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VP-X Emergency buss

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VP-X Emergency bus

I am starting the planning of my electrical system, currently planning on going with VP-X for the main/secondary bus.
I am planning on a very limited emergency bus directly off of the battery with fuses.
This will protect against solenoid, main bus wire short, or complete VP-X meltdown. (Very low probability, but not Zero)

The EFIS (probably AFS, possibly G3X ) will have its own backup battery. What else are others putting on the e-bus?

1. Electronic ignition (single with Mag) ? Definitely
2. Fuel pump ? I have only flown high wing planes (no electric fuel pump), assuming I?m IMC but going to land as quick as possible, is this necessary?
3. Autopilot

Anything else?
 
I've got a Dynon D10A on my e-bus. I can also switch my GNS420 and Xpdr to the e-bus if I hae a total failure of the main bus. I would not worry about powering the fuel pump from the e-bus. It atkes a good bit of current and is hardly ever actually needed.
 
Assuming IMC, radio and transponder would be nice to have on ebus. How about electric trim or flaps if you have them?
 
Assuming IMC, radio and transponder would be nice to have on ebus. How about electric trim or flaps if you have them?

I kept things pretty simple. Just my EFIS and GTN650. That's all I need to get me to the closest runway. Anything more is just a luxory.

Trim and flaps are nice to have, but you don' t need them to land.

bob
 
I kept things pretty simple. Just my EFIS and GTN650. That's all I need to get me to the closest runway. Anything more is just a luxory.

Trim and flaps are nice to have, but you don' t need them to land.

bob

That is what I was thinking, keep it simple as chance of failure is very low. Definately need the 650 as well.
 
My thoughts were if you were IMC and you lost your main buss, you would want a transponder and radio to communicate with ATC and also to transmit your location so ATC can work better with your situation. You can always turn off the radio and transponder if you needed to save electricity. I dont fly in IMC, but I still have the radio and transponder on my e-bus. Its only a few more wires. :eek::D
 
In the case of a VP-X installation, I don't recommend wiring backups for the trim or flaps because it adds quite a bit of complexity. That is because the motor requires two wires that you have to reverse polarity, and frankly you can land safely with either in their cruise position. :)
 
Emergency buss?

You may consider:

One switchable cockpit LED lamp.

Also, I would be very careful to define the name of this buss in light of how it is intended to be used. ie: Which "emergency" would bring this buss into play. I think you may want to call it "endurance" or "essential" buss, for use when the alternator fails. Or "alternate feedpath" buss for use when the VP-X is inop.

Do you have a backup alternator, ie SD-8? If so, you would want to size the continuous draw of the E-buss to be less than the capacity of the Aux alternator, thereby saving the battery to the end of the flight when it's needed the most.

My .02

Bevan
 
You may consider:

One switchable cockpit LED lamp.

Also, I would be very careful to define the name of this buss in light of how it is intended to be used. ie: Which "emergency" would bring this buss into play. I think you may want to call it "endurance" or "essential" buss, for use when the alternator fails. Or "alternate feedpath" buss for use when the VP-X is inop.

Bevan

Using your terminology I am looking for what people are putting on a "alternate feedpath" bus in case for complete VP-X meltdown.
In case of alternator failure the VP-X will handle the load shedding.

With the VP-X Pro having 2 separate busses I think the likelyhood of failure of both is low, but for the cost of a couple of fuses, and 20 ft of wire the cost/complexity is minimal for a few items.
Based on the feedback so far I think I will limit it to:
1. EFIS
2. Electronic Ignition (single with Mag)
3. GNS650
4. Transponder (probably)


Everything else is just "nice to haves", and 99.999% of the time will be covered by the VP-X.
Thanks for everyones thoughts.
 
In my instance, I'll have one P-Mag, Comm1, fuel pump and the RHS SkyView display.

If/when I install a 430/650, that'll be added as well. Autopilot, trim, transponder, external & internal lights can go. I'll have a lip light on the headset for cockpit illumination at night, and the torch in the Nav-bag.

