Collins AHRS System

installation manual AHS-1000( ) Attitude Heading
System
installation manual
© Copyright 2006 Rockwell Collins, Inc. All rights reserved.
Rockwell Collins, Inc.
(523-0806057)
May 1, 2006
TO: HOLDERS OF ROCKWELL COLLINS® AHS-1000( ) ATTITUDE HEADING SYSTEM

INSTALLATION MANUAL (CPN 523-0806057)
REVISION NO 2, DATED MAY 1/06
HIGHLIGHTS
The attached manual completely replaces the existing installation manual. Pages that have been
revised are indicated below with the highlights of the change. All revisions are identified with black
bars in the margins of the page.
PAGE NUMBER DESCRIPTION OF REVISION AND SERVICE EFFECTIVITY

REASON FOR CHANGE BULLETIN
List of Effective Revised to reflect this revision. All
Pages A/(B Blank)
1-1 Revised ECU-3000 part numbers in table 1-1. All
1-5 Added equipment specification for rear All
connector pin P1-96.
1-7 Added equipment specifications for rear All
connector pins P1-75, 85, and 97.
1-11 Revised table 1-3 performance All
characteristics.
1-17/1-18 Revised figure 1-2 for ECU-3000 External All
Compensation Units Part Number Matrix
2-10, 2-11 Revised figures 2-3 and 2-4 mating connector All
pin assignments for pins 96 and 97.
4-6, 4-7 Revised figures 4-3 and 4-4: added Heading All
Sync Command (Discrete Control In block)
and Heading Sync Error function (Analog
Outputs block).
TECHNICAL OPERATIONS
1/2
AHS-1000( ) Attitude Heading
System
installation manual
Printed in the United States of America Rockwell Collins, Inc.

© Copyright 2006 Rockwell Collins, Inc. All rights reserved. Cedar Rapids, Iowa 52498
523-0806057-201116
1st Edition, Feb 04/2003
(AHS-1000_IM_MAY_1/2006) 2nd Revision, May 1/06
T-1
ROCKWELL COLLINS
INSTALLATION MANUAL
EXPORT CONTROL LAWS
The technical data in this document (or file) is controlled for export under the Export Administration
Regulations (EAR), 15 CFR Parts 730-774. Violations of these laws may be subject to fines and
penalties under the Export Administration Act.
PROPRIETARY NOTICE
NOTICE: FREEDOM OF INFORMATION ACT (5 USC 552) AND DISCLOSURE OF

CONFIDENTIAL INFORMATION GENERALLY (18 USC 1905)
This document and the information disclosed herein are proprietary data of Rockwell Collins, Inc.
Neither this document nor the information contained herein shall be used, reproduced, or disclosed
to others without the written authorization of Rockwell Collins, Inc., except to the extent required for
installation or maintenance of recipient’s equipment. This document is being furnished in
confidence by Rockwell Collins, Inc. The information disclosed herein falls within exemption (b) (4)
of 5 USC 552 and the prohibitions of 18 USC 1905.
SOFTWARE COPYRIGHT NOTICE
© COPYRIGHT 2003 - 2006 ROCKWELL COLLINS, INC. ALL RIGHTS RESERVED.
All software resident in this equipment is protected by copyright.
We welcome your comments concerning this manual. Although every effort has been made to keep
it free of errors, some may occur. When reporting a specific problem, please describe it briefly and
include the manual part number, the paragraph or figure number, and the page number.
Send your comments to: Rockwell Collins, Inc.

Collins Aviation Services
350 Collins Road NE, M/S 153-250
Cedar Rapids, IA 52498-0001
Email: techmanuals@rockwellcollins.com
All requests for product orders or inquiries please contact.
Send your request to: Rockwell Collins, Inc.

Customer Response Center
400 Collins Road NE, M/S 133-100
TELEPHONE: 1.888.265.5467
INTERNATIONAL: 1.319.265.5467
FAX: 319.295.4941
Email: response@rockwellcollins.com
T-2
May 1, 2006
523-0806057
INSERT LATEST CHANGED PAGES. DESTROY SUPERSEDED PAGES.
LIST OF EFFECTIVE PAGES NOTE: The portion of the text affected by the changes is indicated by a vertical line
in the outer margins of the page. Changes to illustrations are indicated by
shaded or screened areas, or by miniature pointing hands.
Dates of issue for original and changed pages are:
Original ... ...... ...... ...... ...... ...... ...... ...... ...... ...... 0 .... ...... ...... ...... ...... ...... ...... ...... . 4 February 2003
Change 1.. ...... ...... ...... ...... ...... ...... ...... ...... ...... 1 .... ...... ...... ...... ...... ...... ...... ...... .... 3 March 2004
Change 2.. ...... ...... ...... ...... ...... ...... ...... ...... ...... 2 .... ...... ...... ...... ...... ...... ...... ...... ...... .1 May 2006
TOTAL NUMBER OF PAGES IN THIS PUBLICATION IS 80 CONSISTING OF THE FOLLOWING:
Page No. *Change No. Page No. *Change No.

Title . ...... ...... ...... ...... ...... ...... ...... ...... .....2 2-11 ..... ...... ...... ...... ...... ...... ...... ...... ...... .2
T-2 .. ...... ...... ...... ...... ...... ...... ...... ...... .....2 2-12 ..... ...... ...... ...... ...... ...... ...... ...... ...... .2
A .... ...... ...... ...... ...... ...... ...... ...... ...... .....2 2-13 ..... ...... ...... ...... ...... ...... ...... ...... ...... .2
B Blank ... ...... ...... ...... ...... ...... ...... ...... .....2 2-14 ..... ...... ...... ...... ...... ...... ...... ...... ...... .2
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*Zero in this column indicates an original page.

1 May 2006 A/(B Blank)
523-0806057
TABLE OF CONTENTS
Chapter Page
LIST OF ILLUSTRATIONS ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... iii
LIST OF TABLES ..... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .. .... iv
INTRODUCTION ..... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .. .... . v
... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .... .. ...... . v
SAFETY SUMMARY . ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ..... . vi
GENERAL ADVISORIES FOR ALL UNITS .... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... vi
SPECIFIC ADVISORIES FOR THE AHS-1000( ) ..... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ..... vii
1 General Information .... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .....1-1
1.1 INTRODUCTION .. ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .....1-1
1.2 PURPOSE OF EQUIPMENT . ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ... 1-14
1.2.1 Attitude Heading Computer ... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ... 1-14
1.2.2 Flux Detector Unit .. ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ... 1-14
1.2.3 External Compensation Unit ... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ... 1-14
1.2.4 Mounting Ears ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ... 1-14
1.3 EQUIPMENT NOT SUPPLIED .... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ... 1-14
1.4 RELATED PUBLICATIONS . ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ... 1-15
1.5 STORAGE .... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ... 1-15
1.6 SHELF LIFE .. ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ... 1-15
2 Installation .. ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .....2-1
2.1 GENERAL .... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .....2-1
2.2 UNPACKING AND INSPECTING EQUIPMENT . ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .....2-1
2.3 PREINSTALLATION CHECK ..... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .....2-1
2.4 SPECIAL INSTRUCTIONS .. ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .....2-1
2.5 PLANNING ... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .....2-1
2.5.1 Installation Configurations .... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .....2-2
2.5.2 Strapping Options .. ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .....2-2
2.5.3 Calibration Mode Discretes .... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .....2-5
2.5.4 Input Power ... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .....2-5
2.5.5 Loading Considerations .. ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .....2-5
2.5.6 Cooling Considerations .. ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .....2-5
2.6 CABLING INSTRUCTIONS . ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .....2-5
2.6.1 General .. ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .....2-5
2.6.2 Connector Contact Assembly and Installation . ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .....2-6
2.7 INSTALLATION PROCEDURES .. ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .....2-7
2.7.1 AHC-1000( ) and Mounting Ears Installation .. ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .....2-7
2.7.2 FDU-3000 Flux Detector Unit . ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ... 2-12
2.7.3 ECU-3000 External Compensation Unit . ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ... 2-12
2.7.4 Synchro-Type Flux Detector Unit ... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ... 2-12
2.8 TESTING ..... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ... 2-12
2.8.1 Preinstallation Testing .... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ... 2-12
2.8.2 Orientation Programming and Postinstallation Test . ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ... 2-12
2.8.3 FDU Compensation Mode Procedure ..... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ... 2-13
3 Operation .... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .....3-1
3.1 GENERAL .... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .....3-1
3.2 CONTROLS AND DISPLAYS ..... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .....3-1
3.2.1 DG MODE (Directional Gyro) Switch ... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .....3-1
3.2.2 SLEW Pushbuttons . ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .....3-1
3.3 OPERATING PROCEDURES ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .....3-1
3.3.1 AHC-1000( ) Operational Data ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .....3-1
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table of contents 523-0806057
Chapter Page
3.3.2 Typical Operation of the AHS-1000( ) Attitude Heading Reference System ..... ...... ...... ...... ...... ...... ....3-1
4 THEORY OF OPERATION .. ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ....4-1
4.1 INTRODUCTION ... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ....4-1
4.2 OVERVIEW ... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ....4-1
4.2.1 Installation Configurations ..... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ....4-1
4.3 FUNCTIONAL THEORY ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ....4-2
4.3.1 Power Source Management ..... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ....4-2
4.3.2 Initialization .... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ....4-5
4.3.3 AHRS Mode Operation ... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ....4-7
5 MAINTENANCE . ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ....5-1
5.1 GENERAL ..... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ....5-1
5.2 MAINTENANCE SCHEDULE ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ....5-1
5.2.1 Power Requirements ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ....5-1
5.3 TESTING AND TROUBLESHOOTING . ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ....5-1
5.3.1 Diagnostic Information ... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ....5-1
ii 1 May 2006
523-0806057
LIST OF ILLUSTRATIONS
Figure Title Page

1-1 AHS-1000( ) Attitude Heading Reference System ... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .....1-2
1-2 ECU-3000 External Compensation Unit Part Number Matrix .. ...... ...... ...... ...... ...... ...... ...... ...... ...... ... 1-17
2-1 Typical AHS-1000A Attitude Heading Reference System Installation .... ...... ...... ...... ...... ...... ...... ...... .....2-3
2-2 Typical AHS-1000S Attitude Heading Reference System Installation ..... ...... ...... ...... ...... ...... ...... ...... .....2-4
2-3 AHC-1000A Mating Connector Pin Assignments ... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ... 2-10
2-4 AHC-1000S Mating Connector Pin Assignments .... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ... 2-11
2-5 AHS-1000A and AHS-1000S Attitude Heading Reference System Interconnect Diagram ...... ...... ...... ...... ... 2-17
2-6 AHC-1000A Attitude Heading Computer, Outline and Mounting Diagram ..... ...... ...... ...... ...... ...... ...... ... 2-25
2-7 AHC-1000S Attitude Heading Computer, Outline and Mounting Diagram ..... ...... ...... ...... ...... ...... ...... ... 2-27
2-8 FDU-3000 Flux Detector Unit, Outline and Mounting Diagram ..... ...... ...... ...... ...... ...... ...... ...... ...... ... 2-29
2-9 FDU-3000 Connector Pin Assignments .. ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ... 2-33
2-10 ECU-3000 External Compensation Unit, Outline and Mounting Diagram ...... ...... ...... ...... ...... ...... ...... ... 2-35
2-11 ECU-3000 Connector Pin Assignments .. ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ... 2-37
4-1 Typical AHS-1000A Attitude Heading Reference System Block Diagram ...... ...... ...... ...... ...... ...... ...... .....4-3
4-2 Typical AHS-1000S Attitude Heading Reference System Block Diagram ...... ...... ...... ...... ...... ...... ...... .....4-4
4-3 AHC-1000A System Components and Signals ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .....4-6
4-4 AHC-1000S System Components and Signals . ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .....4-7
1 May 2006 iii

523-0806057
LIST OF TABLES
Table Title Page

1-1 Equipment Covered. . ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ....1-1
1-2 Equipment Specifications. ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ....1-2
1-3 Performance Characteristics. ... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .. 1-11
1-4 DO-160D Environmental Qualifications. .. ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .. 1-11
1-5 Equipment Associated But Not Supplied. . ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .. 1-15
1-6 Related Publications. ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .. 1-15
2-1 Equipment Mounting Options. . ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ....2-6
2-2 Mating Connector Contacts and Special Tools. . ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ....2-7
2-3 Shim Kit Parts List. .. ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ....2-9
2-4 Postinstallation Test Procedure. ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .. 2-12
2-5 FDU Compensation Mode Procedure. ..... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... .. 2-14
iv 1 May 2006
523-0806057
INTRODUCTION
To submit comments regarding this manual, please contact:
Collins Aviation Services

