---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Wed 06/15/16: 2 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 01:12 PM - Re: Re: Review request for RV-9 Electrical System (G3X, GTN, etc) (Robert L. Nuckolls, III) 2. 03:38 PM - Re: Re: Review request for RV-9 Electrical System (G3X, GTN, etc) (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 01:12:41 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Review request for RV-9 Electrical System (G3X, GTN, etc) At 02:14 PM 6/14/2016, you wrote: > >OK, I think I see your point on not needing breakers and going with >fuses but I'm not 100% there yet. For my personal sense of comfort >I'd like to have items on the endurance bus on breakers. Does this >seem like a reasonable compromise? Compromise for what? If a breaker ever opens it means something is broke . . . and that something threatens to set a wire on fire. You want to give it a second chance? What items in your airplane are high priority equipment for comfortable termination of flight? From that list of items, how many of them can fail in ways that do not open a breaker? I can tell you that the vast majority of equipment failures never open a breaker . . . if that item is so necessary/useful that you're worried about being able to reclose a breaker, then you'd better have a plan-b . . . a back up for when the system decides to take a vacation. >It allows me to load-shed even further by pulling breakers if needed >and uses much fewer breakers and panel space. Thoughts? Load shed? What's the e-bus for? The LAST thing you should be doing in flight is running any kind of mental gymnastics calculated to reduce risks of dealing with some kind of failure. ALL such things are done at THIS phase of your design and fabrication. Should a necessary item go T.U. then you go to plan-b. If the item is not necessary, then there is no plan-B. The idea behind the e-bus is to do a two-switch load shed that either (1) does not overtax an SD-8 or (2) produces a KNOWN endurance value running battery only based on periodic capacity checks of your battery. Messing with any breaker or fuse in flight is a demonstration of poor planning that should have been managed during THIS phase of your project's development. Put the fuse blocks out of sight and out of mind. Deal with system difficulties as a pilot with a plan . . . not an in-flight diagnostician and maintenance technician. Bob . . . ________________________________ Message 2 _____________________________________ Time: 03:38:35 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Review request for RV-9 Electrical System (G3X, GTN, etc) >Could you elaborate on the e-bus switch vs relay? Up to what >amperage is it ok for it to be a regular switch? Sure. Any generic toggle switch of any rating is unlikely to be overstressed in your airplane. > I was planning on using the S700 Carling switches sold by b&c and > they claim 15A VAC but a quick search for them seems to bring up > more failure posts than details on the switches. Is there a better option? The Carling switches sold by B&C are direct descendants of those used by the hundreds of thousands on Cessna and Piper aircraft for decades. What details are you lacking? Keep in mind that nobody posts about their working switches . . . only the ones that have presented some problem . . . hence, a dozen posts of problems over a period of years may have the appearance of describing a quality issue. Switches, like every other device or bit of material in your project, are subject to failure . . . nothing lasts forever. Switches on personally owned airplanes have nearly zero service stress compared to, say the light switch in your bathroom. When doing the failure modes analysis for your project the questions to be asked are: How can this part fail? How will I know that it has failed? Is the failure pre-flight detectable? The answer to the third question drives your architecture and checklist decisions. Does failure present some degree of elevated risk for uncomfortable termination of flight? The answer to the fourth question drives your decisions for having a plan-b assuming that the part will fail. The beauty and comfort to be secured by an artfully crafted FMEA is that you don't care if the part fails . . . it's not an issue of increased risk. It's only effect is a cost-of-ownership. You might upgrade a part because you're tired of replacing it . . . not because it #@%%@% near got you killed. THAT is failure tolerant design . . . stone simple, cheap, easy to do. >For the fuse blocks I'm looking at the ones sold by b&c and they >come in different sizes. Does it make sense to have 2 or 3 to split >up the load a bit? Where should they feed from? i.e. should I have >one large wire for the firewall passthrough and then split that up >somewhere between the fuse blocks? Generally, each block represents one bus. In figure Z-13/8 you need three. Battery, Main and E-bus blocks. Other architectures will call for more or fewer blocks. Install blocks larger than needed today to allow for easy, future expansion. 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.