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Phil.Perry(at)netapp.com
Guest

Posted: Sun Aug 30, 2009 4:58 pm Post subject: Grounding Questions

I’m in the process of trying to layout my electrical system on paper and in my head.  

   

Probably the best place to start is with the grounding system.  I really don’t like the idea of routing current through the airframe and would prefer to ground everything back to a block.  

   

Here is where I think I’m headed.  

   

<![if !supportLists]>1)      <![endif]>Run a line directly from the (-) Terminal of the battery forward to the firewall.  

<![if !supportLists]>a.       <![endif]>Attach this line to a “Forest of Tab”  on the interior side of the firewall.  Ground everything forward of the baggage compartment to this spot.  

<![if !supportLists]>b.      <![endif]>Jump through the firewall on the other side and ground all FWF items to the “Forest of Tab” on the FWF side.  

<![if !supportLists]>c.       <![endif]>I’ll also ground the crank case at this point too.

 

   

<![if !supportLists]>2)      <![endif]>Run a line directly from the (-) Terminal of the battery to the left wing tip and install a Forest out there too…..  

<![if !supportLists]>a.       <![endif]>Install a similar setup for NAV, Strobe, Taxi/Landing, Pitot heat, Aileron Trim, Stall Warning, etc……

 

   

<![if !supportLists]>3)      <![endif]>Run a line directly from the (-) Terminal of the battery to the right wing tip and install a Forest.  

<![if !supportLists]>a.       <![endif]>Repeat the left side setup of grounding on the wing items on the right side.

 

   

<![if !supportLists]>4)      <![endif]>Run a line directly from the (-) Terminal of the battery  to a “Forest of Tabs” located beside the battery box.  

<![if !supportLists]>a.       <![endif]>This is for the point for grounding all tailcone electronics.  NAV, Rudder Trim Servo, Elevator Servo, and any other electronic devices that end up aft of the baggage compartment.  

   

How have you designed your grounding system?  Grounding issues can be a pain to chase down, so that’s the reason I’m really wanting to spend the time designing a system that is pretty robust and easy to trace.  

   

Thanks,  

Phil  

   

   

      [quote][b]

pitts_pilot(at)bellsouth.
Guest

Posted: Sun Aug 30, 2009 5:22 pm Post subject: Grounding Questions

Perry, Phil wrote:

 	  Quote: 	
		   I’m in the process of trying to layout my electrical system on paper and 

 in my head.

 

  

 

 Probably the best place to start is with the grounding system.  I really 

 don’t like the idea of routing current through the airframe and would 

 prefer to ground everything back to a block.

 

  

 

 Here is where I think I’m headed.

 

  

 

 1)      Run a line directly from the (-) Terminal of the battery forward 

 to the firewall.

 

 a.       Attach this line to a “Forest of Tab”  on the interior side of 

 the firewall.  Ground everything forward of the baggage compartment to 

 this spot.

My only comment would be to mount the 'forest of tabs' on the sub-panel 
	


where it's access is better than the firewall.  You never know when 

you'll add something!

 	  Quote: 	
		   

 b.      Jump through the firewall on the other side and ground all FWF 

 items to the “Forest of Tab” on the FWF side.

 

 c.       I’ll also ground the crank case at this point too.

 

 2)      Run a line directly from the (-) Terminal of the battery to the 

 left wing tip and install a Forest out there too…..

 

 a.       Install a similar setup for NAV, Strobe, Taxi/Landing, Pitot 

 heat, Aileron Trim, Stall Warning, etc……

 

 3)      Run a line directly from the (-) Terminal of the battery to the 

 right wing tip and install a Forest.

 

 a.       Repeat the left side setup of grounding on the wing items on 

 the right side.

 

 4)      Run a line directly from the (-) Terminal of the battery  to a 

 “Forest of Tabs” located beside the battery box.

 

 a.       This is for the point for grounding all tailcone electronics.  

 NAV, Rudder Trim Servo, Elevator Servo, and any other electronic devices 

 that end up aft of the baggage compartment.


	


I can't really find anything 'wrong' with doing things this way with the 

exception of electronic AHRS and Compass mounted back there.  They 

should have a ground wire going back to the ground point of your 

electronics.  The ground potential COULD be different and cause 

problems, but for strobes and lamps etc. I see no reason not to use a 

forest of tabs here.

 	  Quote: 	
		   

  

 

 How have you designed your grounding system?  Grounding issues can be a 

 pain to chase down, so that’s the reason I’m really wanting to spend the 

 time designing a system that is pretty robust and easy to trace.


	


You pretty much have your grounding system laid out like mine is.

