Landing Light CB

Nobody looks it up. The 4522 lamp is usually used in a swing-down lamp. The
swing down lamp has a motor to drive the lamp up or down.

The lamp is 12 volt, 250 watt, something the guesser at 9 amps (if for a 24
volt plane) would have realized if the system voltage of the plane had been
given, so the current draw for the lamp along is a nominal 20 amps.

If the motor circuit is not opened by the switch/relay built into the light,
the combination of the lamp current and the motor current will pop the breaker
every time, in a short time.

Yes, check the amps with a current meter, and please do not let the motor run
long in the test or it will burn out.

Neal

COUGARNFW wrote:
: Nobody looks it up. The 4522 lamp is usually used in a swing-down lamp. The
: swing down lamp has a motor to drive the lamp up or down.

: The lamp is 12 volt, 250 watt, something the guesser at 9 amps (if for a 24
: volt plane) would have realized if the system voltage of the plane had been
: given, so the current draw for the lamp along is a nominal 20 amps.

: If the motor circuit is not opened by the switch/relay built into the light,
: the combination of the lamp current and the motor current will pop the breaker
: every time, in a short time.

: Yes, check the amps with a current meter, and please do not let the motor run
: long in the test or it will burn out.

: Neal

Correct... I wouldn't even go around shaking the wire, etc, checking for
chafing until I measured the current. It's awfully easy to put in a bigger bulb "more
is better" and all. A friend's Comanche had had two landing lights installed that
were *both* 250W (14v plane). That would require a 40A breaker... rather insane.
Some boob had put the wrong bulb in it, because each was supposed to be a 90W bulb
(125W? I don't recall exactly, but not 250).

Disconnect the wire at the breaker, insert ammeter, and then read the current
with and without the engine running. The change from the bulb running on 12V/24V
(engine off) to 14V/28V (engine on) makes a significant difference in current. There
should be plenty of margin on the breaker (e.g. taking 10A on a 15A breaker).
Breakers do drift a bit with age and typically can blow easier than when new. If it
is the correct bulb and within spec of the breaker, THEN look for worn wires and/or
weak breaker. Replacing the wire as the first thing is silly and a lot of potentially
unnecesary work.

-Cory
--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering Ph.D. Graduate Student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

(COUGARNFW)
shared these priceless pearls of wisdom:

-Nobody looks it up. The 4522 lamp is usually used in a swing-down lamp. The
-swing down lamp has a motor to drive the lamp up or down.

Yes, well, when you look it up, you might want to use the right number. The
original poster said 4552, not 4522. If you had a clue about things, you would
know that no 172 ever made had a swing-lamp setup. That died with the C-170
series. Google on 4552 and see your error.


-
-The lamp is 12 volt, 250 watt, something the guesser at 9 amps (if for a 24
-volt plane) would have realized if the system voltage of the plane had been
-given, so the current draw for the lamp along is a nominal 20 amps.

No, the lamp is 28 volt, 250 watt, which calculates to a skosh below 9 amps.
The guesser didn't guess, he calculated.


-
-If the motor circuit is not opened by the switch/relay built into the light,
-the combination of the lamp current and the motor current will pop the breaker
-every time, in a short time.

There is no motor.

-
-Yes, check the amps with a current meter, and please do not let the motor run
-long in the test or it will burn out.

a. There is no motor.

b. If you check the current with an ammeter (sorry, John), you will blow the
fuse in the ammeter when the failure mode occurs. As somebody who knew what
they were saying commented, the best way is with a second lamp of the same
rating in series with the wire right at the breaker. Under "normal" conditions,
both lamps will light equally bright. Jiggle/wiggle/tap/thump the wire along
its whole length, and when the wing mounted light goes dark and the test light
brightens up, you've found the location of the sharp edge that is cutting
through the wire's insulation.

Having said that, in general it is easier to pull the old wire out and pull a
new wire into place, being sure that when you pull the new wire that it doesn't
go over the same sharp edge that killed the old wire. Yes, this is called
shotgun troubleshooting, but in a situation like this it can result in reduced
labor costs and headscratching to find the exact point along the wire where it
is being inadvertently grounded.

No, a loose ground AT THE LAMP will cause the wire and aluminum at the lamp to
get hot, but it won't pop the breaker. However, a loose or corroded connection
at the BREAKER will cause the breaker to heat up (I-squared R loss) and pop.
You might check the connections at the breaker before you go off on a tangent.

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

"Jim Weir" wrote in message
...
(COUGARNFW)
shared these priceless pearls of wisdom:

-Nobody looks it up. The 4522 lamp is usually used in a swing-down lamp.
The
-swing down lamp has a motor to drive the lamp up or down.

Yes, well, when you look it up, you might want to use the right number.
The
original poster said 4552, not 4522. If you had a clue about things, you
would
know that no 172 ever made had a swing-lamp setup. That died with the
C-170
series. Google on 4552 and see your error.



