Garmin GRS 77 User manual

190-00303-10 March, 2010 Revision L
GRS 77/GMU 44
Installation Manual

Page A GRS 77/GMU 44 Installation Manual
Revision L 190-00303-10
© Copyright 2010
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, Kansas 66062 U.S.A.
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 04/29/04 Production Release
B 08/24/04 Engineering Changes
C 04/26/05 Added –10 GRS 77 and removed EQF
D 7/26/05
Changed GRS 77 unit weight, added torque specs, and added GMU 44
note
E 2/16/06 Revised calibration procedure and updated document
F 6/8/06 Added baud rates and wing tip lights to interference test
G 4/24/08 Added -10 GMU 44 and new TSO deviations
H 4/13/09 Added -10 GMU 44 installation rack and mod status
J 08/31/09 Update to reflect Level A SW for GRS 77
K 01/26/10 Added 011-00868-20 GRS 77H unit
L 03/02/10 Added wording for multiple AHRS installations

GRS 77/GMU 44 Installation Manual Page i
190-00303-10 Revision L
CURRENT REVISION DESCRIPTION
Revision Page
Number(s) Section Number Description of Change
L 2-5 2.5.1 Added paragraph concerning installation of multiple
AHRS
DOCUMENT PAGINATION
Section Page Range
Table of Contents i – viii
Section 1 1-1 – 1-8
Section 2 2-1 – 2-8
Section 3 3-1 – 3-6
Section 4 4-1 – 4-6
Section 5 5-1 – 5-18
Appendix A A-1 – A-12
Appendix B B-1 – B-4

Page ii GRS 77/GMU 44 Installation Manual
Revision L 190-00303-10
This manual reflects the operation of system and boot block software versions listed in the following
table. Some differences in operation may be observed when comparing the information in this manual to
earlier or later software versions.
LRU Part Number System SW Version Boot Block SW Version
GRS 77, 011-00868-00 3.00 3.00
GRS 77, 011-00868-10 3.00 3.00
GRS 77H, 011-00868-20 3.50 3.00
GMU 44, 011-00870-00 2.05 2.05
GMU 44, 011-00870-10 2.05 2.05
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.
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
Throughout this document references made to GRS 77 shall equally apply to the GRS 77
and GRS 77H (011-00868-20) except where specifically noted.

GRS 77/GMU 44 Installation Manual Page iii
190-00303-10 Revision L
TABLE OF CONTENTS
PARAGRAPH PAGE
1 GENERAL DESCRIPTION..............................................................................................................1-1
1.1 Introduction........................................................................................................................................1-1
1.2 Equipment Description......................................................................................................................1-1
1.3 Interface Summary.............................................................................................................................1-2
1.4 Technical Specifications....................................................................................................................1-2
1.5 Certification.......................................................................................................................................1-4
1.6 Reference Publications ......................................................................................................................1-6
1.7 Aviation Limited Warranty................................................................................................................1-7
2 INSTALLATION OVERVIEW........................................................................................................2-1
2.1 Introduction........................................................................................................................................2-1
2.2 Installation Approval Considerations for Pressurized Aircraft..........................................................2-3
2.3 Wiring................................................................................................................................................2-4
2.4 Cooling Air........................................................................................................................................2-4
2.5 Aircraft Mounting Requirements for GRS 77/GMU 44....................................................................2-4
3 INSTALLATION PROCEDURE......................................................................................................3-1
3.1 Unpacking Unit..................................................................................................................................3-1
3.2 Electrical Connections.......................................................................................................................3-1
3.3 Backshell Assembly...........................................................................................................................3-2
3.4 GRS 77/GMU 44 Interconnect Harness Fabrication Instructions .....................................................3-3
3.5 GRS 77 and GMU 44 Mounting Instructions....................................................................................3-4
3.6 GRS 77 Rack to Unit Flatness Check................................................................................................3-4
3.7 Post Installation Inspection................................................................................................................3-5
4 SYSTEM INTERCONNECTS..........................................................................................................4-1
4.1 Pin Function List................................................................................................................................4-1
4.2 Power Function..................................................................................................................................4-3
4.3 Serial Data Electrical Characteristics.................................................................................................4-4

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PARAGRAPH PAGE
5 POST INSTALLATION CONFIGURATION AND CHECKOUT PROCEDURE.........................5-1
5.1 Function Selector Switches and Display ...........................................................................................5-1
5.2 Post-Installation Calibration Procedures............................................................................................5-1
5.3 Calibration Procedure A-1: Pitch/Roll Offset Compensation by Aircraft Leveling..........................5-4
5.4 Calibration Procedure A-2: Zero Pitch/Roll Offsets by Manual Entry..............................................5-5
5.5 Calibration Procedure B: Magnetometer Calibration ........................................................................5-7
5.6 Calibration Procedure C: Heading Offset Compensation................................................................5-10
5.7 Calibration Procedure D: Engine Run-Up Vibration Test...............................................................5-11
5.8 Calibration Procedure E: Magnetometer Interference Test .............................................................5-13
5.9 Site Evaluation of Magnetic Disturbances for Magnetometer Calibration Procedure.....................5-17
APPENDIX A OUTLINE AND INSTALLATION DRAWINGS
APPENDIX B INTERCONNECT DRAWINGS

