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Grounding question

 
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ogdenk



Joined: 05 Feb 2007
Posts: 34
Location: Syracuse, NY

PostPosted: Thu Oct 19, 2017 7:28 am    Post subject: Grounding question Reply with quote

All,
I have a question/concern regarding a ground return to the battery. I have primed all my parts and skins with the Akzo Nobel 2 part primer, which is awesome stuff though it's a smelly pain to work with. All skin overlaps have been primed on both sides of the overlap, and this stuff is not conductive at all so the only electrical path is through the rivets and the small area of the rivet hole that doesn't always have primer covering it. On the outside of the plane the rivet heads have contact directly with the unprimed skin so it's really the inside skin where there is minimal area in electrical contact.
I am concerned that using the skin as a ground return to the battery may not provide an excellent ground path, especially for the large currents needed for engine cranking. I would really rather not have to run another heavy wire to the front of the airplane for ground, but I will if necessary.
Has anyone else faced this issue and had a problem (or no problem) using the skin as a ground return? Also, where/how have people connected the battery ground to the tailcone skin, do you use a piece of brass or copper buss bar riveted to the bottom skin or something like that?
Thanks for any suggestions!
Kent Ogden
#40710 ultra slow-build Smile


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civengpe



Joined: 14 Feb 2011
Posts: 102

PostPosted: Thu Oct 19, 2017 7:37 am    Post subject: Grounding question Reply with quote

I used a forest of tabs mounted to my firewall with a #2 (I think) cable run from there all the way back to the battery ground in the tailcone.  I'm not sure if it was overkill, but I have had zero issues so far.  

I think the plans ground path is through the skin to the battery tray where you ground the battery.  
http://www.bandc.aero/grounding-supplies-battery-cables.aspx
Shannon 

On Thu, Oct 19, 2017 at 10:27 AM, Kent Ogden <ogdenk(at)upstate.edu (ogdenk(at)upstate.edu)> wrote:
Quote:
All,
I have a question/concern regarding a ground return to the battery.  I have primed all my parts and skins with the Akzo Nobel 2 part primer, which is awesome stuff though it's a smelly pain to work with.  All skin overlaps have been primed on both sides of the overlap, and this stuff is not conductive at all so the only electrical path is through the rivets and the small area of the rivet hole that doesn't always have primer covering it.  On the outside of the plane the rivet heads have contact directly with the unprimed skin so it's really the inside skin where there is minimal area in electrical contact.
I am concerned that using the skin as a ground return to the battery may not provide an excellent ground path, especially for the large currents needed for engine cranking.  I would really rather not have to run another heavy wire to the front of the airplane for ground, but I will if necessary.
Has anyone else faced this issue and had a problem (or no problem) using the skin as a ground return?  Also, where/how have people connected the battery ground to the tailcone skin, do you use a piece of brass or copper buss bar riveted to the bottom skin or something like that?
Thanks for any suggestions!
Kent Ogden
#40710 ultra slow-build Smile




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philperry9



Joined: 23 Nov 2011
Posts: 330

PostPosted: Thu Oct 19, 2017 7:43 am    Post subject: Grounding question Reply with quote

Ditto

Sent from my iPhone

On Oct 19, 2017, at 10:35 AM, Shannon Hicks <civeng123(at)gmail.com (civeng123(at)gmail.com)> wrote:
Quote:
I used a forest of tabs mounted to my firewall with a #2 (I think) cable run from there all the way back to the battery ground in the tailcone. I'm not sure if it was overkill, but I have had zero issues so far.

I think the plans ground path is through the skin to the battery tray where you ground the battery.
http://www.bandc.aero/grounding-supplies-battery-cables.aspx
Shannon

On Thu, Oct 19, 2017 at 10:27 AM, Kent Ogden <ogdenk(at)upstate.edu (ogdenk(at)upstate.edu)> wrote:
Quote:
All,
I have a question/concern regarding a ground return to the battery. I have primed all my parts and skins with the Akzo Nobel 2 part primer, which is awesome stuff though it's a smelly pain to work with. All skin overlaps have been primed on both sides of the overlap, and this stuff is not conductive at all so the only electrical path is through the rivets and the small area of the rivet hole that doesn't always have primer covering it. On the outside of the plane the rivet heads have contact directly with the unprimed skin so it's really the inside skin where there is minimal area in electrical contact.
I am concerned that using the skin as a ground return to the battery may not provide an excellent ground path, especially for the large currents needed for engine cranking. I would really rather not have to run another heavy wire to the front of the airplane for ground, but I will if necessary.
Has anyone else faced this issue and had a problem (or no problem) using the skin as a ground return? Also, where/how have people connected the battery ground to the tailcone skin, do you use a piece of brass or copper buss bar riveted to the bottom skin or something like that?
Thanks for any suggestions!
Kent Ogden
#40710 ultra slow-build Smile






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Dave Saylor



Joined: 11 Jan 2015
Posts: 115
Location: GILROY, CA

PostPosted: Thu Oct 19, 2017 7:52 am    Post subject: Grounding question Reply with quote

Kent,

There are so many rivets making metal-on-metal contact that I can't imagine there'd be any problem, even with primed skins.
If you want a more of a one-piece conductor, you could use one of the long stringers as a return with a flexible conductor on each end.
I like braided ground straps.  Mine is bolted to a vertical member of the baggage floor just forward of the battery.
--Dave
On Thu, Oct 19, 2017 at 8:27 AM, Kent Ogden <ogdenk(at)upstate.edu (ogdenk(at)upstate.edu)> wrote:
Quote:
All,
I have a question/concern regarding a ground return to the battery.  I have primed all my parts and skins with the Akzo Nobel 2 part primer, which is awesome stuff though it's a smelly pain to work with.  All skin overlaps have been primed on both sides of the overlap, and this stuff is not conductive at all so the only electrical path is through the rivets and the small area of the rivet hole that doesn't always have primer covering it.  On the outside of the plane the rivet heads have contact directly with the unprimed skin so it's really the inside skin where there is minimal area in electrical contact.
I am concerned that using the skin as a ground return to the battery may not provide an excellent ground path, especially for the large currents needed for engine cranking.  I would really rather not have to run another heavy wire to the front of the airplane for ground, but I will if necessary.
Has anyone else faced this issue and had a problem (or no problem) using the skin as a ground return?  Also, where/how have people connected the battery ground to the tailcone skin, do you use a piece of brass or copper buss bar riveted to the bottom skin or something like that?
Thanks for any suggestions!
Kent Ogden
#40710 ultra slow-build Smile