My switch for the E-buss is labelled A'la A320, "EMER ELEC", will be a guarded, lever-latch toggle from Stein. In the normal position, power for the battery contractor passes through one side. When configured for non-normal operation, the contractor is opened, de-energizing the VP-X, and closing a small relay powering the E-buss.
 
...
Based on the feedback so far I think I will limit it to:
1. EFIS
2. Electronic Ignition (single with Mag)
3. GNS650
4. Transponder (probably)...
1. If your EFIS has a battery backup, don't put it on the E-buss.
2. If you go with a P-mag for your EI, then you don't need to put it on E-Buss. If you want some other type of EI, don't include it. That single Mag should get you home. After all, that's why you have it.
3. That would be good and maybe add a Garmin handheld because of its internal battery.
4. ATC can see you w/o a transponder. They just won't know your altitude. Besides, transponders are always transmitting, which sucks power. Put one Com radio in its place and use it sparingly.
 
1. If your EFIS has a battery backup, don't put it on the E-buss.
2. If you go with a P-mag for your EI, then you don't need to put it on E-Buss. If you want some other type of EI, don't include it. That single Mag should get you home. After all, that's why you have it.
3. That would be good and maybe add a Garmin handheld because of its internal battery.
4. ATC can see you w/o a transponder. They just won't know your altitude. Besides, transponders are always transmitting, which sucks power. Put one Com radio in its place and use it sparingly.

I'm sorta with Bill here. Many folks have a tendency to almost setup a 2nd buss full off goodies and forget than an "E-Buss" is for Emergencies! Here's the deal..to be on an Ebuss you've likely already had 2 failures (Main Alternator plus main battery). Ignition and it's architecture shouldn't be part of the Ebuss eqution and should be planned separately (no matter which brand). Most popular EFISes all have backup batteries. Transponders are vampires.

The reality is that if a failure happens within less than an hour of home you'll return home and land. If it happens after that, most RV's only have another 2 hours of fuel on board anyway....so no need to plan for 18 hours of backup capacity; if you're truly down to the Ebuss it's unlikely you'll keep toodling on your way - instead you'll likely try to land and get the problem fixed.

While the above statements aren't accurante for 100% of the people 100% of the time, they are accurate for the large majority of folks in the lower 48. The two most important things are firstly controlling the airplane and navigating, secondly is the ability to communicate, and all remaining stuff is sort of incidental to the first 2 goals (talking to someone is moot if you can't keep the airplane upright).

Autopilots can be excellent resources if you fly a lot of actual IFR and can relieve you of some stress when dealing with those situations. Given the option between putting an Autopilot or a Transponder on an Ebuss, guess which one I'd choose?!? :)

That's just my 2 cents as usual!

Cheers,
Stein
 
One other thought...

If you put in a second battery to power your E-buss, make sure it is easy to replace. Then, just like your ELT batteries, replace it every two years.
 
E-Bus planning

I am trying to configure an "E" bus. My Dynon D-1000 has it's own backup power as does the Gemini PFD. I can live without xponder, flaps, trim etc. Therefore, I think all I need is a radio. Here is a proposed drawing (crude) of my planned E-Bus wiring to use with my VP-X pro. Does anyone see a problem with this approach or have a better idea? Thanks in advance.
EBuss.jpg
 
I am wiring my GTN650 Nav and Comm power to my alternate buss. Will I need to add my PAR100EX audio panel power to get the comm audio from the 650? I think the answer is yes, but just wanted confirmation.
 
I am wiring my GTN650 Nav and Comm power to my alternate buss. Will I need to add my PAR100EX audio panel power to get the comm audio from the 650? I think the answer is yes, but just wanted confirmation.


Most audio panel's have a fail safe mode that they will revert to when powered off. Typically this routes the #1 COM to the Pilot's jacks.

However, confirm with Mark for your setup....
 
