On Sun, 4 Dec 2005 14:32:10 -0500 "Ed Anderson"
<eanderson@carolina.rr.com> writes:
> I think the old adage KISS goes a long ways - as you know, it is
possible to
> decrease reliability (not to mention increasing weight and cost) by  
> increasing redundancy pass a certain point - more parts to break.

Wow, I TOTALLY disagree with above statement. But note that I define
"redundant" as having independent failure odds (same as logical "or"
circuit). We always have risk reduction with redundancy. HUGE risk
reduction, because you multiply the odds. So 1 circuit has 1 in 100 odds
of failure. 2nd independent circuit jumps the odds to 1 in 10000! That's
why they run two power leads to the ECM on OEM cars. Also multiple ground
leads. Much much safer.

Perhaps you allude to cases where you add a second switch, but power has
to flow thru both switches for circuit to operate. In that case, yes, you
actually increase your risk. Those switches would not have independent
failure odds. If one fails, so does the other. So they are not redundant,
you just have two items (logically "and" type of circuit).

I also don't subscribe to the "single failure point" principal. Yes, risk
often has correlation to single point, but not always. Risk = odds of
failure * Effect failed component has on aircraft * odds(inverse) that
you will notice failure before flight.

> My design is such that you can even shut off the master switch and  the

> engine will continue to run.  

That is good! So you have to really work at it to get it to shut off.
Yes! Yes! I'm impressed with your custom gages Ed. It's great seeing you
take action on those items. Good stuff.



-al wick
Artificial intelligence in cockpit, Cozy IV powered by stock Subaru 2.5
N9032U 200+ hours on engine/airframe from Portland, Oregon
Prop construct, Subaru install, Risk assessment, Glass panel design info:
http://www.maddyhome.com/canardpages/pages/alwick/index.html