Rockwell Collins, Inc.
400 Collins Rd NE
Attn: Technical Operations M/S 153-250
or send email to: techmanuals@rockwellcollins.com
1 May 2006 v
523-0806057
SAFETY SUMMARY
GENERAL ADVISORIES FOR ALL UNITS
Service personnel are to obey standard safety precautions, such as wearing safety glasses, to prevent per-
sonal injury while installing or doing maintenance on this unit.
Use care when using sealants, solvents and other chemical compounds. Do not expose to excessive heat or
open flame. Use only with adequate ventilation. Avoid prolonged breathing of vapors and avoid prolonged
contact with skin. Observe all cautions and warnings given by the manufacturer.
Remove all power to the unit before disassembling it. Disassembling the unit with power connected is
dangerous to life and may cause voltage transients that can damage the unit.
This unit may have components that contain materials (such as beryllium oxide, acids, lithium, radioactive
material, mercury, etc) that can be hazardous to your health. If the component enclosure is broken, han-
dle the component in accordance with OSHA requirements 29CFR 1910.1000 or superseding documents
to prevent personal contact with or inhalation of hazardous materials. Since it is virtually impossible to
determine which components do or do not contain such hazardous materials, do not open or disassemble
components for any reason.
This unit exhibits a high degree of functional reliability. Nevertheless, users must know that it is not practical
to monitor for all conceivable system failures and, however unlikely, it is possible that erroneous operation
could occur without a fault indication. The pilot has the responsibility to find such an occurrence by means
of cross-checks with redundant or correlated data available in the cockpit.
Before handling any unit or unit component, ground the repair operator through a conductive wrist strap or
other device that uses a 470kΩ or 1mΩ series resistor to prevent operator injury.
Turn off power before disconnecting any unit from wiring. Disconnecting the unit without turning power
off may cause voltage transients that can damage the unit.
vi 1 May 2006
safety summary 523-0806057
This unit contains electrostatic discharge sensitive (ESDS) components and ESDS assemblies that can be
damaged by static voltages. Although most ESDS components contain internal protection circuits, good
procedures dictate careful handling of all ESDS components and ESDS assemblies.
Obey the precautions given below when moving, touching, or repairing all ESDS components and units
containing ESDS components.
a. Deenergize or remove all power, signal sources, and loads used with the unit.
b. Place the unit on a work surface that can conduct electricity (is grounded).
c. Ground the repair operator through a conductive wrist strap or other device using a 470-kΩ or 1-MΩ
series resistor to prevent unit or unit component damage.
d. Ground any tools (and soldering equipment) that will contact the unit. Contact with the operator’s hand
is a sufficient ground for hand tools that are electrically isolated.
e. All ESDS replacement components are shipped in conductive foam or tubes and must be stored in their
shipping containers until installed.
f. ESDS devices and assemblies that are removed from a unit must immediately be put on the conductive
work surface or in conductive containers.
g. Place repaired or disconnected circuit cards in aluminum foil or in plastic bags that have a layer of, or
are made with, conductive material.
h. Do not touch ESDS devices/assemblies or remove them from their containers until they are needed. Fail-
ure to handle ESDS devices as described above can permanently damage them. This damage can cause
immediate or premature device failure.
SPECIFIC ADVISORIES FOR THE AHS-1000( )
Ensure that the aircraft battery master switch is turned off before installing any equipment, mounts, or inter-
connect cables. Failure to do so could cause electrical arcing that might result in damage to the equipment
or serious injury to maintenance personnel.
The orientation test procedure is critical to ensure the AHS-1000 provides accurate information to the pilot.
The AHC-1000( ) has been designed to exhibit a very high degree of functional integrity. Nevertheless,
the user must recognize that it is not practical to provide monitoring for all conceivable failures and that,
however unlikely, it is possible that erroneous operation could occur without a fault indication. It is the re-
sponsibility of the pilot to detect such an occurrence by means of cross-checks with redundant or correlated
information available in the cockpit.
Replacing the attitude source to an autopilot will require that the safety aspects of the autopilot certification
be addressed. The effort required will depend on the inherent safety mechanisms employed by the autopilot
and the manner in which the AHC-1000A/-1000S units are connected. In general, dual AHC-1000A/-1000S
units will be installed and the connections will be made to the autopilot in such a way as to prevent or
minimize the potential that a failure in a single AHC-1000A/-1000S could result in a multi-axis autopliot
malfunction.
1 May 2006 vii

safety summary 523-0806057
To provide reliable and effective strapping, all connector straps should be kept as short as possible, prefer-
ably under 75 mm (3 in).
To provide reliable lightning protection, each strap is assigned a unique return pin on the rear connector.
Always strap to the assigned return pin, never strap directly to ground.
viii 1 May 2006

523-0806057
CHAPTER 1
General Information
1.1 INTRODUCTION
This publication provides all the specifications, principles of operation, and information necessary to install the AHS-1000( )
Attitude Heading Reference System (AHRS). The AHRS system is comprised of an AHC-1000( ), Attitude/Heading Computer;
an FDU-3000, Flux Detector Unit; and an ECU-3000, External Compensation Unit. Refer to table 1-1 for a list of equipment
covered in this manual. Refer to table 1-2 for the AHS-1000( ) specifications and table 1-3 for the AHS-1000( ) performance
characteristics. An overall view of the AHS-1000( ) is shown in figure 1-1. A list of DO-160D Environmental Qualifications
are shown in table 1-4.
NOTE
This publication provides information on the following AHS-1000( ) Attitude Heading Reference Systems.
• AHS-1000A consisting of an AHC-1000A (822-1871-201), FDU-3000, and ECU-3000
• AHS-1000S consisting of an AHC-1000S (822-1868-201), ECU-3000, and a synchro-type flux detector.
Throughout this publication AHS-1000( ) refers to all systems. System specific information will refer to
the system by AHS-1000A or AHS-1000S. Likewise, AHC-1000( ) refers to all AHC Attitude Heading
Computers. Equipment specific information will refer to the equipment by AHC-1000A or AHC-1000S.
Table 1-1. Equipment Covered.
COLLINS EQUIPMENT DESCRIPTION PART NUMBER

AHC-1000A Attitude Heading Computer capable of a box 822-1871-201
orientation test, 10–minute battery timeout, an
automated FDU compensation function, automated
unit leveling, synchro outputs, and analog rate and
acceleration outputs.
AHC-1000S Same as AHC-1000A except has an interface to a 822-1868-201
synchro-type flux detector.
FDU-3000 Flux Detector Unit. The FDU-3000 is electrically 822-1193-001
compatible with the FDU-70( ). Packaging
modifications have been made to improve index
error adjustment.
ECU-3000 External Compensation Unit, refer to figure 1-2 for 822-1200–209 thru –211
additional information.
Mounting Ears Two standard base plates used for attaching the 653-4320-001
AHC–1000( ) to a horizontal surface.
1 May 2006 1-1

general information 523-0806057
Figure 1-1. AHS-1000( ) Attitude Heading Reference System
Table 1-2. Equipment Specifications.
CHARACTERISTIC SPECIFICATION
Certification
TSO
FAA C4c, C6d
Environmental
FAA
AHC-1000( ), ECU-3000, Mounting Ears DO-160D, refer to table 1-4 for additional information
FDU-3000 DO-160D, refer to table 1-4 for additional information
Physical
Size
AHC-1000A/-1000S
Height 127 mm (5.00 in)
Width 63.5 mm (2.50 in)
Length 317.5 mm (12.50 in)
Weight 2.18 kg (4.8 lb)
ECU-3000
Height 36.3 mm (1.43 in)
1-2 1 May 2006

Table 1-2. Equipment Specifications. - Continued
Width 50.8 mm (2.00 in)
Length 69.8 mm (2.75 in)
FDU-3000
Height 68.3 mm (2.69 in)
Width 120.9 mm (4.76 in)
Mounting Ears (2)
Height 4.78mm (0.188 in) MAX
Width 50.8 mm (2.00 in)
Weight NA
Mounting
AHC-1000( ) Mounting Ears (refer to installation section for additional information)
FDU-3000 Optional mounting plate assembly (CPN 628-9778-001) (refer to installation
section for additional information)
ECU-3000 Mounts to aircraft frame, near the AHC-1000( ) (refer to installation section
for additional information)
Mating Connector
AHC-1000( ) MS27467T25F35S (CPN 359-0657-110)
Backshell: M85049/49-2-24N (CPN 859-6604-180)
Crimp Contacts: M39029/56-348 (CPN 359-0608-130) Qty = 128
FDU-3000 MS27472P10C35S (CPN 859-0007-010) with crimp sockets.
Alternate: MS27499E10C35S, MS27513E10C35S, MS27497 (E, P or T)
10C35S, MS27508E10C35S, MS27474 (E,P, or T) 10C35S.
ECU-3000 MS27484T10F35S (CPN 359-0645-020)
Backshell: M85049/49-2-10N (CPN 859-6604-110)
Time between overhaul No specific overhaul interval. Unit should be thoroughly tested and repaired
anytime maintenance is performed on it.
Electrical
1 May 2006 1-3

AHC-1000( )
Power
Input Pwr (P1-14) AHC-1000A: +28 V dc Primary (H), (24 W nominal; 33 W nominal, with
synchro loads; 60 W nominal, with all analog loads)
AHC-1000S: +28 V dc Primary (H), (22.5 W nominal; 31.5 W nominal,
with synchro loads; 60W nominal, with all analog loads)
Battery Pwr (P1- 23) (Enabled when primary input falls below +18 V dc)
AHC-1000A: +28 V dc Primary (H), (24 W nominal, no loads; 33 W nom-
inal, with synchro loads; 60 W nominal, with all analog loads)
AHC-1000S: +28 V dc Primary (H), (22.5 W nominal; 31.5 W nominal,
with synchro loads; 60 W nominal, with all analog loads)
Power Gnd (P1-46) +28 V dc Primary (L)
Battery Gnd (P1-57) +28 V dc Battery (L)
Chassis Gnd (P1-58) Chassis Ground
Straps
AHC Box Orient (Fore) (P1-123) strap = face fore; open = not selected
AHC Box Orient (Aft) (P1-59) strap = face aft; open = not selected
AHC Box Orient (Starboard) (P1-109) strap = face starboard; open = not selected
AHC Box Orient (Port) (P1-74) strap = face port; open = not selected
AHC Box Orient COM (P1-105) Box orientation strap common
Source ID (P1-61/106) Gnd (P1-95)/open; gnd = 0, open = 1
Source ID Inputs:
1 (left) P1-61 Open, P1-106 Gnd (01)
2 (right) P1-61 Gnd, P1-106 Open (10)
3 (center) P1-61 Open, P1-106 Open (11)
4 (none) P1-61 Gnd, P1-106 Gnd (00)
Source ID Common (P1-95) Source ID common

Strap Common (P1-65) Ground
ECU Interface Pins
ECU Chip Select 1/2 (P1-124/99) +8 V dc/gnd discrete outputs (gnd = chip selected)
ECU Write Protect 1/2 (P1-125/77) +8 V dc/gnd discrete outputs (gnd = chip write disabled)
ECU Power (+8 V DC) (P1-34) +8 V dc power to ECU
ECU Ground (P1-35) Power ground to ECU
1-4 1 May 2006

ECU Clock (P1-110) Clock output to ECU controls serial bus timing for I/O data
ECU Serial Data RX (P1-118) Input 0/+8 V dc serial data synchronous with clock
ECU Serial Data TX (P1-100) Output 0/+8 V dc serial data synchronous with clock
FDU Interface Pins
AHC-1000A
FDU Excitation SIN/COS (P1-3/5) Sine/cosine excitation voltage outputs to flux detector
FDU Excitation Com (P1-4) Common excitation voltage output to flux detector
FDU Signal SIN/COS (P1-10/12) Sine/cosine inputs from flux detector
FDU Signal Com (P1-11) Common input from flux detector
AHC-1000S
FDU Excitation A/B (P1-3/5) 400 Hz excitation voltage outputs to a synchro-type flux detector
FDU Signal A/B/C (P1-10/11/12) Signal inputs from a synchro-type flux detector
Discrete Inputs
Weight on Wheels (P1-122) Gnd/open (gnd = on ground; open = in air)
DG Mode Select (P1-94) 28V/open (28V = DG mode; open = mag slave mode)
Slew Right (P1-115) 28V/open (28V = slew right; open = inactive)
Slew Left (P1-82) 28V/open (28V = slew left; open = inactive)
FDU Comp Mode Sel (P1-117) Gnd/open (gnd =FDU compensation mode; open = inactive)
Unit Leveling Enable (P1-72) Gnd/open (gnd = MMT leveling mode; open = inactive)
Field Test Mode Sel (P1-116) Gnd/open (gnd = test; open = inactive)
Bench Test Mode Sel (P1-73) Gnd/open (gnd = test; open = inactive).
Heading Sync Command (P1–96) 28V-open (28V = inactive; open = SYNC mode)
NOTE
Heading Sync Command is only active when ECU 822–1200–210 is
installed.
NOTE
Bench Test Mode Select is intended for bench testing only; it should
not be connected in the aircraft.
Discrete Outputs
Attitude Valid (P1-13) Open/+28 V dc (open = invalid; +28 V dc (320 mA max at +27.5 V dc) =
valid)
Heading #1 Valid (P1-20) Open/+28 V dc (open = invalid; +28 V dc (320 mA max at +27.5 V dc) =
valid)
1 May 2006 1-5

