### Commercial **Airplanes** 

# 737 Service Bulletin **ALERT Number: 737-53A1318**  Original Issue: October 31, 2011 ATA System: 5331 **SUBJECT:** FUSELAGE - Skin - Skin Cracking at the Aft Waste Water Drain Mast - Inspection and Repair Export of this technology is controlled under the United States Export Administration Regulations (EAR) (15 CFR 730-774). An export license may be required before it is used for development, production or use by foreign persons from specific countries. The controller of this data has the individual responsibility to abide by all export laws. 9E991 ECCN: 

## BOEING PROPRIETARY, CONFIDENTIAL, AND/OR TRADE SECRET Copyright © 2011 The Boeing Company Unpublished Work - All Rights Reserved Boeing claims copyright in each page of this document only to the extent that the page contains copyrightable subject matter. Boeing also claims copyright in this document as a compilation and/or collective work. This document includes proprietary information owned by The Boeing Company and/or one or more third parties. Treatment of the document and the information it contains is governed by contract with Boeing. For more information, contact The Boeing Company, P.O. Box 3707, Seattle, Washington 98124. Boeing, the Boeing signature, the Boeing symbol, 707, 717, 727, 737, 747, 757, 767, 777, 787, Dreamliner, BBJ, DC-8, DC-9, DC-10, KC-10, KDC-10, MD-10, MD-11, MD-80, MD-88, MD-90, P-8A, Poseidon and the Boeing livery are all trademarks owned by The Boeing Company; and no trademark license is granted in connection with this document unless provided in writing by Boeing.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 1 of 58 2.0BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 2 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT**

BLANK PAGE**Table of Contents** Summary...................................................... 5 1. PLANNING INFORMATION........................................ 9 A. Effectivity................................................ 9 1. Airplanes............................................. 9 2. Spares Affected. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 B. Concurrent Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 C. Reason. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 D. Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 E. Compliance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 F. Approval . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 G. Manpower . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 H. Weight and Balance Changes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 I. Electrical Load Data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 J. References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 1. Existing Data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 2. Data supplied with this Service Bulletin. . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 3. Installation Drawings Used in the Preparation of this Service Bulletin. . . . . . . . . . . . 22 K. Publications Affected . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 L. Interchangeability and Intermixability of Parts. . . . . . . . . . . . . . . . . . . . . . . . . . . 23 2. MATERIAL INFORMATION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 A. Material - Price and Availability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 B. Industry Support Information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 C. Parts Necessary For Each Airplane. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 1. Kits/Parts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 2. Parts and Materials Supplied by the Operator. . . . . . . . . . . . . . . . . . . . . . . . 25 3. Parts Modified and Reidentified. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 4. Parts Removed and Not Replaced. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 D. Parts Necessary to Change Spares. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 E. Special Tooling - Price and Availability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 F. Special Tooling Necessary to do this Service Bulletin. . . . . . . . . . . . . . . . . . . . . . . 26 3. ACCOMPLISHMENT INSTRUCTIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 A. GENERAL INFORMATION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 B. WORK INSTRUCTIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 FIGURE 1: GET ACCESS TO THE DRAIN MAST SUPPORT STRUCTURE [Group 1]. . . . . . . . 31 FIGURE 2: DO A DETAILED INSPECTION OF THE CHANNEL AND THE FILLERS [Group 1]. . . . 34 FIGURE 3: INSPECT THE BONDING STRAP LOCATION [Group 1]. . . . . . . . . . . . . . . . . . 36 FIGURE 4: MEASURE THE DIAMETER OF THE WASHERS UNDER THE DRAIN MAST BOLTS [Group 1] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 FIGURE 5: MEASURE THE THICKNESS OF THE WASHERS UNDER THE DRAIN MAST BOLTS - INSTRUMENT METHOD [Group 1]. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 FIGURE 6: MEASURE THE THICKNESS OF THE WASHERS UNDER THE DRAIN MAST BOLTS - OPTIONAL TOOL METHOD [Group 1]. . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 FIGURE 7: REMOVE THE DRAIN MAST [Group 1]. . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 FIGURE 8: DO ANHFEC AND DETAILED INSPECTION OF THE SKIN, THE CHANNEL, AND THE FILLERS [Group 1]. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 FIGURE 9: INSTALL THE DRAIN MAST [Group 1]. . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 3 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT**FIGURE 10: OPTIONAL TOOL A AND TOOL B - MADE BY THE OPERATOR [Group 1]. . . . . . . . 56

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 4 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT**

### Commercial **Airplanes** 

# 737 Service Bulletin **ALERT Summary**  **Number: 737-53A1318** Original Issue: October 31, 2011 ATA System: 5331 **SUBJECT:** FUSELAGE - Skin - Skin Cracking at the Aft Waste Water Drain Mast - Inspection and Repair THIS BULLETIN IS SENT TO THE OPERATORS OF RECORD OF THE AIRPLANES SHOWN IN PARAGRAPH 1.A., EFFECTIVITY. IF AN AIRPLANE HAS BEEN LEASED OR SOLD, SEND THIS SERVICE BULLETIN TO THE NEW OPERATOR. IF APPLICABLE SPARES HAVE BEEN SOLD, SEND THIS SERVICE BULLETIN TO THE NEW OWNER. **CONCURRENT REQUIREMENTS** None. **BACKGROUND** This service bulletin is sent to ensure that the aft waste water drain mast is installed correctly. A drain mast that is not installed correctly can cause cracks in the fuselage skin and the internal support structure. The skin cracks can not be seen because they are hidden by the drain mast. If cracks in the fuselage skin are not detected and repaired, they can grow past the frames that are adjacent to the drain mast and reach a critical length. Continued operation of the airplane with undetected cracks could result in uncontrolled decompression of the airplane. The drain mast is located between BS 986 - BS 1006 and between Stringer S-24L - S-25L. In January 2010, one operator reported that the aft drain mast was found loose on a 737-400 airplane with approximately 30,500 flight cycles. Further investigation revealed the fuselage skin and surrounding back up structure were cracked. The crack common to the fuselage skin was hidden under the drain mast and was approximately 8 inches long. The crack was probably caused by incorrect installation of the drain mast. Accomplishment of the inspections in this service bulletin will make sure that the aft drain mast is installed correctly and will make sure that cracks under the aft drain mast are detected and repaired before they reach a critical length. Boeing Service Related Problem (SRP) 737-SRP-53-0367 is related to this service bulletin.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 5 of 58**ACTION Group 1:**  On Group 1 airplanes, get access to the internal support structure for the aft waste water drain mast. Do an internal detailed inspection of the drain mast support structure for cracks or corrosion. If cracks or corrosion are found, then contact Boeing for a repair. Inspect the location of the drain mast ground strap. Inspect the washers under the four bolts that hold the aft drain mast. If the ground strap is installed at an incorrect location, or if incorrect washers are found, then remove the drain mast and do an HFEC inspection of the skin and support structure for cracks. Do a detailed inspection of the skin under the drain mast and the support structure for corrosion. If cracks or corrosion are found, then contact Boeing for a repair. **Group 2:** On Group 2 airplanes, contact Boeing to get instructions for the inspection and repair for this service bulletin, 737-53A1318 Original Issue, and do the work instructed by Boeing. **EFFECTIVITY** 737-100/200/200C/300/400/500 Airplanes with the aft waste water drain mast installed. Refer to Paragraph 1.A.1., Airplanes for the list of affected airplanes. **COMPLIANCE** The Federal Aviation Administration (FAA) will possibly release an Airworthiness Directive related to this service bulletin. The Airworthiness Directive will make the compliance tasks and times given in this service bulletin mandatory. Refer to Paragraph 1.E., Compliance. **INDUSTRY SUPPORT INFORMATION** Boeing warranty remedies are not available for the inspection, configuration changes, and/or repair procedures given in this service bulletin. **MANPOWER** Refer to Paragraph 1.G., Manpower . **MATERIAL INFORMATION** Operator Supplied Parts/Materials. Refer to Paragraph 2.A., Material - Price and Availability.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 6 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT**BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 7 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT**BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 8 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT**

