GRT Avionics HXr User manual

HXr
Installation Manual
Revision A5
7-May-2015

HXr Installation Manual GRT Avionics
ii Revision A5
3133 Madison Ave. SE • Wyoming, MI 49548
[phone] • www.grtavionics.com
Copyright© 2013

Revision A5 iii
GRT Avionics HXr Installation Manual
FOREWORD
Congratulations on your purchase of the GRT Avionics HXr! We are pleased that you have chosen
our product to meet your flying needs.
This manual describes installation of the GRT Hxr Electronic Flight Information System using the
software version shown in the Record of Revisions. Some differences may be observed when
comparing the information in this manual to other software versions. Every effort has been made
to ensure that the information in this manual is accurate and complete. Visit the GRT website,
www.grtavionics.com, for the latest manual updates, software updates and supplemental
information concerning the operation of this and other GRT products. GRT is not responsible for
unintentional errors or omissions in the manual or their consequences.
Information in the document is subject to change without notice. GRT Avionics reserves the right
to change or improve their products and to make changes in the content of this material without
obligation to notify any person or organization of such changes or improvements.
Copyright © 2001 - 2013 GRT Avionics or its subsidiaries. All rights reserved.

HXr Installation Manual GRT Avionics
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Revision Date SW
Rev Change Description
A 1-Dec-2012 1b Initial Release
A1 19-Dec-2012 1b
Added notes about audio output- Section 3.9 and Connector B
Pinout Diagram
Replaced HXr Interconnect Diagram with high-res image
A2 09-Jan-2013 1d
Updated wiring harness packages and part numbers in packing list–
Section 1.5
Updated & clarified wiring harness Connector Pinout Diagrams for
Connector A, Connector B, and AHRS– Appendix
A3 31-Jan-2013 1d Corrected pin assignment described in Section 3.7 from B1 to A18.
Simplified trim/flap sensor wiring diagram, A14
A4 03-Apr-2013 1e
Added note about internal pull-up resistors for trim/flap sensors to
trim/flap sensor wiring diagram, A14, and Section 3.10.
Fixed backwards connector diagram on AHRS connector pinout, A11.
A5 20-Feb-2015 1f Updated to include mounting for Adaptive AHRS and digital
magnetometer..
RECORD OF REVISIONS
Section Date Revision Notes
Foreword 05-Mar-2015
1 05-Mar-2015
2 05-Mar-2015
3 05-Mar-2015
4 05-Mar-2015
5 05-Mar-2015
Appendix 20-Feb-2015 A4 HXr systems shipped after 1/08/13 include updated wiring
harnesses as described in the Appendix of Revision A2.
Installers of all units shipped prior to this date should refer to
the Horizon Cable Description documents, available from
www.grtavionics.com/documents, for Connector A, B and
AHRS pinning instructions.
LIST OF EFFECTIVE SECTIONS

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Contents
SECTION 1: GENERAL DESCRIPTION.....................................................................................................7
1.1 Introduction......................................................................................................................................7
1.2 Certification......................................................................................................................................7
1.3 System Description & Architecture................................................................................................7
1.4 Light Aircraft Avionics Primer........................................................................................................8
1.5 HXr Accessories and Packing List..................................................................................................11
SECTION 2: MECHANICAL INSTALLATION.........................................................................................14
2.1 Display Unit Installation Considerations.....................................................................................14
2.2 GADAHRS Installation....................................................................................................................14
2.2 Legacy Equipment - AHRS (Part No. AAS-) Installation............................................................17
2.3 Legacy Equipment - Magnetometer Installation (for AHRS Part No. AAS-)...........................18
2.3 GSNS (GPS) from the Adaptive AHRS...........................................................................................19
2.4 Cooling Considerations.................................................................................................................20
2.5 Pitot/Static Connections...............................................................................................................20
3.1 General Guidelines.........................................................................................................................21
3.2 Power Connections........................................................................................................................21
3.3 Ground Connections......................................................................................................................22
3.4 AHRS & OAT Wiring .....................................................................................................................22
3.4.1 Magnetometer Wiring.................................................................................................................22
3.5 Specific Equipment Interconnect Details....................................................................................23
3.6 Autopilot Source Switch................................................................................................................23
3.7 GPS Wiring from the Adaptive AHRS...........................................................................................23

