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RV-10 Electrical System

AviatorJ

Well Known Member
With the finishing kit on order and the cabin top ready to be put down it's time to start really thinking about the electrical layout of the project. I'm not a complete novice to electrical systems/wiring but this will be by far the most ambitious and complex project I've done. My plan is to do a much wiring as I feel comfortable with but will undoubtedly have a few of the wiring harnesses made professionally.

Working off some of the base designs in AeroElectric Connection I started working up a diagram in Visio. I found myself working in circles and decided to take a step back and determine component location and understanding what I'm putting in the plane before figuring out how it all connects and interconnects.... Understanding this will all change before the project flies.

I put together this very large picture to try and conceptualize where everything is going to be placed. If I'm forgetting, missing or something is completely off base I would like to know.



Once I understand the above I can start working out schematics. I plan on using both a VPX Pro for the electronic breakers and a Garmin GAD 27 for the discrete inputs into the EFIS. They share some duplication on trim and flaps control so not clear how I'll work through that yet. Would like to hear and possibly look at any drawings where someone has both of these installed. Actually I would also settle for a schematic where someone used a VPX Pro just to see how they did it. Anything would help,

Thanks!

Update 12/29/2017 -
It's been a year and a lot has changed. With the chance of someone pulling up this thread on a search I wanted to go ahead and post my near final drawing.



Operation%2BRV-10%2BElectrical.jpg
 
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Hey Justin.

I see that you list a GPS antenna on the belly. You're going to want it on the top of the plane (probably just a typo). Also, I've got 3 different GPS antennas on my 10. Your setup is a little different, as I don't have a GPS20a or a G5, and I'm not sure the requirements of those.

On the top behind the cabin top, mounted side by side:
--XM/GPS antenna that feeds the G3X MFD (and XM tuner in the MFD)
--GTN 650 gps antenna

And on top of my glareshield in front of the center support pillar:
--GPS puck (Garmin GA26C) to feed my PFD.

The reason for all of these is that a possible failure mode of a GPS antenna can cause interference to nearby antennas. My hope is that if this happens to an antenna on the top, my glareshield antenna will be far enough away to still be functional.

And in considering the wiring of the antenna cables, I tried to keep them away from other power wires as much as possible.
 
Thanks for the feedback Ed. That wasn't a typo just wasn't sure where to put it. Will move to right behind the baggage bulkhead on top.

Going to have to read up a bit more on antennas. Seems like an easy concept but for whatever reason I can't quite wrap my head around which are shared, which need their own, ect.
 
Justin, sent you a PM.

We are about the same place structurally but I am ahead in wiring and doing similar on my RV-10

E
 
Are you doing a GPS 20A and a GTN-650 for redundancy? Usually the GPS 20A is used as a source when a GTN or GNS is not available for ADSB out.
 
Thanks for the book reference. Will check that out.

Are you doing a GPS 20A and a GTN-650 for redundancy? Usually the GPS 20A is used as a source when a GTN or GNS is not available for ADSB out.

Actually thought the GPS 20A allowed you to get ADSB info on an ipad and your G3X devices. One aspect I'll do once I start the schematic is really try to understand what each component does.
 
Justin,

Looks like you're a couple months ahead of me. I've been working on the cabin top but my doors don't arrive until next week.

I noticed that you don't have a transponder on your equipment list. Check out the Garmin GTX45R. I believe (but don't know for sure) that you could get ADSB position ForeFlight. The press release says that it has wireless connectivity that can interface with ForeFlight. Also, you can hook the GTN650 to the GTX45R and forego the GPS20A.

My head has been spinning trying to figure out my electrical architecture. My '10 is going to be electrically dependent. EFII + All electric cockpit. I'm planning 2 batteries + 2 alternators. Unfortunately, the panel doesn't have a lot of room left over for circuit breakers. Between the VPX, GAD27, EFII Bus controller, fuses, ckt breakers and panel space, I've been struggling with drawing a line in the sand... At this point, I'm leaning towards the Bus controller, GAD 27 and a mixture of fuses (not on the panel) and a handful of ckt breakers on the panel in open space... Good times :)
 
Thanks for the book reference. Will check that out.



Actually thought the GPS 20A allowed you to get ADSB info on an ipad and your G3X devices. One aspect I'll do once I start the schematic is really try to understand what each component does.

