All:
Jim Nelson and a few others excepted, the XS cowl can't nicely fit a standard
"big"
The Rotax-supplied alternator is of small capacity - 18A less
whatever the fuel pumps and ECU computer draw - and the vac. pad RPM is slower
than
Lycoming standard, so an SD-8 is derated to about 5A and an SD-20 to about 12A.
So good
"amperage conservation" needs to be practiced.
An annoyance is the 1A holding current of the battery contactor relay, which
represents
appx. 8%
of the net Rotax alternator capacity. If you choose to implement a fully
redundant
system, with
dual batteries and alternators, you'll have at least 2 battery contactors, plus
crossfeed contactors,
so this drain can add up fast. Although one can use manual contactors ( as Tony
K. did for
a while ) - possibly remotely activated via a Bowden cable - an alternative is
a power-managed
contactor, one example of which is the cii technologies EV-200
http://www.ciitech.com/doc_generator.asp?doc_id1280
actuator to 130mA - an 8:1 reduction from a conventional contactor relay, and
possibly
low enough to be insignificant. It is highly reliable,
lightweight, and an easy retrofit to a standard power system. Unfortunately, it
is a lot more expensive
than a conventional contactor relay - $75 instead of $15. But it may make sense
if you don't want to go to
heroic (Bowden cable) lengths to control alternator loads.
I caution that this product has not been certified for the aircraft market, nor
have I actually tested it. But
If you would like to see how the big boys do all-electric, check out the SR-22
Pilot's Operating Handbook
on the Cirrus Design website
http://www.cirrusdesign.com
Page 3-28 and Page 7-39 et. seq. are very interesting reading and a neat way of
implementing a dual-alt
dual-bat dual-bus system without the need for a crossfeed switch. It's got Bob
Nuckolls' name all over it,
but I don't think he was a part of its design. Warning: the POH is 320+ pages
and a 2.8MB download.
Shaun Simpkins
...no longer building but still scheming...
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