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3.8 Inter-Display Communication.......................................................................................................23
3.9 Audio Tone Output........................................................................................................................23
3.10 Trim and Flap Servos and Sensors.............................................................................................24
SECTION 4: CHECK OUT & CALIBRATION.........................................................................................25
4.1 Display Unit Check Out..................................................................................................................25
4.2 AHRS/Air Data Computer Test.....................................................................................................25
4.3 Magnetometer Location Validation.............................................................................................26
4.4 Check Uncorrected Magnetic Heading........................................................................................26
4.5 Magnetometer Calibration Procedure.........................................................................................27
4.6 ARINC Checkout Procedure..........................................................................................................30
Section 5: Equipment Interconnect Details........................................................................................31
5.1 Serial Ports......................................................................................................................................31
5.2 Inter-Display Link...........................................................................................................................31
5.3 ARINC 429.......................................................................................................................................31
5.4 Analog Input...................................................................................................................................31
5.5 USB Ports........................................................................................................................................31
5.6 GRT GPS Modules..........................................................................................................................32
5.7 Specific Equipment Interconnect Details....................................................................................32

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GRT Avionics HXr Installation Manual
SECTION 1: GENERAL DESCRIPTION
1.1 Introduction
This document provides the physical, mechanical and electrical characteristics and installation
requirements for the GRT HXr EFIS.
This document, the HXr Set Up Guide and the HXr Users Guide make up the set of HXr user
documentation. These documents, along with periodic software updates and other notices, are
available at www.grtavionics.com under the Support menu.
1.2 Certification
The GRT HXr EFIS is not certified for installation in FAA Type Certificated Aircraft. It is designed
and intended for installation in aircraft licensed as Experimental or Light-Sport.
1.3 System Description & Architecture
The GRT HXr EFIS (Electronic Flight Information System) consists of one or more panel mounted
Display Units, one or more remotely mounted attitude-heading reference system (AHRS), and one
or two remotely mounted magnetometers. The Display Unit is available with either a 10.4” or 12.1”
screen. Dimensional drawings for both sizes, as well as the AHRS and magnetometer, are provided
in the Appendix of this manual. The HXr is available as either a 12 or 28-volt system; the voltage
is specified on the data tag of the display unit.
Two AHRS packages are available. The Dual AHRS package (AHRS-2) is standard with the
dual-display system, while the single AHRS (AHRS-1) is standard with a single display. The Dual
AHRS is two identical AHRS units inside one module; this assures that both AHRS units are aligned
with each other at all times. Dual AHRS is available with a single screen system as an option.
The most basic configuration for HXr is a single EFIS screen to display the primary flight instruments
of airspeed, altitude, heading, attitude, vertical speed, and rate of turn. To do this, the EFIS display
unit works with a remotely-mounted attitude-heading reference system, or AHRS, and a
magnetometer unit to determine aircraft attitude and heading information. The air data computer,
located inside the AHRS box, is connected to the aircraft pitot/static system to determine airspeed
and altitude. The GRT AHRS is unique in the industry in that it provides attitude data without gyros,
GPS or pitot/static input to compute aircraft attitude, making it more reliable than systems that
require external data.
When GPS is added to the system, GPS track and a moving map are displayed on the map page
of the primary display or the secondary display if equipped. GRT offers several different GPS
modules for the HXr. A third-party GPS unit may also be used, such as a Garmin 430/530 or Garmin
650/750. This feature is useful for adding IFR GPS approach capability to the HXr system. (IFR
approach sequencing is currently in development at GRT.) Note that the only GPS functions that

