Thommen CM20 Quick start guide

User Operational Manual
CM20 Digital Chronometer
THOMMEN AIRCRAFT EQUIPMENT AG
H ofackerstrasse 48, CH-4132 Muttenz, Switzerland
USER OPERATIONAL MANUAL
CM20 DIGITAL CHRONOMETER
Revision: 1.5
29/04//2022

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RECORD OF REVISIONS
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RECORD OF REVISIONS
Rev. Date Reason for Revision Prepared Checked Approved
1.0 NOV 4/2011 Initial Release - -
1.1 JAN 9/2012 Format update - -
1.2 JUN 12/2012 Content update - -
1.3 AUG 20/2012 Layout corrections - - Ulrich Dembinski
1.4 NOV 30/2018
Document updated in new format with TAE
company address and logo.
General grammatical corrections.
J. Garrett M. Schaffner M. Sreetharanathan
1.5 APR 29/2022 Removal of MID number (P/N 1613).
General corrections and improvements.
J. Garrett
G. Schaffner
A. Savin

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SERVICE BULLETIN LIST
SB No. Subject Rev. Date

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LIST OF EFFECTIVE PAGES
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LIST OF EFFECTIVE PAGES
SECTION PAGE REV. DATE SECTION PAGE REV. DATE
Title Page 1 1.5 29/04/22 Introduction 1 1.5 29/04/22
2 1.5 29/04/22 2 1.5 29/04/22
3 1.5 29/04/22
4 1.5 29/04/22
Record of Revisions 1 1.5 29/04/22
2 1.5 29/04/22
Description and Operation 1 1.5 29/04/22
2 1.5 29/04/22
3 1.5 29/04/22
Service Bulletin List 1 1.5 29/04/22 4 1.5 29/04/22
2 1.5 29/04/22 5 1.5 29/04/22
6 1.5 29/04/22
7 1.5 29/04/22
8 1.5 29/04/22
List of Effective Pages 1 1.5 29/04/22 9 1.5 29/04/22
2 1.5 29/04/22 10 1.5 29/04/22
11 1.5 29/04/22
12 1.5 29/04/22
13 1.5 29/04/22
Table of Contents 1 1.5 29/04/22 14 1.5 29/04/22
2 1.5 29/04/22 15 1.5 29/04/22
16 1.5 29/04/22
17 1.5 29/04/22
18 1.5 29/04/22
Fault Isolation 101 1.5 29/04/22
102 1.5 29/04/22

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TABLE OF CONTENTS
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TABLE OF CONTENTS
RECORD OF REVISIONS 1
SERVICE BULLETIN LIST 1
LIST OF EFFECTIVE PAGES 1
TABLE OF CONTENTS 1
INTRODUCTION 1
1. Proprietary Notice 1
2. Purpose of this Manual 1
3. Manual Description 1
4. Revisions 1
5. Warnings, Cautions and Notes 2
5.1 Warnings 2
5.2 Cautions 2
5.3 Notes 2
6. Technical Support 2
7. Installer Responsibility 2
8. Document/Equipment Feedback 2
9. List of Abbreviations 4
DESCRIPTION AND OPERATION 1
1. Description 1
1.1 General 1
1.2 Function Description 1
1.3 Limitations 2
1.4 References 2
1.5 Warnings and Cautions 2
2. Operation 3
2.1 General 3
2.2 Pre-flight Procedures 3
2.3 Test Function 3
2.4 Display Options and Modes 3
2.4.1 Local Time (LT) 5
2.4.2 LT Set Page 6
2.4.3 Flight Time (FT) 7
2.4.4 Maintenance Timer in Hours (MTH) 8
2.4.5 Flight Timer Alarm (FTA) 9
2.4.6 Flight Timer Alarm (FTA) Set Page 10
2.4.7 Elapsed Timer (ET) 11
2.4.8 Elapsed Timer Down (ETD) 13
2.4.9 Elapsed Timer Down (ETD) Set Page 14
2.4.10 Alarms 15
2.5 User Programmable Modes 16
2.6 Operating Features 16
2.7 Other Programmable Modes 16

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2.8 NVIS 16
2.9 Emergency Procedures 16
3. Quick Reference Guide 17
FAULT ISOLATION 101
1. General 101
1.1 Malfunctions 101
1.2 Troubleshooting 101

