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

With tongue in cheek, and the Sweetest Wife, She has a couple of those brooms.. She, however, is not a pilot....
 
I have had circuit breakers fail intermittently or open at too low a current after popping but never a fuse. A fuse is all or nothing so I prefer a fuse for several reasons over a CB. And The FAA discourages resetting CBs without first correcting the underlying problem. Note that modern hi-tech cars use a lot more fuses than CBs. However, I have temporarily clipped a CB while troubleshooting the cause of the circuit overload.
 
Snowmass said:
I have had circuit breakers fail intermittently or open at too low a current after popping but never a fuse. A fuse is all or nothing so I prefer a fuse for several reasons over a CB. And The FAA discourages resetting CBs without first correcting the underlying problem. Note that modern hi-tech cars use a lot more fuses than CBs. However, I have temporarily clipped a CB while troubleshooting the cause of the circuit overload.
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A fuse as old as the average CB will fail, too. Both CBs and fuses are subject to oxidation, which creates resistance and causes heating that fools the device into opening the circuit. With a fuse, someone just puts a new one in and everything's fine because it's a new fuse, without any corrosion bewteen the tiny fuse strip and the end caps. Someone else resets a popped breaker, but the oxidized contacts are still there to cause further trouble.

Cars uses fuses because space is limited and fuses are ways smaller and way cheaper. And how often does a fuse fail in a car? Not often for legitimate reasons, and the construction of modern fuses means that there are no interfaces to oxidize in the new fuse. The fuse strip is part of the tangs, not a separate part pinched between the cap and glass tube.
 
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Dan Thomas said:
A Both CBs and fuses are subject to oxidation,
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Yes, and as you have noted, modern encapsulated fuses do NOT oxidize but even modern circuit breakers that are not encapsulated (and they cannot be by design) will oxidize. When they break, and when they are reset, the miniature arc between the contact faces wears a new face over the oxide layer and then they are good for another cycle. Resetting the breaker is sort of like putting a new one in. If it KEEPS breaking, then we've got a problem. Single break, not a problem.

JIm
 
I know that CBs may carry less current after opening several times since I have had this happen and can be an ordeal to replace but a fuse is extremely easy to replace and you get a brand new part for pennies. Also a lot cheaper, lighter and more compact.
 
Snowmass said:
I know that CBs may carry less current after opening several times since I have had this happen and can be an ordeal to replace but a fuse is extremely easy to replace and you get a brand new part for pennies. Also a lot cheaper, lighter and more compact.
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A circuit breaker is far more convenient to reset, and yes it should be replaced after the offending component that tripped it enough to justify it, is remedied.

I just had a Client equate the cost of a repair I assisted him with to "a tank of gas", he was elated.

Maintaining a breaker under normal conditions should cost less than a tank of gas over the life of the aircraft. Worth the convenience?

I loved skiing the Big Burn at Snowmass.
 
Snowmass said:
I know that CBs may carry less current after opening several times since I have had this happen and can be an ordeal to replace but a fuse is extremely easy to replace and you get a brand new part for pennies. Also a lot cheaper, lighter and more compact.
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A fuse can be a real pain when night flying. Fumbling with it in the dark and looking for the spare fuse right when you're trying to talk to ATC--or on an IMC approach--is not a good deal at all. I've found fuseholder caps under the floorboards; those tells a story all their own. Stuff like this is why airplanes got breakers.
 
Snowmass said:
Are you aware that the FAA strongly opposes resetting a CB in the air for very good reasons?
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So tell me what the difference is between resetting a breaker and replacing the fuse. To the circuit it makes no difference at all.
 
None. So do NOT do either so the in flight convenience of a CB reset is meaningless. But fuses are inherently more reliable. I have had an intermittent CB which I could never catch in the open state until one night when it finally stayed open. I never in 8000 flight hours had an intermittent fuse.
 
Snowmass said:
None. So do NOT do either so the in flight convenience of a CB reset is meaningless. But fuses are inherently more reliable. I have had an intermittent CB which I could never catch in the open state until one night when it finally stayed open. I never in 8000 flight hours had an intermittent fuse.
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As a mechanic I did not find that fuses were inherently more reliable. I found old fuses that didn't work and they hadn't blown. They were oxidized, and the fuseholder itself oxidizes in the cap and rear contact. I also found fuses of larger capacity installed in fuseholders because the right fuse wasn't available or it was impossible to read the rating in the dark while flying the airplane. THAT is dangerous, and you can't do that with a breaker.

