dennis.glaeser(at)eds.com Guest
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Posted: Thu Oct 11, 2007 12:06 pm Post subject: [Probable SPAM] Z-19 E Bus feeder questions |
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<snip>
If pump #1 is burning (figuratively) up and we turn on #2 (already has a
power source), we still have power to pump #1. Ok, you know these
automotive jobs will die quickly with no fuel pump, so if pump #1 fails
we need to turn on pump #2. Not a problem, but there is some delay
there. A more robust way may might be to use a pressure switch to catch
#1 in the event of a failure and flip over to #2 auto-magically.
Given all that I would like to isolate #1 should the above events occur.
I would like to add auto failover or at least have the ability to switch
each fuel pump on independent of each other regardless of their
relationship to primary or secondary power.
<snip>
You can look at auto-failover design that Jan Eggenfeller and Gary
Newsted show in their original installation manual
(www.eggenfellneraircraft.com/iindex.htm). However their bad
experiences with pressure switches have led them to abandon that
approach. It's additional failure modes overshadowed it's usefulness.
They now recommend each pump be a simple on-off switch, powered by it's
respective battery. For takeoff and landing, turn both pumps (and
ignition switches) on, so no power loss if one fails. At a safe
altitude, turn off the aux pump and ignition - now you have time to
react if something fails. I have warning lights (LEDs) that are on when
my aux pump and aux ignition are on.
Dennis Glaeser
RV7A-EH6 (painting and final assembly)
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