Electrical Architecture

As I’ve mentioned previously when putting a fuel return port into my gas tanks, I plan to go full EFII (Electronic fuel injection and ignition). That means I’ll have an electrically dependent airplane and, being such, demands quite a bit of attention to the electrical architecture to have redundancy to always keep the fan turning. Fortunately, there is a guy by the name of Bob Nuckolls over at the AeroElectric Connection who has written a book outlining basic electrical principles (most of which I already know being an EE), and provides multiple different time-proven architectures having worked in the industry for many years.

Early on, I had really settled on his Z-14 architecture, which is a dual battery, dual alternator, split (redundant) bus architecture. In-depth schematics are located across 2 pages here and here for those interested. This allows one to take approx half of the load and run it on one bus independent from the other. The idea would be to have the left glass panel, #1Nav/Com, and a handful of other goodies on one bus, and have the #2 Nav/Com, the right-most glass panel etc.. on the other bus. That way you should always be able to navigate, communicate, and get on the ground even under IMC conditions. Additionally, the EFII system is redundant too in the sense that there are 2 ECU modules, 2 fuel pumps, 2 ignition coils, etc… so each of those would be powered off of their respective redundant power busses such that you always have power to at least one of the redundant pair. The 2 busses also have the ability to crossfeed, meaning that if a failure occurs which takes out one bus, it’s possible to continue to use it by having the 2nd bus feed it. That feed won’t be at the same overall capacity as you are now on a single battery and alternator, but most stuff should be able to be used after doing some non-critical load shedding.

I’m getting close to pluming in my brake and fuel lines and systems so I’ve recently started researching more details into the architecture and also the SDS EFII solution I have chosen. First off, I’ve ordered the Andair duplex fuel selector that I’ll need to both select and return  fuel from one of the tanks.

Duplex fuel selector

I’ve also placed an order for my dual fuel pump module (shown below), filters, and pressure regulator.

Dual fuel pump

One thing that I have discovered is the fact that there is only one set of injectors into each engine cylinder for the fuel injection (i.e. not redundant), so there becomes a need to be able to power those devices from either battery. I was figuring that I was going to need to diode-Or the two battery busses together in order to accomplish that. Fortunately there was some really good discussion on VAF about this very topic and various architectures for an EFII setup. The end result was a slightly modified Z14 architecture that provides just that. I am currently planning on going with this as the architecture for my plane.

basic z14 arch
Z14 Electrical Architecture with addition of Diode-OR’ed Engine Bus

Credit for the diagram goes to Dan Horton.

Ignore the alternator amperages for now. I will need to work out my exact electrical loading and size everything appropriately.

Talking to the architecture diagram, you have 2 separate batteries that provide their respective battery busses. These feeds are directly off the battery. The battery busses are then joined together via switches and diodes to form an Engine bus. One could simply put the fuel injectors on this engine bus and keep all the other redundant engine components on their respective battery busses, but the point was made that once you have to have an engine bus, you might as well put all critical engine components on it. The switches would provide a way to isolate the engine bus from either side if something really bad happened on one of the sides that it was impacting the engine bus somehow.

The upper part of the diagram shows each battery feeding a a main and aux contactor (what your master switch typically turns on) powering a main and aux bus which all of the other electrical devices will sit on. There is the cross-feed (cross tie) contactor which allows one bus to drive the other, and each bus has its own alternator.

There will be no single point of failure that can cause the engine to shut off, if something happens, the goal of the architecture is to be able to keep flying while diagnosing and planning to get on the ground as soon as practical. Another benefit of this is if there were ever smoke in the cockpit, the first reaction will be to shut off the master switches. This is still the response here. The panel will go dark, but the engine will still run.

There is still lots of work to do on specifics, but I feel like I have a solid foundation to work from.