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INTRODUCTION
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INTRODUCTION
1. Proprietary Notice
The information disclosed within this document, or separately supplied in furtherance of this
document, includes the proprietary rights of Thommen Aircraft Equipment AG (TAE).
Neither this document nor the information disclosed herein or of a supplementary nature shall be
reproduced or transferred to other documents or used or disclosed to others for manufacturing
purposes, or for any other purposes, except as specifically authorized in writing by Thommen
Aircraft Equipment AG (TAE). All rights are reserved.
2. Purpose of this Manual
The information contained in this User Operational Manual is for operator reference use only.
For information concerning the installation and configuration of the CM20 Digital Chronometer,
refer to the Installation and Operating Manual (CM20-INSOP), ATA 31-22-10.
For repair procedures, refer to the Component Maintenance Manual (CM20-CMM),
ATA 31-22-10.
3. Manual Description
The page blocks in this manual comply with the Air Transport Association of America (ATA)
specification i2200.
4. Revisions
Thommen Aircraft Equipment AG (TAE) gives the customers (that have a product guarantee) a
complete revised manual when a change is included in a manual. The Record of Revisions
section gives the reason for the changes done in the current revision.
A documentation revision service (with a customer portal) is also available for customers that
have instruments/devices no longer covered by a product guarantee. This can be useful when an
upgrade to the instrument/device can improve the operational life and/or reliability of older
products.
The documentation revision service also includes the necessary Service Bulletins that
upgrade/modify the device.

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INTRODUCTION
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5. Warnings, Cautions and Notes
5.1 Warnings
WARNING: WARNINGS ARE GIVEN IN THE RELEVANT PAGE BLOCKS TO TELL
PERSONNEL ABOUT SOMETHING THAT CAN CAUSE INJURY TO THEM.
WARNINGS ARE GIVEN IMMEDIATELY BEFORE THE APPLICABLE TEXT
TO WHICH THEY REFER.
5.2 Cautions
CAUTION: CAUTIONS ARE GIVEN IN THE RELEVANT PAGE BLOCKS TO TELL
PERSONNEL ABOUT SOMETHING THAT CAN CAUSE DAMAGE TO THE
EQUIPMENT. CAUTIONS ARE GIVEN IMMEDIATELY BEFORE THE TEXT
TO WHICH THEY REFER.
5.3 Notes
NOTE: Notes give helpful information to the personnel doing the task. Notes are included
before or after the text to which they refer.
6. Technical Support
Approved Servicing Facilities exist worldwide. Please contact Thommen Aircraft Equipment AG
at the address given below for information regarding the facility nearest to your location.
THOMMEN AIRCRAFT EQUIPMENT AG
Hofackerstrasse 48
CH-4132 Muttenz
Switzerland
Phone: [phone]
Email: tech-s[email protected]
Internet: www.thommen.aero
7. Installer Responsibility
The installer (and/or Approved Service Facility) is responsible for the correct installation of the
equipment. This includes the mechanical and electrical configuration and compatibility with the
aircraft.
8. Document/Equipment Feedback
The Document / Equipment Defect Report (on the next page) gives the customer and/or
Approved Service Facility a way to inform Thommen Aircraft Equipment AG about any defects
regarding the equipment or discrepancies in the technical documentation. This feedback will help
Thommen Aircraft Equipment AG to make continued improvements to the equipment and/or the
technical documentation.

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INTRODUCTION
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DOCUMENT / EQUIPMENT DEFECT REPORT
Aircraft Type Serial No. Manual No. Operator
Date Reported By Contact Details
Document / Equipment:
Description of Defect:
Corrective action taken to continue operation:
Please send to:
THOMMEN AIRCRAFT EQUIPMENT AG
Hofackerstrasse 48
CH-4132 Muttenz
Switzerland
Telephone: [phone]
Email: tech-[email protected]

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9. List of Abbreviations
Abbreviation Description
ATA Air Transport Association
BAT Battery
CM20 Digital Chronometer, Type CM20
CMM Component Maintenance Manual
DEF Defect
ERR Error
ET Elapsed Time
ETD Elapsed Timer Down
FT Flight Time
FTA Flight Timer Alarm
INSOP Installation and Operating Manual
LCD Liquid Crystal Display
LED Light Emitting Diode
LT Local Time
MID Master Identification Number
MOD Mode
MTH Maintenance Timer in Hours
NVIS Night Vision Imaging System
REV Revision
RST Reset
RTCA Radio Technical Commission for Aeronautics
SB Service Bulletin
ST/SP Start/Stop
TAE Thommen Aircraft Equipment
UTC Universal Coordinated Time