May I kindly suggest that this approach is backwards? e.g., I would suggest determining what you need, what you want, and then determining how (or if!) you hook them together. That will also give you a count on serial ports and formats needed, see if it all works.
The Garmin GPS 20A is strictly a non-TSO GPS that Garmin says meets the GPS requirements for use with ADSB-out. It has nothing to do with ADSB-in. If you are planning on a Garmin 400W/500W/ or GTN series GPS navigator then that box can serve as the required GPS for ADSB-out; the 20A is just extra cost, extra weight, extra drag (antenna). I'd leave it out unless there is a compelling reason not to.
BTW, some GPS antennas require a ground plane, some do not. If yours needs one, then mount it at least 6" behind the bulkhead, not 'just' behind it, so you have a metal ground plane in front of it as well as behind it.
 
Going to have to read up a bit more on antennas. Seems like an easy concept but for whatever reason I can't quite wrap my head around which are shared, which need their own, ect.

Conventional nav (VOR, ILS, Glide Slope) radios can share a single antenna, with a splitter (I believe the GTN series has an internal splitter for nav/GS, so it already 'shares' the antenna). Otherwise, off the top of my head, I cannot think of any other antennas which are shared.
 
I noticed that you don't have a transponder on your equipment list. Check out the Garmin GTX45R.

Hey Eric, yah the 45R was on my list, just didn't make it to the drawing. Will swap that out now with the 20a since I'm removing that. Thanks!

May I kindly suggest that this approach is backwards? e.g., I would suggest determining what you need, what you want, and then determining how (or if!) you hook them together.

That's sort of what my approach to this exercise is. By doing the drawing and later the schematic I hope to educate myself on the particulars of equipment and then determine if it's something I want or need.

I really appreciate all the input. Already have revised the drawing three times.
 
Justin,

I'm at about the same stage as you are, defining my avionics and antenna locations in order to install the antennas prior to closing up the cabin top and forward tailcone top skin.

A couple of observations regarding your layout drawing:

You show the magnetometer located just behind the baggage bulkhead, but also show an air conditioner evaporator and I presume the fan that goes with it in the same area. This is likely not a good strategy, as the fan motor will create significant electromagnetic interference (EMI). I am also installing the Airflow Systems A/C, and after some research and communications with the G3X support have decided to install the magnetometer in the wing tip rather than the tail cone.

You show your roll trim servo in the left wing, but the roll AP servo in the right wing. Since you are using Garmin AP servos, they need to be connected to the trim servos, as the Garmin servo drives the trim servos. You might want to consider installing the trim servo in the right wing instead, in order to keep the wiring short and simpler.

I have placed my Nav antenna into the top of the vertical stabilizer, using a RAMI cat whiskers antenna. It fits nicely there without some of the issues others have reported with a wingtip nav antenna.

I don't see your GPS antennas shown on the diagram. You will need 2, and they need to be mounted on the top of the plane. Also, in checking with Van's builder support, they do not recommend mounting antennas to the fiberglass cabin top, nor adding any holes to the cabin top that are not shown on the plans. However, you should be able to place both GPS antennas on the tail cone top skins, and offset them on opposite sides of the centerline.

I'm also placing a Com antenna on the tail cone top, and the ELT antenna, as I believe there is room with adequate spacing between each antenna. My second Com antenna will be located on the bottom of the tail cone, a couple feet behind the A/C condenser scoop. I'm also planning the Transponder and ADS-B antennas on the bottom about where you show them, under the front seats on opposite sides of the aircraft.

Hope this is of some help. If you would like to "discuss" the A/C installation (I'm running the hoses down the sides, not in the center tunnel, and am in the process of installing the system components), or other ideas since you and I seem to be outfitting our 10s in similar ways, I suggest you send me an email.

Cheers,
Dave Macdonald

RV-10 Finishing Kit received Nov. 23, 2016
 
Dave-

Thanks for the plethora of information, very helpful! I had that same concern about the magnometer. Since you've done the footwork I will now install it in the left wingtip since I have an antenna in the right.

I've been talking to Bill about the AC. Saw Someone's pictures where they ran the hoses down the starboard side bulkhead. What's I'm not 100% on is how they go from the tunnel to the bulkhead... maybe inbetween the wing spars?

Wasn't aware that the Autopilot and trim servos connected to each other. That's an easy fix since the aileron trim assembly is just on an access panel.

On the GPS antennas I know I need one for the GTN 650 but what is the other for? Don't know the spacing requirements but if they both fit back there then I'll do the same as you.

On a side note what's the best practice on power wire separation? The way I understand it is audio and lighting should use shielded wire/cable and that power wires though have some distance from audio or antenna cables/wires. So do most people run their power and grounds down say the left side conduit and any signal based wiring down the right side?
 