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import from a third-party GPS to the EFIS are track and position. Flight plan sequencing from such
a GPS can be imported if the GPS is wired to the EFIS through the ARINC 429 port.
When the Grand Rapids Technologies Engine Information System (EIS) unit is installed in the aircraft,
every engine parameter imaginable is able to be monitored through the EFIS system. The EIS
module senses the desired engine or environmental data, such as exhaust gas temperature, cylinder
head temperature, oil temperature/pressure, and outside air temperature, and displays it on both
the EIS screen and the EFIS screen. While the EIS displays it in numerical data only, the EFIS can
display data in graphical format, which is useful and easy to read during flight. One notable feature
is the EGT line graph, which tracks EGT data for each cylinder over time and allows easy and
instantaneous rough-engine troubleshooting. The ENG page on the EFIS is dedicated to engine
and environmental parameters. Engine data can also be displayed on a portion of the primary
flight display page, fully customizable in-flight according to the pilot’s taste and situation.
GRT strives to maintain open compatibility with third-party equipment vendors. This allows aircraft
builders and pilots the freedom to choose whatever brands fit their mission and budget, as well
as the flexibility for easy upgrades as technology evolves. Radios, transponders, ADS-B modules,
and many other third-party units interface with the GRT HXr through RS-232 serial, ARINC 429,
RS-422, and USB ports. VOR/localizer data, traffic alerts, and in-flight weather are very common
additions that are easily displayed on the EFIS screen. The HXr features the capability to mount
the radio, transponder and engine monitor in a remote location to simplify the design of the
instrument panel. The addition of a second or third display unit doubles or triples the number of
available serial and USB ports available, allowing use of more third-party devices. The Ethernet
inter-display link between EFIS screens allows data from most devices to be shared among screens
for redundancy and convenience.
See Section 5, the Appendix of this manual, and the Support section of grtavionics.com for
information on various GRT system & third party equipment configurations.
1.4 Light Aircraft Avionics Primer
Modern flight instrumentation systems may seem intimidating, but they can be simpler to install
than their analog counterparts. This section provides some basic information for aircraft builders
new to the world of electronic flight display systems.
D-Sub Connectors
A key element to designing a glass-panel installation is the communication between different
components of the system. The internal circuits of each unit are wired to use D-sub connectors for
easy external wiring of required and optional components. The main connectors of the Horizon
system are two 25-pin D-Subs, referred to in this manual as Connectors A and B. Each pin of the
connector is wired to an internal component of the display unit circuitry. Some pins are hard wired
to required elements, such as the AHRS input. Others are designated as serial ports or other
communication ports described below.
Analog Input

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GRT Avionics HXr Installation Manual
Some pins on the GRT EFIS connectors are designated as Analog input. These inputs use variations
in voltage levels to perform simple tasks. The most common use for analog data in GRT EFIS systems
today is for position indicators such as trim, flaps, and squat switches. VOR/Localizer data can be
in analog format, but has overwhelmingly been replaced by serial data or ARINC 429 for simplicity
and better performance.
Grey Code
Grey code is an analog language used by most transponders, especially older ones, to decipher
altitude encoder information. A range of pins on older GRT EFIS systems is designated as Grey
code input. Newer transponders can use serial data instead of Grey code, which vastly simplifies
the wiring process. Because Grey code is rapidly becoming phased out in favor of serial data, the
HXr does not support it.
Serial Ports
Serial ports are user defined, meaning that the aircraft builder can choose which devices use each
port. Each serial port consists of two pins– a Transmit (OUT or Tx) and a Receive (IN or Rx)–that
exchange information between the display unit and a connected device such as a GPS, radio or
autopilot. Devices that receive and transmit information use one “whole” serial port. Some
components only require an IN or OUT. For example, the EIS connects to an IN port because it
sends information to the EFIS, but the EFIS does not respond back. The other half of the port, the
OUT, may be used for a device that only requires data FROM the EFIS, such as a transponder that
uses encoder data from the EFIS. During the display unit Setup Procedure, you will use the system
Setup Guide or Equipment Supplement to program the display unit and “tell” it which device uses
each serial port and which baud rate it requires.
Data is transported through the serial ports to make the devices work. A stream of serial data is
like a sentence, and data packets are like the words. Data packets are transmitted in a
predetermined order and frequency. This frequency is known as the baud rate. A device that
communicates at a baud rate of 9600 delivers 9600 coded data packets per second in a sequence
that the receiving device expects. The baud rate of the serial port in the EFIS must be configured
to match that of the device; otherwise, the “sentences” of data packets will be scrambled. Note
that only one baud rate may be programmed per serial port, so if two devices share a port, they
must use the same baud rate.
ARINC 429
ARINC 429 is a data transfer method designed specifically for use in aircraft avionics systems. It
was originally intended for use in airliners and other commercial aircraft where large amounts of
data are transferred. It can be more confusing for a beginner to wire than a serial port because it’s
like a four-lane highway; each data stream IN and OUT requires two wires, referred to as A and B.
ARINC 429 data rates are either 12.5 or 100 kilobits per second; therefore, each ARINC port is set
to either LOW (12 kbps) or HIGH (100 kbps) depending on the requirements of the device it runs.
An ARINC device commonly used with GRT systems is the Garmin GNS430/530 IFR-certified GPS,
which uses the ARINC connection for better performance over the old analog VOR/Localizer data..

