# Boeing Alert Service Bulletin 747-25A3555: Revision 1

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- Document: [Boeing Alert Service Bulletin 747-25A3555](https://openairdocs.org/service-documents/boeing/747-25a3555.md)
- Title as filed: U.S. DOT/FAA - Boeing Service Bulletin
- Pages: 141
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## Text

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### Page 1

Commercial 
Airplanes
747
Service Bulletin
ALERT
Number: 747-25A3555
Original Issue: November 04, 2009
Revision 1: July 27, 2011
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 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.
9E991ECCN:
BOEING PROPRIETARY, CONFIDENTIAL, AND/OR TRADE SECRET
Copyright © 2009 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Unpublished Work - All Rights Reserved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.
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Table of Contents
Revision Transmittal Sheet ............................................ 5
Summary ...................................................... 7
1. PLANNING INFORMATION ........................................ 1 1
A. Effectivity ............................................... 1 1
1. Airplanes ............................................ 1 1
2. Spares Affected ........................................ 1 5
B. Concurrent Requirements ...................................... 1 5
C. Reason ................................................ 1 6
D. Description .............................................. 1 7
E. Compliance .............................................. 1 7
F. Approval ............................................... 1 9
G. Manpower .............................................. 1 9
H. Weight and Balance Changes .................................... 2 2
I. Electrical Load Data ......................................... 2 3
J. References .............................................. 2 3
1. Existing Data .......................................... 2 3
2. Data supplied with this Service Bulletin ............................ 2 3
3. Installation Drawings Used in the Preparation of this Service Bulletin ............ 2 3
K. Publications Affected ........................................ 2 3
L. Interchangeability and Intermixability of Parts ........................... 2 4
2. MATERIAL INFORMATION ........................................ 2 5
A. Material - Price and Availability ................................... 2 5
B. Industry Support Information .................................... 2 9
C. Parts Necessary For Each Airplane ................................. 2 9
1. Kits/Parts ............................................ 2 9
2. Parts and Materials Supplied by the Operator ........................ 3 5
3. Parts Modified and Reidentified ................................ 3 5
4. Parts Removed and Not Replaced .............................. 3 6
D. Parts Necessary to Change Spares ................................. 3 6
E. Special Tooling - Price and Availability ............................... 3 6
F. Special Tooling Necessary to do this Service Bulletin ....................... 3 6
3. ACCOMPLISHMENT INSTRUCTIONS .................................. 3 7
A. GENERAL INFORMATION ..................................... 3 7
B. WORK INSTRUCTIONS ....................................... 3 8
FIGURE 1: FORWARD ALUMINUM GUTTER REINFORCING BRACKET INSTALLATION ...... 4 2
FIGURE 2: AFT ALUMINUM GUTTER REINFORCING BRACKET INSTALLATION [Group 1, 3] . . . 52
FIGURE 3: AFT ALUMINUM GUTTER REINFORCING BRACKET INSTALLATION [Group 2] .... 5 8
FIGURE 4: FLOOR PANEL REMOVAL .................................. 6 4
FIGURE 5: FLOOR PANEL MODIFICATION ............................... 6 7
FIGURE 6: FLANGED SLEEVE INSTALLATION ............................. 7 0
FIGURE 7: LEFT SIDE DRAIN TUBE INSTALLATION [Group 1, 3] ................... 7 4
FIGURE 8: RIGHT SIDE DRAIN TUBE INSTALLATION [Group 1, 3] .................. 8 3
FIGURE 9: LEFT SIDE DRAIN TUBE INSTALLATION [Group 2] .................... 9 1
FIGURE 10: RIGHT SIDE DRAIN TUBE INSTALLATION [Group 2] .................... 9 8
FIGURE 11: FLOOR PANEL INSTALLATION ............................... 1 0 5
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FIGURE 12: EXHAUST PLENUM SEALING ............................... 1 0 8
FIGURE 13: MEC DRIP SHIELD STIFFENER REMOVAL [Group 3] .................. 1 1 3
FIGURE 14: MEC DRIP SHIELD CLEANING AND PREPARATION ................... 1 1 6
FIGURE 15: REPAIR OF HOLES IN MEC DRIP SHIELD ........................ 1 2 0
FIGURE 16: MEC DRIP SHIELD PANEL STIFFENER INSTALLATION ................. 1 2 3
FIGURE 17: MEC DRIP SHIELD FIBERGLASS REINFORCING OVERCOAT INSTALLATION .... 1 2 8
FIGURE 18: CARGO LINER SUPPORT REMOVAL ........................... 1 3 2
FIGURE 19: CARGO LINER SUPPORT INSTALLATION ........................ 1 3 5
APPENDIX A: FABRICATION INSTRUCTIONS FOR 284U1135-107 AND 284U1135-108 ....... 1 3 8
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Commercial 
Airplanes
747
Service Bulletin
ALERT
Revision Transmittal SheetNumber: 747-25A3555Original Issue: November 04, 2009
Revision 1: July 27, 2011
ATA System: 2551
SUBJECT: EQUIPMENT/FURNISHINGS - Electrical/Electronic Equipment Centers - Main
Equipment Center Drip Shield Repair
This revision includes all pages of the service bulletin.
