Today's Message Index:
----------------------
1. 02:45 AM - Re: grounding procedures (toddheffley)
2. 08:23 AM - Re: Z12 Alternator Amps (RV7ASask)
3. 08:37 AM - General Aviation Savior?? (jonlaury)
4. 08:48 AM - Battery question not aeroplan related (Werner Schneider)
5. 08:52 AM - Re: grounding procedures (Robert L. Nuckolls, III)
6. 09:06 AM - Re: Re: grounding procedures (Robert L. Nuckolls, III)
7. 09:26 AM - Re: grounding procedures (Ed Anderson)
8. 10:30 AM - Re: Re: Z12 Alternator Amps (Robert L. Nuckolls, III)
9. 10:39 AM - Re: General Aviation Savior?? (Robert L. Nuckolls, III)
10. 10:46 AM - Re: Battery question not aeroplan related (Robert L. Nuckolls, III)
11. 10:53 AM - Re: grounding procedures (Robert L. Nuckolls, III)
12. 11:10 AM - Re: Re: Z12 Alternator Amps (Bill Bradburry)
13. 12:43 PM - Re: Re: Z12 Alternator Amps (Bob McCallum)
14. 12:51 PM - Re: Re: grounding procedures (Richard Girard)
15. 01:48 PM - Re: Battery question not aeroplan related (Werner Schneider)
16. 02:42 PM - Re: Over-voltage Circuit Trips (Robert L. Nuckolls, III)
17. 03:36 PM - Re: grounding procedures (Jeff Luckey)
18. 03:56 PM - Re: grounding procedures (Ed Anderson)
Message 1
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Subject: | Re: grounding procedures |
I was always doubted the importance of using a metal funnel until I fueled our
champ on a dry day with a large plastic funnel. I was standing in the tire so
I was also insulated. A charge built up strong enough to attract the hair on
my arm to stand up toward the cowl. No Harm, No Foul. It was a warning to alter
my behaviour before a really bad indecent occurred.
todd
--------
WWW.toddheffley.com
www.theinterconnectco.com for lighting products
AV-TS.com for Jet Aircraft Test Equipment
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=378072#378072
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Subject: | Re: Z12 Alternator Amps |
Early this morning I was in the hanger and did some major testing. I disconnected
the 20 Amp Shunt I received originally from B&C when I got the 20 Amp Aux Alternator.
I then temporarily installed a 40 Amp Shunt I had received from Dynon
but had not used. A ground run gave all the correct and expected indications.
The Aux Alternator is now showing the same Amps as the Main.
Thanks to everyone who weighed in on this issue. It looks like I have a solution.
Regards
David Lamb
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=378099#378099
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Subject: | General Aviation Savior?? |
The following arrived in my Inbox today. I subscribe to a fascinating tech newsletter (www.yet2.com,click yet2.com Marketplace, for free sign-up) and I know this list is for electrical stuff, but we all share the same interest in technology and I thought many of you would be inspired by the stuff that turns up here.
I hope you enjoy the article.
This technology could be a turning point in decreasing the cost of building airplanes.
Cheers,
John
Uni-body composite plastic chassis
Developed at a Fortune 500 company, this innovation is a patented one-piece fiber-reinforced
plastic composite chassis produced by the sheet molding compression
(SMC) production method of manufacturing. The composite structural material
used is high-glass-content vinyl ester, toughened with urethane for good fatigue
and damage tolerance. The clamp-to-clamp molding cycle time for this complete
one-piece composite chassis is four (4) minutes. Composite structural golf
cart chassis molded by the SMC method have been built and tested, and proved
to be fully operational and functional. The major advantage of this solution
is to reduce the part count from 150-200 to one molded piece with intrinsic corrosion
resistance. Moreover, the flexibility in composite design allows the molding
of different features to allow customization of the vehicle for different
uses and different power trains.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=378102#378102
Message 4
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Subject: | Battery question not aeroplan related |
Hello Bob and all,
as it is not directly aeroplane related I apologize and hope it is still
acceptable to post in that area, at the end it's about batteries an
their differences
I have an UPS which I neglected a bit and it failed recently; the
batteries in there had an ugly shape but no spill, voltage was
below 2V for each (12v 7.2A nominal)
I looked now for replacement from Panasonic (using a 17A and now 20A
since years in my plane). Interestingly enough they have two types
of this:
LC-R127R2PG1
UP-VW1245P1
price difference (in Switzerland) is 28CHF for the 1st and 49.80CHF for
the 2nd, that is quite a bit as I need a set of 4 . We have a bit an
unstable (overloaded) power net so the UPS does get in action at least
once a month.
I had a hard time to identify any facts why I should go the more
expensive way (a general statement, that UP-VW has double the life of a
LC-R was all I found).
Any recommendation you could give in that case?
Many thanks for the great support of this list!
Werner
do not archive
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Subject: | Re: grounding procedures |
At 08:46 PM 7/11/2012, you wrote:
>soooooooooooo my tanks are grounded to my engine. am i safe to
>attach a wire from my fuel nozzle to my exhaust pipe or does the
>wire need to go to the tank filler neck? [that doesn't make sense to me]
> bob noffs
The word "grounded" is poorly understood and
in this discussion poorly used. As we've studied
in other conversations, having "lots of grounds"
can be deleterious to system performance in terms
of noised conducted from one system to another.
This static charge thing, like most studies of
physics is an energy management issue. We have
an energy source (motion between dissimilar
materials in close proximity), energy storage
(capacitance - proportional to surface area
of mass carrying a charge), potential pathways
for the two masses to exchange levels of charge,
series resistance of those pathways, and finally
open air gaps in the discharge path were a spark
might form that is surrounded by a flammable mixture.
The legacy hazard from which all these discussions
arise are grounded in the management of charges
stored on LARGE surface areas (air transport/military
aircraft and fuel trucks or underground fueling
systems. BIG numbers in terms of potential energy
to be released in that worrisome air-gap.
