### Commercial **Airplanes** 

# 747 Service Bulletin **ALERT Number: 747-25A3640**  Original Issue: January 08, 2014 ATA System: 2551 **SUBJECT:** EQUIPMENT/FURNISHINGS - Electrical/Electronic Equipment Centers - Main Equipment Center Drip Shield Repair Export of this technology is controlled under the United States Export Administration Regulations (EAR) (15 CFR 300-774). 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 © 2014 Boeing. Unpublished Work. All Rights Reserved. Treatment of this document and its content is governed by contract with Boeing. Rights to use this document are licensed on a per aircraft basis and such rights may not be transferable. For more information, contact The Boeing Company. 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, KC-46, KDC-10, MD-10, MD-11, MD-80, MD-88, MD-90, P-8, Poseidon and Boeing liveries 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.

Original Issue: January 08, 2014 747-25A3640 1 of 26 4.0Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: January 08, 2014 747-25A3640 2 of 26 **BOEING SERVICE BULLETIN 747-25A3640 ALERT**  **ALERT**

BLANK PAGE**Table of Contents** Summary...................................................... 5 1. PLANNING INFORMATION ........................................ 9 A. Effectivity................................................ 9 1. Airplanes............................................. 9 2. Spares Affected . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 B. Concurrent Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 C. Reason . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 D. Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 E. Compliance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 F. Approval . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 G. Manpower . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 H. Weight and Balance Changes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 I. Electrical Load Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 J. References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 1. Existing Data: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 2. Data Supplied with this Service Bulletin:. . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3. Installation Drawings Used in the Preparation of this Service Bulletin:. . . . . . . . . . . 14 K. Publications Affected . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 L. Interchangeability and Intermixability of Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 M. Software Accomplishment Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2. MATERIAL INFORMATION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 A. Material - Price and Availability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 B. Industry Support Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 C. Parts Necessary for Each Airplane. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 1. Kits/Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 2. Parts and Materials Supplied by the Operator. . . . . . . . . . . . . . . . . . . . . . . . 17 3. Parts Modified and Reidentified. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 4. Parts Removed and Not Replaced. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 D. Parts Necessary to Change Spares. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 E. Special Tooling - Price and Availability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 F. Special Tooling Necessary to do this Service Bulletin. . . . . . . . . . . . . . . . . . . . . . . 18 3. ACCOMPLISHMENT INSTRUCTIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 A. GENERAL INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 B. WORK INSTRUCTIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 FIGURE 1: MEC DRIP SHIELD FIBERGLASS REINFORCING OVERCOAT INSTALLATION. . . . . 21

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: January 08, 2014 747-25A3640 3 of 26 **BOEING SERVICE BULLETIN 747-25A3640 ALERT**  **ALERT**Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: January 08, 2014 747-25A3640 4 of 26 **BOEING SERVICE BULLETIN 747-25A3640 ALERT**  **ALERT**

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### Commercial **Airplanes** 

# 747 Service Bulletin **ALERT Summary**  **Number: 747-25A3640** Original Issue: January 08, 2014 ATA System: 2551 **SUBJECT:** EQUIPMENT/FURNISHINGS - Electrical/Electronic Equipment Centers - Main Equipment Center Drip Shield 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** Refer to Paragraph 1.B., Concurrent Requirements. **BACKGROUND** This service bulletin will reduce the possibility of water penetration into the main equipment center (MEC). Cracking of the MEC drip shield has allowed water to drip past the MEC drip shield and through the exhaust plenum into the MEC. Water penetration into the MEC could result in an electrical short and potential loss of several functions essential for safe flight. Cracking in the MEC drip shield and exhaust plenum have each been identified as part of the leak path into the MEC. Multiple operators have reported a cracked MEC drip shield. These cracks can allow water to penetrate the MEC drip shield and enter the MEC. This service bulletin is related to service bulletin 747-25A3588 which includes repairs of drip shield cracks, stiffens the drip shield top surface, and installs a fiberglass reinforcing overcoat to the top and sides of the drip shield. Boeing has received reports of additional cracking of the drip shield which is not mitigated by SB 747-25A3588. The reported additional cracking occurs at the lower radius of the MEC drip shield, adjacent to the floor beams. This service bulletin will install a fiberglass reinforcing overcoat to the lower radius area of the MEC drip shield to prevent cracking. This will help prevent water intrusion into the MEC. Boeing Service Related Problem (SRP) 747-SRP-25-0318 is related to this service bulletin. This table is provided to operators for planning purposes only. Refer to the applicable sections for more information.
**Reference Affected**  **Planning Data** Paragraph 1.A.2., Spares Affected No Spares Affected

