Aircraft Wiring Guide

The practical guide to planning, wiring, and enjoying the electrical system in your experimental aircraft.

About The Aircraft Wiring Guide

After talking to thousands of fellow homebuilders and giving many presentations at fly-ins around the country, I realized there was a need for information to design and build the newer, more complex electrical systems. The Aircraft Wiring Guide takes that experience and condenses it into 85 pages of useful information and guidance. Filled with images, pictures, text, and drawings, this book has a wealth of practical information so you can design the electrical system that’s right for you and your mission!


If you’re building, maintaining, upgrading, or repairing an experimental-category aircraft, this book can help you uncover the mysteries of aircraft wiring.


The wiring system in small aircraft used to be fairly simple because many of the systems were mechanical or simply did not exist when compared with modern avionics. Today we have electronic stall and AOA warning systems, GPS receivers, glass cockpit displays, autopilots, backup batteries and busses, electric trim and flap motors, ADS-B receivers, multiple power plugs, powered headsets, and host of other modern electronics. Therefore, the electrical system is a much more important part of the aircraft than it used to be, and therefore it is worth your time to understand the subject matter so that your plane will operate reliably.


This book is for experimental aircraft builders who want to know how to plan and wire their aircraft. First-time builders will learn how to start thinking about and planning for the electrical system. Advanced builders can keep abreast of the latest technologies and products.


This book is designed to focus on the practical information you need to make important decisions about the architecture of your electrical system, what parts to buy, and how to wire it all together.

What's in the Book?

A look at the Table of Contents

Chapter 1. Electrical System Overview

   1.1 Installation Overview

   1.2 Electrical Power Distribution

   1.3 Primary Power

   1.4 Secondary Power

   1.5 Data Buss

Chapter 2. Wiring Basics

   2.1 Electrical System Terms

   2.2 Wire Sizes and Circuit Protection

   2.3 Conductors

   2.4 Wire Labeling & Color

   2.5 Stripping Wire

   2.6 Terminating Wires

   2.7 Connectors

   2.8 Tools

   2.9 Supplies

   2.10 How to Crimp Terminals

   2.11 Switch Nomenclature

   2.12 Circuit Protection

   2.13 Introduction To Electronic Circuit Breakers

   2.14 Diode Isolated Power Inputs

   2.15 Recommendations On Using 14 or 28 Volts

   2.16 Firewall Penetration

Chapter 3. Electrical System Planning

Chapter 4. Alternators and Voltage Regulators

   4.1 Over-voltage Protection

   4.2 Alternator Capacity

   4.3 Low-voltage Indication

   4.4 Alternator Current Sensing

   4.5 Detecting Failure Conditions

Chapter 5. Contactors

   5.1 Battery Contactor

   5.2 Starter Contactor

   5.3 Rear-mounted Batteries

Chapter 6. Buss Architecture

   6.1 Emergency Buss

   6.2 Avionics Buss

   6.3 Technically Advanced Aircraft (TAA) Buss

Chapter 7. Lighting

   7.1 Landing & Taxi Lights

   7.2 Navigation & Strobe Lights

   7.3 Instrument Panel Lights

Chapter 8. Electric Trim

Chapter 9. Electric Flaps

Chapter 10. Grounding

   10.1 Ground Loops

   10.2 Grounding Choices

   10.3 Engine Grounding

   10.4 Magneto Grounding

Chapter 11. Ground Power

Chapter 12. Common Wiring Mistakes

Chapter 13. Annual Inspection Items

Chapter 14. Thinking About Switches

   14.1 Choosing switches

   14.2 Switch layout


Wiring Diagram 1: Avionics Bus Architecture - VFR

Wiring Diagram 2: TAA Architecture - IFR, with backup alternator, power system, and EFIS

Wiring Diagram 3: Vertical Power - IFR, with backup alternator, power system, and EFIS

Wiring Diagram 4: Alternators

Wiring Diagram 5: Backup Alternator

Wiring Diagram 6: Contactor Layout & Connections

Wiring Diagram 7: Starter Switch

Wiring Diagram 8: Landing & Taxi Lights

Wiring Diagram 9: Strobe Lights

Wiring Diagram 10: Navigation Lights

Wiring Diagram 11: Instrument Panel Lights & Dimmer

Wiring Diagram 12: Electric Trim

Wiring Diagram 13: Electric Flaps

Wiring Diagram 14: Starter Annunciator

Marc Ausman




Simple, practical information for homebuilders scratching their head about aircraft electrical wiring.