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USB
The preferred method of data transmission for newer devices is USB. Just like the USB port on your
computer, an EFIS USB port is easy to connect and transmits large amounts of data quickly. USB
devices do not require you to program a baud rate. The HXr has two USB ports that may be used
for two USB devices, or you may attach a USB hub to run up to three devices. Some ADS-B units,
such as the Radenna Skyradar, offer USB data transmission. Software updates are also delivered
to the EFIS via USB– simply install the software update files onto a USB thumb drive from the GRT
website, then install the thumb drive to the EFIS USB port. The EFIS will upload the files when you
follow the Update instructions in the system Setup Guide. Most people choose to leave a USB
extension cable plugged into the USB port for easy software updating. Flight and engine data may
be recorded to a USB thumb drive as a “demo file” for later examination– a useful feature for
collecting flight test data.
Bluetooth
The HXr features a new method of EFIS data communication: Bluetooth wireless. With this feature,
the EFIS can communicate with an Android-based tablet or smartphone that has the GRT App. This
is particularly useful in tandem aircraft, where the back seat passenger can have their own PFD on
a kneeboard. They can even change radio frequencies and adjust flight plans without getting near
the EFIS or the rest of the instrument panel. (Note: The Android app is still in development at GRT;
the beta version will be available for free download by the end of 2012.) The Bluetooth transmitter
dongle is a tiny device about the size of a thumbnail that plugs into one of the USB ports in the
back of the display unit.
Physical Wiring
All the wires supplied with the EFIS system are 22-gauge. Many wires are included in the wiring
harness for the EFIS, and some are pre-pinned. GRT pre-connects wires that are guaranteed to be
used by the builder. The wires are different colors so they may be traced throughout the airframe
and avionics compartment. Labeling the ends of the wires is a good practice, especially in complex
installations where there may be dozens of wires.
It will take some effort to figure out exactly how long each wire must be to reach remotely-mounted
devices, but too long is always preferable to a wire that barely reaches. Always allow several inches
of extra “service loop” in your wiring installations to allow easy removal of connected components
from the mount locations and prevent wires from vibrating loose under tension.
Most wires already have connector ends on them, but some do not because each airplane requires
different lengths of wire for different applications. Each EFIS comes with pin connectors that will
need to be crimped to the ends of wires after they are trimmed to length. For information on how
to crimp wires, there are some good videos on EAA’s Hints for Homebuilders website, as well as
written information in the publications listed at the end of this section.