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Audio-fail Safe

Brian, thanks for the heads up. I just checked and the Garmin 240 does have a fail safe power interrupt--headset, mic and PTT all default to Com 1. So, I can remove the audio panel from my "E" bus. With the audio panel is removed, does anyone see any other issues with my "E" bus schematic?
 
Steve,

Your drawing is as specified in the VP-X installation manual as a "backup method B." The only change is that you should have a dedicated fuse for each device you are powering. The fusing should match what you have configured in the VP-X for those circuits. I'll add clarification to the install manual about this.

Of course, since you can eliminate the audio panel then, in your case, you'll only need one fuse.
 
My switch for the E-buss is labelled A'la A320, "EMER ELEC", will be a guarded, lever-latch toggle from Stein. In the normal position, power for the battery contactor passes through one side. When configured for non-normal operation, the contractor is opened, de-energizing the VP-X, and closing a small relay powering the E-buss.

While this should work, it is more complex than it needs to be. :eek: I'd suggest using backup method B or C as described in the VP-X installation manual and keep things simple.
 
I'll throw in my two cents.... If you truly are designing an aircraft to be used in frequent IMC, then a power failure of the main buss in an all electric dependent aircraft while IMC, should not be treated mildly. It should be a non-event! By that I mean that your backup buss should cover all the required instruments to continue IMC to a successful approach without cleaning your shorts. If you are going to go through the trouble of installing a second battery, a charging system for that power source, and wiring to the panel, then why not back up everything you need to continue, less transponder. Yes, you should power the audio panel in a two place aircraft, after all, there may be a very capable pilot sitting next to you that you might want to communicate with, removing your headset to yell at him while trying to communicate with approach is not the safe way to handle this situation.
IMHO, anything placed between your equipment and the battery such as a the master relay and the VPX distribution system can become the source of a failure. If the alternator fails you should have plenty of time to get down with the main buss. And yes, I have seen 2 master relays fail!
All the garmin products have a secondary power input to make it easy to back them up. Run a switched bus forward, leave it on all the time and fuse it to all your instruments (except the transponder). In an emergency, shed the power as needed manually.
The advantage of a true secondary buss, is the ability to turn on your instruments prior to engine start and get your flight plan loaded, get your weather and clearance, then start your engine with all of that still up and running.
A good example of a truly redundant system is demonstrated in the Beech G36 or the Cessna G 1000 182.
 
All the garmin products have a secondary power input to make it easy to back them up.

None of the Garmin GNS products (430W) nor any of the GTN products have backup power inputs, nor does an SL-30 or an SL-40, so don't assume all Garmin products do when planning your wiring.

--Ian Jordan
Dynon Avionics
 
Ian,
You are not totally correct. You are correct, the SL30/40 do not have secondary power pins and require a back to back diode on the primary pwr in.
The GNS400 series does have secondary power inputs. P4001, pins 15 and 72.
I did not look at the GTN installation manual, so I can't comment on whether it contains secondary power inputs. I will look and report back.
Bill
 
The GNS400 series does have secondary power inputs. P4001, pins 15 and 72.

In the GNS400 installation manual, Figure H-5, Power, Lightning, and Antenna Interconnect, Note 2 says "If the aircraft has multiple power buses, It is recommended that all GNS 430W power inputs be connected to the same power bus".
 
In the GNS400 installation manual, Figure H-5, Power, Lightning, and Antenna Interconnect, Note 2 says "If the aircraft has multiple power buses, It is recommended that all GNS 430W power inputs be connected to the same power bus".

But Note 10 is applicable to the pins that Bill mentioned.

Yes, there are three separate power supplies here and yes they should all be on the same bus.

However, on 4001 there is diode isolated power inputs, which provides redundacy for the GNS portion of the unit only. You are still SOL on the comm side.

What Steve did for Option B on the VPX is a good way to deal with this for the GNS or GTN series units.
 
