---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Mon 04/15/19: 7 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 07:40 AM - The joys of a Z-14 during an charging system failure (Bill Watson) 2. 10:09 AM - Re: Grounding to tube frame structures (jrevens) 3. 10:34 AM - Re: Re: Grounding to tube frame structures (Art Zemon) 4. 11:03 AM - Re: Re: Grounding to tube frame structures (Charlie England) 5. 11:50 AM - Re: Grounding to tube frame structures (jrevens) 6. 12:38 PM - Re: Re: Grounding to tube frame structures (Charlie England) 7. 03:18 PM - Re: Re: Grounding to tube frame structures (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 07:40:16 AM PST US From: Bill Watson Subject: AeroElectric-List: The joys of a Z-14 during an charging system failure Having just passed 1100 hours on my RV-10, I experienced my 2nd LR3C voltage regulator failure. Like the first, this turned out to be a non-event despite some difficulty in problem determination. I installed a Z-14 dual bus, dual alternator, dual battery electrical system. Specifically a B&C L-40, a B&C SD-20, (2) Odyssey PC680s, and (2) LR3c B&C regulators. Dual mags but an electrically hungry panel with (3) GRT EFISs and the rest of the usual kitchen sink. The charging system failure occurred during cruise in the normal configuration; i.e. with both buses running independently and not linked. I first noticed the voltage slowly drop on bus1. I switched the cross-link on and off a few times and observed the voltage climb each time suggesting something on bus1 had failed but bus2 was running fine. Soon the low voltage light lit so I simply switched the cross link on and completed the 2 hour leg. Upon landing and suspecting an LR3c failure, I ran through the problem determination procedure per B&C. Problem was it all checked out so I call them and they said it was probably a failed alternator. I sent it in, they checked it out, the 1100 hour L-40 was just fine so they sent it back for the cost of postage. I reinstalled it, reset the belt tension and took a test flight. All was well on the test flight so a week later I went on a 3 leg journey to DC, Pgh and return. No problems on the first 2 legs but on the third leg, bus 1 was out again. It was a non-event relative to finishing the 1.5 hour leg. I re-ran the regulator's PD procedure and step 4 failed (no voltage drop for those following along). Since I had a previously repaired one on the shelf, I simply swapped it out and was off and flying again. Findings: - The LR3c can 'soft-fail' and can be suspect even if PD checks out. - The 20amp backup alternator is capable of running my full daytime cruising load including battery charging. It only comes up short at low RPMs during ground ops. - The 40amp main alternator is enough for my fully loaded RV10 and will keep things running and charging even during low RPM ground ops (I already knew this). - The Z-14 provides a great deal of 'dispatch reliability'. I can finish out a trip and get home safely in most instances even with a failed regulator or alternator. I feel confident enough to take off with one side failed if need be, an example being on trips to the Bahamas as long as battery life will carry me to an airport even with a 2nd charging system failure. - Don't mount the LR3c on the back of the firewall up under the RV10 panel where it is so *^*&^I%%$$#GD hard to get at for adjustment or replacement. Bill "experiencing the joys of ongoing OBAM aircraft maintenance" Watson --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus ________________________________ Message 2 _____________________________________ Time: 10:09:57 AM PST US Subject: AeroElectric-List: Re: Grounding to tube frame structures From: "jrevens" This is not exactly on topic, but I would like to get Bob's take on it. In a recent online forum, the writer posted the following in regards to the "forest of tabs" grounding structure - > Avionics Ground BusAll other aircraft systems should be grounded through the avionics ground bus. This can be a "field of tabs" bus or simply a copper strip to accept ground wires from each of the systems. The avionics ground bus should not be grounded directly to the airframe. It should be locally isolated from the airframe with appropriate mounting. An 8 ga. wire should connect the avionics bus to the firewall pass-through bolt to complete the ground path. It seems a little silly to insulate the forest of tabs from the airframe and then connect it to the airframe with a wire to the pass through bolt. I'm also wondering about bringing all other aircraft system grounds to the "Avionics" buss. This was supposedly from an article in Kitplanes magazine. -------- John Evens Thorp T-18 N71JE (sold) Kitfox SS7 N27JE (built & flying) Read this topic online here: http://forums.matronics.com/viewtopic.php?p=488746#488746 Attachments: http://forums.matronics.com//files/final_ground_system_113.jpg ________________________________ Message 3 _____________________________________ Time: 10:34:07 AM PST US From: Art Zemon Subject: Re: AeroElectric-List: Re: Grounding to tube frame structures I have two forests of tabs, one on each side of the firewall. There is a hefty bolt, 5/16 if I remember correctly but maybe 1/4, that physically supports the two electrically connects them to the firewall. It's a metal airplane. One additional note: I had enough tabs in the forest inside the cabin that I did not bother with a seperate avionics