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Tim Olson



Joined: 25 Jan 2007
Posts: 2702

PostPosted: Thu Oct 19, 2017 7:59 am    Post subject: Grounding question Reply with quote

+1. I ran an independent #2 ground.

That said, with the number of rivets in the airframe I'm sure you'll be
fine as long as you ground to something with a lot of rivets in it.
I just wanted as low a resistance path to my forest of tabs as
possible.

Tim
On 10/19/2017 10:42 AM, Phillip Perry wrote:
Quote:
Ditto

Sent from my iPhone

On Oct 19, 2017, at 10:35 AM, Shannon Hicks <civeng123(at)gmail.com
<mailto:civeng123(at)gmail.com>> wrote:

> I used a forest of tabs mounted to my firewall with a #2 (I think)
> cable run from there all the way back to the battery ground in the
> tailcone.  I'm not sure if it was overkill, but I have had zero issues
> so far.
>
> I think the plans ground path is through the skin to the battery tray
> where you ground the battery.
>
> http://www.bandc.aero/grounding-supplies-battery-cables.aspx
>
> Shannon
>
> On Thu, Oct 19, 2017 at 10:27 AM, Kent Ogden <ogdenk(at)upstate.edu
> <mailto:ogdenk(at)upstate.edu>> wrote:
>
> All,
>
> I have a question/concern regarding a ground return to the
> battery.  I have primed all my parts and skins with the Akzo Nobel
> 2 part primer, which is awesome stuff though it's a smelly pain to
> work with.  All skin overlaps have been primed on both sides of
> the overlap, and this stuff is not conductive at all so the only
> electrical path is through the rivets and the small area of the
> rivet hole that doesn't always have primer covering it.  On the
> outside of the plane the rivet heads have contact directly with
> the unprimed skin so it's really the inside skin where there is
> minimal area in electrical contact.
>
> I am concerned that using the skin as a ground return to the
> battery may not provide an excellent ground path, especially for
> the large currents needed for engine cranking.  I would really
> rather not have to run another heavy wire to the front of the
> airplane for ground, but I will if necessary.
>
> Has anyone else faced this issue and had a problem (or no problem)
> using the skin as a ground return?  Also, where/how have people
> connected the battery ground to the tailcone skin, do you use a
> piece of brass or copper buss bar riveted to the bottom skin or
> something like that?
>
> Thanks for any suggestions!
>
> Kent Ogden
> #40710 ultra slow-build Smile
>


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Lenny Iszak



Joined: 23 Mar 2008
Posts: 235

PostPosted: Thu Oct 19, 2017 8:37 am    Post subject: Grounding question Reply with quote

I originally ran a #2 wire to the firewall forest of tabs, then realized how much it weighs, promptly ripped it all out and grounded the battery to the battery tray/bellcrank mount (F-1035). It worked out great.

I think it’s more important that you ground everything else to a single point like the forest of tabs on the firewall. I have my tail strobe locally grounded at the end of the tail and it's making a slight audible noise. Everything else is quiet.

Lenny

Quote:
On Oct 19, 2017, at 11:58 AM, Tim Olson <Tim(at)MyRV10.com> wrote:



+1. I ran an independent #2 ground.

That said, with the number of rivets in the airframe I'm sure you'll be fine as long as you ground to something with a lot of rivets in it.
I just wanted as low a resistance path to my forest of tabs as
possible.

Tim


On 10/19/2017 10:42 AM, Phillip Perry wrote:
> Ditto
> Sent from my iPhone
> On Oct 19, 2017, at 10:35 AM, Shannon Hicks <civeng123(at)gmail.com <mailto:civeng123(at)gmail.com>> wrote:
>> I used a forest of tabs mounted to my firewall with a #2 (I think) cable run from there all the way back to the battery ground in the tailcone. I'm not sure if it was overkill, but I have had zero issues so far.
>>
>> I think the plans ground path is through the skin to the battery tray where you ground the battery.
>>
>> http://www.bandc.aero/grounding-supplies-battery-cables.aspx
>>
>> Shannon
>>
>> On Thu, Oct 19, 2017 at 10:27 AM, Kent Ogden <ogdenk(at)upstate.edu <mailto:ogdenk(at)upstate.edu>> wrote:
>>
>> All,
>>
>> I have a question/concern regarding a ground return to the
>> battery. I have primed all my parts and skins with the Akzo Nobel
>> 2 part primer, which is awesome stuff though it's a smelly pain to
>> work with. All skin overlaps have been primed on both sides of
>> the overlap, and this stuff is not conductive at all so the only
>> electrical path is through the rivets and the small area of the
>> rivet hole that doesn't always have primer covering it. On the
>> outside of the plane the rivet heads have contact directly with
>> the unprimed skin so it's really the inside skin where there is
>> minimal area in electrical contact.
>>
>> I am concerned that using the skin as a ground return to the
>> battery may not provide an excellent ground path, especially for
>> the large currents needed for engine cranking. I would really
>> rather not have to run another heavy wire to the front of the
>> airplane for ground, but I will if necessary.
>>
>> Has anyone else faced this issue and had a problem (or no problem)
>> using the skin as a ground return? Also, where/how have people
>> connected the battery ground to the tailcone skin, do you use a
>> piece of brass or copper buss bar riveted to the bottom skin or
>> something like that?
>>
>> Thanks for any suggestions!
>>
>> Kent Ogden
>> #40710 ultra slow-build Smile
>>
>>
>>






