Garmin G300 for Cessna SkyCatcher User manual

190-00921-01 March, 2009 Revision A
G300
Installation Manual

Page A G300 Installation Manual
Revision A 190-00921-01
© Copyright 2009
Garmin Ltd. or its subsidiaries
All Rights Reserved
Except as expressly provided herein, no part of this manual may be reproduced, copied, transmitted,
disseminated, downloaded or stored in any storage medium, for any purpose without the express prior
written consent of Garmin. Garmin hereby grants permission to download a single copy of this manual
and of any revision to this manual onto a hard drive or other electronic storage medium to be viewed and
to print one copy of this manual or of any revision hereto, provided that such electronic or printed copy of
this manual or revision must contain the complete text of this copyright notice and provided further that
any unauthorized commercial distribution of this manual or any revision hereto is strictly prohibited.
Garmin International, Inc.
1200 E. 151st Street
Olathe, KS 66062 USA
Telephone: [phone]
Aviation Dealer Technical Support Line (Toll Free): [phone]
www.garmin.com
Garmin (Europe) Ltd
Liberty House
Bulls Copse Road
Hounsdown Business Park
Southampton, SO40 9RB, UK
Telephone: [phone]
RECORD OF REVISIONS
Revision Revision
Date Description
A 03/02/09 Initial Release

G300 Installation Manual – Table of Contents Page i
190-00921-01 Revision A
WARNING
This product, its packaging, and its components contain chemicals known to the State of
California to cause cancer, birth defects, or reproductive harm. This Notice is being
provided in accordance with California's Proposition 65. If you have any questions or
would like additional information, please refer to our web site at
www.garmin.com/prop65.
NOTE
Unless otherwise noted all installation guidance, requirements, and instructions apply to
both the one-display and two-display G300 system.
NOTE
References to the GDU 37X throughout this manual apply equally to the GDU 370 and
GDU 375 except where specifically noted.
INFORMATION SUBJECT TO EXPORT CONTROL LAWS
This document may contain information which is subject to the Export Administration
Regulations (“EAR”) issued by the United States Department of Commerce (15 CFR,
Chapter VII Subchapter C) and which may not be exported, released or disclosed to
foreign nationals inside or outside the United States without first obtaining an export
license. The preceding statement is required to be included on any and all reproductions
in whole or in part of this manual.
DOCUMENT PAGINATION
Section Page Range
Table of Contents i – viii
Section 1 1-1 – 1-8
Section 2 2-1 – 2-4
Section 3 3-1 – 3-6
Section 4 4-1 – 4-8
Section 5 5-1 – 5-4
Section 6 6-1 – 6-4
Section 7 7-1 – 7-2
Section 8 8-1 – 8-10
Section 9 9-1 – 9-26
Section 10 10-1 – 10-12
Section 11 11-1 – 11-2
Appendix A A-1 – A-16
Appendix B B-1 – B-16

Page ii G300 Installation Manual – Table of Contents
Revision A 190-00921-01
TABLE OF CONTENTS
PARAGRAPH PAGE
1 G300 Installation Overview.............................................................................................................1-1
1.1 Unpacking Unit................................................................................................................................1-1
1.2 Introduction......................................................................................................................................1-1
1.3 System Overview.............................................................................................................................1-2
1.4 General G300 LRU Specifications...................................................................................................1-3
1.5 Mounting..........................................................................................................................................1-4
1.6 Wiring/Cabling Considerations........................................................................................................1-5
1.7 Antenna Considerations ...................................................................................................................1-8
2 GDU 37X.........................................................................................................................................2-1
2.1 Equipment Description.....................................................................................................................2-1
2.2 Electrical Specifications...................................................................................................................2-2
2.3 Environmental Specifications ..........................................................................................................2-3
2.4 Installation Requirements.................................................................................................................2-3
2.5 Installation Considerations...............................................................................................................2-4
2.6 Mounting Requirements...................................................................................................................2-4
2.7 Unit Installation................................................................................................................................2-4
2.8 Continued Airworthiness .................................................................................................................2-4
3 GMU 44 ...........................................................................................................................................3-1
3.1 Equipment Description.....................................................................................................................3-1
3.2 Electrical Specifications...................................................................................................................3-1
3.3 Environmental Specifications ..........................................................................................................3-2
3.4 Installation Requirements.................................................................................................................3-2
3.5 Installation Considerations...............................................................................................................3-2
3.6 GSU 73/GMU 44 Interconnect Harness Fabrication Instructions....................................................3-5
3.7 Mounting Instructions......................................................................................................................3-6
3.8 Continued Airworthiness .................................................................................................................3-6
4 GSU 73.............................................................................................................................................4-1
4.1 Equipment Description.....................................................................................................................4-1
4.2 Electrical Specifications...................................................................................................................4-2
4.3 Environmental Specifications ..........................................................................................................4-3
4.4 Installation Requirements.................................................................................................................4-3
4.5 Installation Considerations...............................................................................................................4-4
4.6 Mounting Requirements...................................................................................................................4-6
4.7 Unit Installation................................................................................................................................4-7
4.8 Continued Airworthiness .................................................................................................................4-7