Breakers sometimes pop due to an intermittent overload (someone has added something to the airplane and instead of installing a separate breaker they just connect it to some existing breaker) or because the breaker is old and getting oxidation on its contacts that causes resistance and more heating than the bimetal actuation mechanism is designed for. If I was landing at night and the landing light breaker popped, I'd reset it after a short cooldown. If there really is a short somewhere it will pop again anyway. If I was on an IFR approach to minimums and the ILS breaker popped, you bet I'd reset it ASAP. One can get stupid about FAA recommendations and kill oneself.

Can you cite the FAA source that strongly opposes breaker resetting in flight?
 
Very well stated, I've seen plenty of fuses fail without blowing.

I've collected enough gently used pullable aircraft breakers to replace the fuse holders in my offshore boat, now if I just had the time...
 
I am 100% certain that the FAA discourages resetting CBs but I did not keep the reference and it's your death from an in flight fire not mine. However for a serious $1000 wager I am certain i can find the source. Tell me how a fuse fails without blowing. Do you men the circuit opens? Then might might it be a junk fuse holder not the fuse? It's likely I have more experience with both than either of you.

The most interesting thing about forums is not any info but how most contributors oppose original or unconventional thinking. Which further increase my superiority complex. Keep it up.
 
Dan Thomas said:
Stuff like this is why airplanes got breakers.
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Not to mention a popped CB is obvious over a blown fuse plus the requirement to keep X-number of spare fuses on board to be legal. I don't miss fused airplane/helicopter electrical systems at all especially when trying to troubleshoot/isolate a problem or chasing a parasitic battery drain.
 
Bell206 said:
Not to mention a popped CB is obvious over a blown fuse plus the requirement to keep X-number of spare fuses on board to be legal. I don't miss fused airplane/helicopter electrical systems at all especially when trying to troubleshoot/isolate a problem or chasing a parasitic battery drain.
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This is why I use a CB temporarily clipped in while tracing the cause of the blown fuse. CBs are ideal on circuits with variable loads such as house wiring because you simply reduce the load and reset. If fixed load circuit fails it is highly probable that after resetting the CB it will quickly pop until you cure the underlying problem. My Cessna does not have CBs that can be pulled open and it is now recommended that all CBs be exercised annually because the are so subject to corrosion and other problems. My generator CB would fail and then work and then fail randomly until total failure (night flight) after about six months. It never popped. Of course it was then easy to diagnose. Fuses are unlikely to randomly reset/repair themselves.

And I hope that carrying a few, very in expensive, spare fuses isn't that difficult for a licensed pilot to deal with. And as to which fuse blew good engineering would have a separate fuse for each item so it would be obvious. Fuses are so small that , for example, you would have one for each radio so that if radio (1) failed radios (2) an (3) would be unaffected. This is how my radios are wired.

But this is all so entertaining.
 
Snowmass said:
But this is all so entertaining.
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I guess for you fuses are good. But having worked on aircraft with over 75 fused circuits spread over 6 different fuse panels I prefer CBs. And in these cases is was more than a "few" spare fuses to meet the legal requirements. While CBs and fuses do the same thing, in my experience, CBs offer reduced upkeep and better reliability. As such I only use CBs when installing additional equipment or alterations. But I think you'll find it's more an industry trend toward CBs over fuses as there are a lot more STCs/alterations to replace fuses with CBs rather than the opposite. But hey, to each their own.
 
Do you prefer CBs because of scientific analysis or because it's what everybody else thinks? Modern cars are far more hi-tech than most GA airplanes and you will see banks and banks of fuses but few CBs. The best possible wiring would be to have a separate fuse for each device so that the failure of one device would not disable any other. You would instantly know which fuse blew by the device that failed. Rarely would a single device constitute an emergency and, in any case, it is doubtful that resetting a CB or replacing a fuse would help since it would be a defective device that blew the fuse and said device isn't going to fix itself.
 
