Replacing All Cockpit Circuit Breakers w/ Same Ratings, Different Style

Pete Lehmann

Pete Lehmann

Filing Flight Plan
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Sep 6, 2021
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Southern Maryland
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Display name:
Tomahawk- Pete
Quick and easy question:

As the owner/operator of my PA38-112 Piper Tomahawk, as well as a certified A&P, can I replace all the white circuit breakers in the cockpit which reset flush and change them out for the black type which can be pulled in flight? Would that take a 337, or are they considered a consumable?

I'm not sure who thought that inhibiting the pilots from being able to pull any appliance off the bus was somehow a good thing. If I'm flying at my favorite cruising altitudes, 7,500' or 8,500' MSL and start to smell electronic circuit smoke, I have 2 awful options I would need to choose from, and do so quickly. I either inform New York Approach what's going on and start an extremely aggressive emergency descent, or I shut the avionics switch off, which takes every single thing I actually really would need, and go find an airport to land.

There's one step left for them and it's the same thing for both. Really really hope it doesn't get worse.

I bet continuing my flight while conducting the simplistic troubleshooting process of pulling each breaker observe, no change, reset and go to the next. Hopefully there would be some evidence which would suggest a likely area the smoke seems to be originating from, or some radio or appliance started exhibiting unusual characteristics.

In the Army, as a Blackhawk crew chief, we were required to train on this process in and were tested before we were qualified to be a member of the crew.

Also, if anyone has a convenient source for these breakers, I'd very much appreciate you passing that along to me.

Thanks Yo!!
 
Can’t give you a definitive answer, but my PA28 has both styles, due to various upgrades over the years.
 
Pete Lehmann said:
can I replace all the white circuit breakers in the cockpit which reset flush and change them out for the black type which can be pulled in flight? Would that take a 337, or are they considered a consumable?
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As long as you dont "redesign" the electrical system replacing CBs with a different style is a minor alteration which you need to sign off under your AP.
Pete Lehmann said:
convenient source for these breakers,
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Depending on quantity Aircraft Spruce usually has better price. If you need a high quantity check at your local commercial electric supply vender to see if they can order at a discount. A second option is to go used from salvage yards. Klixon is the brand I usually look for new/used with Wood a 2nd brand on the used side.

Are you a practicing A&P or picked up the certificate when you left the army?
 
Welcome to PoA, where do you hail from?
 
Pete Lehmann said:
In the Army, as a Blackhawk crew chief, we were required to train on this process in and were tested before we were qualified to be a member of the crew.
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The average pilot has no such training. He's just told to shut the master off and good luck. It's too bad, because even if the pilot never needs to do it, it increases his/her understanding of the aircraft's systems and makes him/her a smarter owner and pilot.
 
Obviously I prefer switch breakers for loads that get turned on and off regularly. The body of the breakers is identical for toggle and push-pull. All my breakers are Tyco.
 
When they built you Tomahawk Piper probably saved a nickel a breaker by not putting in push pulls.
 
I just ordered replacements on my 182.
$750ish with install.

Panel is already out, so labor was cheap.

I like knowing I can isolate a problem circuit at altitude.
 
What is shop rate? I could swear I was paying 90 just a year or two ago and now it’s 130. At least they answer. Every new place I call never responds.

Mid Atlantic region
 
Bell206 said:
As long as you dont "redesign" the electrical system replacing CBs with a different style is a minor alteration which you need to sign off under your AP.

Depending on quantity Aircraft Spruce usually has better price. If you need a high quantity check at your local commercial electric supply vender to see if they can order at a discount. A second option is to go used from salvage yards. Klixon is the brand I usually look for new/used with Wood a 2nd brand on the used side.

Are you a practicing A&P or picked up the certificate when you left the army?
Click to expand...


Well, I have had the A&P since 2013, and up to about 6 months ago when I took delivery of the Tomahawk, it was as idle as it gets.


I did use my 6 years of aircraft maintenance experience to qualify!
 
I think you are precisely on the right track.
My AP/IA is onboard with everything here.
1957 172, came with a half dozen fuse holders original. I fabbed an aluminum mounting plate over the old glove box opening. I fitted 18 push pull Tycos in 2 rows. If space were at a premium, you might consider the klixons, they seem smaller.
Understand the breakers are from $25-$40 per. Interestingly, the 2 amps are more money than the 10 or 15 amp. I did not go with push pull for the 50 amp alternator main, a resettable is much more reasonable, and I have a 5 amp toggle switch/breaker for the alternator field, thus the main would not need to be pulled. Spruce has copper bus in a convenient size to serve the line side of your breakers.
This was all in conjunction with 0SMOH, with alternator conversion and sky tech starter, new starter contactor, all new wiring to these, the new breaker panel, battery, and new panel switches. A ton of work!
I notice the picture above has the EI digital ammeter. This comes with a shunt, so you don’t have the old fashioned in line ammeter heavy current to worry about in the cockpit. For all the points you mention, the ammeter you will love, with the capability of observing amp loads individually in flight as you pull breakers. About $400, but I think well worth it.
 
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Clip4 said:
When they built you Tomahawk Piper probably saved a nickel a breaker by not putting in push pulls.
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I don’t know about that! The push pulls today are a cost factor of almost 10:1 over pop out resettables. I just put em in my ancient 172. Had old glass fuses, you can put in new holders and fuses in for about 5 bucks. The push pull Tyco breakers are $25-$40 each.
You are correct, it is about cost. You are basically going to big airplane set up, but I think the peace of mind is worth it.
 
