Chapter 2 - APU Flashcards
What does APU stand for?
Auxillary Power Unit
What are the 4 functions of the APU?
2 x Pneumatic
- Power plant start - Provide air for ECS and ISDS
2x Electrical
- Provide electrical power in normal situation - Provide electrical power in emergency situations
Where is the APU located?
Rear of the main gearbox, right of No.2 engine
What are the 3 major APU Modules, and what do they do?
Gearbox Module - contains reduction gearbox and associated accessory drives
Turbine Module - houses the intake, compressor rotor and turbine rotor
Combustor Module - houses the reverse flow combustion chamber and exhaust
List the 9 major components of the APU
Air Intake Exhaust Air Delivery Pipe Air Bypass Valve Starter Motor Fuel Filter HEIE Ignitor Plug Fuel Control Unit
What is the Air intake?
Channels airflow to compressor and AC Generator
What is the exhaust?
Channels gases from the turbine to atmosphere
What is the air delivery pipe?
Channels pressurised air from the combustor module to the pneumatic gallery
What is the Air Bypass valve?
Channels air from the compressor to the exhaust to prevent over pressurisation
What is the starter motor, and what is it powered by?
Starts the APU
Powered by a 28V DC battery
What is the fuel filter?
Filters fuel of any unwanted dirt and debris
What is the HEIE & Ignitor plug?
HEIE - High Energy Ignition Exciter
Converts Low tension electricity to high tension electricity
Ignitor plug creates a spark, supplying ignition to the mixture of air and fuel
What is the Fuel Control Unit?
Provides a metered amount of fuel into the combustor module during all conditions of operation
What is the main fuel manifold?
Delivers fuel to the 6 main fuel nozzles in the combustor module
Name the components of the APU Lubrication system (6)
External Pipe Low Oil Pressure Switch Sight Glass Magnetic Plug Filler Cap Filter
What does the filter contain?
Bypass mechanism in case of blockage
What does the magnetic plug do?
Collects any ferrous debris in the oil
Where is the APU AC generator located, and what does it supply to the aircraft systems?
Front face of the APU
25kVa
What does ESU stand for?
Electronic Sequencing Unit
What does the ESU do?
Automatically controls the APU start sequence and monitors critical engine parameters
What is the pneumatic gallery?
Pipe that delivers air from the APU to other engines
What does the APU master start switch do?
isolates power from the APU start circuits
What does the bleed switch do?
Selects the source of bleed air between ground use (OFF) engines or APU
What does the APU Fuel/Fail indicator indicate?
Confirms a failure in either the booster pump supply or the APU system
What does the Ready/Start indicator indicate?
APU mode of operation
What does the Low Pressure fuel switch and indicator do?
Switch isolates APU from the fuel supply, energises the ESU and turns off APU Fuel pump
Indicator shows when the low pressure fuel is in the OFF position
What does the APU Start/Stop button do?
provides an interface to start or stop the APU
Visually indicates fire warning
Where are the APU Panel switches located?
Cabin, aft of the cargo door
What does the APU cabin control panel consist of?
APU emergency stop switch
fire extinguisher switch
fire warning test switch
