Circuit Breakers?

Ask Questions and Offer Advice Related to the Cessna 120 & 140 Type

Moderators: 6643, 6183, V529

Forum rules
You must be a member of the Cessna 120-140 Association in order to post new topics, reply to existing topics, or search for information on this forum. Use the "Join" link in the red menu bar.
Post Reply
scotts97385
Posts: 28
Joined: Thu Sep 01, 2022 6:52 am
Name:
Aircraft Type:
Occupation-Interests:
Contact:

Circuit Breakers?

Post by scotts97385 »

All of the fuse holders in my 120 are junk with a mangled mess of wire to go along with them..Can circuit breakers be used as replacements without a huge paperwork event?
User avatar
6643
Posts: 2337
Joined: Tue May 01, 2018 7:00 am
Location: KLCI
Name: John C
Aircraft Type: 1946 C140/C90
Occupation-Interests: A&P, semi-retired
Contact:

Re: Circuit Breakers?

Post by 6643 »

scotts97385 wrote: Thu Sep 22, 2022 7:43 pmCan circuit breakers be used as replacements
Yes.
without a huge paperwork event?
Well, that depends.

Here's the deal. Part 43 Appendix A spells out what constitutes a "Major Alteration". By definition, if an alteration is not a major alteration, then it is a minor alteration and can be accomplished with only a log book entry. The relevant wording from Appendix A is "changes to the design of the electrical system" (are major alterations.) So, if your IA agrees that replacing fuses (circuit protection devices) with breakers (also circuit protection devices) does not constitute a change to the design of the electrical system, then all you need is a log book entry.

If your IA feels the need to file a Form 337, you can cite the data in AC43.13-1b Chapter 11 Section 4 as approved data and no further approval should be necessary. You should consult this section regardless to ensure your choice of circuit breakers is appropriate; you can't always e.g. replace a 20 amp fuse with a 20 amp circuit breaker.
8224
Posts: 96
Joined: Tue May 01, 2018 7:00 am
Name:
Aircraft Type:
Occupation-Interests:
Contact:

Re: Circuit Breakers?

Post by 8224 »

Scott, John is right. I am an A&P with IA and just finished (well almost) the restoration of a 47 C-140. I replaced all the old fuses with circuit breakers and just entered it in the logbook with the rest of the work done during the rebuild. A major alteration is defined in the FARs and is basically any change from the original design that does not involve any structural member, control system or flight characteristics. All other changes are considered minor and only require a logbook entry. The change from fuses to CBS is in my opinion a no brainer. By the way, flew my 140 last Monday for the first time.
Steve Hawley
Post Reply

Who is online

Users browsing this forum: No registered users and 13 guests