A Trip to Maryland

After my visit to see Jim’s RV-10, I left there still thinking that I needed to see a finished RV-10 in person. I decided to reach out to Van’s East Coast Rep, Mitch Lock. Mitch is located at St. Mary’s airport (2W6) in Maryland. He has an RV-10, RV-12, and is almost finished building an RV-14. The -10 and -12 are available for demo flights. St. Mary’s is about a 2.5 hour flight in the Trinidad, so easily doable in a day, if need be.

Mitch and I made plans to meet on Oct 31st, to take a demo flight in the RV-10 (N220RV).

Jeanine and I have good friends, Gary and Mary Mascelli, that live nearby in Ocean City, MD. So we decided to see if they would be around that weekend, and visit with them while we were in the area.

We headed down to MD on Friday night after Jeanine got off of work, arriving in Ocean City right around 9pm. Gary and Mary were tracking our flight and were ready and waiting for us at the airport.

2015-11-10 21_21_25-Clipboard

Gary’s airplane was out for maintenance, and he was so gracious as to let us park in his hangar for the night.


We had a very enjoyable late dinner, which I felt terrible about having our friends have to wait so long to eat, and then spent some time catching up afterwards, and in the morning over breakfast.

Once done, we said our goodbyes, and made the quick hop (25 minutes or so) over to St. Mary’s to meet Mitch.

We talked a bunch as he pre-flighted the RV-10, and I took an opportunity to sit in both front seats and rear seats to get a good sense of the interior space.

We then taxied out and took about a 15-20 minute flight doing various maneuvers. Mitch took the opportunity to demonstrate the stability of the airplane by having me put it in a 30 degree bank and taking all hands and feet off the controls. The plane just stayed there, in that attitude, stable as could be. He commented that it would stay like that until it ran out of gas. I was relatively impressed with the plane, and it’s handling characteristics. Seems like it would be a perfectly suitable IFR platform, and a good cross country performer (160-170kts TAS) for our needs.

Some pics of the Van’s demo model:

 We then hung out with Mitch in his hangar asking questions, along with another couple who was there to see him next. It was a good Q&A session. I didn’t have a ton of questions, mostly because I feel I’ve done so much reading on the message boards, and various builders websites, that I have a pretty good idea of what to expect.

At some point we decided we should shove off and said our goodbyes. Mitch said he hoped he would have an opportunity to welcome us to the Van’s family someday soon.

We fueled up and then headed off to Concord, NC to visit with my college friend Kevin, and his wife, Becca, who had recently just moved from NH down to NC. We were already so far south, that it was only another hour and forty minute flight to get to their place. I had hesitated earlier on continuing on with this leg of the trip with the way weather was shaping up in NC for Sunday. But the forecast seemed to hold solid that the worst weather would be later in the day, and we’d be running away from it as we continued northeast bound, so I made the call to continue on.

We had a great visit to their gorgeous new home, got to meet a good part of their neighborhood as it was Halloween and the neighbors got together to party while handing out candy to the kids in the neighborhood.

 Almost as quickly as the fun started, it was Sunday morning and we needed to depart for home. The weather was a bit scuzzy, at 500 overcast, 5 miles visibility, light rain, and no wind. Weather along our route was reporting improving conditions as we ventured along, so we launched for home. As soon as the wheels came up, we entered the scuzz. Less than 1000′ of altitude later, we were through the low-level crud and making our way home between cloud layers with some light precip, and a smooth ride. This was one of those days where having an instrument rating is so worth it. We made it home nonstop, with a slight tailwind, in 4 hours.

What a great weekend filled with friends, fun, and airplanes.

A test to see if I could really do this

A fellow flying club member, and friend, is currently building an RV-12. We had got to talking RV’s at the airport one day, and he invited me over to “give it a try”. He said he had some scrap metal we could practice on.

We setup a mutually convenient time on a Sunday morning to meet at his house and get started. Instead of drilling and riveting scrap metal, he pulls out the Van’s toolbox project that he bought several years ago and never used. He looks at me and says, lets do this project!  Umm…. okay, great!

He spent a few hours with me showing me the ropes and helping out build the toolbox.


