Ignition System - Logic/Block Diagram
Figure 002
CES
IGNITION - DESCRIPTION AND OPERATION
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1.
General
_______ The ignition system is a dual system with two igniter plugs, which gives the constant high-energy ignition which ignites the fuel/air mixture in the combustion chamber. It operates during the start sequence when the APU speed is below 55%. The Electronic Control Box (ECB) controls the ignition system fully automatically.
2.
Component Location
__________________
(Ref. Fig. 001)
-------------------------------------------------------------------------------FIN | FUNCTIONAL DESIGNATION | PANEL|ZONE|ACCESS | ATA | | | | DOOR | REF. -------------------------------------------------------------------------------IGNITION UNIT 315/ 315AL 49-41-38 316 316AR IGNITER PLUGS 315/ 315AL 49-41-41 316 316AR IGNITER PLUG ELECTRICAL-LEADS 315/ 315AL 49-41-43 316 316AR
3. System Description
__________________ The ignition system ignites the fuel/air mixture in the combustion chamber of the APU during the start sequence. The main components are:
-an ignition unit,
-
two igniter plugs,
-
two igniter plug electrical-leads. The ignition unit is a completely self contained unit, installed on the lower left side of the APU. The ignition unit produces the electrical energy that is needed to ignite the fuel-air mixture in the combustion chamber. The electrical leads carry the electrical energy to the igniter plugs that are screwed into the combustion chamber at the 5 and 9 o-clock positions when looking from the rear. The ECB de-energizes the ignition unit when the combustion flame can support itself. The high efficiency components of the ignition system guarantee a minimum ignition spark energy of 0.22 joule. This is regulated to a spark rate of 2 to 5 sparks per second. The system components are sealed to minimize the possibility of any contact with flammable fluid or vapours in the APU compartment.
Ignition System - Component Location
Figure 001
CES 4. Component Description
_____________________
(Ref. Fig. 002)
A. Ignition Unit The ignition unit is a sealed metal box assembly with a mounting bracket installed on one side. Power is supplied to the unit through a multi-pin electrical connector installed on one end of the box. The two ignition leads connect to two connectors on the opposite end of the box. The unit is shop-repairable only.
B. Igniter Plug Electrical-Lead The electrical leads carry the output current from the ignition unit to the igniter plugs. Each electrical lead has an insulated electrical conductor contained in a braided metal shield. At each end of the ignition leads are insulated connectors. The ignition leads are installed between the ignition unit and the igniter plugs.
C. Igniter Plug The igniter plugs are installed in the combustion chamber at the 5 and 9-o-clock positions when looking from the rear. The igniter plug is made up of a central electrode, a ceramic insulator and an external casing. The igniter plugs supply a high voltage spark to ignite the fuel/air mixture in the combustion chamber. Each igniter plug has an outer casing, a central electrode and a ceramic insolator.
5. Operation/Control and Indication
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When you push the MASTER SW 14KD and the START 2KA pushbutton switches:
-the start sequence is started (Ref. 49-42-00),
-after 1.5 seconds, the ECB energizes the ignition system. The ignition unit supplies high-voltage electrical energy through the electrical leads to the igniter plugs. Thus the fuel-air mixture in the combustion chamber ignites,
-at 55% APU speed, the ECB de-energizes the ignition system.
Ignition System - Schematic
Figure 002
CES
IGNITION UNIT - REMOVAL/INSTALLATION
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R **ON A/C 001-003, 051-099, 401-499,
TASK 49-41-38-000-001 Removal of the Ignition Unit (8030KM) (GTCP 36-300) WARNING : DO NOT TOUCH THE APU UNTIL IT IS SUFFICIENTLY COOL TO PREVENT BURNS
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WHEN YOU DO THE MAINTENANCE TASK(S).
1.
Reason for the Job
__________________
Self Explanatory
2.
Job Set-up Information
______________________
A. Fixtures, Tools, Test and Support Equipment
-------------------------------------------------------------------------------REFERENCE QTY DESIGNATION -------------------------------------------------------------------------------
No specific blanking caps
No specific circuit breaker(s) safety clip(s)
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