Building Simulated Aircraft Instrumentation
Written by Mike Powell
Published by Mike's Flight Deck Books

I have to admit, when I first heard of Mike Powell's book on building 
instruments for homebuilt flight simulators, I was VERY interested.

The fact that this book exists at all is a testament to the unique 
dedication that the home cockpit builder has.  The book was published at 
the author's expense!

This book is the first of its kind for our hobby and is a landmark text in 
its own right.  

Building Simulated Aircraft Instrumentation is a 400 page book that has 
details on building an Airspeed Indicator, Vertical Speed Indicator, Turn 
Coordinator, Attitude Indicator, VOR/GS, Gyro Compass, ADF/RMI, Altimeter 
and a dual indicating Turbine Tachometer.  Basically, everything you need 
in a homebuilt cockpit is presented here.

The book is broken up by indicating technology.  The first technology 
convered is air-core motors.  Chapter One covers what an air-core motor is 
and how they operate.  He includes information on how these motors can be 
driven by computer, which as it turns out, is very easy.

The second chapter covers how to build your own air-core motor.  The 
description of constructing the motor is clear, but there are some 
elements that aren't clear.  The website ( 
is a big help here as there are pictures of what a DIY air-core motor 
looks like as well as some info on a handy winding machine.  When you've 
got 1000 turns to a coil, a winder is a nice thing to have. :)
The end of the chapter includes a nicely formatted parts list for building 
a "typical" air-core motor.  

The first instrument you get to build with this new found air-core 
knowledge is a simple Airspeed Indicator.  

The instrument is covered in detail, including detailed drawings for the 
various parts that make up the ASI.  The design covers everything from the 
face art and lighting to the circuit used to drive it.  Of special note is 
the care taken to explain the important parts of the electronic circuit.  
You not only learn how to build the circuit, but Mike explains how it 
works so you know WHY it does what it does.  The only down side that I've 
noticed is the lack of a printed circuit board layout.  The schematics are 
clear and well drawn, but a PCB layout would be especially helpful to the 

Next up is an air-core Vertical Speed Indicator.  This instrument is 
driven by a micro-controller called a PIC.  This allows the VSI to be 
controlled via a standard serial port.  The source code for the PIC is 
inlcuded and it's a well commented listing.  He also goes into detail on 
how the PIC is used which is a nice bonus.  

One thing to remember about air-core motors is that they're an infinitely 
positionable device.  This basically means that it can be controlled to a 
very fine degree.  The action is also smoother than any geared system and 
is therefore very good for instruments where there is exactly 360 degrees 
of travel or less.  Good applications would include cylinder head 
temperature gauges, rpm indicators and the like.

In the next chapter, Servos are explained in detail.  Both how they 
operate and how to control them.  This chapter also gives a good overview 
of gears and how they're measured.

The first servo driven instrument is a typical turn and bank indicator.  
He has designed this instrument to use two servos, one for the roll needle 
and one for the slip ball.  It's a very straightforward design and follows 
the previous examples in drawing and construction quality.

Next up is an attitude indicator built from two servos.  This unit is 
representative of what you'd find in a typical Utility category private 
plane such as a Cessna 152 or Piper Cherokee.  This is a fancy way of 
saying that the roll indication has a range of +/- 90 degrees from level 
and pitch has a range of +/- 30 degrees.  This is due to the basic 
limitations of a model airplane servo.

The next servo based instrument is a nice little VOR/GS CDI instrument.  
The servos drive the localizer and glideslope needles and the TO/FROM 
course is displayed on 3 digit 7 segment LED displays.  This is another 
instrument that utilizes a PIC at its heart.  It also includes a rotary 
encoder for adjusting the course setting.

From here the book moves on to stepper motors.  What they are and how they 
work are well outlined in this chapter.  He covers how stepper motors are 
driven in a clear and concise fashion.  

The first instrument in the stepper motor line is a Gyro Compass.  In a 
real aircraft, this is instrument is actually the "display" from a vacuum 
powered or electric gyroscope.  Just like the real thing, the stepper 
motor driven instrument has a "setting" dial that allows the gyro compass 
to be set to the "wet" compass before takeoff.  The design uses a rotary 
encoder like the previous VOR/GS instrument does.  

Next on the stepper motor list is an ADF/RMI indicator.  This is unique in 
that it uses a concentric shaft system to drive the compass card and the 
indicating needle independant of each other.  This instrument has a 
moderately complex gear train that the author does quite well in 
explaining, even to a gear-n00b like myself.  This is also a PIC 
controlled instrument and like the others, full and commented source code 
is included in the book. 

The next instrument is a real peice of art.  It's a three needle 
altimeter.  It counts feet in tens of thousands, thousands and hundreds.  
The gear train complexity takes a step up with this one, but the design is 
beautiful in its simplicity.  

The last instrument in the book is a turbine tachometer that includes a 
sub-gauge used for indicating the units digit of the percentage reading.  
This gauge like the others is a real work of art in how direct and simple 
it is built.  

The remainder of the book covers interfacing and the importance of doing 
good layout for building the instruments in the book.  Also covered are 
good sources of parts for building the projects in the book.

For a first book of it's kind, I'd say it is a must have for any cockpit 
builder's library.  The construction details are universal and can be 
applied to many different instrument types.

There are a few things I'd like to see addressed though.  While 
construction details covered very well, there is little help in doing 
circuit layout.  It would greatly benefit the novice builder if PCB 
layouts could be supplied in some form.  Better yet, a place to order the 
boards, etched and unpopulated.

Another improvement would be code and drawings on CD.  Maybe these could 
be provided to "registered" users for download or emailed?

All in all, this is a great book for both novices and experienced cockpit 
builders alike.

Comments or questions?  Email me at

Gene Buckle
November 11th, 2004
Copyright 2004, All Rights Reserved