Electrical bonding problems in aircraft

[lucaperazzolli]

Hi !

Has somebody have 'brainstorming time' about this problem ?

Let me know, I have to give an answer to my ENAC (Italian FAA) Controller.

Thank in advance

Luca

[smithhb]

Are you referring to electrical conductivity in an aluminum aircraft or friction welding aluminum bonding of skins?

[lucaperazzolli]

Hi, thanks for contact, I refer to electrical conductivity in an aluminum aircraft

[gmcjetpilot]

Originally Posted by lucaperazzolli

Hi, thanks for contact, I refer to electrical conductivity in an aluminum aircraft

There is no problem, aluminum is very conductive.

Bonding = grounding or grounding straps.

However there is a recommended method for attaching bond straps or ground straps to aluminum structure.

In the USA the FAA has "Advisory Circulars" to give guidance and good or "BEST PRACTICE".

Electrical bonding is: AC 43 13-1B, Chapter 11, Electrical.

Attaching to aluminum structure may cause dissimilar metal corrosion. Typically "passivated" washers, screws, bolts and nuts are used to secure a ground strap to the airframe. This is BEST practice and reduces chance of corrosion.

Some builders run a separate ground wires to each component, for example lights in the wing tips or tail. Some builders ground to the airframe locally. Both methods work fine. The FAA accepts both. Again the bolt, nut and washer touching the aluminum structures should be "passivated" hardware. Passivated is neutral and resist corrosion on the aluminum or hardware.


arrivederci

[smithhb]

One primary resource most builders reference is the book, "Aeroelectric Connection" by Bob Nuckolls. It is the premier bible for electrical systems in OBAM (owner built and maintained aircraft).



https://matronics.com/aeroelectric/Catalog/pub/pub.html

[az_gila]

Originally Posted by gmcjetpilot

There is no problem, aluminum is very conductive.

Bonding = grounding or grounding straps.

However there is a recommended method for attaching bond straps or ground straps to aluminum structure.

In the USA the FAA has "Advisory Circulars" to give guidance and good or "BEST PRACTICE".

Electrical bonding is: AC 43 13-1B, Chapter 11, Electrical.

Attaching to aluminum structure may cause dissimilar metal corrosion. Typically "passivated" washers, screws, bolts and nuts are used to secure a ground strap to the airframe. This is BEST practice and reduces chance of corrosion.

Some builders run a separate ground wires to each component, for example lights in the wing tips or tail. Some builders ground to the airframe locally. Both methods work fine. The FAA accepts both. Again the bolt, nut and washer touching the aluminum structures should be "passivated" hardware. Passivated is neutral and resist corrosion on the aluminum or hardware.


arrivederci

George... perhaps he is referring to this section of Part 23 for certified aircraft?

Sec. 23.867

[Electrical bonding and protection against lightning and static electricity.]

(a) The airplane must be protected against catastrophic effects from lightning.
(b) For metallic components, compliance with paragraph (a) of this section may be shown by--
(1) Bonding the components properly to the airframe; or
(2) Designing the components so that a strike will not endanger the airplane.
(c) For non-metallic components, compliance with paragraph (a) of this section may be shown by--
(1) Designing the components to minimize the effect of a strike; or
(2) Incorporating acceptable means of diverting the resulting electrical current so as not to endanger the airplane.

Certified planes usually achieve this with bonding straps that connect major components together. An example of these can be seen as short lengths of braid or wire connecting the aileron to the wing on certified planes.

Our RVs do not have any of these specific bonding straps/wires added, instead relying on electrical conductivity through control bearings, etc., which probably do not meet the FAA requirements for certified aircraft.

gil A