Heading #2 Valid (P1-98) Open/+28 V dc (open = invalid; +28 V dc (320 mA max at +27.5 V dc) =
valid)
Configurable Discrete Outputs These discrete outputs can be disabled by configuration information stored
in the ECU. Future versions of the equipment may be able to redefine the
outputs based on information in the ECU.
Config Discrete #1 (Basic Mode Annunc) Open/+28 V dc (open = Normal Mode; +28 V dc (100 mA max at +27.5 V
(P1-6) dc) = Basic Mode)
Config Discrete #2 (Initialization Annunc) Open/+28 V dc (open = Not Initialization; Open alternating with +28 V dc
(P1-19) (100 mA max at +27.5 V dc) = Initialization)
Config Discrete #3 (6 Degree Roll Annunc) Open/+28 V dc (open = Roll <5.75 degrees; +28 V dc (100 mA max at +27.5
(P1-7) V dc) = Roll >6.25 degrees. Roll between 5.75 and 6.25 degrees = no change
in output (hysteresis)).
Analog Inputs
26 V ac Synchro References
26 V ac Attitude Ref (H) (P1-42) Minimum voltage between 26 V ac attitude reference (H) and (L) is 14.6 V
ac (0.1 VA).
26 V ac Attitude Ref (L) (P1-53)
26 V ac Hdg #1 Ref (H) (P1-41) Minimum voltage between 26 V ac heading #1 reference (H) and (L) is 14.6
V ac (0.1 VA).
26 V ac Hdg #1 Ref (L) (P1-52)
26 V ac Hdg #2 Ref (H) (P1-60) Minimum voltage between 26 V ac heading #2 reference (H) and (L) is 14.6
V ac (0.1 VA).
26 V ac Hdg #2 Ref (L) (P1-68)
Analog Outputs
Pitch Synchro Outputs The AHC-1000A/-1000S provides two standard 3-wire pitch synchro out-
puts. Each is capable of driving up to three 220 +j450 ohm loads.
Pitch #1 X (P1-25) Each synchro output with full synchro load draws an additional 65 mA (max-
imum at +27.5 V dc) from the +28 V dc input.
Pitch #1 Y (P1-37)
Pitch #1 Z (P1-38)
Pitch #2 X (P1-8)
Pitch #2 Y (P1-1)
Pitch #2 Z (P1-2)
Roll Synchro Outputs The AHC-1000A/-1000S provides two standard 3-wire roll synchro outputs.
Each is capable of driving up to three 220 +j450 ohm loads.
1-6 1 May 2006

Roll #1 X (P1-15) Each synchro output with full synchro load draws an additional 65 mA (max-
imum at +27.5 V dc) from the +28 V dc input.
Roll #1 Y (P1-26)
Roll #1 Z (P1-27)
Roll #2 X (P1-16)
Roll #2 Y (P1-17)
Roll #2 Z (P1-9)
Heading Synchro Outputs The AHC-1000A/-1000S provides two standard 3-wire heading synchro out-
puts. Each is capable of driving up to four 120 +j450 ohm loads.
Heading #1 X (P1-36) Each synchro output with full synchro load draws an additional 105 mA
(maximum at +27.5 V dc) from the +28 V dc input.
Heading #1 Y (P1-48)
Heading #1 Z (P1-49)
Configurable Synchro/Analog Outputs The AHC-1000A/-1000S provides a set of configurable synchro/analog

outputs on P1-75, P1–85, and P1–97. Default is to provide a standard
3-wire heading synchro output. Configuration of these outputs is controlled
by ECU. See Figure 1–2.
Configurable Output 1 (P1–75)
Heading #2 X Default configuration
Heading SYNC Error (H)(167mv/°/s) When ECU 822–1200–210 installed.
Roll Rate (H)(95mv/°/s) When ECU 822–1200–211 installed.
Heading #2 Y Default configuration
Yaw Rate (H)(154mv/°/s) When ECU 822–1200–210 or -211 installed.

Heading #2 Z Default configuration
(L) Connection for Configurable Out- When ECU 822–1200–210 or -211 installed.
puts 1 and 2
Weather Radar Pitch Output The AHC-1000A/-1000S provides a stabilization pitch output for use by
weather radar systems. The output is a two-wire synchro output provid-
ing 0.1127 (RMS voltage of 26 V ac Attitude Reference [sine(x)/x] V ac/°,
where x is pitch angle in degrees. This output is commonly referred to as a
50 mV/degree output.
1 May 2006 1-7

WXR Pitch (H) (P1-50) The amplitude and phase of the output is proportional to the sine of the pitch
angle. The output is capable of driving one 10 kilohm load. The output in-
WXR Pitch (L) (P1-62)
dicates positive pitch when the voltage between H and L is in phase with
respect to the 26 V ac Attitude Reference. Other general output character-
istics follow the ARINC 561 Characteristics definition - Range: 0 to ±90
degrees; Resolution: 0.1 degree; Accuracy: 0.5 degree; Index Resolution: 0
V = horizon; Positive Direction: nose up; Phase Angle; 0 ±3 degrees.
2-Wire Pitch Output The AHC-1000A/-1000S provides a 2-wire (X and Y) ac pitch output for
use by weather radar systems, autopilots, and other equipment. The two-
wire synchro output provides a voltage of 0.4503 (RMS voltage of 26 V ac
Attitude Reference [sine(x)/x] V ac/°, where x is pitch angle in degrees. This
output is commonly referred to as a 200 mV/degree output.
2-Wire Pitch (X) (P1-43) The amplitude and phase of the output (Y-X) is proportional to the sine of
the pitch angle. The output indicates positive pitch when the voltage be-
2-Wire Pitch (Y) (P1-66)
tween Y and X is in phase with respect to the 26 V ac Attitude Reference.
Other general output characteristics follow the ARINC 561 Characteristics
definition - Range: 0 to ±90 degrees; Resolution: 0.1 degree; Accuracy: 0.5
degree; Index Resolution: 0 V = horizon; Positive Direction: nose up; Load
Required: 10 kilohms; Phase Angle; 0 ±3 degrees.
Weather Radar Roll Output The AHC-1000A/-1000S provides a linear stabilization roll output for use
by weather radar systems. The output is a two-wire synchro output provid-
ing 0.1127 (RMS voltage of 26 V ac Attitude Reference [sine(x)/x] V ac/°,
where x is roll angle in degrees. This output is commonly referred to as a
50 mV/degree output.
WXR Roll (H) (P1-39) The amplitude and phase of the output is proportional to the sine of the roll
angle. The output is capable of driving one 10 kilohm load. The output
WXR Roll (L) (P1-51)
indicates positive roll when the voltage between H and L is in phase with
respect to the 26 V ac Attitude Reference. Other general output characteris-
tics follow the ARINC Characteristics definition - Range: 0 to ±90 degrees;
Resolution: 0.1 degree; Accuracy: 0.5 degree; Index Resolution: 0 V =
horizon; Positive Direction: right wing down; Phase Angle; 0 ±3 degrees.
2-Wire Roll Output The AHC-1000A/-1000S provides a 2-wire (X and Y) ac roll output for use
by weather radar systems, autopilots, and other equipment. The two-wire
synchro output provides a voltage of 0.4503 (RMS voltage of 26 V ac At-
titude Reference [sine(x)/x] V ac/°, where x is roll angle in degrees. The
selected scale factor is determined by data stored in the ECU-3000. This
output is commonly referred to as a 200 mV/degree output.
1-8 1 May 2006

2-Wire Roll (X) (P1-40) The amplitude and phase of the output (Y-X) is proportional to the sine of
the pitch angle. The output indicates positive roll when the voltage between
2-Wire Roll (Y) (P1-29)
Y and X is in phase with respect to the 26 V ac Attitude Reference. Other
general output characteristics follow the ARINC 561 Characteristics defi-
nition - Range: 0 to ±90 degrees; Resolution: 0.1 degree; Accuracy: 0.5
degree; Index Resolution: 0 V = horizon; Positive Direction: right wing
down; Load Required: 10 kilohms; Phase Angle; 0 ±3 degrees.
Normal Acceleration Output The AHC-1000A/-1000S provides an analog normal acceleration output.
Normal Accel Out (H) (P1-21) The Normal Acceleration Output provides a scale factor of 2.5 V dc/g pro-
portional to the normal acceleration. The range is 0 to ±10 V dc (i.e. ±4.00
Normal Accel Out (L) (P1-32)
g). The null stability is ±100 mV dc. The output is capable of driving one
10 kilohm load. A positive output indicates upward acceleration.
Lateral Acceleration Output The AHC-1000A/-1000S provides an analog lateral acceleration output.
Lateral Accel Out (H) (P1-22) The Lateral Acceleration Output provides a scale factor of 19.32 V dc/g
proportional to the lateral acceleration. The range is 0 to ±10 V dc (i.e.
Lateral Accel Out (L) (P1-33)
±0.5176 g). The null stability is ±100 mV dc. The output is capable of
driving one 10 kilohm load. A positive output indicates acceleration through
the right wing.
Pitch Rate Output The AHC-1000A/-1000S provides an analog pitch rate output.
Pitch Rate (H) (P1-54) The Pitch Rate Output provides a scale factor of 200 mV dc/degree/sec-
ond proportional to body pitch rate. The range is 0 ±10 V dc (i.e. ±50
Pitch Rate (L) (P1-32)
degrees/second). The output is capable of driving two 10 kilohm loads.
Roll Rate Output The AHC-1000A/-1000S provides an analog roll rate output.
Roll Rate (H) (P1-31) The Roll Rate Output provides a scale factor of 200 mV dc/degree/second
proportional to body roll rate. The range is 0 ±10 V dc (i.e. ±50 degrees/sec-
Roll Rate (L) (P1-33)
ond). The output is capable of driving two 10 kilohm loads.
Yaw Rate Output The AHC-1000A/-1000S provides an analog yaw rate output.
Yaw Rate (H) (P1-55) The Yaw Rate Output provides a scale factor of 200 mV dc/degree/second
proportional to aircraft of turn. The range is 0 ±4 V dc (i.e. ±20 degrees/sec-
Yaw Rate (L) (P1-67)
ond). The output is capable of driving one 1 kilohm load. Positive output
indicates a right turn.
Slave Meter Output The AHC-1000A/-1000S provides a slave meter output.
1 May 2006 1-9

Slave Meter (H) (P1-30) The Slave Meter Output provides a scale factor of 0.1 V dc/degree of heading
difference. The range is ±0.5 V dc (i.e. ±5.0 degrees). A positive output
Slave Meter (L) (P1-45)
indicates the computed heading is greater than the heading sensed by the
FDU-3000. The output is 0 V dc when the AHC-1000A is in DG Mode.
Reserved (P1-18/ 24/ 28/ 44/ 47/ 56/ 63/ 64/ 69/ All pins reserved for future requirements on AHC-1000A.
70/ 71/ 76/ 78/ 79/ 80/ 81/ 83/ 84/ 86/ 87/ 89/
90/ 91/ 92/ 93/ 101/ 102/ 103/ 104/ 108/ 111/
112/ 113/ 114/ 119/ 120/ 121/ 126/ 127/ 128)
Reserved (P1-4/ 18/ 24/ 28/ 44/ 47/ 56/ 63/ 64/ All pins reserved for future requirements on AHC-1000S.
69/ 70/ 71/ 76/ 78/ 79/ 80/ 81/ 83/ 84/ 86/ 87/
90/ 91/ 92/ 93/ 101/ 102/ 103/ 104/ 108/ 111/
112/ 113/ 114/ 119/ 120/ 121/ 126/ 127/ 128)
FDU-3000
Inputs
Cosine Excitation (P1-1) Cosine excitation voltage from heading computer
Excitation Com (P1-2) Common excitation voltage from heading computer
Sine Excitation (P1-5) Sine excitation voltage from heading computer
Outputs
Cosine Signal (P1-3) Cosine signal to heading computer
Sine Signal (P1-7) Sine signal to heading computer
Signal Com (P1-4) Signal common to heading computer
Other
Excitation Shield (P1-6) Ground connection for shielded cable
Signal Shield (P1-8) Ground connection for shielded cable
Spare (P1-9/10)
ECU-3000
Power
ECU Power (+8 V DC) (P1-1) +8V dc power provided by AHC-1000( )
ECU Ground (P1-9) ECU power return/common
Inputs
ECU Chip Select 1/2 (P1-2/5) +8 V dc/gnd discrete (gnd = chip selected)
ECU Write Enable 1/2 (P1-3/6) +8 V dc/gnd discrete (gnd = chip write disabled)
ECU Clock (P1-7) +8 V dc/gnd clock controls serial bus timing for I/O data
ECU Serial Data RX (P1-8) 0/+8 V dc serial data input, synchronous with clock
1-10 1 May 2006

Outputs
ECU Serial Data TX (P1-4) 0/+8 V dc serial data, synchronous with clock
Table 1-3. Performance Characteristics.
CHARACTERISTIC RANGE Nominal Accuracy (2 sigma )

Pitch ± 90° ± 1.0° steady level flight; ± 2.5° maneuvers
Roll ± 180° ± 1.0° steady level flight; ± 2.5° maneuvers
Heading ± 180° ± 1.5° steady level flight; ± 2.5° maneuvers
Body Rates ± 880°/sec ± 0.08°/sec bias; ± 0.5% scale factor error
Accelerations ± 15 gravities (g) ± 0.005 g bias; ± 0.5% scale factor error
Table 1-4. DO-160D Environmental Qualifications.
CHARACTERISTIC DO-160D QUALIFICATION LEVEL

PARA NO
Temperature and Altitude 4.0 Category A2, F2
Low Operating Temp 4.5.1 -55 °C (-67 °F) Category F2
High Operating Temp 4.5.3 +70 °C (+158 °F) Category F2
Low Storage Temp 4.5.1 -55 °C (-67 °F) Category F2
High Storage Temp 4.5.2 +85 °C (+185 °F) Category F2
In-Flight Cooling Loss 4.5.4 Category X: Not applicable
Altitude 4.6.1 Category F2: Certified for installation in a non-pressurized and non-controlled
temperature location in an aircraft that is operated at altitudes up to 16 800 m
(55 000 ft) msl.
Decompression 4.6.2 Category A2: Certified for installation in a partially controlled temperature lo-
cation in an aircraft where pressures are no lower than an altitude equivalent of
4600 m (15 000 ft) msl.
Overpressure 4.6.3 Category A2: Certified for installation in a partially controlled temperature lo-
cation in an aircraft where pressures are no lower than an altitude equivalent of
4600 m (15 000 ft) msl.
Temperature Variation 5.0 Category B: Certified for installation in a non-controlled or partially controlled
temperature location in the aircraft where temperature variation is less than 5°C
per minute.
Humidity 6.0 Category B: Certified for a Severe Humidity Environment
Shock 7.0 Category B: Certified for installation in fixed-wing aircraft or helicopters and
tested for standard operational shock and crash safety.
Operational 7.2 Tested at 6 g peak (11 ms duration)
1 May 2006 1-11