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Palm City, FL
2014 RV-10, N311LZ - 300 hrs
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rnewman(at)tcwtech.com
Guest





PostPosted: Thu Oct 19, 2017 8:48 am    Post subject: Grounding question Reply with quote

I used the same Akzo Noble primer on my RV-10, all skins are primed including both sides of all lap joints. ( This primer is amazing stuff, does stink like all heck, but really tough and protective. We’ve used this on the eight airplanes we have built now over more than 20 years now, and can say it has held up extremely well.)
I did not run a separate #2 wire up to the front. All ground current for the starter, alternator and engine sensors flows back through the airframe. I do have a #8 ground wire running from the battery to a ground bus up under the instrument panel solely for the avionics.

I have absolutely no electrical issues or noise problems in this airplane.

Bob Newman
TCW Technologies, LLC
610-928-3420

Quote:
On Oct 19, 2017, at 11:58 AM, Tim Olson <Tim(at)MyRV10.com> wrote:



+1. I ran an independent #2 ground.

That said, with the number of rivets in the airframe I'm sure you'll be fine as long as you ground to something with a lot of rivets in it.
I just wanted as low a resistance path to my forest of tabs as
possible.

Tim


> On 10/19/2017 10:42 AM, Phillip Perry wrote:
> Ditto
> Sent from my iPhone
>> On Oct 19, 2017, at 10:35 AM, Shannon Hicks <civeng123(at)gmail.com <mailto:civeng123(at)gmail.com>> wrote:
>> I used a forest of tabs mounted to my firewall with a #2 (I think) cable run from there all the way back to the battery ground in the tailcone. I'm not sure if it was overkill, but I have had zero issues so far.
>>
>> I think the plans ground path is through the skin to the battery tray where you ground the battery.
>>
>> http://www.bandc.aero/grounding-supplies-battery-cables.aspx
>>
>> Shannon
>>
>> On Thu, Oct 19, 2017 at 10:27 AM, Kent Ogden <ogdenk(at)upstate.edu <mailto:ogdenk(at)upstate.edu>> wrote:
>>
>> All,
>>
>> I have a question/concern regarding a ground return to the
>> battery. I have primed all my parts and skins with the Akzo Nobel
>> 2 part primer, which is awesome stuff though it's a smelly pain to
>> work with. All skin overlaps have been primed on both sides of
>> the overlap, and this stuff is not conductive at all so the only
>> electrical path is through the rivets and the small area of the
>> rivet hole that doesn't always have primer covering it. On the
>> outside of the plane the rivet heads have contact directly with
>> the unprimed skin so it's really the inside skin where there is
>> minimal area in electrical contact.
>>
>> I am concerned that using the skin as a ground return to the
>> battery may not provide an excellent ground path, especially for
>> the large currents needed for engine cranking. I would really
>> rather not have to run another heavy wire to the front of the
>> airplane for ground, but I will if necessary.
>>
>> Has anyone else faced this issue and had a problem (or no problem)
>> using the skin as a ground return? Also, where/how have people
>> connected the battery ground to the tailcone skin, do you use a
>> piece of brass or copper buss bar riveted to the bottom skin or
>> something like that?
>>
>> Thanks for any suggestions!
>>
>> Kent Ogden
>> #40710 ultra slow-build Smile
>>
>>
>>






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Kellym



Joined: 10 Jan 2006
Posts: 1464
Location: Sun Lakes AZ

PostPosted: Thu Oct 19, 2017 1:09 pm    Post subject: Grounding question Reply with quote

The airframe has plenty of surface area to carry any amount of current
you will use.
Running a separate cable from the battery to firewall central grounding
point is a totally wasted effort.
Strobes are a bit different animal if you are talking the old capacitive
discharge into a flash tube variety. They do generate noise that is hard
to totally suppress.
LED strobes don't seem to do that.
I have electrical system from battery to VPX system built to plans, with
grounding cable to frame , in front of battery box.
I have LED nav lights and strobes, all grounded locally, along with Vans
landing lights grounded locally.
The central grounding is essential for electronics that amplify noises
such as intercoms, nav coms etc. It is unnecessary for resistive
electrical loads, as they don't generate RF noise.
My previous aircraft was a Mooney that was built with full zinc chromate
primer, mostly non-structural skin, and chrome-moly tube frame, with
battery behind baggage compartment. It was just fine with ground wire to
airframe at battery. Cessna does the same.

On 10/19/2017 9:35 AM, Lenny Iszak wrote:
Quote:


I originally ran a #2 wire to the firewall forest of tabs, then realized how much it weighs, promptly ripped it all out and grounded the battery to the battery tray/bellcrank mount (F-1035). It worked out great.
R
I think it’s more important that you ground everything else to a single point like the forest of tabs on the firewall. I have my tail strobe locally grounded at the end of the tail and it's making a slight audible noise. Everything else is quiet.