G300 Installation Manual – Table of Contents Page iii
190-00921-01 Revision A
5 GTP 59.............................................................................................................................................5-1
5.1 Equipment Description.....................................................................................................................5-1
5.2 Installation Requirements.................................................................................................................5-1
5.3 Installation Considerations...............................................................................................................5-2
5.4 Unit Installation................................................................................................................................5-4
5.5 Continued Airworthiness .................................................................................................................5-4
6 Antennas...........................................................................................................................................6-1
6.1 Antenna Mounting Location............................................................................................................6-1
6.2 Antenna Doubler/Backing Plate.......................................................................................................6-3
6.3 Antenna Grounding Plane................................................................................................................6-3
6.4 Antenna Grounding..........................................................................................................................6-3
7 Non-G300 LRU Interfaces...............................................................................................................7-1
7.1 SL40.................................................................................................................................................7-1
7.2 GTX 327 ..........................................................................................................................................7-2
8 Software, Configuration, Databases, and XM Activation................................................................8-1
8.1 Configuration Mode.........................................................................................................................8-1
8.2 Software/Audio Data Identification .................................................................................................8-1
8.3 Software Loading Procedure............................................................................................................8-3
8.4 Configuration Procedure..................................................................................................................8-6
8.5 Garmin Database Updates................................................................................................................8-7
8.6 XM Activation Instructions (GDU 375 only)..................................................................................8-9
9 Post-Installation Checkout and Calibration Procedures...................................................................9-1
9.1 Required Test Equipment.................................................................................................................9-2
9.2 GDU 37X Test Procedure................................................................................................................9-2
9.3 GSU 73/GMU 44 Post-Installation Checkout Procedure.................................................................9-4
10 Troubleshooting .............................................................................................................................10-1
10.1 GDU 37X.......................................................................................................................................10-1
10.2 GMU 44 .........................................................................................................................................10-2
10.3 GSU 73...........................................................................................................................................10-3
10.4 GSU 73 – Air Data Troubleshooting..............................................................................................10-7
10.5 Troubleshooting On-board the Aircraft........................................................................................10-10
10.6 GSU Page.....................................................................................................................................10-11
11 Return to Service Information........................................................................................................11-1
11.1 GDU 37X.......................................................................................................................................11-1
11.2 GSU 73...........................................................................................................................................11-1
11.3 GMU 44 .........................................................................................................................................11-2

Page iv G300 Installation Manual – Table of Contents
Revision A 190-00921-01
APPENDIX A: G300 Pinouts..................................................................................................................A-1
A.1 GDU 37X........................................................................................................................................A-1
A.2 GMU 44 ..........................................................................................................................................A-5
A.3 GSU 73............................................................................................................................................A-6
APPENDIX B: Outline & Installation Drawings.....................................................................................B-1
B.1 Outline & Installation Drawings-GDU 37X ...................................................................................B-1
B.2 Outline & Installation Drawings-GMU 44......................................................................................B-5
B.3 Outline & Installation Drawings-GSU 73.....................................................................................B-13
B.4 Outline & Installation Drawings-GTP 59 .....................................................................................B-15
LIST OF ILLUSTRATIONS
FIGURE PAGE
1-1 G300 Interconnect Summary ...........................................................................................................1-2
1-2 Coaxial Cable Installation................................................................................................................1-7
2-1 GDU 37X.........................................................................................................................................2-1
2-2 GDU 37X Mounting Accessories ....................................................................................................2-4
3-1 GMU 44 ...........................................................................................................................................3-1
4-1 GSU 73 Unit View...........................................................................................................................4-1
4-2 GSU 73 Air Hose Fitting Locations.................................................................................................4-5
4-3 GSU 73 Orientation Calibration.......................................................................................................4-6
5-1 GTP 59.............................................................................................................................................5-1
6-1 Recommended Antenna Placement..................................................................................................6-2
9-1 Softkey Positions..............................................................................................................................9-1
9-2 Aircraft Alignment.........................................................................................................................9-10
10-1 Heading Failure Indication (Full-Screen PFD)..............................................................................10-2
10-2 Attitude, Air Data, and Engine/Airframe Failure Indication..........................................................10-5
10-3 Attitude Failure Indication (PFD)..................................................................................................10-5
10-4 AHRS Align Message (PFD).........................................................................................................10-6
10-5 No Info for TAS & OAT................................................................................................................10-7
10-6 Airspeed and Altitude Failure Indications .....................................................................................10-7
10-7 Attitude, Heading, Air Data, and Engine/Airframe Failure...........................................................10-9
10-8 CONFIG GSU Page.....................................................................................................................10-11

