17 year old Pilot in need of electrical advice on 172 Please read

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Kylan Luke Bunch

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Kylan Bunch
Hello All,

My name is Kylan Bunch. I am a 17 year old pilot and a senior at Hayesville High School. I am in need of some advice pertaining my 1957 Cessna 172.

First, a little background of how I got where I am today. When i was 14 years old my HS started an aviation class. I joined and was super excited. My mother was a FA for 35 years so I had grown up in the airline life style. After taking my first flight, I knew this was exactly what I wanted to do when I grew up and I still do.
As I progressed in my flying career my family and the instructor thought it would be a good idea for my family to buy a small 172 for me to train in till the end of HS. Everything was going great until March 28th, 2018 (Yes I have been dealing with this problem for a longggg time). I was flying over Birmingham, AL when a fuse blew. When i got back to the ground I replaced the fuse and figured everything would be fine. Little did I know, it would not. The loss of radios and electrics that I experienced from a blown fuse persisted until this present day.
To make this long story short, I have replaced the once fuses with new circuit breakers, I have converted from a 20 amp generator to a 50 amp alternator kit (new regulator was included), put in a new battery and a new ground from the engine to the airframe.
After the Alternator conversion was finished it worked great for a couple flights where I manged to get most of my CFI hours but, while I was taking a night XC with my CFI the problem surfaced again. radios cut out, lost Communications with ATC and would not have been able to turn on the runway lights had I not carried a handheld. When the problem arises the "Alt inop" light is activated and the only breaker that pops now is the "alt output". I have been told it could possibly be a loose connection or something on the breaker or alt conversion came loose since my few weeks of good flying right after the conversion was put in.

Please advise if you have any suggestions or have had this problem before.
Thank you in advance,
Kylan Bunch
 
Tell a mechanic which breaker/fuse keeps failing, trace wires connected to the circuit and find shorts. A 1957 Cessna will sure have plenty of deteriorated wiring to look at.

I'd also look for a rotating beacon, if by odd chance its connected to the same circuit it may be the problem.
 
I'd be looking for a chafed wire somewhere between the alternator output and the main bus causing an intermittent short to ground. Although this wiring should have been replaced along with the alternator installation, was it?
 
What did your A&P have to say as you were doing the work? Did he/she have any idea where the problem may lie?

In general, fuses and breakers are there to protect the wiring, and the rating of the fuses/breakers are based upon the amount of current the wire after them is capable of carrying safely without melting or causing a fire. Just a word of caution... and I'm not by any means an authority of any of this stuff, so do NOT take my word as gospel on any of this... but when you did (I'm hoping with an A&P) the alternator and breaker upgrades, are you sure you kept the values of the breakers appropriate for the wiring they are protecting? I'm guessing that you may have gotten a couple hours of flight in without "problems" because of a higher-rated breaker where the fuse used to blow... and now even THAT breaker is tripping, which could mean a VERY unsafe condition if the wiring past it is undersized for that breaker.

To figure out what is tripping the breaker, you have to know what circuit(s) is(are) after that breaker, then check the draw with an ammeter as you turn on each device in that circuit, making sure each device draws no more than it's supposed to based upon its specs. Make sure the wiring in the circuit is large enough gauge to support the current it's supposed to be carrying and that the breaker is not sized larger than the wiring's capability. A lot of aircraft avionics wiring is 24g, but the power leads often need to be at least 22g (or more depending upon length of run and the device's requirements)... and much more when it comes to the alternator, starter, and battery leads obviously.

Don't screw around with this. In a car, you're left by the side of the road at worst while you watch your car burn up. In a plane... well.... it can get a LOT worse than that. I'm a DIY kind of guy myself, but you NEED to have an A&P or avionics guy at your side with this one... both because it's required by the FAA, and because it's the smart thing to do.
 
If you are popping CBs and fuses you have an intermittent short somewhere, i would think. Need to trace the wiring served by the CB.
 
+1 on the old wiring. We're talking wires that were installed 62 years ago, and the insulation they used in those days was rubber covered by fabric. The rubber hardens and cracks with age. The fabric rots away and lets bits of rubber fall off. The wires can chafe against structure at numerous places, but they can also chafe against each other in wire bundles.