I'll refer readers to a couple of documents I've
posted to Aeroelectric.com at
http://tinyurl.com/7et4jj5
These two documents speak to 'modeling' the human
body for the purposes of carrying out standardized
tests for ESD vulnerability. Given the surface
area of adult humans to be on the order of 1.5 to
2 square meters, they are 'modeled' as 100 picofarad
capacitors. Further the ability to conduct a charge
off that 'capacitor' is limited by the average
conductivity of the body between the center of charge
and a discharge point (finger tip) which is modeled
with a 1500 ohm resistor. Now, charge the capacitor up
to various voltages up to 15,000 volts and you have
a repeatable means for generating antagonistic stresses
on some device to be tested for ESD immunity.
The machine model is similar but 200 picofarads and
1 ohm of series resistance. I.e., more surface area
and better conductivity.
Now, what might we think the model would be for a
B-747? LOTS of surface area and metallic structure
which provides very low series resistance. Static
charges between large masses can knock you on your
can.
Getting back to filling puddle jumpers from gas
cans or even fuel trucks . . .
The model for a plastic airplane might consider
a surface area on the order of 1000 picofarads
but what's the series resistance? It's an insulator
with hing series resistance. In my studies
with ESD testing I discovered that the WORST case
instances for testing to human body model (15KV)
VERY LITTLE of the potential energy was dissipated
at the victim . . . that 1500 ohm resistor dissipates
90 plus % of the energy. When dealing with things
like metal airplanes and fuel trucks, the machine
models are in force with something on the order of 1000-2000
pf each and VERY LOW series resistance. Connecting
them together before dragging out the hose MAY
NOT dissipate all their charges to zero . . . but it does
bring them TOGETHER in terms of voltage thus ELIMINATING
a potential of spark through a low series resistance.
I forget the structure of the airplane that started
this discussion but I think we were talking about a
non-conductive hose fitted to a fuel transfer pump.
In this instance, ADDING a low series resistance
conductor along the hose length only increases potential
for energy dissipation in a spark at the end of the
hose. Bringing a potential charge on the airplane and
fuel storage containers together is 99.9% of the
safety issue. Having a very large series resistance
in the potential ignition discharge path is another
risk mitigation move.
I've been reading lengthy discussions about fuel
transfer safety on OBAM aircraft for decades sprinkled
with hangar tales and speculative advice . . .
but never have I seen a study of the physics that
underlie the potential for an ignition accident.
Just consider the millions of cars that get fueled
by ding-a-ling drivers every day without blowing
themselves up. Yes, there are the expected 'news'
stories and security camera videos about the
occasional filling station fire. Shucks even the
Mytbusters made a show out of the notion that cell
phones can trigger explosions or fire.
But even the hallowed Mythbusters failed to
mention the physics . . . much less consider how
HARD it is to initiate an explosion under laboratory
conditions (re: explosion proofing tests on motors
we used to build at Electro-Mech).
Bottom line is that if you don't have a means to
bring the surface charge of a container to the same potential
as the surface of your airplane, then the SAME limitation
is in force for causing a spark at the opening of your
filler cap. I.e. if you can't get a spark at the connection
of a potential equalization wire at the exhaust stack of
your engine, you won't get a spark at the filler cap
either. Potentials generated by flowing fuel are
similarly limited in their ability to conduct the
charge to a 'arc gap'. Consider that the fuel
is in constant motion so any charge the liquid carries
is being continuously dumped into the tank . . .
Where is the 'conductor' that's going to bring
that charge to an arc gap? Flammable hydrocarbons
heavier than gasolines are used as medium for
cooling and INSULATOR in high voltage transformers and
capacitors.
Where does the energy come from, where is it stored,
what is the potential equalization path, what is
the series resistance of that path, is it possible
or even NECESSARY to effect an equalization of
potentials at some point AWAY from the filler cap?
Bottom line is that using the same care you would
exercise in filling your car, boat or lawn mower will
suffice to secure your healthy use of that machine.
Adding prophylactic features willy-nilly without
understanding the physics and design goals may
increase risk as opposed to reducing it. If the
truth were known as to root cause for the anecdotal
fuel transfer fires, most if not all would be due
to carelessness.
Bob . . .
Message 6
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Subject: | Re: grounding procedures |
At 04:44 AM 7/12/2012, you wrote:
><public@toddheffley.com>
>
>I was always doubted the importance of using a metal funnel until I
>fueled our champ on a dry day with a large plastic funnel. I was
>standing in the tire so I was also insulated. A charge built up
>strong enough to attract the hair on my arm to stand up toward the
>cowl. No Harm, No Foul. It was a warning to alter my behaviour
>before a really bad indecent occurred.
>
>todd
Sure, while funnels provide a handy tool for control
of the flow of liquid, they add a piece of 'loose gear'
to the mix and expose a the surface of liquid flow
to the air (and funnel surface). The former increases
local concentration of hazardous vapor, the later increases
potential for building an electro-static charge (motion
of dissimilar materials in close proximity). Your body
became yet another surface on which generated charges
could collect. A hair-raising experience both literally
and for consideration of increased risk.
99.999+ of fuel transfers in the world are effected with
a nozzle extend into the fuel storage system. Most are
metallic and in contact with each other. The only
thing you can do to IMPROVE on this combination would
be to close the liquid motion off from the air and
potential for spillage by using some feature like I
suggested yesterday.
As a general rule, I would avoid the use of funnels.
Yeah, Lindbergh used 'em . . . even lined the funnel
with a chamois to absorb water. We don't read much
about aviators of yor setting themselves on fire
during a fueling accident but the risks were demonstrably
great.
Bob . . .
Message 7
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Subject: | Re: grounding procedures |
I was once fueling my Rv-6A out of "Approved" plastic 5 gallon fuel
container. I had a racing funnel with a paper filter cartridge in the
center of the spout. It was a 60F low humidity day with no wind. I had
done this many times before.