BLANK PAGE

### Commercial **Airplanes** 

# 737 Service Bulletin **ALERT Number: 737-53A1318**  Original Issue: October 31, 2011 ATA System: 5331 **SUBJECT:** FUSELAGE - Skin - Skin Cracking at the Aft Waste Water Drain Mast - Inspection and Repair THIS BULLETIN IS SENT TO THE OPERATORS OF RECORD OF THE AIRPLANES SHOWN IN PARAGRAPH 1.A., EFFECTIVITY. IF AN AIRPLANE HAS BEEN LEASED OR SOLD, SEND THIS SERVICE BULLETIN TO THE NEW OPERATOR. IF APPLICABLE SPARES HAVE BEEN SOLD, SEND THIS SERVICE BULLETIN TO THE NEW OWNER. **1. PLANNING INFORMATION A. Effectivity**  1. Airplanes Refer to Service Bulletin Index D6-19567 Part 3 for Airplane Variable Number, Line Number, and Serial Number data.
**DESCRIPTION CONFIGURATION**  **GROUP** 737-200/200C/300/400/500 airplanes with an aft waste water drain mast installed, excluding line numbers 1-291 - 1
737-100/200 airplanes with an aft waste water drain mast installed, line numbers 1-291 - 2

Airplane Models: 737-100, 737-200, 737-200C, 737-300, 737-400, 737-500 **Group Variable Number**  2 PA001 - PA022 2 PA099 2 PG001 - PG004 2 PG006 - PG019 2 PG022 - PG025

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 9 of 58**Group Variable Number**  2 PG027 2 PG030 2 PG032 - PG033 2 PG038 - PG040 2 PG044 - PG045 2 PG051 - PG054 2 PG057 2 PG060 - PG063 2 PG065 - PG072 2 PG075 1 PJ003 - PJ009 1 PJ114 - PJ119 1 PJ201 - PJ219 1 PJ301 - PJ302 1 PJ551 - PJ561 1 PJ601 - PJ615 1 PJ811 1 PJ816 - PJ817 1 PK201 - PK202 1 PK281 - PK289 1 PK351 - PK360 1 PK391 1 PK461 - PK469 1 PK495 1 PK501 - PK504 1 PK611 - PK617 1 PK621 - PK637 1 PK671 - PK681 1 PK731 - PK765 1 PK771 - PK779 1 PK801 - PK804 1 PK819 - PK827 1 PK830

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 10 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT Group**  **Variable Number** 1 PK871 - PK874 1 PK901 - PK938 1 PK971 - PK974 1 PL002 - PL024 1 PL081 1 PL221 1 PL401 - PL417 1 PL451 - PL456 1 PL471 1 PL551 - PL562 1 PL624 - PL626 1 PL631 - PL632 1 PL736 - PL747 1 PL762 - PL770 1 PL783 - PL788 1 PM141 - PM142 1 PM171 1 PM251 - PM255 1 PM281 - PM283 1 PM381 - PM399 1 PM401 - PM417 1 PM541 - PM564 1 PN001 - PN002 1 PN021 - PN043 1 PN081 - PN086 1 PN101 - PN117 1 PN451 - PN456 1 PN471 - PN474 1 PN501 - PN502 1 PN521 1 PP001 - PP054 1 PP201 - PP205 1 PP221

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 11 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT Group**  **Variable Number** 1 PP231 - PP243 1 PP281 - PP286 1 PP301 - PP305 1 PP351 - PP353 1 PP384 1 PP391 - PP393 1 PP401 - PP440 1 PP471 - PP475 1 PP501 - PP520 1 PP671 - PP699 1 PP701 - PP733 1 PP801 - PP808 1 PP821 - PP827 1 PP831 - PP848 1 PP851 - PP852 1 PP861 - PP877 1 PP904 - PP936 1 PP946 - PP948 1 PP951 - PP952 1 PP961 - PP967 1 PP981 - PP990 1 PP993 1 PQ001 - PQ016 1 PQ026 - PQ041 1 PQ051 - PQ092 1 PQ101 - PQ199 1 PQ201 - PQ202 1 PQ241 - PQ243 1 PQ251 - PQ267 1 PQ281 - PQ299 1 PQ301 - PQ307 1 PQ331 - PQ332 1 PQ341 - PQ348

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 12 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT Group**  **Variable Number** 1 PQ361 - PQ373 1 PQ391 - PQ395 1 PQ401 - PQ418 1 PQ421 1 PQ431 - PQ438 1 PQ447 - PQ448 1 PQ451 1 PQ454 1 PQ471 - PQ475 1 PQ479 - PQ481 1 PQ486 - PQ487 1 PQ491 - PQ493 1 PQ771 - PQ772 1 PQ791 - PQ793 1 PQ801 - PQ805 1 PQ931 - PQ935 1 PQ951 1 PQ971 - PQ997 1 PR001 - PR017 1 PR021 - PR034 1 PR041 - PR045 1 PR061 - PR072 1 PR077 - PR082 1 PR091 - PR092 1 PR096 1 PR101 1 PR121 - PR122 1 PR131 - PR132 1 PR141 - PR143 1 PR161 - PR172 1 PR181 1 PS601 - PS631 1 PS636 - PS638

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 13 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT Group**  **Variable Number** 1 PS641 - PS644 1 PS669 1 PS691 - PS692 1 PS701 - PS706 1 PS811 1 PS836 - PS837 1 PS841 - PS846 1 PS851 - PS852 1 PS856 1 PS861 - PS863 1 PS866 - PS868 1 PS871 - PS874 1 PS896 - PS897 1 PS956 - PS957 1 PS961 - PS963 1 PS971 - PS978 1 PT001 - PT015 1 PT021 - PT031 1 PT041 - PT064 1 PT101 - PT105 1 PT121 - PT138 1 PT146 - PT148 1 PT161 - PT170 1 PT181 - PT188 1 PT211 - PT220 1 PT295 1 PT331 - PT360 1 PT381 - PT399 1 PT401 - PT438 1 PT501 - PT517 1 PT561 - PT565 1 PT581 - PT586 1 PT611 - PT621