Justin,

The second GPS antenna is for the G3X, as it needs it's own antenna. It also provides for XM reception by the G3X if you decide to subscribe. The G5 antenna is built in and so shouldn't require a separate antenna.

Separating high current power wires from communication and avionics wires is best practice. The more separation the better, but you should be able to run them down the same side so long as they are run in separate holes rather than bundled together with the other wires. Running them on opposite sides would be ideal, but may not be easily done and shouldn't be required.

As for the A/C hoses, I am keeping them entirely out of the tunnel. I've been working with Bill to replace the Z fittings with 90 deg. fittings to allow the condenser connections to come directly up into the space on each side of the tunnel under the rear seats. From there the right side hose runs back thru the lightening holes to the evaporator/dryer, and the left side hose runs under the seat to the left side wall and from there forward to the firewall bulkhead. There is another hose from the evaporator that runs up the right side wall to the bulkhead. I've just finished fabricating and installing access plates in the rear seat floors to allow future access to the fittings without having to drill out all the rivets and remove the seat floors.

Dave
 
Thanks for those who have sent me or made available their schematics to download. It's interesting to see everyone's approach and I find one thing for certain is there's no one right way to wire up a plane.

I've moved away from using both the VPX pro and a Garmin GAD 27. I've decided to go with the VPX only since there are some duplicating functions and I want the electronic circuit breakers. I know the benefits are all debatable but there are a number of core functions to the VPX that I want... and I learned the one feature on the GAD 27 I really wanted were the discrete inputs which apparently you can do with the G3X alone, just 4 inputs vs 10.

Now I'm working on my initial set of diagrams to include my panel layout. As I go through this process I write down questions I have and then research for the answers. Some of these are still opened and wanted to reach out to see what others have done.

Discrete Inputs - For those using a Garmin product, or something similar that allows customized alarms what have people used? I can select 4 items and I'm thinking these; Doors & fuel pump... not sure what else I would be interested in seeing on the screen.. maybe the status of the cowl flaps or ram air (Putting a Rod Bower ram air system in)... but I'll have switches below that to see if those are opened or closed, so may be over complicating things with that.

Battery Bus - Was thinking about putting in a battery bus (Fuse block) right off of the battery contactor where the battery connects. I could use this for anything I either wanted redundancy on if the VPX or something like the contactor goes south, or something I might want to turn on and off regardless of the Master position. An example maybe the dome lights.

On the 10 the battery and it's contactor is in the rear. So I believe if I wanted to mount the fuse block up front I would need another 4 awg wire to run up front. Or inversely mount the block in the back but then I would have to run multiple small wires up front for the devices.

Is this how must people with battery buses handled it? Wasn't sure if you could add a diode or resister or something to reduce the voltage and run a smaller say 18 awg wire from the contactor to the block. Might be over thinking it.

I might end up just hanging accessory fuse blocks off a VPX power output having it always on (When master on) and putting the devices off that. That's already sort of my plane for a lot of the extra servos for things like cowl flaps, oil damper, ect.
 
In may -10, I Have my AC in the tail aft of bulkhead and the magnetometer in the tail (in the the rear of Aircraft). All Garmin (dual G3x,750, etc...) no interference from the AC. All work fine. Solid, stable, fantastic!
 
Discrete Inputs - For those using a Garmin product, or something similar that allows customized alarms what have people used? I can select 4 items and I'm thinking these; Doors & fuel pump... not sure what else I would be interested in seeing on the screen.. maybe the status of the cowl flaps or ram air (Putting a Rod Bower ram air system in)... but I'll have switches below that to see if those are opened or closed, so may be over complicating things with that.

My 4 discrete inputs are:
Fuel Pump
Door switches
Heated Pitot annunciation
TOGA

You can also use one of the voltage sense pins as a "discrete". That's what I did for my cowl flaps. If that pin has over 6 volts, it "warns" that the cowl flaps are open. Below 6 volts, no warning. The only draw back is that on my electrical page, there is a cowl flaps gauge... but I just ignore that.

Battery Bus - Was thinking about putting in a battery bus (Fuse block) right off of the battery contactor where the battery connects. I could use this for anything I either wanted redundancy on if the VPX or something like the contactor goes south, or something I might want to turn on and off regardless of the Master position. An example maybe the dome lights.


I might end up just hanging accessory fuse blocks off a VPX power output having it always on (When master on) and putting the devices off that. That's already sort of my plane for a lot of the extra servos for things like cowl flaps, oil damper, ect.