Linn



 	  Quote: 	
		   

  

 

 Thanks,

 

 Phil

 

  

 

  

 

 *

 

 

 *

jesse(at)saintaviation.co
Guest

Posted: Sun Aug 30, 2009 5:47 pm Post subject: Grounding Questions

Are all of these Forests of Tabs going to be isolated from airframe (except at the firewall)?  If so, where will your main airframe ground be?  I assume at the firewall.  If not, with wires from the battery negative post to airframe at all of these points, would that introduce more ground loop possibilities in the airframe, with the ground being able to go through the airframe or through the wire back to the battery?  Just curious.  I just remember from my research that giving the ground two possible options/paths can cause more noise in the system.



do not archive



 Jesse Saint

Saint Aviation, Inc.

jesse(at)saintaviation.com (jesse(at)saintaviation.com)

Cell: 352-427-0285

Fax: 815-377-3694



 



On Aug 30, 2009, at 8:53 PM, Perry, Phil wrote:

 	  Quote: 	
		  I’m in the process of trying to layout my electrical system on paper and in my head.

 

Probably the best place to start is with the grounding system.  I really don’t like the idea of routing current through the airframe and would prefer to ground everything back to a block.

 

Here is where I think I’m headed.

 

1)      Run a line directly from the (-) Terminal of the battery forward to the firewall.

a.       Attach this line to a “Forest of Tab”  on the interior side of the firewall.  Ground everything forward of the baggage compartment to this spot.

b.      Jump through the firewall on the other side and ground all FWF items to the “Forest of Tab” on the FWF side.

c.       I’ll also ground the crank case at this point too.

2)      Run a line directly from the (-) Terminal of the battery to the left wing tip and install a Forest out there too…..

a.       Install a similar setup for NAV, Strobe, Taxi/Landing, Pitot heat, Aileron Trim, Stall Warning, etc……

3)      Run a line directly from the (-) Terminal of the battery to the right wing tip and install a Forest.

a.       Repeat the left side setup of grounding on the wing items on the right side.

4)      Run a line directly from the (-) Terminal of the battery  to a “Forest of Tabs” located beside the battery box.

a.       This is for the point for grounding all tailcone electronics.  NAV, Rudder Trim Servo, Elevator Servo, and any other electronic devices that end up aft of the baggage compartment.

 

How have you designed your grounding system?  Grounding issues can be a pain to chase down, so that’s the reason I’m really wanting to spend the time designing a system that is pretty robust and easy to trace.

 

Thanks,

Phil

 

 



 	  Quote: 	
		  



style="color: blue; text-decoration: underline; ">http://www.matronics.com/Navigator?RV10-List

blue; text-decoration: underline; ">http://forums.matronics.com

style="color: blue; text-decoration: underline; ">http://www.matronics.com/contribution



	


	


 [quote][b]

carl.froehlich(at)verizon
Guest

Posted: Sun Aug 30, 2009 6:13 pm Post subject: Grounding Questions

Phil,  

   

Some thoughts:  

<![if !supportLists]>1.      <![endif]> The only thing on the engine that needs a hefty ground is the starter.  Run your ground wire from the same bolt that goes through the firewall to the nice ground lug on the starter (a number #4 wire works well).  On the same starter ground lug do a jumper (like a ground strap or perhaps a piece of #6 wire) to the mounting bolts on the alternator.  This way you have an excellent ground path for both the starter and the alternator.   

<![if !supportLists]>2.      <![endif]>I plan on two Odyssey PC625 batteries in my RV-10 (that is what I’m running in my 8A).  These will be enable split bus operation in the event of a failure of one side or the other.  If you plan on split power supplies, keep in mind a single ground wire that connect both battery grounds to a single point defeats the purpose of having redundant power supplies.  Run a single common  #2 or  #4 wire that connects both battery grounds to the firewall bolt discussed above (this is the starter ground and half of the panel ground).  Run another #10 wire ground from both batteries to another “forest of tabs” on the firewall.  Split the panel ground paths between them consistent with how you are splitting the power distribution.  The objective is to not allow a single failure point (the firewall ground lug) take down your entire panel.   

<![if !supportLists]>3.      <![endif]>Typically a single #14 ground wire is sufficient as a common ground for each wing.  You may want to run another #14 ground to the pitot heat if it draws a lot of current.  Ground these on the same firewall lug that you have the starter on (on the cabin side).  You don’t need a forest of tabs in the wing, just solder pigtails onto the single #14 wire that go to each component.  Do the same type of pigtail for all tail cone grounds.  

   

Carl\  

       

From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of Perry, Phil

 Sent: Sunday, August 30, 2009 8:54 PM

 To: rv10-list(at)matronics.com

 Subject: Grounding Questions  

  

  

   

I’m in the process of trying to layout my electrical system on paper and in my head.  

   

Probably the best place to start is with the grounding system.  I really don’t like the idea of routing current through the airframe and would prefer to ground everything back to a block.  

   

Here is where I think I’m headed.  

   

<![if !supportLists]>1)      <![endif]>Run a line directly from the (-) Terminal of the battery forward to the firewall.  

