blaplante

blaplante

Well Known Member
So, I had a stack of used Cessna style breakers laying on my bench when my local friend (& A/P) drops by. He strongly recommended that I not use them because they aren't pullable. Bummer! Well... really? Should every one of my CB's be pullable? OK, I get it for autopilot servos and trim, agreed. But for Nav lights? Radios?

What's the group opinion on when to use a pullable breaker?
 
Wouldn't non-pullable breakers have just about as much utiity as fuses, at a much higher weight and space penalty? Of course one could argue that the ability to easily reset a circuit in flight is handy, but if a circuit trips in flight I'd sure like to know the cause before I just pushed the breaker back in hoping for the best.

Not that my personal opinion was sought, but I'm going with pullable breakers for the circuits that may be important to disengage in flight, and fuses for everything else.
 
krw5927 said:
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Not that my personal opinion was sought, but I'm going with pullable breakers for the circuits that may be important to disengage in flight, and fuses for everything else.
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If the circuit is that important to be disengaged in flight, wouldn't a series switch be a better idea?
 
Current Cessna practice, etc.

In the recent Cessna 182 (2006) most of the breakers are not pullable. Also there is a notice from the FAA that cautions against using a pullable breaker as any kind of switch. It prohibits pulling a breaker for simulation of a systems failure! There's a couple messages there - one Cessna doesn't think that every circuit needs to have a pullable breaker, and two if the circuit needs a switch, then you need a switch!

Pretty much what I'm getting at is - if the circuit does have a switch, and the switch is nearby to the breaker, then why have a pullable breaker? [Landing light springs to mind] Now, I'm very familiar with stuck push button switches... anything with a push button switch, yes I do think a pullable breaker is important. Also - I am putting in real switches that are really rated for low voltage DC. [Otherwise you are asking for welded contacts.]
 
To a large degree my backround and current career is maintenance. I like to be able to turn systems off during ground maintenance. If I need power on the aircraft to trouble shoot a system I can turn off all the other unnecessary loads by pulling the associated breakers. This saves me from dragging out the GPU to keep everything lit up.

I know Cessna, Beech and other small aircraft manufactures do it this way.. but Boeing, Douglas and all the other "big stuff" I've been around all use pullable breakers, and it just makes more sense to me. I bet the non-pullable breakers are cheaper which is the most important thing to Cessna.
 
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The Carling rocker switches Cessna used for years will often melt on the higher load circuits. Leaves you staring at a melted switch and non-pullable breaker. Just being "certified" doesn't make it the best.
 
blaplante said:
?..Should every one of my CB's be pullable? OK, I get it for autopilot servos and trim, agreed. But for Nav lights? Radios?

What's the group opinion on when to use a pullable breaker?
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Yes and yes. We aren't flying a Cessna and sometimes we need to be able to disable certain things in certain order on the ground for software loads, testing, maintenance, etc... So pullable breakers or equivalent should be used all the way around. Walt and others are right here.

I'm not advocating their use as a switch, but there are several types of purpose built breaker switches as well if you desire that functionality. Don't cheap out on the important stuff - you can scrounge other stuff, but the non pullable breaker and the old cessna switches are both better left on Ebay.

Just my 2 cents as usual.

Cheers,
Stein
 
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Back when I was at your point, I realized that if I had an electrical problem in flight, I would want selectively turn things off and the best way to do that is at the power source. Thus, I used pullable breakers for everything.
 
Breakers

In my RV6 I used fuses for everything except Fuel Pump, ALT field, Flaps LSE ignition (used pullable breakers) thought I might like to give those a second try
Peter
 
N941WR said:
Back when I was at your point, I realized that if I had an electrical problem in flight, I would want selectively turn things off and the best way to do that is at the power source. Thus, I used pullable breakers for everything.
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So what items do you have that you want to load shed that don't have switches associated with them?

On our simpler planes, just switch them off...:)
 
Breakers - always a fascinating debate.

Buy them to pull 'em, not to reset 'em! Pulling a breaker when your radio starts smoking might save your bacon. Resetting a breaker which has popped might cook your bacon. :)
 
az_gila said:
So what items do you have that you want to load shed that don't have switches associated with them?

On our simpler planes, just switch them off...:)
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Switches fail and not everything has a switch. Also, the wire leading to an item might cause an issue.

The cost for the pullable breakers isn't significantly more than a non-pullable breaker, so why not use them?

dutchroll said:
Breakers - always a fascinating debate.

Buy them to pull 'em, not to reset 'em! Pulling a breaker when your radio starts smoking might save your bacon. Resetting a breaker which has popped might cook your bacon. :)
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Exactly!
 
N941WR said:
Switches fail and not everything has a switch. Also, the wire leading to an item might cause an issue.

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Exactly!
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Again, what in our simple planes does not have a switch?

If a wire from the breaker to an electrical items fails - "causes an issue"

1. It fails open - breaker does nothing, pulled or unpulled

2. Wire fails to positive - breaker does nothing, pulled or unpulled

3. Wire fails to ground - breaker pops anyway

4. Wire shorts to some signal wire - problem moves to some other, unknown unit. To find, pull every breaker on the panel one at a time while in flight?

If a breaker pops in flight, leave it and fault find on the ground. Decide wether to continue flight of land somewhere close first...:)
 
az_gila said:
Again, what in our simple planes does not have a switch?
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The dimmer circuit is always on, per the design.
The ANR power supplies that are hard wired into my system (They can be turned off by the Avionics Master.
The remote mounted transponder module. (and the Mode-C box, before I removed it for the panel upgrade. I think it was on its own power.)
Both AP servos.
And a few other things such as the light circuits for the instruments.


I agree with the rest of what you have written but there are times where in debugging things I have pulled the breakers so I know there no power going to an instrument.
 
Missing the point

You guys are all missing the point: All those pullable circuit breakers lined up in a row or two just LOOK COOL !! ;) :rolleyes:
 
For my system I have planned to use commercial, resetable (mainly for the trip indicator) non-pullable breakers. However, for any circuits that are not switched and may need to be pulled in an emergency I am using pullable breakers. Examples for pullable breakers are: Autopilot Servos, Trim Motors, Stall Warning circuit, Alt field... None of these need to be switched as part of normal operation, but if they fail-on using the breaker as a switch will suffice.
 
In real life more than once, I've seen where a typical clump of vans type cheapo round gages are paralleled on a 5 amp. One gage can have a complete drippy stinky meltdown without popping a breaker. If you can't pull it, you have to kill the bus.
 
switch breakers

You could also use switch/breakers. I agree with the Boeing philosophy regarding pullable breakers.
 
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