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IGNITER PLUG

FLASHOVER ON CERAMIC INSULATOR

NO ARC DAMAGE ON THE CONTACT BUTTON
ARC DAMAGE ON THE CONTACT BUTTON
(NEW IGNITER PLUG)
L-71452 L-70764
Igniter Plug Inspection Figure 601 (Sheet 2)
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////////////////////////A / PW4000 SERIES /747-400 / ENGINES/MAINTENANCE MANUAL ////////////////////////
(2)  
AMM 72-00-00/601, Engine

 (3)  
AMM 74-21-02/401, Igniter Plug

 (4)  
AMM 74-21-02/701, Igniter Plug

 C.  Access
 (1)  
Location Zone
 412 Engine No. 1
 422 Engine No. 2
 432 Engine No. 3
 442 Engine No. 4

 (2)  
Access Panel
 418 Right Core Cowl Panel - Engine No. 1
 428 Right Core Cowl Panel - Engine No. 2
 438 Right Core Cowl Panel - Engine No. 3
 448 Right Core Cowl Panel - Engine No. 4

 D.  Prepare for the Inspection of the Igniter Plug
 S 026-022-N00
 (1)  
Remove the igniter plug (AMM 74-21-02/401).

 S 116-002-N00

 (2)  
Clean the igniter plug (AMM 74-21-02/701).

 E.  Procedure (Fig. 601)
 S 216-026-N00
 (1)  Do the inspection of the igniter plug:
 (a)  
Examine the coupling threads and the shell threads on the igniter plug for damage. 1) If damage is found on the coupling threads, repair the

 damaged threads with the 1.000-2NS thread chasing die. 2) If damage is found on the shell threads, repair the damaged threads with the 0.9375-16NS thread chasing die.

 (b)  
Examine the ceramic ends of the igniter plug. 1) Look for cracks in the ceramic ends. 2) Shake the igniter plug and listen for loose internal

 pieces. 3) If you find a crack, replace the igniter plug (AMM 74-21-02/401).
 CAUTION: EXAMINE THE IGNITER PLUG END FOR BROKEN CERAMIC PIECES.
_______ THESE BROKEN PIECES CAN GO INTO THE ENGINE TURBINE AND CAUSE DAMAGE TO THE ENGINE.
 (c)  Examine the igniter plug end for erosion.
 1)  Use a lighted magnifying glass to see if there is erosion through the insulator support flange.
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
2)  If there is erosion, measure the erosion with the Service Wear Measuring Tool.
 NOTE: You can use the erosion to find the wear limits on
____
 the igniter plug.

 3)  Replace the igniter plug (AMM 74-21-02/401), if one of these conditions occur: a) The inner diameter of the insulator support flange has
 erosion of more than 0.30 inch (7.62 mm) (area 3 on
 view B).
 b)  The inner diameter of the insulator support flange has erosion of more than 0.34 inch (8.64 mm) (area 4 on view B).
 NOTE: Igniter plug erosion is in proportion to the
____ total firing time (approximately 250-300 hours). The igniter will continue to fire after the erosion limits but the voltage necessary to get a spark increases to a level that can cause damage to the other ignition components (such as exciter-to-igniter plug cables).
 (d)  Examine the igniter plug for worn areas on the lower shell. 1) If the worn areas are more than 0.030 inch (0.762 mm) (area 1 on view A), replace the igniter plug (AMM 74-21-02/401).
 2)  If there is erosion through the cooling air hole (area 2 on view B), replace the igniter plug (AMM 74-21-02/401).
 (e) Examine the terminal hole of the igniter plug for these conditions: 1) Look for signs of arc damage, (identified by pitting or discoloration) on the contact button (view D). a) If there is small arc damage, clean the contact button (AMM 74-21-02/701). b) If there is a large quantity of arc damage, replace the igniter plug (AMM 74-21-02/401). 2) If there is a flashover shown by a carbon track on the ceramic insulator (view C), replace the igniter plug (AMM 74-21-02/401).
　
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