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Rob:
I haven't calculated the electrical load in my
airplane, but I can tell you from practical experience that the following
load overwhelms my 40-amp alternator:
battery contactor
avionics fan
turn coordinator
intercom
nav/comm (KX-155)
gps (KLN-94)
xponder (KT-76)
EDM-700 (engine monitor)
aux pump
instrument panel lighting (minimal)
nav lights
landing lights (two 55-watt halogens)
Whelen strobes
and either gear or flap actuation
This would be the normal configuration for a night
landing, which is when I noticed the "BATT" warning on the EDM-700 as I lowered
the gear on downwind. I got it again each time I added a notch of
flaps. The "BATT" warning is activated when bus voltage drops below
12v. Since it's the gear or flap actuation that puts it over the edge, and
these are obviously intermittent loads, I haven't worried too much about
it. Next alternator change I will consider moving up in
amperage.
My alternator is an automotive type (Mitsumi, I
think). It only has about 15 hours on it, as its predecessor burned out
after about 470 hours.
Just some real world experience, for what it's
worth.
Lee "Moondog" Metcalfe
N320WH - LNC2 - IO-320-D1C - 485 hrs. - Kansas City
(IXD)
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