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The pinout diagrams included in this manual are designed to give you the pre-wired pin locations
for required components, as well as the pin locations of the serial ports and optional items. NC
means “no connection,” or a pin that leads to nothing inside the EFIS. TX, or transmit, designates
a Serial OUT, and RX, or receive, designates a Serial IN connection.
The graphic interface diagrams are provided as an example of how different devices can be wired
to the EFIS display units. These diagrams offer an efficient way to use the serial ports based on
many years of experience of our techs. Of course, this is just an example, and different third-party
equipment and serial port configurations are left up to the builder and panel designer.
For More Information…
Depending on what your “mission” is, you may want a simple VFR system, or an IFR system with
many built-in redundancies. The GRT system enables customization for the whole range of
possibilities, from simple to sophisticated, depending on the builder’s desire and skill level.
While this manual covers the very basics of EFIS wiring & communication and the GRT HXr-specific
details, there are many very important safety aspects of aircraft wiring that we cannot even begin
to discuss in this manual. The techs at GRT recommend the following sources for more information
on proper aircraft avionics & electrical system design:
by Bob Nuckolls is a great place to start. This manual covers everything
from the very basics of electricity to the proper design and installation of sophisticated IFR-capable
systems.
Longtime EAA columnist Tony Bingelis’s books, the series, have long been a
staple of experimental aircraft builder knowledge. In addition to wiring considerations, Mr. Bingelis
discusses all aspects of kitplane building, from spinner to tail.
FAA Advisory Circular 43.13-2B provides the “certified” reference for safe and durable aircraft wiring
techniques, though it is a bit outdated. It is available online for free download from www.faa.gov.
All of the above publications are available at Amazon.com.
The Experimental Aircraft Association has compiled a collection of videos called Hints for
Homebuilders on its website, www.eaa.org. A quick search through these will give you valuable
hints on various wiring topics, including properly crimping D-sub/Molex connector pins.
1.5 HXr Accessories and Packing List
Your HXr system has been carefully inspected and packaged. It includes the EFIS display unit and
associated accessories. Before installing and getting started with your new system, please use the
packing list that accompanied the EFIS and the following paragraphs to ensure that no items are

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missing and that there is no visible damage. If any parts are missing or damaged, please contact
GRT Avionics or your GRT dealer immediately.
There are a number of options for remotely mounted radios, transponders, ADS-B and XM Weather
receivers that work with HXr. Because this list is constantly growing, please refer to the GRT website,
www.grtavioncs.com, for the most current details about Compatible Equipment options. Some of
them are available for purchase from GRT as part of your EFIS package.
Three- or four-display packages contain the same accessories as a Dual Display package and may
be equipped with similar options. The EFIS to EFIS wiring harness supplied will accommodate the
number of display units supplied.
Single Display Package
Qty Part Number Description
1 MFD-HXr-10.4 Multi-Function Display, HXr EFIS (optional 12.1)
1 AHRS-1 Attitude-Heading Reference System w/Magnetometer (single)
1 OAT-03 Outside Air Temperature Probe
1 CAB-HX-KIT-01 Display Unit Wiring Harness Kit
1 CAB-AHRS-01 AHRS Wiring Harness
1 USB Memory Stick
Dual Display Package
Qty Part Number Description
2 MFD-HXr-10.4 Multi-Function Display, HXr EFIS (optional 12.1)
1 AHRS-2 Attitude-Heading Reference System w/Magnetometers (dual)
1 OAT-03 Outside Air Temperature Probe
2 CAB-HX-KIT-01 Display Unit Wiring Harness Kit
2 CAB-AHRS-01 AHRS Wiring Harness
1 Inter-Display Ethernet Cable
2 USB Memory Stick

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HXr EFIS Options
Qty Part Number Description
GPS-H/E GRT External GPS Module
GPS-RAIM-H/E RAIM GPS Module
GPS-LPV TSO-C145c IFR GPS
(Varies) Engine Monitor Package (EIS)
XM-WEATHER XM Weather Receiver
USB-EXT USB Extension Cable