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 14 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT Group**  **Variable Number** 1 PT641 - PT644 1 PT651 - PT656 1 PT671 - PT672 1 PT681 - PT685 1 PT701 - PT703 1 PT716 - PT717 1 PT721 - PT725 1 PT801 - PT834 1 PT851 - PT854 1 PT871 - PT886 1 PT901 - PT930 1 PT971 - PT973 1 PT981 - PT985 1 PT996 1 PU301 1 PV001 - PV055 1 PV201 - PV209 1 PV226 - PV229 1 PV231 - PV237 1 PV271 - PV272 1 PV281 - PV287 1 PV296 1 PV301 - PV302 1 PV351 1 PV356 - PV357 1 PW001 - PW054 1 PW061 - PW068 1 PW072 1 PW086 - PW088 1 PW091 - PW094 1 PW101 - PW102 1 PW106 1 PW111 - PW120

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 15 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT Group**  **Variable Number** 1 PW156 - PW157 1 PW161 - PW171 1 PW201 - PW252 1 PW261 - PW268 1 PW271 - PW276 1 PW278 1 PW281 - PW293 1 PW296 1 PW301 - PW327 1 PW401 - PW408 1 PW411 - PW418 1 PW421 - PW424 1 PW431 - PW435 1 PW441 - PW450 1 PW461 - PW467 1 PW501 - PW504 1 PW511 - PW522 1 PW524 - PW550 1 PW556 - PW557 1 PW561 - PW564 1 PW571 - PW576 1 PW591 - PW596 1 PW611 - PW622 1 PW631 - PW637 1 PW661 - PW662 1 PW681 - PW683 1 PW701 - PW702 1 PW711 - PW717 1 PW741 - PW742 1 PW761 1 PW771 1 PW831 1 PW851 - PW856

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 16 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT Group**  **Variable Number** 1 PY056 - PY057 1 PY101 - PY103 1 PY111 - PY113 1 PY151 - PY154 1 PY201 1 PY231 1 PY461 - PY463 1 PY721 2. Spares Affected None. **B. Concurrent Requirements** None. **C. Reason** This service bulletin is sent to ensure that the aft waste water drain mast is installed correctly. A drain mast that is not installed correctly can cause cracks in the fuselage skin and the internal support structure. The skin cracks can not be seen because they are hidden by the drain mast. If cracks in the fuselage skin are not detected and repaired, they can grow past the frames that are adjacent to the drain mast and reach a critical length. Continued operation of the airplane with undetected cracks could result in uncontrolled decompression of the airplane. The drain mast is located between BS 986 - BS 1006 and between Stringer S-24L - S-25L. In January 2010, one operator reported that the aft drain mast was found loose on a 737-400 airplane with approximately 30,500 flight cycles. Further investigation revealed the fuselage skin and surrounding back up structure were cracked. The crack common to the fuselage skin was hidden under the drain mast and was approximately 8 inches long. The crack was probably caused by incorrect installation of the drain mast. Accomplishment of the inspections in this service bulletin will make sure that the aft drain mast is installed correctly and will make sure that cracks under the aft drain mast are detected and repaired before they reach a critical length. Boeing Service Related Problem (SRP) 737-SRP-53-0367 is related to this service bulletin.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 17 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT D. Description**  **Group 1:** On Group 1 airplanes, get access to the internal support structure for the aft waste water drain mast. Do an internal detailed inspection of the drain mast support structure for cracks or corrosion. If cracks or corrosion are found, then contact Boeing for a repair. Inspect the location of the drain mast ground strap. Inspect the washers under the four bolts that hold the aft drain mast. If the ground strap is installed at an incorrect location, or if incorrect washers are found, then remove the drain mast and do an HFEC inspection of the skin and support structure for cracks. Do a detailed inspection of the skin under the drain mast and the support structure for corrosion. If cracks or corrosion are found, then contact Boeing for a repair. **Group 2:** On Group 2 airplanes, contact Boeing to get instructions for the inspection and repair for this service bulletin, 737-53A1318 Original Issue, and do the work instructed by Boeing. The work in this service bulletin is done in the maintenance zone(s) given below. **Group 1:**
**Affected Maintenance Zones Zone**  **Model** 2-20 737-200, 737-200C **Group 1:**
**Affected Maintenance Zones Zone**  **Model** 220 737-300, 737-400, 737-500 **Group 2:**
**Affected Maintenance Zones Zone**  **Model** 2-20 737-100, 737-200 **E. Compliance** The Federal Aviation Administration (FAA) will possibly release an Airworthiness Directive related to this service bulletin. The Airworthiness Directive will make the compliance tasks and times given in this service bulletin mandatory.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 18 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT Group 1:**  **Table 1: Aft Waste Water Drain Mast Inspection and Repair on Group 1 Airplanes Repeat Interval**  **(Not to Exceed) Compliance Time (Whichever**  **Occurs Later ) Action**  **Condition**

None Within 4,500flight cycles after the original issue date ofthis Service Bulletin. Before 25,000 total airplane flight cycles. Do a detailed inspection of the channel and the fillersfor cracks and signs of corrosion in accordance with Accomplishment Instruction 3.B.1.c. 737-200/200C/300/400/500 airplanes with an aft waste water drain mast installed, excluding line numbers 1- 291

None Within 4,500flight cycles after the original issue date ofthis Service Bulletin. Before 25,000 total airplane flight cycles. Inspect the bonding strap forthe correct location in accordance with AccomplishmentInstruction 3.B.1.d. If an incorrect installation is found, then remove the drain mastand do an HFEC and detailed inspection of skin, channel, and fillers forcracks and signs of corrosion in accordance with Accomplishment Instruction 3.B.1.d None Within 4,500flight cycles after the original issue date ofthis Service Bulletin. Before 25,000 total airplane flight cycles. Measure the diameter of the washers under the drain mast bolts in accordancewith Accomplishment Instruction 3.B.1.e. If an incorrectinstallation is found, then remove the drain mast and doan HFEC and detailed inspection of skin, channel, and fillers for cracks andsigns of corrosion in accordance with Accomplishment Instruction 3.B.1.e. None Within 4,500flight cycles after the original issue date ofthis Service Bulletin. Before 25,000 total airplane flight cycles. Measure the thickness of the washers under the drain mast bolts in accordancewith Accomplishment Instruction 3.B.1.f. If an incorrectinstallation is found, then remove the drain mast and doan HFEC and detailed inspection of skin, channel, and fillers for cracks andsigns of corrosion in accordance with Accomplishment Instruction 3.B.1.f.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 19 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT Group 1:**  **Table 1: Aft Waste Water Drain Mast Inspection and Repair on Group 1 Airplanes Repeat Interval**  **(Not to Exceed) Compliance Time (Whichever**  **Occurs Later ) Action**  **Condition**

None Before further flight Contact Boeing to get instruc- tions for the repair for this service bulletin, 737- 53A1318 Original Issue, and do the work instructed by Boeing. A crack or sign of corrosion is found in the the skin, the channel, or the fillers.