GRS 77/GMU 44 Installation Manual Page v
190-00303-10 Revision L
LIST OF ILLUSTRATIONS
FIGURE PAGE
2-1 GRS 77 and Mounting Rack..............................................................................................................2-5
3-1 Measuring GRS 77 to Mounting Rack with Feeler Gauge................................................................3-5
4-1 Rear Connector J771..........................................................................................................................4-1
4-2 Pigtail Connector J441.......................................................................................................................4-3
5-1 Fixed-wing and Helicopter position examples ..................................................................................5-7
A-1 GRS 77 Outline Drawing With Mounting Rack...............................................................................A-1
A-2 GMU 44 Mounting Rack (Sheet 1 of 2)...........................................................................................A-3
A-2 GMU 44 Mounting Rack (Sheet 2 of 2)...........................................................................................A-5
A-3 GMU 44 Top Mounted Installation..................................................................................................A-7
A-4 GMU 44 Bottom Mounted Installation.............................................................................................A-9
A-5 GMU 44 Wiring Detail...................................................................................................................A-11
B-1 Typical GRS 77/GMU 44 Interconnect Wiring Diagram.................................................................B-1
B-2 Simplified GRS 77/GMU 44 Installation, Interconnect Wiring Diagram........................................B-3
LIST OF TABLES
TABLE PAGE
2-1 Required Distance from Magnetic Disturbances...............................................................................2-6
3-1 Pin Contact Part Numbers..................................................................................................................3-1
3-2 Recommended Crimp Tools..............................................................................................................3-1
3-3 Parts Needed for GMU 44 Installation ..............................................................................................3-3
3-4 GMU 44 Connector Kit 011-00871-00 Contents ..............................................................................3-3
4-1 P771 Pin Assignments.......................................................................................................................4-1
4-2 P441 Pin Assignments.......................................................................................................................4-3
4-3. Aircraft Power Pin Assignments, P771 and P441 .............................................................................4-3
4-4 RS-232 Pin Assignments, P771 and P441.........................................................................................4-4
4-5 RS-485 Pin Assignments, P771 and P441.........................................................................................4-4
4-6 ARINC 429 Pin Assignments, P771..................................................................................................4-5
4-7 Configuration Module Connections, P771 ........................................................................................4-5
4-8 AHRS System ID Program Pins, P771..............................................................................................4-6
4-9 P771 Strapping to Achieve Desired System ID.................................................................................4-6
5-1 Post-Installation Calibration Procedure Summary.............................................................................5-2
5-2 Fixed-wing Magnetometer Interference Test Sequence Example...................................................5-14
5-3 Helicopter Magnetometer Interference Test Sequence Example.....................................................5-15

Page vi GRS 77/GMU 44 Installation Manual
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GRS 77/GMU 44 HARDWARE MOD LEVEL HISTORY
The following table identifies hardware modification (Mod) Levels for the GRS 77 AHRS and GMU 44
Magnetometer. Mod Levels are listed with the associated service bulletin number, service bulletin date,
and the purpose of the modification. The table is current at the time of publication of this manual (see
date on front cover) and is subject to change without notice. Authorized Garmin Sales and Service
Centers are encouraged to access the most up-to-date bulletin and advisory information on the Garmin
Dealer Resource web site at www.garmin.com using their Garmin-provided user name and password.
GRS 77 P/N 011-00868-00 HARDWARE MOD LEVEL HISTORY
MOD
LEVEL
SERVICE
BULLETIN
NUMBER
SERVICE
BULLETIN
DATE PURPOSE OF MODIFICATION
1 N/A N/A
This modification improves the reliability of certain
GRS 77 LRUs.
2 N/A N/A
Improves circuit reliability and robustness with the use
of improved circuit components.
3 N/A N/A Improves vibration immunity.
GRS 77 P/N 011-00868-10 HARDWARE MOD LEVEL HISTORY
MOD
LEVEL
SERVICE
BULLETIN
NUMBER
SERVICE
BULLETIN
DATE PURPOSE OF MODIFICATION
1 0735 9/7/07
This modification improves the reliability of certain
GRS 77 LRUs.
2 N/A N/A
Improves circuit reliability and robustness with the use
of improved circuit components.
3 N/A N/A Improves vibration immunity.
GRS 77H P/N 011-00868-20 HARDWARE MOD LEVEL HISTORY
MOD
LEVEL
SERVICE
BULLETIN
NUMBER
SERVICE
BULLETIN
DATE PURPOSE OF MODIFICATION

GRS 77/GMU 44 Installation Manual Page vii
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GMU 44 P/N 011-00870-00 HARDWARE MOD LEVEL HISTORY
MOD
LEVEL
SERVICE
BULLETIN
NUMBER
SERVICE
BULLETIN
DATE PURPOSE OF MODIFICATION
1 N/A N/A
This modification improves the reliability of certain
GMU 44 LRUs.
GMU 44 P/N 011-00870-10 HARDWARE MOD LEVEL HISTORY
MOD
LEVEL
SERVICE
BULLETIN
NUMBER
SERVICE
BULLETIN
DATE PURPOSE OF MODIFICATION

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