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.

ECCN: 9E991

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Unpublished Work.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

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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

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BLANK PAGE
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.

Planning Data Affected Reference

Spares Affected No Paragraph 1.A.2., Spares Affected

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Planning Data Affected Reference

Paragraph 1.E., Compliance and Paragraph

1.F., Approval

AD Related Yes

Weight and Balance Change No Paragraph 1.H., Weight and Balance Changes

Electrical Load Changed No Paragraph 1.I., Electrical Load Data

Publications Affected No Paragraph 1.K., Publications Affected

Airplane Flight Operations Affected (Flight Crew No Paragraph 1.K., Publications Affected

Operations Manual and/or FAA Approved Airplane Flight Manual)

Kits/Parts Required No Paragraph 2.C.1., Kits/Parts

Paragraph 2.C.2., Parts and Materials Supplied

by the Operator

Operator Supplied Parts/Material Yes

Paragraph 2.F., Special Tooling Necessary to

do this Service Bulletin

Special Tooling Required No

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

Airplanes Total Task Hours Elapsed Hours

All Airplanes 36.00 9.00

Refer to Paragraph 1.G., Manpower.

MATERIAL INFORMATION

Operator Supplied Parts/Materials.

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Refer to Paragraph 2.A., Material - Price and Availability.

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BLANK PAGE
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.

GROUP CONFIGURATION DESCRIPTION

1 - 747-400F or 747-400 BCF airplanes.

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

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Variable Number Group

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 1

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ALERT ALERT
Variable Number Group

RR951 - RR952 1

RT021 - RT022 1

RT031 - RT033 1

RT061 2

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 1

RT530 2

RT572 - RT579 1

RT642 1

RT655 - RT657 1

RT691 - RT692 2

RT751 - RT752 1

RT781 - RT782 1

RT837 1

RT967 1

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:

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Company Service Bulletin Description

747-25A3588 Original Issue, Revision 1, Main Equipment Center Drip Shield Repair

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

Model Zone

747-400, 747-400F 117, 118

Group 2:

Affected Maintenance Zones

Model Zone

747-400 117, 118

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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.

Task Number of Persons Task Hours Elapsed Hours

Open Access 4 10.00 2.50

FIGURE 1 4 16.00 4.00

Close Access 4 10.00 2.50

TOTAL FOR EACH AIRPLANE 36.00 9.00

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.

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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.

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M. Software Accomplishment Summary

Not affected.

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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.

Part Number / QTY Name Notes

Specification

BMS 5-95, Type I, 1 Qt. SEALANT (a)

Class B

BMS 8-201, Type 1 Qt. EPOXY RESIN (a)

III or Type IV

BMS 9-3, Type H, 1 Roll FIBERGLASS CLOTH (a)

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.

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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.

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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.

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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

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747-25A3640

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BOEING SERVICE BULLETIN 747-25A3640

ALERT ALERT
FIGURE 1: MEC DRIP SHIELD FIBERGLASS REINFORCING OVERCOAT INSTALLATION

(SHEET 1 OF 6)

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BOEING SERVICE BULLETIN 747-25A3640

ALERT ALERT
FIGURE 1: MEC DRIP SHIELD FIBERGLASS REINFORCING OVERCOAT INSTALLATION

(SHEET 2 OF 6)

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BOEING SERVICE BULLETIN 747-25A3640

ALERT ALERT
FIGURE 1: MEC DRIP SHIELD FIBERGLASS REINFORCING OVERCOAT INSTALLATION

(SHEET 3 OF 6)

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BOEING SERVICE BULLETIN 747-25A3640

ALERT ALERT
FIGURE 1: MEC DRIP SHIELD FIBERGLASS REINFORCING OVERCOAT INSTALLATION

(SHEET 4 OF 6)

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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.

Step Task Name Identification Qty More Data

Solvent clean, refer

to SOPM 20-30-03

as an accepted procedure. Only area to

be covered by fiberglass cloth needs to

be cleaned.

1 Clean MEC DRIP SHIELD - -

Abrasive clean, refer

to SOPM 20-30-03

as an accepted procedure. Only area to

be covered by fiberglass cloth needs to

be cleaned.

2 Clean MEC DRIP SHIELD - -

Solvent clean, refer

to SOPM 20-30-03

as an accepted procedure. Only area to

be covered by fiberglass cloth needs to

be cleaned.

3 Clean MEC DRIP SHIELD - -

BMS 9-3, TYPE H, H-2 - (a) (c)

OR H-3, CLASS 7

4 Cut FIBERGLASS CLOTH

BMS 8-201, TYPE III - (b)

OR IV

5 Prepare EPOXY RESIN

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

6 Install (New) FIBERGLASS CLOTH

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

Apply EPOXY RESIN

Refer to SOPM 20-

50-19 as an accepted procedure.

BMS 5-95, TYPE I, -

CLASS B

7 Apply SEALANT

FIGURE 1: MEC DRIP SHIELD FIBERGLASS REINFORCING OVERCOAT INSTALLATION

(SHEET 5 OF 6)

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BOEING SERVICE BULLETIN 747-25A3640

ALERT ALERT
Step Task Name Identification Qty More Data

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

8 Install (New) FIBERGLASS CLOTH

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

Apply EPOXY RESIN

Refer to SOPM 20-

50-19 as an accepted procedure.

BMS 5-95, TYPE I, -

CLASS B

9 Apply SEALANT

(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)

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ALERT ALERT