**Group 2:** On Group 2 airplanes, contact Boeing to get instructions for the inspection and repair for this service bulletin, 737-53A1318 Original Issue, and do the work instructed by Boeing before further flight. **F. Approval** This service bulletin was examined by the Federal Aviation Administration (FAA). The changes specified in this service bulletin comply with the applicable regulations and are FAA approved, as well as European Aviation Safety Agency (EASA)/Joint Aviation Authorities (JAA) approved for all EASA/JAA approved airplanes listed in the service bulletin effectivity. This service bulletin and its approval were based on the airplane in its original Boeing delivery configuration or as modified by other approved Boeing changes. If an airplane has a non-Boeing modification or repair that affects a component or system also affected by this service bulletin, the operator is responsible for obtaining appropriate regulatory agency approval before incorporating this service bulletin. **G. Manpower** The table below shows an estimate of the task hours necessary to do this service bulletin for each airplane. This estimate is for direct labor only, done by an experienced crew. Adjust the estimate with operator task hour data if necessary. The estimate does not include lost time. These are some examples of lost time: • Time to adjust to the workplace • Time to schedule the work • Time to inspect the work • Time to cure the materials • Time to make the parts • Time to find the tools. **Elapsed Hours Task Hours**  **Number of Persons Task**  0.25 0.25 1 Open Access (Open Circuit Breaker) 0.55 0.55 1 FIGURE 1 - Open Access

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 20 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT Elapsed Hours**  **Task Hours Number of Persons**  **Task** 1.00 1.00 1 FIGURE 2 - Detailed Inspection 0.10 0.10 1 FIGURE 3 - Inspect Bonding Strap 0.15 0.15 1 FIGURE 4 - Inspect Washer Diameter 0.75 0.75 1 FIGURE 5 - Inspect Washer Thickness, Instrument Method 0.20 0.20 1 FIGURE 6 - Inspect Washer Thickness, Tool Method 0.75 0.75 1 FIGURE 7 - Remove Drain Mast (a) 2.00 2.00 1 FIGURE 8 - HFECand Detailed Inspection (a) 1.50 1.50 1 FIGURE 9 - Install Drain Mast (a) (b) (b) (b) FIGURE 10 - Make Tool 0.80 0.80 1 Close Access 3.60 3.60 TOTAL FOR EACH AIRPLANE (If Measuring Thickness of Washers by Instrument Method) (a) 3.05 3.05 TOTAL FOR EACH AIRPLANE (If Measuring Thickness of Washers by Optional Tool Method) (a)(a) The totals given do not include estimates for Figures 7, 8 and 9. If it is necessary to do Figures 7, 8 and 9, then you must add estimates for Figures 7, 8, and 9 to the totals given. Paragraph 3.B. tells you when it is necessary to do Figures 7, 8 and 9. (b) No manpower estimate is given. Time to make tools is considered lost time in Boeing manpower estimates. **H. Weight and Balance Changes** None. **I. Electrical Load Data** Not applicable.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 21 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT J. References**  1. Existing Data a. Service Related Problem (SRP) 737-SRP-53-0367 b. Boeing Service Letter 737-SL-51-042 c. Service Bulletin Index D6-19567 d. Standard Overhaul Practices Manual (SOPM) 20-11-03, 20-41-02, 20-41-05, 20-43-03, 20-50-01, 20-50-19 e. Standard Wiring Practices Manual (SWPM) 20-10-11, 20-10-12, 20-10-19, 20-20-00, 20-20-10 f. 737 Non-Destructive Testing (NDT) Manual Part 6, 51-00-00, Figure 4, Part 6, 51-00-00, Figure 16, Part 6, 51-00-00, Figure 23 g. 737-100/200 Aircraft Maintenance Manual (AMM) 30-71-0, 51-31-0 h. 737-300/400/500 Aircraft Maintenance Manual (AMM) 30-71-00, 51-31-00 2. Data supplied with this Service Bulletin None. 3. Installation Drawings Used in the Preparation of this Service Bulletin
**Title Drawing Number**  Aft Waste Water Drain Mast Support Installation 65-55843 Aft Waste Water Drain Mast Installation 65-55765 These drawings were used to prepare this service bulletin. These drawings are not necessary to make the specified changes, and are not supplied with this service bulletin. These drawings may not be applicable to all airplane configurations or operators. **K. Publications Affected** 1. Publications: **Chapter-Section Publication**  38-31 737 Aircraft Maintenance Manual 38-31 737 Illustrated Parts Catalog 2. Damage Tolerance Based Structural Inspections: Boeing has evaluated the repairs and/or changes in this service bulletin for effects on Fatigue Critical Structure (FCS) and for changes to Damage Tolerance Inspections (DTI) required in the Maintenance Program. This service bulletin affects FCS but no new DTIs are necessary.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 22 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT L. Interchangeability and Intermixability of Parts**  Accomplishment of this service bulletin does not affect interchangeability or intermixability of parts.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 23 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT**BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 24 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT**

BLANK PAGE**2. MATERIAL INFORMATION A. Material - Price and Availability**  The operator can supply the parts and materials shown in Paragraph 2.C., Parts Necessary for Each Airplane. As an alternative, operators can purchase the parts from Boeing Spares. This service bulletin does not show the Boeing price and supply data. **B. Industry Support Information** Boeing warranty remedies are not available for the inspection, configuration changes, and/or repair procedures given in this service bulletin. **C. Parts Necessary For Each Airplane** 1. Kits/Parts None. 2. Parts and Materials Supplied by the Operator

**Notes Name**  **QTY Part Number / Specification**  (a) Bolt 4 BACB30LM4-4 (a) Washer 4 NAS1149D0416H (a) Seal Washer 4 NAS1523C4R (a) (b) Chemical Conversion Coating 5 Oz Type 2, Class A (a) (c) Primer 5 Oz BMS 10-11, Type I (a) (c) Sealant 10 Oz BMS 5-95, Type 1, Class B-1/2 or Class B-2 (c) Corrosion Inhibiting Compound 15 Oz BMS 3-29 (a) This part or material is necessary only if you do Figure 9. Paragraph 3.B. tells you when it is necessary to do Figure 9. (b) Refer to SOPM 20-43-03 for material sources. (c) See the Qualified Products List at the end of the Boeing Material Specification (BMS) for supplier data.
3. Parts Modified and Reidentified None 4. Parts Removed and Not Replaced None **D. Parts Necessary to Change Spares** None

