apu

HONEYWELL

This is an unpublished work protected under the copyright laws ofthe United States and other countries. Should publication occur,then the following notice shall apply: COPYRIGHT 2000 HoneywellInternational Inc.

This document and all information and expression containedherein are the property of Honeywell International Inc. are loanedin confidence, and may not, in whole or in part, be used, dupli-cated, or disclosed for any purpose without prior permission ofHoneywell International Inc. These commodities may require anexport license for shipment outside the United States. Exportwithout an appropriate export license is contrary to U.S.law.

All rights reserved

Page i

131-9B Line Maintenance - Trainng Manual

FOREWORD

Information contained herein is intended as a general descriptionof operation which will permit maintenance and systematic trou-bleshooting of the subject system or components describedherein.

It is not the intent of the Honeywell International Inc. that thistraining study guide be used as a supplement to, or in lieu of, anyofficial publication. Contents herein are subject to change withoutnotice and are not exposed to the benefits of constant revision orupdate.

The reader of this manual is reminded that all values of pressure,temperature, speed, power, etc., are chosen for their illustrativemeaning only, and are not necessarily representative of actualvalues of any engine configuration. For actual values the applica-ble maintenance manual must be consulted.

The official publications pertaining to operating procedures, lim-its, and capabilities of the engine are the responsibility of the air-frame manufacturer.

The airframe manufacturer installs the engine in its airframe,designs, and/or manufacturers the electrical and mechanical con-trols, selects the instruments, and flight tests the aircraft.

The airframe manufacturer determines how, and under what limi-tations, the engine will be operated for all modes of aircraft oper-ation.

Honeywell International Inc. may suggest and advise -- but notdictate -- the operational and maintenance practices it feels arebest for the engine.

Some aircraft manufacturers will assimilate Honeywell Interna-tional Inc. manuals into their own publications, while other manu-facturers may simply refer the owner/operator to HoneywellInternational Inc. published manuals.

THIS TRAINING MANUAL HAS NO OFFICIAL STATUS. IN ALLINSTANCES, INFORMATION CONTAINED IN OFFICIAL PUBLICA-TIONS SHALL GOVERN.

Course GoalThis course is designed to provide maintenance personnel withthe training required to service, inspect, operate, and performline maintenance activities on the 131-9B Auxilaiary Powre Unitfollowing the procedures outlined in the applicable tehnical man-ula.

Notes:

Page ii

131-9B Line Maintenance Training Manual

Table of Contents

Chapter 1—Introduction and Description

Objectives ......................................................................................................................... 1-1Overview .......................................................................................................................... 1-2LRU Location .................................................................................................................. 1-4

Right View ................................................................................................................ 1-4Forward view ........................................................................................................... 1-6Left View .................................................................................................................. 1-8

Operating Specifications .............................................................................................. 1-10APU Design and Function .......................................................................................... 1-12Operating Envelope ...................................................................................................... 1-14Summary ......................................................................................................................... 1-16

Chapter 2—Installation and Interface

Objectives ......................................................................................................................... 2-1Overview .......................................................................................................................... 2-2APU Location .................................................................................................................. 2-4APU Installation .............................................................................................................. 2-6

APU Drain Manifold .............................................................................................. 2-8Aircraft Control/Display Interface ............................................................................ 2-10

Electronic Control Unit ....................................................................................... 2-12APU Master Switch .............................................................................................. 2-14APU Indication Panel ........................................................................................... 2-16APU Bleed Valve Switch ..................................................................................... 2-18APU Generator Switches ..................................................................................... 2-20APU Ground Control Panel ............................................................................... 2-22APU Fire Handle Switch ..................................................................................... 2-24

APU Start Sequence ...................................................................................................... 2-26Ready to Load (RTL) ............................................................................................ 2-28Environmental Control System Mode (ECS) .............................................. 2-30Main Engine Start (MES) .................................................................................... 2-30

APU Shutdown .............................................................................................................. 2-32Normal Shutdown ................................................................................................ 2-32

Protective Shutdown .............................................................................................2-34Summary .........................................................................................................................2-36

Chapter 3—Electronic Control Unit Operation and Interrogation

Objectives ......................................................................................................................... 3-1 overview ........................................................................................................................... 3-2ECU Interface .................................................................................................................. 3-4ECU Functions ................................................................................................................ 3-6Control Display Unit (CDU) ......................................................................................... 3-8

Current Status Page ...............................................................................................3-10Fault History Page .................................................................................................3-12Maintenance History Page ...................................................................................3-14Input Monitoring Page .........................................................................................3-16IDENT/CONFIG Page ......................................................................................3-18Oil Quantity ............................................................................................................3-20

Summary .........................................................................................................................3-22

Chapter 4—Theory of Operation & Construction

Objectives ......................................................................................................................... 4-1Overview ........................................................................................................................... 4-2Main APU Engine Sections ........................................................................................... 4-4Basic Operating Cycle ..................................................................................................... 4-6Load Compressor Operation ......................................................................................... 4-8Surge Protection ............................................................................................................4-10Generator and Accessories ...........................................................................................4-12APU Temperature Control ..........................................................................................4-14Summary .........................................................................................................................4-16

Chapter 5—Lubrication System

Objectives ......................................................................................................................... 5-1Overview ........................................................................................................................... 5-2Power Section Turbine Bearing Cavity ........................................................................ 5-4

Table of Contents Page iii


Forward Bearing and Seal .............................................................................................. 5-6Lubrication System Components ................................................................................. 5-8

Lubrication Module .............................................................................................. 5-10Lube Supply Filter ........................................................................................ 5-12Generator Scavenge Filter ........................................................................... 5-12High Oil Temperature Sensor .................................................................... 5-14

Oil Cooler ............................................................................................................... 5-16Gearbox / Oil Sump ............................................................................................ 5-18Low Oil Quantity Switch ..................................................................................... 5-20Magnetic Chip Collector and Drain Plug .......................................................... 5-22Temperature Control Valve ................................................................................. 5-24Low Oil Pressure (LOP) Switch ......................................................................... 5-26Air-Oil Separator ................................................................................................... 5-28

Oil Servicing Provisions ............................................................................................... 5-30Lubrication System Flow ............................................................................................. 5-32Summary ......................................................................................................................... 5-34

Chapter 6— Fuel System

Objectives ......................................................................................................................... 6-1Fuel System Overview .................................................................................................... 6-2Fuel System Components .............................................................................................. 6-4

Fuel Control Unit (FCU) ....................................................................................... 6-6Fuel Filters ............................................................................................................. 6-10Fuel Metering Assembly ...................................................................................... 6-12fuel Flow Divider & flow divider solenoid ....................................................... 6-14Fuel Manifolds & Fuel Nozzles .......................................................................... 6-16Fuel Shutoff Solenoid ........................................................................................... 6-18IGV Actuator Pressure Regulating Valve ......................................................... 6-20Plenum Drain Valve ............................................................................................. 6-22APU Drain Manifold ............................................................................................ 6-24

Fuel System Flow ...........................................................................................................6-26Summary .........................................................................................................................6-28

Chapter 7—Pneumatic System

Objectives ......................................................................................................................... 7-1Overview ........................................................................................................................... 7-2Pneumatic System Components .................................................................................... 7-4

Surge Control Valve (SCV) .................................................................................... 7-6Flow Sensor Assembly ............................................................................................ 7-8Inlet Temperature Sensor (T2) ............................................................................7-12Bleed Air Valve (BAV) .........................................................................................7-14

Inlet Guide Vane (IGV) Assembly .............................................................................7-16Summary .........................................................................................................................7-18

Chapter 8—Electrical Accessories

Objectives ......................................................................................................................... 8-1Overview ........................................................................................................................... 8-2Electrical Accessories Components .............................................................................. 8-4

Start Power Unit (SPU) .......................................................................................... 8-6Start Converter Unit (SCU) ................................................................................... 8-8Starter-Generator ...................................................................................................8-12Ignition Unit ...........................................................................................................8-14EGT Thermocouples ............................................................................................8-16Speed Sensor ..........................................................................................................8-18Data Memory Module (DMM) ............................................................................8-20

Summary .........................................................................................................................8-22

Chapter 9—Glossary

Table of Contents Page iv


CHAPTER 1—INTRODUCTION AND

DESCRIPTION

OBJECTIVES

Upon completion of this chapter, you will be able to:• List the main functions of the 131-9B APU• Show the location of the APU line replaceable units (LRU)• Describe the operating specifications and operating

envelope for the APU

Introduction and Description Objec

Notes:

tives Page 1-1


OVERVIEW

The 131-9B APU is a self-contained power unit used in the Boeing737-600/-700/-800 airplanes. It is designed to function as a com-bination shaft and pneumatic power source. The APU is controlledby a system of electronic, hydraulic, and electro-mechanical con-trols. Power output is ready for use while the airplane is on theground or in the air.

The APU provides the 737-600/-700/-800 airplane with:- Pneumatic power for airplane main engine starting

(MES)- Pneumatic power for cabin air conditioning (up to

17,000 feet altitude.)- Electric power up to 41,000 feet for the airplane

The APU is comprised of three major sections:- Gearbox- Load Compressor- Power Section

GearboxThe accessory gearbox provides gear reduction for the high speedtorque of the power section. The gearbox also serves as the oilreservoir. Accessories mounted to the gearbox include the oilcooler, starter/generator, and the oil pump.

Load CompressorThe load compressor section supplies air pressure to the aircraftbleed air manifold. It is mounted on a common shaft with thepower section rotating group and shares a common inlet with thepower section compressor.

Introduction and Description Overv

Power SectionThe power section creates mechanical energy to turn the APU’smain shaft. The power section drives the load compressor andaccessory gearbox, providing a high-pressure ratio, high-power-density design that minimizes weight, volume, and fuel consump-tion. Features are:

• a single-stage, 8:1 pressure-ratio centrifugal compressor, a reverse-flow annular combustor, and a two-stage axial turbine.

• a single main shaft that ties the engine compressor and turbine to the load compressor. The shaft is supported by two bearings, a duplex ball bearing located forward of the L/C impeller and a roller bearing located aft of the second-stage turbine.

• Carbon seals used in the front and rear bearing cavities.• a first-stage turbine stator that is compressor air cooled.

Notes:

iew Page 1-2

ATM717-001131-9B Overview

131-9B Overview

ATM717.00109/02

Introduction and Description Overview Page 1-3


LRU LOCATION

RIGHT VIEW

Components include:• Starter Generator• Bleed Air Valve• Inlet Guide Vane Actuator• Surge Control Valve• Ignition Unit• Gearbox Vent Line

Introduction and Description LRU Lo

Notes:

cation Page 1-4

ATM717-089Right Side View

Right Side View

ATM717.08911/02

IgnitionUnit Surge Control

Valve Inlet GuideVane Actuator

Bleed AirValve

Starter/Generator

GearboxVent Line

Introduction and Description LRU Location Page 1-5


FORWARD VIEW

Components include:• Air/Oil Separator• Oil Fill Port• Generator Scavenge Filter• Bypass Pressure Differential Switch• Lube Filter• Magnetic Drain Plug


Notes:

cation Page 1-6

ATM717-080Forward View

Forward View

Air/OilSeparator

MagneticDrain Plug

Bypass PressureDifferential

Switch

Lube Filter

GeneratorScavenge

Filter

Oil FillPort

ATM717.08009/02



LEFT VIEW

Components include:• Temperature Regulating Valve• Oil Cooler• Ignition Unit• Fuel Flow Divider Solenoid• Data Memory Module• Oil Quantity Switch• Fuel Control Unit


Notes:

cation Page 1-8

ATM717-081Left Side View

Left Side View

ATM717.08109/02

Oil Cooler

Ignition Unit

TemperatureRegulating

Valve

Fuel ControlUnit

Oil QuantitySwitch

Data MemoryModule

Fuel FlowDivider Solenoid



OPERATING SPECIFICATIONS

The physical and operational characteristics of the APU are listedbelow. For more data on the specific model, refer to the appropri-ate maintenance manual.

Introduction and Description Operating Sp

Notes:

ecifications Page 1-10

ATM717-075Operating Specifications

Operating Specifications

ATM717.07509/02

Total APU weight:398.2 lbs (180.62 KG) with Generator.

Rated Output Shaft Power: 129 SHP Maximum 90 KVA < 32,000 feet66 KVA < 41,000 feet

Rated Output Shaft Speed: 48,800 RPM (100%)

Maximum Turbine EGT:

1175°F (635°C) at sea level

Maximum Allowable Speed: 51,728 RPM (106%)

Maximum Oil Consumption Rate: 8cc/hour

Oil Pressure Limits: 67.5±7.5 psig (466±52 KPA)

Oil Capacity: 8.7 quarts (8.3 ltrs).

Oil "ADD"message:2.5 quarts from full

Oil Quantity to LOP shutdown:4.5 quarts from full

Frequency of Oil ChangeNo oil change required

Frequency of Oil Filter ChangeAt Filter Delta-P Indication

Oil Type:MIL-L-23699 Type IIMIL-L-7808 Type ISee Maintenance Manual for specific brands

Fuel Inlet Pressure:

Fuel Filter Replacement:

APU Supply Power Unit (SPU):

APU Start Converter Unit (SCU):

ECU Power Supply:

10 psig

3500 hours or 3 years

28 vdc/500 amps200 va, 3 phase, 400Hz, 30 amps. max.

28 vdc, 8 amps max

28 vdc, 8 amps max

Introduction and Description Operating Specifications Page 1-11


APU DESIGN AND FUNCTION

The 131-9B APU is designed for ground and airborne operation.This makes it possible to use remote airfields that may not haveground power.

The APU provides the 737-600/-700/-800 airplane with:• pneumatic power for airplane main engine starting (MES).• pneumatic power for cabin air conditioning (up to 17,000

feet altitude.)• electric power up to 41,000 feet

The APU is temperature limited. If loads on the APU becomeexcessive (resulting in high EGT), “load shedding” is accom-plished. The ECB automatically cuts back the electric or pneu-matic output, depending on aircraft mode.

NOTE: Electrical power (#1 priority) can be provided independently of, or in combination with pneumatic power.

Introduction and Description APU Design a

Notes:

nd Function Page 1-12

ATM717-006APU Design & Function

APU Design & Function

ATM717.00609/02

WingAnti-IceValve

PressureTransducer

IsolationValve

PneumaticGround Service

Connection

CheckValve

HighStageValveAPU

BleedValve

ReliefValve

R PackValveL Pack

Valve

CheckValve

PressureRegulator

and ShutoffValve

Precooler

PrecoolerControlValve

S

S

S

S

M

M

M

S

Introduction and Description APU Design and Function Page 1-13


OPERATING ENVELOPE

The APU is designed to meet the following Boeing requirements:• Starting is allowed up to 41,000 feet. • Bleed and shaft power combination up to 17,000 feet

(5,183 meters). • Electrical power up to 41,000 feet (12,500 meters). • 90 KVA up to 32,000 feet (10,366 meters)• 66 KVA up to 41,000 feet (12,500 meters.)

NOTE: The limiting parameters are governed by ambient temperature and pressure altitude.

Introduction and Description Operating

Notes:

Envelope Page 1-14

ATM717-008Operating Envelope

0

Operating Envelope

ATM717.00809/02

- Electrical up to 41K - 90 KVA up to 32K - 66 KVA up to 41K

- Inflight Starting up to 41K

41,000A

ltit

ud

e x

1,00

0 (F

eet)

17,000

0

Inlet Temperature (F˚)-65 10 75 130

Combination:Bleed & Shaft loads up to17K

Introduction and Description Operating Envelope Page 1-15


SUMMARY

Now that you have completed this section, you should be able to:

• List the main functions of the 131-9B APU.• Show the location of the APU line replaceable units (LRU)• Describe the operating specifications and operating

envelope for the APU

To make certain, ask yourself the following questions:

What are the functions of the APU?The 131-9B provides:

• pneumatic power for airplane main engine starting (MES).• pneumatic power for cabin air conditioning (up to 17,000

feet altitude.)• electric power up to 41,000 feet

Where is each LRU located?Refer to the engine views located in this chapter.

What are the operating specifications for the APU?The physical and operational characteristics of the 131-9B arelisted in this chapter. The data reflected is general in nature andmust be considered such. Refer to the maintenance manual.

What is the operating envelope for the APU?The operating limiting parameters are governed by the ambienttemperature and pressure altitude.

• Starting is allowed up to 41,000 feet• Bleed and shaft power combination up to 17,000 feet

(5,183 meters)• Electrical power up to 41,000 feet (12,500 meters)

Introduction and Description Summ

• 90 KVA up to 32,000 feet (10,366 meters)• 66 KVA up to 41,000 feet (12,500 meters)

Notes:

ary Page 1-16


CHAPTER 2—INSTALLATION AND INTERFACE

OBJECTIVES

Upon completion of this chapter, you will be able to:• Explain the installation of the APU.• Explain the location of purpose of each APU interface

component (ECU and related panels) that control the APU.• Explain the conditions for Ready-to-Load, Duct

Pressurization Mode, Environmental Control System Mode, and Main Engine Start.

• Explain the start sequence of events for the APU.• Explain the normal shutdown sequence of events.• Explain the conditions that would cause a protection

shutdown.

Installation and Interface Objec

Notes:

tives Page 2-1


OVERVIEW

The APU installation provides mounting, line replacement unit(LRU) component accessibility, inlet and exhaust passages, enclo-sure cooling, oil cooling, drainage, bleed air extraction and fireprotection.

Installation components include:• Access Door• APU Inlet Door• Eductor Inlet• Exhaust Pipe• Fuel Line• Bleed Air Duct• Fire Detection Loop

Installation and Interface Overv

Notes:

iew Page 2-2

ATM717-009 Overview

Overview

ATM717.00909/02

• Access Door

• APU Inlet Door

• Eductor Inlet

• Exhaust Pipe

• Fuel Line

• Bleed Air Duct

• Fire Detection Loop

Installation and Interface Overview Page 2-3


APU LOCATION

The APU is suspended in the tail cone. Access to the APU isthrough a large door beneath the APU. The enclosure providesmounting points, line replaceable unit (LRU) access, and fire pro-tection.

