172N EPs: Master vs Radio vs Avionics power switch

[DCR]

Hello,

I think this is a simple question but just want to confirm...

Going through the 172N EPs, specifically "Electrical Fire in Flight". In the procedure they distinguish between three switches for which I can only find two. This is my understanding, please correct me if I'm wrong:

"Master Switch": Battery master (And I'm assuming also the parallel alternator switch)
"Radio switches": The single switch labeled "Radio Master" to the left of the master switches.
"Avionics power switch": ??? I always considered the Radio Master to be the "avionics" switch.

The procedure wants the "Radio switches -- OFF" and "Avionics Power Switch -- ON", so they must really be distinct switches.

My best guess is that they want the radios turned OFF individually on the panel, then the switch labeled "Radio Master" to be flipped ON on so you can diagnose if the issue is from COMM 1 or COMM 2.

If I can ask a follow up Q: what would you ACTUALLY do in this situation? If I smell smoke and suspect electrical I'm pretty sure everything is going OFF and I'm getting on the ground ASAP.

 

[flyingron]

Radio master = Avionics Power Switch.

Apparently the guy who wrote the POH and the guy who screened the panel labels weren't synced up.

 

[MauleSkinner]

If I can ask a follow up Q: what would you ACTUALLY do in this situation? If I smell smoke and suspect electrical I'm pretty sure everything is going OFF and I'm getting on the ground ASAP.

Say you’re in IMC. How are you going to find the ground safely?

Note also that in your picture, you’ve got at least two more radio switches to turn off in addition to other electrical equipment.

 

[DCR]

Say you’re in IMC. How are you going to find the ground safely?

Right - I always forget about IMC as a VFR only flyer! In that case it makes sense.

But on a clear weather VFR day I think I'll keep the radios on long enough to tell someone where to find me then turn them off.

 

[DCR]

Radio master = Avionics Power Switch.

Apparently the guy who wrote the POH and the guy who screened the panel labels weren't synced up.

To be fair this is a 172N POH off the web (link) - but I'm pretty sure the one at my school reads the same.

 

[MauleSkinner]

Right - I always forget about IMC as a VFR only flyer! In that case it makes sense.

But on a clear weather VFR day I think I'll keep the radios on long enough to tell someone where to find me then turn them off.

On a clear day I would (did) turn battery/alternator master off and fly home with no electrics. (Assuming the smoke stopped when the master went off, which it did.)

 

[DCR]

On a clear day I would (did) turn battery/anlternator master off and fly home with no electrics. (Assuming the smoke stopped when the master went off, which it did.)

Fair enough. I still have paranoid student pilot brain.

 

[455 Bravo Uniform]

Fair enough. I still have paranoid student pilot brain.

Nothing wrong with that. It’ll keep you surviving as long as it doesn’t paralyze or impact your sensible actions. Complacency is worse, cuz you can almost never cure it once you’re well along in your experiences, and only sometimes temporarily fixed by an “oh crap” moment.