CHAPTER 74 - IGNITION TABLE OF CONTENTS
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Chapter Section
Subject_______ Subject ____ Effectivity_______ Page ___________
IGNITION 74-00-00
________ Description and Operation 1 ALL General 1 Cables - Exciter-to-Igniter Plug 1 Control - Engine Ignition 1 Exciters - Ignition 1 Plugs - Igniter 1 Operation 4 Component Location 101 ALL Component Index Component Location Adjustment/Test 501 ALL General 501 System (Audible) Test 504
ELECTRICAL POWER SUPPLY 74-10-00
_______________________ EXCITER 74-11-00 EXCITER - IGNITION 74-11-01 Removal/Installation 401 ALL Inspection/Check 601 ALL Cleaning/Painting 701 ALL
DISTRIBUTION 74-20-00
____________ CABLE - EXCITER-TO-IGNITER PLUG 74-21-01 Removal/Installation 401 ALL Inspection/Check 601 ALL Cleaning/Painting 701 ALL PLUG - IGNITER 74-21-02 Removal/Installation 401 ALL Inspection/Check 601 ALL Immersion Depth Check -606 Igniter Plug Visual Inspection - Igniter 601 Plug Cleaning/Painting 701 ALL Approved Repairs 801 ALL
74-CONTENTS
NGUN Page 1 Feb 18/02
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
////////////////////////A / PW4000 SERIES /747-400 / ENGINES/MAINTENANCE MANUAL ////////////////////////
CHAPTER 74 - IGNITION TABLE OF CONTENTS_________________
Subject_______ Chapter SectionSubject_______ Page____ Effectivity___________
SWITCHING_________ ENGINE IGNITION CONTROL Description and Operation General Module - Control, Engine Ignition Switch - AUTOSTART, Engine Switch - Control, Fuel Operation 74-30-0074-31-00 1 11333 ALL
74-CONTENTS
NGUN Page 2 Feb 18/02
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
IGNITION - DESCRIPTION AND OPERATION
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1. General
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A. The ignition system supplies a high energy spark to start and keep combustion of the fuel/air mixture in the combustion chamber.
B. Each engine has a dual ignition system: ignition system 1 and ignition system 2. The systems are physically and electrically independent. Each engine ignition system includes these components: Ignition Exciter, AMM 74-11-01; Exciter-to-Igniter Plug Cable, AMM 74-21-01; Igniter Plug, AMM 74-21-02; and Engine Ignition Control, AMM 74-31-00. Either one or both ignition systems can be used to supply continuous ignition for takeoff, landing, or during adverse weather conditions. Alternating use of ignition systems is recommended for engine start.
C. A cooling system (AMM 75-23-00/001) is used to decrease the temperature of the exciter-to-igniter plug cables and igniter plugs.
2. Ignition Exciters (Fig. 1)
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A. The ignition exciter is a capacitor discharge type exciter which requires an input of 115 volts ac at 400 Hz. The output voltage of each exciter is 22-26 kilovolts. Each ignition exciter is in a separate housing which is attached with vibration isolators to a common bracket installed on the upper right side of the main gearbox.
B. The ignition exciter includes of a conducted radio noise filter, a power transformer, rectifiers, storage capacitor, trigger capacitor, discharge tube, trigger transformer, and bleed resistors. All components are included in a housing with individual power input and high tension output connections.
3. Exciter-to-Igniter Plug Cables (Fig. 1)
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A. The exciter-to-igniter plug cable includes a high tension lead in an air-cooled flexible braided steel conduit. There are two cables on the right side of the engine between the ignition exciters, installed on the upper right side of the main gearbox, and the igniter plugs, found at the 4 and 5 o'clock positions on the diffuser case.
B. Each cable is an electrical path between the ignition exciter and the igniter plug. The cables are interchangeable.
4. Igniter Plugs (Fig. 1)
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A. There are two igniter plugs installed in the diffuser case at the 4 and 5 o'clock positions. The igniter plugs pass through holes in the mid section of the diffuser case aft of the fuel injectors.
B. A maximum of two classified spacers control the immersion depth of the igniter plug into the compustion chamber for delivery of ignition energy. The igniter plug, classified spacers, and mounting boss for the igniter plug for each ignition system should stay together for proper immersion depth, or tolerances must be re-established.
5. Engine Ignition Control (Fig. 1)
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A. The engine ignition control module is found on the P5 overhead panel.
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