COMPLIANCE INFORMATION RELATED TO THIS REVISION
Federal Aviation Administration (FAA) Notice of Proposed Rule Making NPRM 2010-NM-035-AD, is related to
this service bulletin.
No more work is necessary on the airplane(s) changed in accordance with the original issue of this service
bulletin.
REASON FOR REVISION
This revision is sent to incorporate changes found during validation of the initial release of the service bulletin.
These sections were changed:
1. Section 1.G., Manpower - corrected applicable figures for different groupings and work packages.
2. Section 2.A., Material - Price and Availability - Corrected Note (b) to reference OPTION #2 for all Groups.
3. Section 2.C.2., Parts and Materials Supplied by the Operator - Changed name of BMS 5-92 to ADHESIVE,
added BMS 5-95, added type and class information for all materials.
4. Section 3.B., Work Instructions - Work Packages 1 and 2 - added reference to Digital Interface Unit in
removal and installation of E/E rack components.
5. Section 3.B., Work Instructions - Work Package 1 - Added steps for removal/installation of cargo liner
support (Figures 18 and 19)
6. Figure 1 - changed locating dimensions for the 284U1135-77/-78 brackets.
7. Figure 2 - corrected the quantity of existing fasteners to be removed.
8. Figure 7 - Left side, forward drain tube routing was changed due to interference with an existing pitot/static
shroud.
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9. Figure 9 - Left side, forward drain tube routing was changed due to interference with an existing pitot/static
shroud.
10. Figure 16 - Added new instructions to add a fillet around the panel stiffeners to reduce chance of trapping
air bubbles under fiberglass overcoat.
11. Figure 16 - Added new note allowing trimming of the panel stiffeners.
12. Figure 18 - New figure giving instructions for removing cargo liner support.
13. Figure 19 - New figure giving instructions for installation of cargo liner support.
Vertical lines are put on the left edge of each page, except in Paragraph 1.A., Effectivity, to show the location
of important changes.
Pages with no vertical lines have no important changes.
As a part of a service bulletin validation program, this change was completed on airplane RT438 by Service
Bulletin 747-25A3555 Original Issue before the release of Revision 01 of this service bulletin. The change
completed on airplane RT438 by Service Bulletin 747-25A3555 Original Issue is equivalent to the release of
Revision 01 of this service bulletin. Airplane RT438 has the configuration of a Group 1 airplane.
REVISION HISTORY
November 04, 2009Original Issue:
July 27, 2011Revision 1:
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Commercial 
Airplanes
747
Service Bulletin
ALERT
SummaryNumber: 747-25A3555Original Issue: November 04, 2009
Revision 1: July 27, 2011
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
None.
BACKGROUND
This service bulletin will reduce the possibility of water penetration into the main equipment center (MEC).
Cracking of the MEC drip shield gutters 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 loss of flight critical systems.
An operator experienced a multi power system loss in-flight of #1, 2 & 3 AC electrical power systems located in
the MEC. The loss of AC power engaged the emergency back-up power system, allowing the plane to land
safely.
The forward MEC drip shield gutters and exhaust plenum have each been identified as part of the leak path into
the MEC. Multiple operators have reported cracked MEC drip shield gutters and upper surface. These cracks
can allow water to penetrate the MEC drip shield and enter the MEC.