Lenny

> On Oct 19, 2017, at 11:58 AM, Tim Olson <Tim(at)MyRV10.com> wrote:
>
>
>
> +1. I ran an independent #2 ground.
>
> That said, with the number of rivets in the airframe I'm sure you'll be fine as long as you ground to something with a lot of rivets in it.
> I just wanted as low a resistance path to my forest of tabs as
> possible.
>
> Tim
> On 10/19/2017 10:42 AM, Phillip Perry wrote:
>> Ditto
>> Sent from my iPhone
>> On Oct 19, 2017, at 10:35 AM, Shannon Hicks <civeng123(at)gmail.com <mailto:civeng123(at)gmail.com>> wrote:
>>> I used a forest of tabs mounted to my firewall with a #2 (I think) cable run from there all the way back to the battery ground in the tailcone. I'm not sure if it was overkill, but I have had zero issues so far.
>>>
>>> I think the plans ground path is through the skin to the battery tray where you ground the battery.
>>>
>>> http://www.bandc.aero/grounding-supplies-battery-cables.aspx
>>>
>>> Shannon
>>>
>>> On Thu, Oct 19, 2017 at 10:27 AM, Kent Ogden <ogdenk(at)upstate.edu <mailto:ogdenk(at)upstate.edu>> wrote:
>>>
>>> All,
>>>
>>> I have a question/concern regarding a ground return to the
>>> battery. I have primed all my parts and skins with the Akzo Nobel
>>> 2 part primer, which is awesome stuff though it's a smelly pain to
>>> work with. All skin overlaps have been primed on both sides of
>>> the overlap, and this stuff is not conductive at all so the only
>>> electrical path is through the rivets and the small area of the
>>> rivet hole that doesn't always have primer covering it. On the
>>> outside of the plane the rivet heads have contact directly with
>>> the unprimed skin so it's really the inside skin where there is
>>> minimal area in electrical contact.
>>>
>>> I am concerned that using the skin as a ground return to the
>>> battery may not provide an excellent ground path, especially for
>>> the large currents needed for engine cranking. I would really
>>> rather not have to run another heavy wire to the front of the
>>> airplane for ground, but I will if necessary.
>>>
>>> Has anyone else faced this issue and had a problem (or no problem)
>>> using the skin as a ground return? Also, where/how have people
>>> connected the battery ground to the tailcone skin, do you use a
>>> piece of brass or copper buss bar riveted to the bottom skin or
>>> something like that?
>>>
>>> Thanks for any suggestions!
>>>
>>> Kent Ogden
>>> #40710 ultra slow-build Smile
>>>
>>>
>>>
>
>







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Bob Turner



Joined: 03 Jan 2009
Posts: 797
Location: Castro Valley, CA

PostPosted: Thu Oct 19, 2017 1:39 pm    Post subject: Re: Grounding question Reply with quote

As others have said, there should be lots of good metal to metal contact with the rivets - when driven properly, they expand radially against the sides of the holes. But if it worries you, it’s easy to measure. Ground the starter locally, and the same with the negative battery terminal. Run a pair of temporary wires from these locations to a good milli-volt voltmeter in the cockpit. Clear the prop area, and engage the starter. What does the voltmeter read?

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philperry9



Joined: 23 Nov 2011
Posts: 330

PostPosted: Thu Oct 19, 2017 2:10 pm    Post subject: Grounding question Reply with quote

Along that line, it’s important to remember that the conductivity you get today may not be e conductivity you see 3, 5, or 10 years down the road. As corrosion sets in over time, resistance will increase and circuit performance is degrade.

If you’re in a highly corrosive environment like those of us along the gulf coast, it’s probably a wise investment to run a dedicated grounding wire.

We spend way too much time in this area chasing down grounding problems that are frequently caused by corrosion. Often times, they get fixed by running a dedicated ground to whatever device is having problems.

Phil


Sent from my iPhone

Quote:
On Oct 19, 2017, at 4:39 PM, Bob Turner <bobturner(at)alum.rpi.edu> wrote:



As others have said, there should be lots of good metal to metal contact with the rivets - when driven properly, they expand radially against the sides of the holes. But if it worries you, it’s easy to measure. Ground the starter locally, and the same with the negative battery terminal. Run a pair of temporary wires from these locations to a good milli-volt voltmeter in the cockpit. Clear the prop area, and engage the starter. What does the voltmeter read?

--------
Bob Turner
RV-10 QB




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schmoboy



Joined: 26 Feb 2006
Posts: 125

PostPosted: Thu Oct 19, 2017 3:26 pm    Post subject: Grounding question Reply with quote

Same boat here. No run from forest on firewall back to batt. LED nav
and strobe lights locally grounded. No issues with those. But... I do
have crazy noise when my locally grounded HID landing light ballasts
heat up at first. It subsides once the draw rush is over. Thinking of
swapping out for LED landing lights anyways, but have been unable to
make them quiet.

-Sean #40303

Quote:
Kelly McMullen <mailto:kellym(at)aviating.com>
October 19, 2017 at 4:08 PM


The airframe has plenty of surface area to carry any amount of current
you will use.
Running a separate cable from the battery to firewall central
grounding point is a totally wasted effort.
Strobes are a bit different animal if you are talking the old
capacitive discharge into a flash tube variety. They do generate noise
that is hard to totally suppress.
LED strobes don't seem to do that.
I have electrical system from battery to VPX system built to plans,
with grounding cable to frame , in front of battery box.
I have LED nav lights and strobes, all grounded locally, along with
Vans landing lights grounded locally.
The central grounding is essential for electronics that amplify noises
such as intercoms, nav coms etc. It is unnecessary for resistive
electrical loads, as they don't generate RF noise.
My previous aircraft was a Mooney that was built with full zinc
chromate primer, mostly non-structural skin, and chrome-moly tube
frame, with battery behind baggage compartment. It was just fine with
ground wire to airframe at battery. Cessna does the same.



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philperry9



Joined: 23 Nov 2011
Posts: 330

PostPosted: Thu Oct 19, 2017 3:53 pm    Post subject: Grounding question Reply with quote

Just a data point, even with a dedicated ground, my LED nav/strobes did have considerable noise. So much that it required a wholesale replacement of the lights. I didn’t discover it until taxiing our for flight #1, so it became the first item I discovered before I ever left the ground.

