Auxiliary Power Unit(APU) and Maintenance Syllabus Diploma in Aircraft Maintenance Engineering, Regulation 2010

Auxiliary Power Unit(APU) and Maintenance Syllabus Diploma in Aircraft Maintenance Engineering, Regulation 2010.


  • To provide understanding of Basic requirement of APU.
  • To understand the services provided by the APU.
  • To familiarize with different types of constructional features of APU.
  • To familiarize with the construction of APU.
  • To identify different constructional materials.
  • To understand the different systems of APU.
  • To understand the fire protection system.
  • To identify the cause of auto-shutdown of APU.
  • To familiarize with different types troubleshooting of APU.
  • To familiarize with different types maintenance of APU.
  • To familiarize with storage procedure of APU.


Short Description:

Introduction to the basic requirements, principle of operation, constructional arrangement, different systems, maintenance, troubleshooting preservation and storage procedure of APU.

Detail Description



  1. Understanding of APU General Arrangement

1.1       Define modular design concept

1.2       Explain model numbering system

1.3       Describe mart numbering system

1.4       Discuss APU Data Plate


  1. Understanding of Power plant

2.1       Define APU air intake

2.2       Illustrate APU door actuation

2.3       Discuss inlet door actuator

2.4       Narrate inlet door proximity switch

2.5       Describe inlet door mechanism

2.6       Discuss exhaust door


  1. Understanding of Engine Description & Operation

3.1       General

3.2       Describe air inlet section

3.3       Explain compressor section

3.4       Discuss combustion section

3.5       Describe turbine section

3.6       Explain accessory drives

3.7       Discuss compressor control

3.8       Narrate APU mounts

3.9       Describe accessory/ bay cooling

3.9.1    Discuss noise suppressor

3.9.2    Explain accessory compartment cooling

3.10     Describe engine drains

  1. Understanding of lubricating System


4.1       General

4.2       Describe operation

4.3       Explain distribution

4.4       Discuss stores
4.5       Narrate indicating


  1. Understanding of Fuel Control

5.1       General

5.2       Describe distribution

5.3       Discuss controlling/limiting factors

5.4       Explain indicating

5.5       Describe operation


  1. Understanding of Ignition & Starting/ Ground Running

6.1       General

6.2       Discuss distribution

6.3       Describe operation

6.4       Explain cranking


  1. Understanding of Engine Speed Control

7.1       General

7.2       Describe power control


  1. Understanding of Indicating System

8.1       General

8.2       Describe power supply

8.3       Explain operation


  1. Understanding of Safety Features/Emergency Shutdown

9.1       Description

9.2       Other emergency shutdown


  1. Understanding of Load Control/ APU Air

10.1     General

10.2     Describe airflow

10.3     Discuss surge valve

10.4     Explain load bleed valve

10.5     Illustrate indicating system


  1. Understanding of APU Fire Protection & Indication

11.1     Operation

11.2     Explain APU fire extinguishing system

11.3     Describe Fire extinguisher containers

11.3.1 Discharge nozzle

11.3.2 Explain discharge cartridge

11.4     Describe fire extinguisher deployment lines

11.4.1  Describe check valve

11.4.2 Explain fire extinguisher discharge control

11.5     Discuss low pressure warning system


  1. Understanding of APU Generator & Electrical control



  1. Understanding of Storage Procedure

13.1     Describe short-term storage

13.2     Explain long-term storage


Typical Auxiliary Power Unit


  1. Understanding of Auxiliary Power Unit

14.1     General

14.2     Describe air intake duct

14.3     Explain exhaust duct

14.4     Discuss major components

14.4.1  Describe gas turbine assembly

14.4.2  Describe combustor assembly

14.4.3  Explain reduction drive assembly

14.4.4  Describe accessory drive assembly

14.5     Explain APU systems

14.5.1  General

14.5.2  Describe oil system

14.5.3  Explain fuel system General Discuss indication system

14.6     Explain APU Fuel Control Unit (FCU)

14.7     Describe ignition system

14.8     Discuss electronic sequence unit

14.9     Illustrate Build in Test Equipment (BITE)

14.10   Describe APU over-speed protection & test

14.11   Explain bleed air system

14.11.1 General

14.11.2 Explain start by-pass valve

14.11.3 Describe bleed valve

14.12   Explain starter generator

14.12.1 Description & operation

14.12.2 Describe starter operating limit

14.12.3 Discuss control and indication

14.12.4 Describe load monitoring

14.13 Explain fire protection

14.13.1 General

14.13.2 Describe fire extinguishing

14.13.3 Describe operation

14.13.4 Explain testing

14.13.5 Discuss thermal and system discharge

14.14   Describe APU compartment ventilation

14.15   Explain rear bay over temperature

14.16   Illustrate APU starting procedure

14.17   Describe APU shut down procedure

14.17.1 Describe normal APU shut down

14.17.2 Explain alternate APU shutdown












  1. Show skill in identifying of various sections of APU
  2. Show skill in identifying of various components of APU
  3. Show skill in removal/Installation of various accessories
  4. Show skill in removal/Installation of APU
  5. Show skill in troubleshooting
  6. Show skill in APU Servicing


Reference Books:


  2. Garott APU (F28 Aircraft Training Note ATA Chapter 49)
  3. Allied Signal A250 APU (A310 Airbus Aircraft Training Note ATA Chapter 49)