Table 1-4. DO-160D Environmental Qualifications. - Continued

PARA NO
Crash Safety 7.3
Impulse 7.3.1 Tested at 20 g (11 ms duration)
Sustained 7.3.2 Tested at 20 g min (acceleration)
Vibration 8.0 Categories S, T, and U
AHC-1000( ), ECU-3000 Category S: Certified for aircraft zone 1 mounting in a fixed wing turbojet en-
gine aircraft, fixed wing reciprocating/turbojet engine aircraft multi-engine over
12 000 lbs using vibration curves C, L, and M.
FDU-3000 Category S: Certified for aircraft zone 5 mounting in a fixed wing turbojet en-
gine aircraft, fixed wing reciprocating/turboprop engine aircraft multi-engine
over 12 000 lbs using vibration curves E and T.
AHC-1000A/-1000S, Category T: Certified for aircraft zone 1 mounting for fixed wing turbojet
ECU-3000, Mounting engine aircraft using vibration curves C, C1 and R.
Ears
AHC-1000A/-1000S, Category U: Certified for aircraft zone 1 for helicopters using curves F and F1.
ECU-3000, Mounting
Ears
Explosion Proofness 9.0 Category E: Certified for installation in a location where an explosive atmos-
phere may occur either continuously or intermittently as a result of uncovered
flammable fluids or where vapors may exist.
Waterproofness 10.0 Category X: No test required. Certified for installation in locations not subject
to falling water (including condensation), rain water, or sprayed water. OR Cat-
AHC-1000A/-1000S
egory W: Certified for installation in locations subject to falling water (including
condensation, rainwater, or spayed water).
Fluids Susceptibility 11.0 Category X: No test required. Certified for installation in locations not exposed
to fluid contamination from fuel, hydraulic fluids, oil, solvents, etc.
Sand and Dust 12.0 Category X: No test required. Certified for installation in locations not subject
to blowing sand and dust.
Fungus Resistance 13.0 Category X: Fungus resistance test not performed.
Salt Spray 14.0 Category X: Salt spray test not performed. Certified for installation in locations
not subject to a salt atmosphere.
AHC-1000A/-1000S
Category S8: Tested for salt spray. Certified for installation in locations subject
to a salt atmosphere.
Magnetic Effect 15.0 Category Z: Unit causes a 1° deflection of an uncompensated compass at a dis-
tance less than 0.3 m (1.0 ft).
1-12 1 May 2006


PARA NO
Power Input 16.0 Categories A, B and Z
Category A: Certified for use on aircraft electrical systems where primary power
is from constant frequency ac generators and the dc system is from a trans-
former-rectifier. A battery may be floating on the dc bus.
Category B: Certified for use on aircraft electrical systems where primary power
is from engine driven alternator/rectifiers or dc generator where a significant
capacity battery is floating on the dc bus at all times.
Category Z: Certified for use on aircraft electrical systems not applicable to any
other category. For example, a dc system from a variable range generator where
a small capacity or no battery is floating on the dc bus.
Voltage (Average Power 16.5.2.1 Equipment tested to categories B and Z
DC)
Ripple Voltage 16.5.2.2 See Section 18.0 for this test
Momentary Power 16.5.2.3 Equipment tested to category A
Interruptions
Normal Surge Voltage 16.5.2.4 Equipment tested to categories B and Z
(DC)
Engine Starting 16.5.2.5 Equipment tested to categories B and Z
Undervoltage Operation
Voltage Steady State 16.5.4.1 Equipment tested to categories B and Z
Low Voltage Conditions 16.5.4.2 Equipment tested to category B
Momentary Undervoltage 16.5.4.3 Equipment tested, but no applicable category
Operation
Abnormal Surge Voltage 16.5.4.4 Equipment tested to categories B and Z
(DC)
Voltage Spike 17.0 Category A: Certified for installation in systems where a high degree of voltage
spike protection is required.
Audio Frequency Suscep- 18.0 Category Z: Certified for use on aircraft electrical systems not applicable to any
tibility other category. For example, a dc system from a variable range generator where
a small capacity or no battery is floating on the dc bus.
Induced Signal Suscepti- 19.0 Category Z: Certified for operation in systems where interference-free operation
bility is required.
RF Susceptibility 20.0 Categories Y and X
Conducted 20.4 Category Y: Certified for installation in a severe electromagnetic environment.
Radiated 20.5 Category Y: Certified for installation in a severe electromagnetic environment.
Pulse 20.5(e) Category X: No test required
Emission of RF Energy 21.0 Category H: Certified for equipment located in areas in direct view of the radio
receiver’s antenna, typically for equipment located outside the aircraft.
1 May 2006 1-13


PARA NO
Lightning Induced Tran- 22.0 Category Z3: Certified per pin test waveform set A3, section 22 DO-160D; with
sient Susceptibility additional testing of waveform 5A, level 3 on powerline input.
Category Z4: Certified per cable bundle test waveform set E4, section 22
DO-160D; with multiple strokes and Multiple burst waveforms per AC 20-136.
Lightning Direct Effects 23.0 Category X: No test required. Certified for operation for which lightning effects
are insignificant or not applicable.
Icing 24.0 Category A: Certified for installation in a non-controlled temperature location
where ice or frost may form.
ESD 25.0 Category A: Certified for installation where electronic equipment is installed,
repaired, or operated in an aerospace environment.
1.2 PURPOSE OF EQUIPMENT

The AHS-1000( ) is an attitude and heading reference system that uses a quartz-based inertial sensing technology. It is targeted
for installations where analog interfaces are required to support older equipment such as analog autopilots, weather radars, and
RMIs, and as a replacement for vertical gyro and directional gyro units in installations that will retain analog interfaces for
primary display of attitude and heading.
1.2.1 Attitude Heading Computer The AHC-1000( ) uses quartz-based inertial sensors to measure angular rates and
linear accelerations about the body axis of the aircraft. Discrete strap inputs set the specific system configuration. The AHC-
1000( ) provides pitch, roll, and heading synchro outputs and analog rate and acceleration outputs. The AHC-1000S provides
an interface to a 5-wire synchro-type flux detector unit. All processing within the AHS-1000( ) system is performed by the
AHC-1000( ) computer.
1.2.2 Flux Detector Unit The FDU-3000 is a gimbaled 2-axis magnetic sensor that detects the horizontal component of
the earth’s magnetic field. The FDU is an analog device and does not contain any memory or processing capability. The AHC-
1000( ) outputs an excitation signal to the FDU. The FDU outputs a magnetic flux measurement back to the AHC-1000( )
proportional to the sine and cosine of the magnetic heading angle. The AHC-1000( ) converts the sine and cosine measurement
to an aircraft heading angle.
1.2.3 External Compensation Unit The ECU-3000 is used to store aircraft specific compensation and configuration data.
It remains with the aircraft during replacement of the AHC-1000( ). Refer to figure 1-2 for a list of available statuses of the
ECU-3000 used with the AHC-1000( ). The data included includes flux detector compensation, battery timeout values, and
leveling compensation values.
The flux detector compensation data is used to reduce the “hard iron” errors and flux detector misalignment. The data is calcu-
lated by the AHC-1000( ) and stored in the ECU during an automated compass swing procedure. The leveling compensation
data accounts for mount misalignment up to three degrees in the pitch and roll axes. The data is calculated and stored during an
automated leveling procedure.
Configuration options are programmed at the factory. All AHS-1000( ) systems include a configuration option for the Battery
Timeout value. This value determines the amount of time the AHC-1000( ) will operate using power available at its back-up
power input following loss of power on the primary input. The default value is 10 minutes.
1.2.4 Mounting Ears A precise alignment or calibration of the AHC-1000( ) to the mounting surface is required to provide
accurate attitude information. The mounting ears have neither electronics nor software.
1.3 EQUIPMENT NOT SUPPLIED
The AHS-1000( ) Attitude Heading Reference System is appropriate for installation in Collins Integrated Avionics Systems
(Pro Line 4 and Pro Line 21). Additionally, the AHS may be installed with other equipment. Associated equipment is listed in
table 1-5. The AHS-1000A/-1000S Heading Reference System is appropriate in aircraft that use synchro/analog interfaces for
AHRS data.
1-14 1 May 2006

1.4 RELATED PUBLICATIONS

Publications related to AHS-1000( ) operation are listed in table 1-6.
1.5 STORAGE
The AHS-1000( ) should be stored in its original packing materials and shipping container. If the unit is to be stored for a long
period of time, put the unit in an airtight plastic bag with sufficient desiccant to absorb moisture. At no time should the ambient
temperature of the storage area fall below -55 °C (-67 °F) or rise above +85 °C (+185 °F). The relative humidity should never
exceed 95 percent. If the unit is stored for an extended period of time, retest the unit prior to returning it to service to ensure
that possible component degradation has not affected performance.
1.6 SHELF LIFE
The AHC-1000( ) does not have a specific shelf life. Refer to Appendix C of the Avionics General Shop Practices manual for
shelf life guidelines for general equipment.
Table 1-5. Equipment Associated But Not Supplied.
EQUIPMENT TYPE OR DESCRIPTION QTY

Flight instrument system EFIS-85; displays pitch/roll attitude and heading data. AHS-
1000( ) will also interface with conventional electromechanical
instruments.
Flight guidance system ARINC 429 capable APS-85.
Weather radar system WXR-840/TWR-850 receives stabilization pitch/roll attitudes.
Flight data recorder Records heading and pitch/roll attitudes. 1
Leveling Fixture CPN 653-2906-003, insures mount alignment within ±0.1 de- 1
gree. (purchase or rent)
Shim Kit CPN 653-2927-001, 13 various thickness shims to level the 1
Mounting Ears mount.
Table 1-6. Related Publications.
PUBLICATION COLLINS PART NUMBER

Avionics Standard Shop Practices 523-0768039
Collins Installation Practices Manual 523-0775254
APS-65 Autopilot and FGS-65 Flight Guidance System Installation Manual 523-0771862
APS-85 Autopilot System Instruction Book 523-0772076
EFIS-85B(4/14)/86B(4/14) Electronic Flight Control System 523-0775353
EFIS-85C(4/14)/86C(4/14) Electronic Flight Control System 523-0775637
EFIS-86E(4/14) Electronic Flight Control System 523-0775613
EFIS-84 Electronic Flight Control System 523-0775963
FCS-105 Flight Control System Instruction Book 523-0762755
MND-640( ) Multisensor Navigation Display 523-0775935
1 May 2006 1-15/(1-16 Blank)

Figure 1-2. ECU-3000 External Compensation Unit Part Number Matrix
1 May 2006 1-17/(1-18 Blank)

523-0806057
CHAPTER 2
Installation
2.1 GENERAL
NOTE
The information and instructions provided in this section are recommendations and do not necessarily corre-
spond with any actual aircraft installation and wiring. This section cannot be used in place of a Supplemental
Type Certificate (STC) or Type Certificate (TC).
This section provides all information needed to install the Collins® AHS-1000( ) Attitude Heading Reference System. The
following topics are included in this section: mounting, mating connectors and contacts, cabling, and system interconnect.
2.2 UNPACKING AND INSPECTING EQUIPMENT
Unpack equipment carefully and make a careful visual inspection of the unit for possible shipping damage. All claims for
damage should be filed with the transportation company involved. If claims for damage are to be filed, save the original shipping
container and materials. If no damage can be detected, replace packing materials in the shipping container and save for future
use (such as storage or reshipment).
2.3 PREINSTALLATION CHECK
Before installing the equipment in an aircraft it is recommended to connect the unit in a system mock up to verify proper oper-
ation.
2.4 SPECIAL INSTRUCTIONS
The following instructions must be followed to ensure proper installation of the AHS-1000( ).
Replacing the attitude source to an autopilot will require that the safety aspects of the autopilot certification
be addressed. The effort required will depend on the inherent safety mechanisms employed by the autopilot
and the manner in which the AHC-1000A/-1000S units are connected. In general, dual AHC-1000A/-1000S
units will be installed and the connections will be made to the autopilot in such a way as to prevent or
minimize the potential that a failure in a single AHC-1000A/-1000S could result in a multi-axis autopliot
malfunction.
NOTE
Aircraft approved wire must always be used.
• The minimum wire size for power lines is #20 AWG. #22 AWG wire can be used for all other lines
• Read all notes on drawings and interconnects and the planning paragraph before installing any units or cabling
• All straps on the AHS-1000( ) have specific return pins on the rear connector. Straps used must be connected to the
appropriate return pin to ensure reliable operation
• Both the AHC-1000( ) and the FDU-3000 or synchro-type Flux Detector Unit (FDU) must be mounted on surfaces that are
level with respect to the aircraft level reference. Specifications are provided in this section
• Both the AHC-1000( ) and the FDU-3000 or synchro-type FDU, must be aligned with the aircraft longitudinal axis. Speci-
fications are provided in this section
• The FDU-3000 or synchro-type FDU must be mounted as far as possible (minimum of 610 mm (2 ft)) from any ferrous
materials and electrical conductors that carry direct current
• After all units are installed, the testing and alignment procedures listed in paragraph 2.8 must be performed to ensure opera-
tional accuracy
• An ECU-3000 must be installed to complete the installation. When the AHC-1000( ) is removed from the aircraft for any
reason, the ECU-3000 is to remain on board.
2.5 PLANNING
Proper and careful planning prior to installation is essential for reliable performance and easy maintenance. The following list
is a sample of the points to be considered in planning an installation:
1 May 2006 2-1

installation 523-0806057
• Single or dual installation

• Installation location (adequate airflow for cooling, good bonding to aircraft ground, ease of cable routing, room for single or
dual mounting in a location that provides structural rigidity)
• Installation configuration
• Compatibility with other equipment loading considerations.
2.5.1 Installation Configurations The AHS-1000( ) is normally configured as a dual installation. Complete configuration
is dependent on the desired connection to ancillary equipment. A typical dual installation is shown in figure 2-1 (AHS-1000A),
and figure 2-2 (AHS-1000S).
2.5.2 Strapping Options
To provide reliable and effective strapping, all connector straps should be kept as short as possible, prefer-
ably under 75 mm (3 in).
To provide reliable lightning protection, each strap is assigned a unique return pin on the rear connector.
Always strap to the assigned return pin, never strap directly to ground.
Strapping in the AHS-1000( ) wiring harness configures the AHC-1000( ) for either left (port), right (starboard), fore or aft
facing mounting. This must be done so that the AHC-1000( ) can correctly interpret aircraft motion as pitch or roll and with
correct polarity. The AHC Source ID straps, P1-61/106 (LSB/MSB) and Source ID Common (P1-95), are strapped to identify
the unit’s location within an aircraft installation. The AHC will read the Source ID strapping and determine the unit location.
Refer to table 1-2 for strapping logic.
2-2 1 May 2006

