Today's Message Index:
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1. 11:49 AM - Re: Re: Z102 w/AEC9005 (Robert L. Nuckolls, III)
2. 12:49 PM - Brownout, revisited (Charlie England)
3. 03:30 PM - Re: Grounding shielded wire 1/4 from one side? (Robert L. Nuckolls, III)
4. 03:32 PM - Re: Brownout, revisited (user9253)
5. 04:42 PM - Re: Grounding shielded wire 1/4 from one side? (rparigoris)
Message 1
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| Subject: | Re: Z102 w/AEC9005 |
>
>I see. So, given the reliability of batteries in general, and the
>simplicity of Z101 vs Z102, it sounds like you're leaning toward a
>recommendation for Z101 with a battery sized and maintained to
>achieve worst case engine-off pre-flight activities followed by
>spirited engine starts. The single battery would not be expected to
>support alternator-out flight loads for any longer than it takes the
>pilot to identify the problem and flip the AUX ALT
>switch. Operation in this condition would be assured by pre-flight
>testing of the standby alternator/regulator.
>
>Is that more-or-less accurate?
Yeah . . . a well crafted system doesn't suffer emergencies.
Low volts should not be an emergency. It's not even
an especially urgent event.
If mitigating action for a low volts warning doesn't
happen until, say, one minute later . . . outcome
of the flight for electrical insufficiency will
not change. Hence, if you have active notification
of low voltage, then an aux battery manager doesn't
do much to reduce risk.
If the ship is fitted with an auxiliary alternator
of lesser size, then design goals and plan-B
calculations will determine what actions are
needed after the warning . . . and time-to-
lights-out are KNOWN.
If an aux alternator can carry 100% of endurance
loads, then the flight can be continued to
airport of original destination. If it carries
less than 100% of endurance loads, then energy
stored in the battery can be drawn down with
an alternator assist. Endurance in this instance
is predictable.
If no aux alternator, then energy bucket is not
so big. But it can still be diligently allocated
for predictable endurance.
Splitting energy storage between two
batteries only doubles maintenance labor and
complicates endurance management when
loads assigned to each battery are not
identical.
Spitting that goal into two separate, probably
unequal tasks seems inelegant. It
seems that one battery, sized and maintained
to meet design goals for battery-only
endurance is more reliable and certainly
easier to meet design goals. The idea behind
'aux batteries' sort of evaporates. Indeed
all forms of 'standby' battery for the various
electro-whizzies should be evaluated. If the
engine is happy, then everybody is happy.
The steps to meeting design goals are validated
by doing the load analysis homework. Been
through this exercise many times . . . it's a
regulatory GIVEN on TC aircraft . . . for
both selection of battery capacity and protocols
for verifying conditions for continued airworthiness.
Contrary to the dreams of some program managers,
a quest for elegant design is not a straight line.
I've seen many a PERT chart forecasting time-
to-market . . . few were very accurate especially
for programs with new technology or promising
but untried philosophies.
I would describe the design process more like a spiral
path that circles the design goal several if
not many times with each circuit gathering in
useful ideas while pitching out the not so useful;
a process exceedingly difficult to plot on
a PERT chart!
When the first half dozen z-figures were published
30+ years ago, I couldn't begin to imagine
what Z101 would have looked like. Nor could
I imagine countless conversations and experiments
here on the List that drove the architecture. The
most interesting feature is a kind of plug-n-play
selection of busses and power sources easily tailored
to a wide range of projects. One drawing
may indeed replace most if to all those that
preceded it all managed by not more than 3 switches.
Z101 could have existed 30 years ago.
Nothing radically new in terms of technology.
If we'd only known then what we know
now! What's that timeless adage? Too
soon we get old and too late we get
smart?
And who is to say Z101 is the ultimate
solution? Not me. Let's continue to refine
the recipe for success while staying
mindful of the laws of physics, the
quest for reduction of weight, complexity,
cost and RISK while addressing the practical
matters of owning and operating airplanes.
Bob . . .
Message 2
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| Subject: | Brownout, revisited |
I thought I'd share my experience with curing 'brownout' in my specific
application; a followup to discussions about brownout step up converters
during the last week of Sept.
I've recently added a used (but fairly new tech) GRT Mini GA (intended for
certified a/c). and an older tech GRT Horizon HX to my panel. While the
Mini seems immune to voltage sag during starting, the HX is quite prone to
either rebooting, or more often, simply hanging up, after the start
sequence. I don't want a separate avionics switch, and the HX is fairly
slow to finish its boot process even without provocation. I looked at Bob's
circuit and wondered if I could simplify a bit for my limited needs.
The HX has three separate, diode-isolated inputs. It consumes an amp or two
in normal operation.
I used a 4A boost converter, bought via Amazon. I spliced the supply wire
that feeds the HX, so that it also feeds the boost converter. the
converter's output is adjusted to around 11.5V (enough to keep the HX
alive), and is fed into one of the spare power inputs on the HX. In four or
five flights since installation, I've had no issues with the HX rebooting
or locking up during engine start. The booster is technically always in the
circuit, but when the alternator is on line, its output 'floats' at
alternator voltage, so it's not really supplying power to the HX. IIRC, its
parasitic draw is under 1/2A.
End result: No relay, no extra feed circuit, and one extra feed into the HX
subD connector. Remember, the booster is feeding a single component in the
panel.
So far, I'm happy with the results.
Charlie
Message 3
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| Subject: | Re: Grounding shielded wire 1/4 from one side? |
At 01:18 PM 10/22/2020, you wrote:
>
>Hi Group I have a question about running a shielded wire to ground.
>On my Rotax 914 it has 2 shielded wires going from the Ducati
>ignition modules to the ignition ACS switch. The shield is connected
>to the ignition switch and is used to ground the Ducati ignition
>modules. Where the shielded wires go into the ignition connectors
>things get pretty tight and need to make sharp bends for several
>inches. The 2 shielded wires run right by my FWF ground field of
>tabs about 1/4 the total length from the ignition modules. Is there
>anything wrong with carefully removing the insulation on the
>shielded wires, wrapping ground wire to shield and carefully
>soldering then connect to field of tabs?:
>https://1drv.ms/u/s!Ah1S270Nwg9V3VSqwoGL7YgsYS7Z?e=EsKSit
What you proposed is probably fine . . .
Ground shields to airframe in only one
place (forest of tabs) using your
proposed 'tap'. Use shields to SUPPLY
ground at ignition switch.
See attached . . .
Of course the assumed condition is that
there exists a FAT wire jumper from engine
crankcase to FWL stud.
Bob . . .
Message 4
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| Subject: | Re: Brownout, revisited |
Good work Charlie.
Those DC - DC converters are so inexpensive that one could be installed for
each load that needs brownout protection. For loads that do not have built in
separate diode isolated inputs, a dual diode such as 863-MBRF20L45CTG can
be used. It is $0.83 at Mouser.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=498941#498941
Message 5
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| Subject: | Re: Grounding shielded wire 1/4 from one side? |
Hi Bob
Thank you for reply. I have a #4 fat wire running from field of tab main negative
3/8" Brass bolt pass-through FW to the starter nub on my Rotax 914. Ron P.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=498943#498943
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