Come to find out, it wasn’t a grounding or wiring problem, it was a design problem within the LED. The LED’s I had more pulled current when they were on and less when they were off. This created a surge that also broke the auto-squelch on my GTN750. So every time they fired, the squelch in my headset broke too.

This required a new LED design that had a more linear current flow. So the current would remain constant even in the off cycles. This addressed the auto-squelch on the GTN.

The newer Garmin Nav/Com’s don’t have a squelch knob. They sense the noise floor and then automatically adjust the squelch to match the floor. With a constant current draw the floor became constant again and the squelch became functional again.

Just a word of caution as you go shop LED’s that flash. My were from a very reputable Certified and Experimental lighting provider and not cheapo’s from Napa. It’s good to ask questions about the current flow patterns and not just be current flow; especially if your using newer radios with auto squelch.

Fortunately the provider I used worked with me to make a swap to a newer LED version relatively painless and simple.

Sent from my iPhone

Quote:
On Oct 19, 2017, at 6:23 PM, Sean Stephens <sean(at)stephensville.com> wrote:



Same boat here. No run from forest on firewall back to batt. LED nav and strobe lights locally grounded. No issues with those. But... I do have crazy noise when my locally grounded HID landing light ballasts heat up at first. It subsides once the draw rush is over. Thinking of swapping out for LED landing lights anyways, but have been unable to make them quiet.

-Sean #40303

> Kelly McMullen <mailto:kellym(at)aviating.com>
> October 19, 2017 at 4:08 PM
>
>
> The airframe has plenty of surface area to carry any amount of current you will use.
> Running a separate cable from the battery to firewall central grounding point is a totally wasted effort.
> Strobes are a bit different animal if you are talking the old capacitive discharge into a flash tube variety. They do generate noise that is hard to totally suppress.
> LED strobes don't seem to do that.
> I have electrical system from battery to VPX system built to plans, with grounding cable to frame , in front of battery box.
> I have LED nav lights and strobes, all grounded locally, along with Vans landing lights grounded locally.
> The central grounding is essential for electronics that amplify noises such as intercoms, nav coms etc. It is unnecessary for resistive electrical loads, as they don't generate RF noise.
> My previous aircraft was a Mooney that was built with full zinc chromate primer, mostly non-structural skin, and chrome-moly tube frame, with battery behind baggage compartment. It was just fine with ground wire to airframe at battery. Cessna does the same.
>
>
>
>
>






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Kellym



Joined: 10 Jan 2006
Posts: 1464
Location: Sun Lakes AZ

PostPosted: Thu Oct 19, 2017 3:54 pm    Post subject: Grounding question Reply with quote

If the conductivity of the airframe deteriorates, it means that a *lot*
of rivets were not driven properly and are going to start smoking soon,
if they aren't already. I grant you corrosive environments are
difficult. I sure would want to have a hangar in those locations.

On 10/19/2017 3:08 PM, Phillip Perry wrote:
Quote:


Along that line, it’s important to remember that the conductivity you get today may not be e conductivity you see 3, 5, or 10 years down the road. As corrosion sets in over time, resistance will increase and circuit performance is degrade.

If you’re in a highly corrosive environment like those of us along the gulf coast, it’s probably a wise investment to run a dedicated grounding wire.

We spend way too much time in this area chasing down grounding problems that are frequently caused by corrosion. Often times, they get fixed by running a dedicated ground to whatever device is having problems.

Phil


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philperry9



Joined: 23 Nov 2011
Posts: 330

PostPosted: Thu Oct 19, 2017 4:26 pm    Post subject: Grounding question Reply with quote

That’s why our gulf coast planes tend to be heavier. We soak them in primer! Smile

It’s better here in Waco than when I was in Houston. I don’t miss the rust and corrosion on everything. My hand tools look like trash after years of working down there.

You could use a new tool in the morning and by the next morning it would have rust forming on it.

When we move to Waco, being able to keep bread on the counter more than 4 Days was awesome! Smile

Sent from my iPhone

Quote:
On Oct 19, 2017, at 6:52 PM, Kelly McMullen <kellym(at)aviating.com> wrote:



If the conductivity of the airframe deteriorates, it means that a *lot* of rivets were not driven properly and are going to start smoking soon, if they aren't already. I grant you corrosive environments are difficult. I sure would want to have a hangar in those locations.

> On 10/19/2017 3:08 PM, Phillip Perry wrote:
>
> Along that line, it’s important to remember that the conductivity you get today may not be e conductivity you see 3, 5, or 10 years down the road. As corrosion sets in over time, resistance will increase and circuit performance is degrade.
> If you’re in a highly corrosive environment like those of us along the gulf coast, it’s probably a wise investment to run a dedicated grounding wire.
> We spend way too much time in this area chasing down grounding problems that are frequently caused by corrosion. Often times, they get fixed by running a dedicated ground to whatever device is having problems.
> Phil





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PostPosted: Fri Oct 20, 2017 12:40 am    Post subject: Grounding question Reply with quote

Philip

Can you share the brand and supplier of your new LED lights?

Thanks
Carlos

Enviado do meu iPhone

No dia 20/10/2017, às 00:52, Phillip Perry <philperry9(at)gmail.com> escreveu:

Quote:


Just a data point, even with a dedicated ground, my LED nav/strobes did have considerable noise. So much that it required a wholesale replacement of the lights. I didn’t discover it until taxiing our for flight #1, so it became the first item I discovered before I ever left the ground.

Come to find out, it wasn’t a grounding or wiring problem, it was a design problem within the LED. The LED’s I had more pulled current when they were on and less when they were off. This created a surge that also broke the auto-squelch on my GTN750. So every time they fired, the squelch in my headset broke too.

This required a new LED design that had a more linear current flow. So the current would remain constant even in the off cycles. This addressed the auto-squelch on the GTN.

