36-12-25
 ALL  ú
 ú  01  Page 502
 ú  Nov 15/97 

BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A 737-300/400/500MAINTENANCE MANUAL
FAN AIR INLET PAN (EXTERNAL CRACK) NO CRACKS ALLOWED
CRACKS ON OR IN WELD SEAMS (EXTERNAL CRACK) CRACKS 1.5 INCHES MAXIMUM IN LENGTH ALLOWED FOR MAXIMUM OF 10 DAYS
BLEED AIR INLET PAN (EXTERNAL CRACK) NO CRACKS ALLOWED
SIDEPLATE (EXTERNAL CRACK) NO CRACKS ALLOWED
CORE CLOSURE BAR
CRACKS ADJACENT TO WELDS
(INTERNAL CRACK) CRACKS ALLOWED IF BLEED AIR LEAKAGE TEST IS SUCCESSFULLY COMPLETED
Precooler Crack Locations
Figure 502

BLEED AIR OUTLET PAN (EXTERNAL CRACK) NO CRACKS ALLOWED
FAN AIR EXIT FACE
(INTERNAL CRACK) CRACKS ALLOWED IF BLEED AIR LEAKAGE TEST IS SUCCESSFULLY COMPLETED
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
 S 015-020
 (2)  Open the applicable fan cowl (AMM 71-11-02/201).
 S 015-043
 WARNING: OBEY THE INSTRUCTIONS IN THE PROCEDURE TO OPEN THE THRUST
_______ REVERSERS. IF YOU DO NOT OBEY THE INSTRUCTIONS, INJURIES TO PERSONS AND DAMAGE TO EQUIPMENT CAN OCCUR.
 (3)  
Open the applicable thrust reverser (AMM 78-31-00/201).

 S 215-019

 (4)  
Examine the precooler for any cracks and find the crack location (Fig. 502).

 S 215-021

 (5)  
If the crack location is internal as specified in Figure 502, do the Bleed Air Leakage Test.

 NOTE: Closure bar cracks on the exit face next to weld seams are
____ considered internal cracks. Any cracks on or in the weld seams are external cracks.
 S 215-054
 (6)  If the crack location is external and located on or in the weld seams, do this step:
 (a)  
Measure the length of the crack.

 (b)  
If the crack length is 1.5 inches or less, continued airplane operation is acceptable for 10 days or until the crack length reaches 1.5 inches, whichever occurs first. 1) Inspect cracks that are 1.5 inches or less on a daily

 basis.

 (c)
If the crack length is greater than 1.5 inches but less than

 5.0 inches, you may continue airplane operation for a maximum of 10 days if you obey the steps that follow: 1) Position the associated BLEED switch on the P5-10 panel to
 OFF and attach a DO-NOT-OPERATE identifier to the switch.
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
 2)  Inspect the crack on a daily basis and make a record of the crack length.
 S 025-016
 (7)  If the crack location is external as specified per Figure 502 and not located on the bleed air inlet pan, replace the precooler (AMM 36-12-25/401).
 S 415-047
 WARNING: OBEY THE INSTRUCTIONS IN THE PROCEDURE TO CLOSE THE THRUST
_______ REVERSERS. IF YOU DO NOT OBEY THE INSTRUCTIONS, INJURIES TO PERSONS AND DAMAGE TO EQUIPMENT CAN OCCUR.
 (8)
Close the applicable thrust reverser (AMM 78-31-00/201).

 S 415-022

 (9)  
Close the applicable fan cowl panel (AMM 71-11-02/201).

 S 445-046

 (10)
 Do the activation procedure for the thrust reverser system (AMM 78-31-00/201).

 TASK 36-12-25-795-052
 3.  Bleed Air Leakage Test
______________________
 A. General ú (1) This task does not use any special equipment. The APU/ground air ú source is used to supply pneumatic pressure to test whether the
 level of leakage from the bleed air system and precooler ducting are ú within acceptable limits.
 B.  References
 (1)  
AMM 12-31-01/201, Zone Diagrams

 (2)  
AMM 12-31-31/201, Body Section 46 Access Doors and Panels
　
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