That's what I did. I hung an 8 circuit accessory fuse block off one of the VPX circuits. I have it come on with my avionics master switch. I put things of lower importance on that block (like cabin lighting, lemo power, etc)
 
Thanks for the feedback Ed. I would of assumed that Pitot Heat on would of been a default input already. Either way I'll make sure I have it.

Was there any particular reason you tied your fuse block to the Avionics vs the Master switch? My thought it I would want power to the cowl flaps, oil damper ect before I start the engine... assuming I wait until after I start the plane to turn on avionics.
 
Almost a month to the day since I started this thread I have my first power distribution schematic draft and thought I would share it. Drawing it out in Visio really enhanced the learning process, forcing me to research components and wiring practices. I did a lot of reading, reached out to a number of folks and made countless revisions to get to this point.

Having it in an electronic format makes it easy to change, add or remove things as my ideas change or new products are released. Then obviously having it updated will help in the inevitable event that I will need to troubleshoot something after I'm flying.

There are a lot of devices on this project but I feel I have good balance between features, simplicity and redundancy. My only real mission requirement is enough power to get me out of IMC if something goes wonky.

I'm also going traditional magnetos with the hope of one day seeing the 6 cylinder P/Emags... but until then I'm most comfortable with traditional ignition systems. This makes complete electrical failure even less of a concern.

The centralized distribution method I'm going with is a VPX Pro. Their handy online planner tool was the first thing I started messing with. Easy to get in there, dump some equipment on it and tweak it around. I actually went back and forth between the planner and my drawing quite a bit. I think this is a dynamic link so will probably stay the same throughout my build.
Vertical Power Planner

Keep in mind the schematic is a work in progress so missing some details as I work through them. The bulk of it is there to a point if I was ordering avionics today this is the route I would go.



Happy New Years!
 
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Run some spares for CPI etc

Hi Justin,
My system is similar to what you have designed ( VPX-Pro, Dual alt,A/C etc)

I flew for two years and 300hrs before fitting the CPI, I had planned to do it one day and having the spare wires and circuits already run, made the install very easy. The CPI's have there own separate circuits,easy to run and terminate a bunch of spare wires now for a 'someday upgrade'

Cheers
 
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The alternator field and air conditioner wire sizes could be much smaller.

I'll change the field wires to 20 and the AC ones to 14. Might be able to go smaller, I think the AC run is probably a few feet since that evaporator sits on a shelf above the battery.

Hi Justin,
My system is similar to what you gave designed ( VPX-Pro, Dual alt,A/C etc)

I flew for two years and 300hrs before fitting the CPI, I had planned to do it one day and having the spare wires and circuits already run, made the install very easy. The CPI's have there own separate circuits,easy to run and terminate a bunch of spare wires now for a 'someday upgrade'

Cheers

I remember reading through your thread this summer on your install. I am going to have some planning for future electronic type ignition or other things.
 
For those that follow...

...thanks for posting all the good information. If you guys are emailing stuff around, I sure would like to see some example schematics for my own reference too.

Ashley,
Your 10 looks very nice. I thought long and hard about AC in my 10, but couldn't justify it. If I decide later on to go this route, is Don's system able to be retrofitted? Also, in your opinion, do you think it would be possible to put the scoop on the top of the tail cone, or is there something in the system that would not allow this type of an install? I am currently planning to have a belly pod on my 10, so I wouldn't be able to have a scoop on the bottom. My plan for AC is to use the ice cooler type of unit, so that it's removable, offering more flexibility and (if not needed) no weight penalty. Plus it's a lot cheaper too. However, I'm trying to keep my options open, if I decide that a dedicated AC unit is the way to go.
 
Mike,

Suggest you call Bill Genevro of Airflow Systems at 949-218-9701 to ask about an alternate mounting location for the A/C condenser scoop. I'm installing his system in my RV-10 as part of the initial build, but I understand that a number of people have installed his system as a retrofit.

As to the ice cooler type of A/C units, I have one I purchased this past summer at Air Venture that I have used a couple of times in my Grumman Traveler. While I understand some people find these meet their needs, I have found mine to be too much trouble for the little bit of cooling provided. Getting it into and out of the plane when it is full of ice water is difficult since my Traveler doesn't have a baggage door, so it might be less trouble on an RV-10. But here in the Houston area, 20 lbs. of ice provides less than an hour of cooling in the summer, and doesn't reduce my cabin temp. by very much. It is certainly a lot cheaper, and avoids the work to install the permanent unit, but for me I have decided that the Airflow Systems A/C should be a much better solution.