The newer Garmin Nav/Com’s don’t have a squelch knob. They sense the noise floor and then automatically adjust the squelch to match the floor. With a constant current draw the floor became constant again and the squelch became functional again.

Just a word of caution as you go shop LED’s that flash. My were from a very reputable Certified and Experimental lighting provider and not cheapo’s from Napa. It’s good to ask questions about the current flow patterns and not just be current flow; especially if your using newer radios with auto squelch.

Fortunately the provider I used worked with me to make a swap to a newer LED version relatively painless and simple.



Sent from my iPhone

> On Oct 19, 2017, at 6:23 PM, Sean Stephens <sean(at)stephensville.com> wrote:
>
>
>
> Same boat here. No run from forest on firewall back to batt. LED nav and strobe lights locally grounded. No issues with those. But... I do have crazy noise when my locally grounded HID landing light ballasts heat up at first. It subsides once the draw rush is over. Thinking of swapping out for LED landing lights anyways, but have been unable to make them quiet.
>
> -Sean #40303
>
>> Kelly McMullen <mailto:kellym(at)aviating.com>
>> October 19, 2017 at 4:08 PM
>>
>>
>> The airframe has plenty of surface area to carry any amount of current you will use.
>> Running a separate cable from the battery to firewall central grounding point is a totally wasted effort.
>> Strobes are a bit different animal if you are talking the old capacitive discharge into a flash tube variety. They do generate noise that is hard to totally suppress.
>> LED strobes don't seem to do that.
>> I have electrical system from battery to VPX system built to plans, with grounding cable to frame , in front of battery box.
>> I have LED nav lights and strobes, all grounded locally, along with Vans landing lights grounded locally.
>> The central grounding is essential for electronics that amplify noises such as intercoms, nav coms etc. It is unnecessary for resistive electrical loads, as they don't generate RF noise.
>> My previous aircraft was a Mooney that was built with full zinc chromate primer, mostly non-structural skin, and chrome-moly tube frame, with battery behind baggage compartment. It was just fine with ground wire to airframe at battery. Cessna does the same.
>>
>>
>>
>>
>>
>
>
>
>






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PostPosted: Fri Oct 20, 2017 7:56 am    Post subject: Grounding question Reply with quote

Learn something every day - what kind of LED lighting device pulls the same current when off as it does when on, and why would we want it to do so?  Please explain.

On Fri, Oct 20, 2017 at 3:59 AM, Carlos Trigo <trigo(at)mail.telepac.pt (trigo(at)mail.telepac.pt)> wrote:
Quote:
--> RV10-List message posted by: Carlos Trigo <trigo(at)mail.telepac.pt (trigo(at)mail.telepac.pt)>

Philip

Can you share the brand and supplier of your new LED lights?

Thanks
Carlos

Enviado do meu iPhone

No dia 20/10/2017, às 00:52, Phillip Perry <philperry9(at)gmail.com (philperry9(at)gmail.com)> escreveu:

> --> RV10-List message posted by: Phillip Perry <philperry9(at)gmail.com (philperry9(at)gmail.com)>
>
> Just a data point, even with a dedicated ground, my LED nav/strobes did have considerable noise.  So much that it required a wholesale replacement of the lights.  I didn’t discover it until taxiing our for flight #1, so it became the first item I discovered before I ever left the ground.
>
> Come to find out, it wasn’t a grounding or wiring problem, it was a design problem within the LED.   The LED’s I had more pulled current when they were on and less when they were off.  This created a surge that also broke the auto-squelch on my GTN750.   So every time they fired, the squelch in my headset broke too.
>
> This required a new LED design that had a more linear current flow.   So the current would remain constant even in the off cycles.    This addressed the auto-squelch on the GTN.
>
> The newer Garmin Nav/Com’s don’t have a squelch knob.   They sense the noise floor and then automatically adjust the squelch to match the floor.    With a constant current draw the floor became constant again and the squelch became functional again.
>
> Just a word of caution as you go shop LED’s that flash.   My were from a very reputable Certified and Experimental lighting provider and not cheapo’s from Napa.  It’s good to ask questions about the current flow patterns and not just be current flow; especially if your using newer radios with auto squelch.
>
> Fortunately the provider I used worked with me to make a swap to a newer LED version relatively painless and simple.
>
>
>
> Sent from my iPhone
>
>> On Oct 19, 2017, at 6:23 PM, Sean Stephens <sean(at)stephensville.com (sean(at)stephensville.com)> wrote:
>>
>> --> RV10-List message posted by: Sean Stephens <sean(at)stephensville.com (sean(at)stephensville.com)>
>>
>> Same boat here.  No run from forest on firewall back to batt.  LED nav and strobe lights locally grounded.  No issues with those.  But... I do have crazy noise when my locally grounded HID landing light ballasts heat up at first.  It subsides once the draw rush is over.  Thinking of swapping out for LED landing lights anyways, but have been unable to make them quiet.
>>
>> -Sean #40303
>>
>>> Kelly McMullen <mailto:kellym(at)aviating.com (kellym(at)aviating.com)>
>>> October 19, 2017 at 4:08 PM
>>> --> RV10-List message posted by: Kelly McMullen <kellym(at)aviating.com (kellym(at)aviating.com)>
>>>
>>> The airframe has plenty of surface area to carry any amount of current you will use.
>>> Running a separate cable from the battery to firewall central grounding point is a totally wasted effort.
>>> Strobes are a bit different animal if you are talking the old capacitive discharge into a flash tube variety. They do generate noise that is hard to totally suppress.
>>> LED strobes don't seem to do that.
>>> I have electrical system from battery to VPX system built to plans, with grounding cable to frame , in front of battery box.
>>> I have LED nav lights and strobes, all grounded locally, along with Vans landing lights grounded locally.
>>> The central grounding is essential for electronics that amplify noises such as intercoms, nav coms etc. It is unnecessary for resistive electrical loads, as they don't generate RF noise.
>>> My previous aircraft was a Mooney that was built with full zinc chromate primer, mostly non-structural skin, and chrome-moly tube frame, with battery behind baggage compartment. It was just fine with ground wire to airframe at battery. Cessna does the same.
>>>
>>>
>>>
>>>
>>>
>>
>>
>>
>>
>
>
>
>


