Silly question but what does this mean

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Joffreyyy

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Joffreyyy
The a and the b on the left side of the electrical circuit diagram for the 172? alternator and battery?
 

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Yea, the represent the "hot" leads to the buses from source.

Sent from my SM-G955U using Tapatalk
 
Both A and B go to the power junction box on the firewall and are connected via breakers to the alternator contactor, which is also connected to the battery contactor. The A and B don't mean alternator and battery. The sources aren't separated like that.
 
Matthew said:
A and B have their own fuses/breakers, and connect together at the alternator relay
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That is much better than connecting apart. I hate when that happens.
 
Matthew said:
A and B have their own fuses/breakers, and connect together at the alternator relay
Click to expand...
That is much better than connecting apart. I hate when that happens.

Brought to you by the department of redundancy department.
 
Matthew said:
Dude.

I was going to do that last weekend but we got 6" of rain Saturday.

Maybe the butt smoking will connect together with a brisket smoking this weekend.
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Coordinates?
 
Joffreyyy said:
So it is just Wires connected from the battery? here is 1/2
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The "A" and "B" labels are because the schematic is spread across two pages. They show which lines from each page are connected.

Both the "A" and "B" lines on page 2/2 get power from the same place, could be alternator or battery, through separate CBs. The purpose of this multi-bus setup is for fault isolation. If there is a fault (short) on one side (BUS 1 or BUS 2) then that side can be isolated and the other other bus can continue to be powered. The ESSENTIAL/CROSSFEED BUS is fed through both BUS 1 and BUS 2 (through diodes for isolation) so that it continues to be powered with the loss of EITHER BUS 1 or BUS 2.

I'm guessing this is for an airplane with all-electric instrumentation. G1000, electric ADI/HSI/DG, etc. and no vacuum system. By going all electric you need to provide other means of back up.
 
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