<![if !supportLists]>a.       <![endif]>Attach this line to a “Forest of Tab”  on the interior side of the firewall.  Ground everything forward of the baggage compartment to this spot.  

<![if !supportLists]>b.      <![endif]>Jump through the firewall on the other side and ground all FWF items to the “Forest of Tab” on the FWF side.  

<![if !supportLists]>c.       <![endif]>I’ll also ground the crank case at this point too.  

<![if !supportLists]>2)      <![endif]>Run a line directly from the (-) Terminal of the battery to the left wing tip and install a Forest out there too…..  

<![if !supportLists]>a.       <![endif]>Install a similar setup for NAV, Strobe, Taxi/Landing, Pitot heat, Aileron Trim, Stall Warning, etc……  

<![if !supportLists]>3)      <![endif]>Run a line directly from the (-) Terminal of the battery to the right wing tip and install a Forest.  

<![if !supportLists]>a.       <![endif]>Repeat the left side setup of grounding on the wing items on the right side.  

<![if !supportLists]>4)      <![endif]>Run a line directly from the (-) Terminal of the battery  to a “Forest of Tabs” located beside the battery box.  

<![if !supportLists]>a.       <![endif]>This is for the point for grounding all tailcone electronics.  NAV, Rudder Trim Servo, Elevator Servo, and any other electronic devices that end up aft of the baggage compartment.  

   

How have you designed your grounding system?  Grounding issues can be a pain to chase down, so that’s the reason I’m really wanting to spend the time designing a system that is pretty robust and easy to trace.  

   

Thanks,  

Phil  

   

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Phil.Perry(at)netapp.com
Guest

Posted: Mon Aug 31, 2009 11:21 am Post subject: Grounding Questions

I think I see what you’re saying Carl.  

   

You’re basically suggesting that I ground everything to the forest of tabs behind the panel, but make a heavier run to each wingtip and ground to those.  Basically a start topology…  Right?  

   

Phil  

   

   

       

From: Carl Froehlich [mailto:carl.froehlich(at)verizon.net] 

 Sent: Sunday, August 30, 2009 9:09 PM

 To: rv10-list(at)matronics.com

 Subject: RE: Grounding Questions  

  

  

   

Phil,  

   

Some thoughts:  

<![if !supportLists]>1.      <![endif]> The only thing on the engine that needs a hefty ground is the starter.  Run your ground wire from the same bolt that goes through the firewall to the nice ground lug on the starter (a number #4 wire works well).  On the same starter ground lug do a jumper (like a ground strap or perhaps a piece of #6 wire) to the mounting bolts on the alternator.  This way you have an excellent ground path for both the starter and the alternator.   

<![if !supportLists]>2.      <![endif]>I plan on two Odyssey PC625 batteries in my RV-10 (that is what I’m running in my 8A).  These will be enable split bus operation in the event of a failure of one side or the other.  If you plan on split power supplies, keep in mind a single ground wire that connect both battery grounds to a single point defeats the purpose of having redundant power supplies.  Run a single common  #2 or  #4 wire that connects both battery grounds to the firewall bolt discussed above (this is the starter ground and half of the panel ground).  Run another #10 wire ground from both batteries to another “forest of tabs” on the firewall.  Split the panel ground paths between them consistent with how you are splitting the power distribution.  The objective is to not allow a single failure point (the firewall ground lug) take down your entire panel.   

<![if !supportLists]>3.      <![endif]>Typically a single #14 ground wire is sufficient as a common ground for each wing.  You may want to run another #14 ground to the pitot heat if it draws a lot of current.  Ground these on the same firewall lug that you have the starter on (on the cabin side).  You don’t need a forest of tabs in the wing, just solder pigtails onto the single #14 wire that go to each component.  Do the same type of pigtail for all tail cone grounds.  

   

Carl\  

       

From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of Perry, Phil

 Sent: Sunday, August 30, 2009 8:54 PM

 To: rv10-list(at)matronics.com

 Subject: Grounding Questions  

  

  

   

I’m in the process of trying to layout my electrical system on paper and in my head.  

   

Probably the best place to start is with the grounding system.  I really don’t like the idea of routing current through the airframe and would prefer to ground everything back to a block.  

   

Here is where I think I’m headed.  

   

<![if !supportLists]>1)      <![endif]>Run a line directly from the (-) Terminal of the battery forward to the firewall.  

<![if !supportLists]>a.       <![endif]>Attach this line to a “Forest of Tab”  on the interior side of the firewall.  Ground everything forward of the baggage compartment to this spot.  

<![if !supportLists]>b.      <![endif]>Jump through the firewall on the other side and ground all FWF items to the “Forest of Tab” on the FWF side.  

<![if !supportLists]>c.       <![endif]>I’ll also ground the crank case at this point too.  

<![if !supportLists]>2)      <![endif]>Run a line directly from the (-) Terminal of the battery to the left wing tip and install a Forest out there too…..  