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philperry9



Joined: 23 Nov 2011
Posts: 330

PostPosted: Fri Oct 20, 2017 9:10 am    Post subject: Grounding question Reply with quote

When I went through it, it they referred to it is a linear current flow.
Sent from my iPhone

On Oct 20, 2017, at 10:54 AM, Bill Boyd <sportav8r(at)gmail.com (sportav8r(at)gmail.com)> wrote:
Quote:
Learn something every day - what kind of LED lighting device pulls the same current when off as it does when on, and why would we want it to do so? Please explain.

On Fri, Oct 20, 2017 at 3:59 AM, Carlos Trigo <trigo(at)mail.telepac.pt (trigo(at)mail.telepac.pt)> wrote:
Quote:
--> RV10-List message posted by: Carlos Trigo <trigo(at)mail.telepac.pt (trigo(at)mail.telepac.pt)>

Philip

Can you share the brand and supplier of your new LED lights?

Thanks
Carlos

Enviado do meu iPhone

No dia 20/10/2017, às 00:52, Phillip Perry <philperry9(at)gmail.com (philperry9(at)gmail.com)> escreveu:

> --> RV10-List message posted by: Phillip Perry <philperry9(at)gmail.com (philperry9(at)gmail.com)>
>
> Just a data point, even with a dedicated ground, my LED nav/strobes did have considerable noise. So much that it required a wholesale replacement of the lights. I didn’t discover it until taxiing our for flight #1, so it became the first item I discovered before I ever left the ground.
>
> Come to find out, it wasn’t a grounding or wiring problem, it was a design problem within the LED. The LED’s I had more pulled current when they were on and less when they were off. This created a surge that also broke the auto-squelch on my GTN750. So every time they fired, the squelch in my headset broke too.
>
> This required a new LED design that had a more linear current flow. So the current would remain constant even in the off cycles. This addressed the auto-squelch on the GTN.
>
> The newer Garmin Nav/Com’s don’t have a squelch knob. They sense the noise floor and then automatically adjust the squelch to match the floor. With a constant current draw the floor became constant again and the squelch became functional again.
>
> Just a word of caution as you go shop LED’s that flash. My were from a very reputable Certified and Experimental lighting provider and not cheapo’s from Napa. It’s good to ask questions about the current flow patterns and not just be current flow; especially if your using newer radios with auto squelch.
>
> Fortunately the provider I used worked with me to make a swap to a newer LED version relatively painless and simple.
>
>
>
> Sent from my iPhone
>
>> On Oct 19, 2017, at 6:23 PM, Sean Stephens <sean(at)stephensville.com (sean(at)stephensville.com)> wrote:
>>
>> --> RV10-List message posted by: Sean Stephens <sean(at)stephensville.com (sean(at)stephensville.com)>
>>
>> Same boat here. No run from forest on firewall back to batt. LED nav and strobe lights locally grounded. No issues with those. But... I do have crazy noise when my locally grounded HID landing light ballasts heat up at first. It subsides once the draw rush is over. Thinking of swapping out for LED landing lights anyways, but have been unable to make them quiet.
>>
>> -Sean #40303
>>
>>> Kelly McMullen <mailto:kellym(at)aviating.com (kellym(at)aviating.com)>
>>> October 19, 2017 at 4:08 PM
>>> --> RV10-List message posted by: Kelly McMullen <kellym(at)aviating.com (kellym(at)aviating.com)>
>>>
>>> The airframe has plenty of surface area to carry any amount of current you will use.
>>> Running a separate cable from the battery to firewall central grounding point is a totally wasted effort.
>>> Strobes are a bit different animal if you are talking the old capacitive discharge into a flash tube variety. They do generate noise that is hard to totally suppress.
>>> LED strobes don't seem to do that.
>>> I have electrical system from battery to VPX system built to plans, with grounding cable to frame , in front of battery box.
>>> I have LED nav lights and strobes, all grounded locally, along with Vans landing lights grounded locally.
>>> The central grounding is essential for electronics that amplify noises such as intercoms, nav coms etc. It is unnecessary for resistive electrical loads, as they don't generate RF noise.
>>> My previous aircraft was a Mooney that was built with full zinc chromate primer, mostly non-structural skin, and chrome-moly tube frame, with battery behind baggage compartment. It was just fine with ground wire to airframe at battery. Cessna does the same.
>>>
>>>
>>>
>>>
>>>
>>
>>
>>
>>
>
>
>
>


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PostPosted: Fri Oct 20, 2017 10:52 am    Post subject: Grounding question Reply with quote

Hi Kent and everyone.

In my opinion you don't need to rum a ground cable to your battery, I
read very good advices regarding that to your answer.

If you allow me; OUT of your question but INSIDE the ground subject

For your instruments and every other equipment that needs power.

Run three ground wires (all of them direct from battery) not from the
point you grounded your battery.

MASTER GROUND - This ground should be used to every electrically "dirt"
instruments or lights - IF you have real noisy and pulsing strobos I'd
consider to have an extra "REALY DIRT MASTER GROUND" also tied directly
to battery.

AUDIO INSTRUMENT GROUND - It's only for those instruments related to
audio signals (a transponder should not be tied here, the same for the
glasses instruments - such as PFDs, MFDs and Skyview screens)

AUDIO GROUND - Used only and only, to ground audio signals and its
shields. When running ground connections it's highly recommended to run
these connections instrument to instrument. I mean, run a wire from the
radio ground up to the audio panel, the same for every other ground
signal. if he audio panel connector doesn't have have enough pins tie
all those grounds to a common wire and that wire to the audio unit.

