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1. 06:43 PM - Power (Adelk123)
2. 07:02 PM - Re: Power (Robert L. Nuckolls, III)
3. 09:10 PM - Re: Power (Adelk123)
Message 1
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Ive got a question for the group. Im currently powering dual board ECU through
a DPDT switch with each side of the switch switching different power sources.
Ive decided I dont want to use two different power sources for the ECUs. I prefer
to just power the ECUs directly off of my engine Bus. This bus is an always
hot battery bus mounted at the aft end of the Aircraft. With the floors being
closed up, access is challenging but not impossible. I had considered the idea
of each ECU having its own circuit powered off of the same bus. I am currently
out of additional circuits on that fuse box though. I have considered combining
with a circuit that I can readily access. I have two small led baggage lights
powered off of that same bus that I could tie in to fairly easily. If there
is no real benefit to having two circuits on the same bus due to the switch
still being a single point of failure, would it be acceptable to stack the terminals
on one side of the switch to power both ECUs from one source? The current
for both combined is less than 1/2 of an amp.
I realize that doing so still creates a single point of failure so Im looking for
advice finding a solution that I might not of already thought of.
Thanks for any advice.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=482061#482061
Message 2
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This bus is an always hot battery bus mounted at the aft end of the
Aircraft. With the floors being closed up, access is challenging but
not impossible. I had considered the idea of each ECU having its own
circuit powered off of the same bus.
Depending on how 'orderly' the lay of wires
is in the bundle carrying the current feeder,
it may be possible to lap solder TWO wires to
the end of the single wire thus converting the
single wire into a 'tag line' for installation
of a new pair.
I am currently out of additional circuits on that fuse box though. I
have considered combining with a circuit that I can readily access. I
have two small led baggage lights powered off of that same bus that I
could tie in to fairly easily.
Use one of those . . . separating them
eliminates the single point of failure
for one ECU (or intermediate wiring faults)
from tripping both systems off line.
If there is no real benefit to having two circuits on the same bus
due to the switch still being a single point of failure, would it be
acceptable to stack the terminals on one side of the switch to power
both ECUs from one source? The current for both combined is less than
1/2 of an amp.
Your choice . . . but I couldn't sell that
idea onto a TC aircraft. I presume you
currently have a 2nd source on a bus up
front? I think I'd leave it there. The
'plum' in your FMEA pudding is the exceedingly
remote probability of loosing BOTH sources
during the consumption of ONE tank of gas.
Exactly what those sources are is irrelevant
as long as they too do not suffer a 'cow pie'
in their FMEA.
This leaves JUST the switch which, in an
OBAM aircraft, will see perhaps a couple
hundred actuations per year . . . at your
stated load, the electrical life is infinite.
The mechanical life will be more environmentally
driven than service driven. I'd just replace
the switch for grins every 5 years or so . . .
I've seen more switches (even the $high$ mil-spec
devices) fail due to chronological AGE in
a less than pleasant environment than
from service life . . .
Bob . . .
Message 3
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Ok, thanks for the feedback.
Yes, I currently have the secondary ECU powered another bus in the front of the
airplane. What I failed to think out completely was the load shedding side of
things. My intent was to have the ability to load shed everything except the
critical engine items, the second ECU not being critical. The problem is the
switchology has become more complex than I like due to the injector relays and
their relationship with the ECUs. I feel its a safer and a more simplified solution
just to have the same power source with both ECUs and leaving no possibility
to inadvertently shut down the engine during load shedding.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=482063#482063
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