G300 Installation Manual – Table of Contents Page v
190-00921-01 Revision A
A-1 View of J3701 Connector from Back of Unit.................................................................................A-1
A-2 View of J441 Connector Looking at Rear of Unit ..........................................................................A-5
A-3 Rear View of Connector End Plate.................................................................................................A-6
A-4 Rear Connector of J731 Viewed from Connector End of Unit.......................................................A-6
A-5 Rear Connector of J732 Viewed from Connector End of Unit.......................................................A-8
B-1.1 GDU 37X Outline Drawing............................................................................................................ B-1
B-1.2 GDU 37X Panel Cutout Drawing....................................................................................................B-3
B-2.1 GMU 44 Mounting Rack ................................................................................................................B-5
B-2.2 GMU 44 Top Mounted Installation.................................................................................................B-7
B-2.3 GMU 44 Bottom Mounted Installation...........................................................................................B-9
B-2.4 GMU 44 Wiring Detail .................................................................................................................B-11
B-3.1 GSU 73 Outline Drawing..............................................................................................................B-13
B-4.1 GTP 59 O.A.T. Probe Wiring Detail.............................................................................................B-15
LIST OF TABLES
TABLE PAGE
1-1 G300 LRU Part Numbers.................................................................................................................1-3
1-2 G300 LRU Power Requirements .....................................................................................................1-3
1-3 G300 LRU Physical Specifications..................................................................................................1-3
1-4 G300 LRU Environmental Forms....................................................................................................1-4
1-5 Pin Contact and Crimp Tools Part Numbers....................................................................................1-6
2-1 GDU 37X Supply Voltages..............................................................................................................2-2
2-2 GDU 37X Power Requirements.......................................................................................................2-2
2-3 GDU 37X GPS Specifications .........................................................................................................2-2
2-4 GDU 37X Recommended Antennas ................................................................................................2-3
2-5 GDU 37X Required Accessories......................................................................................................2-3
2-6 Contents of GDU 37X Connector Kit (011-01921-00)....................................................................2-3
3-1 GMU 44 Electrical Specifications....................................................................................................3-1
3-2 GMU 44 Environmental Specifications...........................................................................................3-2
3-3 GMU 44 Part Numbers ....................................................................................................................3-2
3-4 GMU 44 Accessories .......................................................................................................................3-2
3-5 Required Distance from Magnetic Disturbances..............................................................................3-3
3-6 Parts Needed for GMU 44 Installation.............................................................................................3-5
3-7 GMU 44 Connector Kit, (011-00871-00) Contents, Reference Figure B-2.4..................................3-5

Page vi G300 Installation Manual – Table of Contents
Revision A 190-00921-01
4-1 GSU 73 Supply Specifications.........................................................................................................4-2
4-2 GSU 73 Environmental Specifications ............................................................................................4-3
4-3 GSU 73 Available Equipment..........................................................................................................4-3
4-4 Contents of P731 Connector Kit (011-01818-00)............................................................................4-3
4-5 Contents of P732 Connector Kit (011-01818-01)............................................................................4-4
5-1 GTP 59 Part Number........................................................................................................................5-1
5-2 GTP 59 Outside Air Temperature Kit..............................................................................................5-1
5-3 Parts Needed for GTP 59 Installation ..............................................................................................5-2
7-1 SL40 Required Equipment...............................................................................................................7-1
7-2 SL40 Installation Kit, w/Out Connectors (013-00121-20)...............................................................7-1
7-3 SL40 Installation Kit, D-Sub 15 Pin (013-00121-30)......................................................................7-1
7-4 SL40 Installation Kit, RF Plug (013-00121-40)...............................................................................7-1
7-5 GTX 327 Required Equipment ........................................................................................................7-2
7-6 Contents of GTX 320/327 Connector Kit (011-00651-01)..............................................................7-2
7-7 Contents of Transponder Back Plate w/Hex Kit (011-00677-01)....................................................7-2
9-1 Post-Installation Calibration Procedure Summary...........................................................................9-4
9-2 Magnetometer Interference Test Sequence Example.....................................................................9-23
10-1 GSU 73 AHRS Operating Mode Table..........................................................................................10-3
10-2 GSU 73 AHRS Pitch/Bank Limitations for Cold Start While Airborne........................................10-3