<![if !supportLists]>a.       <![endif]>Install a similar setup for NAV, Strobe, Taxi/Landing, Pitot heat, Aileron Trim, Stall Warning, etc……  

<![if !supportLists]>3)      <![endif]>Run a line directly from the (-) Terminal of the battery to the right wing tip and install a Forest.  

<![if !supportLists]>a.       <![endif]>Repeat the left side setup of grounding on the wing items on the right side.  

<![if !supportLists]>4)      <![endif]>Run a line directly from the (-) Terminal of the battery  to a “Forest of Tabs” located beside the battery box.  

<![if !supportLists]>a.       <![endif]>This is for the point for grounding all tailcone electronics.  NAV, Rudder Trim Servo, Elevator Servo, and any other electronic devices that end up aft of the baggage compartment.  

   

How have you designed your grounding system?  Grounding issues can be a pain to chase down, so that’s the reason I’m really wanting to spend the time designing a system that is pretty robust and easy to trace.  

   

Thanks,  

Phil  

   

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flysrv10(at)gmail.com
Guest

Posted: Mon Aug 31, 2009 1:25 pm Post subject: Grounding Questions

Have a dedicated ground for all your radio/gps equipment and ground

everything including the headset jacks back to this point.  Make sure

that you use the washer with shoulder (comes with the jacks) to

isolate the headset jacks from the airframe ground.



On Sun, Aug 30, 2009 at 8:53 PM, Perry, Phil<Phil.Perry(at)netapp.com> wrote:

 	  Quote: 	
		   I’m in the process of trying to layout my electrical system on paper and in

 my head.



 Probably the best place to start is with the grounding system.  I really

 don’t like the idea of routing current through the airframe and would prefer

 to ground everything back to a block.



 Here is where I think I’m headed.



 1)      Run a line directly from the (-) Terminal of the battery forward to

 the firewall.



 a.       Attach this line to a “Forest of Tab”  on the interior side of the

 firewall.  Ground everything forward of the baggage compartment to this

 spot.



 b.      Jump through the firewall on the other side and ground all FWF items

 to the “Forest of Tab” on the FWF side.



 c.       I’ll also ground the crank case at this point too.



 2)      Run a line directly from the (-) Terminal of the battery to the left

 wing tip and install a Forest out there too…..



 a.       Install a similar setup for NAV, Strobe, Taxi/Landing, Pitot heat,

 Aileron Trim, Stall Warning, etc……



 3)      Run a line directly from the (-) Terminal of the battery to the

 right wing tip and install a Forest.



 a.       Repeat the left side setup of grounding on the wing items on the

 right side.



 4)      Run a line directly from the (-) Terminal of the battery  to a

 “Forest of Tabs” located beside the battery box.



 a.       This is for the point for grounding all tailcone electronics.  NAV,

 Rudder Trim Servo, Elevator Servo, and any other electronic devices that end

 up aft of the baggage compartment.



 How have you designed your grounding system?  Grounding issues can be a pain

 to chase down, so that’s the reason I’m really wanting to spend the time

 designing a system that is pretty robust and easy to trace.



 Thanks,



 Phil




	


-- 

Rob Kermanj

Kellym

Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ

Posted: Mon Aug 31, 2009 1:50 pm Post subject: Grounding Questions

IIRC, Bob Nuckolls advocates only single point grounding for "sensitive" 

  electronics; that the heavy load stuff like starter, battery, landing 

light, pitot heat are all fine being grounded through the aluminum 

airframe. Running dedicated grounds for those devices just adds 

complexity and weight for no discernible benefit. I doubt you will find 

any TC aircraft with separate ground leads for the heavy loads. If you 

still decide to go with separate ground leads for lighting and pitot 

heat, they would benefit from twisting with the hot lead to reduce 

magnetic influences on your compass, remote or otherwise.



Rob Kermanj wrote:

 	  Quote: 	
		   

 

 Have a dedicated ground for all your radio/gps equipment and ground

 everything including the headset jacks back to this point.  Make sure

 that you use the washer with shoulder (comes with the jacks) to

 isolate the headset jacks from the airframe ground.

 

 On Sun, Aug 30, 2009 at 8:53 PM, Perry, Phil<Phil.Perry(at)netapp.com> wrote:

> I’m in the process of trying to layout my electrical system on paper and in

> my head.

>

> Probably the best place to start is with the grounding system.  I really

> don’t like the idea of routing current through the airframe and would prefer

> to ground everything back to a block.

>

> Here is where I think I’m headed.

>

> 1)      Run a line directly from the (-) Terminal of the battery forward to

> the firewall.

>

> a.       Attach this line to a “Forest of Tab”  on the interior side of the

> firewall.  Ground everything forward of the baggage compartment to this

> spot.

>

> b.      Jump through the firewall on the other side and ground all FWF items

> to the “Forest of Tab” on the FWF side.

>

> c.       I’ll also ground the crank case at this point too.

