APU CONTROL SYSTEM -APU CONTROLLER -INTRODUCTION

Purpose
The APU controller (APUC) controls APU functions. The APUC also contains circuits for fault detection and isolation.
APUC Modes
The APUC operates in one of these eight modes:
*
Test mode -APUC does power-up test

*
Idle mode -APUC powered and APU is not on

*
Start -air mode -APU does an air start

*
Start -electric mode -APU does an electric start

*
Onspeed mode -APU RPM is more than 95 percent

*
Cooldown mode -APU is in the cooldown mode

*
Shutdown mode -APU RPM is less than 70 percent during APU shutdown

*
Auto-shutdown mode -the APUC does an APU protective shutdown.

Location
The APUC is on the E7 rack above the aft galley.
Training Information Point
The APUC is an LRU. The circuit cards in the APUC are not LRUs.
You must open a hinged access panel above the aft galley to get access to the APUC.
CAUTION:  DO NOT REMOVE THE APUC AND THE DATA MEMORY MODULE AT THE SAME TIME. IF YOU REMOVE THE APUC AND THE DATA MEMORY MODULE AT THE SAME TIME, YOU WILL LOSE THE DATA FOR THE APU.
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APU CONTROL SYSTEM -APU CONTROLLER -INTRODUCTION

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APU CONTROL SYSTEM -APU CONTROLLER -INPUTS

General
The APUC gets inputs from both airplane systems and the APU.
The APUC receives 28v dc power from both the 28v dc battery bus and the 28v dc APU battery bus.
Airplane Systems ARINC 629 Inputs
The APUC receives these airplane system inputs through the left and right ARINC 629 system buses:
*
Pneumatic duct pressure

*
APU fuel shutoff valve position

*
ECS data

*
Main engine start/run

*
Air driven pumps (ADPs) ON

*
Electrical system demand

*
Air/ground indication

*
Date/time

*
Air data

*
APU bleed valve position.

Airplane Systems Discrete Inputs
The APUC also receives other airplane systems inputs. These inputs include:
*
APU fire shutdown

*
APU ON signal

*
Air inlet door position

*
APUC maintenance test

*
APU fire switch/fire shutdown switches

*
APU autostart.

APU Inputs
Inputs from the APU to the APUC are:
*
Inlet air pressure (P2)

*
Total air pressure (PT)

*
Differential air pressure (DP)

*
Oil pressure

*
Low oil pressure switch

*
Fuel filter impending clog

*
Generator filter impending bypass

*
Lube filter impending bypass

*
EGT (4)

*
Air inlet temperature

*
Fuel temperature

*
Oil temperature

*
Gear box temperature

*
IGV position

*
SCV position

*
Fuel metering servo valve position

*
ATSCV position

*
Speed sensors (2)

*
Oil level

*
Data memory module data

*
Electric starter motor brush wear

*
APU fault data.

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APU CONTROL SYSTEM -APU CONTROLLER -INPUTS

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APU CONTROL SYSTEM -APU CONTROLLER -OUTPUTS

General
The APUC supplies APU data to airplane systems and controls some APU functions.
APUC ARINC 629 Outputs
The APUC supplies this APU data to the airplane through the left and right systems ARINC 629 buses:
*
EGT

*
Air inlet temperature

*
APU speed

*
Oil quantity

*
Oil pressure

*
Gearbox temperature

*
Fuel temperature

*
Generator load available

*
APU fault data

*
APU shutdown data

*
IGV angle

*
SCV angle

*
Pressure sensor data

*
Ignitor ON/OFF

*
Fuel shutoff solenoid ON/OFF

*
Filter clog sensor status (3)

*
Low oil pressure status

*
Electric starter brush wear

*
Maintenance test status.

Other APUC Airplane System Outputs
The APUC also sends these signals on non-ARINC 629 connections:
　
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