Installation and Interface APU Lo

Notes:

cation Page 2-4

ATM717-090APU Location

ATM-717.09009/02

APU Location

Installation and Interface APU Location Page 2-5


APU INSTALLATION

LocationLocationThe APU is mounted in a fireproof compartment located in the aftend of the fuselage.

Access DoorsThe APU access door on the bottom of the APU compartment per-mits servicing and maintenance. Releasing three latches on theleft side opens the access door to the right on two hinges. A rodholds the door open safely.

Mount StrutsThe APU is mounted with support struts. That provide vertical andhorizontal stability and vibration isolation.

APU Removal/InstallationFish poles are used to remove the APU. The fish poles areattached to the top of the APU compartment with fish pole cablesattached to the APU. The weight of the APU is held up by the fishpole while the APU struts are disconnected. Once the APU strutsare removed, the APU is lowered by slowly releasing the fish polecables.

APU Inlet AirAir supply to the APU is through an aircraft mounted inlet doorand plenum chamber.

Fire DetectionThe fire loop is attached to the airframe. This loop detects a firecondition and sends the information to the aircraft fire warningsystem. The aircraft system reports this condition to the APU ECUfor immediate shutdown.

Installation and Interface APU Inst

DrainsThe APU has a drain manifold consisting of a forward, middle, aftdrain. This system provides a means for draining fluid overboard.

NOTE: The fire loop assembly does not have to be removed prior to APU removal.

Notes:

allation Page 2-6

ATM717-104APU Installation

APU Installation

ATM717.10409/02

EXHAUST MIXED FLOW

Inlet Air

Inlet VortexGenerator

APU AirOutput

APU Compartment

Eductor Inlet(cooling air)

FCU

SCV

Gen.BAV

OilCooler

Fuel TankFuel Pump

APU SOVExhaust

Pipe

APU Compartment

Door Latches

APU InletDoor

Inlet Door Actuator& Position Switch

Installation and Interface APU Installation Page 2-7


APU DRAIN MANIFOLD

The drain manifold consisting of a forward, middle, aft drain. toallow for the draining of fluid overboard.

The forward drain is used for detecting degraded seal perfor-mance in the:

• fuel control,• inlet guide vane actuator, and• surge control valve.

The middle drain is used for detecting degraded seal performancein the load compressor main shaft seal.

The aft drain is used for disposing of excess fuel in the event of anaborted start and also a means of draining the aircraft exhaustmuffler. During normal APU operation, no fuel is discharged fromthe aft drain.

The leakage limits shown are acceptable after 5 minutes of opera-tion.

NOTE: The APU inlet plenum has a drain which flows into the APU compartment.

Table 2-1:

Fuel Control Leakage Limits 3 drops per minute

Inlet Guide VAne Actuator 3 drops per minute

Surge Control Valve 3 drops per minute

Oil Consumption 8 cc per hour

Installation and Interface APU Inst

Notes:

allation Page 2-8

ATM717-020APU Drain Manifold

APU Drain Manifold

ATM717.02009/02

Gearbox Vent

InletGuide Vane

Actuator

Tell-TalePort

Tell-TalePort

Load CompressorSeal Drain

Combustor Case,Edustor Muffler,

& Drain Mast

LubeModule

FuelControl

Gearbox

SurgeControlValve

CheckValve

AirFlow

Starter/Generator

Fuel Control, Surge Control Valve,& Inlet Guide Vane Actuator

Installation and Interface APU Installation Page 2-9


AIRCRAFT CONTROL/DISPLAY INTERFACE

The APU control system consists of the Electronic Control Unit(primary control) along with other airplane panels located in thecockpit. The APU control system consists of the following:

• Full Authority Digital Electronic Controls (ECU)• APU Master Switch (APU and main engine control)• APU Bleed Valve Switch (air conditioning and pneumatics)• APU Generator Switches (electrical controls)• APU Remote Control Panel (fire protection panel -

external)• APU Fire Handle Switch (external)• APU Indication Panel

Installation and Interface Aircraft Control/D

Notes:

isplay Interface Page 2-10

ATM717-011Aircraft Control & Displays

HORNCUTOUT

BOTTLEDISCHARGE

1. PULL HANDLE DOWN

2. DISCHARGE BOTTLE

APUFIRE

CONTROL

APU Master Switch(P5-4)

APU Fire HandleSwitch (P8-1)

M1709 Electronic Control Unit(Aft Cargo Compartment)

APU Generator Switches(P5-3)

APU

OFF

ON

OFF

ON

OFF

ON1 2

OFF

ONAPU

BLEED

APU GEN

APU GENOFF BUS

OFF

ON

START

APU Bleed Valve Switch(P5-10)

APU Remote ControlPanel (P28) Right

Wheel Well

DISCH

Aircraft Control & Displays

ATM717.01109/02

Installation and Interface Aircraft Control/Display Interface Page 2-11


ELECTRONIC CONTROL UNIT

Identification and LocationThe ECU is a full-authority, digital electronic control, located inthe aft cargo compartment, next to the aft cargo door.

Purpose and InterfaceThe ECU functions include:

• Pre-Start Built-In-Test-Equipment• Automatic Start Control• Speed Control within 1 percent rpm• Protective Shutdown capability• Start Inhibit capability• Fault storage• Fault reporting to the Control Display Unit (CDU)


Notes:


ATM717-010Electronic Control Unit (ECU)

Electronic Control Unit (ECU)

ATM717.01009/02

Electronic Control Unit(Aft Cargo Compartment)



APU MASTER SWITCH

Identification and LocationThe APU master switch is located on the overhead panel (P5-4). Itcontains a start switch.

Purpose and InterfaceThe APU master switch:

• initiates APU Start and Stop sequences• controls the airplane inlet door,• controls the fuel boost pump (optional), • controls the APU fuel valve


Notes:


ATM717-091APU Master Switch

APU Master Switch(P5-4)

APU

OFF

ON

START

APU Master Switch

ATM717.09109/02



APU INDICATION PANEL

Identification and LocationThe APU indication panel is located on the overhead panel (P5-4).

Purpose and InterfaceThe APU indication panel has four lights to indicate a problem tothe operator for the following:

• maintenance• low oil pressure• fault• overspeed

The panel also has an EGT indicator for APU temperature read-ings.


Notes:


ATM717-096APU Indication Panel

P5-4 PANEL

LOW

HIGH

INT

L WIPERPARK10

EGT8

6

4 2

FAULT OVERSPEED

LOW OILPRESSUREMAINT

APU Indication Panel

ATM717.09609/02



APU BLEED VALVE SWITCH

Identification and LocationThe APU bleed valve switch is located on the overhead panel (P5-10). It is a two position switch; OFF and ON.

Purpose and InterfaceThe bleed valve switch provides a signal to the ECU. The ECUenergizes the APU bleed valve solenoid to open the bleed valve.


Notes:


ATM717-092APU Bleed Valve Switch

OFF

ON1 2

OFF

ONAPU

BLEED

APU Bleed Valve Switch(P5-10)

APU Bleed Valve Switch

ATM717.09209/02



APU GENERATOR SWITCHES

Identification and LocationThe APU generator switches are located on the overhead panel(P5-3).

Purpose and InterfaceThe APU generator switches give manual control for APU genera-tor power source selection. There are two switches because thereare two bus tie breakers (BTBs).

The blue APU GEN OFF Bus Light comes on when the APU is readyto supply electrical power.


Notes:


ATM717-093APU Generator Switches

APU Generator Switches(P5-3)

OFF

ON APU GEN

APU GENOFF BUS

OFF

ON

APU Generator Switches

ATM717.09309/02



APU GROUND CONTROL PANEL

Identification and LocationThe APU ground control panel (P28) and Fire Alarm Horn arelocated in the right wheel well, on the AFT bulkhead.

Purpose and InterfaceThe APU ground control panel allows the operator to stop the APUfrom outside the airplane.

• Pull the handle down to shut down the APU and arm the fire bottle discharge switch.

• Push the toggle switch to discharge the APU fire bottle.

APU fire alarm causes the following to occur:• The APU fire warning light to flash.• The APU fire warning horn to sound (on ground only).


Notes:


ATM717-094APU Ground Control Panel

HORNCUTOUT

BOTTLEDISCHARGE

1. PULL HANDLE DOWN

2. DISCHARGE BOTTLE

APUFIRE

CONTROL

APU Remote ControlPanel (P28) Right

Wheel Well

APU Ground Control Panel

ATM717.09409/02



APU FIRE HANDLE SWITCH

Identification and LocationThe APU fire handle switch is located on the electronic controlpanel (P8).

Purpose and InterfaceThe APU fire handle switch allows the operator to discharge theAPU fire bottle.

APU fire alarms cause the following to occur:• Automatic APU shutdown• The master fire warning lights come on.• The APU fire switch light comes on.• The APU fire switch unlocks.• The flight deck fire bell rings.

Lifting and turning the fire handle will discharge the fire bottle.


Notes:


ATM717-095APU Fire Handle Switch

APU Fire HandleSwitch (P8-1)

DISCH

APU Fire Handle Switch

ATM717.09509/02



APU START SEQUENCE

You can start the APU up to an altitude of 41,000 feet (12,500meters). The ECU controls the following components during start:

• APU inlet door• APU fuel shutoff valve• APU fuel • Ignition• APU start system

Pre-start• The battery switch must be on before you can start and

operate the APU.• If AC power is available, turn the aft number 1 fuel boost

pump on. This gives pressurized fuel to the APU. Pressurized fuel makes the APU start better.

APU Start Sequence• Move the APU master switch to the START position and

release it. The switch moves back to the ON position. Sending a signal to the ECU.

• The ECU opens the APU fuel shut-off valve and the APU inlet door. When the air inlet door is fully open, the door switch closes. The door switch sends a “door fully open” signal to the ECU.

• 0% speed, the ECU energizes the starter-generator and ignition circuit.

• 7% speed, the fuel solenoid valve opens. • 34% speed, the low oil pressure light (P5) goes out.• 60% speed, the ignition unit de-energizes• 70% speed, the starter-generator de-energizes

Installation and Interface APU Start

• 95% + 2 seconds, the APU can supply electrical and pneumatic power.

• 100% speed, full speed- >106%, overspeed shutdown is initiated.

NOTE: Maximum altitude for shaft loading is 41,000 feet and pneumatic loading is 17,000 feet.

Notes:

Sequence Page 2-26

ATM717-012APU Start Sequence

APU

OFF

START

ON

Maximum speed

APU Switch (P5)

- Battery Switch "ON"- APU Switch to the "Start" Position & Release t o"ON"- APU Fuel SOV open Air Inlet Door open- Starter/Generator Energized

1 0 0 %9 5 %

7 0 %

6 0 %

3 4 %

7 %

0 %

6 0 S e c o n d s t a r t t i m e t o 1 0 0 %

100% Governed speedElectrical & PneumaticLoading are Available

Starter/Generator de-energized

Ignition unit de-energized

Low Oil Pressure light "off"

Fuel solenoid valve opens

Ignition unit energized

1 0 6 %

APU Start Sequence

ATM717.01209/02

Installation and Interface APU Start Sequence Page 2-27


READY TO LOAD (RTL)

In the Ready to Load mode of operation, the conditions are:• Speed >95% plus 2 seconds• Bleed Air switch is OFF.

At 95% +2 seconds, the ECU sends the APU Ready-to-Load (RTL)signal to the aircraft which indicates that the generator and pneu-matic power are available.

NOTE: It should be noted that Boeing recommends 2 minute warm up before loading the APU. This allows the internal temperature to stabilize.

NOTE: The Surge Control Valve (SCV) is modulating open and Generator loading is available.


DUCT PRESSURIZATION MODE

In the Duct Pressurization mode of operation, the conditions are:• Speed >95% plus 2 seconds• Bleed Air switch ON• LMES, RMES, LECS and RECS signals are false• Altitude <17,000 feet

The IGVs are set as a function of P2 to provide at least 10 psigbleed pressure to the aircraft.

Notes:

Sequence Page 2-28

ATM717-070Ready-to-Load (RTL)

• Speed is >95 plus 2 seconds

• Bleed Air Switch in "OFF"

Duct Pressurization Mode


• Bleed Air Switch in "ON"

• LMES, RMES, LECS, & RECS signals are false

• Altitude <17,000 feet

Ready-to-Load (RTL)

ATM717.07009/02



ENVIRONMENTAL CONTROL SYSTEM MODE (ECS)

In the Environmental Control System (ECS) mode, the conditionsare:

• Speed is >95% plus 2 seconds. • Bleed Air Switch ON.• LMES and RMES signals are false.• LECS and RECS signal signals (2 pack) are true• Altitude <17,000 feet

When the left or right ECS packs are set to “ON”, the ECU sets theAPU IGVs to a pre-determined position.

MAIN ENGINE START (MES)

MES mode of operation conditions are met when:• Speed >95% plus 2 seconds.• Bleed air switch is ON• Either LMES or RMES is true• Altitude <17,000 feet

When the left or right MES switches are set to “ON”, the IGVs areset at 90° (full open) and the surge control system is active (fullyclosed).

The inlet guide vane (IGV) maximum position will vary duringMES mode. The IGV positions are determined by using inlet tem-perature. The MES positions are:

• 68° / -65°F• 71° / -40°F


• 75° / 0.0°F• 82° / 30°F• 90° / 90°F• 90° / 130°F

NOTE: In MES mode, the pneumatic power has priority over electrical. If the APU EGT trim limit is obtained, the APU electrical load is reduced to prevent an overtemperature condition.

Notes:

Sequence Page 2-30

ATM717-072Environmental Control System Mode

(ECS)

Environmental Control System Mode (ECS)

ATM717.07209/02

Main Engine Start (MES)



• LMES or RMES signals are true




• LMES and RMES signals are false

• LECS and RECS signals (2 pack) are true




APU SHUTDOWN

The ECU controls the APU shutdown. Their are two types of shut-down conditions, normal and protective.

NORMAL SHUTDOWN

The normal shutdown sequence is as follows:• APU switch placed to ‘OFF’ position

- 28 vdc ON signal removed from ECU- ECU receives the OFF signal- RTL signal is removed- 60 second cool-down period starts

• At 30% speed, the APU air inlet door starts to close (closes immediately for APU fire).

• At less than 7% speed, an APU restart can be initiated.

Cool Down CycleThe cool down period prevents oil coke at the turbine bearing andfuel nozzles. During cool down, the ECU:

• Removes the ready-to-load signal• Closes the bleed air valve• Closes the inlet guide vanes (22 degrees)• Opens the surge control valve• De-energizes the starter generator• Starts the 60 second timer

Installation and Interface APU Shu

NOTE: The APU fuel shutoff valve and air inlet door close for both the normal and protective shutdown.

NOTE: A protective shutdown has no cool down cycle.

CAUTION: DO NOT USE A BATTERY SWITCH OR FIRE SWITCH TO BEGIN A NORMAL APU SHUTDOWN. IF THE FUEL SHUTOFF VALVE DOES NOT CLOSE IN THE REQUIRED TIME, THE APU FAULT LIGHT WILL COME ON AND STAY ON UNTIL THE APU IS STARTED AGAIN OR THE BATTERY SWITCH IS PUT IN THE OFF POSITION.

Notes:

tdown Page 2-32

ATM717-013APU Normal Shutdown Sequence

OFF

ON

START

100%

APU Operating

30%

7%

0%

APU fuel shutoff valveand inlet door start to close

An APU restart can beinitiated

APU switch placed to "Off"- 28 vdc "ON" signal removed from ECU- ECU recieves the "OFF" signal- The Ready-to-load signal is removed- 60 second cool-down period starts

60 second cool down

APU Normal Shutdown Sequence

ATM717.01309/02

Installation and Interface APU Shutdown Page 2-33


PROTECTIVE SHUTDOWN

The hardware and software circuits inside the ECU control auto-matic protective shutdowns of the APU. The cause for a protectiveshutdown displays on the CDU located on the P9 panel.

Protective Shutdowns: (Fault Light ON)• APU fire • Fuel shutoff valve not in commanded position• Critical ECU failure • High oil temperature• Inlet door not in commanded position• Loss of DC power • Loss of both EGT signals• No acceleration• No flame• No speed signal • Sensor Failure• Overtemperature • Reverse flow (load compressor)• Under speed• APU inlet overheat• Generator filter clogged.

Overspeed Light ON• Fuel control unit solenoid failure• Loss of overspeed protection• Overspeed of more than 106% rpm

Low Oil Pressure Light ON• Low oil pressure

Installation and Interface APU Shu

Maintenance Light ON• Failed oil quantity switch• Low oil quantity• Start generator shorted rotating diode

Notes:

tdown Page 2-34

ATM717-065Protective Shutdowns

- APU FIRE *- FUEL SOV NOT IN COMMAND POSITION- CRITICAL ECU FAILURE *- HIGH OIL TEMPERATURE- INLET DOOR NOT IN COMMAND POSITION *- LOSS OF DC POWER- LOSS OF EGT SENSING - BOTH SIGNALS *- NO ACCELERATION- NO FLAME- NO SPEED SIGNAL- OVERTEMPERATURE- REVERSE FLOW (LOAD COMPRESSOR)- UNDERSPEED- APU INLET OVERHEAT- GENERATOR FILTER CLOGGED

- LOW OIL PRESSURE

- FUEL CONTROL UNIT SOLENOID FAILURE - LOSS OF OVERSPEED PROTECTION - OVERSPEED OF MORE THAN 106% RPM

- FAULT OF OIL QUANTITY SWITCH- LOW OIL QUANTITY- START/GEN. SHORTED ROTATING DIODE

FAULT OVERSPEED

MAINT

LOW OILPRESS

FAULTOVER

SPEEDMAINT LOW OILPRESS APU INDICATOR PANEL (P5)

* Start inhibit- Sensor Failure

Protective Shutdowns

ATM717.06509/02

Installation and Interface APU Shutdown Page 2-35


SUMMARY


• Explain the installation of the APU.• Explain the location of purpose of each APU interface

component (ECU and related panels) that control the APU.• Explain the conditions for Ready-to-Load, Duct

Pressurization Mode, Environmental Control System Mode, and Main Engine Start.