Sondavid said:
I did not go with push pull for the 50 amp alternator main, a resettable is much more reasonable, and I have a 5 amp toggle switch/breaker for the alternator field, thus the main would not need to be pulled.
This was all in conjunction with 0SMOH, with alternator conversion....
Click to expand...
Now, depending on the reliability of the regulator, you might not be able to shut off a rogue alternator just by turning the alternator switch off. The old electromechanical regulators, and the newer hybrids (not the ACUs) take their field current off the alternator's output sense line or the bus, depending on the airframe OEM. The ALT switch simply controls a relay in the regulator that shuts off that source. If the relay sticks itself shut (they can do that as the contacts arc and get rough) the alternator stays on. If an ACU has an internal short in its electronics, the same thing can happen.

I'd want the pullable breaker, but I have to admit that the risk is quite small, especially if you're not using an old regulator.
 
Dan Thomas said:
The average pilot has no such training. He's just told to shut the master off and good luck. It's too bad, because even if the pilot never needs to do it, it increases his/her understanding of the aircraft's systems and makes him/her a smarter owner and pilot.
Click to expand...

You're absolutely right, and is absolutely this type of ignorance actually cuts across the industry,
Sondavid said:
I think you are precisely on the right track.
My AP/IA is onboard with everything here.
1957 172, came with a half dozen fuse holders original. I fabbed an aluminum mounting plate over the old glove box opening. I fitted 18 push pull Tycos in 2 rows. If space were at a premium, you might consider the klixons, they seem smaller.
Understand the breakers are from $25-$40 per. Interestingly, the 2 amps are more money than the 10 or 15 amp. I did not go with push pull for the 50 amp alternator main, a resettable is much more reasonable, and I have a 5 amp toggle switch/breaker for the alternator field, thus the main would not need to be pulled. Spruce has copper bus in a convenient size to serve the line side of your breakers.
This was all in conjunction with 0SMOH, with alternator conversion and sky tech starter, new starter contactor, all new wiring to these, the new breaker panel, battery, and new panel switches. A ton of work!
I notice the picture above has the EI digital ammeter. This comes with a shunt, so you don’t have the old fashioned in line ammeter heavy current to worry about in the cockpit. For all the points you mention, the ammeter you will love, with the capability of observing amp loads individually in flight as you pull breakers. About $400, but I think well worth it.
Click to expand...

Yeah, having the main 50 Amp not pullable wouldn't bother me. The master does pretty much the same, and for me the point of the exercise is isolation of a single component from the rest of the buss.

It's all about dealing with an appliance which is exhibiting evidence of an internal failure, smoke, fire, doing stuff it's just not supposed to that indicates the circuit protection inside the appliance has failed. Yes, the primary and most critical drivers are addressing smoke and fire. However the secondary, and still very important in my mind are preventing further damage to the failing appliance which just turning the power switch to off doesn't guarantee. Also, there is no way to know what the failure mode inside actually is. So to prevent the now possibly compromised integrated circuitry inside the appliance from allowing surges of stray voltage to find it's way onto the buss, ICS, any digital integration links with sister components, or anywhere that would trigger a cascading failure situation, I need to cage that failing appliance in a sandbox which doesn't rely on a circuit to keep it there.

I've had a few people on another forum really push back on me for suggesting something that they "fail to see any realistic scenarios in my Tomahawk that being able to pull a circuit breaker was the difference between life and death"

I replied that his perspective didn't surprise me because there are a thousands of aircraft accidents & incidents where in many cases people lost their lives which occurred or weren't mitigated by the crew because they failed to think it could happen. I dissected his comment but by bit in a lengthy response which he never commented on... Huh.
 
Dan Thomas said:
Now, depending on the reliability of the regulator, you might not be able to shut off a rogue alternator just by turning the alternator switch off. The old electromechanical regulators, and the newer hybrids (not the ACUs) take their field current off the alternator's output sense line or the bus, depending on the airframe OEM. The ALT switch simply controls a relay in the regulator that shuts off that source. If the relay sticks itself shut (they can do that as the contacts arc and get rough) the alternator stays on. If an ACU has an internal short in its electronics, the same thing can happen.

I'd want the pullable breaker, but I have to admit that the risk is quite small, especially if you're not using an old regulator.
Click to expand...
The field source in my case is the main bus. Hartzell Plane Power ER conversion on an O-300B. A push pull 50 amp breaker is about $225, the resettable is $50.
 
Pete Lehmann said:
…I bet continuing my flight while conducting the simplistic troubleshooting process of pulling each breaker observe, no change, reset and go to the next. Hopefully there would be some evidence which would suggest a likely area the smoke seems to be originating from, or some radio or appliance started exhibiting unusual characteristics….
Click to expand...
Though you got your answer about how to go about the documentation, I want to share my experience with this from about a year ago or so.

GNS530 shut down and then restarted during a critical phase of flight; Com2/Nav2 was still operable. This cascaded to the G5 doing the same thing. No problem, hit continue on battery power for the last couple minutes into the airport. Then the ozone smell and magic smoke appeared.

Okay, we have a problem, make a quick announcement on C2/N2 and killed the master going into an uncontrolled field w/no other traffic on freq.

After I got on the ground and secured the aircraft, I found this:

18d557d747bc4c2b37b67d7285e41680.jpg



That was going to the main buss from the master. All the troubleshooting in the world wasn’t going to do anything to stop the short.
 
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