ABOUT MARC He currently flies an RV-7 that he finished building in 2006. He was founder and president of Vertical Power and has served as an EAA Director since 2011. He served with the U.S. Navy as a Naval Flight Officer on board the
P3-C Orion.

How this book can help you:

PLAN Helps you think about the electrical system and what things are important and what are not. Detailed three-step plan to designing the right electrical system for your mission.

UNDERSTAND Insights into all aspects of wiring to help you make better decisions. Practical information to help you learn fast! No engineering required.

BUILD Once you build, you’ll have the confidence and knowledge to do it right. And, this book is available in both paper and digital formats, so it is easy to have with you while planning and working on the plane.

Sample Pages

Here's an excerpt from Chapter 2:

2.14 Diode Isolated Power Inputs


Many modern avionics have diode-isolated power inputs – typically a primary and a secondary power input. The diode isolation ensures that each power input is “independent” of the other power input. Current coming in from one buss cannot flow through the device and out to the other buss. The diodes shown below can be thought of as check valves that ensure current only goes in but does not come out that particular power pin. The device will automatically choose between the inputs and select the one with the highest voltage.

Contactors and Diodes

Connector and Tool Selection

Wiring Diagrams Put It All Together

"Much better [than other books] for the average builder in every way!” - Stein Bruch, SteinAir

"Having read through a draft of Marc's book, I can tell you that it clearly answers many of the basic wiring questions that the average builder (without extensive aircraft wiring experience) would have - I think it will be a great resource." - Paul F. Dye, Editor in Chief, KITPLANES Magazine"

"I just picked up my copy of your book Marc. Nice job!” - James Clark, TeamRV

"My overall impression is that this is a great buy. I don't keep too may hard copies of anything anymore since we are in the electronic age but I have to say that this gem is a keeper.” - RV-9 builder

"I found the booklet to be a well written and useful guide for homebuilders.” - Sportair Workshop instructor

"I learned more about wiring my plane reading your book than any other book I have read.” - RV9A builder

“This book is a straightforward, organized presentation.” - RV-8A builder

“Thank you for cutting to the chase in your book and delivering the information concisely and logically... Money very well spent.” - RV-7A builder

"I purchased a copy at Sun N Fun. I showed it to a friend in the campground and he went over and purchased a copy. It is extremely easy to read/understand/follow. Thank you for taking the time write it.” - RV-7 builder

"I can say that we here all agree this is something everyone should have. Very simple, concise, updated to modern methods and not too overbearing for the new builder.” - Stein Bruch, SteinAir

"Got home this morning at about 1am and spent an hour reading the first parts before my eyes gave up on me.  So far it's great, well organized and thought out and exactly what I need while I think about and try to understand the fundamentals of electrical wiring we are about to undertake on my project.” - RV-8A builder

Sources - Parts and Supplies

Below is a list of suppliers that have a large selection of electrical parts and supplies.


Aircraft Spruce

B&C Specialty Products



Below is a list of vendors mentioned in the book.


Daniels Manufacturing

Plane Power

TCW Technologies

Vertical Power


And a special thanks to Bob Nuckolls, the original AeroElectric guy!

Corrections to the printed book can be found here.

Purchase Information


The Aircraft Wiring Guide is available in two formats:

1. 8.5 x 11 inch spiral bound paper, black and white printing. Our printing partner will take your order information, print the
     book, and ship it to you worldwide.

2. iBook format viewable on Mac OS X, iPad, and iPhone.


Tax and shipping may be extra. Priced in USD below. Contact for more information.


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Copyright © Marc Ausman. All rights reserved.

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