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essential bus usage

kentb

kentb

Well Known Member
I am wiring my plane using the aeroconnection essential bus/main bus system.
I am now faced with the desission about what is essential and what is not.
I am using fuse blocks for power and have 20 for the main bus, 10 for the essential bus and 6 for the battery bus. I will have a 60 amp alt plus an 8 amp standby alt. Single battery.

Feedback from other would be welcome.

This is what I think it should look like:

Battery bus:
1. cabin lights
2. electronic mag
3. essential bus
4.
5.
6.

Essential bus - all items can be switch off to reduce load except the T&B
1. Efis Lite
2. Turn & bank
3. GNS 430 (com)
4. GNS 430 (nav)
5. engine monitor (ACS 2500)
6. pm6000m
7. AT50 transponder
8.
9.
10.

Main bus
1. Efis Sport
2. A.P.
3. SL30 (com)
4. SL30 (nav)
5. Nav lights
6. Landing light
7. Taxi light
8. strobe light
9. pitch trim
10. roll trim
11. starter
12.
.
.
.


Kent
__________________
 
Minor Comments

Kent,

If you're using the GRT EFIS's, each Display Unit can be fed from three different sources (they are internally isolated), so you can run power from both Main and Essential busses if you want no-brainer redundancy. I also put my A/P on my essential bus, but that is becasue it is the Tru-Trak Pictorial Pilot, which also serves as T&B.

Paul Dye
 
Other sources

Aviation Safety had an article about 7-8 months ago reguarding the best redundancy between the certified glass cockpits.(Lancair vs Cirrus vs some others) They felt the Cirrus had the better set-up and include a schematic of the 2 alternator and 2 battery system. I have it in the bowels of this computer as a pdf file. I'll try to figure out how to post the image.
 
Electrical busses

My bus breakdown plan is essentially the same (slight difference in equipment). Don't forget your clock will also be on the battery bus.

Dennis Glaeser
7A Wings
 
Here is my $.02 worth:

Essential bus - all items can be switch off to reduce load except the T&B
1. Efis Lite
2. Turn & bank
3. GNS 430 (com)
4. GNS 430 (nav)
6. pm6000m
7. pitch trim (The trim isn?t used much and make it much easier to fly in IMC.)
8. roll trim (Same as pitch trim)
9. Landing light (Not used much but you will want it after coming out of the clouds w/ an electrical problem at night. Might save you from having to do a missed approach.)
10.

Main bus
1. Efis Sport
2. A.P.
3. SL30 (com)
4. SL30 (nav)
5. Nav lights
6. Taxi light
7. strobe light
8. starter
9. engine monitor (ACS 2500) (As long as the thing up front is making noise, you know your engine is working.)
10. AT50 transponder (ATC can still paint you with their radar, they just won?t have an altitude reading on you.)
 
I also have 6 slot battery bus, 10 slot e-buss, and 20 slot main.

From the top of my head...

Battery has:
Always live Dynon
E-Mag
P-Mag
E-buss Feed

E-Buss has:
SL30 Com
SL30 Nav
GPS296
PM3000 Intercom
Dynon
GTX327
Pictoral Pilot
Fuel Pump/Primer
(all these items can be turned off by themselves if need be also)

Main has:
All lights, Pitot heat, marker beacon, etc.

Scott
#90598 - Only a couple items left to be wired and then FWF
N598SD reserved
 
First off, take the transponder OFF the e-bus. Especially with the Narco, it's a power hog, and if you get in a pinch, you don't need it. I don't know that much about the way you guys design your electrical systems, but normally the starter runs a big fat #4 cable straight from the master solenoid right to the firewall, where you mount the starter solenoid, then straight on to the starter. I don't know of a bus that would handle the current necessary for the starter. Another thing is the audio panel, assumeing complete power loss, the PS6000 SHOULD revert to com1, therefore powering it in an emergency system is unnecessary. Personally, if you have electric trim only, I'd be running that to the e-bus. I know that trim forces can be overpowered in the RV, but I wouldn't want that extra distraction in a flight thats already going rough. At least run pitch trim to the e-bus.
 
Is essential bus necessary?

My current design includes an essential bus, but I'm kind of wondering if it is really necessary. I might just have two busses, and if I need to conserve power, I'll just turn off what I don't need.

A comment on your system - I would keep the AP on the essential bus. Turn it off if you don't need it, but have it available if things start getting busy.
 
The POINT of the e-bus

Mickey,

The whole point of the e-bus is that it lowers your workload. It allows you to instantly (by flipping one switch) shed unnecessary load. It takes the guesswork out of the equation.

If you're flying along in the soup and your alternator dies, do you really want to spend mental cycles deciding what to turn off, and then waste "scan cycles" being distracted by having to flip several switches?

I'm not saying it's all that difficult, but it sure makes it easy if you calculate your essentials up front -- and then in the event of a failure you literally just flip your master switch off (my e-bus switch is always on during flight anyway to simplify the process).