>

> 2)      Run a line directly from the (-) Terminal of the battery to the left

> wing tip and install a Forest out there too…..

>

> a.       Install a similar setup for NAV, Strobe, Taxi/Landing, Pitot heat,

> Aileron Trim, Stall Warning, etc……

>

> 3)      Run a line directly from the (-) Terminal of the battery to the

> right wing tip and install a Forest.

>

> a.       Repeat the left side setup of grounding on the wing items on the

> right side.

>

> 4)      Run a line directly from the (-) Terminal of the battery  to a

> “Forest of Tabs” located beside the battery box.

>

> a.       This is for the point for grounding all tailcone electronics.  NAV,

> Rudder Trim Servo, Elevator Servo, and any other electronic devices that end

> up aft of the baggage compartment.

>

> How have you designed your grounding system?  Grounding issues can be a pain

> to chase down, so that’s the reason I’m really wanting to spend the time

> designing a system that is pretty robust and easy to trace.

>

> Thanks,

>

> Phil

>

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD

drfred(at)suddenlinkmail.
Guest

Posted: Mon Aug 31, 2009 2:47 pm Post subject: Grounding Questions

Bout 3-4 years ago I heard one of the electronic gurus speak at Osh.  At 

that lecture he did recommend couple grounds from the engine to the 

airframe.  He has several stories of hard starting engines with 

inadequate grounds. I don't remember him saying that you had to run a 

separate ground back for all the other devices (again complexity/vs wt 

savings).   In trying to get adequate starter power for my engine, I 

have run a separate ground from the starter back to a common post on the 

firewall.  The post then has a number 4 wire back to the battery.  I 

switched out my skytec starter for a B&C starter and I think I have 

solved my starter problems.  I'd recommend that if you have a higher 

compression engine you consider starting out with a B&C starter. 



Dr Fred.



Kelly McMullen wrote:

 	  Quote: 	
		   



 IIRC, Bob Nuckolls advocates only single point grounding for 

 "sensitive"  electronics; that the heavy load stuff like starter, 

 battery, landing light, pitot heat are all fine being grounded through 

 the aluminum airframe. Running dedicated grounds for those devices 

 just adds complexity and weight for no discernible benefit. I doubt 

 you will find any TC aircraft with separate ground leads for the heavy 

 loads. If you still decide to go with separate ground leads for 

 lighting and pitot heat, they would benefit from twisting with the hot 

 lead to reduce magnetic influences on your compass, remote or otherwise.



 Rob Kermanj wrote:

> 

>

> Have a dedicated ground for all your radio/gps equipment and ground

> everything including the headset jacks back to this point.  Make sure

> that you use the washer with shoulder (comes with the jacks) to

> isolate the headset jacks from the airframe ground.

>

> On Sun, Aug 30, 2009 at 8:53 PM, Perry, Phil<Phil.Perry(at)netapp.com> 

> wrote:

>> I’m in the process of trying to layout my electrical system on paper 

>> and in

>> my head.

>>

>>

>>

>> Probably the best place to start is with the grounding system.  I 

>> really

>> don’t like the idea of routing current through the airframe and 

>> would prefer

>> to ground everything back to a block.

>>

>>

>>

>> Here is where I think I’m headed.

>>

>>

>>

>> 1)      Run a line directly from the (-) Terminal of the battery 

>> forward to

>> the firewall.

>>

>> a.       Attach this line to a “Forest of Tab”  on the interior side 

>> of the

>> firewall.  Ground everything forward of the baggage compartment to this

>> spot.

>>

>> b.      Jump through the firewall on the other side and ground all 

>> FWF items

>> to the “Forest of Tab” on the FWF side.

>>

>> c.       I’ll also ground the crank case at this point too.

>>

>> 2)      Run a line directly from the (-) Terminal of the battery to 

>> the left

>> wing tip and install a Forest out there too…..

>>

>> a.       Install a similar setup for NAV, Strobe, Taxi/Landing, 

>> Pitot heat,

>> Aileron Trim, Stall Warning, etc……

>>

>> 3)      Run a line directly from the (-) Terminal of the battery to the

>> right wing tip and install a Forest.

>>

>> a.       Repeat the left side setup of grounding on the wing items 

>> on the

>> right side.

>>

>> 4)      Run a line directly from the (-) Terminal of the battery  to a

>> “Forest of Tabs” located beside the battery box.

>>

>> a.       This is for the point for grounding all tailcone 

>> electronics.  NAV,

>> Rudder Trim Servo, Elevator Servo, and any other electronic devices 

>> that end

>> up aft of the baggage compartment.

>>

>>

>>

>> How have you designed your grounding system?  Grounding issues can 

>> be a pain

>> to chase down, so that’s the reason I’m really wanting to spend the 

>> time

>> designing a system that is pretty robust and easy to trace.

