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My RV-8 Wiring Schematic v1.00

One thing that comes to mind from flying G1000 Cessnas, from looking at your diagram if you lose the M-bus then all you'd have is the E-bus. So that would leave you with GPS, Boost Pump, Flaps, etc. It looks like you're making a glass PFD, so do you have backup instruments? For Night VFR having some illumination would be good too.

It's a good exercise to go over a lot of what-if's and failure analyses. If there's a short in the comm power and that trips a breaker, what else do I lose? What if the alternator is stuck over-charging? What if the pitch servo is stuck running one direction?

Have you crunched any numbers on what power you'd expect the avionics to draw? A quick calculation of what you'd plan to use and how much current it would pull can help you pick the wire gauges for your wiring harnesses.

Hope this helps!
 
Thanks for the input...

Thanks for the reply wildblue37,

I forgot to mention that I have a steam driven back lit Altimeter and Airspeed indicator. Here is a link to my panel plan:

http://www3.ns.sympatico.ca/jeffrey.mitchell/RV8%20Forum%20Pics/Panel%20RV8%20JM%20002.JPG

Illumination planned is a strip of white LED's mounted under the glare shield and an LED map-light (plus flashlight of course).

If the VP-CU (main bus) is offline I have a back up circuit (bypassing the VP-CU) to allow the alternator to energize the E-Bus. It's internally regulated and I have a 60 amp ANL fuse to handle an over-voltage scenario.

I definitely have to run some what-if's and failure analyses.

Still have to confirm AWG for all runs. I don't actually have all my components yet.

One small observation another forum member made is the battery polarity is depicted incorrectly. I didn't notice that when I pasted the battery symbol.

Your comments do help, thanks kindly.
 
Electrical system

Jeff
I've noticed on your shematic that you're planning to install ''seat heating '''
You could save yourself the trouble and time just by installing sheep skin seat cover in your airplane.They are warm in the winter and cool in the summer to sit on and not to mention confortable.
I should know as I spent 15 hrs + sometimes sitting on them..

Just trying to save you time here ;-)

Bruno

P.S: I'll keep a copy of your shematic for future reference as a wiring job is in the plan for next spring..
 
Seat heat

Hi Bruno,

Great idea, but too late for me. My seats are done and already have the heating pads installed.

If I had to do it again I would leave the heating pads out next time. Sheep skin covers are nice (I also have them at work) and don't require any wiring!

Thanks for the input.

Bye for now...
 
Question

jmitchell said:
Thought I would put it out there for constructive criticism.
Click to expand...

Jeff,

It looks like you are feeding the alternator field from your E-Buss. What failure mode (scenario) is that for, battery contactor failure? I think of an E Buss coming into play if I have an alternator failure and need to minimize the battery load until I land. If I had a battery contactor failure I'd want to power the E Buss through an appropriate switch that bypasses the battery contactor.

Pardon me if I missed something, this just jumped out at me with a cursory look.

Nice drawing, BTW.

Don
 
VP-50 Back up circuit for Alternator field wire...

Hi Don,

One of the main goals of my design is to prevent being left AOG in the event of a failure of the VP-50 switch unit or VP-50 control unit.

When those units are serviceable the alternator field wire goes to the VP-50. If one of the VP boxes should fail I have a back up circuit for another field wire to the aux bus (with a flip of a switch) which keeps the aux bus energized from the alternator independent of the VP units.

This way I still have power for the boost pump, alternator control, flaps and GPS with no VP CU.

The other items that are on the aux bus are really just there because taking power from this physical location is more convenient than going all the way to the VP-50 CU. It's why I call it an 'aux' bus and not an 'essential' bus.

Anyway, when I ordered my VP-50 I was told it was the last unit in stock and there could be a lengthy wait for some components on backorder for VP to be able to build more units.

I want to be able to fly in the event a replacement VP unit takes awhile.

Thanks for your question and comment.
 
Jeff, we have service parts and units set aside for that. Production parts for the -50 are an issue we're working through right now. ;)
 
Just some other thoughts to consider...