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 25 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT E. Special Tooling - Price and Availability**  The operator can supply the tools shown in Paragraph 2.F., Special Tooling Necessary to do this Service Bulletin. Tool price and supply data are not given. **F. Special Tooling Necessary to do this Service Bulletin** The operator can make optional Tool A and Tool B in accordance with Figure 10. Use Tool A and Tool B as an optional method of measuring the thickness of the washers under the drain mast bolts in accordance with Figure 6. The operator can do the requirements of this service bulletin without Tool A and Tool B by measuring the thickness of the washers under the drain mast bolts in accordance with Figure 5. Maintenance and overhaul tools in the manuals given in Paragraph 1.J., References, can be necessary. Examine operator tool supply to make sure all necessary tools are available.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 26 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT 3. ACCOMPLISHMENT INSTRUCTIONS**  **A. GENERAL INFORMATION CAUTION:**  KEEP THE WORK AREA, WIRES AND ELECTRICAL BUNDLES CLEAN OF METAL PARTICLES OR CONTAMINATION WHEN YOU USE TOOLS. UNWANTED MATERIAL, METAL PARTICLES OR CONTAMINATION CAUGHT IN WIRE BUNDLES CAN CAUSE DAMAGE TO THE BUNDLES. DAMAGED WIRE BUNDLES CAN CAUSE SPARKS OR OTHER ELECTRICAL DAMAGE. **NOTE:** 1. Manual titles are referred to by acronyms. Refer to Paragraph 1.J., References, for definition of the acronyms. 2. Obey all of the warnings and cautions given in the specified manual sections. 3. Unless shown differently, these dimensions and tolerances are used: – Linear dimensions are in inches – Tolerance on linear dimensions, other than rivet and bolt edge margins, is plus or minus 0.03 inch – Tolerance on rivet and bolt edge margin is plus or minus 0.05 inch – Angular tolerance is plus or minus 2 degrees – Hole dimensions for standard solid rivets and fasteners are in Structural Repair Manual (SRM) Chapter 51 4. Use the approved fastener and process material substitutions in accordance with SRM Chapter 51. 5. Refer to the SWPM 20-10-11 and SWPM 20-10-12 for the wire installation procedures, and SWPM 20-10-19 for the wire separation requirements, as accepted procedures. 6. A Detailed Inspection is defined as: An intensive examination of a specific item, installation, or assembly to detect damage, failure, or irregularity. Available lighting is normally supplemented with a direct source of good lighting at an intensity deemed appropriate. Inspection aids such as mirrors, magnifying lenses, etc. may be necessary. Surface cleaning and elaborate procedures may be required. 7. These work instructions refer to procedures included in other Boeing documents. When the words "refer to" are used and the operator has an accepted alternative procedure, the accepted alternative procedure can be used. When the words "in accordance with" are included in the instruction, the procedure in the Boeing document must be used. 8. Boeing Service Letter 737-SL-51-042, Damage Reporting and Repair Plan/Design Guidelines, is an acceptable procedure to request information from Boeing for additional structural repair instructions. The Service Letter describes what information must be provided to Boeing before a structural repair can be provided. 9. The instructions in Paragraph 3.B., Work Instructions and the figures can include operation of tools or test equipment. Boeing Engineering Tool Drawings, the Illustrated Tool and Equipment Manual, and the Special Tool and Ground Handling Drawing Index contain data on versions of the tools or test equipment that you can use. It is permitted to use replaced tools. It is not permitted to use superseded tools.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 27 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT**10. If it is necessary to remove more parts for access, you can remove those parts. If you can get access without removing identified parts, it is not necessary to remove all of the identified parts. Jacking and shoring limitations must be observed. 11. Where the work instructions include installation of a kept part, a new or serviceable part with the same part number can be installed as an alternative to the kept part. 12. This service bulletin includes functional test procedures for the systems changed by this service bulletin. More functional tests can possibly be necessary in accordance with standard maintenance practices because of interruption to other airplane systems. **B. WORK INSTRUCTIONS**
1. **Group 1:** Work Instructions for Group 1 airplanes. a. Do these Work Instructions at the times given in Paragraph 1.E Compliance. b. Get access to the work area. (1) Open the DRAIN MAST HEATER circuit breakers on the P18 panel. Attach DO-NOT-CLOSE tags. (2) Get access to the aft waste water drain mast support structure in accordance with Figure 1. c. Do a detailed inspection of the channel and the fillers for cracks and signs of corrosion adjacent to the drain mast bolts in accordance with Figure 2. (1) If there is no crack and no sign of corrosion, then do Paragraph 3.B.1.d. (2) If there is a crack or sign of corrosion, then contact Boeing for a repair. Refer to Boeing Service Letter 737-SL-51-042 as an accepted procedure. d. Inspect the bonding strap for the correct location in accordance with Figure 3. (1) If the bonding strap is installed at the location in accordance with Figure 3, then do Paragraph 3.B.1.e. (2) If the bonding strap is not installed at the location in accordance with Figure 3, then you you have an incorrect installation. Remove the drain mast in accordance with Figure 7. Do an HFEC inspection of the skin, the channel, and the fillers for cracks that start at the drain mast bolt holes, in accordance with Figure 8. Do a detailed inspection of the skin, the channel, and the fillers for signs of corrosion adjacent to the drain mast bolt holes, in accordance with Figure 8. (3) If there is no crack and no sign of corrosion, then install the drain mast in accordance with Figure 9 and do Paragraph 3.B.1.g. (4) If there is a crack or sign of corrosion, then contact Boeing for a repair. Refer to Boeing Service Letter 737-SL-51-042 as an accepted procedure.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 28 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT**e. Measure the diameter of the washers under the drain mast bolts in accordance with Figure 4. (1) If the diameter of all the washers measures within the range in accordance with Figure 4, then do Paragraph 3.B.1.f. (2) If the diameter of any washer does not measure within the range in accordance with Figure 4, or if no washers are installed, then you have an incorrect installation. Remove the drain mast in accordance with Figure 7. Do an HFEC inspection of the skin, the channel, and the fillers for cracks that start at the drain mast bolt holes, in accordance with Figure 8. Do a detailed inspection of the skin, the channel, and the fillers for signs of corrosion adjacent to the drain mast bolt holes, in accordance with Figure 8. (3) If there is no crack and no sign of corrosion, then install the drain mast in accordance with Figure 9 and do Paragraph 3.B.1.g. (4) If there is a crack or sign of corrosion, then contact Boeing for a repair. Refer to Boeing Service Letter 737-SL-51-042 as an accepted procedure. f. Measure the thickness of the washers under the drain mast bolts in accordance with Figure 5. As an option, you can make Tool A and Tool B in accordance with Figure 10, and measure the thickness of the washers under the drain mast bolts in accordance with Figure 6. (1) If the thickness of the washers measures within range in accordance with Figure 5 or Figure 6, then do Paragraph 3.B.1.g. (2) If the thickness of the washers does not measure within the range in accordance with Figure 5 or Figure 6, then you have an incorrect installation. Remove the drain mast in accordance with Figure 7. Do an HFEC inspection of the skin, the channel, and the fillers for cracks that start at the drain mast bolt holes, in accordance with Figure 8. Do a detailed inspection of the skin, the channel, and the fillers for signs of corrosion adjacent to the drain mast bolt holes, in accordance with Figure 8. (3) If there is no crack and no sign of corrosion, then install the drain mast in accordance with Figure 9 and do Paragraph 3.B.1.g. (4) If there is a crack or sign of corrosion, then contact Boeing for a repair. Refer to Boeing Service Letter 737-SL-51-042 as an accepted procedure. g. Close access to the work area.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 29 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT**(1) Apply Corrosion Inhibiting Compound BMS 3-29 to the area where corrosion inhibiting compound was removed for inspection. Refer to SOPM 20-41-05 as an accepted procedure. (2) Install the kept insulation that was removed for access. (3) Install the kept aft cargo compartment access panel that was removed for access. (4) Remove the DO-NOT-CLOSE tags and close the DRAIN MAST HEATER circuit breakers on the P18 panel. (5) Return the airplane to a serviceable condition. 2. **Group 2:** Work Instructions for Group 2 airplanes. a. Do these Work Instructions at the times given in Paragraph 1.E Compliance. b. On Group 2 airplanes, contact Boeing to get instructions for the inspection and repair for this service bulletin, 737-53A1318 Original Issue, and do the work instructed by Boeing.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 30 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT This Figure applies only to: Group 1.** 