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DESCRIPTION AND OPERATION
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DESCRIPTION AND OPERATION
1. Description
1.1 General
The CM20 is a digital chronometer with Universal Coordinated Time (UTC), Local Time (LT),
Flight Timer (FT), Flight Timer Alarm (FTA), Elapsed Timer (ET), Elapsed Timer Down (ETD)
and Maintenance Timer in Hours (MTH) functions.
It has the purpose to provide clock and timer capabilities in aviation cockpit applications.
1.2 Function Description
The CM20 has a three-line negative image liquid crystal display (LCD). The top line shows
the UTC; the middle and bottom lines show the selected additional function.
Dual mode (day/night) LED backlighting allows the display to be clearly read under all lighting
conditions.
Located below the display, 3 push-buttons allow the user to easily switch between display
modes or to start and stop the counter.
A built-in battery prevents the loss of stored time settings if there is a power interruption.
Figure 1 – CM20 Digital Chronometer, Front View

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1.3 Limitations
The CM20 is vibration tested in accordance with category U2 of section 8.0 of RTCA/DO-
160F, curves F and F1, without shock mounts.
The CM20 can therefore be installed in a helicopter or a fixed wing aircraft.
The CM20 can be operated within the following environmental limitations:
•Temperature: -45° C to +70° C (-49° F to +158°F)
•Altitude: Max. 55 000 ft (16 800 m)
•Humidity: 95% ±4% relative humidity
1.4 References
Refer to Installation and Operating Manual (CM20-INSOP) for installation and configuration
instructions.
Refer to Component Maintenance Manual (CM20-CMM) for overhaul procedures.
1.5 Warnings and Cautions
WARNING: IF AN AIRCRAFT PILOT IS USING NVIS GOGGLES, AN UNINTENDED
SWITCH OF THE CM20 TO DAY MODE CAN INCREASE THE DISPLAY
LUMINANCE TO A LEVEL WHERE THE PILOT CAN BE TEMPORARILY
BLINDED. IN THIS CONDITION, THE NVIS GOGGLES CAN
UNEXPECTEDLY SHUT DOWN.

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DESCRIPTION AND OPERATION
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2. Operation
2.1 General
When electrical power is switched ON, the CM20 enters a self-test routine. During this time,
all display segments are turned on for about five seconds, as shown below.
Figure 2 - Display Self-test
During normal mode of operation, the CM20 cycles between the different display pages by
pressing the MODE button.
When available, the RESET button switches to the corresponding set display page. The
value to be set starts blinking.
The top line always displays the UTC value; the content of the middle and bottom lines varies.
2.2 Pre-flight Procedures
If not already done, set Local Time (LT) to the desired value. Refer to LT Set Page
(Description and Operation, section 2.4.2) for further details.
All timers (FT, ET, ETD) are automatically reset when power is supplied to the CM20.
2.3 Test Function
No manual function tests can be applied to the CM20. The power-up self-test detects all
possible failures.
2.4 Display Options and Modes
Each function is represented by a display page.
The following figure shows all the display pages and the order in which they appear.
The following sub-sections (2.4.1 to 2.4.10) describe the display pages.

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DESCRIPTION AND OPERATION
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Figure 3 - Display Page Selection

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2.4.1 Local Time (LT)
The first mode entered by CM20 is Local Time. The middle line displays the local time,
the bottom line statically displays ‘LT’.
Depending on the configuration setting, the local time can be displayed in 12-hour or
24-hour format. The local time varies from UTC by whole hours.
Figure 4 - LT in 12-hour Format
Figure 5 - LT in 24-hour Format

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DESCRIPTION AND OPERATION
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2.4.2 LT Set Page
The UTC and Local Time can be manually set. Use the RESET button to switch to the
desired field to be set (e.g., UTC hours, LT hours, etc.) and increase the value with the
START/STOP button.
Pressing the MODE button cancels the setting operation and leaves the time values
unaltered.
The final RESET button push, after the seconds field, sets the time to the defined values.
A summary of the process is shown below.
Figure 6 - Setting UTC and Local Time