When I restored my '51 International pickup I pulled out all the old wiring. It was toast. Rewired the whole truck and never had any issues. A 172 isn't a complicated airplane and rewiring it wouldn't be all that big a job. I presume the avionics have been replaced long ago and their wiring was likely replaced then, too. The rest of it--the charging circuit, lights, fuel gauges and senders, beacon--probably all have ancient wiring.

Edit: If the P-leads are old, get them changed soon. If one of those shorts you lose a magneto. If both of them short the engine quits, and your own shorts suffer somewhat...

Old wiring has other problems, too. The wire itself oxidizes and resistance builds inside the crimp connectors, causing heating and eventual failure. The contacts inside old switches and contactors oxidize, and burn due to the arc generated when an inductive load is switched off. The ancient master switch in your airplane is GOING to cause trouble unless it's been replaced, and they are now hard to find and harder to get at in the panel. They had sliding contacts lubricated by grease, and the grease ages and hardens and eventually prevents contact.

Old airplanes are fun and expensive. Sometimes it's much cheaper in the long run to buy a much newer airplane and be done with most of the age-related issues. I once worked on a '68 that ended up costing the owner nearly as much as the 2002 (IIRC) low-time 172 we had for sale.
 
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IA course last winter had an eye-opening talk on the state of, aging of, GA wiring. Abominable.
Would not be surprised to see a push to life-limit the entire wiring system of older airplanes!
 
Let's turn it into a learning experience. Kid, your weekends are shot for the next year. Find you a grizzled old mechanic that is a crackerjack electrics guy -- we are around, you just have to find us -- try your local EAA chapter for leads. Then prepare to get your hands dirty doing what (s)he tells you to do and then letting them inspect it when you are done. It's gonna cost you $500 or so in wire, but get used to spending money on airplanes. Then, three years of this and you get to sit for your A&P just about the same time you sit for your commercial/instrument. But you will know your wiring (and probably a lot about your airplane) when you are done.

BTW, topnotch electrical, electronic, and avionics engineers make as much, if not more, than some airline flight deck personnel and they don't have to spend twenty years moving from right to left seat, sweat a serious medical every six months, they get a hell of a good retirement package, and spend weekends at home. Plus, they get to know state of the art airplanes ten years before you get to fly them.

Jim
 
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What size is the "alt output" fuse or breaker? Is it rated for the amount of amps that is being demanded? Was a load analysis done for the alternator kit install? Was the alternator feed to the bus checked for condition and if it is an appropriate size for the load?

The below website has some good information on this subject. I haven't dealt with him, but he seems to know his stuff.

https://pinpointharnessing.com/

Look after this old girl. I have always had a soft spot for broom tails!
 
[QUOTE="Dan Thomas, post: 2790135, member: 4817]...

Edit: If the P-leads are old, get them changed soon. If one of those shorts you lose a magneto. If both of them short the engine quits, and your own shorts suffer somewhat...
[/QUOTE]

Not how the P-lead functions. Lose the p-lead and the magnetos are hot. They ground the magnetos when the ignition switch is off.
 
Witmo said:
[QUOTE="Dan Thomas, post: 2790135, member: 4817]...

Edit: If the P-leads are old, get them changed soon. If one of those shorts you lose a magneto. If both of them short the engine quits, and your own shorts suffer somewhat...


Not how the P-lead functions. Lose the p-lead and the magnetos are hot. They ground the magnetos when the ignition switch is off.
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I think you missed his point. If the wires short then the magneto is grounded and the engine shuts off just like turning the key.
 
Salty said:
I think you missed his point. If the wires short then the magneto is grounded and the engine shuts off just like turning the key.
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You missed the point. The p-leads go to ground. How do you short a ground?
 
Witmo said:
You missed the point. The p-leads go to ground. How do you short a ground?
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By having a bare mag wire accidentally touch ground.
 
Witmo said:
You missed the point. The p-leads go to ground. How do you short a ground?
Click to expand...

When the P-lead is grounded, it kills the magneto. A worn P-lead can expose the conductor which can touch ground and kill the magneto.

As an aircraft mechanic, I have found some badly worn P-leads. Sometimes the insulation can get so bad that the internal conductor contacts the shielding, which is grounded.
 
