Today's Message Index:
----------------------
1. 12:50 AM - Re: Re: RV10-List: Shunt - Location (John Tipton)
2. 05:22 AM - Re: Engine restart while airborne . . . (Robert L. Nuckolls, III)
3. 06:40 AM - Re: Shield wiring (MLWynn@aol.com)
4. 06:51 AM - Re: Microphone Question (Robert L. Nuckolls, III)
5. 06:53 AM - Re: Shield wiring (MLWynn@aol.com)
6. 05:49 PM - Re: Re: RV10-List: Shunt - Location (Robert L. Nuckolls, III)
Message 1
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| Subject: | Re: RV10-List: Shunt - Location |
An answer I understand: thank you Jeff
Sent from my iPad
----x--O--x----
> On 2 Sep 2014, at 07:18 am, Jeff Luckey <jluckey@pacbell.net> wrote:
>
> My comments are in orange (hope they are legible) & a few paragraphs at th
e bottom.
>
>
>
> 1) Connected in the B-Lead (to measure the output of the ALT).If you're go
ing to measure current anywhere, this is the
> FIRST choice . . . I will elaborate later . . .
>
> 2) Connected to the battery (to measure the load on the battery; but it mi
sses the contributions of electrons coming from the ALT to the main buss.)
> This is how it was done on cars and some airplanes for decades.
> There may be a good reason for that...
>
> Useful ONLY to the individual who KNOWS about
> how a battery behaves with a lot of electro-whizzies
> wrapped around it. Good diagnostic tool but it requires
> attention, memory (monitoring of trends) and an understanding
> of battery physics.
>
> I don't think you need a BSEE to understand how to read a battery ammeter.
Besides, if you are going to fly around in an electrically-dependent airpl
ane, it probably wouldn't hurt to learn a little about batteries & ammeters.
As pilots we do a lot of "trend monitoring".
>
> You won't find an ammeter in series with any bus structure
> on a biz jet . . . ammeters monitor generator loads.
> Not sure the Biz Jet analogy is apt here. There are lots of differences b
etween a biz jet & our OBAMs. Biz jets have 2 of lots of things, engines, g
enerators (maybe 3 w/ APU), pilots, etc. They have more complicated feed/so
urce switching. The pilots go to recurrent training which includes systems t
raining, etc. Very little of that applies to OBAMs.
>
> In other words, just 'cause they do it in Gulfstreams doesn't mean we shou
ld do it in our little airplanes.
>
> The PRIMARY electrical system monitor is active notification
> of LOW VOLTS. When the light comes on, you look to see if
> the alternator is putting out ANYTHING . . . MAYBE it has
> popped a diode and is still putting out some energy but
> at a reduced rate. You have the option of reducing load
> until the light goes out.
> You can do load reduction with the Battery Ammeter...
>
>
> Your NUMBER ONE tool for dealing with electrical system
> malfunction is active notification of low voltage. Your
> response to that event should be . . . at most . . .
> the repositioning of a couple of switches whereupon you
> assume Plan-B for getting comfortably on the ground.
>
> Absolutely.
> I don't have any of the Z figures in front of me but I have a question. I
n the most complicated Z design, how many switches does the pilot have to fl
ip in a worst case scenario?
>
> If your Plan-B calls for reading displays, flipping
> switches, pushing/pulling breakers, fiddling with
> fuses and/or WONDERING how long the battery is going
> to last . . . then you blew it before your airplane's
> first flight.
>
> Maybe... but, I didn't hear anyone suggest pushing, pulling, or fiddling, (
especially w/ fuses)... (are those checklist items?:)
>
>
> For the most part, an ammeter is useful for figuring
> things out AFTER you get back on the ground. Not having
> one available in flight should NOT be a matter of concern.
>
> OK
>
>
>
> Here's what I like about Battery Ammeters:
>
> 1. Using a zero-center ammeter provides info on the health of the battery c
harging system when everything is
> working properly. By learning to watch the charge taper after start-up yo
u can glean info about the health of your battery & charging system. Learni
ng to watch trends: "hey, that looked different than it did last time I star
ted-up. What's up with that?"
>
> 2. When the alternator fails, the ammeter automatically becomes a load met
er to aid the pilot in load-shedding, if necessary. Exa
ctly the info you want, exactly when you need it (without flipping any switc
hes).
>
>
>
> What I don't like about Alternator Load Ammeters:
>
> 1. Alternator load is not a very useful piece of information
> Do you really care what the alternator is putting out? Will you take any a
ction if the alternator load is 25 amps or if it is 40 amps - as long as the
alternator is working properly, it's replacing the necessary volume of elec
trons to handle the load... automatically. It is either working properly or
it isn't.