>>

>>

>>

>> Thanks,

>>

>> Phil

>>

>>

>>

>>

>>

>>

>>

>

Phil.Perry(at)netapp.com
Guest

Posted: Tue Sep 01, 2009 6:55 am Post subject: Grounding Questions

I'm not sure that's right Kelly..  Of course I have a hard time

following much of what Mr. Nuckolls has to say in his book.  He's so

damn verbose and wants to share so much history that it's really hard to

follow his thought process.    I wish he would write another book

called "Just the Facts" and leave the other 85% of the history, stories,

and unnecessary content out.  But at least there is some good

information in there in the diagrams and in general.  You just have to

get to it.



But that's just me....



So back to the topic...



On page 5-4 paragraph #2, he tells a story of when they used to own an

airport.  A mechanic was reinstalling an engine that was overhauled.  In

the process of connecting grounds, he didn't connect the ground strap

between the crankcase and the firewall.



When they tried to start the engine they only had smoke.  Come to find

out the current tried to find a path back to the battery via throttle,

mixture, and p-lead shielding.



So it sounds like he is advocating a ground from the crankcase to the

airframe.  But then in the next sentence, he says "Grounding the

crankcase to the battery directly eliminates this possibility."



He suggests grounding the crankcase with a heavy braid to the bolt

holding the Forest of Tabs on the firewall.  Then from the Tabs to the

battery.



So it's open to your interpretation I guess.



I think I'm going to run a heavy ground from the battery to the tabs at

the panel.  Then from the tabs, I'll run a ground wire to each wing tip

and one to the tail.  FWF, I'm going to jump through the firewall (from

the tabs) and run a strap to the starter.  Then a jumper from the

starter to the alternator.

Phil



--

rv10builder(at)bellsouth.
Guest

Posted: Tue Sep 01, 2009 10:12 am Post subject: Grounding Questions

Phil,



For FWF a single braided connection from the rear of the engine block to a

forest of tabs on the firewall is more than sufficient (pic attached).  You

would only be adding unnecessary weight with a ground connection all the way

up the starter and alternator.



Brian

N104BS (160 hours)

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rv10builder(at)bellsouth.
Guest

Posted: Tue Sep 01, 2009 10:23 am Post subject: Grounding Questions

Phil,



For FWF a single braided connection from the rear of the engine block to a

forest of tabs on the firewall is more than sufficient (pic attached).  You

would only be adding unnecessary weight with a ground connection all the way

up the starter and alternator.



Brian

N104BS (160 hours)

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rv10builder(at)bellsouth.
Guest

Posted: Tue Sep 01, 2009 10:23 am Post subject: Grounding Questions

Phil,



For FWF a single braided connection from the rear of the engine block to a

forest of tabs on the firewall is more than sufficient (pic attached).  You

would only be adding unnecessary weight with a ground connection all the way

up the starter and alternator.



Brian

N104BS (160 hours)

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pitts_pilot(at)bellsouth.
Guest

Posted: Tue Sep 01, 2009 12:24 pm Post subject: Grounding Questions

Here's my take:  A heavy ground from the battery to the firewall, and 

from the firewall to the engine case eliminates any grounding issues 

down the road.  I have seen corrosion caused by electrolysis in aluminum 

structures .... typically where the rivets or screws are ...  from 

currents in the ground.  I have also seen the braided ground straps 

deteriorate from vibration and electrolysis ..... but it did take a long 

time.  In the scheme of things, the additional ground weight is minimal, 

and the absence of grounding problems in the future outweighs the weight 

penalty.  The 'airframe ground' problems show up when your battery is 

old on a cold morning and you need to depart quickly.  It is true that 

most factory built aircraft use the airframe as ground ..... but the 

battery is usually hanging on the firewall, not stuck back behind the 

baggage compartment like RV-10s and Cherokees.  I'm running both power 

and ground from the battery to bulkhead feedthroughs from Waytek, and a 

short cable from there to the engine case (ground) and to the starter 

(power) through the start solenoid.  There will be a heavy cable (but 

smaller than the above power/ground) to the subpanel where everything is 

connected on terminal strips.  Both power and ground.  Nav lights will 

use airframe ground.  Electronics in the tail will have power and ground 

fed from the sub-panel terminal strips.

Linn



Brian wrote:

 	  Quote: 	
		   Phil,

 

 For FWF a single braided connection from the rear of the engine block to a

 forest of tabs on the firewall is more than sufficient (pic attached).  You

 would only be adding unnecessary weight with a ground connection all the way

 up the starter and alternator.

 

 Brian

 N104BS (160 hours)

Phil.Perry(at)netapp.com
Guest

Posted: Tue Sep 01, 2009 12:25 pm Post subject: Grounding Questions

Thanks Brian...



What did you run from the battery to cabin-side of the firewall?



Also, do you have all of your grounds coming back to the tabs?

	AKA: Wingtips and Tailcone too.



Thanks!