• Explain the start sequence of events for the APU.• Explain the normal shutdown sequence of events.• Explain the conditions that would cause a protection

shutdown.

Describe the APU installation.• The APU access door on the bottom of the APU

compartment permits servicing and maintenance. • The APU is mounted with support struts. That provide

vertical and horizontal stability and vibration isolation.• Fish poles are used to remove the APU. • Air supply to the APU is through an aircraft mounted inlet

door and plenum chamber. • The fire loop is attached to the airframe provides for fire

protection. • A drain manifold consisting of a forward, middle, aft drain.

provides a means for draining fluid overboard.

What is the location and purpose of the ECU and panels that control the APU?

• ECU - a full-authority, digital electronic control, located in the aft cargo compartment, next to the aft cargo door.

Installation and Interface Summ

• APU Master Switch - is located on the overhead panel (P5-4). The APU master switch initiates APU Start and Stop sequences, controls the airplane inlet door, controls the fuel boost pump (optional), and controls the APU fuel valve.

• APU Indication Panel - located on the overhead panel (P5-4). It has four lights to indicate a problem to the operator for maintenance, low oil pressure, fault and overspeed.

• APU Bleed Valve Switch - located on the overhead panel (P5-10). It contains a two position switch; Off & On.

• APU Generator Switches - located on the overhead panel (P5-3). The switches give manual control for APU generator power source selection.

• APU Ground Control Panel - located in the right wheel well, on the aft bulkhead, allows the operator to stop the SPU from outside the airplane.

Notes:

ary Page 2-36

• APU Fire Handle Switch - located on the aft electrical panel (P8). It allows the operator to discharge the APU fire bottle.

What are the conditions for the Ready-to-Load, Duct Pressurization, Environmental Control System, and Main Engine Start Modes?

Ready to Load mode:

- Speed >95% plus 2 seconds- Bleed Air switch is OFF.

Duct Pressurization mode:

- Speed >95% plus 2 seconds- Bleed Air switch ON- LMES, RMES, LECS and RECS signals are false- Altitude <17,000 feet

Environmental Control System (ECS) mode:

- Speed is >95% plus 2 seconds. - Bleed Air Switch ON.- LMES and RMES signals are false.- LECS and RECS signal signals (2 pack) are true- Altitude <17,000 feet

MES mode of operation conditions:

- Speed >95% plus 2 seconds.- Bleed air switch is ON- Either LMES or RMES is true- Altitude <17,000 feet

What is the start sequence of events for the APU?• Battery switch ON• APU switch to the Start position • 0% speed, the ECU energizes the starter-generator and

ignition circuit• 7% speed, the fuel solenoid valve opens


• 34% speed, the low oil pressure light (P5) goes out• 60% speed, the ignition unit de-energizes• 70% speed, the starter-generator de-energizes• 95% + 2 seconds, the APU can supply electrical and

pneumatic power• 100% speed, full speed

- >106%, overspeed shutdown is initiated

What is the normal shutdown sequence of events? Explain the cooldown cycle.

• APU switch placed to ‘OFF’ position- 28 vdc ON signal removed from ECU- ECU receives the OFF signal- RTL signal is removed- 60 second cool-down period starts

• At 30% speed, the APU air inlet door starts to close (closes immediately for APU fire).

• At less than 7% speed, an APU restart can be initiated.

Notes:

ary Page 2-37


During cool down, the ECU:• Removes the ready-to-load signal and closes the bleed air

valve• Closes the inlet guide vanes (22 degrees)• Opens the surge control valve and de-energizes the starter

generator• Starts the 60 second timer

What are the conditions that would cause a protective shutdown?

Protective Shutdowns: (Fault Light ON)• APU fire • Fuel shutoff valve not in commanded position• Critical ECU failure • High oil temperature• Inlet door not in commanded position• Loss of DC power • Loss of both EGT signals• No acceleration; No flame• No speed signal • Oil temperature or inlet air temperature sensor failure

(Need to included in graphic?)• Overtemperature • Reverse flow (load compressor)• Under speed• APU inlet overheat and Generator filter clogged

Overspeed Light ON• Fuel control unit solenoid failure; Loss of overspeed

protection; Overspeed of more than 106% rpm


Low Oil Pressure Light ON• Low oil pressure;

Maintenance light ONFailed oil quantity switch; Low oil quantity; Start generatorshorted rotating diode

Notes:

ary Page 2-38


CHAPTER 3—ELECTRONIC CONTROL UNIT OPERATION

AND INTERROGATION

OBJECTIVES

After completing classroom discussion, you should be able to:• Identify the inputs and outputs to the ECU.• Explain the main functions of the electronic control unit

(ECU): start sequencing, speed governing, load sequencing, shutdown sequencing.

• Describe the purpose of each APU menu page.

Electronic Control Unit Operation and Interrogation Objec

Notes:

tives Page 3-1


OVERVIEW

The 131-9B APU uses a computer based electronic control unit(ECU) designed to control and provide an interface with the air-craft and subsystems.

The ECU incorporates a built-in-test-equipment (BITE) featurethat ensures safe operation of the APU. The ECB interface to theaircraft includes hardware discrete signals and a AeronauticalRadio. Inc. (ARINC) 429 communication system.

Inputs to the ECU are:• ARINC 429 Low-Speed Receiver Environmental Control

System (ECS)• ARINC 429 Low-Speed Receiver Generator Control Unit

(GCU)• ARINC 429 Low-Speed Receiver Central Fault Display

System• Data memory module (DMM)• Line replaceable units (LRU)

Electronic Control Unit Operation and Interrogation overv

Notes:

iew Page 3-2

ATM717-010Electronic Control Unit (ECU)

Electronic Control Unit (ECU)

ATM717.01009/02

Electronic Control Unit(Aft Cargo Compartment)

Electronic Control Unit Operation and Interrogation overview Page 3-3


ECU INTERFACE

The ECU input/output diagram shows the discrete and analoginput command signals received by the ECU from the aircraft andthe discrete and analog output signals produced by the ECU.

Input SignalsInput signals represent the commands from the flight deck con-trol panels, ECU essential pin, inlet door switches, and aircraftsensors and switches.

Output SignalsOutput signals are produced by the ECU and are used to controlthe operation of aircraft indicators.

Electronic Control Unit Operation and Interrogation ECU In

Notes:

terface Page 3-4

ATM717-060ECU Interface

LOP SWITCH SPEED SENSOR 2SPEED SENSOR 1

TOTAL PRESSURE SENSORDELTA PRESSURE SENSORBLEED AIR VALVE OPEN CMDBLEED AIR VALVE POSITION SWITCHINLET TEMPERATURE (T2) SENSOR

SCV T/MSCV LVDT PRIMARYLVDT SECONDARY

VA

CONTROL DISPLAYUNIT (CDU)

OIL LEVEL “ADD”OIL LEVEL “LOQ”OIL TEMP SENSORRESOLVER EXC

RESOLVER SINERESOLVER COSINEFCU T/MFUEL SHUTOFF VALVE

FUEL TEMPERATURE

INLET PRESS. (P2 ) SENSORIGV T/MIGV LVDT PRIMARYMA LVDT SECONDARYV

IGNITIONEGT #1 AND #2SCU BITE #1SCU BITE #2SCU BITE #3

SCU BITE #4

PERSONALCOMPUTER

DATA MEMORY MODULE

READY-TO-LOAD (RTL)READY-TO-LOAD (RTL)

APU FUEL S0V/AIR INLET DOOR OPENAPU FUEL SHUTOFF VALVE/AIR INLET DOOR CLOSE

AIR INLET DOOR POSITION SWITCH POWER ELECTRONIC

CONTROL

UNIT

FIRE (COCKPIT)FIRE (REMOTE)

FIRE (AUTOMATIC DETECTORS)

BLEED-AIR-SWITCHAIRPLANE SIGNATURE #1

AIRPLANE SIGNATURE #2AIR/GROUND

L ECS PACK VALVE COMMANDR ECS PACK VALVE COMMAND

LEFT MES COMMANDRIGHT MES COMMAND

ESSENTIAL/NON ESSENTIALAIR INLET DOOR OPEN

AIR INLET DOOR NOT OPEN

OFFON

START

FROMMAIN

BATTERY

LOAD SHED

OFFONSTART

LOP

FAULT

EGT METER

OVERSPEEDMAINTENANCE

ARINC 429

28-VOLT POWER

RS 422

ECU Interface

ATM717.06009/02

Electronic Control Unit Operation and Interrogation ECU Interface Page 3-5


ECU FUNCTIONS

The ECU inputs are used to control the following:• Start sequence• Speed governing• Load sequencing• Shutdown sequence

Start SequenceThe APU starts automatically after placing the APU Master switchto “START”. The ECU controls the ignition and fuel automaticallyas required for ambient conditions.

During pre-start Built-In-Test-Equipment (BITE), if a failure isdetected that would critically affect APU operation, the ECU inhib-its starting of the APU until the failure is resolved. The failure isstored in the ECU and the APU FAULT indicator is illuminated onthe APU control panel.

Speed GoverningExhaust gas temperature and engine speed are continuouslymonitored by the ECU. Once on-speed, the ECU maintains enginespeed at 48,800 RPM (±1.0%).

Load SequencingThe ECU regulates the APU pneumatic output by sensing the APUEGT and comparing this to a predetermined schedule within theECU. Bleed extraction is reduced to prevent an overtemperaturecondition.

ShutdownThe ECU shuts down the APU if engine speed exceeds 106% orEGT exceeds 1175F (635C).

Electronic Control Unit Operation and Interrogation ECU Fu

The ECU has the authority to shut down the APU when BITE indi-cates that continued APU operation might cause damage. Uponrequest, the ECU reports all APU fault data to the CDU. Thisallows troubleshooting of APU fault data.

Notes:

nctions Page 3-6

ATM717-069ECU Functions

• Pre-Start Built-In-Test-Equipment

• Automatic Start Control

• Speed Control within 1 percent rpm

• Protective Shutdown capability

• Start Inhibit capability

• Fault storage

• Fault reporting to the Control Display Unit (CDU)

ECU Functions

ATM717.06909/02

Electronic Control Unit Operation and Interrogation ECU Functions Page 3-7


CONTROL DISPLAY UNIT (CDU)

The APU indicating data can be viewed on the Control Display Unit(CDU), of which there are two (2) on the forward electronicspanel of the cockpit, if 115v ac power is available on the aircraft.

Accessing CDU Information • On IDENT page, push line select key 6L (INDEX). The

INIT/REF/INDEX page displays.• Press key 6R (MAINT) and the MAINT BITE INDEX page

displays.• Press key 2R (APU) and the APU BITE MAIN MENU page

displays.

Selecting the APU Menu PagesFrom the APU BITE TEST MAIN MENU you can select one of sixAPU menu pages:

• Current status: shows currently active maintenance faults• Fault history: shows faults that cause the APU to shutdown

or abort a start.• Maintenance history: shows faults that turn on the MAINT

light on the P5 panel and faults that have no flight compartment indication.

• Ident/Config (DMM data included): shows APU serial number, hours of operation, number of starts, ECU part and serial number, ECU software version.

• Input monitoring: shows APU operating parameters to assist in fault isolation.

• Oil quantity: shows the APU oil level as either FULL, LOW or ADD.

Electronic Control Unit Operation and Interrogation Control Displa

Returning to the Main MenuPush the INDEX button to return to the Main Menu page from anyof the APU menu pages.

Notes:

y Unit (CDU) Page 3-8

ATM717-051Control Display Unit

1 2

3

Select: APU > Main Menu page

Select: MAINT >Select: < INDEX

MAINTENANCE HISTORY >

< CURRENT STATUS

APU BITE TESTMAIN MENU

1/1

< FAULT HISTORY

< IDENT/CONFIG

< INPUT MONITORING

< INDEX OIL QUANTITY >FMC DOWN LOAD >

APU >

FQIS >

ENGINES >

< INDEX

< CDS

< ADIRS

< A/T

< DFCS

< FMCS

MAINT BITE INDEX 1/1

< INDEX MAINT >

IRS NAV >

ALTN DEST >

NAV DATA >

< OFFSET

< APPROACH

< TAKE OFF

< PERF

< POS

< IDENT

INT / REF INDEX 1/1

737-700NAV DATAUAL 6820401

MODEL

OP PROGRAM548849-001

MAR18APR17/97APR18MAY17/97

SUPP DATA APR 17/97

ENG RATING18.5K

ACTIVE

IDENT 1/2

POS INIT >

MSG RECALL >

Control Display Unit (CDU)

ATM717.05109/02

Electronic Control Unit Operation and Interrogation Control Display Unit (CDU) Page 3-9


CURRENT STATUS PAGE

PurposeThe Current Status page displays currently active APU mainte-nance faults.

DescriptionThere are approximately 200 different APU faults. When the APUECU detects a maintenance fault, the active fault is stored in theECU memory. Each fault has an assigned maintenance messagecode. The maintenance message code is used with the Boeingmaintenance manual for corrective actions.


Notes:


ATM717-052Current Status Page

B

A

12

3

Displayed i f noother occurrenceshave happened

CURRENT STATUSUNKNOWN FLT DECK EFFECT MAINT MSG 49-71146EGT 1 THERMOCOUPLEDISAGREE WITH EGT 2

NO OTHER OCCURRENCES

A P U B I T E T E S T

CURRENT STATUSUNKNOWN FLT DECK EFFECT MAINT MSG 49-71146EGT 1 THERMOCOUPLEDISAGREE WITH EGT 2OTHER OCCURRENCES/STARTS1 2 11 31 99 200456 801 999

A P U B I T E T E S T 1 / 1

CURRENT STATUSUNKNOWN FLT DECK EFFECT MAINT MSG 49-71146EGT 1 THERMOCOUPLEDISAGREE WITH EGT 2RUN APU AND SELECT BLEEDAIR TO CONFIRM REPAIR

APU >

FQIS >

< INDEX

< CDS

< ADIRS

< A/T

< DFCS

< FMCS

MAINT BITE INDEX 1/1


OIL QUANTITY >

< CURRENT STATUS

< FAULT HISTORY

< IDENT/CONFIG

< INPUT MONITORING

< INDEX


1/1

< INDEX

FMC DOWN LOAD >

ENGINES >

OCCURRENCES >OTHER

< INDEX

< INDEX

Displayed i f otheroccurrenceshave happened

Press to seeAPU menuscreen

Press to seeCurrent Statusscreen

Press forOther Occurrencesscreen

Select APU

Current Status Page

Current Status Interrogation

Current Status Page

ATM717.05209/02



FAULT HISTORY PAGE

PurposeThe Fault History page displays faults that cause the APU to shut-down.

DescriptionOne fault displays per page. Each fault has an assigned mainte-nance message code. The maintenance message code is usedwith the Boeing maintenance manual for corrective actions.

A maximum of 99 shutdowns can be stored in Fault History. Toview the faults, push the NEXT PAGE button on the CDU.


Notes:


ATM717-053Fault History Page

1

2

A P U B I T E T E S T 1 / 1 1 A P U B I T E T E S T 2/ 1 1

< FAULT HISTORY FAULT LIGHT MAINT MSG 49-71146 EGT 1 THERMOCOUPLE MAINT MSG 49-71146 EGT 2 THERMOCOUPLE LOSS OF EGT SHUTDOWN DATE GMT STARTS OLD APR 10 1027 11


OIL QUANTITY >

< CURRENT STATUS

< FAULT HISTORY

< IDENT/CONFIG

< INPUT MONITORING

< INDEX


1/1

CURRENT STATUS >

OTHER OCCURENCES >

< FAULT HISTORY FAULT LIGHT MAINT MSG 49-41011 SEE FAULT ISOLATION MANUAL NO FLAME SHUTDOWN DATE GMT STARTS OLD APR 13 1149 1

CURRENT STATUS >

OTHER OCCURENCES >

Main Menu Page

Fault History Page 1 of 11 Fault History Page 2 of 11

NOTE:To move between pages,use the PREV/NEXT keyon the CDU

Press to ViewFault HistoryScreen/Displays

Fault History Page

ATM717.05309/02



MAINTENANCE HISTORY PAGE

PurposeThis Maintenance History page displays faults that either

• turn on the MAINT light located on the APU panel, or• have no flight deck indication.

DescriptionOne fault displays per page. To view additional faults, push theNEXT PAGE button on the CDU. Each fault has an assigned main-tenance message code. The maintenance message code is usedwith the Boeing maintenance manual for corrective actions.


Notes:


ATM717-054Maintenance History Page

1

2

Main Menu Page

< CURRENT STATUS

< IDENT/CONFIG

< INPUT MONITORING

< INDEX

APU BITE TEST MAIN MENU

1/

MAINTENANCE MESSAGEUNKNOWN FLT DECK EFFECTMAINT MSG 49-71146EGT 1 THERMOCOUPLEDISAGREES WITH EGT 2DATE GMT STARTS OLDAPR 13 1101 1

< INDEX < INDEX

CURRENT STATUS> S

OTHER OCCURRENCES>

MAINTENANCE MESSAGE

EGT 1 THERMOCOUPLEDISAGREES WITH EGT 2OTHER OCCURRENCES/STARTS

APU BITE TEST 1/20 APU BITE TEST 1/20

Press to ViewMaintenanceHistory Pages

Press to viewOther Occurrences

< FAULT HISTORY

OIL QUANTITY >

MAINTENANCE HISTORY>

Maintenance History Page Other Occurrences Page

UNKNOWN FLT DECK EFFECTMAINT MSG 49-71146

1 2 11 31 99 200

Maintenance History Page

ATM717.05409/02

1/1



INPUT MONITORING PAGE

PurposeThe Input Monitoring pages display the APU parameters.