>
> 2. Alternator Load is kind of a muddled number. It is neither buss load n
or is it battery charge current. Those are 2 numbers I care something about
but Alternator Load gives me neither.
>
> I'm unaware of a scenario where I would see some value on the Alternator A
mmeter and say "I better do something about that!" If it is too high, indic
ating a full-field condition then I presume the my over-voltage protection s
ystem will kick-in (probably before I even have time to look at the ammeter)
and shut-down the regulator. If the alternator stops making power, my low-
volts alarm will go off and my Alternator Load Ammeter is useless.
>
>
>
> -Jeff
>
>
>
>
>
==========================
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>
Message 2
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| Subject: | Re: Engine restart while airborne . . . |
At 07:36 PM 9/1/2014, you wrote:
>Bob, Nope, a Rotax is a geared engine and when
>the engine stops so does the prop. Even the two
>strokes with relatively low compression compared
>to the 10.5 to 1 of the 912S series engines
>bring the prop to a stop PDQ when the engine stops running.
>Learned this the hard way when the engine on my
>Kolb quit on a downwind departure. Fortunately I
>was able to glide back to the runway and miss
>the idiot in the Baron who was taking off
>downwind so it ended well. Some new Hanes and a
>fuel filter and I was good as new.
>
>Rick Girard
Shucks . . . I knew that. Thanks for the
refresher course!
Bob . . .
Message 3
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| Subject: | Re: Shield wiring |
Hi All,
Over the long weekend I got the ELT mounted, the remote mounted, the phone
cable in. The really hard part was
In a message dated 8/27/2014 8:31:18 A.M. Pacific Daylight Time,
nuckolls.bob@aeroelectric.com writes:
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
<nuckolls.bob@aeroelectric.com>
At 05:40 PM 8/26/2014, you wrote:
>
>Quoted from below
>"Power(+) to the battery bus . . . use a 3A fuse."
>
>I don't think you want the power to this ELT wired to the battery
>bus. The recommended 3 month test requires the power to the ELT to
>be off. We used to get emails from SAR in Canada confirming
>satellite reception for those 3 month tests but I'm always careful
>to make sure my master (power to the ELT) is off when I test.
>
>I picked this ELT specifically because it uses aircraft power to
>pre-process gps position and have the position instantly available
>if the unit is activated. It is news to me if aircraft power is also
>available to supplement battery power for transmissions.
I'll ask ACK . . .
Bob . . .
Message 4
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| Subject: | Re: Microphone Question |
At 08:12 PM 8/29/2014, you wrote:
>Hello Bob,
>
>Haven't heard from you in a while, so I thought I'd check in. Have
>you had an opportunity to look at the mic?
>
>Kevin
The boards are on order . . .
Emacs!
Bob . . .
Message 5
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| Subject: | Re: Shield wiring |
Lets try that again. For unknown reasons, my computer occasionally sends
mail prematurely.
Anyway, I got the ELT mounted, phone line in. The difficult part was
fishing the three wire conductor from one end of the aircraft to the other. I
have the ELT power, ground and GPS feed set up in this cable. It currently
ends in the right gear tower. I have a fused power feed from a fuse block
and a ground wire from my avionics ground bus.
Unfortunately, I miscalculated the length and am about two feet short on
the three conductor getting to the back of the GPS. I have a single
shielded wire which I planned to bring down from the GPS, terminating all together
at the gear tower.
If I connect (solder) both shields and the ELT ground lead together and
ground all of that to the avionics ground bus, will that do the trick? I did
not ground the shield at the ELT end nor would I ground the shield at the
GPS end.
The GPS is a Garmin GTN 650. Steinair, who wired my panel, has four feeds
coming from a single feed (pin 8). They suggested that I tap into this
for the GPS feed. Two of the feeds go into Grand Rapids PFD and MFD. It
would be a lot easier to tap into the circuit where they enter those units
than into the GPS where there is already a four into one joint. I can't see
that it makes any electrical different which end of the wire I join into.
Am I missing anything here?
Thanks,
Michael Wynn
RV 8
Livermore, CA
In a message dated 8/27/2014 8:31:18 A.M. Pacific Daylight Time,
nuckolls.bob@aeroelectric.com writes:
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
<nuckolls.bob@aeroelectric.com>
At 05:40 PM 8/26/2014, you wrote:
>
>Quoted from below
>"Power(+) to the battery bus . . . use a 3A fuse."
>
>I don't think you want the power to this ELT wired to the battery
>bus. The recommended 3 month test requires the power to the ELT to
>be off. We used to get emails from SAR in Canada confirming
>satellite reception for those 3 month tests but I'm always careful
>to make sure my master (power to the ELT) is off when I test.