This time near the end of the 5 gallon container, I attempted to raise
the bottom of the container higher to get the last of the fuel and broke
connection between the funnel (also plastic) and the fuel container.
There was a "Whomp" of ignition and I found myself with an event on my
hands, to wit:
1. Holding a 5 gallon container with flames out its nozzle
2. Holding a large racing funnel with fuel soaked paper filter blazing
way.
3. Haven been mildly started by the unexpected ignition event - I had
stepped back a pace. This resulting in the funnel I was holding being
pulled from the fuel tank leaving me with flames coming out of the
aircraft fuel tank, flames on the wing surface where I dragged the
emptying funnel from the wing tank opening and flames on the tarmac from
that dripping from the wing.
The first thought after "oh S...t" was not too panic, after which I
quickly
1. Walked approx 15 feet from the aircraft and set down flaming
container and funnel.
2. Ran to my Van for my fire extinuisher - always stored under drives
seat (could not located it)
3. Raced back to the aircraft and brushed off the surface fuel/fire
with a rag.
4. Picked up the wing tank fuel cap and remembered thinking "..this
always worked in science class!" ..slapped to fuel cap into the flaming
opening -which fortuntately worked just like in highschool science class
with test tube and cork.
5. Stomped out the small fire on the tarmac.
Fortunately no damage to anything but my nerves and the funnel and
container.
Even though I had used plastic fuel containers for decades refueling
lawnmowers, etc without ever having an incident - I never used anything
but metal containers aftewards - however, I was later told that the the
breaking of the connection permitted the liquid flow to generated a
static potential difference and it would not have mattered if funnel and
container had been metal - it was the breaking of the connection that
apparently resulting in the conditions that lead to ignition.
FWIW
Ed
From: Robert L. Nuckolls, III
Sent: Thursday, July 12, 2012 11:52 AM
Subject: Re: AeroElectric-List: grounding procedures
At 08:46 PM 7/11/2012, you wrote:
soooooooooooo my tanks are grounded to my engine. am i safe to attach
a wire from my fuel nozzle to my exhaust pipe or does the wire need to
go to the tank filler neck? [that doesn't make sense to me]
bob noffs
The word "grounded" is poorly understood and
in this discussion poorly used. As we've studied
in other conversations, having "lots of grounds"
can be deleterious to system performance in terms
of noised conducted from one system to another.
This static charge thing, like most studies of
physics is an energy management issue. We have
an energy source (motion between dissimilar
materials in close proximity), energy storage
(capacitance - proportional to surface area
of mass carrying a charge), potential pathways
for the two masses to exchange levels of charge,
series resistance of those pathways, and finally
open air gaps in the discharge path were a spark
might form that is surrounded by a flammable mixture.
The legacy hazard from which all these discussions
arise are grounded in the management of charges
stored on LARGE surface areas (air transport/military
aircraft and fuel trucks or underground fueling
systems. BIG numbers in terms of potential energy
to be released in that worrisome air-gap.
I'll refer readers to a couple of documents I've
posted to Aeroelectric.com at
http://tinyurl.com/7et4jj5
These two documents speak to 'modeling' the human
body for the purposes of carrying out standardized
tests for ESD vulnerability. Given the surface
area of adult humans to be on the order of 1.5 to
2 square meters, they are 'modeled' as 100 picofarad
capacitors. Further the ability to conduct a charge
off that 'capacitor' is limited by the average
conductivity of the body between the center of charge
and a discharge point (finger tip) which is modeled
with a 1500 ohm resistor. Now, charge the capacitor up
to various voltages up to 15,000 volts and you have
a repeatable means for generating antagonistic stresses
on some device to be tested for ESD immunity.
The machine model is similar but 200 picofarads and
1 ohm of series resistance. I.e., more surface area
and better conductivity.
Now, what might we think the model would be for a
B-747? LOTS of surface area and metallic structure
which provides very low series resistance. Static
charges between large masses can knock you on your
can.
Getting back to filling puddle jumpers from gas
cans or even fuel trucks . . .
The model for a plastic airplane might consider
a surface area on the order of 1000 picofarads
but what's the series resistance? It's an insulator
with hing series resistance. In my studies
with ESD testing I discovered that the WORST case
instances for testing to human body model (15KV)
VERY LITTLE of the potential energy was dissipated
at the victim . . . that 1500 ohm resistor dissipates
90 plus % of the energy. When dealing with things
like metal airplanes and fuel trucks, the machine
models are in force with something on the order of 1000-2000
pf each and VERY LOW series resistance. Connecting
them together before dragging out the hose MAY
NOT dissipate all their charges to zero . . . but it does
bring them TOGETHER in terms of voltage thus ELIMINATING
a potential of spark through a low series resistance.
I forget the structure of the airplane that started
this discussion but I think we were talking about a
non-conductive hose fitted to a fuel transfer pump.
In this instance, ADDING a low series resistance
conductor along the hose length only increases potential
for energy dissipation in a spark at the end of the
hose. Bringing a potential charge on the airplane and
fuel storage containers together is 99.9% of the
safety issue. Having a very large series resistance
in the potential ignition discharge path is another
risk mitigation move.
I've been reading lengthy discussions about fuel
transfer safety on OBAM aircraft for decades sprinkled
with hangar tales and speculative advice . . .
but never have I seen a study of the physics that
underlie the potential for an ignition accident.
Just consider the millions of cars that get fueled
by ding-a-ling drivers every day without blowing
themselves up. Yes, there are the expected 'news'
stories and security camera videos about the
occasional filling station fire. Shucks even the
Mytbusters made a show out of the notion that cell
phones can trigger explosions or fire.
But even the hallowed Mythbusters failed to
mention the physics . . . much less consider how
HARD it is to initiate an explosion under laboratory
conditions (re: explosion proofing tests on motors
we used to build at Electro-Mech).
