draw 17.9 amps.  So, in a moment of weakness (voltage drop (spike)) combined with an old breaker could result in this happening.

I'm not doing anything but puting tape on the wire and watching what happens.

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Re: Sounds strange to me

Barry, I too had a problem with the breaker popping. Turned out to be that the mechanic installed a bulb of  incorrect wattage. When the taxi light was on, all was well, however whan you lit the landing light, the combined wattage exceeded the circutry.

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Re: Sounds strange to me

JimJ,

Thanks for the info, but I only have one light for taxi and landing. I haven't looked as what else is on the circuit, but it gives me another path to try.

I haven't confirmed the problem, but when I have all electrical loads on the Alternator output breaker will operate (pop) some of the time.  I'm suspecting that it could be a related problem.  The voltage regulator was recently replaced.

I will try some things, like varying power with the landing light on and see if the problem reappears.

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Re: Sounds strange to me

Barry,
Is that 250w light the proper one?  It sounds like it's pushing the envelope of the breaker.
My 182 has two lights...landing & taxi...  I've noticed that one mounts 90º from the other.  I think it's the landing light that is horizontal.  I dont remember for sure.  It seems that the landing light burns out quicker than the landing light
There is a double rocker switch on the panel.  The taxi switch will turn on the only the taxi light.  The landing switch will turn both on.
The lights are both GE 4509.  The seem to put out a beam that is oval shaped.  Hence, the taxy light pattern is wider and the landing light pattern is narrower and "taller".  I guess to allow for some illumination on the runway at differrent angles during approach and the flair to land.
With the one light, rotating it 90º will likely give it a different pattern, which you may or may not prefer.
That 90º difference may expain why my landing light didn't last as long as the taxi light.  Especially, since the taxi light gets more use.
But then...maybe it was all by chance.
Michael

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Re: Sounds strange to me

Michael,

My single landing light looks like a circle to me not an ellipse.  I'm not buying the horizontal filament rational.  Mines been OK for so long and I've had my share of bumps.  The local A&P it and said that's the one Cessna spec'd out.  Also this is the first time the breaker operated on the landing light since I owned the plane.

The filament has so little mass and good flexibility that I wouldn't think the acceleration in any direction and within the limitations of the aircraft's structure would be enough to break it. (The wings would fall off before the element would break and then who cares about the bulb!)  Perhaps when its hot this may be different but certainly not while it's off.

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Re: Sounds strange to me

Barry,
I re read your posts.  It sounds like your landing light is doing just fine.  (If it ain't broke...don't fix it")  I certianly wouldn't pay a mechanic to rotate the thing.  10  min and a screwdriver would do that for free.  If the bulb is doing fine for you...dont waste the 10 minutes.
Anything on this end re your breaker popping would be pure speculation based on my imangination.  Your piece of tape probably took care of it.
blue skies!!
Michael

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Re: Sounds strange to me

Michael,

That's exactly my position.  I'm taking a wait and see attitude.

The A&P said something about having to cut this or that to turn the landing light mount.  Next time I have the cowling off I'll take a look for curiosity sake.

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Re: Sounds strange to me

Barry,  The correct 14v.  bulb is a GE 4509 which is a 100 watt bulb.  If your installed bulb is 250 watts, it is incorrect and the reason for the popped breaker.
  There was quite a bit of discussion at the "other" Cessna group about this issue which very authoritatively (whether correct or not, I'll leave to you) states that filament life can be increased by rotating the bulb within the holder.  These bulbs have a "locater-notch" or protusion molded into the outer rim at their rear surface.  This "locator" helps align the focus of the bulb.  (The filament is so designed in relation to it's reflector to throw a specific pattern of light on the runway surface.  The bulb is normally positioned by design with a horizontal filament, which casts a more vertically shaped beam onto the runway.  This "tall" beam illuminates more concrete length than width."
  Rotating the bulb to place the filament vertically allegedly reduces vibrations on the hot filament and increases it's life.  It also rotates the oblong beam into a horzontal polarization thereby illuminating more runway width than length.  (This can alter the amount of runway illuminated according to the CG the aircraft is loaded to versus it's approach speed, i.e., pitch angle.)
  Since the bulb has a "locator-notch" built into it, so does it's sheet-metal mount.  In order to rotate the bulb and still hold it securely, the mount must also be rotated,...or an additional "notch" must be cut into the mount to accomodate the bulb's "locator". 
  If you want to read the entire article by the "other" Cessna organization, give me your email address and I'll "loan" you my pdf file to read.

