Grounding and Doug's front page pic...

[az_gila]

Doug... I noticed the new audio clip and picture dealing with grounds, and I feel it should be commented on.

The gist of the audio was to use graphite paste, which is fine, however the associated picture showed some techniques that are definitely not in accordance with AC 43.13.

Grounding hardware is quite well detailed in Chapter 11 of the "bible".

long link here to FAA web site

Page 82 (Table 11-16) covers how to use bolts as ground connections - our terminals are usually tinned copper, so use the lower half of the table.

In the picture shown...

No removal of primer under the nut - bare metal should be exposed.

A self locking nut is not appropriate as shown against the metal surface.

No washers apparent, either plain or self-locking.

Plain washers and self-locking washers are the correct hardware to use, and the materials should be as listed in the AC. In general, for our alum. planes, standard cadmium plated AN hardware is correct, with an aluminum washer under the terminal.

A final lock nut on the "stack" of parts is correct, and not shown.

It is so easy to follow the recommendations of AC 43.13-1b in this case, that there is no reason for using any other procedure.

If your Technical Counselor disagrees with the 43-13 recommendations, then let's have an open discussion about his reasons, and have him present them.

Until this happens, I believe the FAA recommendations are the correct procedures, and we should not propagate alternate methods without good reason.

YMMV, but I think that TCs should start with the FAA guidance as a basis for our RV construction work.

gil A

[jsharkey]

Gil is correct - but the Van's plans do show a nyloc nut securing the ground stud to the panel, similarly with the "studs" on the on the home made terminal block. It can be confusing.
Jim Sharkey
RV6 - Wiring

[DeltaRomeo]

Maybe Mel Asberry will chime in...he was standing next to me when I took the pic.
b,
d

[Mel]

Gil,
Your points are correct. However you must realize that this aircraft is a ways from being completed. These points were discussed at the meeting. Don was simply discussing one point. He was not trying to do a complete diagnosis. Another point that was not brought out was that you should limit the number of ground lugs to three per stud.

[jsharkey]

Originally Posted by Mel

Gil,
Your points are correct. However you must realize that this aircraft is a ways from being completed. These points were discussed at the meeting. Don was simply discussing one point. He was not trying to do a complete diagnosis. Another point that was not brought out was that you should limit the number of ground lugs to three per stud.

FYI - Chapter 11 says four lugs max.

[Mel]

Originally Posted by jsharkey

FYI - Chapter 11 says four lugs max.

I was going by Mil Spec. 4 is certainly acceptable. My recommendation is 3.

[DeltaRomeo]

Originally Posted by Mel

I was going by Mil Spec. 4 ...snip

Not to hijack the thread, but anything Mel says is considered 'Mel Spec'.

rim shot....

[Canadian_JOY]

The MIL Spec for grounding was developed partly with an eye to 43-13, and partly with an eye toward aircraft life cycle managment. The limitation of 3 lugs per terminal was established as a means of allowing easy supplemental/after-the-fact equipment installation. All of the rework instructions I've had to get through USAF/US Army approval have allowed the addition of one ground lug to each pre-existing ground terminal, thus not exceeding 43-13's 4-per-terminal recommendation. By limiting net-new installations to 3-per-terminal the Mil Spec makes it easy for future systems growth without having to install a new grounding terminal.

If you're building a new airplane it's not a bad idea to go with 4-per-terminal, but install an extra terminal or two at the main grounding points (firewall, instrument panel). This will make it easy for you to install and properly ground any equipment you might add in the future.

[RV8TOR]

Thanks for the comments guys, it was just that I have found it is cheaper to buy all of my hardware from Home Depot and not Van's. Besides those pesky ny-locs are so hard to work with and I can hand-tighten the other ones.

[Bob Brown]

If you have very many grounds at all...I'd sure recommend going with the single point ground that Aeroelectric Connection recommends and that B&C sells, with a panel of tabs on each side of the firewall. It sure makes it easy to map out your ground bus.