Bottom line is that if you don't have a means to
bring the surface charge of a container to the same potential
as the surface of your airplane, then the SAME limitation
is in force for causing a spark at the opening of your
filler cap. I.e. if you can't get a spark at the connection
of a potential equalization wire at the exhaust stack of
your engine, you won't get a spark at the filler cap
either. Potentials generated by flowing fuel are
similarly limited in their ability to conduct the
charge to a 'arc gap'. Consider that the fuel
is in constant motion so any charge the liquid carries
is being continuously dumped into the tank . . .
Where is the 'conductor' that's going to bring
that charge to an arc gap? Flammable hydrocarbons
heavier than gasolines are used as medium for
cooling and INSULATOR in high voltage transformers and
capacitors.
Where does the energy come from, where is it stored,
what is the potential equalization path, what is
the series resistance of that path, is it possible
or even NECESSARY to effect an equalization of
potentials at some point AWAY from the filler cap?
Bottom line is that using the same care you would
exercise in filling your car, boat or lawn mower will
suffice to secure your healthy use of that machine.
Adding prophylactic features willy-nilly without
understanding the physics and design goals may
increase risk as opposed to reducing it. If the
truth were known as to root cause for the anecdotal
fuel transfer fires, most if not all would be due
to carelessness.
Bob . . .
No virus found in this message.
Checked by AVG - www.avg.com
07/12/12
Message 8
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Subject: | Re: Z12 Alternator Amps |
At 10:21 AM 7/12/2012, you wrote:
>
>Early this morning I was in the hanger and did some major testing. I
>disconnected the 20 Amp Shunt I received originally from B&C when I
>got the 20 Amp Aux Alternator. I then temporarily installed a 40 Amp
>Shunt I had received from Dynon but had not used. A ground run gave
>all the correct and expected indications. The Aux Alternator is now
>showing the same Amps as the Main.
>
>Thanks to everyone who weighed in on this issue. It looks like I
>have a solution.
This speaks to calibration issues for switching
one display between multiple values to be measured,
converted to 'amps' and displayed to the operator.
A ammeter shunt in simply a power resistor, usually fabricated
from manganin (high resistance, low temperature coefficient of
resistance). Here's a popular example:
[]
Two terminals for high current, two SEPARATE terminals
for sampling the voltage dropped across the resistance
(thin strut between the posts).
Shunts are always paired with an instrument. The instrument
will display some reading at full scale when excited by
a voltage. A legacy convention is to craft ammeters that
go to full scale with 50 millivolts applied. Accurate
pairing calls for installing a scale plate with an
appropriate full scale value (in example below it's
30 Amps; and then combining it with a shunt that drops
full scale volts for the instrument when carrying 30
amps).
[]
When you want to watch two different current flows with
a single instrument, you pick two shunts large enough
to cover the largest expected current flow . . . but
for the display in amps to be accurate, they must be
identical shunts.
If the two current flows are widely separated (suppose
b-lead currents from say a 60A main alternator
and an 8A SD-8 alternator), then an ammeter that
reads 60+ amps full scale is not so useful for slicing
up the output of an 8A alternator.
This is often handled by not calibrating the ammeter
in AMPs but in PERCENT of full load for the devices
being monitored. For example, the ammeter we offer
Emacs!
Is calibrated in percent. We then offer a variety of
shunts calibrated to the instrument and scaled to the
load being monitored. For example, an SD-8/60A combo
would call for a 10A/60A shunts. An SD-20/40A combo
would be 20/40, etc.
When you have a digital display like Dynon, it may
come to you with a FIXED input sensitivity for full
scale, like a steam-gauge . . .
It may be programmable either from a local keyboard
or USB input. But in any case, it's probably NOT capable
of different sensitivities. In the situation we're
considering, 40A, 50mv shunts give accurate readings
on the Dynon . . . irrespective of the size of the
device being monitored.
Bob . . .
Message 9
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Subject: | Re: General Aviation Savior?? |
At 10:35 AM 7/12/2012, you wrote:
>
>The following arrived in my Inbox today. I subscribe to a
>fascinating tech newsletter
Good find. I've subscribed also. Thanks for the heads-up.
Bob . . .
Message 10
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Subject: | Re: Battery question not aeroplan related |
At 10:48 AM 7/12/2012, you wrote:
>
>Hello Bob and all,
>
>as it is not directly aeroplane related I apologize and hope it is
>still acceptable to post in that area, at the end it's about
>batteries an their differences
>
>I have an UPS which I neglected a bit and it failed recently; the
>batteries in there had an ugly shape but no spill, voltage was
>below 2V for each (12v 7.2A nominal)
>
>I looked now for replacement from Panasonic (using a 17A and now 20A
>since years in my plane). Interestingly enough they have two types
>of this:]
Have you considered automotive batteries for this
application? My UPS here has a regular car battery
sitting outside the case connected to nice fat wires
that extend the leads for a battery normally inside
the case.
I can get a lot more capacity for less dollars as
long as it's not a requirement that the battery
'fit inside'.
How old was your original battery? The fact that
it failed and changed shape suggests an overcharge
condition. What ever your choice of battery, you
might want to put a voltmeter on the battery and
watch it for a few weeks and in particular after
a power-outage event to watch the re-charge event.
When all topped off, the battery should be floated
at no more than 13.8 volts and no less than 13.0
volts. In other words, too low to allow the battery
to be charged and too high to allow the battery to
take on 'load'.
My UPS battery is about 50A.H. It will keep my
desk system up for 5 hours or more.
Bob . . .
Message 11
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Subject: | Re: grounding procedures |
Even though I had used plastic fuel containers for decades refueling
lawnmowers, etc without ever having an incident - I never used
anything but metal containers aftewards - however, I was later told
that the the breaking of the connection permitted the liquid flow to
generated a static potential difference and it would not have
mattered if funnel and container had been metal - it was the breaking
of the connection that apparently resulting in the conditions that
lead to ignition.
Interestingly enough, 'grounding' the airplane
would have probably not have changed the outcome.
Your particular air/fuel/ignition triad was
constituted within a mini-system outside and separate
from the airplane itself.
Bob . . .