I did check the Garmin pin outs, and Ian is correct, the GTN series do not have secondary power inputs. Garmin has informed me that the G3X and GNS dual power inputs are isolated only by back to back diodes. This is something that can easily be done externally. Bob is correct in that the secondary power inputs for the GNS 430 exclude the comm radio and only back up the GPS and Nav.
 
We've found that the best way to back up the Garmin certified GPS/radios with the VP-X is to use backup method B (as described in the VP-X install manual). Typically in newer certified aircraft the have one radio on the avionics bus and the other on the essential bus.

The G3X components do have dual power inputs and you can run one to the VP-X and the other input to a backup battery use use backup method C.
 
I'm resurrecting an old thread rather than restarting a new one.

I've been thinking long and hard about design of my electrical system and have read Ausman's book and the relevant sections of Knuckol's as well. Things are starting to gel.

My plane is going to have dual alternators and dual batteries. It will be fully IFR capable and will utilize the SDS system as well as the VPX PRO. The panel will be Garmin (G3X x 3, GTN 650, G5, + Garmin (audio panel,transponder,2nd Nav Comm).

Where I'm stumbling is configuring the backups of the essential buss in case of failure of the main power supply or VPX. I've studied Options B and C in the VPX install manual. It looks to me like both of these solutions are rather switch intensive in that they require an extra switch for each component that I want to back up. I would prefer to have a single switch that would provide power to all that is needed. Can this be done?
 
Randy,

Shoot me a PM and I'll share with you my wiring schematic. I'm running the same setup. Would also like to talk to you about your engine.

Tim
 
I'm resurrecting an old thread rather than restarting a new one.

I've been thinking long and hard about design of my electrical system and have read Ausman's book and the relevant sections of Knuckol's as well. Things are starting to gel.

My plane is going to have dual alternators and dual batteries. It will be fully IFR capable and will utilize the SDS system as well as the VPX PRO. The panel will be Garmin (G3X x 3, GTN 650, G5, + Garmin (audio panel,transponder,2nd Nav Comm).

Where I'm stumbling is configuring the backups of the essential buss in case of failure of the main power supply or VPX. I've studied Options B and C in the VPX install manual. It looks to me like both of these solutions are rather switch intensive in that they require an extra switch for each component that I want to back up. I would prefer to have a single switch that would provide power to all that is needed. Can this be done?
Randy,

Can I ask what you came up with? I’m going through the same thing. Did you put one switch between the battery and fuse block?
 
Randy,

Can I ask what you came up with? I?m going through the same thing. Did you put one switch between the battery and fuse block?

It's a difficult question to answer. This is because almost no two aircraft have the same schematics. Without seeing the existing schematic, there isn't enough info provide accurate advice.

On my RV-10 w/ VPX Pro, I do have two Master Bus switches/solenoids that each connect a battery to the main bus. on the EBUS I do have a fuse panel that provides power to individual devices that have a backup power input.

Since the GTN650 doesn't have this feature, I have a dedicated emergency switch that switches the power in between the two buses. The only down side is if you flip the switch in flight, it will power cycle the gps.

There are pros and cons to any solution. This is why I don't share my schematic. There are very few that have the identical requirements as me. I will help discuss requirements and the decision tree around it requirement so that individuals can generate their own unique schematic.

If you haven't already done so, create a table of every electrical device in the aircraft. Add a column to identify if it's a must have for VFR flight and another column for IFR (assume solid IMC). The another pair of columns for IFR/VFR risk mitigation. in these columns how will you mitigate the risk if that device fails. The last column is to identify the best solution to solve the risk mitigation you previously defined.

A couple people that I've walked through this process with were surprised at the outcome. Many folks jump into solutioning right away. The surprise is that some folks over designed and other under designed the solution.

Paul Dye wrote an excellent article describing this approach to determining the best way to design fault tolerance into your aircraft is needed several years ago.
 