This service bulletin will install aluminum gutter reinforcing brackets to correct the cracking in the MEC drip shield
gutters. Flanged sleeves and drain tubes will be installed in the lower surface of the exhaust plenum to allow
water to drain away from the MEC as an interim action. A fiberglass reinforcing overcoat will be installed as a
terminating action.
Boeing Service Related Problem (SRP) 747-SRP-25-0277 is related to this service bulletin.
As a part of a service bulletin validation program, this change was completed on airplane RT438 by Service
Bulletin 747-25A3555 Original Issue before the release of Revision 01 of this service bulletin. The change
completed on airplane RT438 by Service Bulletin 747-25A3555 Original Issue is equivalent to the release of
Revision 01 of this service bulletin. Airplane RT438 has the configuration of a Group 1 airplane.
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ACTION (PRR 85901-95RS)
All operators will add aluminum gutter reinforcing brackets to forward and aft MEC drip shield gutters. Due to
the difficulty of accessing the top surface of the MEC drip shield, an interim action is available. The interim action
installs flanged sleeves and drain tubes to the lower surface of the exhaust plenum. The terminating action is
to add a fiberglass reinforcing overcoat to the MEC drip shield.
EFFECTIVITY
747-400/-400D Airplanes. Refer to Paragraph 1.A.1., Airplanes for the list of affected airplanes.
COMPLIANCE
Federal Aviation Administration (FAA) Notice of Proposed Rule Making 2010-NM-035-AD, is related to this
service bulletin.
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 configuration changes given in this service bulletin.
MANPOWER
Group 1:
Elapsed HoursTotal Task HoursAirplanes
14.2519.00Work Package 1
20.5520.55Work Package 2
23.0062.00Work Package 3
Group 2:
Elapsed HoursTotal Task HoursAirplanes
13.7518.50Work Package 1
21.8521.85Work Package 2
23.0062.00Work Package 3
Group 3:
Elapsed HoursTotal Task HoursAirplanes
14.2519.00Work Package 1
20.5520.55Work Package 2
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Group 3:
Elapsed HoursTotal Task HoursAirplanes
23.7562.75Work Package 3
MATERIAL INFORMATION
Boeing Supplied Kits/Parts.
Refer to Paragraph 2.A., Material - Price and Availability.
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BOEING SERVICE BULLETIN 747-25A3555
ALERT  ALERT
ALL OPERATORS WILL ADD ALUMINUM
GUTTER REINFORCING BRACKETS TO
FORWARD AND AFT MEC DRIP SHIELD
GUTTERS. THE INTERIM ACTION INSTALLS
FLANGED SLEEVES AND DRAIN TUBES TO  THE LOWER SURFACE OF THE EXHAUST  000
PLENUM. THE TERMINATING ACTION IS TO
ADD A FIBERGLASS REINFORCING
OVERCOAT TO THE MEC DRIP SHIELD
STA
460
STA
440
1737897
Original Issue: November 04, 2009
Revision 1: July 27, 2011  747-25A3555
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Commercial 
Airplanes
747
Service Bulletin
ALERT
Number: 747-25A3555
Original Issue: November 04, 2009
Revision 1: July 27, 2011
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 Document D6-30300 Part 3 for Airplane Variable Number, Line
Number, and Serial Number data.
This service bulletin is for the airplanes shown below. Refer to PRR 85901-95RS for data about
this change.