Now another SEWAG. The ALT-OUTPUT breaker is popping. That's the hewmongous 50 or so amp breaker directly from the alternator output to the system. That's a lot of current to pop. And, the kid said that his radios almost immediately dropped out, indicating that the battery isn't holding anything up. What can take a 50 amp jolt without catching fire? A shorted battery certainly will do that, and if that new alternator has been pumping that many amps into the battery it certainly has buckled plates by now. I say put the battery on an analyzer and see about its condition.

Jim
 
weirdjim said:
That makes absolutely no sense to me. What is the connection between brooms and corn? And what looks like corn, the rudder or the vertical stabilizer?

Jim
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I think I get it ... "corn broom" ... the tail looks (kinda) like an old corn broom, with the rudder looking like the end of the broom, horizontally, (imaginary) handle facing forward

41oaWbwLLoL._SL500_AC_SS350_.jpg
 
Capt. Geoffrey Thorpe said:
P-lead goes to the mag switch. The mag switch goes to ground. If the P-lead goes to ground, you ain't gonna get much noise out of that big aluminum thing up front.
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I forgot that little detail. I stand corrected. Thanks.
 
gkainz said:
I think I get it ... "corn broom" ... the tail looks (kinda) like an old corn broom, with the rudder looking like the end of the broom, horizontally, (imaginary) handle facing forward
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That is about the most OBSCURE reference I've ever seen. First of all, why would you need a broom to sweep off corn? Second of all, the image you've published shows the bristles coming off at an angle, not parallel.

Makes no sense.

Jim, who flies a 182A "broomtail" I guess.
 
weirdjim said:
That is about the most OBSCURE reference I've ever seen. First of all, why would you need a broom to sweep off corn? Second of all, the image you've published shows the bristles coming off at an angle, not parallel.
Click to expand...

After a few frosty rockets it might make more sense. Maybe not.

weirdjim said:
Jim, who flies a 182A "broomtail" I guess.
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Awesome. My 150E is the last of them. :)
 
Corn brooms aside, I wonder how the young man is making out. Hopefully he isn't still flying it (the aircraft)!
 
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I rather dislike people coming into a conversation asking for advice and then not following through on any replies. Whether they be seventeen or seventy. Shows a lack of basic courtesy. Which is quite common amongst the junior set these days.

Jim
 
weirdjim said:
I rather dislike people coming into a conversation asking for advice and then not following through on any replies. Whether they be seventeen or seventy. Shows a lack of basic courtesy. Which is quite common amongst the junior set these days.

Jim
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Well, the OP hasn’t stuck around either.
 
I've gotten used to it.
 
I restored a '56 172 and flew it all over Colorado and the four corners many years ago. I've chased things like this with that one and several others. 48.jpg I think I could probably get this figured out pretty quick
 
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JAWS said:
Corn brooms aside, I wonder how the young man is making out. Hopefully he isn't still flying it (the aircraft)!
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Kylan reports he discovered the connections to the 50 amp alternator breaker were loose, causing resistance heating, that was tripping the breaker. Screws tightened, other nearby wiring tidied up... several trouble-free flights now. I guess he was scared off by city folks here who had never seen a poor man's broom made of corn stalks...
 
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Thank you very much for following-up, @PaulMillner !

Tell Kylan to come on back and share his progress with us - it's a source of comfort to see a young'un coming into the fold, especially one who isn't just a button-pusher.
 
PaulMillner said:
Kylan reports he discovered the connections to the 50 amp alternator breaker were loose, causing resistance hating, that was tripping the breaker. Screws tightened, other nearby wiring tidied up... several trouble-free flights now. I guess he was scared off by city folks here who had never seen a poor man's broom made of corn stalks...
Click to expand...


I would advise a careful inspection of the connectors that were loose, and replace the breaker. The times I've seen this, even some of the wiring needed to be replaced due to the heat generated by the loose connections. It may work fine now but if any connector or wire that got hot enough, it has been compromised by the process of annealing. The breaker should be replaced for age alone, much less the loose connection heat. You are not out of the woods yet.

Here is a link where we found an issue in a 340A that could have gone real bad.

http://fly.twincessna.org/forum/viewtopic.php?f=4&t=7260&p=58383&hilit=hall+of+flame#p58383

I would be more than happy to donate my time here, I had a 56', and even a broom like that! 616 822 1999 webairconsulting.com
 
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