Page 10
VP-X Installation and Operating Manual
Rev. D (August 5, 2020)
3. Electrical System Basics
This manual and the accompanying documentation on the Vertical Power
web site are intended to provide enough detail to understand overall
concepts and safely wire your aircraft. Should you want more information,
additional resources can be found in a variety of books and texts, a few of
which are shown here:
• FAA Advisory Circular AC 43.13,
Acceptable Methods, Techniques,
and Practices - Aircraft Inspection and Repair
available from
• FAA Advisory Circular AC 23.1311,
Installation of Electronic Display
in Part 23 Airplanes
,
• EAA
https://www.eaa.org/Videos/Hints-for-
• AeroElectric Connection book, available from
•
https://www.eaa.org/shop/SAW/SportAir_Workshops.aspx
• Aircraft Wiring Guide, by Mark Ausman, more info at
3.1
Free Advice on Designing your Electrical System
Many builders are new to electrical wiring and find it daunting. Even
experienced electrical engineers may not be familiar with good practices
specific to aircraft wiring. With that in mind, we’ve added lots of detail
throughout this manual. Before we dig into those details, this section will help
you to think about the big picture as you design your electrical system.
When designing your electrical system, there is a temptation to copy or
do things the same way as your buddy did them when he built his plane.
Avoid that temptation. Every experimental aircraft is different and is used
in different ways. It may end up that your plane, when finished, is similar
in certain ways to your friend’s plane, but that should be because your
requirements are similar and not because you blindly copied him.
We believe the most important free advice we can offer is the following:
CLARIFY YOUR MISSION
In this age of gadgets, it is all too tempting to add just one more
enhancement, then one more again, until we lose sight of how and why we
are building an airplane in the first place. Think about the most basic things
first. What will your plane be used for? What type of weather will you be
flying in? What do the worst-case scenarios look like?
The outcome of this decision drives not only how you wire your electrical
system, but also what avionics and other equipment you put in the aircraft.
If you clarify your mission like this, determining not only what it is but just as
importantly what it isn’t, you will be ready to adopt our next bit of free advice:
COMMIT YOUR ELECTRICAL SYSTEM TO PAPER
It is surprising to us how many builders, after relying on many pages of
detailed plans for their airframes, use little more than a napkin or a single
sheet of copy paper to draw out their electrical system. Planning and
researching your design and then committing every detail of that design to
hardcopy before you buy equipment and run wires will pay huge dividends
later on.
Whether you’re comfortable with either a pencil or a keyboard, write and
draw everything down, somewhere. Use whatever tools work best for you
— paper, PowerPoint, AutoCAD, or spreadsheets. We cannot design your
electrical system for you, but we can be a valuable sounding-board for your
thoughts. We even have an on-line planning tool at
that is a big step in the forward direction. After helping many different
customers with many different designs, we’ve learned that it’s much easier to
erase than to rewire. Much cheaper too.
While you commit your design to paper, erasing and redrawing as many
times as it takes to get it right, please keep in mind our last piece of free
advice:
KEEP IT SIMPLE
As a basic rule, the more complex something is the more likely it is to break.
For some reason, while most experimental airplanes are built as dependable
but simple vehicles, their builders are enticed to attach every electrical
bell and whistle they can find in a catalog. By adding more relays, busses,
terminals, diodes, wires, and (let’s face it) toys, you are actually adding more
things that can fail and more things that make it harder to troubleshoot.
Before you delve into the details of designing your electrical system, please
consider these three bits of advice. If you do so, the end result will be an
electrical system and avionics package that meets your real needs when you
get your project in the air.