G300 Installation Manual – Table of Contents Page vii
190-00921-01 Revision A
Limited Warranty for TSO’d Products
The Garmin products GMU 44 and GTP 59 are warranted to be free from defects in materials or
workmanship for two years from the date of purchase. Within this period, Garmin will at its sole option,
repair or replace any components that fail in normal use. Such repairs or replacement will be made at no
charge to the customer for parts or labor, provided that the customer shall be responsible for any
transportation cost. This warranty does not cover failures due to abuse, misuse, accident or unauthorized
alteration or repairs.
THE WARRANTIES AND REMEDIES CONTAINED HEREIN ARE EXCLUSIVE AND IN LIEU OF
ALL OTHER WARRANTIES EXPRESS OR IMPLIED OR STATUTORY, INCLUDING ANY
LIABILITY ARISING UNDER ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR A
PARTICULAR PURPOSE, STATUTORY OR OTHERWISE. THIS WARRANTY GIVES YOU
SPECIFIC LEGAL RIGHTS, WHICH MAY VARY FROM STATE TO STATE.
IN NO EVENT SHALL GARMIN BE LIABLE FOR ANY INCIDENTAL, SPECIAL, INDIRECT OR
CONSEQUENTIAL DAMAGES, WHETHER RESULTING FROM THE USE, MISUSE, OR
INABILITY TO USE THIS PRODUCT OR FROM DEFECTS IN THE PRODUCT. Some states do not
allow the exclusion of incidental or consequential damages, so the above limitations may not apply to
you.
Garmin retains the exclusive right to repair or replace the unit or software or offer a full refund of the
purchase price at its sole discretion. SUCH REMEDY SHALL BE YOUR SOLE AND EXCLUSIVE
REMEDY FOR ANY BREACH OF WARRANTY.
To obtain warranty service, contact your local Garmin Authorized Service Center. For assistance in
locating a Service Center near you, call Garmin Customer Service at one of the numbers shown below.
Products sold through online auctions are not eligible for rebates or other special offers from Garmin.
Online auction confirmations are not accepted for warranty verification. To obtain warranty service, an
original or copy of the sales receipt from the original retailer is required. Garmin will not replace missing
components from any package purchased through an online auction.
Garmin International, Inc. Garmin (Europe) Ltd.
1200 East 151st Street Liberty House, Bulls Copse Road
Olathe, Kansas 66062, U.S.A. Hounsdown Business Park
Phone: [phone] Romsey, SO40 9RB, U.K.
FAX: [phone] Phone: +44/ (0) 870.8501241
Phone: +44/ (0) 870.8501251