What is your plan if you are AOG because of a failed engine monitor? Ignition system? Flaps motor stuck in the down position? Battery contactor (most FBOs don't have 12v parts in stock)? Fuel pump? etc.

Point is, there are lots of things on your plane that will cause you to be AOG and it doesn't make sense to carry spares or install a backup system. So why add the extra complexity in this case? That said, we do recommend backups, but only for critical avionics to help you to continue to fly safely. A similar example is putting in a backup EFIS in case the main EFIS fails. Makes sense for IFR but perhaps not so much for VFR.

In the end, each builder has his or her comfort with things and needs to build the plane that they are most comfortable with and meets the needs of their mission (that's my way of saying this is just my opinion).

BTW, reliability calculations (MTBF) show that Electronic Circuit Breakers are 50 times more reliable than mechanical breakers.
 
Panel

Not wiring -but I think compass not used much. I mounted mine in the right side panel after checking for mag interference there. Would the current compass spot serve well for G meter? Have fun designing. It's almost a shame to be done with that part and be somewhat locked in!
 
Lost sight of the mission a bit...

Thanks for the comments, I appreciate it.

I should have mentioned Vertical Power keeps spare parts to support existing VP-50 units in stock in my earlier post. I forgot about that, sorry.

Of course Marc is absolutely right about having several other items that would keep me on the ground that I don't have backups for.

It's a delicate balance between too many backup systems (and the weight / complexity / cost associated with them) and not enough.

My day job is flying heavy transport helicopters to offshore oil / gas platforms off the Canadian East Coast in the worst kind of weather. The aircraft I fly has 2 of everything and 3 of the really important things! I am accustomed to a certain level of system redundancy.

In addition every AME I know and solicit for advice on my electrical system only have experience working on complex transport machines. They have no idea what a day VFR sport plane mission is all about. Some can?t get over the fact I?ll only have one engine out front! There is almost zero general aviation here in Halifax to draw on let alone sport aviation.

Anyway, the only VP-50 backup circuits I planned initially were to the boost pump, and flaps sourced from the battery in the unlikely event the VP-CU became U/S.

But when I started working with the VP-50 load planning worksheet I realized I was too close to my alternators limit and was running out of available VP-50 power pins. Mostly because I have heated seats (front /back) and two auxiliary power outlets to run heated (motorcycle style) vests, electric flaps, boost pump, and landing light. Cumulatively these items draw a lot of current.

My plan then evolved to incorporate an auxiliary bus (Fuse block) energized by both the alternator and battery to take care of the seat heaters, and boost pump (B/U) etc. At this point I realized the physical location of the aux buss (on the side wall under a switch console by my right knee) would make it convenient to add other items that would have had wires running in close proximity to it if routed to the VP-50 CU.

So for convenience I decided to just power those items from the aux buss as well. This lightened the load on the VP-50 and freed up some pins for future use.

My plan is still fluid and I?m fortunate to have VAF forum members and especially Marc Ausman offer comments, observations and suggestions for the purpose of improving the system.

Given Marcs recent illumination of the fact there are many single items that can ground my RV-8 I need to rethink my strategy a bit. I have to keep in mind the mission is Day/Night VFR. Not heavy weather IFR.

Thanks again, keep the comments coming!

P.S. I agree the compass has little use, but I don?t have anything else in mind for that panel position at the moment and my Dynon D-100 has a G-Meter.

P.S.S. Here is a link to my updated schematic as of yesterday. (Now I have to change it!)

http://www3.ns.sympatico.ca/jeffrey.mitchell/RV8%20Forum%20Pics/General%20Schematic%20V1.02.vsd
 
"http://www3.ns.sympatico.ca/jeffrey....ic%20V1.02.vsd"

When you post schematics, could you save as PDF, PNG, JPEG, or something else generic? Visio is expensive!
 
ergonomics

Clean layout. However I would switch the transponder and SL40. In an -8 your left hand will be free to switch radios and turn on lights when flying down low near airports. The transponder is basically set and forget. I would put the GPS on the left also however compromises must be made for making things fit nicely.
Obviously it will work anyway you go. Just my .02 worth.

