Fuses for night VFR question

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4RNB

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4RNB
Hello,

So I am studying for my oral and checkride, figured I better get this one done right. I see requirements for spare fuses for night flight. I've done a few minutes of search related to this question (google and here) but did not find the answer.

Do the extra fuses need to be certified or can I go to my nearest auto parts store and buy extras?

Thank you.
 
4RNB said:
Hello,

So I am studying for my oral and checkride, figured I better get this one done right. I see requirements for spare fuses for night flight. I've done a few minutes of search related to this question (google and here) but did not find the answer.

Do the extra fuses need to be certified or can I go to my nearest auto parts store and buy extras?

Thank you.
Click to expand...

Im not sure certified but make sure they fit! I all the sudden had a random radio failure. I was on edge of replacing a radio- and found out the fuses were the right amps but wrong physical size due to the age of my plane. It looks like a Napa fuse but it’s a legacy physical size. It was an auto fuse from the era but was not the same as modern tube fuses..
 
If it fits, use it. Pretty sure there is no such thing as an “FAA Certified Fuse.”
 
Timbeck2 said:
Make sure the plane is question actually uses fuses instead of breakers. If its all breakers, fuses aren't required.
Click to expand...

I went round and round with the DPE on this point when I took my commercial. He stated that 91.205c(6) doesn’t say anything about “unless the plane doesn’t have pilot accessible fuses”. His firm belief was that unless one had a set of spare fuses, one was not legal to fly at night. My plane has no pilot accessible fuses, so I asked him what types of “spare” fuses I should carry. “As long as you have some fuses of any sort” was his response. Stupid. Fine, I said, Since there are no pilot accessible fuses in my plane, I’ll claim that the metal pocket clip on my ball point pen is also a fuse. At the right amperage, it will blow. Prove me wrong... Not a great oral.

I tried to make the argument that the set of fuses required was the null set, and that the three of each kind required was also 0 because the each kind required was equal to 0, but he didn’t go for it. I mean, I believe there are probably some fuses somewhere in the avionics, but none are accessible to me. Sheesh.

Just throwing this out there in case one runs into a DPE like this, or even worse, some bored FAA type who wants to ramp check you...

There used to be 23.1357(e) which was in conflict with his point, but it seems to have been removed:

[(e) For fuses identified as replaceable in flight--
(1) There must be one spare of each rating or 50 percent spare fuses of each rating, whichever is greater; and
(2) The spare fuse(s) must be readily accessible to any required pilot.]
 
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jimhorner said:
There used to be 23.1357(e) which was in conflict with his point, but it seems to have been removed:
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It wasn't removed, just relocated to AC 23-17 during the Part 23 rewrite as were most of the Part 23 regulations. However, 23.1357 is still applicable to those aircraft certified under it.

FYI: the key determination whether spare fuses are required is if that circuit is essential to safe flight or non-essential. If essential the fuse holder must be accessible to the pilot (in-flight) as well as 50% of the required spare fuses. We had several aircraft at the old day job that were fuse based and had a number of spare fuse holders mounted around the cockpit. And yes at the 135 level it was magnet for a PMI to ramp check and usually find at least one one aircraft short of the 50 rule which gave them a quick write-up so they could go to lunch. Most of the times the fuse simply vibrated out and we'd find them under the seat, etc.... unless that is a pilot needed some for a home project.:rolleyes:
 
If there are no fuses installed in the aircraft, 91.205(c)(6) is impossible to comply with, IMO. That DPE's "some fuses of any sort" doesn't make sense, because if the plane has fuses, I doubt that having incorrect fuses would qualify as carrying spares in the eyes of the FAA.

Also, if there are no fuses installed and you have no spare fuses, then you in fact do have a spare set of "no fuses." Makes just as much sense as carrying "some fuses of any sort"!
 
I have always been told if a fuse (or CB) blows, it did so for a reason. And replacing it in flight is not a good idea. Better to get on the ground and figure it out rather than replace/reset and have another, more interesting, problem.
 
I never checked out in aircraft with fuses. As for not replacing fuses in flight, doesn't always apply to cb's. Some check list items have you pulling and resetting cb's. Like a chip light. One thing I did when flying retract gear was to carry a spare bulb so I could get a real "three green." Its a hassle if you have to unscrew a functioning bulb to put it in the unlit socket. You also have to recycle the red bulb if its also unlit to be real anal. BTW, the specific bulbs called for have double filaments so one dim light will give you a heads up of an upcoming outage.
 
Timbeck2 said:
Make sure the plane is question actually uses fuses instead of breakers. If its all breakers, fuses aren't required.
Click to expand...
I suddenly panicked "damn, I've never carried extra fuses on my night flights!" then realized it's because the planes I've flown were all breakered

Are there any prolific post 70's GA planes that use fuses?
 