Regards,
Dave Macdonald
RV-10 Finishing Kit Rec'd Nov. 2016
 
I have Airflow A/C and love it. I ran the hoses down the right side. I did have to "Bulge out" my cargo compartment panel on that side to have room for the hose. I used split pvc pipe to do that and it just looks like a bumper/brace.
Having the overhead panel is nice to allow running a wire bundle through the windshield brace and through the overhead. I have the A/C wires, GPS wires, overhead lights, and three extra future use wires through there.

I have my dual Dynon ADAHRS stack mounted below the A/C shelf on one side and the blower on top on the other side. I get zero compass change on low and about 3 degrees on high fan. In reality, the magnetic issue is no big deal in a modern GPS airplane. The airplane is going to go where you send it. The only variable is a tiny error in your wind direction display. I placard to have the A/C off during ILS approaches.

The biggest interference I've found with the compass readout is if the rear pax shoulder strap cable sags down which is why I put the ADAHRS stack below the composite shelf. I've thought of having a sailboat shop fab me some cables in stainless, but a made a little cross brace on top of the shelf that keeps the cables from sagging down.

Electrically I really recommend Approach Fast Stack or similar technology for the panel. It really makes it easy.

I hate batteries because they're heavy and expensive so I went with one ship's battery and a Piper style external plug. I do have backup on the Dynons.
 
The centralized distribution method I'm going with is a VPX Pro.



Happy New Years!

Justin,

I note the backup battery for the GTN-650, the one ADHARS module, one EFIS display and the EIS module. I'm guessing that battery will provide ~45 minutes of operation. Is that the reserve you are looking for?

Carl
 
Not to get too far off track, but if you go with the Flightline AC system, it only has two louvers for the condenser and no scoop. You could put those louvers on the side or on the top, although the airflow on top may not be as much as the sides or bottom. They may even fit on the bottom with your pod, as they are only about 5 inches wide.

The diagram looks good. I'm curious if you would share the Visio file? If so, I'd love to take a look at it. I'm learning Visio now as an alternate to Express ECH. tim dot huneycutt at gmail dot com. Thanks!
 
Not to get too far off track, but if you go with the Flightline AC system, it only has two louvers for the condenser and no scoop. You could put those louvers on the side or on the top, although the airflow on top may not be as much as the sides or bottom. They may even fit on the bottom with your pod, as they are only about 5 inches wide.

The diagram looks good. I'm curious if you would share the Visio file? If so, I'd love to take a look at it. I'm learning Visio now as an alternate to Express ECH. tim dot huneycutt at gmail dot com. Thanks!

Thanks. I'd like a copy of your Visio file too, please. ppilotmike at gmail dot com
 
will provide ~45 minutes of operation. Is that the reserve you are looking for?

Was hoping the the largest 6ah version it would be closer to 1 hour. My backup to the backup is the G5 so combined that should be enough to get out of IMC. As I mentioned I have yet to fly in any hard IMC where I can't get out of the clouds by changing altitude a few thousand feet.

On the topic of AC I like the Airflow system because it's not electric and spreads the components out. I've riden in 172/182 with an electric AC and it wasn't all that impressive on the ground... which is where I want it. Since we're talking about it this is how I'm running my lines.



Bill has reviewed it and feels it would work. One of my rules of thumbs is don't install anything that will be completely closed up and uninspectable or workable later on. So I'm going to run the lines out the back and up the starboard side to the engine compartment. I'm going to make my HVAC friend help me out.

Also I'll email the Visio files that I've done so far for those that have asked. They're no where near complete but you'll have what I did so far.
 
Long runs..

Justin,

Those look to be pretty long runs of chiller lines. How are they insulated to make sure that the Frion (or whatever) is still cold when it gets back to the back of the plane? Especially, considering that the lines start in the engine compartment (=hot)??
 
Was hoping the the largest 6ah version it would be closer to 1 hour.
This is example of adding backup batteries as the the risk mitigation tool for single component failure scenarios. The alternative is to create flexibility such that the batteries have a primary and secondary function (e.g. both batteries on line for engine start and normal operations, split when needed to bypass around a fault).

I also was surprised on this 6ah backup battery's very high price tag.

Carl
 
Mike can't answer your question on how the lines don't get overheated in the engine compartment.

Carl- for me it came down to what I was trying to accomplish. I put a very low risk and impact of losing electrical or attitude indication in VFR and as I always say if I have an issue in IMC my #1 priority is to get out of IMC. So if I can have enough situational awareness to get myself out of the clouds then I'm not particularly worried about getting down safely.

Not being overconfident or passive but I've had an alternator go out, a vacuum pump go out while in IMC and have had to land without landing lights at night... it's not particularly fun to deal with these things but I didn't consider any of those an emergency.

