Today's Message Index:
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1. 03:14 AM - Re: ADS-B issue (David and Elaine lamphere)
2. 02:59 PM - Re: Re: Excessive Amperage (Robert L. Nuckolls, III)
Message 1
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Its been a while, but I remember that the key for my ADS-B report was using flight
following. Getting ATC involved. Did you make sure your reg number was set
(instead of anon) ?
Which ADS-B unit do you have?
Dave
Wittman Buttercup N365ED
On Jul 29, 2023, at 10:28 AM, merlewagner2 <wagnermerle@gmail.com> wrote:
Not sure if this is relevant to this forum but...
After going thru major fixes on my Tailwind I had a couple of test flights to check
things out.
I took a look at Flightaware.com to see the flights and they came up but the airspeeds
were very erratic. Positioning/tracking looked great, just airspeed was
crazy.
I decided to pull an ADS-B report from the FAA to see what that stated. They came
back with no report found on either flight. They suggested I send in the GPS/Transponder
for repair.
Any thoughts on what would cause the FAA to throw out a flight, ie: not create
a report. I don't have the detail on what info is broadcast on ADS-B so maybe
someone might know of a document that explains the process.
Merle
--------
KC1DNJ
General Radiotelephone
Commercial SEL
A & P
Building scale P51, rebuilding Tailwind W10
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=511166#511166
Message 2
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| Subject: | Re: Excessive Amperage |
At 12:56 PM 7/29/2023, you wrote:
>
>Looks like nonsense to me, too. Of course, I've been less than
>impressed with EX since they 1st started hyping their stuff on the
>VAF forum; it was obvious that their spokesperson knew a whole lot
>less than they pretended.
>
>1st question about the graphs in question: Why is the supply voltage
>changing, if we're talking about an aircraft (or car, or motorcycle,
>etc) charging system? If properly sized, the alternator output
>voltage isn't going to vary in normal operation.
>
>Makes me wonder if they were really trying to show the relationship
>between charge voltage and charge current, which should have been
>plotted as x/y, without time on the graph at all.
We'll probably never know . . . and the document
raises more questions than answers.
I have no doubt about that itty-bitty battery's
ability to sink 30A . . . but that's a condition
that would probably occur only if the battery
were severely discharged and then hit with
an energetic alternator of some loosely defined
setpoint.
The article suggests that dropping the charge
potential to the standby battery by ~0.6V would
prevent this deleterious inrush. The lithium
battery's ability to draw such currents is
based in part on its internal resistance. Hmmmm . . .
if 0.6 volt reduction is a 'magic' endeavor
what would happen if we put some small resistance
in series with the battery . . . say something
on the order of 50 milliohms.
Okay, try to stuff 30A thru 50 milliohms would
get you a drop of 30 x 0.05 = 1.5 volts!
That suggests any potential for 30A inrush just
evaporated.
Now, after the battery approaches full charge and
recharge load drops to say less than 1A, then
the drop becomes 0.05 volts . . . okay, no big
deal. Even with our resistor in place, the battery
WILL become full charged.
What would one expect for a voltage drop
in an 'emergency' situation? 6AH battery . . .
endurance load of what? 4A? That would give
you approximately 90 minutes endurance when
the battery is new . . . 70 minutes at end of
life. Okay 4A draw through 0.05 ohms is 0.2
volts . . . again, no device wanting power
from that battery would care.
Where does one get a 0.05 ohm power resistor?
How about 5 feet of 20AWG wire at 0.010 Ohms per
foot? It's certainly 'beefy' enough to carry
expected normal loads with negligible effect
on system performance while ADDING series
resistance to the battery thus corralling it's
willing to self destruct when charged from a
'stiff' source.
But let's further examine a fundamental
premise of that article: TWO batteries?
If we've learned anything over the past
30 or so years here on the List is that
TWO engine driven power sources beat TWO
batteries by a light year or so.
A second, seldom-if-ever-used s/b battery has
the same preventative maintenance burden
as the main battery. You are sorta obligated
to do periodic cap checks to confirm ability
to meet design goals. Oh, yeah, that's not too
hard on a long cross country, you could provide
a means by which that battery and its precious
loads are cut loose . . . then see how long
it takes for the voltage to drop into the
'worrisome' range.
But that also means that you're going to
recharge the same TOTALLY dead device over the
remainder of your trip . . . then is when
that 50 milliohm resistor comes in real
handy.
Yeah, not every engine will support two
power sources. So fine, have an separate
ENDURANCE bus that can be drawn into service
should the ONLY alternator fail.
NOW . . . you've got a ROBUST s/b battery
probably 3 or 4 times bigger than any itty-bitty,
fussy-fragile lithium device and a much simpler
system more like that described here on
the List about 30 years ago with ancestors
to Z-11.
Short answer, the EarthX article cited is
short on physics and practical realities
of robust system design. I suggest it's
safe to ignore it.
Bob . . .
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