Message 12
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Subject: | Re: Z12 Alternator Amps |
Isn't the shunt supposed to be the same as the range on the reading
instrument?
Bill
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of RV7ASask
Sent: Thursday, July 12, 2012 11:21 AM
Subject: AeroElectric-List: Re: Z12 Alternator Amps
Early this morning I was in the hanger and did some major testing. I
disconnected the 20 Amp Shunt I received originally from B&C when I got the
20 Amp Aux Alternator. I then temporarily installed a 40 Amp Shunt I had
received from Dynon but had not used. A ground run gave all the correct and
expected indications. The Aux Alternator is now showing the same Amps as the
Main.
Thanks to everyone who weighed in on this issue. It looks like I have a
solution.
Regards
David Lamb
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=378099#378099
Message 13
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Subject: | Re: Z12 Alternator Amps |
Yes. (or the reading instrument needs to be calibrated to match the shunt.
(same thing))
Bob McC
> From: bbradburry@bellsouth.net
> To: aeroelectric-list@matronics.com
> Subject: RE: AeroElectric-List: Re: Z12 Alternator Amps
> Date: Thu=2C 12 Jul 2012 14:09:33 -0400
>
lsouth.net>
>
> Isn't the shunt supposed to be the same as the range on the reading
> instrument?
>
> Bill
>
> -----Original Message-----
> From: owner-aeroelectric-list-server@matronics.com
> [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of RV7ASa
sk
> Sent: Thursday=2C July 12=2C 2012 11:21 AM
> To: aeroelectric-list@matronics.com
> Subject: AeroElectric-List: Re: Z12 Alternator Amps
>
>
>
> Early this morning I was in the hanger and did some major testing. I
> disconnected the 20 Amp Shunt I received originally from B&C when I got t
he
> 20 Amp Aux Alternator. I then temporarily installed a 40 Amp Shunt I had
> received from Dynon but had not used. A ground run gave all the correct a
nd
> expected indications. The Aux Alternator is now showing the same Amps as
the
> Main.
>
> Thanks to everyone who weighed in on this issue. It looks like I have a
> solution.
>
> Regards
> David Lamb
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=378099#378099
>
>
>
>
>
>
>
>
>
>
>
===========
===========
===========
===========
>
>
>
Message 14
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Subject: | Re: grounding procedures |
Bob, I built this rig to fuel my little LSA. I built it mainly to get out
of having to bend over and crawl under the wing to fuel, but it also gets
me away from where the fuel is flowing. The tubing legs (titanium from
Boeing Surplus!) provide grounding although I am going to take advantage of
the advice offered here and install a copper wire to pick up any static
from fuel flowing through the plastic pipe and run it out to the legs to
ground that, too. Using stuff from my strategic supplies and plastic pipe
and fittings from Lowe's the whole thing cost less than $10.
The other precaution I use during fueling is to always have a size 20 fire
extinguisher rated for flammable liquids right next to me.
Rick Girard
On Thu, Jul 12, 2012 at 11:05 AM, Robert L. Nuckolls, III <
nuckolls.bob@aeroelectric.com> wrote:
> nuckolls.bob@aeroelectric.com**>
>
>
> At 04:44 AM 7/12/2012, you wrote:
>
>> public@toddheffley.com>
>>
>> I was always doubted the importance of using a metal funnel until I
>> fueled our champ on a dry day with a large plastic funnel. I was standing
>> in the tire so I was also insulated. A charge built up strong enough to
>> attract the hair on my arm to stand up toward the cowl. No Harm, No Foul.
>> It was a warning to alter my behaviour before a really bad indecent
>> occurred.
>>
>> todd
>>
>
>
> Sure, while funnels provide a handy tool for control
> of the flow of liquid, they add a piece of 'loose gear'
> to the mix and expose a the surface of liquid flow
> to the air (and funnel surface). The former increases
> local concentration of hazardous vapor, the later increases
> potential for building an electro-static charge (motion
> of dissimilar materials in close proximity). Your body
> became yet another surface on which generated charges
> could collect. A hair-raising experience both literally
> and for consideration of increased risk.
>
> 99.999+ of fuel transfers in the world are effected with
> a nozzle extend into the fuel storage system. Most are
> metallic and in contact with each other. The only
> thing you can do to IMPROVE on this combination would
> be to close the liquid motion off from the air and
> potential for spillage by using some feature like I
> suggested yesterday.
>
> As a general rule, I would avoid the use of funnels.
> Yeah, Lindbergh used 'em . . . even lined the funnel
> with a chamois to absorb water. We don't read much
> about aviators of yor setting themselves on fire
> during a fueling accident but the risks were demonstrably
> great.
>
>
> Bob . . .
>
>
--
Zulu Delta
Mk IIIC
Thanks, Homer GBYM
It isn't necessary to have relatives in Kansas City in order to be unhappy.
- Groucho Marx
Message 15
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Subject: | Re: Battery question not aeroplan related |
Thanks Bob, find my answers inside
>
> Have you considered automotive batteries for this
> application?
The UPS is rack mounted and uses 4 batteries always 2 in series so I
guess I will try tomorrow if I can test with two in series if it works
(I've tried already with one but it did not work (I guess it's using 24 V)
>
> How old was your original battery? The fact that
> it failed and changed shape suggests an overcharge
> condition. What ever your choice of battery, you
> might want to put a voltmeter on the battery and
> watch it for a few weeks and in particular after
> a power-outage event to watch the re-charge event.
They were over 10 years old and I've got some warnings, but as these
were LED's only and I had the operation manual not at hand I neglected
for several weeks that then caused probably to overload as some cells
were dead.
Cheers Werner
do not archive
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Subject: | Re: Over-voltage Circuit Trips |
At 06:37 AM 7/11/2012, you wrote:
>
>Bob N. et al,
>
>Since my RV first flew about a year ago the over-voltage circuit has
>frequently tripped shortly after take off. Resetting the 5 amp
>pull-able circuit breaker once or twice generally prevents a
>re-occurence for the remainder of the flight but I need to determine
>the root cause and correct it.