Figure 2-1. Typical AHS-1000A Attitude Heading Reference System Installation
1 May 2006 2-3

Figure 2-2. Typical AHS-1000S Attitude Heading Reference System Installation
2-4 1 May 2006

2.5.3 Calibration Mode Discretes The FDU Compensation Mode Select (P1-117) discrete input to the AHC-1000( )
must be grounded during an FDU Compensation Mode (compass swing) procedure. This procedure is performed during initial
installation and after replacement of the FDU-3000 or synchro-type FDU, or ECU-3000. This procedure is not required after
replacement of the AHC-1000( ). The procedure calibrates the compass system to compensate for aircraft magnetic field distur-
bances near the flux detector. P1-117 should be connected to a switch that is located in the cockpit, or other convenient location,
for easy activation during the procedure.
In the AHC-1000A/-1000S, the Unit Leveling Enable (P1-72) must be grounded during the unit leveling procedure. This pro-
cedure is performed during any installation or re-installation of the AHC-1000( ) or the ECU-3000. The procedure provides
information regarding the misalignment between the AHC-1000( ) mounting surface and the aircraft level surface to provide
accurate aircraft attitude information. P1-72 should be connected to a switch that is located in the cockit, or other convenient
location, for easy activation during the procedure.
2.5.4 Input Power The AHC-1000A/-1000S is designed to operate from a primary power input source with a nominal
voltage of 27.5 V dc (25 +10 amp start/surge (<10 msec); 0.84 +0.10 amp running with no synchro load, or 1.00 +0.10 amp
running with full synchro load). The system is designed to require 24 W with no analog (discretes or synchro) loads, 33 W with
full synchro loading, and 60 W with full analog loading. The actual power will depend on the analog loads connected. Most of
the power required for the loads is dissipated by the loads. The AHC-1000A/-1000S provides power for the ECU-3000 and the
FDU-3000.
2.5.5 Loading Considerations Inputs and outputs between the AHC-1000( ), the FDU-3000 or synchro-type FDU, and
the ECU-3000 are described in the theory of operation section.
2.5.6 Cooling Considerations The AHS-1000( ) performs properly with passive cooling at ambient air temperatures up
to +70 °C (+158 °F). However, as with all electronic equipment, lower operating temperatures extend equipment life. On the
average, reducing the operating temperature by 15 to 20 °C (25 to 35 °F) doubles the Mean Time Between Failure (MTBF).
Units tightly packed on the equipment rack heat each other through radiation, convection, and sometimes by direct conduction.
If space permits, separate the units from each other to significantly improve reliability.
Even a single unit operates at a much higher temperature in still air than in moving air. Fans or some other means of moving
the air around electronic equipment are usually a worthwhile investment. If a form of ram air cooling is installed, make certain
that rainwater cannot enter and be sprayed on the equipment.
2.6 CABLING INSTRUCTIONS
The mating connectors and contacts required to install an AHS-1000( ) are listed in table 2-1. Also, table 2-2 lists the special
tools required for installation.
2.6.1 General Refer to figure 2-3 AHC-1000A Attitude Heading Computer and figure 2-4 AHC-1000S Attitude Heading
Computer for AHC mating connector pin assignments.
Interconnect cables should be prepared in accordance figure 2-5, AHS-1000A/-1000S Attitude Heading Reference System in-
terconnect diagram.
Since these interconnects are typical, variations or modifications to meet customer requirements are inevitable. Refer to para-
graph 2.5, PLANNING, for information on some of the options that can affect the interconnecting cabling.
Ensure that the aircraft battery master switch is turned off before installing any of the interconnect cabling.
Failure to do so could cause electrical arcing that might result in damage to the equipment or serious injury
to maintenance personnel.
During preparation of the interconnect cables, observe the following precautions:

• Read all notes on drawings and interconnect diagrams prior to fabricating interconnect wiring cables
• Bond and shield all parts of the aircraft electrical system, such as generator and ignition systems
• Keep the interconnect cables away from circuits carrying heavy current, pulse transmitting equipment, and other sources of
interference
• Make all external connections of the equipment through the designated connectors listed on the outline and mounting dia-
grams
1 May 2006 2-5

• For balanced connections, use twisted pair shielded wiring for minimum pickup of electrostatic and magnetic fields. Avoid
long runs of wire and keep input and output circuits separated as much as possible
• All interconnect wires and cables should be marked in accordance with the Aircraft Electronics Association Wire Marking
Standard
• Avoid excessive cable lengths, but allow sufficient slack for movement due to vibration
• After installation of the cables in the aircraft, and before installation of the equipment, check to ensure that aircraft power is
applied only to the pins specified on the interconnect diagrams and that all other wires and shields are properly terminated.
2.6.2 Connector Contact Assembly and Installation For more detailed instructions on contact crimping, contact in-
sertion, and contact extraction refer to Collins Installation Practices manual (523-0775254).
NOTE
Each connecting wire must be crimped in the contact so the crimped portion of the contact can enter the
connector shell. The crimped portion must enter the shell to provide positive locking of contact in the shell.
Contact Crimping Instructions

a. Strip approximately 3.2 mm (0.125 in) of insulation from each interconnect wire.
b. Place the contact into crimp tool (refer to table 2-2 for part number) and gently close handles until the contact is held in place
without deforming either the wire or insulation barrels.
c. Hold wire straight and insert stripped portion as far as possible into wire barrel of contact pin. Bare wire should extend
beyond the front of the wire barrel, but no more than 0.8 mm (1/32 in). Insulation should be aligned with the insulation
barrel.
d. Hold the wire in place and complete the crimp by closing the crimping tool handles until the ratchet releases.
e. Remove the crimped contact from the crimping tool.
NOTE
Be sure that the wire insulation has not been crimped into the wire barrel. The end portions of the insulation
barrel should meet after crimping to form a complete loop. The wire barrel section of the contact should be
completely closed after crimping.
Contact Insertion Instructions

a. Use insertion tool (refer to table 2-2 for part number) and insert each wired contact into the proper connector hole from the
rear and press until locked.
b. Pull gently on each wire to ensure that the pin is properly locked into the connector.
Contact Extraction Instructions
a. From the wire side of the connector, insert the extraction tool (refer to table 2-2 for part number) as far as possible into the
cavity containing the contact to be removed.
b. Holding the tool in position, pull the wire, tool, and contact free from the connector.
Table 2-1. Equipment Mounting Options.
DESCRIPTION COLLINS PART NUMBER QTY

AHC-1000( ), ECU-3000 - Mounting Ears 653-4320-002 2
Mating Connector (AHC-1000( )), MS27467T25F35S, Connector, 359-0657-110 1
circular multi-contact, bayonet coupling, with crimp removable
contacts.
Backshell, M85049/49-2-24N. 859-6604-180 1
Crimp contacts, M39029/56-348 359-0608-130 128
2-6 1 May 2006

Table 2-1. Equipment Mounting Options. - Continued
DESCRIPTION COLLINS PART NUMBER QTY

Mating Connector (ECU-3000), MS27484T10F35S, Connector, 359-0645-020 1
contacts.
Backshell, M85049/49-2-10N. 859-6604-110 1
Crimp contacts, M39029/57-354 359-0608-110 9
FDU-3000 Mounting plate (optional) 628-9778-001 1
Mating Connector (FDU-3000), MS27472P10C35S, Connector, 859-0007-010 1
contacts. Alternate: MS27499E10C35S, MS27513E10C35S,
MS27497(E, P or T)10C35S, MS27508E10C35S, MS27474(E, P
or T)10C35S.
Crimp contacts, M39029/57-354 359-0608-110 13
Table 2-2. Mating Connector Contacts and Special Tools.
CONTACT CONTACT COLLINS PART CRIMP TOOL LOCATOR INSER-

DESCRIPTION COLOR CODE NUMBER TION/EXTRAC-
TION TOOL
Crimp Socket 22D Orange-Green- 359-0608-110 359-8102-010 359-8102-060 359-8032-010
Yellow M22520/2-01 M22520/2-06 M81969/14-01
Crimp Socket 22D Orange-Yellow- 359-0608-130 359-8102-010 359-8102-070 359-8032-010
Gray M22520/2-01 M22520/2-07 M81969/14-01
2.7 INSTALLATION PROCEDURES
Ensure that the aircraft battery master switch is turned off before installing any equipment, mounts, or inter-
connect cables. Failure to do so could cause electrical arcing that might result in damage to the equipment
or serious injury to maintenance personnel.
The following paragraphs provide instructions for installing the AHS-1000( ). If other associated equipment is to be installed,
refer to the applicable equipment manual for installation procedures. A precise alignment of the AHC-1000( ) mounting surface
is required for the AHS-1000( ) to provide accurate attitude information.
2.7.1 AHC-1000( ) and Mounting Ears Installation The AHC-1000( ) is normally mounted, with mounting ears, in
front of the center of gravity of the aircraft. The mount location must be in a stable, horizontal, low vibration area. The mounting
ears should be attached to the primary aircraft structure at floor level; however, lower avionics rack mounting is acceptable,
provided the rack is rigid and will not have motion that is independent of the primary aircraft structure.
A precise alignment of the AHC-1000( ) mounting surface is required for the AHS-1000( ) to provide accurate attitude infor-
mation. It can be achieved by shimming the AHC-1000( ) to a tight tolerance with respect to the aircraft level surface.
Another option is to use the AHC-1000( ) leveling function. Using this function, after the aircraft is leveled, the AHC-1000( ) can
be switched into the Unit Leveling Mode and the system will be capable of computing the values of attitude offset between the
AHC-1000( ) mounting plane and the aircraft level plane. These offset values will be stored in the ECU-3000. The AHC-1000( )
1 May 2006 2-7

then reads these offset values during the initialization process and compensates the computed attitude accordingly during normal
operation. The maximum misalignment the automatic leveling function can compensate for is three degrees in the pitch and roll
axes. Therefore some shimming may still be necessary to coarsely level the installed unit.
In order to insure accuracy of the AHS-1000( ) outputs, the following mounting tolerances must be followed:
• The longitudinal axis of the installed AHC–1000( ) must be aligned within 0.50 degree of the aircraft longitudinal axis
• For installations not using the Unit Leveling function, the installed AHC–1000( ) must be leveled within 0.10 degree of the
aircraft level axes
• For installations using the Unit Leveling function, the installed AHC-1000( ) must be leveled within 3.0 degrees of the aircraft
axes.
Refer to table 2-1 for specific mount, mating connector and contact information. Refer to figure 2-6 (AHC-1000A) and figure
2-7(AHC-1000S) for outline and mounting diagrams.
2.7.1.1 Unit Leveling Mode
NOTE
Perform steps “e” and “f” immediately after step “d” to minimize the length of time that power is removed
from the AHC-1000( ) so the unit remains thermally stable.
While in the Unit Level Mode, the following unit leveling procedure should be followed for the AHS-1000( ) to compute the
unit leveling compensation data.
a. Verify the DG/Slave switch is set to Slave, power-up the AHC-1000( ), and confirm the attitude outputs are valid. The
AHC-1000( ) must be thermally stable prior to beginning the unit leveling procedure. Allow a 60-minute warm-up period
when powering up from ambient temperature.
b. Level aircraft within 0.0 ±0.1 deg of actual level reference.
c. The leveling procedure requires an “On-Ground” condition. If needed, override the aircraft Weight-On-Wheels (strut) switch
to indicate “On-Ground”.
d. After the unit is thermally stable, remove all power (both primary and battery) to the AHC-1000( ).
e. Set the Unit Leveling Mode switch to the ON or Unit LEVELING MODE ENABLE position.
f. Apply power to the AHC-1000( ). After power-up tests complete, the AHC-1000( ) will enter unit leveling mode.
g. While the AHC-1000( ) is calculating leveling parameters, the pitch, roll and heading data outputs will alternate between
invalid and valid at a 1 Hz rate and the heading will begin decrementing from 360 degrees over a five minute period.
h. If leveling parameters are within acceptable limits (±3 degrees) at the end of the leveling parameter calculation, the attitude
and heading outputs will discontinue alternating between invalid and valid indications and will remain in the invalid state
and the valid state, respectively.
i. Toggle the DG/Slave switch from Slave to DG back to Slave to save leveling parameters in the ECU-3000. If the leveling
parameters are within acceptable limits, go to step k. The heading output will transition to invalid indicating that unit leveling
data has been written to the ECU-3000.
j. If leveling parameters are outside acceptable limits, the attitude and heading outputs will continue to alternate between invalid
and valid at a 1 Hz rate at the end of the five minute calculation period. The leveling parameters in the ECU-3000 will not
be updated. The failure cause should be corrected and the unit leveling procedure repeated.
k. Switch the Unit Leveling Mode switch to the OFF position to exit unit leveling mode.
l. Perform a post-alignment leveling check to verify that the attitude is within 0.0 ±0.2 degrees. Allow the unit to stabilize for
5 minutes prior to verifying the leveling accuracy.
2.7.1.2 Exiting Unit Leveling Mode The Unit Leveling Mode can be aborted at any time during this mode by removing
all power (both primary and battery) to the AHC-1000( ) or by setting the Unit Leveling Mode Select discrete to disabled
(open=disabled). Setting the Unit Leveling Mode Select discrete to disabled position causes the AHC-1000( ) to automatically
reinitialize upon exiting Unit Leveling Mode.
2-8 1 May 2006

