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Jae Chang
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  • 30 days


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    Tue, 12 Feb 2008


    Match: #11 Message: #9098 Date: Mar 10, 1996 From: "Robert L. Nuckolls, III" <72770.552(at)compuserve.com> Subject: Re: Ground Bus and Other Grounding Issues

    >An excellent source for a ground bus is B&C Specialty Products (316)283-8000. >They have one that uses PIDG spade terminal connections. >Stan Blanton >RV-6 Fuselage skeleton While the topic of grounding is up . . . I thought I would share some words with RV-LIST which are currently being incorporated into the 6th edition of the 'Connection. Some salient points to ponder . . .
    1. The most important wire in your airplane runs from battery (-) to crankcase. In all but rotax powered airplanes this should be a 2AWG (oh well, you RVers with 12" ground leads can get by with a 4AWG . . . BUT NO SMALLER. There are a number of reasons for this which I won't elaborate on here . . . you'll have to get details by reading the book!
    2. The next wire to go in runs from crankcase to firewall. This wire is alternator and/or systems load sized, 4AWG for 60 amp alternators, 6 AWG for 40 amp machines.
    3. If your airplane is tractor type, the next items to install are B&C ground buses on both sides of firewall. A 48-pin device on cabin side, a 24-pin device on firewall side. Both them back to back with 5/16" BRASS hardware. The firewall to crankcase lead should go to the 5/16" thru-stud. Install the stud with just ground busses and locktite under the first nut. Put the firewall to crankcase jumper under a second nut with an internal tooth lockwasher.
    4. Now, if you're building an RV, your ground SYSTEM is done. Only remotely located components like light fixtures at tips, strobe supplies under seat, etc . . . are grounded locally (right next to where they mount). All goodies behind panel should get their own ground wire to the ground bus . . . don't daisy-chain a number of components onto the same ground wire. All goodies under the cowl, except for those which achieve ground by virtue of it's enclosure being mounted to metal, get their own ground lead to the forward firewall ground bus.
    5. Special Cases: All headset and microphone jacks should be INSULATED from local ground with fiber washers or fabrication of non-conducting mounting brackets. All unbalanced antennas (comm monopole, Archer's wing-tip vor antennas, etc) must get good local ground. All balanced antennas (g.s. dipoles, vor dipoles in canards, Archer's gamma-matched dipoles, etc) generally require no local ground and may cause problems if they ARE locally grounded. Check with manufacturer but in any case, leaving it ungrounded is generally the best thing to do FIRST. Canard pusher aircraft with battery mid-ships or forward will have an engine side firewall ground bus as above but no cabin side ground bus. These aircraft need a 48-point ground block behind the panel attached to battery (-) with 4AWG wire.
    In a nutshell, the techniques described will save you a lot of fuss and all but guarantee a noise free, voltage stable electrical system.
    Bob
    . . . AeroElectric Connection

    posted at: 16:22 | path: /aviation/build/avionics/aeroelectric | permanent link to this entry | add a comment