Jack, I'm not ignoring you. Will have a response
and some suggestions in the morning . . .
Bob . . .
Message 17
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Subject: | grounding procedures |
Ed,
Your story scares the s**t out of me (I wonder if the same happened to you?)
but thanks for sharing. After having the advantage of reading about your
experience I think I would change the order of operations a little:
1. Before starting refueling operations, make sure fire extinguisher is
where I think it is - perhaps even set it nearby on tarmac
2. get rid of flaming container in my hands - keep me from catching on
fire
3. replace fuel cap - keep my airplane/fuel tank from continuing to
burn
4. go for extinguisher
I think this will become my pre-fueling check-list.
One thing that I do when fueling from plastic containers is, before I start
pouring, touch the airplane (metal airplane) near the fuel cap while holding
the full fuel container in the other hand.
In my little mind this helps equalize any differences in potential among
airframe, fuel container, & me.
_____
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Ed
Anderson
Sent: Thursday, July 12, 2012 09:25
Subject: Re: AeroElectric-List: grounding procedures
I was once fueling my Rv-6A out of "Approved" plastic 5 gallon fuel
container. I had a racing funnel with a paper filter cartridge in the
center of the spout. It was a 60F low humidity day with no wind. I had
done this many times before.
This time near the end of the 5 gallon container, I attempted to raise the
bottom of the container higher to get the last of the fuel and broke
connection between the funnel (also plastic) and the fuel container. There
was a "Whomp" of ignition and I found myself with an event on my hands, to
wit:
1. Holding a 5 gallon container with flames out its nozzle
2. Holding a large racing funnel with fuel soaked paper filter blazing way.
3. Haven been mildly started by the unexpected ignition event - I had
stepped back a pace. This resulting in the funnel I was holding being
pulled from the fuel tank leaving me with flames coming out of the aircraft
fuel tank, flames on the wing surface where I dragged the emptying funnel
from the wing tank opening and flames on the tarmac from that dripping from
the wing.
The first thought after "oh S...t" was not too panic, after which I quickly
1. Walked approx 15 feet from the aircraft and set down flaming container
and funnel.
2. Ran to my Van for my fire extinuisher - always stored under drives seat
(could not located it)
3. Raced back to the aircraft and brushed off the surface fuel/fire with a
rag.
4. Picked up the wing tank fuel cap and remembered thinking "..this always
worked in science class!" ..slapped to fuel cap into the flaming opening
-which fortuntately worked just like in highschool science class with test
tube and cork.
5. Stomped out the small fire on the tarmac.
Fortunately no damage to anything but my nerves and the funnel and
container.
Even though I had used plastic fuel containers for decades refueling
lawnmowers, etc without ever having an incident - I never used anything but
metal containers aftewards - however, I was later told that the the breaking
of the connection permitted the liquid flow to generated a static potential
difference and it would not have mattered if funnel and container had been
metal - it was the breaking of the connection that apparently resulting in
the conditions that lead to ignition.
FWIW
Ed
From: Robert <mailto:nuckolls.bob@aeroelectric.com> L. Nuckolls, III
Sent: Thursday, July 12, 2012 11:52 AM
Subject: Re: AeroElectric-List: grounding procedures
At 08:46 PM 7/11/2012, you wrote:
soooooooooooo my tanks are grounded to my engine. am i safe to attach a
wire from my fuel nozzle to my exhaust pipe or does the wire need to go to
the tank filler neck? [that doesn't make sense to me]
bob noffs
The word "grounded" is poorly understood and
in this discussion poorly used. As we've studied
in other conversations, having "lots of grounds"
can be deleterious to system performance in terms
of noised conducted from one system to another.
This static charge thing, like most studies of
physics is an energy management issue. We have
an energy source (motion between dissimilar
materials in close proximity), energy storage
(capacitance - proportional to surface area
of mass carrying a charge), potential pathways
for the two masses to exchange levels of charge,
series resistance of those pathways, and finally
open air gaps in the discharge path were a spark
might form that is surrounded by a flammable mixture.
The legacy hazard from which all these discussions
arise are grounded in the management of charges
stored on LARGE surface areas (air transport/military
aircraft and fuel trucks or underground fueling
systems. BIG numbers in terms of potential energy
to be released in that worrisome air-gap.
I'll refer readers to a couple of documents I've
posted to Aeroelectric.com at
http://tinyurl.com/7et4jj5
These two documents speak to 'modeling' the human
body for the purposes of carrying out standardized
tests for ESD vulnerability. Given the surface
area of adult humans to be on the order of 1.5 to
2 square meters, they are 'modeled' as 100 picofarad
capacitors. Further the ability to conduct a charge
off that 'capacitor' is limited by the average
conductivity of the body between the center of charge
and a discharge point (finger tip) which is modeled
with a 1500 ohm resistor. Now, charge the capacitor up
to various voltages up to 15,000 volts and you have
a repeatable means for generating antagonistic stresses
on some device to be tested for ESD immunity.
The machine model is similar but 200 picofarads and
1 ohm of series resistance. I.e., more surface area
and better conductivity.
Now, what might we think the model would be for a
B-747? LOTS of surface area and metallic structure
which provides very low series resistance. Static
charges between large masses can knock you on your
can.
Getting back to filling puddle jumpers from gas
cans or even fuel trucks . . .
The model for a plastic airplane might consider
a surface area on the order of 1000 picofarads
but what's the series resistance? It's an insulator
with hing series resistance. In my studies
with ESD testing I discovered that the WORST case
instances for testing to human body model (15KV)
VERY LITTLE of the potential energy was dissipated
at the victim . . . that 1500 ohm resistor dissipates
90 plus % of the energy. When dealing with things
like metal airplanes and fuel trucks, the machine
models are in force with something on the order of 1000-2000
pf each and VERY LOW series resistance. Connecting
them together before dragging out the hose MAY
NOT dissipate all their charges to zero . . . but it does
bring them TOGETHER in terms of voltage thus ELIMINATING
a potential of spark through a low series resistance.