**FIGURE 1: GET ACCESS TO THE DRAIN MAST SUPPORT STRUCTURE (SHEET 1 OF 3)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 31 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT FIGURE 1: GET ACCESS TO THE DRAIN MAST SUPPORT STRUCTURE**  **(SHEET 2 OF 3)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 32 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT**The step numbers shown below agree with the numbers shown in the circle symbols in the figure.
**MORE DATA NAME**  **TASK STEP**  Remove and keep the access panel from the aft bulkhead in the aft cargo compartment. Access Panel Remove / Keep 1 Remove the insulation from the drain mast support structure. Keep the insulation. Make sure that you can see the four drain mast bolts. Make sure you can see the bonding strap. (a) Insulation Remove / Keep 2

(a) The drain mast support structure is located 4.5 feet behind the bulkhead between BS 986 - BS 1006 and between Stringer S-24L - S-25L.

**FIGURE 1: GET ACCESS TO THE DRAIN MAST SUPPORT STRUCTURE (SHEET 3 OF 3)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 33 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT This Figure applies only to: Group 1.** 

**FIGURE 2: DO A DETAILED INSPECTION OF THE CHANNEL AND THE FILLERS (SHEET 1 OF 2)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 34 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT**The step numbers shown below agree with the numbers shown in the circle symbols in the figure.
**MORE DATA NAME**  **TASK STEP**  Clean the channel and the fillers for inspection. The inspectionarea must be clean of dirt, grease, corrosion inhibiting compound, or other substances that prevent a detailed inspection of the structure. Make sure you only use approved compound removal tools. Refer to 737-100/200 AMM 51-31-0 or 737- 300/400/500 AMM 51-31-00 as an accepted procedure. Channel / Filler Clean 1

Do an internal detailed inspection of the channel and the fillers for cracks and signs of corrosion adjacent to the drain mast bolts. Channel / Filler Inspect 2

**FIGURE 2: DO A DETAILED INSPECTION OF THE CHANNEL AND THE FILLERS (SHEET 2 OF 2)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 35 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT This Figure applies only to: Group 1.** 

**FIGURE 3: INSPECT THE BONDING STRAP LOCATION (SHEET 1 OF 2)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 36 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT**The step numbers shown below agree with the numbers shown in the circle symbols in the figure.
**MORE DATA NAME**  **TASK STEP**  Make sure that the bonding strap is installed on the forward drain mast bolt. (a) Bonding Strap Inspect 1 (a) If the bonding strap is installed on a drain mast bolt that is not the forward drain mast bolt, then you have an incorrect installation.

**FIGURE 3: INSPECT THE BONDING STRAP LOCATION (SHEET 2 OF 2)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 37 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT This Figure applies only to: Group 1.** 

**FIGURE 4: MEASURE THE DIAMETER OF THE WASHERS UNDER THE DRAIN MAST BOLTS (SHEET 1 OF 2)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 38 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT**The step numbers shown below agree with the numbers shown in the circle symbols in the figure.
**MORE DATA QTY**  **NAME TASK**  **STEP** Make sure that the diameter of all the washers under the drain mast bolt measures less than 0.55 inch. (a) (b) (c)4 Bolt Locations Diameter of Washers Measure 1

(a) One or two washers may be installed. (b) If the diameter of any washer measures larger than 0.55 inch, then you have an incorrect installation. (c) If no washers are installed, then you have an incorrect installation.

**FIGURE 4: MEASURE THE DIAMETER OF THE WASHERS UNDER THE DRAIN MAST BOLTS (SHEET 2 OF 2)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 39 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT This Figure applies only to: Group 1.** 

**FIGURE 5: MEASURE THE THICKNESS OF THE WASHERS UNDER THE DRAIN MAST BOLTS - INSTRUMENT METHOD**  **(SHEET 1 OF 3)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 40 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT FIGURE 5: MEASURE THE THICKNESS OF THE WASHERS UNDER THE DRAIN MAST BOLTS -**  **INSTRUMENT METHOD (SHEET 2 OF 3)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 41 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT**The step numbers shown below agree with the numbers shown in the circle symbols in the figure.
**MORE DATA QTY**  **NAME TASK**  **STEP** Make sure that the thickness of the washers under the drain mast bolt measures 0.057 - 0.074 inch. (a) (b) (c)3 Bolt Locations Thickness of Washers Measure 1

Make sure that the thickness of the washers and the bonding strap lug under the drain mast bolt measures 0.086 - 0.109 inch. (a) (b) (c) 1 Bolt Location Thickness of Washers and Bonding Strap Lug Measure 2

(a) Measure from the upper surface of the filler to the upper surface of the top washer. Use an instrument that is capable of measuring the geometric step to an accuracy of +/- 0.001 inch. (b) One or two washers may be installed. If one washer is installed, then the thickness must measure within the minimum and maximum range given. (c) If the thickness of the washers or the thickness of the washers and bonding strap do not measure within the minimum and maximum range given, then you have an incorrect installation.

**FIGURE 5: MEASURE THE THICKNESS OF THE WASHERS UNDER THE DRAIN MAST BOLTS - INSTRUMENT METHOD**  **(SHEET 3 OF 3)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 42 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT This Figure applies only to: Group 1.** 

**FIGURE 6: MEASURE THE THICKNESS OF THE WASHERS UNDER THE DRAIN MAST BOLTS - OPTIONAL TOOL METHOD**  **(SHEET 1 OF 4)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 43 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT FIGURE 6: MEASURE THE THICKNESS OF THE WASHERS UNDER THE DRAIN MAST BOLTS - OPTIONAL**  **TOOL METHOD (SHEET 2 OF 4)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 44 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT FIGURE 6: MEASURE THE THICKNESS OF THE WASHERS UNDER THE DRAIN MAST BOLTS - OPTIONAL**  **TOOL METHOD (SHEET 3 OF 4)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 45 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT**The step numbers shown below agree with the numbers shown in the circle symbols in the figure.
**MORE DATA QTY**  **NAME TASK**  **STEP** Make sure that the thickness of the washers under the drain mast bolt is within the maximum limit of 0.074 inch. Do the measurement with the TOOL A MAXIMUM MEASUREMENT (GO GAUGE). If Tool A slides over the top surface of the washer, then the thickness of the washers is within the maximum limit. (a) (b) (c)3 Bolt Locations Thickness ofWashers Compared to Maximum Limit Measure 1