DescriptionThis menu displays APU operating parameters in real time toassist the operator in APU fault isolation.

To display the next page of information, push the NEXT PAGE but-ton on the CDU.

Maintenance Tip• The parameters displayed on the Input Monitoring page

can be used to assess the APU health.• The basic parameters, EGT, speed, and inlet temperature

are readily available for reference.• This information is only available when the aircraft is on

the ground.


Notes:


ATM717-055Input Monitoring Page

Main Menu Page

1

< I N D E X

A P U B I T E T E S T 2/4INPUT MONITORING

OIL TEMPFUEL TEMPGENERATOR LOADSTART SWITCHAPU ON SWITCHAPU OFF SWITCHMES SWITCH(S)AIR/GROUNDLEFT PACKRIGHT PACK



77 C50 C

YES

NOOFF

LOW

54.0 KW

YES

OFF

LOW


< I N D E X

SPEEDEGTIGV POSITIONSCV POSITIONDELTA PRESSTOTAL PRESSINLET PRESSINLET TEMPFUEL TMCFUEL FLOW

100.0%440 C

89.5 DEG

38.3 PSIA14.4 PSIA

148 MA

45.8 DEG

4.9 PSID

10.2 C

231 PPH

BLEED COMMAND SWINLET DOOR OPENDOOR NOT FULL OPENFIRE COCKPITFIRE REMOTE HANDLEFIRE DETECTIONAIRPLANE MODELBLEED AIR VALVEFUEL VALVE CLOSEDFUEL VALVE OPEN

ONYES

NO

NO700

NO

NO

NO

OPEN

YES< I N D E X

READY TO LOADSTART COMMANDLOAD SHED COMMANDIGNITION COMMANDFUEL SOL COMMANDBLEED SOL COMMANDOVERSPD INDICATORFAULT INDICATORLOP INDICATORMAINT INDICATOR

YESNO

NO

YESNO

NO

NO

YES

NO

NO< I N D E X


OIL QUANTITY >

< CURRENT STATUS

< FAULT HISTORY

< IDENT/CONFIG

< INPUT MONITORING

< INDEX


1/1

Input Monitoring Page 2/4 Input Monitoring Page 4/4Input Monitoring Page 3/4

Input Monitoring Page 1/4

Press to viewInput MonitoringPages

Input Monitoring Page

ATM717.05509/02



IDENT/CONFIG PAGE

Data Memory Module (DMM)The Ident/Config page displays all data in the data memory mod-ule.

To display the Ident/Config data, press the NEXT PAGE button onthe CDU.

This menu shows the following items:• APU serial number• Hours of operation• Number of starts• ECU part number and serial number• ECU software version.


Notes:


ATM717-056IDENT/CONFIG Page

IDENT/CONFIG BITE Interrogation

Page 1

Page 2

1


< CURRENT STATUS


1/1

< FAULT HISTORY

< IDENT/CONFIG

< INPUT MONITORING

< INDEX OIL QUANTITY >

IDENT/CONIG 1/2APU BITE TEST

APU S/NAPU HOURS

APU CYCLESHOURS SINCEINSTALLATIONON AIRPLANE

P-0013552.44296

3552.4

ECU HW P/NECU S/N

2118966-03166B00001

< INDEX INSTALLATION >

IDENT/CONIG 2/2APU BITE TEST

ECU OPERATIONAL SW P/N4900-TUS-A00-01

< INDEX

DATA MEMORYMODULE >

Press to viewIDENT/CONFIG

screens

Note:Press thekeys on the CDU foradditional pages

PREV/NEXT

IDENT/CONFIG Page

ATM717.05609/02



OIL QUANTITY

PurposeThe Oil Quantity page displays the APU oil level. It shows eitherFULL, LOW or ADD.

DescriptionADD oil means approximately two quarts low.

LOW oil means there are two quarts left in the gearbox. TheMAINT light will illuminate when the low oil level is reached.


Notes:


ATM717-103Oil Quantity

APU BITE TESTOIL QUANTITY REPORT

OIL LEVEL AD DACTIVE FOR 2.5 HOURS

Oil Quantity

ATM717.10309/02

Low Oil QuantitySwitch

CDU

(INPUT/MONITORING MENU)



SUMMARY


• Identify the inputs and outputs to the ECU.• Explain the main functions of the electronic control unit

(ECU): start sequencing, speed governing, load sequencing, shutdown sequencing.

• Describe the purpose of each APU menu page.

What are the inputs and outputs to the ECU?Refer to the diagram on page 3-5.

What are the main functions of the electronic control unit?

Start SequenceThe APU starts automatically after placing the APU Master switchto “START”. The ECU controls the ignition and fuel automaticallyas required for ambient conditions.

During pre-start Built-In-Test-Equipment (BITE), if a failure isdetected that would critically affect APU operation, the ECU inhib-its starting of the APU until the failure is resolved. The failure isstored in the ECU and the APU FAULT indicator is illuminated onthe APU control panel.

Speed GoverningExhaust gas temperature and engine speed are continuouslymonitored by the ECU. Once on-speed, the ECU maintains enginespeed at 48,800 RPM (±1.0%).

Load SequencingThe ECU regulates the APU pneumatic output by sensing the APUEGT and comparing this to a predetermined schedule within the

Electronic Control Unit Operation and Interrogation Summ

ECU. Bleed extraction is reduced to prevent an overtemperaturecondition.

ShutdownThe ECU shuts down the APU if engine speed exceeds 106% orEGT exceeds 1175F (635C).

The ECU has the authority to shut down the APU when BITE indi-cates that continued APU operation might cause damage. Uponrequest, the ECU reports all APU fault data to the CDU. Thisallows troubleshooting of APU fault data.

Notes:

ary Page 3-22

What is the purpose of each of the six APU menu pages?• Current status: shows currently active maintenance faults• Fault history: shows faults that cause the APU to shutdown

or abort a start.• Maintenance history: shows faults that turn on the MAINT

light on the P5 panel and faults that have no flight compartment indication.

• Ident/Config (DMM data included): shows APU serial number, hours of operation, number of starts, ECU part and serial number, ECU software version.

• Input monitoring: shows APU operating parameters to assist in fault isolation.

• Oil quantity: shows the APU oil level as either FULL, LOW or ADD.


Notes:

ary Page 3-23



Notes:

ary Page 3-24


CHAPTER 4—THEORY OF OPERATION &

CONSTRUCTION

OBJECTIVES

Upon completion of this chapter, you will be able to:• Identify the major APU Sections.• Explain the basic operating cycle of the turbine engine.• Explain the effect of load compression on engine

operation.• Explain the effect of a surge on engine operation.• Explain the effect of a generator load on engine operation.• Explain how APU Temperature controls effects engine

operation.

Theory of Operation & Construction Objec

Notes:

tives Page 4-1


OVERVIEW

ConstructionThe APU is divided into three major sections:

• Power section• Load compressor section • Accessory gearbox section

Theory Of OperationThe APU is designed to provide:

• pneumatic power for main engine start (MES), and the environmental control system (ECS),

• shaft power to drive a customer furnished generator for the aircraft electrical system.

Both shaft and bleed loads are placed upon the APU during opera-tion. Temperature control is accomplished through sensor inputto the ECB.

Theory of Operation & Construction Overv

Notes:

iew Page 4-2

ATM717-002Main APU Engine Sections

Main APU Engine Sections

Gearbox Load Compressor Power SectionATM717.002

09/02

Theory of Operation & Construction Overview Page 4-3


MAIN APU ENGINE SECTIONS

The basic APU is comprised of three major sections:• Power section• Load compressor section • Accessory gearbox section

Power SectionThe power section drives the load compressor and accessorygearbox. It consists of a shaft with a single centrifugal impellerand a two-stage axial turbine all protected by a containmentstructure. There are also 10 fuel nozzles and a reverse flow annu-lar combustor.

Load CompressorThe load compressor consists of a single centrifugal impeller anda diffuser. Inlet air to the load compressor is controlled by inletguide vanes. The power section and load compressor impellersshare the same inlet plenum duct.

Accessory GearboxThe accessory gearbox is driven through a quill shaft by the highspeed torque of the power section. The gearbox contains a seriesof spur gears to drive the APU accessories. Accessories installedon the gearbox are the oil cooled generator, oil pump/fuel control,cooling fan and starter motor. The gearbox also serves as a reser-voir for the lubrication system.

Theory of Operation & Construction Main APU En

Notes:

gine Sections Page 4-4

ATM717-002Main APU Engine Sections

Main APU Engine Sections

Gearbox Load Compressor Power SectionATM717.002

09/02

Theory of Operation & Construction Main APU Engine Sections Page 4-5


BASIC OPERATING CYCLE

At the heart of the APU is a turbine engine that is similar in oper-ation to a jet engine, but it produces no thrust. The compressorand turbine are mounted on a common shaft. Initially turned by astarter, using electrical power, the compressor draws air throughthe air inlet raising its pressure, then passes it into the combustorwhere fuel is injected. The burning within the combustor raisesthe energy level of the air. The hot gases then pass through theturbine, which extracts as much energy as possible from the gasflow. The turbine converts the gas energy to rotational energy todrive the compressor. Even with no load applied, it is necessary toinject heat energy into the combustor by burning fuel to over-come the losses that occur within the compressor turbine, andother mechanical/aerodynamic drag.

The amount of fuel which the unit burns and the heat which isexpelled from the exhaust are indicators of engine health. Ascomponents wear or malfunctions occur, a rise in exhaust gastemperature and an increase in fuel consumption can occur.

Theory of Operation & Construction Basic Opera

Notes:

ting Cycle Page 4-6

ATM717-102Basic Operating Cycle

Basic Operating Cycle

ATM-717.102 (07/02)

Fuel

InletAir

Compressor

Combustor

Turbine

Theory of Operation & Construction Basic Operating Cycle Page 4-7


LOAD COMPRESSOR OPERATION

The APU supplies compressed air for air conditioning, and mainengine starting. This air is obtained by a second compressorcalled the load, or driven compressor. It is driven from an exten-sion of the power section compressor turbine shaft.

The load compressor takes air from the same inlet as the powersection compressor. It compresses it and supplies it to the aircraftthrough a load control valve. The load control valve shuts off theair flow from the load compressor when there is no demandplaced on the APU by the aircraft control system. The energyrequired to drive the load compressor is obtained from the turbineby burning more fuel in the combustor. As air is extracted fromthe load compressor, fuel flow and exhaust gas temperature rise.

The load compressor must provide the maximum amount of airflow that the aircraft will require. If there were no control overairflow, it would impose full load on the turbine and require a veryhigh fuel flow, whether or not the aircraft demanded air. Inletguide vanes between the compressor and the air inlet matchcompressor flow to the demand. Inlet guide vane position is con-trolled by the electronic control box in response to aircraftdemand. When there is no demand, the ECB closes the IGV's tothe lowest possible setting, so the load compressor imposes min-imum load on the power section. In this condition, the load con-trol valve is closed and all air is redirected through the surgecontrol valve. When the IGV's are at the minimum closed posi-tion, the unit is “ready-to-load”, which means the APU is run-ning on-speed, with bleed de-activated and the generator off.

Theory of Operation & Construction Load Compres

Notes:

sor Operation Page 4-8

ATM717-097Load Compressor OperationI

GVA

ECU

Load Compressor Operation

ATM-717-097 (09/02)

Bleed AirValve

LoadCompressor

Compressor Turbine

Air Intake

Combustor

Aircraft

DemandsFuel

Theory of Operation & Construction Load Compressor Operation Page 4-9


SURGE PROTECTION

Although the air conditioning system may be turned on in the air-plane, it may not be using as much air as the load compressorcan deliver. If the airflow from the compressor falls too far belowthe rate at which it enters through the IGV's, a back pressurecondition known as compressor stall can occur. A significant backpressure of the compressor results in a surge.

A surge control valve spills air that the compressor wants todeliver but the airplane cannot use, to protect the load compres-sor from a stall/surge condition. For any opening in the inlet guidevanes, there is a minimum amount of air that must be allowed toflow through the compressor. Actual flow is sensed by the flowsensor which through the ECB controls the position of a surgecontrol valve.

Theory of Operation & Construction Surge Pro

Notes:

tection Page 4-10

ATM717-098Surge Protection

EHSV

ECU

LVDT

ATM-717-098 (09/02)

Exhaust

SCV Control and Feedback

Signals

Diffuser

FuelSupply

IGV PositionAir Inlet Temperature

Pneumatic System Demands

FlowSensors

PT

DP

Load Compressor

AircraftDuct

SurgeControlValve

Surge Protection

Theory of Operation & Construction Surge Protection Page 4-11


GENERATOR AND ACCESSORIES

The APU drives the electrical generator mounted on the gearboxassembly. The gearbox in turn is driven from the power sectionthrough the common shaft as shown in the figure. Whether theAPU is bleeding air from the load compressor or taking electricalpower from the generator, each will impose a load on the powersection. As load is applied, the power section tends to slow down.The electronic control box senses the speed drop and providesmore fuel to the combustor. This results in an increase in thepower to match the load which helps maintain a constant speed.

Theory of Operation & Construction Generator and

Notes:

Accessories Page 4-12

ATM717-099Generator and Accessories

GCU

IGVA

ECU

PT

DP

Gearbox

Generator And Accessories

ATM-717-099 (09/02)

Gen

Speed

Starter

Lube andFuel

Clusters

SurgeControlValve

Bleed Air Valve

Fuel

Theory of Operation & Construction Generator and Accessories Page 4-13


APU TEMPERATURE CONTROL

As the combined loads of the generator and the load compressorare imposed on the power section, the speed governing functionof the ECB responds by increasing fuel flow. Under someextremely high combination loads or with significant deteriorationof the power section, the turbine trim temperatures limit will bereached. The trim limit is set below the maximum temperaturelimit of the turbines temperature to ensure long life.

The ECB monitors turbine temperature through a pair of dualthermocouples located in the turbine exhaust. When a loadchange results in a temperature higher than its setpoint, the ECBmoves the IGV’s toward a more closed position, reducing loadcompressor airflow, and thus reducing the load and its resultingturbine temperature.

Theory of Operation & Construction APU Tempera

Notes:

ture Control Page 4-14

ATM717-100APU Temperature ControlI

GVA

ECU

PT

DP

Gearbox

APU Temperature Control

ATM-717-100 (09/02)

Speed

Gen

Starter

Lube andFuel

Clusters

EGT

SurgeControlValve

Bleed AirValve

Exhaust

Fuel

Theory of Operation & Construction APU Temperature Control Page 4-15


SUMMARY


• Identify the major APU Sections.• Explain the basic operating cycle of the turbine engine.• Explain the effect of load compression on the engine

operation.• Explain the effect of a surge on the engine operation.• Explain the effect of a generator load on engine operation.• Explain how APU Temperature controls effects engine

operation.

What are the major APU sections?• Power section• Load compressor section • Accessory gearbox section

What is the basic operating cycle of the turbine engine?The compressor draws air through the air inlet raising its pres-sure, then passes it into the combustor where fuel is injected. Theburning within the combustor raises the energy level of the air.The hot gases then pass through the turbine, which extracts asmuch energy as possible from the gas flow. The turbine convertsthe gas energy to rotational energy to drive the compressor.

What is the effect of load compression on engine operation?

The load compressor must provide the maximum amount of airflow that the aircraft will require. If there were no control overairflow, it would impose full load on the turbine and require a veryhigh fuel flow, whether or not the aircraft demanded air. Inletguide vanes between the compressor and the air inlet matchcompressor flow to the demand. Inlet guide vane position is con-

Theory of Operation & Construction Summ

trolled by the electronic control box in response to aircraftdemand. As the IGVVs open, the load comp0ressor imposes aload on the power section which causes the APU to slow down.The ECB senses the speed drop and provides more fuel to bringthe APU up to 100% speed.

What is the effect of generator load on engine operation?

The APU drives the electrical generator mounted on the gearboxassembly. The gearbox in turn is driven from the power sectionthrough the common shaft as shown in the figure. Whether theAPU is bleeding air from the load compressor or taking electricalpower from the generator, each will impose a load on the powersection. As load is applied, the power section tends to slow down.The electronic control box senses the speed drop and providesmore fuel to the combustor. This results in an increase in thepower to match the load which helps maintain a constant speed.

Notes:

ary Page 4-16

How does APU Temperature control effects engine operation?

The ECB monitors turbine temperature through a pair of dualthermocouples located in the turbine exhaust. When a loadchange results in a temperature higher than its setpoint, the ECBmoves the IGV’s toward a more closed position, reducing loadcompressor airflow, and thus reducing the load and its resultingturbine temperature.


Notes:

ary Page 4-17



Notes:

ary Page 4-18


CHAPTER 5—LUBRICATION SYSTEM

OBJECTIVES

Upon completion of this training section, you will be able to:• Locate and identify lubrication system LRUs.• Identify the purpose and operation of the lubrication

system components.• Trace the flow of oil through the lubrication system.• Identify possible malfunctions related to the lubrication

system.

Lubrication System Objec

Notes:

tives Page 5-1


OVERVIEW

The lubrication system provides oil to lubricate, clean, and coolthe gears, bearings and shafts of the power section, load com-pressor and gearbox. The system consists of the supply, scav-enge, pressure, temperature and vent systems.

There are two main areas in the APU that require lubrication. Atthe front is the accessory gearbox that houses gears, shafts andthe duplex ball bearing that supports the front end of the rotatinggroup. The other area is the roller bearing on the turbine powersection.

Lubrication System Overv

Notes:

iew Page 5-2

ATM717-101Lubrication System Overview

Lubrication System Overview

ExhaustGenerator

LubeModule

BypassValve

Gearbox

ScavengeReturns toGearbox

Air/OilSeparator

GearboxVent Line

OilCooler

ScavengePumpReturnScreen

InletScreen

Oil Level

PowerSection

OilJetsForGear-boxBear-ings

ATM-717-101 (09/02)

Lubrication System Overview Page 5-3


POWER SECTION TURBINE BEARING CAVITY

The flow of oil through the power section turbine bearing cavity isas follows:

• The lubricating oil enters the rear turbine cavity through a tube to lubricate the rear turbine roller-bearing.