DESCRIPTIONCONFIGURATIONGROUP
747-400 Passenger airplanes prior to line number 982 that do not
have existing MEC drip shield stiffeners installed
-1
747-400/-400D Passenger airplanes line number 982 and later.-2
747-400 Passenger airplanes prior to line number 982 that have
existing MEC drip shield stiffeners installed
-3
Airplane Models:
747-400, 747-400D
GroupVariable Number
2RF001 - RF006
2RM001 - RM007
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GroupVariable Number
2RM010 - RM013
2RM021 - RM024
2RM026 - RM030
2RM036 - RM045
2RM051 - RM053
2RM071
2RM081 - RM084
2RM091
2RM096 - RM097
2RM116 - RM117
2RM126 - RM127
2RM129 - RM132
2RM136 - RM147
2RM156 - RM158
2RM166 - RM177
2RM191 - RM192
2RM231 - RM233
2RM241 - RM246
2RM261 - RM264
2RM316 - RM318
2RM331 - RM333
2RM341
2RM351 - RM355
2RM366 - RM367
2RM401 - RM403
2RM426
2RM431
2RM441 - RM443
2RM445
2RM801 - RM803
2RM811 - RM813
3RT001 - RT005
1RT006 - RT009
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GroupVariable Number
2RT010 - RT014
2RT034 - RT035
3RT041 - RT043
1RT045 - RT047
1RT073 - RT074
1RT101 - RT103
1RT121
1RT131 - RT133
2RT134 - RT137
2RT151 - RT152
2RT162 - RT163
2RT165 - RT168
3RT401 - RT410
2RT411 - RT412
3RT431 - RT436
1RT437 - RT441
2RT442 - RT447
3RT451 - RT455
1RT457 - RT460
1RT462 - RT464
2RT466 - RT469
3RT471 - RT487
1RT488 - RT496
2RT497 - RT499
3RT502 - RT505
1RT511 - RT512
1RT514 - RT515
1RT517
2RT521 - RT523
2RT525 - RT527
2RT529 - RT530
3RT531 - RT533
1RT534 - RT535
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GroupVariable Number
3RT551 - RT560
1RT561 - RT568
3RT571
1RT580
2RT581 - RT588
2RT590
3RT591
3RT601 - RT608
1RT609 - RT620
2RT621 - RT630
1RT633 - RT634
2RT636 - RT640
3RT641
3RT643 - RT650
1RT651 - RT654
3RT671 - RT672
1RT673
3RT681 - RT682
3RT691 - RT693
1RT694 - RT696
2RT697 - RT699
3RT701 - RT702
1RT703 - RT704
3RT711
1RT712 - RT717
3RT741
1RT742
1RT744 - RT745
2RT746 - RT750
1RT753 - RT755
2RT756 - RT757
3RT776
1RT783
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GroupVariable Number
2RT784
2RT801 - RT803
2RT811 - RT814
2RT831 - RT835
1RT861 - RT864
1RT877 - RT878
2RT879 - RT880
1RT931 - RT932
2RT945 - RT949
1RT951 - RT953
2RT954 - RT955
2RT966
2RU001 - RU006
2RU016 - RU017
2RU031 - RU032
2RU051 - RU052
2RU059 - RU062
2RU081 - RU083
2RU101 - RU102
2RU121 - RU132
1RU801 - RU808
2RU809
1RU831 - RU837
2RU838 - RU841
2. Spares Affected
None.
B. Concurrent Requirements
None.
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C. Reason
This service bulletin will reduce the possibility of water penetration into the main equipment center
(MEC). Cracking of the MEC drip shield gutters 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 loss of flight
critical systems.
An operator experienced a multi power system loss in-flight of #1, 2 & 3 AC electrical power systems
located in the MEC. The loss of AC power engaged the emergency back-up power system, allowing
the plane to land safely.
The forward MEC drip shield gutters and exhaust plenum have each been identified as part of the leak
path into the MEC. Multiple operators have reported cracked MEC drip shield gutters and upper surface.
These cracks can allow water to penetrate the MEC drip shield and enter the MEC.
This service bulletin will install aluminum gutter reinforcing brackets to correct the cracking in the MEC
drip shield gutters. Flanged sleeves and drain tubes will be installed in the lower surface of the exhaust
plenum to allow water to drain away from the MEC as an interim action. A fiberglass reinforcing overcoat
will be installed as a terminating action.
Boeing Service Related Problem (SRP) 747-SRP-25-0277 is related to this service bulletin.
As a part of a service bulletin validation program, this change was completed on airplane RT438 by
Service Bulletin 747-25A3555 Original Issue before the release of Revision 01 of this service bulletin.
The change completed on airplane RT438 by Service Bulletin 747-25A3555 Original Issue is equivalent
to the release of Revision 01 of this service bulletin. Airplane RT438 has the configuration of a Group
1 airplane.
Revision 01 is sent to incorporate changes found during validation of the initial release of the service
bulletin.
These sections were changed:
1. Section 1.G., Manpower - corrected applicable figures for different groupings and work packages.
2. Section 2.A., Material - Price and Availability - Corrected Note (b) to reference OPTION #2 for all
Groups.