The way I view my setup and in particular the IBBS is that it's the second to the last of 'if all else fails' list. The last on the list is the G5 which has it's own self contained battery. To get to that point I would of had to lose both ADAHRS, both Panels, both Alternators, the VPX, the contactor or the battery itself... Murphy's law says that may happen in that case I'm banking on the G5 to get me to safety... if the G5 goes out then lets hope I can feel the climb or descent enough to get out of the clouds without spinning!

I actually view this set up more as a Dual Alternator, Dual Battery setup. Maybe not with the all the redundancy of the design you sent me but enough to get me safely out without the weight hit.... already getting that with the AC.
 
Thanks for the file Justin.

FYI, Flightline has an electric version but most folks are going with an engine driven compressor, just light Air Flow. The only difference is lack of scoop. Both are good systems with folks happy with finished installs.
 
Thanks for the file Justin.

FYI, Flightline has an electric version but most folks are going with an engine driven compressor, just light Air Flow. The only difference is lack of scoop. Both are good systems with folks happy with finished installs.

Any idea why most prefer the engine-driven compressor? I would think the electric would provide more flexibility for location of components.
 
When I was shopping for an A/C system about 7 years ago, I passed on the electric system because it required a 24v system and a very expensive alternator and battery setup. I also felt like the old school automotive type system would be easier to resource and maintain.

I went with Airflow and the scoop because:

1: I didn't like the idea of sucking up exhaust laden air into the fuselage.

2: I actually like the looks of the scoop.

3: Bill returned my phone call first and I liked his pro-support attitude. He's been great to work with.

I know guys with Flightline who are quite happy with their system.

No A/C system is plug and play. It adds a lot more time to the build than initially appears, and requires initial tweaking and maintenance. However, after 300 hours I am very glad I did it. It isn't just hot (Arizona) weather where it is nice, the RV10 cabin is a greenhouse even in coolish weather and getting the humidity out also makes a much more pleasant flight and must be beneficial to the avionics and cabin materials. I recently returned from a trip to Baja and the amount of water pouring out of the vent on shutdown was amazing even though the OAT wasn't that hot at all.
I would guess that our compressor has run at least a third of our flighttime.
 
Should add three ANR's (or fusible links, or some other high reliability, high capacity circuit interruption device) to the alternator B leads and VPX feed, near the battery master.

To break the power connection without having to disconnect the battery?

I'm working through some other things right now, like going with illuminated rockers or toggles with a glare shield dimmable light. What to use on the AC power switch (relay or whatever) so I don't have to run 20 amps of power to the panel for the switch and then back to the tail.

I also received Marc's book in the mail yesterday so will be reading through that.
 
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To break the power connection without having to disconnect the battery?

Short any of them, and things get hot real quick. Although a well-trained pilot may eventually open the master contactor and disconnect the battery, there will be a time interval between the short and the switch movement. The process requires detection, realization, decision, and action. In the meantime, nothing good is happening. Think sparks and burning insulation, while your wife screams.

Ok, let's assume our superior pilot disconnects the battery with lightning speed...no indecision, no delay. Does it stop the sparks? Not necessarily. The alternator doesn't drop off line because the battery master was opened. Shutting down the alternator field supply will require another switch selection.

Short any of them with an ANL near the master, and the ANL melts immediately. End of problem; the short path is isolated from the rest of the system. If it was the live alternator B-lead, the VPX will alert a voltage drop, and the pilot brings the other alternator online. If it was the standby B-lead, its ANL pops and nothing else happens. If it was the VPX power feed, the panel goes dark. The pilot switches to the IBBS for power and pushes "Nearest" on the GPS.

http://www.bandc.aero/anlcurrentlimiters40athrough130a.aspx
 
GAD29 interface

Justin,
I noticed you're utilizing the IBBS backup battery for the GTN, GDU, GSU 25, and the GEA 24, but no similar/equivalent backup for the GAD 29. As I'm building an -8 with similar components and architecture and haven't flown behind a GTN yet, I'm curious as to how much functionality would be lost between the GTN and the GDU in the event of a main bus failure. Would it be significant if in IMC conditions? I intend to post the same question to the G3X experts at Garmin and maybe others here who have experience with the GTN and G3X will chime in, but wanted to know if not having a backup power source for the GAD 29 was a consideration.
Thanks for posting your design-
J. Baker
 
I fly with a stand alone GTN 650 in my current plane. By itself it has a lot of functionality so much that I'm not even full aware of what I'm missing out on by not having an ADAHRS or Glass Panel of any type. By itself I use it as my sole IFR Navigator. When having some hand flying fun in IMC it's included in my scan and will fly a full approach on it.
 