If you don't want all the redundant switches for the critical bus items, you can use one appropriately rated switch or a switch/relay combination to power a critical bus fuse block that feeds the individual devices's backup power inputs. Yes, this is a single point of failure but only when exclusively using the critical bus..... What are the statistical odds of a failure of both the primary and backup at the same time?

For devices that do not have a built in backup power input....like the GTN series, you can basically recreate that feature external to the box by adding two back to back appropriately selected diodes to the single power input. This is essentially how many devices that have built in backup power inputs are built inside anyway.

Just be careful with the selection of the diodes. Forward voltage drop, current, and power dissipation ratings must be considered. Keep in mind that excessive forward voltage drop will increase the minimum voltage required to keep your device operating. Might be important for maximum endurance.

If you want to get fancier, there are some more advanced ways to do this with more components to minimize forward voltage drop and wasted power.
 
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E-Buss Schematic

I also have a dual batt/dual alternator setup. My system is similar to what Brantel describes. The E-buss is controlled by a single switch that can be used either to cross-tie the two (LiFePo) batteries, or activate the E-buss as a stand-alone sub system.

The objective is to power only the systems necessary to facilitate a safe landing after a major electrical failure in IMC. These are IMHO;
PFD
MFD
Primary NAV/COM
Auto Pilot

i-Rzj2Q46-XL.jpg
 
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Hi Paddy,

Thanks for posting. Just want to clarify a few things on your diagram:
1. What is the shunt connected to the VP-X? The VP-X does not have a function to read external shunt values. Shunts are typically wired to the engine monitor box.
2. What is the purpose of the backup power to the Dynon D6? It has an internal backup battery in case of main power failure.

Thanks!
 
Hi Marc,
Good catch - I'd expect nothing less from the creator of the VPX!
The shunt is actually part of the G3X system, that version of the diagram showed it connected to the VPX in error - I've fixed that. As for E-Buss power to the Dynon D6, I have a particular mission in mind. I'll be flying the airplane across the North Atlantic to Ireland this summer, so I want to preserve the availability of the backup instrument for as long as possible in the event of a total electrical failure. God forbid - if the E-Buss battery reserve were to be exhausted, I'd still have the D6 internal battery to give me something to look at until I'm within sight of land.
 
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Wow, that'll be an interesting flight and trip!

Thanks for the additional context, and exactly why I say in the book to build a plane that meets *your* needs, as those needs are likely different than someone else's. :)
 
Randy,

Can I ask what you came up with? I?m going through the same thing. Did you put one switch between the battery and fuse block?

If you PM me your email I will send you a copy of the schematic I came up with. I had a fellow RV 10 builder who is also an electrical engineer look it over and he approved.
Randy
 
Old thread, new questions

I need some advice on an EBuss I'd like to use
Have installed a VPX Sport on my plane already. Because I don't have full confidence in the thing Not going dark, I want to have 3 Essential items on a basic EBuss. My Com radio, my backup Efis (G660) and an Alternator Field. That comes to 3A + 3A + 5A = 11 Amps. Below is my crude schematic. I have one SureFly emag. I figure if the alternator charges the battery I could fly on to my destination with com and GPS.
I'd appreciate your critique.


https://photos.app.goo.gl/cKjoX8T4DJrXGrZWA
 
Ron,

IMO you are making your system less reliable by adding in extra complexity and failure points. There is guidance in the VP-X install manual about backups.

My 2c. :D
 
I need some advice on an EBuss I'd like to use
Have installed a VPX Sport on my plane already. Because I don't have full confidence in the thing Not going dark, I want to have 3 Essential items on a basic EBuss. My Com radio, my backup Efis (G660) and an Alternator Field. That comes to 3A + 3A + 5A = 11 Amps. Below is my crude schematic. I have one SureFly emag. I figure if the alternator charges the battery I could fly on to my destination with com and GPS.
I'd appreciate your critique.


https://photos.app.goo.gl/cKjoX8T4DJrXGrZWA

Can I ask why you would have electrical feeds to the e-bus via both the switched and the unswitched side of the master contactor?
 
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