• When the oil has reached the bearing cavity, it circulates and migrates down into the lower part of the cavity.

• In the lower cavity, it is picked up by the scavenge tube and drawn back by a scavenge pump into the gearbox.

Fault Indication:Scavenge pump failure will leave oil in the turbine cavity longerthan intended. This will result in black oil and possible oil temper-ature auto-shutdowns.

Smoke out of the APU exhaust could indicate that the aft gaskethas failed on the turbine cover.

Lubrication System Power Section Turb

Notes:

ine Bearing Cavity Page 5-4

ATM717-035Power Section Turbine Seal Cavity

Power Section Turbine Seal Cavity

ATM717.03509/02

ScavengeOut Port

TurbineRoller

Bearing

Metal Rotor Seal

Carbon SealOil InPort

Lubrication System Power Section Turbine Bearing Cavity Page 5-5


FORWARD BEARING AND SEAL

Air discharged from the load compressor is fed into the cabin andvarious pneumatic components. This requires that extra protec-tion for oil leakage be incorporated for the forward bearing.

• At the forward end of the rotating group, the duplex ball bearing is separated from the load compressor by a carbon face seal.

• The carbon face seal is backed up with an air buffered labyrinth seal.

• This extra protection for oil leakage is required because Compressor discharge air is fed into the area between the carbon face seal and the labyrinth seal through covered passages.

• If any oil should get past the carbon face seal, it would be forced back toward the gearbox rather than entering the load compressor.

Maintenance TipA seal leakage witness port is located on the lower part of theload compressor to check if the seal is in fact leaking.

If the APU is suspected of being the source of odors, mainte-nance personnel should troubleshoot for a reason.

Lubrication System Forward Bear

Notes:

ing and Seal Page 5-6

ATM717-036Forward Bearing and Seal

Forward Bearing and Seal

ATM717.03609/02

Compressor Scroll

LoadCompressor

ImpellerSeal

WitnessTest Port

DuplexBall

Bearing

Lubrication System Forward Bearing and Seal Page 5-7


LUBRICATION SYSTEM COMPONENTS

The lubrication system components include the following:• Lubrication Module

- Lube Supply Filter- Generator Scavenge Filter- High Oil Temperature Sensor

• Oil Cooler• Gearbox/Oil Sump• Low Oil Quantity Switch• Magnetic Chip Collector/Drain Plug• Temperature Control Valve• Low Oil Pressure Switch• Air/Oil Separator

Lubrication System Lubrication Syste

Notes:

m Components Page 5-8

ATM717-082Lubrication System Components

Lubrication System Components

ATM-717.082 (09/02)

• Lubrication Module

• Lube Supply Filter

• Generator Scavenge Filter

• High Oil Temperature Sensor

• Oil Cooler

• Gearbox / Oil Sump

• Low Oil Quantity Switch

• Magnetic Chip Collector/Drain Plug

• Temperature Control Valve

• Low Oil Pressure Switch

• Air/Oil Separator

Lubrication System Lubrication System Components Page 5-9


LUBRICATION MODULE

Identification and LocationThe lubrication module mounts directly to the gearcase.

Purpose and InterfaceThe lubrication module is a self-contained unit, that provideslubrication and scavenge functions to the starter/generator, gear-box, and main shaft bearings.

Functional DescriptionThe lubrication module incorporates a three-element ge-rotorpressure pump, a three-element ge-rotor scavenge pump forclearing oil from the generator, and a single element ge-rotorscavenge pump, 7 in all, for clearing oil from the APU turbinebearing cavity.

To enhance cold starting, ceramic ge-rotor rings are used inthe 131-9[B] configuration. The ceramic rings have a lower ther-mal coefficient of expansion than that of the steel ge-rotor ele-ments. This allows a larger cold clearance between the ge-rotorand ring to minimize cold temperature viscous drag withoutsacrificing performance when operating with hot oil.

The filters, and indicators are accessible with the lube moduleinstalled on the APU and are removed and installed with standardtools.

The module incorporates a seal plate to provide sealing featuresat each oil passageway. This eliminates the need for externaltubes at the lube module.

Pressure Regulator A pressure regulator (67.5±7 psi) maintains a constant lubesupply pressure to the engine and starter/generator which isinstalled on the lube module.


Ultimate Relief Valve AssemblyThe ultimate relief valve assembly (240±40 psi) is locatedinside the lube module. It’s responsibility is to prevent over pres-surization of the oil system.

The Lubrication Module is an LRU.

Notes:


ATM717-030Lubrication Module

Lubrication Module

ATM717.03009/02

Captive Bolts

Oil PressureTest Port

LUBE

SCAV



LUBE SUPPLY FILTER

The oil filter elements are throw-away types contained in ahouseing that is screwed into the Lube Module housing. The 2 fil-ters are rated at 10 micron nominal and 25 microns absolute.The collapse pressure of the filter exceeds 350 psid.

Purpose and InterfaceThe oil filter elements remove contaminants from the oil as itreturns to the oil storage area.

Functional DescriptionThe Lube filter housing is equipped with a DP indicator but-ton. Should the lube filter become contaminated, the differentialpressure (DP) indicator pops out at 35±5 psid.

If additional contamination buildup occurs, the filter bypass valveallows unfiltered oil to bypass the filter at a differential pressureof 60±10 psid.

A thermal lockout feature is incorporated in the assembly so theDP feature is inoperative when oil temperature is less than 70°F.

GENERATOR SCAVENGE FILTER

The generator scavenge filter and filter bypass valve areidentical to but entirely separate from the lubrication oil filter.This part of the lube system contains an electrical impendingbypass switch.

The purpose of the generator switch is to eliminate and mini-mize damage to the APU if the starter/generator should malfunc-tion by shutting down the APU before generator debris cancirculate in the lubrication system.


When the bypass switch activates, a signal is sent to the ECU.There are three conditions that must be met before theECU will shutdown the APU:

1. Oil temperature >100°F2. For >5 seconds3. Aircraft must be on ground

NOTE: If a signal is generated in flight, the ECU will log a maintenance fault to the APU maintenance page of the CDU.

Notes:


ATM717-031Oil Filter Elements

Oil Filter Elements

ATM717.03109/02

Lube Module

LubeReservoir

Filter Element

Starter/GeneratorScavenge

Filter Element

BypassSwitch

RetainingRing Groove

LUBE

SCAV



HIGH OIL TEMPERATURE SENSOR

Identification and LocationThe high oil temperature sensor is located in the lubricationmodule.

The high oil temperature sensor is used for high oil temperatureindication/protection.

Functional Description• Normal operating oil temperature is approximately 200-

210°F on a standard sea level day.• A high oil temperature shutdown will occur when APU

speed is >95%, oil temperature is >290°F, plus 10 seconds.

• The sensor is checked during Pre-start, Monitor and Self-test.

The high oil temperature sensor is an LRU.

Fault Indication: Oil Temp shutdowns• Sensor failure results in the APU would not have HOT

protection• Low oil quantity• Dirty oil cooler assembly• Thermostatic bypass valve failure• Lube pump failure (pressure and scavenge)


Notes:


ATM717-034High Oil Temperature Sensor

High Oil Temperature Sensor

ATM717.03409/02

High OilTemperature

Sensor

Lube Module



OIL COOLER

Identification and LocationThe oil cooler is a aluminum air/oil heat exchanger of the two-pass-folded crossflow type with the oil flowing perpendicular tothe direction of airflow twice.

Purpose and InterfaceThe oil cooler removes the waste heat in the lubrication oil andcarries it away from the APU and the starter/generator.

Functional DescriptionCooling air for the oil cooler is supplied by the cooling educatorduct from the tail of the airplane. The high speed exhaust flowfrom the APU forms a low pressure area. This low pressure areapulls cooler air from outside through the eductor duct to the APUcompartment. This low pressure area also pulls air continuouslyfrom the compartment through the oil cooler and out through theexhaust.

Maintenance TipThe cooler air side is easily cleaned of ingested contaminants withcommonly available shop equipment.

NOTE: This new design has eliminated the need for a oil cooling fan on the 131-9B APU.


Notes:


ATM717-076Oil Cooler

Oil Cooler

ATM717.076 (09/02)

Oil Cooler

Cooler ReturnTube

CoolerSupplyTube

CaptiveBolt

Heat Shield

APU CompartmentAirflow Exit



GEARBOX / OIL SUMP

Identification and LocationThe gearbox/oil sump is mounted to the front of the load com-pressor housing.

All accessories are mounted on the front of the gearbox assemblyto maximize maintainability.

Purpose and InterfaceThe gearbox/oil sump drives the APU accessories, including theStarter/Generator. It is also the reservoir for the lubrication sys-tem.

Functional DescriptionThe gearbox is designed as a module and is removable from theAPU, leaving all gears, bearings, and seals in place.

The gearbox is considered a HOT gearbox, because the oil in itcomes from the working APU before oil cooling occurs.

Oil capacity is 8.8 quarts (8.4 liters), and the ADD point is 4.0quarts. The G/B holds approx. 5.7 quarts, while the lines andcooler hold approx. 3.8 quarts.

Maintenance TipPeriodically check the end of the vent tube (turbine exhaust) forcarbon buildup.


NOTE: Maximum oil consumption allowed is approximately 8 cc’s per hour.

Fault Indication:A plugged vent line will cause oil pressure to increase, oil con-sumption, gearbox cracking, and oil being pushed through theseals.

Smoke out the APU exhaust and smells in bleed air will benoticed.

The gearbox assembly is a Shop Replaceable Unit (SRU).

Notes:


ATM717-027Gearbox/Oil Sump

Gearbox/Oil Sump

ATM717.02709/02

Air/OilSeparator

MagneticDrain Plug

Bypass PressureDifferential

Switch

Lube Filter

GeneratorScavenge

Filter

Oil FillPort



LOW OIL QUANTITY SWITCH

Identification and Location The low oil quantity switch is located on the gearbox next to theoil fill port.

Purpose and InterfaceThe low oil quantity switch indicates when a low oil conditionoccurs and sends a signal to the CDU.

Functional Description• The low oil quantity switch uses four reed -switches (one

full, two add, and one low) to ensure reliable nuisance-free indication. The quantity indicated is not dynamic, it is checked upon start-up.

• The low quantity switches are actuated by a float/samarium cobalt magnet combination that moves depending on oil level. The float has strategically placed slots to prevent trapping of air by the float.

• The CDU displays the APU oil quantity with a FULL, ADD, or LOW indication, under the “input monitoring” screen.

NOTE: Approximately 70 hours (maximum allowed oil consumption) of APU operation remain once the ADD indication is seen on the CDU.


Notes:


ATM717-028Low Oil Quantity Switch

APU BITE TESTOIL QUANTITY REPORT

OIL LEVEL AD DACTIVE FOR 2.5 HOURS

Low Oil Quantity Switch

ATM717.02809/02

Low Oil QuantitySwitch

CDU

(INPUT/MONITORING MENU)



MAGNETIC CHIP COLLECTOR AND DRAIN PLUG

Identification and LocationThe magnetic chip collector is a threaded metal plug, withwrenching flats on one end, and a magnet on the opposite end.

Purpose and InterfaceThe magnetic chip collector detects metallic particles in the oil.The check valve on the drain plug prevents oil loss when inspect-ing the chip collector.

The magnetic chip collector and drain plug assembly are an LRU.

Maintenance TipRefer to applicable maintenance manual for the meaning andmaintenance action for particles that may appear.

If any of the filters or chip detector is contaminated, change thecontaminated oil, filter element(s) and recheck after 15 minutesof APU operation. If further contamination is seen, refer to appro-priate maintenance manual for disposition.

NOTE: If you see metal particles on the magnetic element, examine the engine to find the cause and quantity of the damage.


Notes:


ATM717-029Magnetic Chip Collector/Drain Plug

Magnetic Chip Collector/Drain Plug

ATM717.029R109/02

Magnetic Chip Collector

Magnet

Plug

RetainingClamp

Check Valve

Gearbox

Oil Filler Housingwith Strainer

Oil Fill Cap



TEMPERATURE CONTROL VALVE

Identification and LocationThe temperature control valve is remotely located on the gearboxand is attached by a seal plate.

Purpose and InterfaceThe temperature control valve allows the flow of oil to either flowthrough or bypass the cooler, depending on oil temperature.

Functional DescriptionThe control valve allows oil to bypass the oil cooler at tempera-tures less than 140°F. Oil flows through the cooler when temper-atures are greater than 170°F.

The valve opens to allow oil to bypass the oil cooler when:• it is internally restrictive to oil flow.• the oil temperature is less then 140° F.• there is a differential pressure of (50 psid) across the oil

cooler assembly.

If the temperature control valve fails to close, H.O.T. shutdownswould most likely occur.

NOTE: This feature helps the cold APU start by not putting an extra strain on the APU starter system.


Notes:


ATM717-032Temperature Control Valve

Temperature Control Valve

ATM717.03209/02

Poppet Valve

OilIn

OilOut

ToOil

Cooler

FromOil

Cooler

Oil CoolerSupply Tube

Oil CoolerReturn Tube

ThermostaticBypassValve

Diaghragm

ExpansionElement

TemperatureSensitive

Compound



LOW OIL PRESSURE (LOP) SWITCH

Identification and LocationThe oil pressure switch is located in the gearcase, in the oil flowto the engine bearings.

The LOP switch is a normally closed electrical, open-with-pres-sure switch.

Purpose and InterfaceThe low oil pressure switch provides protection against low oilpressure conditions.

Functional DescriptionA open pressure switch position is checked in Pre-Start andSelf-test ECU modes only and not during APU operation.

On pre-start BIT, the LOP switch has failed if the APU speed is lessthan 7% and the switch is showing electrically open.

An Oil Pressure auto-shutdown will occur if RPM >95%, oil pres-sure <35±5 psi for 20 seconds.

The APU would start but have no LOP protection if found tobe bad during Pre-Start BIT

The Oil Pressure switch is an LRU.


FAULT INDICATION: LOP AUTO-SHUTDOWNPossible causes:

• Oil filters clogged.• Insufficient oil quantity.• Over servicing of the oil.• Mixing of incompatible oils.• Sludge buildup in APU internal cored passageways.

Notes:


ATM717-033Low Oil Pressure Switch

Low Oil Pressure Switch

ATM717.03309/02

Low OilPressure Switch



AIR-OIL SEPARATOR

Identification and LocationThe oil-air separator is located right above and to the left of thelubrication module.

Purpose and InterfaceIn scavenging the oil from the bearing cavities, some air will bedrawn with it since the scavenge pump capacity is greater thanthe oil flow to the turbine cavity. The scavenged air/oil mixture issaturated with oil mist, and must separated. The gearcase mustbe vented to prevent the buildup of pressure.

The air-oil separator removes the air from the oil mist as itreturns to the gearbox reservoir.

Functional DescriptionAir and oil come into the gearbox from the air buffered seals. Oilis then slung to the sides and re-deposited into the sump. The airthen vents overboard through a hard-line tubing going back tothe APU exhaust duct.

Maintenance Tip• The stationary air-oil carbon seal is removable and

replaceable without gearbox disassembly. The rotor, however is not.

• The rotating group can be turned by using a 5/16 socket to turn the air/oil separator, after the cover has been removed.

The Air-Oil Separator assembly is not an LRU.


Notes:


ATM717-037Air/Oil Separator (Top View)

Air/Oil Separator (Top View)

ATM717.03709/02

Air/OilSeparator

GearboxVent toExhaust

Vent toExhaust

Pipe

Metal Rotor

Carbon Face Seal

Gearbox

Air/Oil SeparatorCompoundIdler Gear

Air/OilIn



OIL SERVICING PROVISIONS

The following synthetic lubricants are approved by Honeywell.

Type 1 per MIL-LP7808:Aeroshell Turbine Oil 390

Brayco 880

BP Aero Turbine Oil 15

Castrol 3C

Castrol 325

Type II per MIL-L-23699:Castrol 500

Exxon or Esso Turbine Oil 2380

Exxon or Esso Turbine Oil 85

Exxon 2197

Hatcol 3611

Mobil Jet Oil II

Mobil Jet Oil 254

Royco 899

Royco or Aeroshell Turbine Oil 500

Royco or Aeroshell Turbine Oil 555

Lubrication System Oil Servicing

NOTE: The use of non-approved lubricants or the mixing of brands and types of lubricants may cause foaming, and “Low Oil Pressure” auto shutdowns.

NOTE: Information concerning oil change intervals and a table listing the approved oil brands and type are provided in the appropriate maintenance manual.

Notes:

Provisions Page 5-30

Notes

Lubrication System Oil Servicing Provisions Page 5-31


LUBRICATION SYSTEM FLOW

The following text describes the flow of oil through the engine.• Oil is drawn from the reservoir through a protective screen

into the 3-element supply pump. After being discharged from the pump the oil passes through a pressure regulator/relief valve which maintains constant system pressure throughout APU operation.

• The oil then flows to the thermostatic/pressure relief valve on the oil cooler.- If oil is cold, it bypasses the cooler and is distributed to

the engine and components.- If the oil is hot, it passes through the cooler to remove

excess heat.• Oil then flow to the lube filter and is distributed to the

bearings, gears, and generator. Oil is distributed through internal passages and external lines to the various parts of the APU.- As it flows to the turbine bearing, a pressure switch

and temperature sensor monitor system pressure and temperature. If pressure is too low or temperature is too high, the APU is shut down.

• The generator is scavenged by elements in the lube module. Oil returning from the generator first passes through in-line screens. The pumps discharge oil into a generator scavenge filter and empties it into the reservoir. The generator scavenge filter has an impending bypass switch that causes the APU to shutdown if the filter becomes restricted.

• Oil from the forward bearings and gearbox returns to the reservoir by gravity. The turbine bearing area is scavenged by a single pump element. Oil passes through an inlet screen, through the pump and into the reservoir.

