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grounding to fuselage

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sarg314(at)gmail.com
Guest

Posted: Tue Jun 02, 2009 6:16 am Post subject: grounding to fuselage

In general I am opposed to running current thru the fuselage, but in the case of the white tail light, I am willing to make an exception.  Is there any "approved" way of doing this so as to avoid causing corrosion due to the contact of dissimilar metals?  Is a tin plated (it is tin isn't it?) ring terminal against bare aluminum going to cause a problem?  Should it be covered/sprayed with something to protect it from moisture?  Or is this just a bad idea under any circumstances? 

Thanks,

-- 

Tom Sargent, RV-6A final assembly.

 

  [quote][b]

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nuckolls.bob(at)aeroelect
Guest

Posted: Tue Jun 02, 2009 7:31 am Post subject: grounding to fuselage

At 08:48 AM 6/2/2009, you wrote:

 	  Quote: 	
		  In general I am opposed to running current thru the fuselage, but in 

the case of the white tail light, I am willing to make an 

exception.  Is there any "approved" way of doing this so as to avoid 

causing corrosion due to the contact of dissimilar metals?


	


 	  Quote: 	
		    Is a tin plated (it is tin isn't it?) ring terminal against bare 

 aluminum going to cause a problem?  Should it be covered/sprayed 

 with something to protect it from moisture?  Or is this just a bad 

 idea under any circumstances?


	


   Local concerns for the attachment of wires to

   the airframe have been the topic of many pages

   of "how to" and "how not" to do. In the

   most hostile of environments, all the recommended

   processes and materials add longevity to

   the connection.



   Our airplanes are seldom operated in conditions

   that qualify as strenuous much less hostile.

   Design goals for local grounding/bonding

   speak to deleterious effects for failure to

   faithfully observe recipes for success but they

   seldom speak to the physics of the effects or

   relative risks.



   Keep in mind that for corrosion to occur, oxygen

   laden moisture must be present in the joint.

   Only then do the electrolytic effects of

   dissimilar metals in ionized solutions

   arise.



   Yes, the tin plating of copper terminals #1

   task is an electrolytic "buffer" between copper

   and aluminum . . . but if you damage the tin

   layer in any way during assembly or maintenance

   of the joint, that barrier is breached and

   the original copper-aluminum couple is exposed.



   For all the fuss and froth about materials

   control, the very best prophylactic against

   corrosion call for making joints up with sufficient

   pressure to produce "gas-tightness" enhanced

   with a means by which future moisture ingress

   is retarded assuages 99.99% of your concerns.



   Join clean metals with robust, locking fasteners.

   Coat the metals with silicon grease before joining.

   And the joint will be fine for more than the

   lifetime of airplane. You can "drink from the

   fire hose" off grounding/bonding processes

   in section 15 of AC43-13 offers a rigorous study.



   There's nothing inherently evil about using the

   airframe to carry power system currents. Modern

   production aircraft made of aluminum have

   countless airframe grounds crafted with due

   diligence to the principals of gas-tightness

   and choice of materials. These function as

   desired for the lifetime of the airplane.

        Bob . . .



        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

        ----------------------------------------

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rv-9a-online(at)telus.net
Guest

Posted: Tue Jun 02, 2009 7:52 am Post subject: grounding to fuselage

AC43.13-1B has an extensive discussion of aircraft  bonding (grounding), including the proper procedure for connecting to the  airframe and protection against corrosion.

  

 This document is available in .pdf format if you  don't have a hardcopy. It's a bit large to email, so if you can find it online  for download, that's good.

  

 If not, please let me know and I'll make other  arrangements.

  

 Thanks,

 Vern Little

 www.vx-aviation.com

 [quote]   ---

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nuckolls.bob(at)aeroelect
Guest

Posted: Tue Jun 02, 2009 8:01 am Post subject: grounding to fuselage

At 10:50 AM 6/2/2009, you wrote:

  	  Quote: 	
		   AC43.13-1B has an extensive discussion of aircraft bonding (grounding), including the proper procedure for connecting to the airframe and protection against corrosion.

  

 This document is available in .pdf format if you don't have a hardcopy. It's a bit large to email, so if you can find it online for download, that's good.

  

 If not, please let me know and I'll make other arrangements. 	


   AC43-13 is available for download at:



  http://www.aeroelectric.com/Reference_Docs/FAA/



 

        Bob . . .