3. Section 2.C.2., Parts and MAterials Supplied by the Operator - Changed name of BMS 5-92 to
ADHESIVE, added BMS 5-95, added type and class information for all materials.
4. Section 3.B., Work Instructions - Work Packages 1 and 2 - added reference to Digital Interface
Unit in removal and installation of E/E rack components.
5. Section 3.B., Work Instructions - Work Package 1 - Added steps for removal/installation of cargo
liner support (Figures 18 and 19)
6. Figure 1 - changed locating dimensions for the 284U1135-77/-78 brackets.
7. Figure 2 - corrected the quantity of existing fasteners to be removed.
8. Figure 7 - Left side, forward drain tube routing was changed due to interference with an existing
pitot/static shroud.
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Original Issue: November 04, 2009
747-25A3555Revision 1: July 27, 2011
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ALERTALERT

### Page 17

9. Figure 9 - Left side, forward drain tube routing was changed due to interference with an existing
pitot/static shroud.
10. Figure 16 - Added new instructions to add a fillet around the panel stiffeners to reduce chance of
trapping air bubbles under fiberglass overcoat.
11. Figure 16 - Added new note allowing trimming of the panel stiffeners.
12. Figure 18 - New figure giving instructions for removing cargo liner support.
13. Figure 19 - New figure giving instructions for installation of cargo liner support.
D. Description
All operators will add aluminum gutter reinforcing brackets to forward and aft MEC drip shield gutters.
Due to the difficulty of accessing the top surface of the MEC drip shield, an interim action is available.
The interim action installs flanged sleeves and drain tubes to the lower surface of the exhaust plenum.
The terminating action is to add a fiberglass reinforcing overcoat to the MEC drip shield.
Revision 01 - No more work is necessary on airplanes changed in accordance with the original issue
of this service bulletin.
The work in this service bulletin is done in the maintenance zone(s) given below.
Group 1-2:
Affected Maintenance Zones
ZoneModel
117, 118747-400, 747-400D
Group 3:
Affected Maintenance Zones
ZoneModel
117, 118747-400
E. Compliance
Federal Aviation Administration (FAA) Notice of Proposed Rule Making 2010-NM-035-AD, is related
to this service bulletin.
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.
Within 24 months after the original issue date of this service bulletin, install MEC drip shield aluminum
gutter reinforcing brackets and add reinforcing fiberglass overcoat to the top surface of the MEC drip
shield as specified in Table 1: MEC drip shield modification OPTION #1
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OR,
within 24 months after the original issue date of this service bulletin, install MEC drip shield aluminum
gutter reinforcing brackets, drain system and flanges on the MEC exhaust plenum and, within 8 years
after the original issue date of this service bulletin, add a reinforcing fiberglass overcoat to the top
surface of the MEC drip shield as specified in Table 2: MEC drip shield modification OPTION #2.
Table 1: MEC drip shield modification OPTION #1
Repeat Interval
(Not to Exceed)
Compliance TimeActionCondition
-Within 24 months
after the original is-
sue date of this
service bulletin
Install MEC drip shield
aluminum gutter reinforc-
ing brackets in accor-
dance with Accomplish-
ment Instructions 3.B.,
Work Package 1
All airplanes
-Within 24 months
after the original is-
sue date of this
service bulletin
Add a reinforcing fiber-
glass overcoat to the top
surface of the MEC drip
shield in accordance with
Accomplishment Instruc-
tions 3.B., Work Package
3 (a)
All airplanes
(a) The reinforcing fiberglass overcoat is the terminating action to this service bulletin.
Table 2: MEC drip shield modification OPTION #2
Repeat Interval
(Not to Exceed)
Compliance TimeActionCondition
-Within 24 months
after the original is-
sue date of this
service bulletin
Install MEC drip shield
aluminum gutter reinforc-
ing brackets in accor-
dance with Accomplish-
ment Instructions 3.B.,
Work Package 1
All airplanes
-Within 24 months
after the original is-
sue date of this
service bulletin
Install MEC drip shield
drain system in accor-
dance with Accomplish-
ment Instructions 3.B.,
Work Package 2
All airplanes
-Within 8 years after
the original issue
date of this service
bulletin
Add a reinforcing fiber-
glass overcoat to the top
surface of the MEC drip
shield in accordance with
Accomplishment Instruc-
tions 3.B., Work Package
3 (a)
All airplanes
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Table 2: MEC drip shield modification OPTION #2
Repeat Interval
(Not to Exceed)
Compliance TimeActionCondition
(a) The reinforcing fiberglass overcoat is the terminating action to 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.