Lubrication System Lubrication S

• Servicing provisions are on the reservoir case, as well as a sight gage.- There is an oil level sensor that signals the ECU. - In the bottom of the gearbox is a magnetic drain plug

that collects any metal particles for viewing in case of a suspected problem.

• Air and oil are separated by an air/oil separator. • The reservoir is vented to the exhaust section which

prevents over-pressurization of the reservoir during APU operation.

Notes:

ystem Flow Page 5-32

ATM717-026Lubrication System Flow

Lube Pump RegulatedLube Pump InletGearcase Vent AirTurbine ScavengeScavenge Pump DischargeGen. Scavenge Pump InletHigh Pressure Discharge

Lubrication System Flow

LubePump

Elements (3)

MagneticDrain Plug

Oil LevelSight Glass

LubeInlet

ScreenFillPort

Low Oil Quantity Switch

Gen. ScavengeElements (3)

TurbineScavengeElement

PressureRegulating/Relief Valve

Low OilPressureSwitch

Bearings

FCU

Oil Cooler

TemperatureControl Valve

OilTemp

Sensor

LubeFilter

Delta P Indicator Delta P

ImpendingBypassSwitch

GeneratorScavenge

Filter

To TailpipeVent

To Turbine Cavity

From Turbine Cavity

ATM717.02609/02

Lubrication System Lubrication System Flow Page 5-33


SUMMARY


• Locate and identify lubrication system LRUs• Identify the purpose and operation of the lubrication

system components.• Trace the flow of oil through the lubrication system.• Explain oil servicing provisions.

What are the lubrication system LRUs?• Lubrication Module

- Lube Supply Filter- Generator Scavenge Filter- High Oil Temperature Sensor

• Oil Cooler• Gearbox/Oil Sump• Low Oil Quantity Switch• Magnetic Chip Collector/Drain Plug• Temperature Control Valve• Low Oil Pressure Switch• Air/Oil Separator

What is the purpose of each LRU?• Lubrication Module: provides lubrication and scavenge

functions to the starter/generator, gearbox, and main shaft bearings.

• Oil Filter Elements: oil filter elements remove contaminants from the oil as it returns to the oil storage area.

• Low Oil Pressure Switch: provides protection against low oil pressure conditions.

Lubrication System Summ

• Lube Supply Filter: removes contaminants from the oil as it returns to the oil storage area.

• Oil Cooler: removes the waste heat in the lubrication oil and carries it away from the APU and the starter/generator.

• Gearbox/Oil Sump: drives the APU accessories and is also the reservoir for the lubrication system.

• Low Oil Quantity Switch: indicates when a low oil condition occurs and sends a signal to the CDU.

• Magnetic Chip Collector/Drain Plug: detects metallic particles in the oil.

• Temperature Control Valve: allows the flow of oil to either flow through or bypass the cooler, depending on oil temperature.

• High Oil Temperature Sensor: is used for high oil temperature indication/protection.

Notes:

ary Page 5-34

• Air/Oil Separator: removes the air from the oil mist as it returns to the gearbox reservoir.

What is the flow of oil through the lubrication system?• Oil is drawn from the reservoir through a protective screen

into the 3-element supply pump. After being discharged from the pump the oil passes through a pressure regulator/relief valve which maintains constant system pressure throughout APU operation.

• The oil then flows to the thermostatic/pressure relief valve on the oil cooler.- If oil is cold, it bypasses the cooler and is distributed to

the engine and components.- If the oil is hot, it passes through the cooler to remove

excess heat.• Oil then flow to the lube filter and is distributed to the

bearings, gears, and generator. Oil is distributed through internal passages and external lines to the various parts of the APU.- As it flows to the turbine bearing, a pressure switch

and temperature sensor monitor system pressure and temperature. If pressure is too low or temperature is too high, the APU is shut down.

• The generator is scavenged by elements in the lube module. Oil returning from the generator first passes through in-line screens. The pumps discharge oil into a generator scavenge filter and empties it into the reservoir. The generator scavenge filter has an impending bypass switch that causes the APU to shutdown if the filter becomes restricted.

• Oil from the forward bearings and gearbox returns to the reservoir by gravity. The turbine bearing area is scavenged by a single pump element. Oil passes through an inlet screen, through the pump and into the reservoir.


• Servicing provisions are on the reservoir case, as well as a sight gage.- There is an oil level sensor that signals the ECU. - In the bottom of the gearbox is a magnetic drain plug

that collects any metal particles for viewing in case of a suspected problem.

• Air and oil are separated by an air/oil separator. • The reservoir is vented to the exhaust section which

prevents over-pressurization of the reservoir during APU operation.

1

Notes:

ary Page 5-35



Notes:

ary Page 5-36


CHAPTER 6— FUEL SYSTEM

OBJECTIVES

Upon completion of this training section, you will be able to:• Locate and identify fuel system LRUs• Identify the purpose and operation of the fuel system

components.• Trace the flow of fuel through the fuel system.• Identify possible malfunctions related to the fuel system.

Fuel System Objec

Notes:

tives Page 6-1


FUEL SYSTEM OVERVIEW

The APU fuel system is a fully automatic system controlled by theECU.

StartingDuring start, the fuel system provides the correct amount of fuelto support combustion and provides for smooth acceleration ofthe engine to full rated speed.

On-SpeedOnce rated speed is reached, fuel flow is modulated to meet thedemands of varying pneumatic and electrical loads while main-taining a constant speed.

Fuel SupplyFor proper operation, the aircraft system furnishes a stableamount of fuel at a pressure between 0 and 55 PSIG. The sys-tem also requires 24 VDC (range of 14-30 volts) power.

ShutdownDuring shutdown fuel flow is stopped by the fuel shutoff solenoid.

Fuel System Fuel System

Notes:

Overview Page 6-2

ATM717-024Fuel System Overview

Fuel System Overview

ATM717.02409/02

FuelControl Unit

FuelManifold

CombustorDrain Valve

Fuel FlowDivider

Fuel System Fuel System Overview Page 6-3


FUEL SYSTEM COMPONENTS

The Fuel System consists of the following components:• Fuel Control Unit• Fuel Filters• Fuel Metering Assembly• Flow Divider Assembly

- Flow Divider Solenoid• Fuel Manifolds & Fuel Nozzles• Fuel Shutoff Solenoid• IGV Actuator Pressure Regulating Valve• Plenum Drain Valve• APU Drain Manifold

Fuel System Fuel System C

Notes:

omponents Page 6-4

ATM717-084Fuel System Components

Fuel System Components

ATM-717-084 (09/02)

• Fuel Control Unit

• Fuel Filters

• Fuel Metering Assembly

• Flow Divider Assembly

• Flow Divider Solenoid

• Fuel Manifolds & Fuel Nozzles

• Fuel Shutoff Solenoid

• IGV Actuator Pressure Regulating Valve

• Plenum Drain Valve

• APU Drain Manifold

Fuel System Fuel System Components Page 6-5


FUEL CONTROL UNIT (FCU)

Identification and LocationThe FCU consists of the following:

• a high pressure fuel pump• seals• filters• fuel torque motor• flow meter• temperature sensor• fuel shutoff solenoid

The entire pump and control assembly is attached to the lubrica-tion module by means of a quick release V-band clamp.

Purpose and InterfaceThe fuel control unit supplies metered fuel to the flow divider inproportion to the signal received from the ECU.

Functional DescriptionThe FCU:

• is driven by an oil lubricated spline drive shaft.

• has a single electrical connector for fuel shutoff solenoid, fuel torquemotor feedback, and temperature.

• is designed to operate at supply pressures as low as 5 psi above true vapor pressure.

The gear pump is a positive displacement type.

Protection for the fuel pump system is provided by a safety reliefvalve (1150 PSI) (internal) which relieves pump pressure on allFCU shutdowns.


Maintenance TipFuel or oil seepage from the drain port is an indication that theseals are leaking internally. This condition warrants FCU replace-ment.

There is no “clogged filter” indicator.

Notes:

omponents Page 6-6

ATM717-014Fuel Control Unit

Fuel Control Unit

ATM717.01409/02

Fuel ControlUnit (FCU)

Lube ModuleAlignment Pin

Fuel SupplyTube Assembly



Fault IndicationFCU performance problems will cause the following protectiveshutdowns:

• No Flame• No Accel• Overtemperature• Overspeed• Underspeed

Starting Fuel Trim Schedule:

Table 1:

RPM Temperature

0 1750°F

10.3 1750°F

13 1650°F

20 1600°F

41 1520°F

51.2 1425°F

61.5 1425°F

71.7 1320°F

82 1200°F

90.2 1100°F

95 1070°F

98.4 1050°F


Notes:

omponents Page 6-8

ATM717-014Fuel Control Unit

Fuel Control Unit

ATM717.01409/02

Fuel ControlUnit (FCU)

Lube ModuleAlignment Pin




FUEL FILTERS

Identification and LocationThe fuel filters include:

• a large capacity, replaceable element located at the inlet to the FCU (10-micron inlet filter).

• protective metal screens installed at the pump discharge (high pressure, non-bypassing type), shutoff valve, torque motor and flow divider valve locations.

Purpose and InterfaceThe filters trap normal fuel pump wear debris. The entire pumpdischarge flow passes through the filter.

Functional DescriptionThe metal screens installed at the pump discharge, shutoff valve,torque motor and flow divider valve locations are rated at 40microns nominal and 65 microns absolute.

The fuel filter housing and filter element are LRUs.

Maintenance Tip• The high pressure pump screen is replaceable without

removing the FCU.• The screens located at the fuel shutoff solenoid and flow

divider are of the same type.• All seals, filters, and internal components are compatible

with JP-4, JP-8, and Jet A fuels, and applicable additives.


NOTE: Recommended filter change is 3,500 APU hours or 3 years, whichever comes first.

NOTE: Fuel filters are designed to trap normal fuel pump wear debris.

Notes:

omponents Page 6-10

ATM717-015Fuel Filters

Fuel Filters

ATM717.01509/02

Filter Element

Filter Cap



FUEL METERING ASSEMBLY

Identification and LocationThe fuel metering assembly is located internally in the FCU.

Purpose and InterfaceThe ECU and fuel metering assembly control the APU start andacceleration.

Functional DescriptionThe fuel metering assembly meters fuel flow using a direct actingmetering valve (torque-motor). The metered fuel filter is a func-tion of ECU supplied current.

An increase in current increases fuel flow by enlarging the meter-ing area. A constant pressure drop across the torque motor iskept by the differential pressure regulator which senses fuel pres-sure upstream and downstream of the torque motor andbypasses excess fuel back to the pump inlet to maintain the dif-ferential pressure.

After leaving the torque motor, the metered flow passes throughthe integral flow meter and pressurizing valve, which keeps aminimum pressure down stream of the metering valve and tofeedback the flowrate amount to the ECU.

The fuel then travels through the fuel shutoff solenoid and out tothe fuel flow divider.

NOTE: Whenever a protective shutdown is initiated, the current to the torque-motor is automatically removed.

The Fuel Control Torque-motor is an integral part of the FCU andis not line adjustable or replaceable


Torque-Motor Current Versus Fuel Flow:

Table 6-1:

Milliampere lbs/hr

0 0

20 16

35 28

50 50

100 140

150 235

200 330

250 425

Notes:

omponents Page 6-12

ATM717-016Fuel Metering (Torque-Motor)Fuel Metering

Outlet Port

Fuel Inlet Port

Clevis

FCU TorquemotorMetering Valve

Fuel Metering (Torque-Motor)

ATM717.01611/02



FUEL FLOW DIVIDER & FLOW DIVIDER SOLENOID

Identification and LocationThe fuel flow divider is on the left side of the APU near the com-bustion chamber.

These are the main fuel flow divider components:

• Ball check valve• Inlet filter• Flow divider solenoid

PurposeThe fuel flow divider directs fuel to the primary and secondarymanifolds.

Functional DescriptionThe fuel flow divider gives fuel to the primary manifold duringstart of the APU.

At 25-40 percent speed or approximately 120 psi, the check valveinside the T fitting opens and supplies fuel to the secondary main-ifold, unless the flow divider solenoid is closed.

The fuel flow divider solenoid in normally open (de-energized). Itmakes sure fuel flows to the secondary manifold at the correcttime.

The ECU energizes the solenoid closed in the following conditions.

• During start from 7 to 30% speed.• Above 25,000 feet.• T2 less than 55°F


The flow divider solenoid also improves start capability in coldweather.

The ECU uses P2, T2, and speed signals to control the fuel flowdivider solenoid valve.

The flow divider assembly is considered an LRU.

Maintenance TipIf flow divider sequencing is incorrect, No Acceleration, No Flame,Overtemperature and Underspeed auto-shutdowns could occurwith NO faulty LRUs in ECU memory.

Notes:

omponents Page 6-14

ATM717-018Fuel Flow Assembly

Fuel Flow Assembly

ATM717.01809/02

Combustor

Primary Fuel FlowFlow Divider

Solenoid

Fuel FlowDivider

Fuel FlowDivider Secondary

Fuel Flow

Fuel Nozzles

Secondary

Fuel NozzlesPrimary



FUEL MANIFOLDS & FUEL NOZZLES

Identification and LocationThe two manifolds (primary and secondary) consist of ten (10)dual-orifice atomizers equally spaced and mounted on the com-bustor plenum.

Purpose and InterfaceThe primary and secondary fuel manifolds (2) route fuel to thefuel injector nozzles (10 dual orifice nozzles).

The fuel nozzles inject metered fuel into the combustor.

Functional Description• Fuel for ignition and initial acceleration is supplied by the

primary portion of the atomizers.• The fuel inlet has a filter screen to prevent contaminants

from entering the spray tip. An indexing pin positions the air shroud on the atomizer, and ensures accurate atomizer assembly in the engine.

• A hard coat is applied to the air shroud where it contacts the combustor to reduce wear.

• Combustor inlet air is introduced through the shroud to sweep the face of the spray tip to prevent carbon formation.

Maintenance TipThe combustor is bolted down to allow for removal and replace-ment of all fuel nozzles at the same time.

The inlet screens are removable for cleaning or replacement.


Notes:

omponents Page 6-16

ATM717-019Fuel Manifolds & Fuel Nozzles

Fuel Manifolds & Fuel Nozzles

ATM717.01909/02

FuelNozzle

Primary Secondary

Screens

Air Shroud

Nozzle Tip

Primary FuelManifold

SecondaryFuel Manifold

LocatingPin



FUEL SHUTOFF SOLENOID

Identification and LocationThe fuel shutoff solenoid is a three-way, normally closed, twoposition poppet valve. It is an integral part of the FCU and assuch, is not considered an LRU.

Purpose and InterfaceThe fuel shutoff solenoid directs metered fuel to the fuel flowdivider.

The fuel shutoff solenoid is energized by the ECU.

Functional DescriptionWhen the fuel shutoff solenoid is energized by the ECU, meteredfuel is directed through it and to the fuel flow divider.

When the solenoid is de-energized, APU operation is terminated(for either a protective or normal shutdown).

NOTE: If the fuel shutoff solenoid fails mechanically to open at approximately 7% speed, a No Flame auto-shutdown occurs and NO failed LRUs will be in ECU memory.

NOTE: If the fuel shutoff solenoid leaks fuel to the flow divider before approximately 7% speed, torching,

NOTE: Overtemperature or No Flame auto-shutdowns will occur without failed LRUs in ECU memory.


Notes:

omponents Page 6-18

ATM717-021Fuel Shutoff Solenoid

Fuel Shutoff Solenoid

ATM717.02111/02

Solenoid



IGV ACTUATOR PRESSURE REGULATING VALVE

Identification and LocationThe actuator pressure regulator is an integral part of the FCU.

Purpose and InterfaceThe pressure regulating valve provides the hydraulic pressureused to activate the inlet guide vane assembly and the surge con-trol valve.

Functional DescriptionThe valve maintains a fuel pressure of 250±25 psig to the inletof the IGV Actuator and Surge Control valve.

If pressure regulation is low or high, the Inlet Guide Vane Actua-tor could be faulted because it did not extend or retract to its pro-grammed position.

NOTE: The regulator is not line adjustable and is not considered to be an LRU.


Notes:

omponents Page 6-20

ATM717-022IGVA Pressure Regulator Valve

IGVA Pressure Regulator Valve

ATM717.02209/02

IGV Actuator/Surge Valve

Return

IGV Actuator/Surge Valve

Supply

ActuatorPressureRegulator

LubeModule

FuelPump

FuelSupply

Gearbox

LEGENDFUEL IN (LOW PRESSURE)PUMP DISCHARGE (HIGH PRESSURE)METERED FUELREGULATED PRESSUREACTUATOR RETURN

LRU FuelDrain TubeAssembly

IGV ReturnTube Assembly

IGV SupplyTube Assembly




PLENUM DRAIN VALVE

Identification and LocationThe plenum drain valve is located at the lowest point in the ple-num.

Purpose and InterfaceA plenum drain valve (orificed) ensures complete drainage of fuelthat may accumulate in the combustor and turbine plenum fol-lowing an unsuccessful light off attempt (not attributed to fuel).Draining the excess fuel prevents a possible hot or torching start.

Maintenance Tip• An arrow on the valve body points in the direction of fuel

flow toward the overboard drain line.• Check to see if the valve is clean and unobstructed on a

scheduled basis. • Refer to the Boeing maintenance manual for more details.

NOTE: The valve is always open whether the APU is operating or not.


Notes:

omponents Page 6-22

ATM717-023Plenum Drain Valve

Plenum Drain Valve

ATM717.02309/02

CombustorDrain Valve

(Orificed Tube)



APU DRAIN MANIFOLD

Identification and LocationThere are four drains on the APU. Three of the drains are over-board drains that consist of two fuel drains and one oil drain. Thedrains are customer interfaced by the drain mast installedbeneath the inlet duct.

One drain (inlet duct) is internal to the airplane compartment.

Which is the forward, middle and aft drains.

Purpose and InterfaceThe forward drain detects degraded seal performance in the fuelcontrol unit (FCU), inlet guide vane (IGV) actuator, and surgecontrol valve (SCV) actuator.