ground bus. If I run out of tabs, I will add an avionics ground bus connected to one of the tabs. -- Art Z. On Mon, Apr 15, 2019 at 12:24 PM jrevens wrote: > > This is not exactly on topic, but I would like to get Bob's take on it. > In a recent online forum, the writer posted the following in regards to t he > "forest of tabs" grounding structure - > > > > Avionics Ground Bus=94All other aircraft systems should be ground ed > through the avionics ground bus. This can be a "field of tabs" bus or > simply a copper strip to accept ground wires from each of the systems. Th e > avionics ground bus should not be grounded directly to the airframe. It > should be locally isolated from the airframe with appropriate mounting. A n > 8 ga. wire should connect the avionics bus to the firewall pass-through > bolt to complete the ground path. > -- https://CheerfulCurmudgeon.com/ *"Love wins. Love always wins." Morrie Schwartz* ________________________________ Message 4 _____________________________________ Time: 11:03:01 AM PST US Subject: Re: AeroElectric-List: Re: Grounding to tube frame structures From: Charlie England On 4/15/2019 12:09 PM, jrevens wrote: > > This is not exactly on topic, but I would like to get Bob's take on it. In a recent online forum, the writer posted the following in regards to the "forest of tabs" grounding structure - > > >> Avionics Ground BusAll other aircraft systems should be grounded through the avionics ground bus. This can be a "field of tabs" bus or simply a copper strip to accept ground wires from each of the systems. The avionics ground bus should not be grounded directly to the airframe. It should be locally isolated from the airframe with appropriate mounting. An 8 ga. wire should connect the avionics bus to the firewall pass-through bolt to complete the ground path. > > It seems a little silly to insulate the forest of tabs from the airframe and then connect it to the airframe with a wire to the pass through bolt. I'm also wondering about bringing all other aircraft system grounds to the "Avionics" buss. This was supposedly from an article in Kitplanes magazine. > > -------- > John Evens > Thorp T-18 N71JE (sold) > Kitfox SS7 N27JE (built & flying) > > I think the logic is that if the avionics ground bus is remote from the main ground bus at the firewall, keeping it isolated and running its own ground wire to the firewall serves the same purpose as the firewall mounted bus: to prevent ground 'loops' (noise in the ground path showing up in undesired locations). Charlie --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus ________________________________ Message 5 _____________________________________ Time: 11:50:21 AM PST US Subject: AeroElectric-List: Re: Grounding to tube frame structures From: "jrevens" ceengland7(at)gmail.com wrote: > On 4/15/2019 12:09 PM, jrevens wrote: > > > > > > > This is not exactly on topic, but I would like to get Bob's take on it. In a recent online forum, the writer posted the following in regards to the "forest of tabs" grounding structure - > > > > > > > Avionics Ground BusAll other aircraft systems should be grounded through the avionics ground bus. This can be a "field of tabs" bus or simply a copper strip to accept ground wires from each of the systems. The avionics ground bus should not be grounded directly to the airframe. It should be locally isolated from the airframe with appropriate mounting. An 8 ga. wire should connect the avionics bus to the firewall pass-through bolt to complete the ground path. > > > > It seems a little silly to insulate the forest of tabs from the airframe and then connect it to the airframe with a wire to the pass through bolt. I'm also wondering about bringing all other aircraft system grounds to the "Avionics" buss. This was supposedly from an article in Kitplanes magazine. > > > > -------- > > John Evens > > Thorp T-18 N71JE (sold) > > Kitfox SS7 N27JE (built & flying) > > > > > > I think the logic is that if the avionics ground bus is remote from the > > > > main ground bus at the firewall, keeping it isolated and running its own > ground wire to the firewall serves the same purpose as the firewall > mounted bus: to prevent ground 'loops' (noise in the ground path showing > up in undesired locations). > > Charlie > > --- > This email has been checked for viruses by Avast antivirus software. > https://www.avast.com/antivirus Agreed, Charlie. I just couldn't see why you would want to insulate the forest of tabs from the firewall, as shown in the drawing. The direct connection to the carry through bolt and the firewall seems simpler and smarter. The author seems to imply that the forest of tabs must be insulated from the airframe, when the wire connecting it to the bolt connects it to the airframe anyway. I guess I just don't see the reasoning for "isolating" the bus when it is also connected with a conductor to the airframe. -------- John Evens Thorp T-18 N71JE (sold) Kitfox SS7 N27JE (built & flying) Read this topic online here: http://forums.matronics.com/viewtopic.php?p=488751#488751 ________________________________ Message 6 _____________________________________ Time: 12:38:09 PM PST US From: Charlie England Subject: Re: AeroElectric-List: Re: Grounding to tube frame structures On Mon, Apr 15, 2019 at 1:55 PM jrevens wrote: > > > ceengland7(at)gmail.com wrote: > > On 4/15/2019 12:09 PM, jrevens wrote: > > > > > > > > > > > This is not exactly on topic, but I would like