2.7.1.3 Unit Leveling Using Leveling Fixture The leveling fixture consists of a rigid, precision-machined block with
engagement surfaces corresponding to an AHC-1000( ). It is placed on the flat surface where the AHC-1000( ) is to be installed.
The fixture contains two perpendicular bubble levels and longitudinal/lateral milled vertical surfaces for line-of-flight calibra-
tion. Clearance holes have been provided in the fixture to allow tightening of mounting screws with the leveling fixture in place
in order to monitor any changes in leveling during the tightening process.
Use Shim Kit, CPN 653-2927-001, to shim the AHC-1000( ). The shim kit consists of 13 shims of various thickness. The shim
sizes and corresponding part numbers are in table 2-3.
Table 2-3. Shim Kit Parts List.
DESCRIPTION COLLINS PART NUMBER QUANTITY

Shim, .001 thick 653-2928-001 5
Shim, .003 thick 653-2928-002 2
Shim, .005 thick 653-2928-003 2
Shim, .010 thick 653-2928-004 2
Shim, .015 thick 653-2928-005 2
It is important to make sure that after shimming the unit (prior to tightening screws) that there is no slack between the unit and
the surface in all corners. No rocking motion that could lead to distortion of the unit upon tightening the screws should exist on
either axis.
Before the AHC-1000( ) is tightened down, perform the following orientation test procedure.
This orientation test procedure is critical to ensure the AHS-1000 provides accurate information to the pilot.
a. Tilt the AHC-1000( ) to simulate a right bank. Verify the ADI horizon rotates ccw.
b. Tilt the AHC-1000( ) to simulate a left bank. Verify the ADI horizon rotates cw.
c. Tilt the AHC-1000( ) to simulate a pitch-down attitude. Verify the ADI horizon moves up.
d. Tilt the AHC-1000( ) to simulate a pitch-up attitude. Verify the ADI horizon moves down.
NOTE
If incorrect results are obtained, verify the integrity of the orientation strapping.
Observe the fixture bubbles while tightening the screws. Any large change of bubble centering could indicate a possible unit
distortion during the tightening procedure.
a. Verify all interconnect wiring before proceeding. Make sure 28 V dc input power is applied only to pins J1-14 and J1-23.
b. Verify alignment of the unit is within design parameters.
c. Attach wire harness mating connector to front connector of unit. Verify proper connector engagement by observing indicators
on connector.
d. Ensure that a good electrical bond exists between the unit and the aircraft.
1 May 2006 2-9

Figure 2-3. AHC-1000A Mating Connector Pin Assignments
2-10 1 May 2006

Figure 2-4. AHC-1000S Mating Connector Pin Assignments
1 May 2006 2-11

2.7.2 FDU-3000 Flux Detector Unit The FDU-3000 must be mounted as far as possible (minimum of 610 mm (2 ft))
from any magnetic materials and cables carrying direct current. The FDU must be mounted within three degrees of the aircraft
longitudinal axis. The mounting surface should be perpendicular within one degree of the aircraft level axes. Prepare the
mounting surface in accordance with the outline and mounting diagram, figure 2-8. Secure the FDU-3000 mounting plate,
628-9778-001, to the aircraft and the FDU to the mounting plate using non-ferrous hardware. The FDU-3000 mounting plate
provides alignment pins to ensure that, if the FDU is replaced, no index error adjustment is required. Installations not using the
FDU-3000 mounting plate must secure the FDU directly to an aircraft structure in the manner stated above. Connect the aircraft
wiring harness to the FDU-3000 pendant cable. Refer to table 2-1 for specific mating connector and contact information. Refer
to figure 2-9 for the FDU-3000 connector pin assignments.
2.7.3 ECU-3000 External Compensation Unit The ECU-3000 should be located within 5 feet of the AHC-1000( ). The
ECU-3000 is designed to stay with the aircraft during an AHC-1000( ) removal. The ECU-3000 is designed to be secured to
a vertical surface of the aircraft frame. Connect the system interconnect cable to P1. See the ECU-3000 outline and mounting
diagram figure 2-10 for further instructions. Refer to table 2-1 for specific mating connector and contact information. Refer to
figure 2-11 for the ECU-3000 connector pin assignments.
2.7.4 Synchro-Type Flux Detector Unit The synchro-type FDU is a customer supplied item. For installation, refer to
the application manual that was supplied with the unit.
2.8 TESTING
Testing should be done before and after installation.
2.8.1 Preinstallation Testing To verify proper operation before installing the equipment in an aircraft it is recommended
to connect the unit to a system mock up.
2.8.2 Orientation Programming and Postinstallation Test Strapping in the AHS-1000( ) wiring harness configures
the AHC-1000( ) for either left (port), right (star-board), fore, or aft facing mounting. This must be done so that the AHC-1000( )
can correctly interpret airplane motion as pitch or roll and with the correct polarity. The AHC-1000( ) determines its orientation
using the orientation strap information each time power is applied.
The postinstallation test provides an operational check which is crucial to flight safety of the AHS-1000( ) and ensures that
orientation strapping of the units in the system are correct. This test should be performed after the interconnect cables have
been installed and verified, and before the AHC-1000( ) and FDU-3000 or synchro-type FDU are permanently installed in the
aircraft. An HSI and ADI or equivalent (eg, EFIS) must be connected to monitor the output of the system. Refer to table 2-4
for the postinstallation test procedure.
Table 2-4. Postinstallation Test Procedure.
STEP PROCEDURE DESIRED RESULTS

1.0 Connect all units to the system interconnect Securely screw the AHC-1000( ) to the mounting ears.
cables and position them in their normal
mounting position.
1.1 Slaved/ DG switch to Slaved. Verify the Slaved/DG mode input = Slaved.
2-12 1 May 2006

Table 2-4. Postinstallation Test Procedure. - Continued

2.0 Close circuit breakers from +28 VDC and The AHC-1000( ) initialization time is dependent upon the
Battery supplies to apply power to the Source ID strapping. The compass cards make one complete
AHS-1000( ) system and the HSI and ADI. rotation (from north to north) during an initialization cycle. If
initialization parameters are not met additional initiation cycles
will occur. Verify the attitude and heading flags go out of view
and the HSI slews to the general aircraft magnetic heading.
Source ID Strapping Approx Initialization Time
Unit # One (01) 35 seconds
Unit # Two (10) 45 seconds
Unit # Three (11) 40 seconds
Unit # Four (00) 50 seconds
3.0 Open the AHC-1000( ) +28 V dc primary Verify the AHC-1000( ) continues to operate.
circuit breaker.
3.1 Close the AHC-1000( ) +28 V dc primary
circuit breaker.
4.0 DG/Slaved operation
4.1 Put the DG/Slaved mode switch in the DG Verify the compass card rotates cw (heading decreases).
position and push the Right Slew pushbut-
ton.
4.2 Return the DG/Slaved mode switch to the Verify the compass card quickly rotates back to the original head-
Slaved position. ing.
4.3 Put the DG/Slaved mode switch in the DG Verify the compass card rotates ccw (heading increases).
position and push the Left Slew pushbutton.
4.4 Return the DG/Slaved mode switch to the
Slaved position.
End Postinstallation Test Procedure
If the above test is completed satisfactorily, remove power and secure all system components in the aircraft, and then perform
the FDU compensation mode procedure.
2.8.3 FDU Compensation Mode Procedure The following alignment procedure must be performed after installation of
the equipment in the aircraft to ensure system accuracy. The postinstallation test given in table 2-4 should be performed before
alignment to ensure that the system is operational and connected properly.
The FDU Compensation Mode of operation is intended to collect FDU-3000 or synchro-type FDU data and calculate the com-
pensation coefficients during the FDU compensation procedure. The compensation coefficients are used to compensate for the
single cycle (Sin/Cos) error and index error of the installed FDU magnetic sensor. The computed compensation coefficients are
stored in the ECU-3000. The next step is the index adjustment that compensates for alignment error of the FDU-3000 or the
synchro-type FDU with respect to the longitudinal axis of the aircraft. Refer to table 2-5 for the compensation mode procedure.
2.8.3.1 Prealignment Procedure Before aligning the AHS-1000( ), follow this procedure:
a. Ensure that all equipment, cover panels, and hardware near the flux detector are secured in their normal flight positions.
Remove all nonflight equipment from the aircraft.
1 May 2006 2-13

b. Lock the flight controls with the flight compartment lock. Do not use external locks.
c. Remove all magnetic items from personnel involved with alignment of the system.
d. Ensure that the weather is suitable for alignment (adequate light for aircraft positioning at the compass base and less than 15
knots windspeed) and taxi or tow the aircraft to the compass rose.
Table 2-5. FDU Compensation Mode Procedure.

1.0 Setup
1.1 Power up the AHS-1000( ). Verify the ATT and HDG are valid.
1.2 Taxi the aircraft to a compass rose, or an area known to be
free of magnetic interference.
1.3 Position aircraft toward North heading and apply brakes. Aircraft heading to 0±2 degree.
NOTE
The aircraft must be stationary during these calcula-
tions.
1.4 Remove all power from the AHS-1000( ). Both primary and battery power removed.
1.5 Set the FDU Compensation Mode switch to ON or Com- Apply ground to P1-117 throughout the FDU
pensation Mode position. Compensation Mode Procedure.
2.0 Procedure
2.1 Apply power to AHS-1000( ). After power-up test is complete, the AHC-
1000( ) will enter FDU compensation mode.
2.2 FDU compensation mode The ATT is flagged and HDG is valid.
2.3 Toggle the DG/Slaved switch from Slaved to DG, and back The HDG flag appears on all displays for at
to Slaved. least 25 seconds, but no longer than 35 sec-
onds.
2.4 Reposition the aircraft in a clockwise direction to the next Aircraft centered on 45 degree radial.
45 degree step.
NOTE
Although the procedure is designed to work with
45±5 degree steps, a more accurate result will be
achieved if the steps are kept to 45±2 degrees.
2.5 Toggle the DG/Slaved switch from Slaved to DG, and back The HDG flag appears on all displays for at
to Slaved. least 25 seconds, but no longer than 35 sec-
onds.
2.6 Repeat steps 2.4 and 2.5 until all eight 45-degree alignment The last step occurs when the aircraft is posi-
steps have been completed. tioned at the 315 degree heading mark.
2-14 1 May 2006

Table 2-5. FDU Compensation Mode Procedure. - Continued

2.7 Upon completion of this step, a sine/cosine compensation
calculation will be performed using the information col-
lected at each step. If the sine/cosine compensation is
within correctable limits (7500 nano−tesla) and the FDU
Compensation Mode switch is in the ON or COMPENSA-
TION MODE position (P1-117 grounded), the HDG will
become valid. If the sine/cosine compensation is outside
correctable limits the HDG flag will remain in view to indi-
cate an out-of-limits condition. If the compensation proce-
dure cannot succeed because one or more of the 45 degrees
steps exceeded the +/5 degree tolerance, the HDG flag will
remain in view. The cause of the out-of-limits condition
should be corrected and the compass compensation proce-
dure repeated.
3.0 Index Adjustment (If not initial installation and the FDU-3000
index pin is used, go to step 3.5)
3.1 Align the aircraft to any known heading as accurately as Accurate position heading and stationary air-
possible and apply the aircraft brakes to keep it stationary. craft.
NOTE
Any misalignment will be directly translated into a
heading error during operation.
3.2 Momentarily activate either slew switch to initiate the in- The HDG flag will appear for at least 25 sec-
dex adjustment procedure. onds, but not longer than 35 seconds, while the
AHC-1000( ) performs a heading alignment
calculation. The HDG becomes valid upon
completion of the calculation.
3.3 Use the heading slew switches to slew the heading left or Corrected to the actual heading. If the dis-
right until the displayed heading agrees with the heading played heading cannot be adjusted to the ac-
the aircraft has been aligned to. It is possible to display tual heading, the index error is outside cor-
the heading to the nearest 0.1 degree by using the FCS rectable limits (corrections > ±3 degrees are
diagnostic display. not allowed) and the FDU compass compen-
sation procedure should be aborted.
3.4 Once the correct heading is obtained, toggle the DG/Slaved Store the index correction.
switch from Slaved to DG then back to Slaved.
NOTE
If the DG mode had been selected, toggle from DG
to Slaved to DG and back to Slaved.
3.5 Set the FDU Compensation switch to OFF (remove the To exit the FDU Compensation mode and
ground from P1-117). restart in the normal AHRS mode.
1 May 2006 2-15