Group 1, 3:
Work Package 1- MEC Drip Shield Aluminum Gutter Reinforcing Bracket Installation
Elapsed HoursTask-HoursNumber of Per-
sons
Task
2.502.501Open Access
2.254.502Figure 1
3.003.001Figure 2
1.252.502Figure 18
1.252.502Figure 19
2.502.501Close Access
1.501.501Test
14.2519.00Total per airplane
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Work Package Number 1 can be done at the same time as Work Package 2 and 3.
Group 2:
Work Package 1- MEC Drip Shield Aluminum Gutter Reinforcing Bracket Installation
Elapsed HoursTask-HoursNumber of Per-
sons
Task
2.502.501Open Access
2.254.502Figure 1
2.502.501Figure 3
2.502.502Figure 18
2.502.502Figure 19
2.502.501Close Access
1.501.501Test
13.7518.50Total per airplane
Work Package Number 1 can be done at the same time as Work Package 2 and 3.
Group 1, 3:
Work Package 2- MEC Drip Shield Drain System Installation
Elapsed HoursTask-HoursNumber of Per-
sons
Task
2.502.501Open Access
1.001.001Figure 4
0.750.751Figure 5
2.102.101Figure 6
3.103.101Figure 7
3.103.101Figure 8
1.001.001Figure 11
3.003.001Figure 12
2.502.501Close Access
1.501.501Test
20.5520.55Total per airplane
Work Package Number 2 can be done at the same time as Work Package 1 and 3
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Group 2:
Work Package 2- MEC Drip Shield Drain System Installation
Elapsed HoursTask-HoursNumber of Per-
sons
Task
2.502.501Open Access
1.001.001Figure 4
0.750.751Figure 5
2.102.101Figure 6
3.753.751Figure 9
3.753.751Figure 10
1.001.001Figure 11
3.003.001Figure 12
2.502.501Close Access
1.501.501Test
21.8521.85Total per airplane
Work Package Number 2 can be done at the same time as Work Package 1 and 3
Group 1-2:
Work Package 3- MEC Drip Shield Reinforcing Fiberglass Overcoat
Elapsed HoursTask-HoursNumber of Per-
sons
Task
6.0024.004Open Access
2.752.751Figure 14
3.503.501Figure 15
3.006.002Figure 16
1.751.751Figure 17
6.0024.004Close Access
23.0062.00Total per airplane
Work Package Number 3 can be done at the same time as Work Package 1 and 2
Group 3:
Work Package 3- MEC Drip Shield Reinforcing Fiberglass Overcoat
Elapsed HoursTask-HoursNumber of Per-
sons
Task
6.0024.004Open Access
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Group 3:
Work Package 3- MEC Drip Shield Reinforcing Fiberglass Overcoat
Elapsed HoursTask-HoursNumber of Per-
sons
Task
0.750.751Figure 13
2.752.751Figure 14
3.503.501Figure 15
3.006.002Figure 16
1.751.751Figure 17
6.0024.004Close Access
23.7562.75Total per airplane
Work Package Number 3 can be done at the same time as Work Package 1 and 2
H. Weight and Balance Changes
Group 1:
Change in Moment
(Pound-Inches)
Change in Weight
(Pounds)Airplane
+2025.0+4.5Work Package 1
+11970.0+26.6Work Package 2
+765.0+1.7Work Package 3
Group 2:
Change in Moment
(Pound-Inches)
Change in Weight
(Pounds)Airplane
+2250.0+5.0Work Package 1
+11745.0+26.1Work Package 2
+765.0+1.7Work Package 3
Group 3:
Change in Moment
(Pound-Inches)
Change in Weight
(Pounds)Airplane
+2025.0+4.5Work Package 1
+11970.0+26.6Work Package 2
+540+1.2Work Package 3
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I. Electrical Load Data
Not changed.