If you'll never fly IFR, and if you don't see value in simplifying the process, then sure...consolidate your buses.

)_( Dan
RV-7 N714D
http://www.rvproject.com
 
Great Discussion

This is really a great discussion. Dan is right. The whole purpose of the E-bus is to make it a no-brainer in the event of a alternator failure during a "worst case" flight.

Keep in mind that whether you need an E-bus or not, and what to put on it or leave off of it, is determined far earlier in the process. What kind of flying are you planning to conduct and how much battery capacity to you have available? These are questions that need to be answered first. You can supplement your electrical design with another battery or another alternator. Maybe just a battery for your EFIS or AP. If you're strictly day VFR and you never scud run or fly in bad weather, then it probably doesn't matter much. Hard IFR is another matter. Most of us are somewhere in between. Then the question becomes what do I want to do if my alternator(s) go TU? Do you just want to land at the nearest large airport and repair? Do you want to continue your flight for 1 hour, 2 hours, 3 hours? Then you need to plan your battery capacity accordingly.

Theroetically, if you have enough battery capacity for 3 hours of flight for all your equipment, you don't need an E-bus. If you go with a smaller capacity battery to save weight and/or reduce costs, then an E-bus can save your butt or at least, reduce your hassle to a minimum.

In my design, I added a 20 AMP backup alternator to the vacumn pad because it gives me unlimited range with the load on my E-bus. No matter what happens to the primary alternator, I can continue my flight on the backup and E-bus. If I don't like living without something on my primary bus, I can take my time to select a destination for repairs. If both go TU, I have approximately 1 hour of flight time to decide while using the E-bus.

To be honest, a dual battery system would be more cost effective, but I didn't like the additional weight and ongoing cost of battery replacement. You do replace your battery every year or two don't you? You should, but that's another discussion.

Fly safe!
 
Scott DellAngelo said:
I also have 6 slot battery bus, 10 slot e-buss, and 20 slot main.

From the top of my head...

Battery has:
Always live Dynon
E-Mag
P-Mag
E-buss Feed

E-Buss has:
SL30 Com
SL30 Nav
GPS296
PM3000 Intercom
Dynon
GTX327
Pictoral Pilot
Fuel Pump/Primer
(all these items can be turned off by themselves if need be also)

Main has:
All lights, Pitot heat, marker beacon, etc.

Scott
#90598 - Only a couple items left to be wired and then FWF
N598SD reserved
Click to expand...

Scott--

You need to move the emag and Pmag off the battery bus. They differ from other electronic ignitions in that the are always "on" even if you turn the spark off with the P-lead.

If you leave them on the batt bus, the battery will drain overnight, causing you to use foul language and waste time troubleshooting. Go ahead, ask me how I know ;-)

I would just put them both on the main bus--the Pmag will run the engine fine if you lose power after it's running.

James Freeman
 
Last edited:
f1rocket said:
Theroetically, if you have enough battery capacity for 3 hours of flight for all your equipment, you don't need an E-bus.
Click to expand...

A friend pointed out that this is true - unless your battery contactor shoots craps! In that case, the e-bus still lets you get power to the items that aren't wired directly to the battery bus.

mcb
RV-7 emp
 
Thanks for the help!

Lots of great ideas to digest. I will look at the impact of moving the transponder and PM6000M off the E-bus and moving the trim on to it.

Randy, I will be studing your diagram.

Another benfit of the E-bus is that the battery contactor is not using 1 amp with it is in use.

Dan, I hadn't though about leaving the E-bus switch on all the time. Did you wire you system like appendix Z-13 of the "connection"?

James, how was you e-mag wired. Didn't the switch remove power from the EI control unit?

Kent
 
flyeyes said:
Scott--

You need to move the emag and Pmag off the battery bus. They differ from other electronic ignitions in that the are always "on" even if you turn the spark off with the P-lead.

If you leave them on the batt bus, the battery will drain overnight, causing you to use foul language and waste time troubleshooting. Go ahead, ask me how I know ;-)

I would just put them both on the main bus--the Pmag will run the engine fine if you lose power after it's running.

James Freeman
Click to expand...

Really??? Well good thing where my busses are located I should just be able to move the wires over from one to the other and be done. Since I don't have them yet, I just made an assumption on where to power them.

Scott
 
I used Z-11

kentb said:
Dan, I hadn't though about leaving the E-bus switch on all the time. Did you wire you system like appendix Z-13 of the "connection"?
Click to expand...