I forget the structure of the airplane that started
this discussion but I think we were talking about a
non-conductive hose fitted to a fuel transfer pump.
In this instance, ADDING a low series resistance
conductor along the hose length only increases potential
for energy dissipation in a spark at the end of the
hose. Bringing a potential charge on the airplane and
fuel storage containers together is 99.9% of the
safety issue. Having a very large series resistance
in the potential ignition discharge path is another
risk mitigation move.
I've been reading lengthy discussions about fuel
transfer safety on OBAM aircraft for decades sprinkled
with hangar tales and speculative advice . . .
but never have I seen a study of the physics that
underlie the potential for an ignition accident.
Just consider the millions of cars that get fueled
by ding-a-ling drivers every day without blowing
themselves up. Yes, there are the expected 'news'
stories and security camera videos about the
occasional filling station fire. Shucks even the
Mytbusters made a show out of the notion that cell
phones can trigger explosions or fire.
But even the hallowed Mythbusters failed to
mention the physics . . . much less consider how
HARD it is to initiate an explosion under laboratory
conditions (re: explosion proofing tests on motors
we used to build at Electro-Mech).
Bottom line is that if you don't have a means to
bring the surface charge of a container to the same potential
as the surface of your airplane, then the SAME limitation
is in force for causing a spark at the opening of your
filler cap. I.e. if you can't get a spark at the connection
of a potential equalization wire at the exhaust stack of
your engine, you won't get a spark at the filler cap
either. Potentials generated by flowing fuel are
similarly limited in their ability to conduct the
charge to a 'arc gap'. Consider that the fuel
is in constant motion so any charge the liquid carries
is being continuously dumped into the tank . . .
Where is the 'conductor' that's going to bring
that charge to an arc gap? Flammable hydrocarbons
heavier than gasolines are used as medium for
cooling and INSULATOR in high voltage transformers and
capacitors.
Where does the energy come from, where is it stored,
what is the potential equalization path, what is
the series resistance of that path, is it possible
or even NECESSARY to effect an equalization of
potentials at some point AWAY from the filler cap?
Bottom line is that using the same care you would
exercise in filling your car, boat or lawn mower will
suffice to secure your healthy use of that machine.
Adding prophylactic features willy-nilly without
understanding the physics and design goals may
increase risk as opposed to reducing it. If the
truth were known as to root cause for the anecdotal
fuel transfer fires, most if not all would be due
to carelessness.
Bob . . .
href="http://www.matronics.com/Navigator?AeroElectric-List">http://www.matro
nics.com/Navigator?AeroElectric-List
href="http://forums.matronics.com">http://forums.matronics.com
href="http://www.matronics.com/contribution">http://www.matronics.com/c
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Message 18
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Subject: | Re: grounding procedures |
I think I did require an underwear check, Jeff. Yes, thinking these
things out before hand is certainly the way to do it - coming up with a
check list during - is not recommended {:>).
Actually, after that, I almost always (99%) either have the fuel truck
come out or hook up to an airport type fuel facility. Decided
transporting and transferring fuel was something I just did not have to
do.
It would probably never happened again - but, once is more than
enough!!!
Ed
From: Jeff Luckey
Sent: Thursday, July 12, 2012 6:34 PM
Subject: RE: AeroElectric-List: grounding procedures
Ed,
Your story scares the s**t out of me (I wonder if the same happened to
you?) but thanks for sharing. After having the advantage of reading
about your experience I think I would change the order of operations a
little:
1.. Before starting refueling operations, make sure fire extinguisher
is where I think it is - perhaps even set it nearby on tarmac
2.. get rid of flaming container in my hands - keep me from catching
on fire
3.. replace fuel cap - keep my airplane/fuel tank from continuing to
burn
4.. go for extinguisher
I think this will become my pre-fueling check-list.
One thing that I do when fueling from plastic containers is, before I
start pouring, touch the airplane (metal airplane) near the fuel cap
while holding the full fuel container in the other hand.
In my little mind this helps equalize any differences in potential among
airframe, fuel container, & me.
-------------------------------------------------------------------------
-------
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Ed
Anderson
Sent: Thursday, July 12, 2012 09:25
Subject: Re: AeroElectric-List: grounding procedures
I was once fueling my Rv-6A out of "Approved" plastic 5 gallon fuel
container. I had a racing funnel with a paper filter cartridge in the
center of the spout. It was a 60F low humidity day with no wind. I had
done this many times before.
This time near the end of the 5 gallon container, I attempted to raise
the bottom of the container higher to get the last of the fuel and broke
connection between the funnel (also plastic) and the fuel container.
There was a "Whomp" of ignition and I found myself with an event on my
hands, to wit:
1. Holding a 5 gallon container with flames out its nozzle
2. Holding a large racing funnel with fuel soaked paper filter blazing
way.
3. Haven been mildly started by the unexpected ignition event - I had
stepped back a pace. This resulting in the funnel I was holding being
pulled from the fuel tank leaving me with flames coming out of the
aircraft fuel tank, flames on the wing surface where I dragged the
emptying funnel from the wing tank opening and flames on the tarmac from
that dripping from the wing.
The first thought after "oh S...t" was not too panic, after which I
quickly
1. Walked approx 15 feet from the aircraft and set down flaming
container and funnel.
2. Ran to my Van for my fire extinuisher - always stored under drives
seat (could not located it)
3. Raced back to the aircraft and brushed off the surface fuel/fire
with a rag.
4. Picked up the wing tank fuel cap and remembered thinking "..this
always worked in science class!" ..slapped to fuel cap into the flaming
opening -which fortuntately worked just like in highschool science class
with test tube and cork.
5. Stomped out the small fire on the tarmac.
Fortunately no damage to anything but my nerves and the funnel and
container.