>
>I picked this ELT specifically because it uses aircraft power to
>pre-process gps position and have the position instantly available
>if the unit is activated. It is news to me if aircraft power is also
>available to supplement battery power for transmissions.
I'll ask ACK . . .
Bob . . .
Message 6
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| Subject: | Re: RV10-List: Shunt - Location |
Here's what I like about Battery Ammeters:
1. Using a zero-center ammeter provides info on the health of the
battery charging system when everything is
working properly. By learning to watch the charge taper after
start-up you can glean info about the health of your battery &
charging system. Learning to watch trends: "hey, that looked
different than it did last time I started-up. What's up with that?"
Yes, it has that functionality . . . my first car ('41 Pontiac) had
one and it took a bit to figure out the nuances of behavior. But
is THIS a useful way to track battery condition. If you're a day-vfr
airplane and you don't care about battery capacity, then you run the
battery until it doesn't crank the engine any more. You're more
likely to replace the battery because it is given you soggy starts
than if 'the needle is returning to zero just a tad too soon'.
If you have specific endurance goals then unless those goals
allow you to run a battery down to 80% of new capacity,
then you're not likely to see much of an accelerated recharge
rate on the battery ammeter when in fact, it IS time to replace
the battery.
2. When the alternator fails, the ammeter automatically becomes a
load meter to aid the pilot in load-shedding, if necessary. Exactly
the info you want, exactly when you need it (without flipping any switches).
Say what? Your Plan-B is "flip switches until you see what you
like"? This presumes, of course, that what-you-like is
consistent with prior knowledge of battery capacity and
you KNOW that the what-you-like-reading is going to get
you on the ground.
Plan-B is best crafted by (1) maintaining a battery
at some level consistent with design goals and (2)
knowing exactly what loads are to be shed after
alternator failure - BEFORE TAKEOFF.
What I don't like about Alternator Load Ammeters:
1. Alternator load is not a very useful piece of information
Do you really care what the alternator is putting out?
Nope, that's what I've said. Ammeters are of little use
as an in-flight, system management tool. Of course, you
get the same behavior from the alternator load meter
after engine start as you do with the -0+ battery
ammeter . . . a peaking of demand while the battery
is being recharged that tapers as the battery recovers.
Same date.
Will you take any action if the alternator load is 25 amps or if
it is 40 amps - as long as the alternator is working properly, it's
replacing the necessary volume of electrons to handle the load...
automatically. It is either working properly or it isn't.
Actually, I've had an instance for loosing one
phase in an alternator on a car that I had bought.
The a/c was out so I didn't run blower loads until
months later during heating season. Only then did
I discover that the battery would not get recharged
during night ops with both head-lights and blower.
When diagnosing the system I discovered that
the alternator was de-graded to about a 15-20A
machine . . . adequate to all ops when the blower
was off.
The factory stock alt warning light never did come on.
In any case, you're correct that if a low-volts warning
light is dark, then alternator output, what ever its
limits are, is adequate for the current task.
2. Alternator Load is kind of a muddled number. It is neither buss
load nor is it battery charge current. Those are 2 numbers I care
something about but Alternator Load gives me neither.
Which is precisely why it's not a flight ops display . . .
I'm unaware of a scenario where I would see some value on the
Alternator Ammeter and say "I better do something about that!" If it
is too high, indicating a full-field condition then I presume the my
over-voltage protection system will kick-in (probably before I even
have time to look at the ammeter) and shut-down the regulator. If
the alternator stops making power, my low-volts alarm will go off and
my Alternator Load Ammeter is useless.
Absolutely . . . and so is the battery ammeter.
Lord Kelvin once opined:
"When you can measure what you are speaking about,
and express it in numbers, you know something about it,
when you cannot express it in numbers, your knowledge
is of a meager and unsatisfactory kind; it may be the
beginning of knowledge, but you have scarcely, in your
thoughts advanced to the stage of science."
A load analysis is comprised of measurable values. Capacity
checks produce measurable values. Endurance based on
known capacity divided by verifiable load is a number
base on measured values.
Look through the POH for any TC aircraft having a
battery ammeter and see if the manufacturer offers
a narrative on its use as a in-flight tool beyond
an obvious failure of engine driven power source.
Emacs!
Most are no more carefully calibrated than the stock
ammeters on cars of the era . . . doing the battery ammeter
was easy, doing a low volts warning light not so much.
But it DID satisfy the FARs for offering the pilot
a means of monitoring health of the GENERATOR . . .
not the battery.
Nowadays, the low volts warning is child's play.
Bob . . .
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