I think I was able to pick up riveting pretty quickly. Certainly some room for more practice and perfection, mostly with making sure I keep the rivet gun and bucking bar perpendicular to the rivet.

While my finished product wasn’t perfect, I certainly walked away with the impression that I could indeed do this stuff.

Thanks so much, Dave!

Some pics of his RV-12 in progress.


Fast Forward 6 years

The Trinidad has served us well over the 6 years of ownership. I have taken the plane on many trips around the eastern part of the country. They include Tampa, FL, Savannah, GA, West Virginia, Charlotte, NC, Ocean City, MD, Hamilton, OH, Various places in PA, Oshkosh, WI, Upper Peninsula of MI, and lots of places local to the New England states. I’ve probably missed a few…

As with all things in life, some things change. There have been some changes in the lives of my airplane partners to warrant them getting out of the partnership. Thus the decision to sell our bird.

This sale got me to thinking forward to what might be next for me in this aviation world. Of course, the thought to build my own plane resurfaced, and launched me into research mode again.

One of the things that I really wanted to do was to at least see an RV-10 up close, and personal. I wanted to make sure that the interior space and baggage area was sufficient for our needs. So I reached out to the local EAA chapter, which I am a member of, to see if anyone locally was building one. I was connected to a local chapter member who lives an hour away from me, so we setup a time to meet at his house to look over and talk about his project.

Jim’s RV-10 isn’t 100% complete yet. He is a little over half done working on the fuselage, specifically fitting the cabin top onto the structure. Below is a picture of the stage where Jim is at when I went to visit.


I was able to see the baggage compartment and access door, and also sit in what would be the back seat with a cushion on the frame to get a feel for what it’s like inside. Jim and I spent about an hour together talking about his experiences with the build and lots of suggestions if I do end up building. It was certainly a good thing to see the project I’m considering in progress to get a grasp on the magnitude.

Even though this was a very productive visit, I still felt like I really needed to see a finished one in person.

The Beginnings

I started thinking about building my own airplane back in late 2008/early 2009. I was part of a flying club that has decent planes to fly, but not really well suited for longer trips that I wanted to take. I started thinking of what I could do to address that issue. In looking over airplane classifieds, it seemed like the only airplanes I could afford were old, with outdated avionics. Everything newer had a very steep purchase price that just seemed way out of my reach. I quickly latched onto the idea of building one myself. I’m an Electrical Engineer by trade, and really love understanding all the intricacies of how things work and are built. I have a reasonable skill level mechanically (doing various home-improvement projects over the years), so I really was convinced that I had what it takes to make a project of such magnitude a success. I really wanted to have a 4 seat airplane, so my choices were somewhat limited. I quickly narrowed in on the Van’s RV-10 for several reasons.

  1. It is largely an aluminum airframe (minus the cabin top/doors and cowling). An entirely carbon airframe with no fiberglass experience seemed rather daunting.
  2. Relatively fast (160-170kt true airspeed) on somewhere between 9-14 gallons per hour. Dependent on how you run the engine.
  3. The large support system. There is a massive community, not to mention support from Vans themselves, when it comes to support during my build. Rest assured that if I ever were to hit a roadblock or have a question, there would be plenty of answers out there.

I did tons of research, and even started taking steps to better insulate my garage and make an attempt to provide heat out there to be able to work during the freezing cold winter months.

During my research, I found there to be many benefits to building your own airplane.

  1. Performing your own maintenance. This alone will save lots of money over the ownership of the plane. Not having to pay for overpriced mechanics that seem to only do an okay job.
  2. Brand new airframe with state-of-the-art avionics systems for a fraction of the cost of something comparable in the used market.
  3. Spreading the money over a period of time, such that one could accomplish the build debt-free.

Around that same time, a fellow club member approached me to see about my interest in buying into a plane that he already owned with some other partners that wanted to sell. Discussions ensued for several months in search of other partners. Eventually, we found enough to make it viable for everyone, and we purchased into his 1986 Socata Trinidad TB21.

That quelled any thoughts of building my own plane… at least for now….