Was out of town for a week on business and used my flight and down time to read through Marc's book. Was initially put off with it only being 80 pages but once I got into it I found it had quite a bit of information. I made a series of notes and today I updated my Power Distribution drawing accordingly.

Want to ask about sizing an alternator. How do you speculate the pull on sporadic amperage outliers like Radio Transmitting, Strobes, ect? Was thinking a primary Plane power 70 amp with a 30 amp backup.. but wanted to run some numbers to make sure that was going to work.
 
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Resurrecting this thread vs starting a new. I'm diving back into the electrical planning this month and I plan to get everything worked with and ordered from Stein in January. I'm trying to simplify everything as much as possible but still have a capable IFR setup with redundancy for safety. The catch all on my setup is the Garmin G5-- If ALL else fails it has an independent battery that should keep it powered for 'up to 4 hours'. So here are the changes I'm thinking and wanted to get any feedback while I work through this.

- Start Button - I'm backing off my original setup of having the mag switches function as the engine start sequence. It's still a neat idea but adds some complication and also requires you to have your hand off the stick to start the plane. Now I'm going to put the start switch on the stick. The VPX will disengage the starter function once the planes running so I'm less concerned about accidentally hitting the button in flight. My question is do I put this on both sticks or just one?


- Dual Batteries - Technically a setup with IBBS could be considered two batteries I suppose. However the IBBS only powers a handful of devices in the case of an outage, but is somewhat independent of the VPX, so if that drops I can still get power to a G3X, GTN 650 and a few other things. Lately I've been thinking about instead doing two EarthX 900 batteries, but even with a drawing from Carl I can't tell if this is more complicated or not... to get away from the single point of failure of the VPX it seems I would have to have a separate essential bus. Am I missing something?


- Dual Alternators - If I can get an hour or so of extra power from the batteries and up to 4 hours on the G5, do I really need an extra alternator? I've had an alternator go out a few times while flying and it's always a bit of a non-issue. My gut is saying do it anyways because you're only talking a few extra wire runs and it should extend your backup endurance by quite a bit.


Any feedback will be appreciated. Thanks!
 
- Start Button - I'm backing off my original setup of having the mag switches function as the engine start sequence. It's still a neat idea but adds some complication and also requires you to have your hand off the stick to start the plane. Now I'm going to put the start switch on the stick. The VPX will disengage the starter function once the planes running so I'm less concerned about accidentally hitting the button in flight. My question is do I put this on both sticks or just one?

Why re-invent the wheel and deal with the trouble of extra wiring in the stick. Save that button for something you use more than once a flight.
You really need a handle on the throttle and the starter switch. That is all; so go sit in a dozen certified or existing RV planes and see which solution you like. Button position to the left of the stick, in the center high on the dashboard...

- Dual Batteries - Technically a setup with IBBS could be considered two batteries I suppose. However the IBBS only powers a handful of devices in the case of an outage, but is somewhat independent of the VPX, so if that drops I can still get power to a G3X, GTN 650 and a few other things. Lately I've been thinking about instead doing two EarthX 900 batteries, but even with a drawing from Carl I can't tell if this is more complicated or not... to get away from the single point of failure of the VPX it seems I would have to have a separate essential bus. Am I missing something?


- Dual Alternators - If I can get an hour or so of extra power from the batteries and up to 4 hours on the G5, do I really need an extra alternator? I've had an alternator go out a few times while flying and it's always a bit of a non-issue. My gut is saying do it anyways because you're only talking a few extra wire runs and it should extend your backup endurance by quite a bit.


Any feedback will be appreciated. Thanks!

Extra batteries and dual alternators should largely depend on the kind of flying you do. If a VMC flyer, keep it as simple as possible. If IMC of marine layers on the coast, you may need to fly hours to get to VMC conditions, in which case redundancy matters. Dual batteries and dual alternators is the "ultimate" expression of this.

Tim
 
Start button - My preference is for it not to be on the stick, but if it was, I would only put it on one. I also have a button that interrupts the ground to all functions on the right stick, which effectively disables all functions. Great for flying Young Eagles and other youth in the front seat.

Batteries - I have two Odyssey 680s.

Alternators - I have two as well.

For the last three years, it's worked as designed. I did have to modify the schematic a bit from the VP/X manual to accommodate two batteries and alternators. I have one switch that enables one or the other alternators, so that I can never have both enabled at the same time. Another switch isolates or puts in parallel the 680 batteries.
 