Make sure that the thickness of the washers under the drain mast bolt is within the minimum limit of 0.057 inch. Do the measurement with the TOOL A MINIMUM MEASUREMENT (NO-GO GAUGE). If Tool A does not slide over the top surface of the washer, then the thickness of the washers is within the minimum limit. (a) (b) (d)3 Bolt Locations Thickness ofWashers Compared to Minimum Limit Measure 2

Make sure that the thickness of the washers and the bonding strap lug under the drain mast bolt is within the maximum limit of 0.109 inch. Do themeasurement with the TOOL B MAXIMUM MEASUREMENT (GO GAUGE). If the Tool B slides over the top surface of the washer, then the thickness of the washers is within the maximum limit. (a) (b) (c) 1 Bolt Location Thickness of Washers and Bonding Strap Lug Compared to Maximum Limit Measure 3

Make sure that the thickness of the washers and the bonding strap under the drain mast bolt is withinthe minimum limit of 0.086 inch. Do the measurement with the TOOL B MINIMUM MEASUREMENT (NO-GO GAUGE). If Tool B does not slide over the top surface of the washer, then the thickness of the washers is within the minimum limit. (a) (b) (d) 1 Bolt Location Thickness of Washers and Bonding Strap Lug Compared to Minimum Limit Measure 4

(a) Measure from the upper surface of the filler to the upper surface of the top washer. Put the end of the tool flat on the filler. Slide the tool to a location where the washer protrudes past the bolt head. If necessary, use 15X magnification to visually verify if the tool does, or does not, slide over the washers. (b) One or two washers may be installed. If one washer is installed, then the thickness must measure within the minimum and maximum range given. (c) If the MAXIMUM MEASUREMENT (GO GAUGE) end of the tool does not slide over the top surface of the washer, then you have an incorrect installation. (d) If the MINIMUM MEASUREMENT (NO-GO GAUGE) end of the tool does slide over the top surface of the washer, then you have an incorrect installation.

**FIGURE 6: MEASURE THE THICKNESS OF THE WASHERS UNDER THE DRAIN MAST BOLTS - OPTIONAL TOOL METHOD**  **(SHEET 4 OF 4)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 46 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT This Figure applies only to: Group 1.** 

**FIGURE 7: REMOVE THE DRAIN MAST (SHEET 1 OF 2)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 47 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT CAUTION:**  WHEN YOU REMOVE THE FASTENERS THAT HOLD THE DRAIN MAST, ASK ANOTHER PERSON TO HOLD THE DRAIN MAST FROM THE OUTSIDE OF THE AIRPLANE. IF THE DRAIN MAST FALLS, DAMAGE CAN OCCUR. **CAUTION:** OBEY THE INSTRUCTIONS IN THE STEPS TO REMOVE THE SEALANT FROM THE SKIN. IF YOU DO NOT OBEY THE INSTRUCTIONS, DAMAGE TO THE AIRPLANE SURFACE CAN OCCUR. The step numbers shown below agree with the numbers shown in the circle symbols in the figure.
**MORE DATA SPEC**  **NAME TASK**  **STEP** Loosen the clamp and disconnect the drain mast tube. Make sure that you do not damage the drain mast tube when you disconnect it. Keep the drain mast tube and clamp. - Drain Mast Tube / Clamp Disconnect / Keep 1

Disconnect the drain mast electrical wires at the splices. Keep the drain mast wires. (a) - Drain Mast Wires Disconnect / Keep 2

Remove and discard the drain mast bolts and washers. Make sure that another person holds the drain mast from the outside of the airplane so that the drain mast does not fall. Make sure you do not damage the bonding strap when you remove the bolt. Keep the bonding strap. (a) - Bolts / Wash- ers Remove / Discard 3

Remove and keep the drain mast.

- Drain Mast Remove / Keep 4 Remove the aerodynamic smoother and faying surface sealant from the skin and the drain mast. Make sure you do not damage the skin when you remove the sealant. Make sure you only use approved sealant removal tools. Refer to 737-100/200 AMM 51-31-0 or 737-300/400/500 AMM 51-31-00 as an accepted procedure. 737-100/200 AMM 51-31-0 or 737- 300/400/500 AMM 51-31-00 Sealant Remove 5

(a) The drain mast wires and the bonding strap are connected to the drain mast. They are removed from the airplane when the drain mast is removed.

**FIGURE 7: REMOVE THE DRAIN MAST (SHEET 2 OF 2)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 48 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT This Figure applies only to: Group 1.** 

**FIGURE 8: DO AN HFEC AND DETAILED INSPECTION OF THE SKIN, THE CHANNEL, AND THE FILLERS (SHEET 1 OF 3)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 49 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT FIGURE 8: DO AN HFEC AND DETAILED INSPECTION OF THE SKIN, THE CHANNEL, AND THE FILLERS**  **(SHEET 2 OF 3)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 50 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT**The step numbers shown below agree with the numbers shown in the circle symbols in the figure.
**MORE DATA SPEC**  **QTY NAME**  **TASK STEP**  Do an open hole HFEC inspection of the drain mast bolt holes in accordance with 737 NDT Part 6, 51-00-00, Figure 16. 737 NDT Part 6, 51-00-00, Figure 164 Bolt Hole Locations Bolt Holes Inspect 1

Do an external HFEC inspection of the skin for cracks that start at the drain mast bolt holes in accordance with 737 NDT Part 6, 51-00-00, Figure 4 or 737 NDT Part 6, 51-00-00, Figure 23. Inspect approximately a 0.125 inch zone around each bolt hole. 737 NDT Part 6, 51-00-00, Figure 4 / 737 NDT Part 6, 51-00-00, Figure 23 - Skin Inspect 2

Do an external detailed inspection of the skin for signs of corrosion adjacent to the drain mast bolt holes. - - Skin Inspect 3

Do an internal HFEC inspection of the channel and the fillers for cracks thatstart at the drain mast bolt holes in accordance with 737 NDT Part 6, 51-00-00, Figure 4 or 737 NDT Part 6, 51-00-00, Figure 23. Inspect approximately a 0.125 inch zone around each bolt hole. 737 NDT Part 6, 51-00-00, Figure 4 / 737 NDT Part 6, 51-00-00, Figure 23 - Channel / Fillers Inspect 4

Do an internal detailed inspection of thechannel and the fillers for signs of corrosion adjacent to the drain mast bolt holes. - - Channel / Fillers Inspect 5

**FIGURE 8: DO AN HFEC AND DETAILED INSPECTION OF THE SKIN, THE CHANNEL, AND THE FILLERS (SHEET 3 OF 3)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 51 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT This Figure applies only to: Group 1.** 

**FIGURE 9: INSTALL THE DRAIN MAST (SHEET 1 OF 4)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 52 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT FIGURE 9: INSTALL THE DRAIN MAST**  **(SHEET 2 OF 4)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 53 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT CAUTION:**  OBEY THE INSTRUCTIONS IN THE STEPS TO APPLY THE SEALANT. IF YOU DO NOT OBEY THE INSTRUCTIONS, DAMAGE TO THE AIRPLANE SURFACE CAN OCCUR. The step numbers shown below agree with the numbers shown in the circle symbols in the figure.
**MORE DATA PART NUMBER /**  **SPEC NAME**  **TASK STEP**  Apply sealant BMS 5-95, Type 1, Class B1/2 or Class B-2 to the drain mast and the airplane faying surface. Make sure you do not damage the skin when you apply the sealant. Refer to SOPM 20-50-19, 737- 100/200 AMM 51-31-0 and 737-300/400/500 AMM 51-31-00 as accepted procedures. BMS 5-95, Type 1, Class B-1/2 or Class B-2 / SOPM 20-50- 19, 737-100/200 AMM 51-31-0, 737- 300/400/500 AMM 51-31-00 Drain Mast Seal 1

Put the kept drain mast in position.