--

jeff(at)westcottpress.com
Guest

Posted: Tue Sep 01, 2009 1:20 pm Post subject: Grounding Questions

another thought...



There is a longeron that runs up the right side of the plane... from the aft side of the baggage compartment to the firewall.  My plan is to run a ground strap from the battery to the aft end of that...

Jeff Carpenter

40304

Routing out my left window  >:



On Aug 30, 2009, at 5:53 PM, Perry, Phil wrote:

 	  Quote: 	
		  I’m in the process of trying to layout my electrical system on paper and in my head.

 

Probably the best place to start is with the grounding system.  I really don’t like the idea of routing current through the airframe and would prefer to ground everything back to a block.

 

Here is where I think I’m headed.

 

1)      Run a line directly from the (-) Terminal of the battery forward to the firewall.

a.       Attach this line to a “Forest of Tab”  on the interior side of the firewall.  Ground everything forward of the baggage compartment to this spot.

b.      Jump through the firewall on the other side and ground all FWF items to the “Forest of Tab” on the FWF side.

c.       I’ll also ground the crank case at this point too.

2)      Run a line directly from the (-) Terminal of the battery to the left wing tip and install a Forest out there too…..

a.       Install a similar setup for NAV, Strobe, Taxi/Landing, Pitot heat, Aileron Trim, Stall Warning, etc……

3)      Run a line directly from the (-) Terminal of the battery to the right wing tip and install a Forest.

a.       Repeat the left side setup of grounding on the wing items on the right side.

4)      Run a line directly from the (-) Terminal of the battery  to a “Forest of Tabs” located beside the battery box.

a.       This is for the point for grounding all tailcone electronics.  NAV, Rudder Trim Servo, Elevator Servo, and any other electronic devices that end up aft of the baggage compartment.

 

How have you designed your grounding system?  Grounding issues can be a pain to chase down, so that’s the reason I’m really wanting to spend the time designing a system that is pretty robust and easy to trace.

 

Thanks,

Phil

 

 



 	  Quote: 	
		  



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 [quote][b]

Kellym

Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ

Posted: Tue Sep 01, 2009 1:20 pm Post subject: Grounding Questions

Every Mooney of more than 180hp has the battery(s)behind the baggage 

compartment, and uses local airframe grounds. Some Cessnas also have 

battery in back and use local grounds. As well as the mentioned Pipers. 

Never have seen any corrosion anywhere but the actual cable connections, 

which should be inspected annually. Pipers had problems with aluminum 

battery cables on positive side of circuit.

Linn Walters wrote:

 	  Quote: 	

 Here's my take:  A heavy ground from the battery to the firewall, and 

 from the firewall to the engine case eliminates any grounding issues 

 down the road.  I have seen corrosion caused by electrolysis in aluminum 

 structures .... typically where the rivets or screws are ...  from 

 currents in the ground.  I have also seen the braided ground straps 

 deteriorate from vibration and electrolysis ..... but it did take a long 

 time.  In the scheme of things, the additional ground weight is minimal, 

 and the absence of grounding problems in the future outweighs the weight 

 penalty.  The 'airframe ground' problems show up when your battery is 

 old on a cold morning and you need to depart quickly.  It is true that 

 most factory built aircraft use the airframe as ground ..... but the 

 battery is usually hanging on the firewall, not stuck back behind the 

 baggage compartment like RV-10s and Cherokees.  I'm running both power 

 and ground from the battery to bulkhead feedthroughs from Waytek, and a 

 short cable from there to the engine case (ground) and to the starter 

 (power) through the start solenoid.  There will be a heavy cable (but 

 smaller than the above power/ground) to the subpanel where everything is 

 connected on terminal strips.  Both power and ground.  Nav lights will 

 use airframe ground.  Electronics in the tail will have power and ground 

 fed from the sub-panel terminal strips.

 Linn

 Brian wrote:

> Phil,

>

> For FWF a single braided connection from the rear of the engine block 

> to a

> forest of tabs on the firewall is more than sufficient (pic 

> attached).  You

> would only be adding unnecessary weight with a ground connection all 

> the way

> up the starter and alternator.

>

> Brian

> N104BS (160 hours)

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD

Kellym

Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ

Posted: Tue Sep 01, 2009 1:21 pm Post subject: Grounding Questions

Phil,

There are two issues. Yes, the engine needs a very stout ground cable to 

the firewall, because the engine mounts make a poor grounding path. No, 

you don't need a ground cable from your firewall ground point to the 

battery. The airframe will serve very well. Just for example, my Mooney 

has a braided ground from the engine crankcase to the firewall...no 

forest of tabs, just a single bolt and washer connection at firewall. 

ALL grounds are to the airframe. Not as good as the single point of 

grounding for electronics. But more than sufficient for all your 

lighting and your starter. My battery is behind baggage compartment, 

just like RV-10. Ground is to an airframe rib with bolt and washer. 

Carries all 300 amps or so during starting, with very little resistance. 