Snowmass said:
Do you prefer CBs because of scientific analysis or because it's what everybody else thinks?
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Neither. I prefer CBs based on 30+ years of maintaining helicopters and airplanes. And you?
Snowmass said:
Modern cars....
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No comparison. Aircraft are designed, whether old or new, to a completely different standard than cars or trucks. Perhaps give the design engineers at Bell, Boeing, Piper, or Cessna a call as to why there are not more fuses in newer aircraft? You might be surprised by their answers.;)
 
Dan Thomas said:
As a mechanic I did not find that fuses were inherently more reliable. I found old fuses that didn't work and they hadn't blown. They were oxidized, and the fuseholder itself oxidizes in the cap and rear contact. I also found fuses of larger capacity installed in fuseholders because the right fuse wasn't available or it was impossible to read the rating in the dark while flying the airplane. THAT is dangerous, and you can't do that with a breaker.

Breakers sometimes pop due to an intermittent overload (someone has added something to the airplane and instead of installing a separate breaker they just connect it to some existing breaker) or because the breaker is old and getting oxidation on its contacts that causes resistance and more heating than the bimetal actuation mechanism is designed for. If I was landing at night and the landing light breaker popped, I'd reset it after a short cooldown. If there really is a short somewhere it will pop again anyway. If I was on an IFR approach to minimums and the ILS breaker popped, you bet I'd reset it ASAP. One can get stupid about FAA recommendations and kill oneself.

Can you cite the FAA source that strongly opposes breaker resetting in flight?
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Why does it have to be endorsed by the FAA to be a good idea. Personally I think the FAA is rather incompetent

I’m an avid supporter of the never reset in flight camp but do you really think that applies to every circumstance you could dream up? Is this what people call a straw man argument? Honest question. Never have heard that before reading it on here.
 
The FAA is more concerned with in flight fires and feel that resetting keeps adding heat to a dangerous level on every reset. There was a recent small GA fatal accident due to this resetting starting a fire beyond the instrument panel and smoke filling the cockpit. Every pilot should be capable of flying with one electric device not functioning.

I would not be the least bit surprised by the the reasons why engineers at Bell, etc. use CBs. It's called following the herd. And I already knew what the majority of the responses would be on this forum. Why question what everybody "knows" to be true. But I question everything. Obviously I was not popular in church. (Glad Torquemada is dead.)

Thanks for the entertainment.
 
Why does it have to be endorsed by the FAA to be a good idea. Personally I think the FAA is rather incompetent



I remember a time when an FAA guy would nearly faint when he would see how far we were into a project, they would step away with very few questions.

I learned to stage it for the shock factor!

I enjoy looking back at my career rather than forward because the same mentality exists today, only they want to tell far more knowledgeable people how they should be doing their jobs.

I got my first soldering iron in 1965, I was 6. I have built multiple motorcycles, cars, boats, airplanes, discotechs(a rather weak time in my life), houses, avionics shops, RST aircraft radios, etc... I've sat at the bench with factory training programs under my belt since the mid 1980's specializing in autoflight systems. I even had to build a stupid computer in college.

Granted, I'm a bit wet behind the ears here, but I'm still replacing all of the fuse holders in my offshore boat with pullable aircraft breakers.

When I get the time.

I've just popped some more corn...
 
Snowmass said:
The FAA is more concerned with in flight fires and feel that resetting keeps adding heat to a dangerous level on every reset. There was a recent small GA fatal accident due to this resetting starting a fire beyond the instrument panel and smoke filling the cockpit. Every pilot should be capable of flying with one electric device not functioning.

I would not be the least bit surprised by the the reasons why engineers at Bell, etc. use CBs. It's called following the herd. And I already knew what the majority of the responses would be on this forum. Why question what everybody "knows" to be true. But I question everything. Obviously I was not popular in church. (Glad Torquemada is dead.)

Thanks for the entertainment.
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Actually I feel the information given below is more relevant. He know electrical equipment
weirdjim said:
Yes, and as you have noted, modern encapsulated fuses do NOT oxidize but even modern circuit breakers that are not encapsulated (and they cannot be by design) will oxidize. When they break, and when they are reset, the miniature arc between the contact faces wears a new face over the oxide layer and then they are good for another cycle. Resetting the breaker is sort of like putting a new one in. If it KEEPS breaking, then we've got a problem. Single break, not a problem.

JIm
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Jim's remarks are generally consistent with the FAA guidance:
https://www.faasafety.gov/files/notices/2009/Dec/SAIB_CE-10-11.pdf
 
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