- Drain Mast Install / Kept 2

Install new drain mast bolts and washers in accordance with Table 1. Make sure that you install the kept bonding strap at Bolt Location 4 in accordance with Table 1.Use the part numbers and specifications in accordance with Table 1Bolts / Washers / Bonding Strap Install / New / Kept 3

Make a fillet seal (aerodynamic smoother) around the drain mast with sealant BMS 5- 95, Type 1, Class B-1/2 or Class B-2. Make sure you do not damage the skin when you apply the sealant. Refer to SOPM 20-50-19, 737-100/200 AMM 51-31-0 and 737- 300/400/500 AMM 51-31-00 as accepted procedures. BMS 5-95, Type 1, Class B-1/2 or Class B-2 / SOPM 20-50- 19, 737-100/200 AMM 51-31-0, 737- 300/400/500 AMM 51-31-00 Drain Mast Seal 4

Connect the kept drain mast tube to the fitting on the drain mast with the kept clamp. - Drain Mast Tube / Clamp Connect / Kept 5 Connect the kept drain mast electrical wires.

- Drain Mast Wires Connect / Kept 6

Do a check for leaks on the drain mast in accordance with the instructions that follow: Plug the drain mast. Let the water run from the sink of an adjacent lavatory. Check for leaks at the drain mast tube connection to the drain mast. Remove the plug from the drain mast. - Drain Mast / Drain Mast Tube Test 7

Do a check for heating of the drain mast. Refer to 737 737-100/200 AMM 30-71-0 and737-300/400/500 AMM 30-71-00 as accepted procedures. 737-100/200 AMM 30-71-0, 737- 300/400/500 AMM 30-71-00 Drain Mast Test 8

**FIGURE 9: INSTALL THE DRAIN MAST (SHEET 3 OF 4)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 54 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT Table 1: Installation of the Drain Mast Bolts, Washers, and Bonding Strap**  **More Data QTY**  **PART NUMBER NAME**  **BOLT LOCATION** (a) (b) 1 BACB30LM4-4 Bolt Bolt Location 1 (b) 1 NAS1149D0416H Washer (b) 1 NAS1523C4R Seal Washer (a) (b) 1 BACB30LM4-4 Bolt Bolt Location 2 (b) 1 NAS1149D0416H Washer (b) 1 NAS1523C4R Seal Washer (a) (b) 1 BACB30LM4-4 Bolt Bolt Location 3 (b) 1 NAS1149D0416H Washer (b) 1 NAS1523C4R Seal Washer (a) (b) (c) (d) (e) 1 BACB30LM4-4 Bolt Bolt Location 4 (b) (c) (d) (e) 1 NAS1149D0416H Washer (b) (c) (d) (e) 1 NAS1523C4R Seal Washer (b) (c) (d) (e) 1 Kept Part Bonding Strap (a) Apply torque to the drain mast bolts in accordance with the instructions that follow: Apply a torque of 8 - 12 inch-pounds to bolt locations 1 and 4. Apply a torque of 8 - 12 inch-pounds to bolt locations 2 and 3. Apply a torque of 38 - 42 inch-pounds to bolt locations 1 and 4. Apply a torque of 38 - 42 inch-pounds to bolt locations 2 and 3. Apply a final torque of 78 - 82 inch-pounds to bolt locations 1 and 4. Apply a final torque of 78 - 82 inch-pounds to bolt locations 2 and 3. Refer to SOPM 20-50-01 as an accepted procedure. (b) Apply chemical conversion coating Type 2, Class A to the bare surfaces of the washers and bonding strap lug after you install them. Refer to SOPM 20-43-03 as an accepted procedure. Apply one coat of primer BMS 10-11, Type I to the drain mast bolts, washers, and bonding strap lug. Refer to SOPM 20-41-02 as an accepted procedure. (c) This is the forward drain mast bolt location. (d) These are electrical bonding parts. Clean the drain mast bolt, the washers, and the bonding strap before you install them. Refer to SOPM 20-11-03, Cleaning Method CM3, as an accepted procedure. Make sure the bonding area meets electrical bonding requirements. The resistance between the bonding strap and the airplane structure must be less than 0.001 ohm. Refer to SWPM 20-20-00 and SWPM 20-20-10 as accepted procedures. (e) Apply sealant BMS 5-95, Type 1, Class B-1/2 or B-2 to the drain mast bolt, washers, and bonding strap lug. This gives corrosion protection at the electrical bonding location. Refer to SOPM 20-50-19, 737- 100/200 AMM 51-31-0 and 737-300/400/500 AMM 51-31-00 as accepted procedures.

**FIGURE 9: INSTALL THE DRAIN MAST (SHEET 4 OF 4)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 55 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT This Figure applies only to: Group 1.** 

**FIGURE 10: OPTIONAL TOOL A AND TOOL B - MADE BY THE OPERATOR (SHEET 1 OF 3)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 56 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT FIGURE 10: OPTIONAL TOOL A AND TOOL B - MADE BY THE OPERATOR**  **(SHEET 2 OF 3)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 57 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT**The step numbers shown below agree with the numbers shown in the circle symbols in the figure.
**MORE DATA PART NUMBER**  **NAME TASK**  **STEP** Make Tool A from aluminum. (a) (b) (c) (d) (e) Tool A Measuring Tool, Washers Make 1 Make Tool B from aluminum. (a) (b) (c) (d) (e) Tool B Measuring Tool, Washers and Bonding Strap Lug Make 2

(a) The operator can supply any aluminum alloy and heat treat to make the tool. (b) Tolerance for dimensions X.XX is plus or minus 0.03. Tolerance for dimensions X.XXX is plus or minus 0.001. (c) Break all sharp edges. (d) No finish is necessary. (e) Identify each end of the tool as shown. Any marking method is acceptable.

**FIGURE 10: OPTIONAL TOOL A AND TOOL B - MADE BY THE OPERATOR (SHEET 3 OF 3)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 31, 2011 737-53A1318 58 of 58 **BOEING SERVICE BULLETIN 737-53A1318 ALERT**  **ALERT**