VP-X Emergency buss
 

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?

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

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.