REFLECTOR: 24 volt electrical system

[Al Gietzen]

Since a given load draws half the current at 24 volts that it does at 12 you
can use smaller wire with the same results. you can use wire that's only 1/4
the size, which is a pretty big deal when you're are running #18 and
everyone else is running #14. Most small planes have nearly 50 pounds of
wire in them. How would you like to save 10 pounds of dead weight?

I'm sure 24V system has some advantages; but the 50 lb. number is way too
big.  The vast majority of wires in my all electric airplane are #22.  Wires
smaller than that are more difficult to work with and do not make as
reliable a crimp; so even with 24v you may find that you'll want to use a
least #24 or larger.  A few big ones are #18, and, of course there is the
one big #2 running from contactors to starter.

 

Engine start will drop a 12-volt system to around 9 volts causing EFIS
systems to reboot, radios to loose presets and fuel totalizers to restart. A
24 volt system will only drop to about 18 volts during engine start, which
is well above the 10.5 volt minimum for modern, digital avionics. No backup
batteries, no switching, no relays, and no fiddly, complex systems to solve
a non-problem.

If my (2) PC-680 batteries are a bit low to begin with, the EFIS sometimes
reboots after engine start. Otherwise no other effects.

 

FWIW,

 

Al

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