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SECTION 2: MECHANICAL INSTALLATION
2.1 Display Unit Installation Considerations
Mount the display unit(s) in the desired location in the instrument panel. The main consideration
in choosing a location is the ability to view the display unit and reach its controls. Since the display
is fully sunlight-readable, no consideration for shielding the display unit from sunlight is required.
Be mindful of the space behind the instrument panel as well; some aircraft with tip-up canopies,
for example, have canopy supports that may interfere with the back of the EFIS when the canopy
is closed. See the Appendix of this manual for HXr component mounting templates.
The use of nut plates behind the instrument panel greatly simplifies the task of installing and
removing the 6 screws used to retain the display unit in the panel. #6 socket cap stainless steel
screws are recommended.
These two FAA Advisory Circulars provide suggestions for positioning display units with respect to
visual field and control location: While they are intended for Part 23 (Certified) Airplanes, the
information is useful and applicable to experimental airplanes also:
ŸAC23.1311-1B Installation of Electronic Displays in Part 23 Airplanes
ŸAC 20-138A Airworthiness Approval of Global Navigation Satellite System Equipment
2.2 AHRS Installation
The Adaptive GPS/AHRS/Air data computer provides airplane with GPS navigation data, one or
two attitude-heading reference systems, and an air data computer. It accepts an input from a GPS
antenna, and an external digital magnetometer.
The AHRS has the ability to be mounted in 8 different orientations. This gives the installer more
flexibility in where it may be mounted. In addition, the GADARHS includes user settings that allow
for +/-30 degree variation in the mounting orientation, eliminating the requirement for a precision
mounting surface. These settings are made through a display unit, but are stored within the AHRS.
Selecting a Location
The location of the AHRS meet these requirements:
· The location should allow for a solid mounting, such that the GADAHRS will not vibrate.
· Must not be exposed to strong airflow from cabin heat, or cabin vent air such that it could cause
rapid changes in the internal temperature of the unit. The accuracy of the attitude data could be
reduced when its temperature is changing rapidly.
· Must allow the AHRS to be mounted in any one of the 8 mounting orientations, with a variation
from this orientation of no more than +/- 30 degrees in roll, pitch, and yaw.

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· Must not be exposed to water.
The location
· The routing of pitot/static lines to the ports on the unit.
· The GADAHRS will revert to its internal magnetometer when neither the external magnetometer
data nor GPS groound track data is available to it. While magnetic fields near the GADAHRS are
not critical, mounting the GADAHRS away from strong magnets (motors, wires that carry heavy
currents, magnetic compasses, etc.) may allow for more accurate attitude data and faster startup
in this reversionary state.
· Although there is no need to remove the AHRS for maintenance or software updates, it is desirable
to chose a location that considers the practical considerations of mounting and removing it.
Setting the AHRS Orientation
The mounting orientation of the AHRS is accessed this menu. This menu also includes the roll, pitch
being sensed by the AHRS. The settings are accessed via SET MENU > AHRS Maintenance > Set
AHRS orientation. This setting screen provides the following settings:
AHRS Orientation Lock:
After setting the orientation of the AHRS, the display unit locks access to this setting, requiring that
it be unlocked before the user can alter the AHRS orientation setting. The lock feature prevents
inadvertent altering of the selected AHRS orientation, as this could result in reversed roll and pitch
attitude displays.
To unlock the AHRS orientation, the serial number of the AHRS (located on the label of the AHRS),
must be entered into unlock code. This requires the AHRS be inspected to note its mounted
orientation. The unlock code will need to be re-entered after the display unit is turned off.
AHRS Orientation Options
This entry must be set to match the installed orientation of the GADAHRS. This setting will be
grayed out when the AHRS orientation is locked. It cannot be altered until the unlock code has
been set with the previous setting. The available mounting orientations are defined by the direction
top and connector sides of the unit, as follows:

