Switch and CB conversion

How to keep the Cessna 170 flying and airworthy.

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Switch and CB conversion

Postby rupertjl » Wed Mar 11, 2020 4:56 pm

I'm converting my fuse holders to CB and when i removed the piano keys and updated the switches I noticed the CA-20 Klixon switch attached to the backside of the piano key structure. Since i'm updating the switches and connecting to new CB's, can i replace that CA-20 switch that was attached to the Master switch and put in its place a appropriately sized CB as the Main breaker?
1950 170A: N9191A s/n 19366
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Re: Switch and CB conversion

Postby gahorn » Thu Mar 12, 2020 2:42 am

The “CA” designation of that CB indidates that it is a “self resetting” or “automatic” circuit breaker.

Typically those are used in positions of special importance...such as the T&B indicator (once considered the primary and most-important gyroscope due to it’s resistance to “tumbling”. ... and the stall-warning in aircraft which had stall warnings as “required equipment” (such as the B-model 170.).
I.E. it was used in circuits considered so-Paramount of importance that the pilot should have them available even in “last ditch” circumstances.

However, I do not know of any regulatory reason they cannot be replaced with another current-limiter under the “minor alteration” authority..

The question I have is : WHY ...do you feel the need to replace it, or re-set it, or disable it? What advantage would be gained?
I cannot think of one, and they are usually located whrere the pilot would not need to do so, since they are automatic.

Meanwhile, since it guards items which are mandatory per the TCDS to be operational, the inadvertent disabling of those items would affect the safety-of-flight. That’s why it’s there in the first-place. :wink:
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight.
An originality nut (mostly) for the right reasons. ;)
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Re: Switch and CB convedrsion

Postby rupertjl » Thu Mar 12, 2020 12:38 pm

i have no reason to not use, other than the plastic mount ear was cracked, so i would have to replace it anyway and wondered if it was better to upgrade. I see Univair has them in stock, just wanted to make sure since I'm into the "exploded view" of the instrument panel i was replacing or upgrading all that i could from the 1950 hardware.
1950 170A: N9191A s/n 19366
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Re: Switch and CB convedrsion

Postby rupertjl » Mon Mar 30, 2020 7:11 pm

So after three weeks and not receiving my order from Univair I called to find out what was going on. They said they cannot find stock and cancelled my order so now I'm back trying to find one or a suitable replacement.
1950 170A: N9191A s/n 19366
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Re: Switch and CB convedrsion

Postby gahorn » Mon Mar 30, 2020 8:46 pm

$72 from https://www.cessnaparts.com/product/ca2/

Texas Air Salvage has a used one for $30.

Personally... I’d use a ty-wrap and reinstall the one you have. :wink:

(Or JB Weld, etc. but to be forthright, the restorer of my airplane substituted an ordinary Klixon non-automatic breaker, but placed it where it can be reached in-flight with the rest of the CB’s with which he replaced the fuses.)
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight.
An originality nut (mostly) for the right reasons. ;)
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Re: Switch and CB convedrsion

Postby rupertjl » Thu Apr 02, 2020 8:40 pm

Found one on Amazon no less. NOS from DFWairparts. All the other places showed no stock or gave me 90 day lead times.
1950 170A: N9191A s/n 19366
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