Page viii G300 Installation Manual – Table of Contents
Revision A 190-00921-01
Limited Warranty for Non-TSO’d Products
The Garmin products GSU 73 and GDU 37X are warranted to be free from defects in materials or
workmanship for one year from the date of purchase. Within this period, Garmin will at its sole option,
repair or replace any components that fail in normal use. Such repairs or replacement will be made at no
charge to the customer for parts or labor, provided that the customer shall be responsible for any
transportation cost. This warranty does not cover failures due to abuse, misuse, accident or unauthorized
alteration or repairs.
THE WARRANTIES AND REMEDIES CONTAINED HEREIN ARE EXCLUSIVE AND IN LIEU OF
ALL OTHER WARRANTIES EXPRESS OR IMPLIED OR STATUTORY, INCLUDING ANY
LIABILITY ARISING UNDER ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR A
PARTICULAR PURPOSE, STATUTORY OR OTHERWISE. THIS WARRANTY GIVES YOU
SPECIFIC LEGAL RIGHTS, WHICH MAY VARY FROM STATE TO STATE.
IN NO EVENT SHALL GARMIN BE LIABLE FOR ANY INCIDENTAL, SPECIAL, INDIRECT OR
CONSEQUENTIAL DAMAGES, WHETHER RESULTING FROM THE USE, MISUSE, OR
INABILITY TO USE THIS PRODUCT OR FROM DEFECTS IN THE PRODUCT. Some states do not
allow the exclusion of incidental or consequential damages, so the above limitations may not apply to
you.
Garmin retains the exclusive right to repair or replace the unit or software or offer a full refund of the
purchase price at its sole discretion. SUCH REMEDY SHALL BE YOUR SOLE AND EXCLUSIVE
REMEDY FOR ANY BREACH OF WARRANTY.
To obtain warranty service, contact your local Garmin Authorized Service Center. For assistance in
locating a Service Center near you, call Garmin Customer Service at one of the numbers shown below.
Products sold through online auctions are not eligible for rebates or other special offers from Garmin.
Online auction confirmations are not accepted for warranty verification. To obtain warranty service, an
original or copy of the sales receipt from the original retailer is required. Garmin will not replace missing
components from any package purchased through an online auction.
Garmin International, Inc. Garmin (Europe) Ltd.
1200 East 151st Street Liberty House, Bulls Copse Road
Olathe, Kansas 66062, U.S.A. Hounsdown Business Park
Phone: [phone] Romsey, SO40 9RB, U.K.
FAX: [phone] Phone: +44/ (0) 870.8501241
Phone: +44/ (0) 870.8501251

G300 Installation Manual – Installation Overview Page 1-1
190-00921-01 Revision A
1G300 Installation Overview
1.1 Unpacking Unit
Carefully unpack the equipment and make a visual inspection of the unit for evidence of damage incurred
during shipment. If the unit is damaged, notify the carrier and file a claim. To justify a claim, save the
original shipping container and all packing materials. Do not return the unit to Garmin until the carrier
has authorized the claim.
Retain the original shipping containers for storage. If the original containers are not available, a separate
cardboard container should be prepared that is large enough to accommodate sufficient packing material
to prevent movement.
1.2 Introduction
This manual provides an overview of the G300 and its mechanical and electrical installation aspects.
NOTE
The Garmin G300 is not a TSO-certified product and has received no
FAA approval or endorsement.
The following outline describes the organization of this manual:
Section 1 This section contains a basic overview of the G300 system and interface. A Block
diagram is given to aid in the understanding of the system. This section also contains
generic information that pertains to all components of the G300 system, such as
mounting, wiring, and antenna location.
Section 2 This section describes the mechanical, electrical, and installation aspects of the
GDU 37X.
Section 3 This section describes the mechanical, electrical, and installation aspects of the
GMU 44.
Section 4 This section describes the mechanical, electrical, and installation aspects of the
GSU 73.
Section 5 This section describes the mechanical, electrical, and installation aspects of the
GTP 59.
Section 6 This section describes the mechanical, electrical, and installation aspects for the
antenna(s).
Section 7 This section describes the non-G300 LRU interfaces.
Section 8 This section contains software, configuration, database, and XM activation
information.
Section 9 This section contains post-installation checkout for the G300.
Section 10 This section contains G300 troubleshooting information.
Section 11 This section contains information for ensuring the unit is suitable to be returned to
service.
Appendix A This section contains pinout information for all G300 LRU’s.
Appendix B This section contains outline and installation drawings for the Garmin G300 LRU’s.

Page 1-2 G300 Installation Manual –Installation Overview
Revision A 190-00921-01
1.3 System Overview
The G300 is an advanced technology avionics suite designed to integrate pilot/aircraft interaction into one
central system. The system combines primary flight instrumentation, aircraft systems instrumentation,
and navigational information, all displayed on one or two color screens. The G300 system is composed
of several sub-units or Line Replaceable Units (LRUs). LRUs have a modular design and can be installed
directly behind the instrument panel or in a separate avionics bay if desired. This design greatly eases
troubleshooting and maintenance of the G300 system. A failure or problem can be isolated to a particular
LRU, which can be replaced quickly and easily. Each LRU has a particular function, or set of functions,
that contributes to the system’s operation. For additional information on LRU functions, see the
applicable section of this manual.
1.3.1 System Architecture
Figure 1-1 illustrates the communication paths that are in place in a typical G300 installation.
GSU 73
GDU 370
(PFD)
GMU 44
GTP 59 GTX 327
SL
40
RS-232
CAN
RS-232
RS-485
Pitot
Static
(not included in
the G300 system)
G
OPTIONAL
DU 375
(MFD)
(not included in
the G300 system)
Figure 1-1. G300 Interconnect Summary

