So in your case opening the master(s) does not disconnect power from the busses? So I assume we now we have more switches to disconnect power?
Cockpit is still filling with smoke and you don't have time to read time POH, now what? In a few seconds you may not be able to see the panel.
(not sure you've ever seen a cockpit filling with smoke but I have (on the ground thankfully), it gets very exciting very quickly)
PS: small wires can emit large quantities of smoke as they melt, not just fat ones.
Walt - not how the design works.
Now consider my experience with RVs having absolutely dead or less than full capacity backup batteries, then overlay the risk of a pilot having an electrically dependent engine that finds himself with a stopped fan because the 60 minute backup power only lasted 15 minutes. Do builders actually test fly the plane on backup power alone to verify design targets are met?
I also suggest that a low probability but far more dangerous electrical system single fault casualty is a lithium type backup battery (or something connected to it) going nuclear. How does the pilot isolate that fire? My design mitigates this risk as multiple failures need to occur for me not to be able to isolate an electrical fault and still maintain at least half the panel.
Sorry for the thread drift but I had to comment on the trend of people just adding backup batteries while not carefully considering:
- What do I have left and how long will I have it (and does this support my IFR risk profile? I suggest that no less than a full hour of IFR flight is required, I have much more than that).
- How do I test that the various back batteries work as advertised?
- Do I have confidence that the backup batteries are properly charging - and how do I verify this?
- How often do these batteries need to be replaced to have some confidence they will meet minimum capacity requirements.
I say again, step back and overlay the requirements for what you want your plane to do, then look at a total system approach to meet those requirements as well as mitigate risk for any plausible single point failure. This includes any component (battery, alternator, solenoid, switch, etc.) as well as any connection or connecting wire.
If nothing else I’m hopeful IFR builders will see the value of not having all power going through a single Master Solenoid or the use of a single Avionics Master switch. If you want this function have two, one for each half of the panel (assumes two EFIS, two GPS sources, two radios, etc.). I can also state this is not at all hard to achieve.
Enough - stepping off my soapbox.
Carl