Table 2-5. FDU Compensation Mode Procedure. - Continued

3.6 Perform a check swing to verify heading alignment accu- The heading deviation should not exceed ±2
racy. degrees on any heading. For dual installa-
tions the heading difference between the two
NOTE
systems should not exceed ±2 degrees on any
After positioning the aircraft at each heading “fast heading.
slave” the heading to the FDU by switching the
DG/Slaved switch from Slaved to DG and back to
Slaved.
3.7 End FDU Mode Compensation Procedure.
NOTE
The FDU Compensation Mode can be aborted at any time during this mode by removing all power (both primary and
battery) to the AHC-1000( ).
If the check swing is not successful, confirm that the area in which the aircraft was swung is indeed free of magnetic materials
that influence the earth’s magnetic field. A simple hand held magnetic compass may be used to survey the area for magnetic
influence. If any areas of influence are found, repeat the procedure in a clean area.
Another potential cause of inaccurate heading readings during the check swing is magnetic influence near the flux detector in
the aircraft. Magnetic influence may be caused by magnetically charged items or materials installed near the FDU. Magnetic
influence may also be present due to a magnetic field generated by DC current running through wires that are routed near the
FDU. Check the area for these types of effects. A simple hand held magnetic compass may be used to check for magnetized
materials. DC current effects may be checked for by turning aircraft equipment on in a systematic manner while monitoring the
heading display for large changes in heading readout. If any of these influences are present, eliminate or reduce them and repeat
the FDU compensation procedure. If no magnetic influence is found at the site or near the FDU, another possible corrective
action is to perform the procedure again paying close attention to hitting the 45 degree steps as accurately as possible.
2-16 1 May 2006

Figure 2-5. AHS-1000A and AHS-1000S Attitude Heading Reference System Interconnect Diagram (Sheet 1 of 4)
1 May 2006 2-17/(2-18 Blank)

1 May 2006 2-19/(2-20 Blank)

1 May 2006 2-21/(2-22 Blank)

1 May 2006 2-23/(2-24 Blank)

.
Figure 2-6. AHC-1000A Attitude Heading Computer, Outline and Mounting Diagram
1 May 2006 2-25/(2-26 Blank)

.
Figure 2-7. AHC-1000S Attitude Heading Computer, Outline and Mounting Diagram
1 May 2006 2-27/(2-28 Blank)

.
Figure 2-8. FDU-3000 Flux Detector Unit, Outline and Mounting Diagram (Sheet 1 of 2)
1 May 2006 2-29/(2-30 Blank)

Figure 2-8. FDU-3000 Flux Detector Unit, Outline and Mounting Diagram (Sheet 2 of 2)
1 May 2006 2-31/(2-32 Blank)

.
Figure 2-9. FDU-3000 Connector Pin Assignments
1 May 2006 2-33/(2-34 Blank)

Figure 2-10. ECU-3000 External Compensation Unit, Outline and Mounting Diagram
1 May 2006 2-35/(2-36 Blank)

.
Figure 2-11. ECU-3000 Connector Pin Assignments
1 May 2006 2-37/(2-38 Blank)

523-0806057
CHAPTER 3
Operation
3.1 GENERAL
The AHS-1000( ) Attitude Heading Reference System is used to provide measurements of the aircraft pitch, roll, and Euler
angles for use by cockpit displays, flight control and management systems, and other avionics equipment. High quality body
rate, Euler rate and linear acceleration outputs are provided for enhanced flight control system performance. Operation of the
AHS-1000( ) system is automatic when power is applied to the system. Proper operation is indicated when the compass card on
the associated HSI or RMI slews to the magnetic heading of the aircraft, the horizon on the associated ADI moves to indicate
the aircraft pitch/roll attitude, and associated flags go out of view.
3.2 CONTROLS AND DISPLAYS
The only operating controls for the AHS-1000( ) system are external switches which are used to select the directional gyro mode
and slew pushbuttons.
3.2.1 DG MODE (Directional Gyro) Switch

NOTE
The AHC-1000( ) is intended to operate in slaved mode only in regions where other slaved magnetic com-
pass systems operate. The DG Mode is available for brief operation near magnetic anomalies. DG Mode is
not intended for use as a long-term heading reference.
The AHS-1000( ) provides two modes of Heading Function operation: Magnetic Heading (Slaved) Mode and Directional Gyro
(DG or Free Gyro) Mode. The DG MODE switch is used to select either the Slaved Mode or the DG Mode. In the Slaved Mode
the heading computations in the AHC-1000( ) are slaved to the FDU-3000 or synchro-type flux detector unit (FDU). This is the
primary heading mode during normal operation. In the DG (Directional Gyro) Free Gyro Mode the input from the FDU-3000 or
synchro-type FDU is not used to slave the heading of the AHC. The AHC performs like a directional gyro in this mode. When
switching from DG Mode to Slaved Mode, the AHC-1000( ) fast slaves to the magnetic heading sensed by the FDU-3000 or
synchro-type FDU. Momentarily selecting then deselecting DG Mode prior to takeoff corrects any heading splits between the
two compass cards.
3.2.2 SLEW Pushbuttons These momentary action buttons are operational in Slaved and/or DG Mode depending upon
the wiring configuration. When operating in the DG Mode, the slew buttons are used to periodically correct for drift, right
or left. Pushing either Slew button causes the heading computations in the AHC-1000( ) (and the heading displayed on the
compass card) to slew toward the selected direction. Pushing either slew button when operating in the slaved mode also causes
the heading computations to slew in the selected direction; however, when the button is released the heading will slowly slave
back to the heading sensed by the FDU-3000 or synchro-type FDU. The slew buttons will cause an increase or decrease in the
heading at one degree per second for the first two seconds, then at five degrees per second if the switch remains engaged.
3.3 OPERATING PROCEDURES
3.3.1 AHC-1000( ) Operational Data This paragraph contains operation-related information that may be useful to a
ground maintenance crew.
• Backup Power: The battery backup allows normal system operation during primary power outages. The duration of AHC-
1000( ) operation using backup power is dependent on the battery timeout value setting. The default value is 10 minutes.
• Time-To-Valid Flags: After initial turn on, the attitude and heading flags should switch to a valid (out-of-view) indication in
35 to 50 seconds. In DG Mode, initialization time is approximately 4 1/2 minutes and is not recommended.
• Annunciators: Included are the following annunciators; initialization, basic mode, attitude validity, heading #1 validity, and
heading #2 validity.
3.3.2 Typical Operation of the AHS-1000( ) Attitude Heading Reference System Operation of the AHS-1000( )
is automatic when power is applied to the system and the initialization procedures have been completed. Upon successful
completion of a power-up test, the AHC transitions to the AHRS mode. This is the normal operating mode. Proper operation
is indicated when the compass card on the associated navigation display (ND and/or RMI/HSI) slews to the correct magnetic
heading, the attitude display on the associated primary flight display (PFD or ADI) moves to indicate the pitch and roll attitude,
and the associated ATT and HDG flags go out of view.
4 February 2003 3-1

operation 523-0806057
The normal procedure is to initialize the system on the ground before or after engine start-up with DG MODE not selected
(initialization time with DG MODE selected can take up to 4 1/2 minutes) and with the parking brake set so that no significant
movement of the aircraft is possible. It is also recommended that operation of flaps, nosewheel steering, or changes in the engine
power setting do not occur until the initialization is complete. An initialization cycle takes approximately 35 to 50 seconds.
During the AHRS mode initialization/alignment, the AHC performs an initialization test, an LRU configuration function, and
initial alignment function. If there are faults detected during the initialization, the AHC will determine if the faults are critical or
not. Critical faults are defined as faults that cause the AHC to fail the performance requirements or compromise data integrity.
If the fault is determined to be critical, the unit will reset. If the fault is not critical the LRU will continue operation.
As the initialization period starts, the HSI and RMI compass cards indicate north and begin counting down to 0 degree by
rotating clockwise and the (optional) installed initialization annunciator flashes. This action tells the pilot that initialization is
in process and how much time remains until it is completed (it takes 35 to 50 seconds for one revolution, or one cycle). If the
aircraft is moved during initialization, the initialization may not complete successfully and may begin a new initialization cycle.
During this period, the ATT and HDG flags will be in view but will clear after a successful initialization.
If the aircraft is airborne, cycling both primary and battery power to the AHC-1000( ) computer causes the computer to reini-
tialize. While airborne initialization is in process, the aircraft should maintain a straight and level flight with no acceleration
changes for the 35 to 50 second initialization.
Various monitors have been included in the AHC-1000( ) to check for bad initializations. However, it is the responsibility of
the pilot to ensure that a successful initialization occurs as evidenced by the ATT and HDG flags being in view for 35 to 50
seconds and then clearing during a period when the airplane is motionless. If there is any doubt, the pilot should cycle both the
AHC-1000( ) primary dc circuit breaker and the battery backup switch and observe a successful initialization.
After the system is initialized, as indicated by the ATT and HDG flags being out of view and the presentation of valid attitude
and heading information, the airplane may be taxied.
NOTE
Prior to takeoff, if the two headings disagree but are not slewing away from the airplane heading, momen-
tarily select then deselect DG MODE (or optional FAST/SLAVE switch). This allows the headings to align
quickly with the magnetic heading sensed by the FDU-3000 or synchro-type FDU.
While in AHRS mode, the AHC performs the core AHRS functions that include the IMU sensor processing and attitude/heading
determination. After processing the measured inertial data, input air data, and flux detector data (if available), the AHC will
provide attitude, heading, rate, and acceleration information. The AHC also provides fault detection and reporting.
3-2 4 February 2003

523-0806057
CHAPTER 4
THEORY OF OPERATION
4.1 INTRODUCTION
This section provides overall system theory and functional block diagram theory for each unit in the Collins® AHS-1000( )
Attitude Heading Reference System.
The overall system theory is in a paragraph called overview, which introduces the general principles involved in the AHS-
1000( ).
Functional block diagram theory briefly describes all inputs and outputs of each unit, along with signal flow information.
4.2 OVERVIEW
This paragraph is intended as a brief introduction to the general principles involved in the AHS-1000( ). It is written for those
who have little or no previous contact with this type of airborne equipment. The treatment here is by no means exhaustive and
the reader is invited to consult other sources for additional information. In the remainder of this paragraph, those terms which
are often used in connection with the Attitude Heading Reference System are underlined so the reader can build a vocabulary
common to Attitude Heading Reference System.
4.2.1 Installation Configurations The AHS-1000( ) is a solid-state strap-down attitude/heading reference system that
uses quartz-based inertial sensor technology. The primary function of the AHS-1000( ) system is to provide measurements of
the aircraft pitch, roll and heading Euler angles for use by cockpit displays, flight control and management systems, and other
avionics equipment. Also, high quality body rate, Euler rate and linear acceleration outputs are provided for enhanced flight
control system performance.
A typical dual system installation is shown in figure 4-1 (AHS-1000A) and figure 4-2 (AHS-1000S). The basic components and
signals of the system are illustrated in figure 4-3 (AHS-1000A) and figure 4-4 (AHS-1000S). The AHS-1000( ) system consists
of the AHC-1000( ) Attitude Heading Computer, FDU-3000 Flux Detector Unit (AHS-1000A), and the ECU-3000 External
Compensation Unit (ECU). A 5-wire synchro-type Flux Detector Unit (FDU) is used in the AHS-1000S system.
The AHC-1000( ) internally measures angular rates and linear accelerations about the body axis of the aircraft. The AHC-
1000( ) processes this data to obtain digital 3-axis angle, rate and acceleration information. Input sources include primary and
battery power sources, strut switch logic, orientation straps, mode select logic, slew command logic and source ID straps. The
AHC-1000( ) uses magnetic heading information from the Flux Detector Unit, and flux detector compensation data from the
External Compensation Unit to compute attitude, heading, rotational rate and acceleration information. The AHC-1000A and
AHC-1000S also convert the data to synchro and analog outputs. The AHC-1000( ) monitors and reports on the operation of
the AHS-1000( ) system. The AHC-1000( ) is the single computing source of the AHS-1000( ) system.
The FDU-3000 Flux Detector Unit is a gimbaled, 2-axis, magnetic sensor that detects the horizontal component of the earth’s
magnetic field. The AHC-1000A applies a 3000-Hz triangle signal to the primary windings of both coils in the FDU-3000. This
excitation signal drives the core material into saturation in alternating opposite directions. The secondary winding of each coil
senses the transition into saturation. The presence of an external magnetic field causes the core to remain in saturation longer
in the direction of the external field and shorter in the direction opposite the external field. Electronics within the AHC-1000( )
process this signal and generate a dc voltage to rebalance the flux pattern of the core. This rebalancing signal is proportional
to either the sine or cosine of the magnetic heading. The FDU, along with its compensation data, provides an accurate heading
reference. The derived magnetic heading information is used to slave the computed heading angle in the AHC-1000( ). The
FDU-3000 is an analog device and does not contain software, memory or processing capability.
The synchro-type FDU is a customer supplied item. Basic operation is similar to the FDU-3000, except that the AHC-1000S
supplies a 400-Hz square wave excitation signal to the primary winding coil in the FDU. Three secondary windings that are
each separated by 120 degrees drive the core material to saturation. For specific signal descriptions and operational theory, refer
to the manual supplied with the FDU model that is installed in the aircraft.
The ECU-3000, External Compensation Unit, is used to store aircraft specific compensation and configuration data. The ECU
contains flux detector compensation values, battery timeout values, and unit leveling compensation values. The ECU is designed
to stay with the aircraft during replacement of the AHC-1000( ).
Precise alignment of the AHC-1000( ) mounting surface is required for the AHS-1000( ) to provide accurate attitude information.
This is accomplished through accurate alignment and shimming of the AHC-1000( ) during installation.
1 May 2006 4-1