G300 Installation Manual – Installation Overview Page 1-3
190-00921-01 Revision A
1.4 General G300 LRU Specifications
1.4.1 Garmin LRU Part Numbers
Table 1-1. G300 LRU Part Numbers
LRU Assembly Part
Number
Unit Only Part
Number
GDU 370 011-01747-10 010-00667-10
GDU 375 011-01747-30 010-00667-30
GMU 44 011-00870-00 010-00296-00
GSU 73 011-01817-00 010-00691-00
1.4.2 Power Specifications
All LRUs are capable of operating at either 14 or 28 VDC. See the individual LRU specific
Environmental Forms (Table 1-4) for details on surge ratings and minimum/maximum operating voltages.
See Table 1-2 for current draw specifications.
Table 1-2. G300 LRU Power Requirements
LRU Supply Voltage Current Draw
GDU 37X 9-29 Vdc 1.07 Amp @ 14Vdc
0.54 Amp @ 28Vdc
GMU 44 12Vdc (from GSU 73) Inc. in GSU Current Draw
GSU 73 9-29 Vdc 1.75 Amp @ 14Vdc (Max)
0.80 Amp @ 28Vdc (Max)
1.4.3 Physical Specifications
All width, height, and depth measurements are taken with unit rack (if applicable) and connectors.
Table 1-3. G300 LRU Physical Specifications
LRU Width Height
Depth
(GMU 44
Diameter,
including
flange*)
Unit Weight
Unit Weight
w/Nutplate
& Connector
Weight
GDU 370 6.04 inches
(153.4 mm)
7.83 inches
(198.8 mm)
3.41 inches
(86.7 mm)
1.6 lbs
(0.713 kg)
1.8 lbs
(0.803 kg)
GDU 375 6.04 inches
(153.4 mm)
7.83 inches
(198.8 mm)
3.41 inches
(86.7 mm)
1.7 lbs
(0.753 kg)
1.9 lbs
(0.843 kg)
GMU 44 N/A 2.10 inches
(5.33 cm)
*3.35 inches
(85.1 mm)
0.35 lbs.
(0.16 kg)
0.50 lbs.
(0.23 kg)
GSU 73 5.50 inches
(139.8 mm)
3.96 inches
(100.6 mm)
7.33 inches
(186.2 mm)
3.1 lbs
(1.41 kg)
3.5 lbs
(1.59 kg)

Page 1-4 G300 Installation Manual –Installation Overview
Revision A 190-00921-01
1.4.4 Environmental Specifications
Refer to the applicable environmental form (Table 1-4) for a complete list of environmental
characteristics.
Table 1-4. G300 LRU Environmental Forms
Document Garmin Part Number
GMU 44 Environmental Qualification Form 005-00164-31
GTP 59 Environmental Qualification Form 005-00191-97
1.4.5 Cooling Requirements
•No cooling air is required for the GDU 37X
•No cooling air is required for the GMU 44
•No cooling air is required for the GSU 73, however the GSU 73 should be mounted in a location
that provides adequate airflow to comply with the maximum outer case temperature listed in
Section 4.
NOTE
Avoid installing the G300 LRUs near heat sources. If this is not
possible, ensure that additional cooling is provided. Allow adequate
space for installation of cables and connectors. The installer will supply
and fabricate all of the cables. All wiring should be in accordance with
FAA AC 43.13-1B and AC 43.13-2A.
1.5 Mounting
Refer to Section 2 through Section 6 for specific mounting instructions for each component of the G300,
and to Appendix A for Outline & Installation Drawings.
It may be necessary to mount the GSU 73 and/or the GMU44 remotely due to spacing/accessibility
concerns, or due to weight/balance requirements.

