Chapter 1. INTRODUCTION

TM 55-4920-431-13

CHAPTER 1

INTRODUCTION

GENERAL

INFORMATION

Section I.

1-1. Purpose. Auxiliary Power Unit Electronic Sequence Unit Multi-Purpose Test Set,

Part No. 161226-200 referred to herein as the tester figure 1-1, is used to troubleshoot

an Auxiliary Power Unit (APU) and Electronic Sequence Unit (ESU), either in the air-

craft or in a maintenance shop or test cell.

1-2. Capabilities. The tester allows the user to dynamically test the APU and ESU

independent of all aircraft controls and to isolate a fault to a malfunctioning com-

ponent or part. Refer to fault logic tree in the applicable maintenance manual.

1-3. The tester can be used to control the APU and monitor all functions, to test

the APU in a test cell after overhaul or repair.

1-4. The tester can be used in a maintenance shop for troubleshooting or repair

of the ESU.

1-1