Well, Jim, I think you are being unfair to someone trying to be helpful, and
to be candid this guy Cougar from Sacramento has been very generous with his
expertise on the Stromberg carburetor and the files he has generated on it
and shared with some of us. If it weren't for these wonderful files (some
of which can be found at Ron Wanttaja's website), I wouldn't have been able
to make the neat little tool necessary to check and set the quirky float
level on a Stromberg. And yesterday after having spent a half day sweating
and changing out washers under the seat and checking and rechecking the
float level with gasoline in the bowl from a tube and a gallon of mogas
overhead, I thanked him every minute.

I was also grateful when the little C-85-powered taildragger's engine sprang
to life, purred, and flew gallantly aloft after I had finished doing a
bundle of wrenching and safety-wiring. And finally, thanks to Cougar
because it would have cost us over two weeks time and over $500 if we had
had to send that carburetor off for rebuild. And now we have a carb which
runs neither too rich nor too lean and doesn't leak gas all over the ramp.

So pick on someone who really deserves it, because he of all people, in his
kindness and generosity, should not be the butt of your caustic remarks.

You have been kind and generous with your technical advice. That is where
YOU shine, not at being mean.

Nobody looks it up. The 4522 lamp is usually used in a swing-down lamp.

The landing lamp is a GE 4522.

If I posted different, then it is my error and I appologize.
Hank

If your lamp is a 4522 then it is a PAR46 bulb, 13 volts 250 watts
5.75 inch dia with a rated life of 25 hours. 250w/13v = 19.23 amps
not counting the initial surge of about 5 times the rated current. A
20 amp breaker is too small to power this lamp.
You can get lamps in this same size glass housing from 35 to 450
watts.

A 4552 lamp is a 250 watt 28 volt PAR64 lamp , 8 inch dia which is the
number you listed first This lamp will draw about 9 amps which is
about correct for a 20 amp breaker.

I suspect someone installed the wrong lamp in your aircraft. Many
14volt 172's use a par36, 4509 lamp which is rated at 13 volts, 100
watts, 7.7amps.

You need to look up in the parts list for the aircraft the correct
part number of the lamp.

On 21 Aug 2004 23:36:14 GMT, (Hankal) wrote:

Nobody looks it up. The 4522 lamp is usually used in a swing-down lamp.

The landing lamp is a GE 4522.

If I posted different, then it is my error and I appologize.
Hank

I suspect someone installed the wrong lamp in your aircraft. Many
14volt 172's use a par36, 4509 lamp which is rated at 13 volts, 100
watts, 7.7amps.

You need to look up in the parts list for the aircraft the correct
part number of the lamp.

I did look at the parts manual and it states GE 4522 and the breaker is a 20
amp.
Would a 4509 or 4905 fit in the same housing?
Hank

A 4522 lamp is a PAR46 bulb, 13 volts 250 watts 290,000 cp
5.75 inch dia with a rated life of 25 hours. 250w/13v = 19.23 amps
If it runs at more than 13 volts it will draw more current and burn
out quicker.

A 20 amp breaker is running very close to its limit powering this
lamp. Since these breakers are thermal breakers a poor crimp or a
loose screw on the breaker terminals will cause extra heating and
cause the breaker to trip at lower than 20 amps. As these breakers age
they trip at lower than rated current due to oxide build up on the
internal contacts.

The next smaller wattage in the same lamp shell size, PAR 46, is a
4537. This is rated at 100 watts 13v, 200,000 cp

My 172M uses two 4905 lamps at 100 watts each which are PAR 36. These
are a smaller diameter lamp and will NOT fit in t PAR46 mount.

Look for hot crimps on the breaker wires and chafed wires going to the
lamp.

On 22 Aug 2004 21:59:44 GMT, (Hankal) wrote:

I suspect someone installed the wrong lamp in your aircraft. Many
14volt 172's use a par36, 4509 lamp which is rated at 13 volts, 100
watts, 7.7amps.

You need to look up in the parts list for the aircraft the correct
part number of the lamp.

I did look at the parts manual and it states GE 4522 and the breaker is a 20
amp.
Would a 4509 or 4905 fit in the same housing?
Hank

If he had simply stated that the bulb drew thus and such a current and was used
in a swing-down application, I would have simply stated that he was using the
wrong bulb number supplied by the original poster (who, it turns out, screwed up
and posted the wrong number to begin with).

Instead, he starts of with a particularly snotty "Nobody looks it up" when half
a dozen of us DID take the time to look up a rather obscure bulb and post our
findings.

He got a snotty answer back. End of story.

Jim



" jls"
shared these priceless pearls of wisdom:

-
-"Jim Weir" wrote in message
.. .
- (COUGARNFW)
- shared these priceless pearls of wisdom:
-
- -Nobody looks it up.

- Yes, well, when you look it up, you might want to use the right number.

-
-
-
-Well, Jim, I think you are being unfair to someone trying to be helpful


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

f he had simply stated that the bulb drew thus and such a current and was
used
in a swing-down application, I would have simply stated that he was using the
wrong bulb number

Ok here are the facts.
The plane is a 1973 Cessna 172 M.
The landing light is a 4522. 250 watt at 14 volts. By ohms law is draws 17.86
amps.
The Circuit Breaker Part number is S-1360-20---20 amp
This is from the equipment table on page 20-35
Either the Cessna book is wrong or the light should be of lower wattage or the
circuit breaker should be of a higher amperage.
Hank