David
 
I agree, beautiful layout, and very clean. But I also agree that you might be happier the VP over on the right, and stack the Garmins all over on the left side.
 
Nice panel

Beautiful panel layout. I agree with the other post about putting avionics that require tuning, etc. on the left side so that you can do them with your left hand, while keeping the right hand on the stick. For the same reason, you should put your flap and boost pump switches on the left side of the panel as well. That way, your left hand can adjust throttle, mixture, prop, flaps, and boost pump, while the right hand stays on the stick.

One other suggestion is to replace the whiskey compass with a G-meter. With two remote magnetometers on the Dynon's, you do not need a whiskey compass unless you plan to fly IFR. You will want a G-meter, however, if you intend to do aerobatics. Do to the variations in elevator stick force with CG differences in the tandem RV-8, it is a good idea to watch a G-meter, while pulling G's. Putting the G-meter up high on the panel makes it easy to see during aerobatics. Note. I have a Dynon in my plane and it is much easier to watch an analog G-meter than to watch a small digital readout on the Dynon during aerobatics.

Finally, you might consider putting a switch on the stick to swap active and standby frequencies on your com radio. That is a great convenience while formation flying and at other times.

Cheers,

Dan Miller
RV-8 N3TU 890+ hours of fun
 
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WHISKEY COMPASS

Dan
''One other suggestion is to replace the whiskey compass''

I'm not 100% positive on this one but I believe it is a requirement in Canada to have one either IFR or VFR..Please correct me if I'm wrong and I will be the first one to take it out..;-)

Cheers

Bruno
[email protected]
 
Point(s) taken.

Thanks for the suggestions everyone.

I agree and moved the radio and GPS to the left side and put the VP-50 and the Transponder on the right.

My flap switch is on my Infinity grip (protected by a Vfe speed switch) and the boost pump switch is on the VP-50 control unit.

As for the G-Meter; sounds like a good idea. I agree analog needles are easier to interpret than a digital value. I have to do more research but I'm pretty sure a whiskey compass is required even for VFR in Canada (don't ask me why). If the compass readout in my Dynon EFIS will suffice I will delete the whiskey compass and put something more useful in it's place.

The radio frequency flip flop feature would be nice on the stick but the Garmin SL40 doesn't support it. The SL30 does, but I don't need the VOR.

My master switch (next to the black trim knob on the right sub panel) is a cam-lock style to prevent inadvertent activation.

Here is a pic of the revised panel:

http://www3.ns.sympatico.ca/jeffrey.mitchell/RV8 Forum Pics/My Panel 11 Dec 2010.bmp

Thanks again!
 
In practice.....

cdmiller said:
... I agree with the other post about putting avionics that require tuning, etc. on the left side so that you can do them with your left hand, while keeping the right hand on the stick.
Click to expand...

Early on in my panel design, I had my radio stack (radio, transponder, GPS-nav) on the right. Several people suggested moving it to the left, based on this logic, and I did. I am a more dominantly right-handed stick than most (to the point that I would fly an RV-7 from the right seat!) so this seemed like solid logic.

BUT in practice, I find myself, more often than not, switching to left hand stick and reaching across to the left side with my right hand to tune the radio, set a txpr code, or select a feature on the GPS. It's a matter of fine motor dexterity. The buttons are small, and they are moving around in turbulence. Even though I am not as smooth flying with left-hand stick, my left hand is better on the stick than it is trying to push small buttons.

In hind sight, I wish I had kept the radio stack on the right.
 
Last edited:
That is why I had the GPS and Radio on the right in the first place. I figured I would want to use my dominant hand to fiddle with them.

However, at work I sit in the left seat as often as I do the right so I am accustomed to using my left hand to play with the FMS etc. without any problem.

Putting my GPS and Radio on the left and the VP-50 and Transponder on the right solves a couple of other issues I had with mounting the VP-50 control unit (Red Box) behind the panel so I am going to stick with this plan.

Thanks for your comment.
 
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