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: January 08, 2014 747-25A3640 5 of 26**Reference Affected**  **Planning Data** Paragraph 1.E., Compliance and Paragraph 1.F., Approval Yes AD Related Paragraph 1.H., Weight and Balance Changes No Weight and Balance Change Paragraph 1.I., Electrical Load Data No Electrical Load Changed Paragraph 1.K., Publications Affected No Publications Affected Paragraph 1.K., Publications Affected No Airplane Flight Operations Affected (Flight CrewOperations Manual and/or FAA Approved Airplane Flight Manual) Paragraph 2.C.1., Kits/Parts No Kits/Parts Required Paragraph 2.C.2., Parts and Materials Supplied by the Operator Yes Operator Supplied Parts/Material Paragraph 2.F., Special Tooling Necessary to do this Service Bulletin No Special Tooling Required

**ACTION (PRR 85901-128RS)** Gain access to MEC drip shield. Clean MEC drip shield. Install a fiberglass reinforcing overcoat. Close access. **EFFECTIVITY** 747-400/400F Airplanes. 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. Boeing recommends that the change given in this service bulletin be done within 24 months after the original issue date of this service bulletin. **INDUSTRY SUPPORT INFORMATION** Boeing warranty remedies are not available for the repair procedures given in this service bulletin. **MANPOWER Elapsed Hours**  **Total Task Hours Airplanes**  9.00 36.00 All Airplanes Refer to Paragraph 1.G., Manpower. **MATERIAL INFORMATION** Operator Supplied Parts/Materials.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: January 08, 2014 747-25A3640 6 of 26 **BOEING SERVICE BULLETIN 747-25A3640 ALERT**  **ALERT**Refer to Paragraph 2.A., Material - Price and Availability.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: January 08, 2014 747-25A3640 7 of 26 **BOEING SERVICE BULLETIN 747-25A3640 ALERT**  **ALERT**Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: January 08, 2014 747-25A3640 8 of 26 **BOEING SERVICE BULLETIN 747-25A3640 ALERT**  **ALERT**

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### Commercial **Airplanes** 

# 747 Service Bulletin **ALERT Number: 747-25A3640**  Original Issue: January 08, 2014 ATA System: 2551 **SUBJECT:** EQUIPMENT/FURNISHINGS - Electrical/Electronic Equipment Centers - Main Equipment Center Drip Shield 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 D6-30300 Part 3 for Airplane Variable Number, Line Number, and Serial Number data. This service bulletin is for the airplane(s) shown below. Refer to PRR 85901-128RS for data about this change.
**DESCRIPTION CONFIGURATION**  **GROUP** 747-400F or 747-400 BCF airplanes.

- 1 747-400F or 747-400 BCF airplanes which have not accomplished 747-25A3588. 1
747-400F or 747-400 BCF airplanes which have accomplished 747-25A3588. 2
747-400 BCF airplanes that have had the intent of 747-25A3588 incorporated on the airplane during BCF modification. - 2

Airplane Models: 747-400, 747-400F

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: January 08, 2014 747-25A3640 9 of 26**Group Variable Number**  1 RL401 - RL403 1 RL411 - RL436 1 RL451 - RL456 1 RL461 - RL462 1 RL471 - RL481 1 RL491 - RL492 1 RL501 - RL502 1 RL511 - RL516 1 RL521 - RL522 1 RL531 - RL534 1 RL551 1 RL561 1 RL563 - RL568 1 RL571 - RL572 1 RL576 - RL577 1 RL579 1 RL581 - RL586 1 RL651 - RL655 1 RL671 - RL675 1 RL681 - RL684 1 RL751 - RL752 1 RM128 1 RM851 - RM859 1 RM861 - RM862 1 RM871 - RM899 1 RM901 - RM906 1 RM911 1 RR701 1 RR721 - RR724 1 RR746 - RR748 1 RR851 - RR856 1 RR861 - RR862

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: January 08, 2014 747-25A3640 10 of 26 **BOEING SERVICE BULLETIN 747-25A3640 ALERT**  **ALERT Group**  **Variable Number** 1 RR951 - RR952 1 RT021 - RT022 1 RT031 - RT033 2 RT061 1 RT071 - RT072 1 RT101 1 RT161 1 RT164 1 RT456 1 RT501 1 RT506 - RT510 1 RT513 1 RT516 1 RT518 - RT520 1 RT524 1 RT526 1 RT528 2 RT530 1 RT572 - RT579 1 RT642 1 RT655 - RT657 2 RT691 - RT692 1 RT751 - RT752 1 RT781 - RT782 1 RT837 1 RT967 2. Spares Affected None. **B. Concurrent Requirements Group 1, Configuration 1:**  The service bulletin listed below must be done before or at the same time as this service bulletin:

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: January 08, 2014 747-25A3640 11 of 26 **BOEING SERVICE BULLETIN 747-25A3640 ALERT**  **ALERT Description**  **Service Bulletin Company**  Main Equipment Center Drip Shield Repair 747-25A3588 Original Issue, Revision 1, Revision 2, or Revision 3.The Boeing Company **Group 1, Configuration 2; Group 2:** None. **C. Reason** This service bulletin will reduce the possibility of water penetration into the main equipment center (MEC). Cracking of the MEC drip shield has allowed water to drip past the MEC drip shield and through the exhaust plenum into the MEC. Water penetration into the MEC could result in an electrical short and potential loss of several functions essential for safe flight. Cracking in the MEC drip shield and exhaust plenum have each been identified as part of the leak path into the MEC. Multiple operators have reported a cracked MEC drip shield. These cracks can allow water to penetrate the MEC drip shield and enter the MEC. This service bulletin is related to service bulletin 747-25A3588 which includes repairs of drip shield cracks, stiffens the drip shield top surface, and installs a fiberglass reinforcing overcoat to the top and sides of the drip shield. Boeing has received reports of additional cracking of the drip shield which is not mitigated by SB 747-25A3588. The reported additional cracking occurs at the lower radius of the MEC drip shield, adjacent to the floor beams. This service bulletin will install a fiberglass reinforcing overcoat to the lower radius area of the MEC drip shield to prevent cracking. This will help prevent water intrusion into the MEC. Boeing Service Related Problem (SRP) 747-SRP-25-0318 is related to this service bulletin. **D. Description** Gain access to MEC drip shield. Clean MEC drip shield. Install a fiberglass reinforcing overcoat. Close access. The work in this service bulletin is done in the maintenance zone(s) given below. **Group 1:**
**Affected Maintenance Zones Zone**  **Model** 117, 118 747-400, 747-400F **Group 2:**
**Affected Maintenance Zones Zone**  **Model** 117, 118 747-400