to get Bob's take on > it. In a recent online forum, the writer posted the following in regards > to the "forest of tabs" grounding structure - > > > > > > > > > > Avionics Ground Bus=94All other aircraft systems should be gr ounded > through the avionics ground bus. This can be a "field of tabs" bus or > simply a copper strip to accept ground wires from each of the systems. Th e > avionics ground bus should not be grounded directly to the airframe. It > should be locally isolated from the airframe with appropriate mounting. A n > 8 ga. wire should connect the avionics bus to the firewall pass-through > bolt to complete the ground path. > > > > > > It seems a little silly to insulate the forest of tabs from the > airframe and then connect it to the airframe with a wire to the pass > through bolt. I'm also wondering about bringing all other aircraft syste m > grounds to the "Avionics" buss. This was supposedly from an article in > Kitplanes magazine. > > > > > > -------- > > > John Evens > > > Thorp T-18 N71JE (sold) > > > Kitfox SS7 N27JE (built & flying) > > > > > > > > > I think the logic is that if the avionics ground bus is remote from > the > > > > > > > main ground bus at the firewall, keeping it isolated and running its ow n > > ground wire to the firewall serves the same purpose as the firewall > > mounted bus: to prevent ground 'loops' (noise in the ground path showin g > > up in undesired locations). > > > > Charlie > > > > --- > > This email has been checked for viruses by Avast antivirus software. > > https://www.avast.com/antivirus > > > Agreed, Charlie. I just couldn't see why you would want to insulate the > forest of tabs from the firewall, as shown in the drawing. The direct > connection to the carry through bolt and the firewall seems simpler and > smarter. The author seems to imply that the forest of tabs must be > insulated from the airframe, when the wire connecting it to the bolt > connects it to the airframe anyway. I guess I just don't see the reasonin g > for "isolating" the bus when it is also connected with a conductor to the > airframe. > > -------- > John Evens > Thorp T-18 N71JE (sold) > Kitfox SS7 N27JE (built & flying) > > Ah; didn't even see his pic when I posted. You're right; absolutely no reason to isolate the firewall mounted FOT. Virus-free. www.avast.com <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2> ________________________________ Message 7 _____________________________________ Time: 03:18:39 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Grounding to tube frame structures > > > > > Avionics Ground Bus=94All other aircraft > systems should be grounded through the avionics > ground bus. This can be a "field of tabs" bus > or simply a copper strip to accept ground wires > from each of the systems. The avionics ground > bus should not be grounded directly to the > airframe. It should be locally isolated from > the airframe with appropriate mounting. An 8 > ga. wire should connect the avionics bus to the > firewall pass-through bolt to complete the ground path. > I think the logic is that if the avionics ground bus is remote from the > > main ground bus at the firewall, keeping it isolated and running its own > > ground wire to the firewall serves the same purpose as the firewall > > mounted bus: to prevent ground 'loops' (noise in the ground path showing > > up in undesired locations). Correct. See various examples in Figure Z-15 https://tinyurl.com/5wxzn7 The 'avionics bus' is a CENTRAL grounding point located in closest practical proximity to potential noise VICTIMS(generally all panel mounted). This ground point may well be electrically common to the airframe . . . this would be true if your airplane is all metal and the panel structure gets 'hooked up electrically' to the rest of the airplane. The magic things about an avionics bus: (1) central location to potential VICTIMS (2) single point for grounding all components in constellation of potential VICTIMS. (3) this ground is NOT SHARED with any potential ANTAGONIST (all those other things scattered around the airplane). If the airplane is composite, then you'll need to extend the avionics ground down to the firewall ground point with either a relatively robust bond wire (8awg is a bit overkill 12AWG is probably fine for modern suite of solid-state avionics). The avionics ground bus generally has lots of small wires none of which carries big currents. A product like this https://tinyurl.com/y44yngbm is much easier to mount in close proximity to the panel mounted electro-whizzies. For potential antagonists, grounding to the AIRFRAME can be managed with a product like this: https://tinyurl.com/y4gvepup But there's nothing magic about bringing all your airframe grounds to a single point. If you have an all-metal airplane, remote grounding of things like landing lights, strobe supplies, landing gear motors, batteries etc is quite practical. Insulating your ground system from the airframe is not recommended and has no demonstrable value. However, running all airframe grounds to the firewall thru- stud bus is not a 'bad' thing to do either. Bob . . . ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message aeroelectric-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/AeroElectric-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/aeroelectric-list Browse Digests http://www.matronics.com/digest/aeroelectric-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.