The middle drain is used for detecting degraded load compres-sor main shaft seal performance.

The aft drain is used for disposing of excess fuel in the event ofan aborted start, and is also a means of draining the airplanemuffler.

Maintenance TipDuring normal operations, NO fuel is discharged from the aftdrain.

The leakage rates shown are acceptable for normal engine opera-tion after a minimum of five minutes at sustained APU speed.

Unit/Item Limit Max. Tolerance/Remarks:• Fuel/Lube Module cavity: 3 drops per minute allowed at

the FCU/lube moduledrain tell-tale witness drain.


• Inlet Guide Vane Actuator: 3 drops/minute allowed at the IGVA tell-tale witness drain.

• Oil Consumption: 8 cc/hr• Surge Control Valve (SCV): 3 drops/minute at the tell-

tale minute witness drain.A daily visual inspection check for leakage at the APU drain mani-fold should be done by maintenance personnel.

Leakage more than the limits or a sudden leakage increase, mustbe monitored frequently and/or necessary maintenance sched-uled.

Notes:

omponents Page 6-24

ATM717-059APU Drain Manifold

APU Drain Manifold

ATM717.05909/02

Load CompressorSeal Drain

Combustor Case/Eductor, Muffler

DrainFCU/SCV/IGVA

Drain

BOTTOM VIEW

FWD



FUEL SYSTEM FLOW

The aircraft fuel system supplies the APU with low-pressure fuel.• Fuel is passed through an inlet filter on the fuel control

unit.• After the filter, the fuel is sent to a two-stage pump and

actuator supply regulator. This fuel is used to operate the inlet guide vane and surge control valve actuators.

• After passing through the pump, the fuel is sent to a high-pressure fuel filter and the torque motor (TM). The torque motor is controlled by signals from the ECU.

• Fuel leaving the TM is now metered fuel which is used to operate the APU. The metered fuel flows past a temperature sensor and integral flow divider. The resulting signals are used to adjust flow rates for starting the APU in cold conditions and altitude.

• The fuel then flows to the fuel shutoff solenoid. - When energized at 7% speed, it allows fuel to flow to

the flow divider and flow divider solenoid. - When the ECU receives an OFF signal and the APU has

completed a cool-down cycle, the fuel shutoff solenoid closes and the APU shuts down.

• The flow divider and flow divider solenoid distribute the fuel between primary flow and secondary fuel manifolds.- Primary flow is for starting the APU and secondary flow

is for acceleration and on-speed operating conditions. - The flow divider solenoid is controlled by the ECU.

• Attached to the manifolds are 10 fuel nozzles. The nozzles inject fuel into the combustion chamber for APU operation.

• On the bottom of the outer combustion case is a plenum drain valve. It is used to drain the excess fuel from the combustion chamber in case of a no start condition.

Fuel System Fuel Syste

Notes:

m Flow Page 6-26

ATM717-017Fuel System Flow

Fuel System Flow

ATM717.01709/02

ActuatorReturn

ElectricalConnector

MeteringModule

ActuatorSupply

ActuatorPressureRegulator

P2Pressure

Tap

FlowmeterResolver

RTD

FlowmeterPressurizing

Valve

3-WayShutoff

SolenoidN.C.

MeteredFlow

Discharge

Orifice

DifferentialPressureRegulator

Bypass Bleed(Double Screened)

FuelSupply

Inlet FuelFilter Element

High PressureFuel Pump

SealDrain

LubeModule

PumpDriveSpline

ShaftSeals

PumpReliefValve

HighPressureFuel Filter

LEGENDFuel In (Low Pressure)

Pump Discharge(High Pressure)

Metered Fuel

Regulated Pressure

Actuator Return

Fuel System Fuel System Flow Page 6-27

SUMMARY


• Locate and identify fuel system LRUs• Identify the purpose and operation of the fuel system

components.• Trace the flow of fuel through the fuel system.• Identify possible malfunctions related to the fuel system.

What are the fuel system LRUs?• Fuel Control Unit• Fuel Filters• Flow Divider Assembly

- Flow Divider Solenoid• Fuel Manifolds & Fuel Nozzles• Plenum Drain Valve• APU Drain Manifold

What is the purpose of each LRU?• Fuel Control Unit: supplies metered fuel to the flow

divider in proportion to the signal received from the ECU.• Fuel Filters: trap normal fuel pump wear debris. The

entire pump discharge flow passes through the filter.• Fuel Metering Assembly: through the ECU controls APU

start and acceleration.• Flow Divider Assembly/Flow Divider Solenoid: distributes

the fuel between primary flow and secondary fuel manifolds.

• Fuel Manifolds & Fuel Nozzles: the manifolds route fuel to the fuel injector nozzles; the fuel nozzles inject metered fuel into the combustor.

• Fuel Shutoff Solenoid: directs metered fuel to the fuel flow divider.

• IGV Actuator Pressure Regulating Valve: provides the hydraulic pressure used to activate the inlet guide vane assembly and the surge control valve.

Fuel System Summ

• Plenum Drain Valve: ensures complete drainage of fuel that may accumulate in the combustor and turbine plenum during an unsuccessful start.

• APU Drain Manifold: - The forward drain detects degraded seal perfor-

mance in the fuel control unit (FCU), inlet guide vane (IGV) actuator, and surge control valve (SCV) actuator.

- The middle drain is used for detecting degraded load compressor main shaft seal performance.

- The aft drain is used for disposing of excess fuel in the event of an aborted start, and is also a means of drain-ing the airplane muffler.

Describe the flow of fuel through the engine.• Fuel is passed through an inlet filter on the fuel control

unit.• After the filter, the fuel is sent to a two-stage pump and

actuator supply regulator. This fuel is used to operate the inlet guide vane and surge control valve actuators.

Notes:

ary Page 6-28

• After passing through the pump, the fuel is sent to a high-pressure fuel filter and the torque motor (TM). The torque motor is controlled by signals from the ECU.

• Fuel leaving the TM is now metered fuel which is used to operate the APU. The metered fuel flows past a temperature sensor and integral flow divider. The resulting signals are used to adjust flow rates for starting the APU in cold conditions and altitude.

• The fuel then flows to the fuel shutoff solenoid. - When energized at 7% speed, it allows fuel to flow to

the flow divider and flow divider solenoid. - When the ECU receives an OFF signal and the APU has

completed a cool-down cycle, the fuel shutoff solenoid closes and the APU shuts down.

• The flow divider and flow divider solenoid distribute the fuel between primary flow and secondary fuel manifolds.- Primary flow is for starting the APU and secondary flow

is for acceleration and on-speed operating conditions. - The flow divider solenoid is controlled by the ECU.

• Attached to the manifolds are 10 fuel nozzles. The nozzles inject fuel into the combustion chamber for APU operation.

• On the bottom of the outer combustion case is a plenum drain valve. It is used to drain the excess fuel from the combustion chamber in case of a no start condition.

Fuel System Summ

Notes:

ary Page 6-29


Fuel System Summ

Notes:

ary Page 6-30


CHAPTER 7—PNEUMATIC SYSTEM

OBJECTIVES

Upon completion of this training section, the student will:

• Locate and identify the pneumatic system LRUs.• Identify the purpose and operation of the pneumatic

system components.• Identify possible malfunctions related to the pneumatic

system.

Pneumatic System Objec

Notes:

tives Page 7-1


OVERVIEW

The pneumatic system provides compressed air to the (undervarying load conditions) to prevent surging of the APU load com-pressor.

The pneumatic system is comprised of a:• PT Sensor• P2 Sensor• DP Sensor• Inlet guide vane actuator (IGV)• Inlet temperature sensor (T2)• Surge Control Valve

Pneumatic System Overv

Notes:

iew Page 7-2

ATM717-039Pneumatic System Schematic

LEGEND

Pneumatic System Schematic

ATM717.03909/02

Inlet Temperature Sensor (T2)

PowerSection

Inlet Air Flow

LVDT

DPSensor

PTSensor

Opening Piston

ClosingSpring

AirFlow

ToECU

SCV

TM

ToECU

Fuel Out

Fuel In

Gearcase Vent AirElectrical SignalLoad CompressorBleed AirAPU CompartmentCooling AirAPU Inlet AirExhaust Air

Air/OilSeparator

Fuel In

FuelOut

OilCooler

IGVAInlet PressureSensor (P2) Oil In

Oil Out

CompartmentAir

LoadCompressor

Surge Bleed Air Exhaust

Total PressureProbe (PT)

ExhaustEductor

VisualPositionIndicator

Closed

Closed

Open Open

PositionSwitch

Open

Closed

Open

Close

ECUBAV

Solenoid

Static PressureSensing Ports

Pneumatic System Overview Page 7-3


PNEUMATIC SYSTEM COMPONENTS

The pneumatic system consists of:• Surge Control Valve• Flow Sensor Assembly

- PT Sensor- DP Sensor- P2 Sensor

• Inlet Temperature Sensor• Bleed Air Valve• Inlet Guide Vane Assembly

Pneumatic System Pneumatic Syste

Notes:


ATM717-085Pneumatic System Components

Pneumatic System Components

ATM717.085 (09/02)

• Surge Control Valve

• Flow Sensor Assembly

• PT Sensor

• DP Sensor

• P2 Sensor

• Flow Sensor Probes

• Inlet Temperature Sensor

• Bleed Air Valve

• Inlet Guide Vane Assembly

Pneumatic System Pneumatic System Components Page 7-5


SURGE CONTROL VALVE (SCV)

Identification and LocationThe surge control valve (SCV) is a butterfly type valve. The SCVactuator is on the top of the valve. A two-stage servo valve con-trols the actuator. A visual indicator on the valve gives the posi-tion of the valve.

The SCV is located in the surge bleed duct on the right side of theAPU.

Purpose and InterfaceThe ECU controls a torque motor on the servo valve. This motorsends high pressure fuel from the APU fuel system to open orclose the surge control valve. The valve moves between 10degrees (open) and 90 degrees (closed). A linear variable differ-ential transformer (LVDT) supplies valve position feedback to theECU.

The surge control valve (SCV) releases air from the load compres-sor. The SCV makes sure there is a minimum flow of air throughthe load compressor. This prevents a surge. If a surge doesoccur, the SCV opens to help the load compressor recover.

The surge margin set point is the minimum quantity of correctedair that should flow through the load compressor to prevent loadcompressor surge. The ECU calculates the corrected airflow andthe surge margin set point. The corrected airflow is the quantityof air that flows through the load compressor. The ECU uses totalpressure (PT) and differential pressure (DP) to calculate the cor-rected airflow. The ECU uses the following inputs to calculate thesurge margin set point:

• Inlet temperature (T2)• IGV position• Bleed mode


• Air/ground

Air that flows through the surge control valve goes overboardthrough the exhaust duct.

Notes:


ATM717-040Surge Control Valve

Surge Control Valve

ATM717.04011/02

Surge ControlValve



FLOW SENSOR ASSEMBLY

Identification and LocationThe flow sensor assembly (P2, PT and DP) consists of staticpressure taps located in the load compressor diffuser and a totalpressure probe (basically a shaped tube) in the duct between thediffuser and bleed air valve.

Purpose and InterfaceAll 3 pressure sensors (transducers) (P2, PT, and DP) changepressure into an electrical signal and transmit these values to theECU to control:

• fuel scheduling during APU starts• surge control valve operations• inlet guide vane positions

The total pressure sensor (PT) measures load compressor dis-charge pressure.

The delta pressure sensor (DP) measures the difference betweentotal and static pressures.

The ambient pressure sensor (P2) measures inlet pressure.

NOTE: The flow sensors real-time data can be viewed on the flightdeck CDU panel, under APU BITE TEST.

NOTE: The ECU compensates for any possible drift in the Delta P sensor zero point by adding or subtracting a compensating offset if a non zero Delta P is detected in Pre-Start BIT.


Notes:


ATM717-042Flow Sensor Assembly

REAL TIME PARAMETERS 1/4

SPEEDEGTIGV POSITIONSCV POSITIONDELTA PRESSTOTAL PRESSINLET PRESSINLET TEMPFUEL TMCFUEL FLOW<INDEX

000.0 % 20.5 C 00.0 DEG 10.0 DEG 0.0 PSID 14.7 PSIA 14.7 PSIA 20.5 C 0.0 MA 00.0 PPH

APU BITE TEST

Flow Sensor Assembly

ATM717.04209/02

Pressure AmbientSensor (P2)

Delta PressureSensor ( ∆P)

CDU

Pressure TotalSensor (PT)



Functional Description• The P2 and PT sensing probes sample the air

pressure developed by the load compressor and route to the electrical sensors. The sensors translate the pressure input into an electrical signal that is transmitted to the ECU.

• The ECU interprets the signals from the PT and DP transducers, as well as the altitude input (P2) and inlet guide vane position (LVDT).

• After interpreting these parameters, the ECU provides the correct command signal to the Surge Control valve to modulate it more open or closed in order to provide a constant airflow through the compressor during all loading conditions.

PT and P2 signals are sent to the flow sensor manifoldwhich directs the pressure to the total and differential pressuresensors.

In the event of a failure, the ECU allows safe electric-load opera-tion by holding the SCV open and the IGVs closed. This gives pri-ority to electric (shaft load) operation at the expense of bleed loadin the event of a surge system malfunction.


Notes:


ATM717-077Flow Sensor Schematic

REAL TIME PARAMETERS 1/4SPEEDEGT

IGV POSITIONSCV POSITIONDELTA PRESSTOTAL PRESSINLET PRESSINLET TEMPFUEL TMCFUEL FLOW

<INDEX

000.0 % 20.5 C

00.0 DEG 10.0 DEG 0.0 PSID 14.7 PSIA

14.7 PSIA 20.5 C

0.0 MA 00.0 PPH

CDU

5 R5 R

APU Bite Test

Flow Sensor Schematic

ATM717.07709/02

(LVDT)

BleedAir

Valve

One-wayCheckValve

SurgeControlValve

PT Transducer

DP Transducer

To APUExhaust

Pipe

To AircraftBleed Duct

PressureTotalProbe

PressureStaticProbe

TM

LoadCompressor

Diffuser

Load CompressorDischarge Air



INLET TEMPERATURE SENSOR (T2)

Identification and LocationThe inlet temperature sensor (T2) is a resistance temperaturetype detector located on the bottom of the APU compressor ple-num.

Purpose and InterfaceThe inlet temperature sensor supplies inlet air temperature data(T2) to the ECU. This data is used for:

• Fuel Control (during APU starting)• IGV Control (during bleed air usage)• SCV Control (>95% APU speed)• EGT trim schedule (ECS and MES modes)

Functional Description• When air temperature into the APU inlet compressor

changes, the resistance changes in the sensor.• The ECU senses this change in resistance and adjusts the

APU operation due to that temperature change.

NOTE: The ECU also sends the temperature to the control display unit (CDU) in the flight compartment where it can be viewed by the operator.

The Inlet Temperature Sensor is an LRU.


Notes:


ATM717-044Inlet Temperature Sensor (T2)

APU B ITE TESTREAL TIME PARAMETERS 1/4


100.0 % 650 C 80.1 DEG 90.0 DEG 6.2 PSID 50.5 PSIA 13.8 PSIA 20.5 C 139 MA 249 PPH

Inlet Temperature Sensor (T2)

ATM717.04409/02

T2 Sensor(Temperature Ambient) ECU

CDU



BLEED AIR VALVE (BAV)

Identification and LocationThe bleed air valve is a pneumatically actuated, open and closedbutterfly valve located between the bleed air duct and compressordischarge duct.

PurposeThe Bleed Air Valve (BAV) controls bleed airflow to the airplane.

Functional Description• The BAV is normally in the closed position. Load

compressor bleed air, controlled by a solenoid, provides the power for valve opening.

• The ECU energizes the solenoid mechanism to open the valve when the APU bleed switch (P5 Pneumatic Control Panel) is in the ON position and the APU speed is greater than 95 percent.


Notes:


ATM717-043Bleed Air Valve

Bleed Air Valve

ATM717.04311/02

MechanicalPositionIndicator

Bleed AirValve

CLOSED

OP

EN

OP

EN



INLET GUIDE VANE (IGV) ASSEMBLY

Identification and LocationThe IGV assembly consists of 16 vanes located radially at the loadcompressor inlet.

Purpose and InterfaceThe IGV assembly controls the air flow to the load compressor.The IGV consists of the:

• IGV Actuator• Linear Variable Differential Transformer (LVDT)

Functional DescriptionThe vanes are supported at one end and are driven by gear seg-ments attached to each vane. The gear segments mesh with acylindrical rack to synchronize vane position.

During an APU start, the IGVs are held at 22 degrees for altitudesabove 25,000 feet. If altitude is below 15,000 feet, the IGVs areheld at 15 degrees up to 60 percent speed and then opened to 22degrees.

Bleed Air Demands:• No bleed• Duct Pressurization• Main Engine Start• Air Conditioning System

Pneumatic System Inlet Guide Vane

NOTE: IGV position is a function of P2, T2 and load demand, and is controlled by the ECU.

IGV ActuatorThe IGV actuator regulates the load compressor discharge air bypositioning the vanes in response to an electrical signal from theECU.

LVDTThe Linear Variable Differential Transformer (LVDT) provides con-tinuous IGV actuator position during APU operation. The LVDT isinternally mounted to the IGV actuator and is powered by theECU.

• The IGV position is seen on the CDU/APU Input Monitoring page.

Notes:

(IGV) Assembly Page 7-16

ATM717-004Inlet Guide Vane (IGV) Assembly

Inlet Guide Vane (IGV) Assembly

ATM717.00409/02

IGV AccessCover

Linkage

Vanes (16)

Bolts (3)Attachment

Bolt

IGV Actuator

L/C BoroscopePort

Pneumatic System Inlet Guide Vane (IGV) Assembly Page 7-17


SUMMARY


• Locate and identify pneumatic system LRUs• Identify the purpose and operation of the pneumatic

system components.• Identify possible malfunctions related to the pneumatic

system.