        -----------------------------------------

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

        -----------------------------------------    [quote][b]

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Eric M. Jones

Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts

Posted: Wed Jun 03, 2009 4:54 am Post subject: Re: grounding to fuselage

I suppose you could "get away with it" to use the airframe for grounding. But remember that the "ground" connection does EXACTLY the same thing as the positive conductor but backwards.



Wiring a tail light might be fine, but wiring the ground on a MAC/RAC trim box will almost certainly cause a noisy bar graph indicator, and the desire to keep down the loop resistance can be frustrated, and change with age. If you just can't stop yourself, then at least don't use the airframe or tubes as a high current ground for engine starting.



A customer of mine has an automobile built of steel. It has a battery in the trunk and requires an additional ground conductor--or the engine won't start. Hmmmm.......



"When facing a decision, ask yourself: what would I do if I wasn't afraid?"

         â€”Russ Reeves

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_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Jun 03, 2009 5:33 am Post subject: grounding to fuselage

At 07:54 AM 6/3/2009, you wrote:

 	  Quote: 	
		  



I suppose you could "get away with it" to use the airframe for 

grounding. But remember that the "ground" connection does EXACTLY 

the same thing as the positive conductor but backwards.



Wiring a tail light might be fine, but wiring the ground on a 

MAC/RAC trim box will almost certainly cause a noisy bar graph 

indicator, and the desire to keep down the loop resistance can be 

frustrated, and change with age. If you just can't stop yourself, 

then at least don't use the airframe or tubes as a high current 

ground for engine starting.



A customer of mine has an automobile built of steel. It has a 

battery in the trunk and requires an additional ground conductor--or 

the engine won't start. Hmmmm.......


	


    All of which goes to the system integration task

    of deducing which devices are potential antagonists

    (can be grounded about anywhere) and potential victims

    (demand attention to wiring to avoid ground loop injection

    of noise).



    It's not a matter of "getting away with it". This

    phraseology suggests an air of uncertainty or risk

    for using the airframe as a ground. When accomplished

    with a bit of study and understanding, then there is no

    uncertainty, no risk and no wishful thinking for

    "getting away with" anything.



 	  Quote: 	
		  "When facing a decision, ask yourself: what would I do if I wasn't afraid?"


	


    Perhaps the better question is: "What do I need to understand to

    mitigate my unfounded fear?"

        Bob . . .



         ---------------------------------------

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

         ---------------------------------------

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mikef(at)apexconsultingse
Guest

Posted: Wed Jun 03, 2009 6:14 am Post subject: grounding to fuselage

Maybe it should be "ungrounded fear".....



On Wed, Jun 3, 2009 at 7:30 AM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> 

 

 At 07:54 AM 6/3/2009, you wrote:

  	  Quote: 	
		   --> AeroElectric-List message posted by: "Eric M. Jones" <emjones(at)charter.net (emjones(at)charter.net)>

 

 I suppose you could "get away with it" to use the airframe for grounding. But remember that the "ground" connection does EXACTLY the same thing as the positive conductor but backwards.

 

 Wiring a tail light might be fine, but wiring the ground on a MAC/RAC trim box will almost certainly cause a noisy bar graph indicator, and the desire to keep down the loop resistance can be frustrated, and change with age. If you just can't stop yourself, then at least don't use the airframe or tubes as a high current ground for engine starting.

  

 A customer of mine has an automobile built of steel. It has a battery in the trunk and requires an additional ground conductor--or the engine won't start. Hmmmm.......

 	
 



    All of which goes to the system integration task

    of deducing which devices are potential antagonists

    (can be grounded about anywhere) and potential victims

    (demand attention to wiring to avoid ground loop injection

    of noise).

 

    It's not a matter of "getting away with it". This

    phraseology suggests an air of uncertainty or risk

    for using the airframe as a ground. When accomplished

    with a bit of study and understanding, then there is no

    uncertainty, no risk and no wishful thinking for

    "getting away with" anything.

 

  	  Quote: 	
		   "When facing a decision, ask yourself: what would I do if I wasn't afraid?"

 	
 



    Perhaps the better question is: "What do I need to understand to

    mitigate my unfounded fear?"

 

 

        Bob . . .

 

         ---------------------------------------

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

         ---------------------------------------



 

 

 

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-- 

Mike



================================

Mike Fontenot

Apex Consulting & Services LLC

Lakewood, Colorado

303 / 731-6645

mikef AT apexconsultingservices DOT com

 =======

  [quote][b]

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