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Re: Sounds strange to me

P.S. ...By the way, anyone wishing to so alter their aircraft to accomodate a rotated landing light should be advised that without a basis of approval for making such a mod, ...it would be illegal.

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Re: Sounds strange to me

George, can you "loan" me the PDF as well?

   Dave

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Re: Sounds strange to me

Dave,
Maybe I can borrow the PDF when you're done...If it's OK with Geroge....  ;-)
Thanks
Michael

Re light  mods..I've had my 182 since '86...the landing/taxi lights are in the wing.  Ever since I got the plane, I though I would like to have a set of lights in the other wing too.  I may very well die a very old man still thinking it would be a neat thing to do.
Would anyone out there know if this has been done?  I would probably have to put in a bigger alt to accomodate them...It would probably get pretty darned pricey...
<Here I sit thinking about adding lights to my plane when just two weeks ago, I was out shooting some landings in a Citabria on the unlighted runway with the landing light off...hmmmm...??>

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Re: Sounds strange to me

I live in the "hill country" of central Texas on a 1500 ranch far from the city lights.  It's a very dark "hole" at night.  My paved runway that has lights is 1/2 mile from my hangar down an unlit grass runway.  I wanted to duplicate the left wing leading edge taxi/land lights on the right wing of my C-206 and had it priced turnkey  at $750.  Like Michael, I always wanted it, but never did.
If I were to do it, I'd use starter relay/solenoids to control the current from the main buss to the lamps, that way the original cockpit switches would still be operational, no necessity to re-placard, etc., and not be overloaded.  (I'd use the switches to control the relays, and I'd not concern myself with having to increase generator/alternator capacity because I'd placard the switch not to use all the lamps at the same time.  Heh-Heh.) ;Þ
Bob Dentice has an STC for this mod.  This e-mail address is being protected from spambots. You need JavaScript enabled to view it
Also, his website is: <http://home.earthlink.net/~n6d/>

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Re: Sounds strange to me

George,

Please send the PDF file. It's more for information.  I'm not going to do the modification.

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Re: Sounds strange to me

I forwarded the PDF to Barry.
I found it very interesting.

George,  was that $750 price the "out the door" price?
I was sorta thinkin' maybe, call the wreckin' yard for the mount, a hacksaw, some duct tape, piece of extention cord and a forged 337.... no?

I like the relay idea.  Seems like the actual hardware installation wouldn't be as hard or time consuming as the wireing...
I dunno....the whole idea does sound like a neat one!

Thanks for the pdf...

Michael

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Re: Sounds strange to me

It was an "out the door" price, but of course, you should get it priced wherever you intend to have the work performed.  The shop where I got the quote also operated a "bone-yard" and specialized in salvage and wreck-rebuilds, so they knew they already had the parts out in the yard.

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Re: Sounds strange to me

George:  The GE4509 is a par 36 size bulb and will not fit in light bracket.

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Re: Sounds strange to me

Barry "B"...I don't represent the GE4509 to fit every airplane....only the ones for which use that bulb.  My previous comment was to illustrate the wattage of the 4509 bulb, and that a 250 watt bulb used in lieu of a 4509 bulb would likely "pop" the breaker. 
It's important to use the correct PN bulb in every case.

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Re: Sounds strange to me

I realize that the ge4509 won't fit every plane, my frustration comes from not finding a par 46 13v 100w bulb for my 172M.

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Re: Sounds strange to me

The GE 4537 is a PAR 46 13 volt, 100 watt lamp with 2 screw terminals.

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