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Orientation Settings - Adjust Roll / Adjust Pitch / Adjust Yaw
These entries allow for correcting for mounting orientation by up to 30 degrees. Adjust the roll
and pitch setting as required to make the adjustment. When the knob is pressed after making the
adjustment, the roll and pitch displayed on this page will reflect the effect of the new setting. It
is possible that some interaction between the settings may be observed if the settings are large.
Roll and pitch can be adjusted to zero the roll and pitch data displayed (assuming the airplane is
resting in a wing level/nose level position).
The yaw entry must be made by measuring the orientation of the AHRS box with respect to the
longitudinal axis (centerline) of the airplane from a top-down perspective. Note that a right entry
indicates the AHRS is mounted with its axis pointing to the right of the airplane longitudinal axis
in the direction of the nose.
CAUTION: Adjusting the roll, pitch or yaw orientation of the AHRS requires will reduce the accuracy
of the magnetometer data. A fine magnetometer calibration should be performed after these
settings are changed.
2.3 Adaptive AHRS Digital Magnetometer Installation
The digital magnetometer supplied with your adaptive AHRS includes internal accelerometers to
sense the orientation of the magnetometer automatically. This allows great flexibility in the
mounting of the magnetometer, but determining the location of the magnetometer requires
considerable care due to the magnetometer's sensitivity to magnetic disturbances generated by
the airplane.
No periodic maintenance is required for the magnetometer, although it is desirable to mount it in
a location where it is not exposed to water, and allows access to it if necessary. Keep in mind that
.
Top - Forward, Connector - Right
Top - Up, Connector - Aft
Top - Up, Connector - Forward
Top - Aft, Connector - Right
Top - Left, Connector - Aft
Top - Left, Connector – Forward
Top - Right, Connector - Aft
Top - Down, Connector – Aft

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Sharing the Magnetometer
The digital magnetometer serial data output may be shared with other GRT Avionics GADAHRS,
and with the Mini-EFIS that may also be a part of your panel. To share the data, simply tee the
serial output from the magnetometer with other devices. Only one source of power should be
provided to the magnetometer. If your panel includes a GRT Avionics Mini-EFIS with a battery
backup, we recommend using the Mini-EFIS to power the magnetometer.
Setup for the Magnetometer
Refer to the section "Validating the Magnetometer Location" to find the best location. Before
validating a magnetometer location, temporarily mount the magnetometer (such as by using
masking tape), Go to Set Menu > AHRS Maintenance > Set Magnetometer Orientation. Answer
the prompts on the screen to begin automatic orientation of the magnetometer. Upon completion,
the heading data displayed on the PFD screen should be approximately correct.
Magnetometer Mounting Requirements
There is not a designated “top” of the magnetometer, so it can be turned on its side for easier
mounting. The side of a wing tip rib is a simple place to put it. The following requirements must
be met.
· The magnetometer is marked with an arrow pointing in the direction of flight. This will position
the d-sub connector on the aft side.
· Mount it such that the centerline of the magnetometer is parallel to the centerline of the airplane
from a top view.
· The "pitch" attitude of the magnetometer should be within the range of +/- 60 degrees.
2.2 Legacy Equipment - AHRS (Part No. AAS-) Installation
The AHRS is not affected by wiring, magnetic field, heat, temperature or vibration influences.
However, good practices suggest that it should be located where these influences are minimized.
The pitot and static connections are made to the AHRS, so its location should consider this.
It is important that the AHRS is mounted so that the roll, pitch and yaw axes of the AHRS are parallel
to the roll, pitch and yaw axes of the aircraft. The precision that this is achieved influences the final
performance of the EFIS.
There is no requirement that the AHRS roll, pitch or yaw axes be parallel to those of its associated
display unit.
Be sure to mount the AHRS with the connector toward the rear of the airplane. Observe the label
on the AHRS to ensure it is oriented correctly.
2.3 Legacy Equipment - Magnetometer Installation (for AHRS Part No. AAS-)
Determining the location of the magnetometer requires considerable care because of the
magnetometer's sensitivity to magnetic disturbances generated by the airplane. No periodic