What are the pneumatic system LRUs?• Surge Control Valve• Flow Sensor Assembly

- PT Sensor- DP Sensor- P2 Sensor

• Inlet Temperature Sensor• Bleed Air Valve• Inlet Guide Vane Assembly

What is the purpose of each LRU?• Surge Control Valve: prevents a surge by releasing air

from the load compressor to ensure there is a minimum flow of air through the load compressor.

• Flow Sensor Assembly- PT Sensor: measures load compressor discharge pres-

sure.- DP Sensor: measures the difference between total and

static pressures.- P2 Sensor: measures inlet pressure.

• Inlet Temperature Sensor: supplies inlet air temperature data to the ECU.

Pneumatic System Summ

• Bleed Air Valve: controls bleed airflow to the airplane.• Inlet Guide Vane Assembly: controls air flow to the load

compressor.

Notes:

ary Page 7-18


CHAPTER 8—ELECTRICAL ACCESSORIES

OBJECTIVES

Upon completion of this training section, you will be able to:• Locate and identify the electrical accessory LRUs.• Explain the purpose of each electrical accessory

component.• Identify possible causes of electrical accessory

malfunctions.

Electrical Accessories Objec

Notes:

tives Page 8-1


OVERVIEW

The APU electrical control system consists of electrical accessoriesthat work in conjunction with the ECU. Together the electricalaccessories and ECU sense and control the functions required tosafely and reliably start and monitor the APU.

Electrical Accessories Overv

Notes:

iew Page 8-2

ATM717-Electrical Accessories Overview

Electrical Accessories Overview Page 8-3


ELECTRICAL ACCESSORIES COMPONENTS

Electrical accessories components include:• Start Power Unit• Start Converter Unit (SCU)• Electronic Control Unit (See Chapter 3)• APU Starter-Generator• Ignition Unit• EGT Thermocouples• Speed Sensor• Data Memory Module (DMM)

Electrical Accessories Electrical Accesso

Notes:

ries Components Page 8-4

ATM717-086Electrical Accessory Components

Electrical Accessory Components

ATM717-086 (09/02)

• Start Power Unit• Start Converter Unit• Electronic Control Unit• Starter-Generator• Ignition Unit• EGT Thermocouple Rakes• Speed Sensor (Monopole)• Data Memory Module (DMM)

Electrical Accessories Electrical Accessories Components Page 8-5


START POWER UNIT (SPU)

Identification and LocationThe start power unit (SPU) is located in the EE compartment onthe E2-2 shelf.

Purpose and InterfaceThe start power unit changes 28 VDC or 115 VAC electrical powerto 270 VDC power for the start converter unit (SCU). Theswitched hot battery bus or the transfer bus number 1 suppliespower to the SPU.

Functional DescriptionThe operational flow is as follows:

• The ECU sends a signal to the SCU when the air inlet door is fully open.

• The Start Converter Unit (SCU) tells the SPU to supply 270 VDC power.

• The SCU then changes the 270 VDC to AC power for the operation of the starter-generator.

• At 70% speed, the ECU removes the start signal from the SCU. With the start signal off, the SCU and SPU remove power from the starter-generator.

NOTE: The maximum duty cycle for the SPU and SCU is three starts, one after the other, followed by a 15 minute cool down period. More starts are possible after the SCU and SPU are cool.


Notes:


ATM717-066Start Power Unit

EE Compartment (Looking Aft)

Start Power Unit (E2-2)

115 VAC Transfer Bus 1Or Switched Hot

Battery Bus

Start Power Unit

ATM717.06609/02



START CONVERTER UNIT (SCU)

Identification and LocationsThe start converter unit (SCU) is located on the E2 rack in the EEcompartment.

Purpose and InterfaceThe SCU:

• operates with the APU generator control unit (AGCU) to control and regulate APU starter-generator power.

• makes the starter-generator function like a motor to turn the APU during starting.

• Changes 270 VDC from the SPU to AC power to energize the starter-generator during starting (through the SCU internal contactor)

• Sends fault data to the APU ECUThe APU generator control relay (AGCR) and the starter-genera-tor voltage regulator are inside the SCU.

Functional DescriptionThe operational flow is as follows:

• The ECU sends a signal to the SCU when the air inlet door is fully open.

• The SCU tells the SPU to supply 270 VDC power.• The SCU then changes the 270 VDC to AC power for the

operation of the starter-generator.• At 70% speed, the ECU removes the start signal from the

SCU.• With the start signal off, the SCU and SPU remove power

from the starter-generator.


NOTE: The maximum duty cycle for the SPU and SCU is three starts, one after the other, followed by a 15 minute cool down period. More starts are possible after the SCU and SPU cool.

Notes:


ATM717-078Start Converter Unit (SCU)

Start Converter Unit (E2-2)

EE Compartment (Looking Aft)

ECU (Aft Cargo)

ATM717.07809/02

Start Converter Unit



OperationThe voltage regulator and the APU generator control relay (AGCR)give excitation to the starter-generator. The voltage regulatorcontrols the amount of excitation and frequency of excitation tocontrol generator output voltage. The AGCR completes or opensthe circuit for excitation power.

The APU generator control unit (AGCU) controls the operation(on/off) of the voltage regulator and AGCR position. The AGCUsends a “voltage- regulator- enable signal” (turn on signal) to theSCU when you put an APU generator switch to the on position ifthe APU is ready to load. The AGCR also closes.

The starter-generator permanent magnet generator (PMG) is thepower source for the voltage regulator. The AGCU protection cir-cuits use the PMG output to monitor starter-generator frequencyoutput.

The voltage regulator and the AGCU monitor the voltage of eachphase at point between the starter-generator and the auxiliarypower breaker (APB). The voltage regulator uses this informationto control excitation. The AGCU uses this information for systemprotection purposes.

ProtectionThe AGCU removes the “voltage-regulator-enable signal” andopens the AGCR when the AGCU protection circuits find an electri-cal parameter not within limits.

The AGCU sends a fault signal to the SCU if a starter-generatorhigh voltage or low voltage condition happens.

The SCU sends this data to the APU ECU. This data is displayed onthe control display unit (CDU) in the flight compartment.


Notes:


ATM717-067SCU Interface

SCU Interface

ATM717.06709/02

ToBTB1,BTB2

SPU

APU StartSW (P5)

VoltageSense

PWRSupply

VoltageRegulatorand AGCR

Enable/Close

SCU

ControlCircuits

ProtectionCircuits

FaultData

APU ECU CDU (2)

RotorPMG

RotorExciter

Main GenRotor

LCT APB

To AGCU

StatorMain Gen

PMGStator

NCT

To AGCU

DC To ACConverter Cont

Starter-Generator

AGCU

APUCont

P6

28 VDCSW HotBat. Bus



STARTER-GENERATOR

Identification and LocationThe brushless AC starter-generator (which weighs 54.5 lbs.) is asalient-pole synchronous type incorporating three devices: a per-manent-magnet generator, exciter generator, and a main AC gen-erator. They share a common shaft and housing.

It is located on the upper right side of the APU gearbox and isattached with eight bolts.

Purpose and InterfaceThe starter-generator supplies the initial rotation of the APU dur-ing the start cycle. It also supplies 90 KVA, AC electrical power tothe aircraft while on the ground or in flight.

The starter-generator functions are controlled by the SCU, whichreceives 270 volts from the SPU and becomes operational inresponse to the start command (start relay signal) from the APUECU.

During the generate mode, the PMG power from the APU starter-generator is used to supply power to the starter-generator volt-age regulator.

The Starter-Generator is considered an LRU.

Maintenance Tip• If oil is leaking out from bottom of starter/generator, the

seal plate needs replacing.• There is an o-ring installed on the generator shaft. If the

O-ring is missing or cut, excessive heat accumulation to the generator will result.


Notes:


ATM717-047Starter-Generator

Starter-Generator

ATM717.04709/02

Starter/ Generator



IGNITION UNIT

Identification and LocationThe ignition unit is a single-output, dc powered unit. The output isa high-tension oscillatory-type ignition pulsing 2 to 11 times asecond.

The ignition unit bolts to the lower part of the turbine plenum.

Purpose and InterfaceThe ignition unit provides the APU with 1.0 joules deliveredenergy at 18K volts to the igniter at a minimum spark rate of 2sparks per second.

The ignition system operates on voltages from 14-36 VDC, alti-tudes from sea level to 41,000 feet.

The ignition unit, cable and plug are LRUs.

CAUTION: VOLTAGE PRODUCED BY THE IGNITION SYSTEM IS LETHAL. CAUTION SHOULD BE OBSERVED WHEN WORKING WITH THE SYSTEM.

NOTE: Ignition system problems not detected by the ECU will give the operator No Acceleration or No Flame auto-shutdowns.

NOTE: The ignition unit is energized in the 0-60% RPM range.


Notes:


ATM717-048Ignition Unit System

Ignition Unit System

ATM717.04809/02

Igniter Plug

IgniterPlug Lead

Ignition Unit



EGT THERMOCOUPLES

Identification and LocationThe EGT thermocouples are 2 closed-beaded, dual element,chromel-alumel (K-type) thermocouples, located in the APUexhaust duct.

Purpose and InterfaceThe EGT thermocouples provide EGT temperature input to theECU. Input signals control fuel flow based on acceleration to pre-vent over-temperature conditions.

Functional DescriptionEach thermocouple is separately sensed and conditioned by theECU. The ECU selects the highest reading of both rakes, so thatthe loss of one rake will not influence APU operation. This defersmaintenance action and increases dispatch reliability.

BITE circuitry allows detection of an open thermocouple duringprestart checks.

• If both thermocouple rakes fail, a start is inhibited.• If both thermocouple rakes fail open, or both

thermocouple measurement channels fail, while the APU is active, a shutdown is initiated.

• If one of the two thermocouples fail, the APU will start and run normally; an EGT TC1 (or EGT TC2)

LRU failure is stored in the ECU.

Maintenance TipThe individual thermocouples may be changed separately withoutdisturbing the system.


NOTE: The actual temperature of the APU can be viewed on the flightdeck CDU panel, under APU BITE TEST.

Notes:


ATM717-045EGT Thermocouples

REAL TIME PARAMETERS 1/4

APU BITE TEST


000.0 % 20.5 C

00.0 DEG 10.0 DEG 0.0 PSID

14.7 PSIA 14.7 PSIA

20.5 C 0.0 MA

00.0 PPH

LOW

HIGH

INT

L WIPERPARK10

EGT8

6

4 2

FAULT OVERSPEED

LOW OILPRESSUREMAINT

EGT Thermocouples

ATM717.04509/02

Exhaust Gas TemperatureThermocouples (2)

CDU

P5-4 Panel

(OR)



SPEED SENSOR

Identification and LocationThe speed sensor is a magnetic, non-contact, variable-reluctancesensor located near a gear inside of the gearbox.

Purpose and InterfaceThe speed sensor monitors mechanical motion, and sends anelectronic signal to the ECU proportional to the motion sensed.

Functional DescriptionThe speed sensor senses the gear tooth passage as the APU shaftrotates. Frequency is used by the ECU to compute APU speed.

The air gap between the stationary sensor and the moving teethof the gear will be fixed at a gap of 0.015±0.010 inch.

Its dual-coil design provides two independent speed signal to theECU for redundancy.

The speed sensor is an LRU.

Maintenance TipThe speed sensor can be removed and replaced, without measur-ing. No shimming is required.

If the APU has an overspeed condition (>106%), an amber over-speed light illuminates on the P5 flightdeck panel.


NOTE: When the overspeed light comes on, the master caution and APU annunciator light on the P7 panel also comes ON.

NOTE: The master caution and APU annunciator lights tell the pilot/ground crew that the APU has a problem.

Notes:


ATM717-046Speed Sensor

REAL TIME PARAMETERS SPEEDEGTIGV POSITIONSCV POSITIO NDELTA PRESSTOTAL PRESSINLET PRESSINLET TEMPFUEL TMCFUEL FLOW<INDEX

000.0 % 20.5 C

00.0 DEG 10.0 DEG 0.0 PSID 14.7 PSIA 14.7 PSI A

20.5 C 0.0 M A

00.0 PPH

1/4

Speed Sensor

ATM717.04609/02

CDU

Speed Sensor (Monopole)



DATA MEMORY MODULE (DMM)

Identification and LocationThe Data Memory Module (DMM) is an engine mounted (left sideof inlet plenum), non-volatile memory device.

Purpose and Interface The DMM stores information regarding the health monitoring andlife usage of the APU and is powered from the aircraft battery busvia the ECU.

The DMM interfaces with the ECU via a serial link and stores thefollowing information:

• APU serial number and model number• APU operating hours and starts• APU LCF (Low Cycle Fatigue) and creep life• APU accumulated aborted starts

The CDU “menu” handling is according to the Boeing SCD with allcommunication via an ARINC 429 low-speed data bus.

Functional DescriptionThe DMM comes with the APU serial number programmed.

At power-up, the software reads the DMM test pattern and per-forms the following:

• If numbers agree, power-up initialization is continued• If different, the ECU record is updated from the DMM.• Upon completion of an APU cool down cycle, the DMM is

automatically updated from the ECU.

APU data is also stored in the ECU in case of DMM failure.


DMM ReplacementThe the ECU is replaced, the DMM retains all the APU data andautomatically re-initializes the new ECU with the old accumulatedAPU data.Once recognized, the ECU records in memory that a DMM changehas occurred. The new DMM is then loaded with all the totaledAPU data that is stored in the ECU. The recent DMM change mes-sage is retained until the ECU is interrogated and message erasedvia command from the ARINC 429 data bus.

NOTE: Replacement DMMs are delivered with all zeros stored in their memory, hence, they are easily recognizable by the ECU as new or recycled units.

Notes:


ATM717-049Data Memory Module (DMM)

Data Memory Module (DMM)

ATM717.04909/02

Data MemoryModule (DMM)



SUMMARY


• Identify and locate the electrical accessory LRUs.• Explain the purpose of each electrical accessory

component.• Identify possible causes of electrical system malfunctions.

What are the electrical Accessory Components?The electrical accessories components are:

• Start Power Unit (located in the EE compartment on the E2-2 shelf)

• Start Converter Unit (located on the E2 rack in the EE compartment)

• Electronic Control Unit (See Chapter 3)• Starter-Generator (located on the upper right side of the

APU gearbox)• Ignition Unit (bolts to the lower part of the turbine

plenum)• EGT Thermocouples (located in the APU exhaust duct)• Speed Sensor (located near a gear inside of the gearbox)• Data Memory Module (located on the left side of inlet

plenum)

What is the purpose of each electrical accessory component?• Start Power Unit: changes 28 VDC or 115 VAC electrical

power to 270 VDC power for the start converter unit

Electrical Accessories Summ

• Start Converter Unit: - operates with the APU generator control unit (AGCU) to

control and regulate APU starter-generator power.- makes the starter-generator function like a motor to

turn the APU during starting. - Changes 270 VDC from the SPU to AC power to ener-

gize the starter-generator during starting (through the SCU internal contactor)

- Sends fault data to the APU ECU• Electronic Control Unit (See Chapter 3)• APU Starter-Generator: supplies the initial rotation of the

APU during the start cycle. It also supplies 90 KVA, AC electrical power to the aircraft while on the ground or in-flight.

Notes:

ary Page 8-22

• Ignition Unit: provides the APU with 1.0 joules delivered energy at 18K volts to the igniter at a minimum spark rate of 2 sparks per second

• EGT Thermocouples: provide EGT temperature input to the ECU

• Speed Sensor: monitors mechanical motion, and sends an electronic signal to the ECU proportional to the motion sensed

• Data Memory Module: stores information regarding the health monitoring and life usage of the APU and is powered from the aircraft battery bus via the ECU.


Notes:

ary Page 8-23



Notes:

ary Page 8-24


Notes:

CHAPTER 9—GLOSSARY

AACSC - Air conditioning system controller

ADP - Air driven pump

APB - Auxiliary power breaker

APU - Auxiliary power unit

ARINC - Aeronautical radio incorporated

ATS - Air turbine starter

ATSCV -Air turbine starter control valve

BBAT - Battery

BAV - Bleed Air Valve

BITE - Built in test equipment

BLV - Bleed load valve

BPCU - Bus power control unit

CC - Centigrade

CFDS - Centralized fault display system

CDU - Control display unit

Glossary

DDCU - Data collection unit

DMM - Data memory module

EECS - Environmental control system

ECU - Electronic control unit

EEPROMS- Electronically erasable programmable read only memory system

EGT - Exhaust gas temperature

EICAS - Engine information crew alerting system

Page 9-1


Notes:

FF - Fahrenheit

FCU - Fuel control unit

FSM - Field service monitor

GGCU - Generator control unit

HHOT - High oil temperature

IIDD - Interface data dictionary

I/O - Input/output

IOC - Input output generator

IOC LA- Input output generator left channel A

IOC RA- Input output generator right channel A

IGV - Inlet guide vane

IGVA - Inlet guide vane actuator

IOT - In operation tests

J/K/LL/C - Load compressor

LCV - Load control valve

LOP - Low oil pressure

Glossary

LRU - Line replaceable unit

LVDT - Linear variable differential transformer

MMDC - Maintenance data computer

MFD - Mulyifunction display

MES - Main engine start

MMEL - Master minimum equipment list

NNVM - Non volatile memory

Page 9-2

O/PPBA - Push button annunciator

Pcd - Compressor pressure discharge

PSI - Pounds square inch

PSIA - Pounds square inch absolute

PSID - Pounds square inch differential

PSIG - Pounds square inch gauge

PUT - Power up test

Q/RROM - Read only memory

RPM - Revolutions per minute

RTD - Resistance temperature device

RTL - Reset to load

RVDT - Rotary variable differential transformer

SSCV - Surge control valve

SOV - Shut off valve

SRU - Shop replaceable unit

STS - Status

TTM - Torque motor

Glossary

U/V/WWOW - Weight on wheels

X/Y/Z

Page 9-3