Also insulate from the air frame the ground of the headsets connector.

The general idea is always lay down your wiring as a star. Regarding to
ground your battery is the center of you galaxy Smile

I'm ware that seems to be to much, but it isn't, doing that you will
listen only the sounds that mater.

Best Regards

Dilson

Em 19/10/2017 19:08, Kelly McMullen escreveu:
Quote:


The airframe has plenty of surface area to carry any amount of current
you will use.
Running a separate cable from the battery to firewall central
grounding point is a totally wasted effort.
Strobes are a bit different animal if you are talking the old
capacitive discharge into a flash tube variety. They do generate noise
that is hard to totally suppress.
LED strobes don't seem to do that.
I have electrical system from battery to VPX system built to plans,
with grounding cable to frame , in front of battery box.
I have LED nav lights and strobes, all grounded locally, along with
Vans landing lights grounded locally.
The central grounding is essential for electronics that amplify noises
such as intercoms, nav coms etc. It is unnecessary for resistive
electrical loads, as they don't generate RF noise.
My previous aircraft was a Mooney that was built with full zinc
chromate primer, mostly non-structural skin, and chrome-moly tube
frame, with battery behind baggage compartment. It was just fine with
ground wire to airframe at battery. Cessna does the same.

On 10/19/2017 9:35 AM, Lenny Iszak wrote:
>
>
> I originally ran a #2 wire to the firewall forest of tabs, then
> realized how much it weighs, promptly ripped it all out and grounded
> the battery to the battery tray/bellcrank mount (F-1035). It worked
> out great.
> R
> I think it’s more important that you ground everything else to a
> single point like the forest of tabs on the firewall. I have my tail
> strobe locally grounded at the end of the tail and it's making a
> slight audible noise. Everything else is quiet.
>
> Lenny
>
>> On Oct 19, 2017, at 11:58 AM, Tim Olson <Tim(at)MyRV10.com> wrote:
>>
>>
>>
>> +1.   I ran an independent #2 ground.
>>
>> That said, with the number of rivets in the airframe I'm sure you'll
>> be fine as long as you ground to something with a lot of rivets in it.
>> I just wanted as low a resistance path to my forest of tabs as
>> possible.
>>
>> Tim
>>
>>
>> On 10/19/2017 10:42 AM, Phillip Perry wrote:
>>> Ditto
>>> Sent from my iPhone
>>> On Oct 19, 2017, at 10:35 AM, Shannon Hicks <civeng123(at)gmail.com
>>> <mailto:civeng123(at)gmail.com>> wrote:
>>>> I used a forest of tabs mounted to my firewall with a #2 (I think)
>>>> cable run from there all the way back to the battery ground in the
>>>> tailcone.  I'm not sure if it was overkill, but I have had zero
>>>> issues so far.
>>>>
>>>> I think the plans ground path is through the skin to the battery
>>>> tray where you ground the battery.
>>>>
>>>> http://www.bandc.aero/grounding-supplies-battery-cables.aspx
>>>>
>>>> Shannon
>>>>
>>>> On Thu, Oct 19, 2017 at 10:27 AM, Kent Ogden <ogdenk(at)upstate.edu
>>>> <mailto:ogdenk(at)upstate.edu>> wrote:
>>>>
>>>>     All,
>>>>
>>>>     I have a question/concern regarding a ground return to the
>>>>     battery.  I have primed all my parts and skins with the Akzo
>>>> Nobel
>>>>     2 part primer, which is awesome stuff though it's a smelly
>>>> pain to
>>>>     work with.  All skin overlaps have been primed on both sides of
>>>>     the overlap, and this stuff is not conductive at all so the only
>>>>     electrical path is through the rivets and the small area of the
>>>>     rivet hole that doesn't always have primer covering it.  On the
>>>>     outside of the plane the rivet heads have contact directly with
>>>>     the unprimed skin so it's really the inside skin where there is
>>>>     minimal area in electrical contact.
>>>>
>>>>     I am concerned that using the skin as a ground return to the
>>>>     battery may not provide an excellent ground path, especially for
>>>>     the large currents needed for engine cranking.  I would really
>>>>     rather not have to run another heavy wire to the front of the
>>>>     airplane for ground, but I will if necessary.
>>>>
>>>>     Has anyone else faced this issue and had a problem (or no
>>>> problem)
>>>>     using the skin as a ground return?  Also, where/how have people
>>>>     connected the battery ground to the tailcone skin, do you use a
>>>>     piece of brass or copper buss bar riveted to the bottom skin or
>>>>     something like that?
>>>>
>>>>     Thanks for any suggestions!
>>>>
>>>>     Kent Ogden
>>>>     #40710 ultra slow-build Smile
>>>>
>>>>
>>>>
>>
>>
>>
>>
>



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Joined: 03 Jan 2009
Posts: 797
Location: Castro Valley, CA

PostPosted: Fri Oct 20, 2017 12:23 pm    Post subject: Re: Grounding question Reply with quote

sportav8r(at)gmail.com wrote:
Learn something every day - what kind of LED lighting device pulls the same current when off as it does when on, and why would we want it to do so?  Please explain.

[/quote]
You cannot just hook an LED up to 12 volts; it will pull a huge current and quickly overheat and fail. For low power lights (like panel) a dropping resistor is used. Very simple and easy, but 90% of the energy ends up in the resistor. Okay for low power lights, but not for position or landing lights. There, something more sophisticated is needed. The usual solution is to pulse the lights on/off, faster than your eye can see, to limit the power and heat build up. Those pulses can radiate RF and cause interference to other electronics. Some circuits add "smoothing" downstream to limit the RF, and provide a lower average current to the LED. So the LED has some average current thru it, while the power supply is pulsed.


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