Tantalum said:
I suddenly panicked "damn, I've never carried extra fuses on my night flights!" then realized it's because the planes I've flown were all breakered

Are there any prolific post 70's GA planes that use fuses?
Click to expand...
Not sure if it's correlation or causation, but getting rid of fuses seems to coincide with the switch to 28v electrical systems. 1976-1979 Grumman Tiger (14v) seems to be the youngest plane I can think of off-hand with fuses.
 
asicer said:
Not sure if it's correlation or causation, but getting rid of fuses seems to coincide with the switch to 28v electrical systems. 1976-1979 Grumman Tiger (14v) seems to be the youngest plane I can think of off-hand with fuses.
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There are lots of Pipers with breakers and 12-volt batteries in them.
 
asicer said:
Not sure if it's correlation or causation, but getting rid of fuses seems to coincide with the switch to 28v electrical systems.
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In my experience, it had more to do with when/what/where the aircraft was certified. If at a later date they changed the electrical system requiring a re-cert then usually the fuses where replaced with CBs. Know of several aircraft, mainly helicopters at this point, that came off the factory line with fuses and 28v as late as 2016.
 
Huckster79 said:
Im not sure certified but make sure they fit! I all the sudden had a random radio failure. I was on edge of replacing a radio- and found out the fuses were the right amps but wrong physical size due to the age of my plane. It looks like a Napa fuse but it’s a legacy physical size. It was an auto fuse from the era but was not the same as modern tube fuses..
Click to expand...
That there. The common automotive fuse is an AGC; lots of old airplanes used the AGS, which is larger in diameter. If you use an AGC in an AGS fuseholder you end up with point contact that can get hot and fail the fuse. The fuse should go into the cap with some friction. That also prevents losing the fuse as you take the cap out.

https://www.mcfarlaneaviation.com/products/category/buss-fuses/
 
It seems that the homebuilders are leaning towards fuses over cb's. They are all free thinkers any way and know more than we do.
 
AggieMike88 said:
So... by his interpretation, Det cord counts
Click to expand...

Kinda wish you’d quoted a bit more of my post to show that those were the DPE’s words and not mine. I personally think his stance that one has to have some fuses in the plane even if there are no pilot accessible fuses is complete nonsense. Ridiculous.
 
Palmpilot said:
If there are no fuses installed in the aircraft, 91.205(c)(6) is impossible to comply with, IMO. That DPE's "some fuses of any sort" doesn't make sense, because if the plane has fuses, I doubt that having incorrect fuses would qualify as carrying spares in the eyes of the FAA.

Also, if there are no fuses installed and you have no spare fuses, then you in fact do have a spare set of "no fuses." Makes just as much sense as carrying "some fuses of any sort"!
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Yeah, I thought his point was nonsense. I have no pilot accessible fuses, so my set is the empty set. His advice was to go to Radio Shack and buy some fuses, any type. Total nonsense. I tried the 3 extras of zero and a complete set of none, but that didn’t work with him. He didn’t like my metal pen clip idea either. That exchange left me with the strong impression that he wasn’t testing my knowledge but was instead just trying to be nit-picking. Oh well, Not likely to need to ever do a ride with him in the future.
 
My Navion originally came with fuses but it was switched to circuit breakers long before I got to it.
 
jimhorner said:
I tried to make the argument that the set of fuses required was the null set
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LOL. A mathematical joke that uses wordplay.

Would have been appreciated by some DPE somewhere. But unfortunately your DPE was pretty much the opposite of a mathematician with a sense if humor.
 
Sounds like the DPE was also the opposite of having a brain. I may have said, let's discontinue the check ride right now and call the FSDO/OKC and chat about this.
 
"My point is with regards to the reverse: Can't think of any planes off-hand with 28v and fuses"


My 1979 172N is 28 volts and has CBs but there are two fuses... on the firewall, one for the clock and one for the master switch.

I will let the DPE get out and change them while I fly the plane
 
jimhorner said:
Kinda wish you’d quoted a bit more of my post to show that those were the DPE’s words and not mine. I personally think his stance that one has to have some fuses in the plane even if there are no pilot accessible fuses is complete nonsense. Ridiculous.
Click to expand...
Wellll..... I was going more for the chuckles versus picking nits....

Be glad C’Ron and some of the other rules know-it all’s have moved to other boards. This would get spun and twisted quickly into all sorts unusual attitudes and configurations.
 
Maxnr said:
It seems that the homebuilders are leaning towards fuses over cb's. They are all free thinkers any way and know more than we do.
Click to expand...
Fuses are cheaper and take up less room on a small panel. A lot of homebuilts don't fly at night. Trying to find the right fuse, or the fuse cap you dropped somewhere in the belly, while still flying the airplane, is no fun.
 