G300 Installation Manual – Installation Overview Page 1-5
190-00921-01 Revision A
1.6 Wiring/Cabling Considerations
Use MIL-W-22759/16 (or other approved wire) AWG #24 or larger wire for all connections unless
otherwise specified. The standard pin contacts supplied in the connector kit are compatible with up to
AWG #22 wire. In cases where some installations have more than one LRU sharing a common circuit
breaker, sizing and wire gauge is based on aircraft circuit breaker layout, length of wiring, current draw
on units, and internal unit protection characteristics. Do not attempt to combine more than one unit on the
same circuit breaker unless it is specified on aircraft manufacturer approved drawings.
Ensure that routing of the wiring does not come in contact with sources of heat, RF or EMI interference.
Check that there is ample space for the cabling and mating connectors. Avoid sharp bends in cabling and
routing near aircraft control cables.
RG400 or RG142 coaxial cable with 50 Ωnominal impedance and meeting applicable aviation
regulations should be used for the installation.
Check that there is ample space for the cabling and mating connectors. Avoid sharp bends in cabling and
routing near aircraft control cables. Cabling for the G300 should not be routed near components or
cabling which are sources of electrical noise. Route the GPS antenna cable as far as possible away from
all COM transceivers and antenna cables.
1.6.1 Wiring Harness Installation
Allow adequate space for installation of cables and connectors. The installer shall supply and fabricate all
of the cables. Electrical connections are made through D subminiature connectors for the GDU 37X and
GSU 73 units, and through a round 9-pin connector for the GMU 44. Appendix A defines the electrical
characteristics of all input and output signals. Required connectors and associated hardware are supplied
with the connector kit.
CAUTION
Check wiring connections for errors before connecting any wiring
harnesses. Incorrect wiring could cause internal component damage.

Page 1-6 G300 Installation Manual –Installation Overview
Revision A 190-00921-01
Table 1-5. Pin Contact and Crimp Tools Part Numbers
LRU Contact Type
Garmin
Contact Part
Number
Recommended
Positioner
Recommended
Insertion/
Extraction Tool
Recommended
Hand Crimping
Tool
GDU 37X Socket, Mil
Crimp, Size 20 336-00094-00 M22520/2-08, Daniels K13-1
GSU 73
GTP 59
011-00979-20
(Config
module
w/EEPROM
kit)
011-00981-00
(thermocouple
kit)
Pin, Mil Crimp,
Size 22D
336-00021-00
Positronic P/N
9502-4,
ITT P/N
M22520/2-09,
Daniels P/N K42
GMU 44 Socket, Mil
Crimp, Size 20 336-00022-00 M22520/2-08, Daniels K13-1
011-00979-22
(Config
module
w/Sockets &
Jackscrew kit)
Socket, Mil
Crimp, Size 20,
26-30 AWG
336-00022-01 Positronic P/N
9502-5
M81969/1-04
for size 22D
pins and
M81969/1-02
for size 20 pins
M22520/2-01
NOTES
1. Insertion/Extraction tools from ITT Cannon are all plastic; others are plastic with metal tip.
2. Non-Garmin part numbers shown are not maintained by Garmin and consequently are subject
to change without notice.
1.6.2 Cable Location Considerations
Use cable meeting the applicable aviation regulation for the interconnect wiring. Any cable meeting
specifications is acceptable for the installation. When routing cables, observe the following precautions:
•All cable routing should be kept as short and as direct as possible.
•Avoid sharp bends.
•Avoid routing cables near power sources (e.g., 400 Hz generators, trim motors, etc.) or near
power for fluorescent lighting.
•Analog Input wires routed too close to spark plugs, plug wires, or magnetos may result in erratic
readings.

G300 Installation Manual – Installation Overview Page 1-7
190-00921-01 Revision A
1.6.3 Cable Installation
1. Route the coaxial cable to the unit location. Secure the cable in accordance with good aviation
practice.
2. Trim the coaxial cable to the desired length and install the BNC connector (330-00087-00) per
the cabling instructions on Figure 1-2. If the connector is provided by the installer, follow the
connector manufacturer’s instructions for cable preparation.
Figure 1-2. Coaxial Cable Installation
3. Contacts for the 50, 62, and 78 pin connectors must be crimped onto the individual wires of
the aircraft wiring harness. Table 1-5 list contact part numbers (for reference) and
recommended crimp tools.
1.6.4 Backshell Assemblies
Connector kits include backshell assemblies. The backshell assembly houses the configuration module
and a thermocouple reference junction (if applicable). Garmin’s backshell connectors give the installer
the ability to quickly and easily terminate shield grounds at the backshell housing. The instructions
needed to install the Jackscrew Backshell (190-00313-11), Configuration Module (190-00313-10), and
Thermocouple (190-00313-01) can be downloaded from the Dealer portion of the Garmin website
www.garmin.com.