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: January 08, 2014 747-25A3640 12 of 26 **BOEING SERVICE BULLETIN 747-25A3640 ALERT**  **ALERT 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 recommends that the change given in this service bulletin be done within 24 months after the original issue date of this service bulletin. **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 change 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**  2.50 10.00 4 Open Access 4.00 16.00 4 FIGURE 1 2.50 10.00 4 Close Access 9.00 36.00 TOTAL FOR EACH AIRPLANE **Group 1, Configuration 1:** This estimate does not include the task hour data given in the service bulletin(s) in Paragraph 1.B., Concurrent Requirements. **H. Weight and Balance Changes** None.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: January 08, 2014 747-25A3640 13 of 26 **BOEING SERVICE BULLETIN 747-25A3640 ALERT**  **ALERT I. Electrical Load Data**  Not applicable. **J. References** 1. Existing Data: a. Engineering Change Memo PRR 85901-128RS b. Boeing Service Bulletin 747-25A3588 c. Boeing Service Related Problem (SRP) 747-SRP-25-0318 d. Service Bulletin Index D6-30300 e. Standard Overhaul Practices Manual (SOPM) 20-30-03, 20-50-01, 20-50-19 f. Standard Wiring Practices Manual (SWPM) 20-10-11, 20-10-12, 20-10-19 g. 747-400 Aircraft Maintenance Manual (AMM) 25-57-01, 25-57-04, 25-57-06, 25-58-01, 25-58-02, 53-21-02 h. 747-400 Structural Repair Manual (SRM) 51-70-06 i. 747-400F Structural Repair Manual (SRM) 51-70-06 2. Data Supplied with this Service Bulletin: None. 3. Installation Drawings Used in the Preparation of this Service Bulletin: None. **K. Publications Affected** 1. Publications: None. 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 does not affect FCS, therefore DTIs are not necessary. **L. Interchangeability and Intermixability of Parts** Accomplishment of this service bulletin does not affect interchangeability or intermixability of parts.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: January 08, 2014 747-25A3640 14 of 26 **BOEING SERVICE BULLETIN 747-25A3640 ALERT**  **ALERT M. Software Accomplishment Summary**  Not affected.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: January 08, 2014 747-25A3640 15 of 26 **BOEING SERVICE BULLETIN 747-25A3640 ALERT**  **ALERT**Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: January 08, 2014 747-25A3640 16 of 26 **BOEING SERVICE BULLETIN 747-25A3640 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 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 The following parts or materials are necessary to do the change in this service bulletin. Parts and materials in the manuals given in Paragraph 1.J., References, can also be necessary. Examine operator part and material supply to make sure all necessary parts and materials are available.
**Notes Name**  **QTY Part Number /**  **Specification** (a) SEALANT 1 Qt. BMS 5-95, Type I, Class B (a) EPOXY RESIN 1 Qt. BMS 8-201, Type III or Type IV (a) FIBERGLASS CLOTH 1 Roll BMS 9-3, Type H, H-2, or H-3, Class 7 (a) Refer to 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.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: January 08, 2014 747-25A3640 17 of 26 **BOEING SERVICE BULLETIN 747-25A3640 ALERT**  **ALERT E. Special Tooling - Price and Availability**  None. **F. Special Tooling Necessary to do this Service Bulletin** No special tools or equipment are necessary to do the change in this service bulletin. But, 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.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: January 08, 2014 747-25A3640 18 of 26 **BOEING SERVICE BULLETIN 747-25A3640 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 – Torque Values: — Values for structural fasteners are given in 747 Structural Repair Manual, Chapter 51. — Values for airframe maintenance tasks are included in Chapter 20 of 747 Airplane Maintenance Manual (AMM). — Values for electrical maintenance tasks are included in Chapter 20 of Standard Wiring Practices Manual (SWPM). — Values for engine maintenance tasks are included in Chapter 70 of 747 Airplane Maintenance Manual (AMM). — Non-standard torque values for maintenance tasks are included in the applicable installation step.
4. Use the approved fastener, process and 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. The necessary conditions for selection of clamp type and size are included in SWPM 20-10-12. If any wire bundle support clamp specified in this service bulletin does not make a correct fit on the wire bundle, refer to SWPM 20-10-12 as an accepted procedure to select a clamp that fits correctly.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: January 08, 2014 747-25A3640 19 of 26 **BOEING SERVICE BULLETIN 747-25A3640 ALERT**  **ALERT**7. If the length of any fastener specified in this service bulletin does not meet installation standards given in SRM Chapter 51, then a fastener of the same specification, or an approved substitute, with a length which meets the installation standards given in SRM Chapter 51 may be used. In addition, washers may be installed for fastener grip length in accordance with SRM Chapter 51. Refer to SOPM 20-50-01 for alternate full threaded fasteners (screws) needed for installation in this service bulletin. 8. 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. 9. 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. 10. 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. 11. If shading is used, shaded areas in Figures are to separate the non-critical and non-authoritative information from the critical and authoritative information. 12. Some steps in the Work Instructions are identified as Required for Compliance (RC). If this service bulletin is mandated by an Airworthiness Directive (AD), then the steps identified as RC must be done to comply with the AD. Alternative procedures for steps not identified with RC can be used if the RC steps can still be done as specified, and the airplane can be put back in a serviceable condition. An Alternative Method of Compliance (AMOC) is not necessary for deviations to steps that are not identified as RC. **B. WORK INSTRUCTIONS** 1. Remove cargo handling equipment between STA 440 and STA 460 and LBL 55 and RBL 55. Refer to 747-400 AMM 25-57-01, 747-400 AMM 25-57-04, 747-400 AMM 25-57-06, 747-400 AMM 25-58-01, and 747-400 AMM 25-58-02 as an accepted procedure. 2. Remove main deck floor panels between STA 440 and STA 460 and LBL 55 and RBL 55. Refer to 747-400 AMM 53-21-02 as an accepted procedure. 3. RC- Install a fiberglass reinforcing overcoat on the main equipment center (MEC) drip shield in accordance with FIGURE 1. 4. Install main deck floor panels between STA 440 and STA 460 and LBL 55 and RBL 55. Refer to 747-400 AMM 53-21-02 as an accepted procedure. 5. Install cargo handling equipment between STA 440 and STA 460 and LBL 55 and RBL 55. Refer to 747-400 AMM 25-57-01, 747-400 AMM 25-57-04, 747-400 AMM 25-57-06, 747-400 AMM 25-58-01, and 747-400 AMM 25-58-02 as an accepted procedure. 6. Put the airplane back to a serviceable condition.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: January 08, 2014 747-25A3640 20 of 26 **BOEING SERVICE BULLETIN 747-25A3640 ALERT**  **ALERT FIGURE 1: MEC DRIP SHIELD FIBERGLASS REINFORCING OVERCOAT INSTALLATION**  **(SHEET 1 OF 6)** Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: January 08, 2014 747-25A3640 21 of 26 **BOEING SERVICE BULLETIN 747-25A3640 ALERT**  **ALERT FIGURE 1: MEC DRIP SHIELD FIBERGLASS REINFORCING OVERCOAT INSTALLATION**  **(SHEET 2 OF 6)** Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: January 08, 2014 747-25A3640 22 of 26 **BOEING SERVICE BULLETIN 747-25A3640 ALERT**  **ALERT FIGURE 1: MEC DRIP SHIELD FIBERGLASS REINFORCING OVERCOAT INSTALLATION**  **(SHEET 3 OF 6)** Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: January 08, 2014 747-25A3640 23 of 26 **BOEING SERVICE BULLETIN 747-25A3640 ALERT**  **ALERT FIGURE 1: MEC DRIP SHIELD FIBERGLASS REINFORCING OVERCOAT INSTALLATION**  **(SHEET 4 OF 6)** Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: January 08, 2014 747-25A3640 24 of 26 **BOEING SERVICE BULLETIN 747-25A3640 ALERT**  **ALERT**The step numbers shown below agree with the numbers shown in the circle symbols in the figure. The QTY numbers shown below are the number of parts necessary for each airplane.
**More Data Qty**  **Identification Name**  **Task Step**  Solvent clean, refer to SOPM 20-30-03as an accepted procedure. Only area tobe covered by fiberglass cloth needs to be cleaned. - - MEC DRIP SHIELD Clean 1

