[Veetail88]

I'm closing in on my final panel design for my RV-8.



My questions are mainly about fuse/breaker issues and other switch questions.

1. I'm wiring the plane for dual alternators per Nukoll's book with a single battery. I'll have a main buss, an e-buss and a battery buss. I'm trying to build in a reasonable amount of redundancy for the moment as I'm not instrument rated yet and don't exactly know how I'll end up using the plane. I do want to be able to get through a layer regularly and get home to my own airport if the weather is a little scuzzy, but I'm not planning on any 400 miles in the soup legs. There's room left for another comm and a dynon D6 if I want to get the rest of the way later. I'll be utilizing the plug in type fuses that will be installed on the backside of the access doors I'm building into the baggage compartment bulkhead, so they're not accessible in flight. I've noticed that quite a lot of you also end up incorporating some resettable type fuses inside the cockpit for some items. Which functions would you use a resettable type fuse for and why?

2. Obviously, some protection for the "Main" and "Boost Pump" switches is in order (Boost pump switch will be located on the gear tower in front of the throttle quadrant), but do I need any for the remaining switches? Do you folks find you knock these things around much during flight?

3. I'm not necessarily planning on putting in a key switch and I'm not sure why. The key switches I've seen don't really handle the dual P-mags setup that I'm running the way I want to be able to use it for testing spark and internal alternator function on preflight. A simple key switch is so easy to hotwire that I don't think it's really much of a deterrent from theft, so other than keeping some kid from climbing in and doing something stupid is there any other good reason for adding one?

4. I know that the start position for normal mags will only start the motor on the mag with the impulse coupling. Is that the same case for p-mags?
I'm planning on wiring my start button on my Infinity stick grip so that it is only enabled when the p=mag switches are in the right starting positions. I've seen a schematic for wiring normal mag switches this way, but if both P-mags are on for engine start, I'll need to add a start button enable switch. Any help?

Other than that, I would appreciate critique on general layout, ergonomics, obvious oversights, etc.

Thanks in advance for any help.

 

[Pat Hatch]

One minor point: doesn't the AF-3500 have a built-in Hobbs meter? Otherwise, very nice panel.

On #3: I agree with your assessment of a key switch, plus it's one more thing that can break, and they do break. Much easier to replace single switches! I kind of like separating out different functions--makes troubleshooting much easier.

 

[Pat Hatch]

On #1: I put CBs on the alternator field, all electric trim tabs, and the T&B if you have one. Otherwise, I used Nuckolls' fuse blocks, not accessible in flight. Obviously, if you had a runaway trim you will want to be able stop the trim servo, although in the RV I don't think full trim is an unmanageable situation. The T&B is just for maintenance on the ground to be able to turn it off. A lot depends on whether you agree with Bob's philosophy; I do.

 

[erich weaver]

Nice panel - I like it.

Two comments:
1 Why have the breaker on the e-bus feed? Do you really think you are going to fix the problem by resetting the breaker? Also keep in mind that you are only going to use the ebus alternate feed when you have some electrical problem. So now for the use of the breaker to come into into play you are assuming that you have a second problem after that, and that it can be resolved by resetting the breaker. Not likely...

2 I know you have GPS in the 430 and presumably built into the EFIS which would show up as a separate page, but have you considered a Garmin x96 mounted in an AirGizmos dock? Besides the moving map, they can display lots of other useful information, and it sure is nice to have all the good stuff all displayed at once. Just a thought.

erich

 

[Veetail88]

Pat, The Advanced panel will actually be the new Advanced Deck 4500, but you're right. I downloaded the manual for the 3500 and it does indeed have built in Hobbs type function. I should have realized that. Pretty simple function for such a piece of equipment.

Fact is, it has G meter function as well, so I removed that from the plan.

I've updated the drawing.

What is the reasoning behind you're putting a breaker on the alternator field circuits instead of just a fuse? Do you have a single alternator system? If so, I suppose I'd like to be able to try to reset it at least once. With dual alternators, I fugure I'll just run on the e-buss from the secondary alternator if the primary goes.

I hadn't thougt of a runaway trim condition. I think I'll add a switch to disble the trim functions rather than a breaker.

I'm not running a T&B. My autopilot will be my back up attitude system to begin with. If later I want more, I'll be adding a Dynon D6 or D10A.

Erich,

I think you're right about the e-buss feed. I don't think it would likely be useful either. With the multiple buss electrical system and redundant instrument functions, resetting any circuit shouldn't be necessary. I guess that's the goal of the complex electrical architecture.

Regarding the GPS, yes, I'll have GPS and NAV from the 430 but I'll also run a GPS puck for redundant positioning for the EFIS. If the EFIS goes, I still have the 430 which while the screen is small, it certainly will get me where I'm going.

As for the other goodies, I've ordered the mapping system for the AF EFIS which will do a pretty good job. Later, when I get to my IFR ticket, I'll add the XM weather module so I can overlay that on the map. Who knows, by then ADS-B might be fully implemented and I understand one of the companies selling ADS-B recievers is already compatible with the Advanced Filght Systems stuff. I think free uplinked rader weather will trump XM weather.

Amazing stuff.

Thanks for the help guys.

 

[Pat Hatch]

Pat,

What is the reasoning behind you're putting a breaker on the alternator field circuits instead of just a fuse? Do you have a single alternator system? If so, I suppose I'd like to be able to try to reset it at least once. With dual alternators, I fugure I'll just run on the e-buss from the secondary alternator if the primary goes.

I have a B & C regulator which has an overvoltage test function. Basically, when you test it, it simulates an overvoltage condition and if things are working properly, pops your field breaker. After the test, you simply re-set the breaker. But you are right, you are allowed one alternator reset! I like having the alternators on separate switches, in my case, the top position of the battery masters, OFF, BATT, ALT. If you were to have a buss fault (like a feeder fault, for instance), you would want to turn off the source of the amps, i.e., alternators and battery. This is just me, but I also like to conserve battery power, so before starting I select the BATT position and only go to ALT after starting. Keep in mind that in the ALT position the alternator field is drawing an amp or so. You don't need this when the engine is not running, especially if you're getting a clearance or have a long pre-start checklist.

A heads up on your dual alternator architecture: I have this on the RV-7, dual alternators, dual batts, using the Nuckolls schematic. Here's what happens in real life: when taxiing, the vacuum-pad-mounted alternator produces low voltage because of the low gearing in the accessory case for the vacuum pump. So, until RPMs increase, you will be getting a low-voltage warning for the secondary alternator--just a nuisance, really. The solution for me is to tie the two buses with the buss tie switch during ground operations, low voltage light goes out. I untie the busses before takeoff, that way, if you have a bus problem both alternators won't be feeding the fault, and also you isolate the bus with the problem. If, instead, you have an alternator failure, you would then want to tie the busses in flight, of course.