If you do have fuses and you have never taken them out before, it is wise to check them all at once as many were probably replaced at some time with 1/4” NAPA auto fuses as the AGS/4AC/ABS 9/32” diameter fuses are hard to find. Elliot Electronics seems to have a great selection, but I have had to find EBay and NOS ones before. Took a while to get them all replaced and have a decent set of spares on hand for all the different sizes.
https://www.elliottelectronicsupply...lty-types/1-4-x1-1-4-fast-acting-ceramic.html
 
Tantalum said:
I suddenly panicked "damn, I've never carried extra fuses on my night flights!" then realized it's because the planes I've flown were all breakered

Are there any prolific post 70's GA planes that use fuses?
Click to expand...
mine...sigh
 
I will take a fuse over a breaker almost any day. CBs can fail without out popping and remake and break the circuit. This not hypothetical. It happened to me but I could never catch the CB in the open mode long enough to find it until it finally opened at night and stayed open between Las Vegas and Phoenix. Also CBs will open at lower currents if they open enough times, again actually measured. A fuse is basically all or nothing. Also the FAA discourages resetting CBs if flight as this has resulted in inflight fires; a real problem.
 
Maxnr said:
It seems that the homebuilders are leaning towards fuses over cb's. They are all free thinkers any way and know more than we do.
Click to expand...

It’s mostly about saving money. I don’t get spending 60 to 90 grand building a plane and cheaping out to save a couple hundred on breakers.

My RV-8A was built with a mix of breakers and fuses. The avionics, alternator field and autopilot are on breakers. Everything else is on automotive blade fuses, which are behind a panel accessed through the forward baggage compartment.

I wouldn’t necessarily reset a breaker for lights, but if one blows I want to know about it.

Probably this year, the plane is getting the electrical system re-done to include all breakers.
 
Snowmass said:
I will take a fuse over a breaker almost any day. CBs can fail without out popping and remake and break the circuit. This not hypothetical. It happened to me but I could never catch the CB in the open mode long enough to find it until it finally opened at night and stayed open between Las Vegas and Phoenix. Also CBs will open at lower currents if they open enough times, again actually measured. A fuse is basically all or nothing. Also the FAA discourages resetting CBs if flight as this has resulted in inflight fires; a real problem.
Click to expand...

Yes, this it why new housing construction has gone with fuses in lieu of breaker panels.
 
jimhorner said:
I went round and round with the DPE on this point when I took my commercial. He stated that 91.205c(6) doesn’t say anything about “unless the plane doesn’t have pilot accessible fuses”.
Click to expand...

This is why we had grammar classes as part of our primary English learning. (We did have grammar, didn't we?) This is the one of the most bastardized sentences that I've seen.

One spare set of fuses, or three spare fuses of each kind required, that are accessible to the pilot in flight
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Reading this, the DPE is technically correct. The object of the sentence is "one spare set of fuses", with an apositive identifying that three spare fuses of each type is an equivalent. "That are accessible to the pilot in flight" in terms of grammar, must apply to the direct object, the set of fuses. Reading the language in the DPE's meaning, we can take this to extremes. If there is a fuse in your alternator (which you cannot replace anyway, even on a bench), you must carry a replacement fuse on board.

Obviously that is ridiculous, as is carrying fuses for things that aren't accessible in flight.

Of course, the alternative is to point out that if the DPE is right, every airplane in the country is grounded and he is out of a job.
 
Tantalum said:
I suddenly panicked "damn, I've never carried extra fuses on my night flights!" then realized it's because the planes I've flown were all breakered

Are there any prolific post 70's GA planes that use fuses?
Click to expand...
Pretty sure the DA-20 I learned in had fuses.
 
Maxnr said:
It seems that the homebuilders are leaning towards fuses over cb's. They are all free thinkers any way and know more than we do.
Click to expand...
I'm sure you've researched this like all of us homebuilders, or at least read "AeroElectric Connection" (the book that convinced many of us) before judging:rolleyes:.
 
Snowmass said:
I will take a fuse over a breaker almost any day. CBs can fail without out popping and remake and break the circuit. This not hypothetical. It happened to me but I could never catch the CB in the open mode long enough to find it until it finally opened at night and stayed open between Las Vegas and Phoenix. Also CBs will open at lower currents if they open enough times, again actually measured. A fuse is basically all or nothing. Also the FAA discourages resetting CBs if flight as this has resulted in inflight fires; a real problem.
Click to expand...
In old airplanes you could find old breaker technology. Modern breakers (like 40 or 50 years now) are the trip-free type that will not reset themselves.
 
A fuse is still much more reliable, smaller and vastly cheaper. CBs only make sense where you might plug in external devices and temporarily overload a circuit or for tracing down a short or other defect. This is why they are good in your home where you can plug in many devices. If a fuse blows the truth is just replacing it is is a bad idea without first correcting the underlying cause. The vast majority of aviation circuits are designed for and connected to a certain max load and will only pop a CB or burn out a fuse if there is a defect that must be corrected.
 
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