Abrasive clean, refer to SOPM 20-30-03as an accepted procedure. Only area tobe covered by fiberglass cloth needs to be cleaned. - - MEC DRIP SHIELD Clean 2

Solvent clean, refer to SOPM 20-30-03as an accepted procedure. Only area tobe covered by fiberglass cloth needs to be cleaned. - - MEC DRIP SHIELD Clean 3

(a) (c)

- BMS 9-3, TYPE H, H-2 OR H-3, CLASS 7 FIBERGLASS CLOTH Cut 4 (b)

- BMS 8-201, TYPE III OR IV EPOXY RESIN Prepare 5

Make sure that fiberglass cloth is installed flush against the lower floor beam chord as shown. (c) - BMS 9-3, TYPE H, H-2 OR H-3, CLASS 7 FIBERGLASS CLOTH Install (New) 6

Bond using BMS 8- 201 Type III or Type IV. Refer to 747- 400F SRM 51-70-06 or 747-400 SRM 51-70-06 as an accepted procedure. (d) - BMS 8-201, TYPE III OR IV EPOXY RESIN Apply

Refer to SOPM 20-50-19 as an accepted procedure. - BMS 5-95, TYPE I, CLASS B SEALANT Apply 7

**FIGURE 1: MEC DRIP SHIELD FIBERGLASS REINFORCING OVERCOAT INSTALLATION (SHEET 5 OF 6)**  Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: January 08, 2014 747-25A3640 25 of 26 **BOEING SERVICE BULLETIN 747-25A3640 ALERT**  **ALERT More Data**  **Qty Identification**  **Name Task**  **Step** Make sure that fiberglass cloth is installed flush against the lower floor beam chord as shown. (c) - BMS 9-3, TYPE H, H-2 OR H-3, CLASS 7 FIBERGLASS CLOTH Install (New) 8

Bond using BMS 8- 201 Type III or Type IV. Refer to 747- 400F SRM 51-70-06 or 747-400 SRM 51-70-06 as an accepted procedure. (d) - BMS 8-201, TYPE III OR IV EPOXY RESIN Apply

Refer to SOPM 20-50-19 as an accepted procedure. - BMS 5-95, TYPE I, CLASS B SEALANT Apply 9

(a) Cut fiberglass cloth in sections as required. All seams shall overlap 2 inches minimum, including sheetto-sheet and sheet-to-beam. (b) Prepare epoxy laminating resin in sufficient quantity. Work in small batches consistent with working life of resin. (c) Two layers of fiberglass cloth are required. (d) Apply mixed resin and cloth using squeegee or similar tool.

**FIGURE 1: MEC DRIP SHIELD FIBERGLASS REINFORCING OVERCOAT INSTALLATION (SHEET 6 OF 6)**  Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: January 08, 2014 747-25A3640 26 of 26 **BOEING SERVICE BULLETIN 747-25A3640 ALERT**  **ALERT**