Seminole Electrical System Question

IanM

Well-Known Member
#1
Hey, all! I'm starting a commercial multi add on next week in a '79 Seminole and I'm trying to get as much down now as I can. I've got a (probably stupid) question about the differences between the electrical systems in a '79 Seminole vs. newer ones (approximately '00 and on). Lots of resources for the electrical system I've found online use a diagram from the newer Seminole, which show the electrical system having 6 buses (shown below). I understand the newer diagram, everything makes sense and it's pretty clear where everything is.

Screen Shot 2018-09-10 at 19.06.03.JPG

For the life of me, I can't find as nice of a diagram in the '79 POH. The closest they have is the alternator and starter diagram (shown below) and I'm having a hard time figuring out if it just neglects to show the avionics buses shown in the newer POH, or if the '79 model has a different bus layout that you have to decipher from the diagram. The POH is certainly light on descriptive text. My best guess is that the diagram has been altered to just show what is relevant to the starters and alternators, but I'm honestly not sure.

Screen Shot 2018-09-10 at 19.00.43.JPG

Does the '79 Seminole have the same 6 bus layout that newer Seminoles do, or does it have its own deal? Thanks!!
 

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IanM

Well-Known Member
#6
Maybe. Some of the Pipers of that era had the avionics installed by a subcontractor and you can’t find schematics...but probably you have at least one avionics bus.
Ah, gotcha. I know there's only one radio master, but I guess that isn't indicative of how many avionics buses there are because they're tied together in the newer Seminoles anyhow. Thanks for the insight!

“Two wings, some fuel, and an engine or two. Max weight 3800, Vr is 75. Good luck, sailor!”
Haha the '79 POH really does feel like this a lot of the time. Kinda weird, Cessnas of a similar age seem to (in my limited experience) have much more detailed POHs.
 

Roger Roger

Paid to sleep, fly for fun
#7
Ah, gotcha. I know there's only one radio master, but I guess that isn't indicative of how many avionics buses there are because they're tied together in the newer Seminoles anyhow. Thanks for the insight!


Haha the '79 POH really does feel like this a lot of the time. Kinda weird, Cessnas of a similar age seem to (in my limited experience) have much more detailed POHs.
You would really have to look at the CB panels and see if you have an “avionics” breaker, or “avionics 1/2” breakers, or is the avionics master a switch/breaker?
 
#8
If it isn't in the POH, can you be expected to know it?
Lol. It's printed on a faded out placard in the nose compartment behind a screen that you remove with a hex driver. Take a flashlight ... and a can of pesticide.

And if it isn't in the AFM or supplements, it doesn't exist. ;)
 

IanM

Well-Known Member
#9
You would really have to look at the CB panels and see if you have an “avionics” breaker, or “avionics 1/2” breakers, or is the avionics master a switch/breaker?
Well, got weathered out and rescheduled, so had quite a bit of time to look around the airplane. Avionics master isn't a breaker, but there are breakers for most pieces of equipment. I'm thinking there's just one avionics bus. Thanks again for your help!
 
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