Virtually all certificated metal skinned aircraft do the same, because 

it works, is lightweight and maintenance free. Including the Piper 

Cherokee he mentions reducing battery size. Other than that mention, 

none of his verbiage really addresses the rear mount battery in a metal 

airframe. He mostly talks about batteries on the firewall and composite 

aircraft. Yes, you would run a cable from battery to firewall if it is 

only 18". The subject has come up on his email list.

But you are free to install the extra heavy #4 cable all the way back to 

your battery if you want. Just money, weight and space.

A quote from Bob on his email list a couple years ago:

">1) For each battery (minus) it's shown to connect locally to the

 >airframe.  Providing that good, secure connections with 4AWG (or welding

 >cable) are done locally, does this negate the need to run heavy (2AWG or

 >4AWG) ground cabling forward?

     Yes.

 >2) Relates to question 1.  If it's necessary to run ground cabling

 >forward, is it acceptable/reasonable to instead: a) Connect the battery

 >minus posts with a single, short welding cable, and b) Connect another

 >single short welding cable for local ground, and c) continue with a 

single

 >large (2AWG or 4AWG) cable forward to connect to the Brass Firewall Thru

 >Bolt for the Firewall, Panel and downstream Avionics ground busses? 

(This

 >seems overdone, redundant and heavy to me, but I just want to be sure I

 >haven't missed something here)

     There's a boatload of ol' mechanic's tales out there about

     the hazards of local grounds in aircraft. Aside from the obvious

     and predictable issues involving ground loops (when particularly

     vulnerable systems share grounds spread out over the airframe),

     there are no great concerns for using the airframe as a primary

     ground structure. There's some value in considering the used of

     a separate ground wire for tubular structures where we've see

     some instances of structure getting magnetized due to high current

     flow . . . but that doesn't apply to you."

Perry, Phil wrote:

[quote] 

 I'm not sure that's right Kelly..  Of course I have a hard time

 following much of what Mr. Nuckolls has to say in his book.  He's so

 damn verbose and wants to share so much history that it's really hard to

 follow his thought process.    I wish he would write another book

 called "Just the Facts" and leave the other 85% of the history, stories,

 and unnecessary content out.  But at least there is some good

 information in there in the diagrams and in general.  You just have to

 get to it.

 But that's just me....

 So back to the topic...

 On page 5-4 paragraph #2, he tells a story of when they used to own an

 airport.  A mechanic was reinstalling an engine that was overhauled.  In

 the process of connecting grounds, he didn't connect the ground strap

 between the crankcase and the firewall.

 When they tried to start the engine they only had smoke.  Come to find

 out the current tried to find a path back to the battery via throttle,

 mixture, and p-lead shielding.

 So it sounds like he is advocating a ground from the crankcase to the

 airframe.  But then in the next sentence, he says "Grounding the

 crankcase to the battery directly eliminates this possibility."

 He suggests grounding the crankcase with a heavy braid to the bolt

 holding the Forest of Tabs on the firewall.  Then from the Tabs to the

 battery.

 So it's open to your interpretation I guess.

 I think I'm going to run a heavy ground from the battery to the tabs at

 the panel.  Then from the tabs, I'll run a ground wire to each wing tip

 and one to the tail.  FWF, I'm going to jump through the firewall (from

 the tabs) and run a strap to the starter.  Then a jumper from the

 starter to the alternator.

 Phil

 --

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD

msausen

Joined: 25 Oct 2007
Posts: 559
Location: Appleton, WI USA

Posted: Tue Sep 01, 2009 3:39 pm Post subject: Grounding Questions

I chose to run a #2 cable up to the firewall, same as the positive.  I'm running it though the firewall with a piece of 3/8ths all thread rod so it is acting as the single point ground for my panel, airframe, and engine.  I'll still ground non sensitive equipment like Nav lights at the source and I also have a battery bus back by the batteries and anything there can ground right to the battery.



Michael



--

ricksked(at)embarqmail.co
Guest

Posted: Tue Sep 01, 2009 4:45 pm Post subject: Grounding Questions

Guys/Gals,



I local grounded the battery's at the aft bulkhead...Ran independent grounds for EVERYTHING to the tree at the firewall (no G loops by running independent grounds)  where the engine is grounded to the tree by the same size ( #2 welding lead) cable use to deliver power to the starter. It works fine, don't mind f#*k this.......it has worked this way on aircraft for years....and years....I only local grounded the position lights...From my "flying" experience there is no reason to run a #2 ground wire up front....



YMMV....and just the normal 2 cents......



Rick Sked

N246RS

Sent via BlackBerry by AT&T



--

Dick Sipp

Joined: 11 Jan 2006
Posts: 215
Location: Hope, MI

Posted: Tue Sep 01, 2009 6:51 pm Post subject: Grounding Questions

I did just that Jeff.  Seems to be working  great.

  

 Dick Sipp

 N110DV

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