Even though I had used plastic fuel containers for decades refueling
lawnmowers, etc without ever having an incident - I never used anything
but metal containers aftewards - however, I was later told that the the
breaking of the connection permitted the liquid flow to generated a
static potential difference and it would not have mattered if funnel and
container had been metal - it was the breaking of the connection that
apparently resulting in the conditions that lead to ignition.
FWIW
Ed
From: Robert L. Nuckolls, III
Sent: Thursday, July 12, 2012 11:52 AM
Subject: Re: AeroElectric-List: grounding procedures
At 08:46 PM 7/11/2012, you wrote:
soooooooooooo my tanks are grounded to my engine. am i safe to attach a
wire from my fuel nozzle to my exhaust pipe or does the wire need to go
to the tank filler neck? [that doesn't make sense to me]
bob noffs
The word "grounded" is poorly understood and
in this discussion poorly used. As we've studied
in other conversations, having "lots of grounds"
can be deleterious to system performance in terms
of noised conducted from one system to another.
This static charge thing, like most studies of
physics is an energy management issue. We have
an energy source (motion between dissimilar
materials in close proximity), energy storage
(capacitance - proportional to surface area
of mass carrying a charge), potential pathways
for the two masses to exchange levels of charge,
series resistance of those pathways, and finally
open air gaps in the discharge path were a spark
might form that is surrounded by a flammable mixture.
The legacy hazard from which all these discussions
arise are grounded in the management of charges
stored on LARGE surface areas (air transport/military
aircraft and fuel trucks or underground fueling
systems. BIG numbers in terms of potential energy
to be released in that worrisome air-gap.
I'll refer readers to a couple of documents I've
posted to Aeroelectric.com at
http://tinyurl.com/7et4jj5
These two documents speak to 'modeling' the human
body for the purposes of carrying out standardized
tests for ESD vulnerability. Given the surface
area of adult humans to be on the order of 1.5 to
2 square meters, they are 'modeled' as 100 picofarad
capacitors. Further the ability to conduct a charge
off that 'capacitor' is limited by the average
conductivity of the body between the center of charge
and a discharge point (finger tip) which is modeled
with a 1500 ohm resistor. Now, charge the capacitor up
to various voltages up to 15,000 volts and you have
a repeatable means for generating antagonistic stresses
on some device to be tested for ESD immunity.
The machine model is similar but 200 picofarads and
1 ohm of series resistance. I.e., more surface area
and better conductivity.
Now, what might we think the model would be for a
B-747? LOTS of surface area and metallic structure
which provides very low series resistance. Static
charges between large masses can knock you on your
can.
Getting back to filling puddle jumpers from gas
cans or even fuel trucks . . .
The model for a plastic airplane might consider
a surface area on the order of 1000 picofarads
but what's the series resistance? It's an insulator
with hing series resistance. In my studies
with ESD testing I discovered that the WORST case
instances for testing to human body model (15KV)
VERY LITTLE of the potential energy was dissipated
at the victim . . . that 1500 ohm resistor dissipates
90 plus % of the energy. When dealing with things
like metal airplanes and fuel trucks, the machine
models are in force with something on the order of 1000-2000
pf each and VERY LOW series resistance. Connecting
them together before dragging out the hose MAY
NOT dissipate all their charges to zero . . . but it does
bring them TOGETHER in terms of voltage thus ELIMINATING
a potential of spark through a low series resistance.
I forget the structure of the airplane that started
this discussion but I think we were talking about a
non-conductive hose fitted to a fuel transfer pump.
In this instance, ADDING a low series resistance
conductor along the hose length only increases potential
for energy dissipation in a spark at the end of the
hose. Bringing a potential charge on the airplane and
fuel storage containers together is 99.9% of the
safety issue. Having a very large series resistance
in the potential ignition discharge path is another
risk mitigation move.
I've been reading lengthy discussions about fuel
transfer safety on OBAM aircraft for decades sprinkled
with hangar tales and speculative advice . . .
but never have I seen a study of the physics that
underlie the potential for an ignition accident.
Just consider the millions of cars that get fueled
by ding-a-ling drivers every day without blowing
themselves up. Yes, there are the expected 'news'
stories and security camera videos about the
occasional filling station fire. Shucks even the
Mytbusters made a show out of the notion that cell
phones can trigger explosions or fire.
But even the hallowed Mythbusters failed to
mention the physics . . . much less consider how
HARD it is to initiate an explosion under laboratory
conditions (re: explosion proofing tests on motors
we used to build at Electro-Mech).
Bottom line is that if you don't have a means to
bring the surface charge of a container to the same potential
as the surface of your airplane, then the SAME limitation
is in force for causing a spark at the opening of your
filler cap. I.e. if you can't get a spark at the connection
of a potential equalization wire at the exhaust stack of
your engine, you won't get a spark at the filler cap
either. Potentials generated by flowing fuel are
similarly limited in their ability to conduct the
charge to a 'arc gap'. Consider that the fuel
is in constant motion so any charge the liquid carries
is being continuously dumped into the tank . . .
Where is the 'conductor' that's going to bring
that charge to an arc gap? Flammable hydrocarbons
heavier than gasolines are used as medium for
cooling and INSULATOR in high voltage transformers and
capacitors.
Where does the energy come from, where is it stored,
what is the potential equalization path, what is
the series resistance of that path, is it possible
or even NECESSARY to effect an equalization of
potentials at some point AWAY from the filler cap?
Bottom line is that using the same care you would
exercise in filling your car, boat or lawn mower will
suffice to secure your healthy use of that machine.
Adding prophylactic features willy-nilly without
understanding the physics and design goals may
increase risk as opposed to reducing it. If the
truth were known as to root cause for the anecdotal
fuel transfer fires, most if not all would be due
to carelessness.
Bob . . .
href="http://www.matronics.com/Navigator?AeroElectric-List">http://www.
matronics.com/Navigator?AeroElectric-Listhref="http://forums.matronics.
com">http://forums.matronics.comhref="http://www.matronics.com/contribu
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Checked by AVG - www.avg.com
07/12/12
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