Recommend you not put the starter button on the stick. I did this in my first RV and quickly found how easy is was to bump it while the engine was running. It got disconnected and the other two RVs never had it on the stick.

As I have posted in the past, two PC-625 batteries are easy to mount in the stock RV-10 battery position (some minor modifications to the mount needed) and if wired with some thought both are available for start but either can power the panel if you have a fault someplace. No other backup batteries required or desired.

On the RV-10 I did later add a standby alternator that feeds Avionics #1 and Avionics #2 via isolation diodes. I did this as I found the full glass panel and especially the GTN-650 to be power hungry - so the batteries gave me about 2 hours of reserve capacity. I wanted 3, so the standby alternator was added. I?m still on the fence on adding this for the new RV-8 project.

Carl
 
Okay no start button on the stick.

I'll have to do some more thinking about the dual standard batteries vs a standard battery and the IBBS setup. I'll push forward with the 2nd alternator, seems like relatively uncomplex to add.

Here's an add on question I just thought of while staring at my panel mock up. Is it common to have a power switch for your Autopilot Servos? I had planned to do one but in looking at other people's set ups it seems hit or miss.
 
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Second alternator of battery?

...

Extra batteries and dual alternators should largely depend on the kind of flying you do. If a VMC flyer, keep it as simple as possible. If IMC of marine layers on the coast, you may need to fly hours to get to VMC conditions, in which case redundancy matters. Dual batteries and dual alternators is the "ultimate" expression of this.

Tim

Interesting point.

EFIS redundancy is usually provided by dedicated back-up batteries anyway, so your scenario really applies to the rest of the electrical stuff on the plane.

If you must fly IFR to get to VMC conditions then it implies your engine is running... :) and a second alternator would do the job of keeping the avionics going.

If the engine isn't running then the extra capacity of a second battery is probably not useful.

Does the above really say that a second alternator is more useful than a second battery if the EFIS systems take care of themselves in a "electrics out" situation?
 
I've always felt a second alternator/dynamo is of more value than a second battery for the exact line of reasoning above. How long do you need backup electrics to last in what has become a glider?

This assumes you have a way to know at the start of the flight that both alternators are functional, and that either or both could perform their function absent a battery to serve as a load/filter. Much has been written about this, but I remember little of it. I believe the dynamos like SD-8 employ a large electrolytic capacitor to mitigate the effects of taking the battery load off line.
 
Here's an add on question I just thought of while staring at my panel mock up. Is it common to have a power switch for your Autopilot Servos? I had planned to do one but in looking at other people's set ups it seems hit or miss.

No separate switches. I'm not sure why I would want them.

I have power to the Autopilot servos group powered through the VPX with an "Avionics Switch". I can still access the individual output for each individual servo through the VPX page to override the Avionics switch on single outputs.
 
Interesting point.

EFIS redundancy is usually provided by dedicated back-up batteries anyway, so your scenario really applies to the rest of the electrical stuff on the plane.

If you must fly IFR to get to VMC conditions then it implies your engine is running... :) and a second alternator would do the job of keeping the avionics going.

If the engine isn't running then the extra capacity of a second battery is probably not useful.

Does the above really say that a second alternator is more useful than a second battery if the EFIS systems take care of themselves in a "electrics out" situation?

Most EFIS backup batteries for the primary EFIS is 45 minutes or so.
In a congested area like LA, Boston, DC... I would not only want to keep the PFD running in the common situations, but also NAV/COM and transponder. I do not enjoy the idea the a F16 joining me on a downwind flight :D

If I was a mid-west, VMC, daytime flyer; I would go with a single lead acid battery and a single alternator. This will handle almost any emergency, lead acid is bullet proof simple to monitor and be proactive on replacement when losing charge.
If night flying, I would add a backup alternator and setup the start procedures to run the system off the backup alternator for most of the taxi to test the system before starting the primary alternator.
If either coast, or flying over IMC, or dual electronic ignition; I would go with what I consider the ultimate solution. Dual batteries and dual alternators. One lead acid battery hooked on the main bus and is the ship primary source of power. A Li polymer battery connected via diodes for charging and when armed to provide the bus with power. Primary alternator set to slightly higher voltage than backup for automatic take over.
Reason I like the lead acid battery in the system; they handle transient current, voltage and spikes and drops much better than Li polymer batteries; and if a supper high spike do not go off line or blow up very easily. This offers the best "buffer" to protect the much more expensive electronics in the cockpit and helps ensure they are still working when the second battery and/or alternator comes online.


Tim
 
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