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1. 10:57 AM - Re: Too many Circuit breakers.... (Robert L. Nuckolls, III)
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| Subject: | Re: Too many Circuit breakers.... |
At 11:43 AM 9/29/2022, you wrote:
><ceengland7@gmail.com>
>
>I have a 'FWIW' general observation about electrical systems design
>discussions that we have on this list/forum. (Some of us get email;
>others use the forum, and stuff often doesn't 'translate' well
>between the two formats.)
>
>The rise of multiple variations of electronic ignition and/or
>computer controlled, high pressure fuel delivery, the replacement of
>steam gauges with glass, and the increase in the number of people
>flying homebuilts in the IFR environment, has made these discussions
>much more difficult.
>
>Examples:
>VFR & 'traditional' engine & panel? minimal effect on electrical system design
>electronic ignition only (carb/mech injection fuel delivery)?
>minimal effect on electrical system design
>high pressure electronic fuel injection? HUGE effect
>IFR? quite serious effect, especially with a glass panel
>And I've probably forgotten other factors that significantly
>influence electrical system design.
>
>I constantly see people post a question without a complete listing
>of what will be installed, and how the plane will be operated. I
>also frequently see answers that overlook one or more of the above
>qualifiers even though it had been mentioned earlier.
>
>I wonder if it would help to have a list of installed appliances &
>intended mission requirements at the top of every post when we're
>discussing 'best practices'.
Points well taken sir. I've received many a direct request for
comment and analysis on a builder's proposed architecture
and without fail, I have to start with asking about a load analysis
(are your battery/alternator choices adequate to design goals?) and
the request for recitation on what equipment is to be installed and how
will the airplane be used (is there any single appliance the
loss of which puts your airframe at-risk?).
List EVERY device that will need ship's power.
I.e. Pick a bus, feeder and protection size for each
device. The important thing is to get every electrical
load defined and down on paper.
Then, come to the AEList and get some insights
about how and under what flight condition might some
'critical' component become inoperative.
For more than 50 years I've read the 'Dark-n-
Stormy Night' stories in the journals. It wasn't
until late in those years and well in to my
aviation career did I come to understand how
those stories sold a bill of goods to an under
informed readership. Virtually all such stories
focused on pilot awareness (or worry) about how
to deal with a similar situation in the future.
I can't recall reading any stories that spoke
to root causes and reducing risk for that
situation happening again.
Of course, fixes to reduce risk in a TC aircraft
require dispensation from On High. We are not
so encumbered in OBAM Aviation Land.
In 30+ years of rubbing elbows with the OBAM aviation
community, EVERY sad tale of an aviator's demise due
to electrical system issues will had root cause
in errors of craftsmanship, maintenance and/or
understanding.
You're dead-on for asking that every load
on the ship's busses be identified for demand,
function and necessity for putting wheels
on the ground with CONFIDENCE.
I suggest that one print out some pages . . .
https://tinyurl.com/2zxe4jsr
with one page for each proposed bus. Get every
load accounted for. Then share with as many
individuals who are willing to brainstorm
(here on the List would be good).
Then deduce how each of those busses
will be powered with a goal of achieving
dual sources for mission critical items.
Consider proposed pilot controls
with a goal of minimizing numbers of switches
and reducing risks for undesired events
arising from mis-placement of switches.
This philosophy drove the evolution of
the library of z-figures not the least
of which is what might become the "Mother
of all Z-Figures", Z101. Z101 is 'modular'
with a mix/match array of busses that cover
the vast majority of powered flight projects.
Should Z101 be found lacking in the service
of some design goal, then let's thrash
it out here on the List. This is how
shortcomings are (1) identified and
fixed or (2) dismissed as a trip down the
rabbit hole.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
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