theory of operation 523-0806057
4.3 FUNCTIONAL THEORY

The AHC-1000( ) is the heart of the AHS-1000( ) Attitude Heading Reference System. All processing takes place in the Atti-
tude/Heading Computer. Ancillary inputs from the flux detector unit and external compensation unit combine with the sensed
rate and acceleration data in the Attitude Heading Reference System (AHRS) program to provide the attitude and heading in-
formation for the aircraft attitude and directional instrumentation.
4.3.1 Power Source Management The AHC-1000( ) is designed to operate from a primary input source with a nominal
voltage of 27.5 V dc and a backup battery source for operation during short term power outages of the primary source. The
AHC-1000( ) will power up when the primary bus is powered above an 19.0 V dc level. The battery input will be enabled after
the unit powers up and when the primary power level is below 18 V dc. The battery input will be disabled when primary power
is restored or after the timeout period passes (as set in the ECU-3000). The default timeout period is 10 minutes. If the battery
input is enabled, the power supply card, A1, converts the 28 V dc input power to +5, -5, +8 and -8 V dc for circuit operation.
The AHC-1000( ) provides power for the ECU-3000 and the FDU-3000 or synchro-type FDU functions.
4-2 1 May 2006

Figure 4-1. Typical AHS-1000A Attitude Heading Reference System Block Diagram
1 May 2006 4-3

Figure 4-2. Typical AHS-1000S Attitude Heading Reference System Block Diagram
4-4 1 May 2006

4.3.2 Initialization Initialization starts immediately after primary power is applied to the AHC-1000( ). A power up test
takes about 5 seconds to verify the AHC-1000( ) is capable of performing the basic functions of the operating mode. If the LRU
detects faults during the power up test, it will initiate reset. Upon successful completion of the power up test the AHC-1000( )
is capable of operating in the AHRS mode and the FDU Compensation Mode. The FDU Compensation Mode of operation is
covered in the installation section. The normal AHRS mode is covered here.
After power is applied, the AHC-1000( ) sets the attitude and heading invalid bits causing both HDG and ATT flags to be
activated. During initialization, the AHC-1000( ) decrements the heading value from a North heading until the North heading
is reached again at the end of initialization. This causes the compass card on the associated navigation display rotate to north,
pause, and then slowly rotate clockwise ending back at north after the process is complete. This indicates that initialization is
in process and approximately how much time remains until complete. The (optional) installed initialization annunciator flashes
during the alignment procedure. The unit reads the discrete strapping inputs to determine Slaved or DG mode, on-ground or
in-air status, source ID, and box orientation. The unit also reads the External Compensation Unit data to determine the FDU
compensation and configuration. The AHC-1000( ) checks for the proper software and hardware configuration and aligns the
Inertial Measurement Unit.
During the initial alignment procedure, the AHC-1000( ) monitors the external influences that might disturb the alignment
accuracy. Detection of aircraft motion (linear or angular) in excess of normal cargo loading and wind buffeting may cause
restart of the initialization process. The front panel LEDs cycle through three colors (green, amber, red).
After the compass card rotates back to north, heading slews to the correct aircraft heading. The initialization should take approx-
imately 35 to 50 seconds. The aircraft must remain level and must not accelerate during air-borne initialization. If DG-mode is
selected, initialization will take up to 5 minutes to complete.
1 May 2006 4-5

Figure 4-3. AHC-1000A System Components and Signals
4-6 1 May 2006

Figure 4-4. AHC-1000S System Components and Signals
4.3.3 AHRS Mode Operation
The AHC-1000( ) has been designed to exhibit a very high degree of functional integrity. Nevertheless,
the user must recognize that it is not practical to provide monitoring for all conceivable failures and that,
however unlikely, it is possible that erroneous operation could occur without a fault indication. It is the re-
sponsibility of the pilot to detect such an occurrence by means of cross-checks with redundant or correlated
information available in the cockpit.
The AHC-1000( ) performs the core attitude/heading and reference functions in the AHRS mode of operation. The Inertial
Measurement Unit (IMU) of the AHC-1000( ) provides the processor with 3-axis body angular rates of pitch, roll and yaw, and
3-axis body longitudinal, lateral and normal accelerations.
The IMU uses three quartz rate sensors and three vibrating quartz accelerometers to mimic the actions of directional and vertical
gyros. Rotation sensors measure rotation rates in X, Y and Z axes and apply them to the processor where a Direction Cosine
Matrix is developed to retain the attitude/heading information. The inertial rates alone are acceptable only during a short interval.
Without compensation, the attitude/heading error which is an integration of the inertial rate error will grow unbounded over
time. The magnetic heading information obtained from the flux detector performs a similar function for the long term heading
reference. This is referred to as the heading slaving function. The AHC-1000( ) performs the proper attitude and heading slaving
functions including feedback gains and cutouts under various flight patterns to meet the attitude and heading requirements for
the general aviation and commuter market.
1 May 2006 4-7

The AHC-1000( ) provides one mode of attitude function operation: Basic mode. Similar to the operation of a conventional
vertical gyro erection system, in this Basic mode the measured inertial accelerations are used to establish the long-term attitude
reference. The slaving to the long-term attitude reference is cut out adequately to avoid the error caused by the aircraft maneu-
vering. Errors are expected due to erroneous leveling when operating just under cutout points or due to gyro drift rates when
operating above cutout points.
The AHC-1000( ) provides two modes of heading function operation: Magnetic Heading (Slaved) mode and Directional Gyro
(DG or Free Gyro) mode. If the DG mode discrete input is open, the LRU will transition into the Magnetic Heading (Slaved)
mode. If 28 V dc is applied to the DG Mode discrete, the LRU will transition to the DG Mode.
The Magnetic Heading mode is the primary heading mode during normal operation. Magnetic heading data is obtained from
the flux detector unit to slave the computed heading angle. The AHC-1000( ) provides a 3000 Hz triangle excitation signal to
the primary windings of the SIN and COS coils in the FDU-3000 through the SIN and COS Excitation pins. This excitation
signal alternately drives the sine and cosine coil core material into saturation in opposite directions. Secondary windings of each
coil sense the transition into saturation and in conjunction with external magnetic fields develop a different waveform in the
secondary winding. The AHC-1000( ) processes the signal received from the FDU SIN and COS Signal output to estimate the
magnetic field sensed by the windings. The AHC-1000( ) will monitor the magnitude of the sensed magnetic fields when the
roll angle is between ±5°. When the Magnetic Heading mode is selected from the DG mode, the slaved heading is immediately
stepped into agreement with the FDU heading. In installations without the DG mode it may be desirable to immediately correct
heading errors through a fast slave control. This can be provided by connecting the DG/Slave mode line to a momentary switch
in the cockpit.
The DG mode may be selected manually in areas where the magnetic field measurements are inconsistent, noisy, etc. While in
the DG mode the AHC-1000( ) will not slave the heading to the FDU, but instead performs like a directional gyro.
A Heading Slew function allows the pilot to rotate the heading at predetermined rates. Slew switches (left and right) when
asserted (asserted = 28 V dc) will cause the AHC-1000( ) to decrease or increase the heading. The heading changes at 1°/sec
±0.5°/sec for the first 2 seconds. If the switch remains engaged for longer than 2 seconds, the heading change rate will increase
to 5°/sec ±1°/sec.
The AHC-1000( ) has continuous self test (in-line monitoring) which provides an indication of the health of the unit. A variety
of monitors are employed to obtain a very high coverage of failure conditions. Detected faults are annunciated on the front
panel status indicator. During initialization, the indicator flashes in color sequence: red, amber and green. After initialization,
the LED annunciates the following status indications:
• AHC-1000( ) critical fault = RED
• FDU-3000 (or synchro-type FDU) or ECU-3000 but no AHC-1000( ) critical fault = AMBER
• No AHC-1000( ), FDU-3000 (or synchro-type FDU) or ECU-3000 critical faults = OFF
The program supplied to the processor integrates the inputs from the IMU, FDU, the discrete straps and controls, and the com-
pensation data of the ECU to develop the necessary data for the attitude and heading display systems, and other aircraft systems
requiring these inputs. The AHC-1000A and AHC-1000S provide pitch, roll, and heading synchro outputs and analog rate and
acceleration outputs.
4-8 1 May 2006

523-0806057
CHAPTER 5
MAINTENANCE
5.1 GENERAL
This section provides information about maintenance procedures and self-diagnostic monitoring for the AHC-1000( ).
5.2 MAINTENANCE SCHEDULE
No periodic maintenance is required on the AHS-1000( ).
5.2.1 Power Requirements All power required to perform the system tests and troubleshooting is provided by the aircraft
in which the system is installed.
5.3 TESTING AND TROUBLESHOOTING
No tests beyond those shown in the installation section are necessary. Fault isolation is conducted through standard troubleshoot-
ing procedures. No special fault isolation techniques exist.
5.3.1 Diagnostic Information While in the AHRS mode the AHC-1000( ) continuously performs in-line monitoring func-
tions. The LRU monitors for excessive aircraft maneuvers and data received from the FDU. The AHC also provides indications
of the system status on the front panel LED. If the AHC-1000( ) has a critical fault, the LED will be red. If the FDU-3000( )
(or the synchro-type FDU), or EDU-3000, but not the AHC-1000( ) has a critical fault, the LED will be amber. If there are no
critical faults the LED will be off.
4 February 2003 5-1/(5-2 Blank)

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installation manual AHS-1000( ) Attitude Heading

© Copyright 2006 Rockwell Collins, Inc. All rights reserved.

Rockwell Collins, Inc.

TO: HOLDERS OF ROCKWELL COLLINS® AHS-1000( ) ATTITUDE HEADING SYSTEM

REVISION NO 2, DATED MAY 1/06

PAGE NUMBER DESCRIPTION OF REVISION AND SERVICE EFFECTIVITY

Printed in the United States of America Rockwell Collins, Inc.

EXPORT CONTROL LAWS

NOTICE: FREEDOM OF INFORMATION ACT (5 USC 552) AND DISCLOSURE OF

SOFTWARE COPYRIGHT NOTICE

© COPYRIGHT 2003 - 2006 ROCKWELL COLLINS, INC. ALL RIGHTS RESERVED.

All software resident in this equipment is protected by copyright.

Send your comments to: Rockwell Collins, Inc.

All requests for product orders or inquiries please contact.

Send your request to: Rockwell Collins, Inc.

INSERT LATEST CHANGED PAGES. DESTROY SUPERSEDED PAGES.

Dates of issue for original and changed pages are:

TOTAL NUMBER OF PAGES IN THIS PUBLICATION IS 80 CONSISTING OF THE FOLLOWING:

Page No. *Change No. Page No. *Change No.

*Zero in this column indicates an original page.

Figure Title Page

1 May 2006 iii

Table Title Page

To submit comments regarding this manual, please contact:

Collins Aviation Services

Attn: Technical Operations M/S 153-250

or send email to: techmanuals@rockwellcollins.com

1 May 2006 vii

viii 1 May 2006

COLLINS EQUIPMENT DESCRIPTION PART NUMBER

1 May 2006 1-1

Figure 1-1. AHS-1000( ) Attitude Heading Reference System

Table 1-2. Equipment Specifications.

1-2 1 May 2006

Table 1-2. Equipment Specifications. - Continued

1 May 2006 1-3

Table 1-2. Equipment Specifications. - Continued

Source ID (P1-61/106) Gnd (P1-95)/open; gnd = 0, open = 1

Source ID Common (P1-95) Source ID common

1-4 1 May 2006

Table 1-2. Equipment Specifications. - Continued

1 May 2006 1-5

Table 1-2. Equipment Specifications. - Continued

1-6 1 May 2006

Table 1-2. Equipment Specifications. - Continued

Configurable Synchro/Analog Outputs The AHC-1000A/-1000S provides a set of configurable synchro/analog

Yaw Rate (H)(154mv/°/s) When ECU 822–1200–210 or -211 installed.

1 May 2006 1-7

Table 1-2. Equipment Specifications. - Continued

1-8 1 May 2006

Table 1-2. Equipment Specifications. - Continued

Slave Meter Output The AHC-1000A/-1000S provides a slave meter output.

1 May 2006 1-9

Table 1-2. Equipment Specifications. - Continued

1-10 1 May 2006

Table 1-2. Equipment Specifications. - Continued

Table 1-3. Performance Characteristics.

CHARACTERISTIC RANGE Nominal Accuracy (2 sigma )

Page No. Change No. Page No. Change No.