Page 1-8 G300 Installation Manual –Installation Overview
Revision A 190-00921-01
1.7 Antenna Considerations
1.7.1 GPS Antenna Location
Refer to Section 6 for GPS antenna location considerations.
1.7.2 Electrical Bonding
No special precautions need to be taken to provide a bonding path between the GPS antenna and the
aircraft structure.
1.7.3 VHF COM/GPS Interference
On some installation VHF COM transceivers, Emergency Locator Transmitter (ELT) antennas, and
Direction Finder (DF) receiver antennas can re-radiate through the GPS antenna. The GDU 37X does not
interfere with its own GPS receiver. However, placement of the GPS antenna relative to a COM
transceiver and COM antenna, ELT antenna, and DF receiver antenna is critical.
Use the following guidelines, in addition to others in this document, when locating the GDU 37X and its
antennas.
•GPS Antenna—Locate as far as possible from all COM antennas and all COM transceivers,
ELT antennas, and DF antennas. The GPS antenna is less susceptible to harmonic interference
if a 1.57542 GHz notch filter is installed on the COM transceiver antenna output.
•Locate the GDU 37X as far as possible from all COM antennas.
If a COM antenna is found to be the problem, a 1.57542 GHz notch filter (Garmin P/N 330-00067-00)
may be installed in the VHF COM coax, as close to the COM as possible.
If a COM is found to be radiating, the following can be done:
1. Replace or clean the VHF COM rack connector to ensure good coax ground.
2. Place grounding straps between the GDU 37X unit, VHF COM and a good ground.
3. Shield the VHF COM wiring harness.

G300 Installation Manual – GDU 37X Page 2-1
190-00921-01 Revision A
2GDU 37X
Figure 2-1. GDU 37X
2.1 Equipment Description
The GDU 37X provides a central display and user interface for the G300 Integrated Flightdeck System.
The display is mounted flush to the aircraft instrument panel using four #6 screws. A GDU 37X is
available in two models, GDU 370 and GDU 375. The GDU 370 is a Garmin Display Unit with a VFR
WAAS-GPS receiver. The GDU 375 provides these same features plus an XM receiver.
2.1.1 Flight Instrument Functions
•Display of attitude (pitch and roll), rate of turn, slip/skid, heading, airspeed, altitude, and vertical
speed information (single display installation, or on an MFD in reversionary mode)
•Display of engine and airframe instrumentation (single display installation, on a PFD in
reversionary mode, or on an MFD)
2.1.2 Navigation Functions
•Display of position and ground speed
•Display of stored navigation and map databases
•Control and display of the HSI, Selected Heading, and Selected Course (PFD or reversionary
modes only)
•Area navigation functions using the determined position/velocity and stored navigation data
•Advisory approach navigation functions and associated databases

Page 2-2 G300 Installation Manual – GDU 37X
Revision A 190-00921-01
2.1.3 Interface Summary
The GDU 37X uses CAN and RS-232 communications interfaces. The GDU 37X communicates with the
following Garmin LRUs:
•Other GDU 37X
•GSU 73 ADAHRS/Engine LRU
•SL40 Comm Transceiver
2.2 Electrical Specifications
2.2.1 Electrical Characteristics
Table 2-1. GDU 37X Supply Voltages
Characteristics Specifications
Power Requirements 14/28 VDC
2.2.2 Power Consumption
Table 2-2. GDU 37X Power Requirements
LRU 14V (Maximum) 14V (Typical) 28V (Maximum) 28V (Typical)
GDU 370 15W, 1.10 Amp 8.5W, .600 Amp 15W, 0.540 Amp 8.5W, .300 Amp
GDU 375 15W, 1.10 Amp 9.5W, .675 Amp 15W, 0.540 Amp 9.25W, .330 Amp
2.2.3 GPS Specifications
The GDU 37X uses a WAAS enabled, high-sensitivity GPS receiver that continuously tracks and uses up
to 12 satellites to compute and update it’s position.
Table 2-3. GDU 37X GPS Specifications
Characteristics Specifications
Acquisition Time a) Warm Start (position known to 10 nm, time known to 10
minutes, with valid almanac and ephemeris): Less than 5
seconds
b) Cold Start (position known to 300 nm, time known to 10
minutes, with valid almanac): Less than 45 seconds
c) AutoLocate™ (with almanac, without initial position or
time): Less than 60 seconds
Update Rate 5/second, continuous
Positional Accuracy <10 meters
Velocity Accuracy 0.05 meter/sec steady state
Antenna power supply Voltage (4.5 to 5.0), current (50 mA max)
Max Input Signal 40dB