My system mimics Z-11, almost exactly. KISS. Just a fresh PC680 battery and no dual anything (overkill imho). The Dynon has its own internal battery backup. As I've mentioned before, I see lots of VFR-only pilots flying VFR-only equipped aircraft...with dual alternators. I have to laugh when I see that. :)

As for the e-bus switch...
As soon as I start my engine, I flip my master up the rest of the way (it was on battery-only for start), and I flip my e-bus switch on. There is absolutely no harm in doing so (imho). And in fact, by connecting the alternate feed for the e-bus, it eliminates the voltage drop normally associated with powering the e-bus through the diode. Probably reduces/elminates the diode heat as well. But most importantly, as I mentioned in my last post, it means I can just flip the master off at any time and my essentials are good to go. One switch flip instead of two.

Also want to throw in my 2 cents about the transponder. Leave that puppy on the e-bus! There will be cases where you will need it, even if you're running only on the e-bus...specifically the case of an alternator failure when IFR. It's the same sort of logic as the flap motor, trim, fuel pump, etc. Those are things you won't necessarily need constantly, but when you do, you don't want to have to flip the master back on just to use 'em. As somebody else mentioned, it may have been your master contactor that crapped out. And if not, the contactor itself is consuming valuable current.

This is just my opinion. To go along with it, I may as well enumerate my bus stuff:

Battery Bus:
  • Dynon keep-alive
  • Lightspeed ignition
  • E-bus alternate feed

Main Bus:
  • Starter
  • AF-2500 engine monitor (that's right, my engine monitor is NOT on my e-bus)
  • Voltage regulator sense/light
  • Landing lights & wig-wag
  • Pitot heat
  • Strobes
  • Position lights

E-Bus:
  • Dynon
  • Autopilot
  • Audio Panel
  • Primary GPS/Comm
  • Secondary Nav/Comm
  • Transponder
  • ACU (annunciator for the IFR GPS)
  • CDI
  • Aileron trim
  • Elevator trim
  • Panel lights
  • Flaps
  • Fuel Pump
  • Cigarette lighter

All fuses.

B&C 40-amp externally regulated alternator, LR3C-14 voltage regulator/alternator controller. Alternator field is on the only circuit breaker in my plane.

I don't necessarily advocate copying this (although I haven't had so much as a blown fuse or any electrical problem in 600+ hours), but it's a data point for your file.

)_( Dan
RV-7 N714D
http://www.rvproject.com
 
dan said:
I see lots of VFR-only pilots flying VFR-only equipped aircraft...with dual alternators. I have to laugh when I see that. :)
Click to expand...
Well, I have to laugh when I see someone fly for 600+ hours without paint! :)
 
I've been following this thread with great interest since I'm currently designing the wiring for my plane. Here's where I'm at so far: The plane is an RV4 with fixed pitch 360, no lights, manual flaps, manual trim, 1 com, GRT EIS, Garmin 196 and no gyros except for a Trutrak ADI. I plan on a single battery, single alternator setup with fuses and a crowbar OV. My question is do I really want to set up an E-bus, and if so, what would be on it? I've noodled on it for awhile and think that everything on the plane would be on the E-bus so what's the point. On the other hand I know that if my battery contactor takes a dump, the alternate feed would come in handy. Thoughts??

Steve Zicree
RV4
 
Alternate feed is a good idea

I've seen some planes that don't necessarily have an e-bus (for the sake of "essentials" or "endurance") but they do have an alternate feed to the main bus, in case the contactor takes a crap.

For a VFR-day setup (you said no lights, so that's what I'm assuming), you could wire an alternate feed circuit from a fuse on the battery bus, through an SPST switch, to the main bus.

Check out figure Z-11: http://www.aeroelectric.com/articles/Rev11/AppZ_R11C.pdf

)_( Dan
RV-7 N714D
http://www.rvproject.com
 
szicree said:
I've been following this thread with great interest since I'm currently designing the wiring for my plane. Here's where I'm at so far: The plane is an RV4 with fixed pitch 360, no lights, manual flaps, manual trim, 1 com, GRT EIS, Garmin 196 and no gyros except for a Trutrak ADI. I plan on a single battery, single alternator setup with fuses and a crowbar OV. My question is do I really want to set up an E-bus, and if so, what would be on it? I've noodled on it for awhile and think that everything on the plane would be on the E-bus so what's the point. On the other hand I know that if my battery contactor takes a dump, the alternate feed would come in handy. Thoughts??

Steve Zicree
RV4
Click to expand...

Steve,

Since you are building a Day VFR ship with standard Mags, you don't need anything. Remember, the engine will continue to run w/o your electrical system. You will still be able to get on the ground w/o any problem. If you want, keep a hand held Nav/com in the -4 w/ a rubber ducky antenna to communicate with ATC, if you need. Heck, the battery in the 196 should last you until you get on the ground, so you really shouldn't even need the nav side of the hand held.

I flew my old no electric's T-Craft all over the East coast w/ nothing but a whiskey compass and a hand held com. Never used the nave feature, never needed it.
 
recommendation for Steve

You may have already had this in your plan, but if I were doing your setup I think that I would use the 8 Amp vacumn pad altinator from B&C. This eliminates the standard alt and belt and weights less. Does cost a little more though.

Kent
 
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