HOW TO USE THIS MANUAL (TM 55-1520-240-T)
This manual has 17 Chapters that have instructions for troubleshooting 72 CH-47 Helicopter Systems.
apter 1 has:
The Complete List of Troubleshooting Symptoms you will find in this manual. This list outlines each
chapter by system and symptom.
Complete wiring for 300 Series Connectors and Receptacles, Terminal Boards, and Ground Devices.
Chapters 2 thru 17 have sets of troubleshooting instructions that include:
A Chapter outline of all systems and symptoms found in the beginning of each Chapter.
Connector part numbers and pin patterns for each connector and receptacle in systems contained
in chapter. Also included are relay termination views and ground termination types and location.
System Schematics and/or Wiring Diagrams.
Visual Checks with locator figures and step by step procedures.
Operational Checks with locator figures and step by step procedures.
Fault Isolation Procedures with locator figures and troubleshooting logic for specific system faults.
HOW TO FIND WHAT YOU NEED
MaintenanceRefer to TM 55-1520-240-23.
TroubleshootingUse the index in Chapter 1 or in the beginning of each chapter. This is where you will find
the system troubleshooting procedures (visual checks, operational checks and fault isolation procedures).
The troubleshooting procedures are listed under the name of the system that the component or system
2. Each system has a number:
Cabin and Ramp Lights
3. Each item in your set of troubleshooting instructions has a task number. The system number is prefixed to
each of the item task numbers.
Cabin and Ramp Lights
Cabin and Ramp Circuit Breaker
Does not Stay Closed
Each Troubleshooting procedure begins with INITIAL SETUP information. Read
tells you what you need and what you have to know before you begin the job.
T M 5 5 - 1 5 2 0 - 2 4 0 - T
before starting. It
Applicable Configurations. Tells you what configurations or effectivity the task applies to.
Tools. If any tools from your tool kit are needed, just the kit is listed. Tools needed that are not in the kit
are called for by name. Special ground support tools, containers, and test equipment are listed by tool
number (Txx). Find these items in TM 55-1520-240-23.
Materials. Materials needed are listed by expendable number (EXX). Find these items in TM 55-1520-
Parts. New parts required, such as gaskets, packings, and washers, are listed by name only. If parts are
not needed, you will not see this heading.
Personnel Required. Each MOS needed to do the task is Iisted. When more than one of any MOS is
needed, the number is shown in parentheses.
References. Lists references such as TM 55-1520-240-23. These references will provide where infor-
mation can be found when you need to repair or replace a part or component. When more than one
reference is listed, the Fault Isolation Procedure blocks will contain a refer to statement for all references
other than TM 55-1520-240-23.
Equipment Condition. Procedures which must be done before starting the task are listed and task or
TM number is given. Tasks that are not indented under a TM manual can be found in this manual. Refer
to the TM manual listed above the indented tasks.
General Safety Instructions. These are safety precautions that must be observed throughout task.
Warnings include basic first aid instructions.
Locator Figure. The area of the helicopter where the task will be performed is shown, with components
to be worked on called out.
Visual Checks are performed to determine if the cause of the system fault is visually apparent.
Operational Checks are performed step by step on the system to determine the system fault. Continue
the operational check TASK until the symptom is confirmed in the RESULT column.
Fault Isolation Procedures are performed to identify the specific trouble in the system. Start with the first
block. Read it through and answer the question. The questions will always have a YES or NO answer, If
you answer the question YES, follow the direction of the YES arrow to the next block. If you answer the
question NO, follow the direction of the NO arrow to the next block. Continue troubleshooting until the
symptom cause is identified.
Use the integrated schematic during troubleshooting for a view of system component connections and
Use the wiring diagram when the troubleshooting instructions require wire tests to isolate the symptom