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maintenance is required for the magnetometer, although it is desirable to mount it in a location
that allows access to it if necessary. The most important consideration when mounting the
magnetometer is choosing a location in the airplane that is away from magnetic disturbances. It
is quite amazing how sensitive the magnetometer is to these disturbances, and how much error
this can cause in the magnetic heading reported by the AHRS.
Keep the magnetometer at least 12 inches away from any current carrying wires (such as navigation
or landing light wires), and more than 18 inches from ferrous metal, such as the steel mass balance
tube that is typically used in the leading edge of ailerons. Use non ferrous hardware for mounting
the magnetometer. Keep the magnetometer as far as possible from transmitting antennas
(transponder and especially comm. radio) and their coaxial cables.
You can test your proposed magnetometer location prior to mounting the magnetometer itself by
placing an ordinary compass at the spot. Then:
1. Turn on and off any electrical equipment whose wiring passes within 2 feet of the magnetometer.
2. Move the flight controls from limit to limit.
3. If the magnetometer is located within 2 feet of retractable landing gear, operate the landing
gear.
4. Operate the comm. radio (transmit) and transponder (IDENT).
Observe the compass while doing each of the above. The goal is no movement, or compass
movement of less than 5 degrees. If you observe greater movement, try another location. After
the installation and wiring of the magnetometer and display unit(s) is complete, a more sensitive
check for magnetic disturbances will be conducted.
Each magnetometer and its associated AHRS work together. For this reason, they must be oriented
in the same directions, that is, the pitch, roll and yaw axes of the magnetometer and the AHRS
need to be parallel. A standard level can be used to orient the magnetometer and AHRS such that
they are equal in roll, and in pitch. For yaw, the orientation of these devices should be parallel to
the fuselage centerline. In cases where the magnetometer is mounted in the wing, it may be possible
to orient the magnetometer parallel to a wing rib, if these ribs are oriented in the wing such that
they are parallel to the fuselage centerline. This is quite practical in airplanes such as Van’s RV’s.
Figure 2-1 shows this.
There is no requirement that the Magnetometer roll, pitch or yaw axes be parallel to those of its
associated display unit.
Be sure to mount the magnetometer with the connector toward the rear of the airplane. Observe
the label on the magnetometer to ensure it is oriented correctly.

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2.3 GSNS (GPS) from the Adaptive AHRS
The GADAHRS can include an optional GPS receiver, or more accurately, a satellite navigation
receiver. This receiver can be configured to receive multiple constellations of navigation data, such
as the data from the US GPS system, the Russian Glonass, as well as Japanese and European systems
that are being developed.
Configuring the Serial Port for GPS Data Input
The GPS data provided by the GADAHRS is transmitted via its serial data output. The serial input
used to receive this data must be configured for GPS NMEA0183, 9600 baud.
The output from this GPS may be shared with all GRT EFIS display units as desired, as well as at
least two other devices, such as an ELT, transponder, etc. If these other devices impart too much
load on the serial output, the signal level will be reduced and some or all of these device will receive
no data.
Configuring the Serial Port for data to the GPS
An optional serial output from the display unit, to the GPS may also be made. If this connection is
not made, the GSNS will default to using all satellite constellations (not just the American GPS
system), and will be set to 1 position update per second. By making this connection, the satellites
used can be limited to the American GPS system only. We recommend allowing all satellite types,
Fig 2-1. AHRS to Mag Orientation
(Applies to Legacy AHRS (Does not apply to adaptive AHRS).

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and our EFIS is equally happy with once per second update rates as it is with five per second, so
the default settings are acceptable.
To configure the GPS, set the serial output to 9600 baud, and use the "GPS NMEA Configuration"
serial output selection.
2.4 Cooling Considerations
The GRT Horizon HXr EFIS does not require external cooling. However, as with all electronic
equipment, lower operating temperatures extend equipment life. Units in an avionics stack heat
each other through radiation, convection and sometimes by direct conduction. Even a stand-
alone unit operates at a higher temperature in still air than in moving air. The Horizon HXr contains
an internal cooling fan. Be sure that there is adequate air available so that it can cool the display
unit. A few openings in the glare shield are usually more than adequate to allow natural air flow.
If external forced air is used, be certain that the cooling air does not contain water – a problem
often encountered when using external air.
2.5 Pitot/Static Connections
The AHRS contains the Air Data Computer. The ADC requires connection to the aircraft pitot static
system. Connections on the AHRS unit take a 1/8 – 27 NPT male fitting. Connections and the entire
pitot static system must be leak tight. Refer to AC 43.13.1B for approved methods to achieve this.