J. References
1. Existing Data
a. Engineering Change Memo PRR 85901-95RS
b. Boeing Service Related Problem (SRP) 747-SRP-25-0277
c. Federal Aviation Administration (FAA) Notice of Proposed Rule Making (NPRM)
2010-NM-035-AD
d. Standard Overhaul Practices Manual (SOPM) 20-30-03, 20-41-02, 20-43-03, 20-50-10,
20-50-12
e. Standard Wiring Practices Manual (SWPM) 20-10-11, 20-10-12, 20-10-19
f. 747-400 Aircraft Maintenance Manual (AMM) 20-11-22, 22-11-01, 23-38-01, 24-23-01,
24-23-05, 25-00-00, 25-31-00, 25-40-01, 29-33-02, 34-61-01, 53-21-02, 77-31-03
g. 747-400 Structural Repair Manual (SRM) 51-70-06, Chapter 51
2. Data supplied with this Service Bulletin
None.
3. Installation Drawings Used in the Preparation of this Service Bulletin
TitleDrawing Number
MOISTURE SHROUD & DRAIN TUBE INSTL - ELEX EQUIP CTR.284U1104
FLOOR PANEL INSTALLATION - ELEX EQUIP CTR.284U1107
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-SectionPublication
25-51, 51-41747 Illustrated Parts Catalog
2. Damage Tolerance Based Structural Inspections:
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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
Refer to Paragraph 2.C., Parts Necessary for Each Airplane, for interchangeability and intermixability
information.
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2.    MATERIAL INFORMATION
A. Material - Price and Availability
Boeing can supply the kits/parts shown in Paragraph 2.C., Parts Necessary for Each Airplane as shown
below. If there is a limit to the quantity (QTY) of available kits/parts, a supply sequence is given by
Spares. More kits/parts become available as shown in the Reorder Lead Time (ROLT). ROLT is
calculated from the date Boeing gets the purchase order.
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Group 1, 3:
Unit Price thru
December 31,
2009
ROLT
(Weeks)
QTYDateNameKit Number
$2,408.00306006/15/09Top Kit - MEC DRIP
SHIELD REPAIR
015U1854-1 (a)
2007/14/09
2008/11/09
2009/09/09
2510/07/09
2511/04/09
2512/04/09
2501/12/10
2502/09/10
2503/09/10
2504/06/10
905/04/10
$8,612.00431506/15/09Top Kit - MEC DRIP
SHIELD REPAIR
015U1854-2 (b)
1508/05/09
1509/02/09
1510/01/09
1510/29/09
2011/30/09
2001/06/10
2002/03/10
2003/03/10
2003/31/10
2004/28/10
2005/26/10
2006/24/10
2007/23/10
2008/20/10
2009/20/10
1412/06/10
$577.0084004/22/09PANEL STIFFENER284U1135-82 (a)
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Group 1, 3:
Unit Price thru
December 31,
2009
ROLT
(Weeks)
QTYDateNameKit Number
04/29/09 40
4005/06/09
4005/13/09
4005/20/09
4005/28/09
4006/04/09
2006/11/09
(a) All Group 1 and 3 operators.
(b) Group 1 and 3 operators who choose OPTION #2 for incorporating this service bulletin. Refer
to Paragraph 1.E., Compliance to determine appropriate incorporation option.
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Group 2:
Unit Price thru
December 31,
2009
ROLT
(Weeks)
QTYDateNameKit Number
$2,404.0030506/12/09Top Kit - MEC DRIP
SHIELD REPAIR
015U1854-3 (a)
507/13/09
1508/10/09
509/08/09
$8,982.0043506/30/09Top Kit - MEC DRIP
SHIELD REPAIR
015U1854-4 (b)
508/05/09
509/02/09
510/01/09
510/29/09
512/14/09
$577.0084004/22/09PANEL STIFFENER284U1135-82 (a)
4004/29/09
4005/06/09
4005/13/09
4005/20/09
4005/28/09
4006/04/09
2006/11/09
(a) All Group 2 operators.
(b) Group 2 operators who choose OPTION #2 for incorporating this service bulletin. Refer to
Paragraph 1.E., Compliance to determine appropriate incorporation option.
The kits/parts are subject to the terms and conditions of the Boeing standard purchase order
acknowledgment. After the Unit Price date, new price and ROLT data is applicable. Prices are in United
States dollars. Terms: Net 30 days.
Reference this service bulletin and submit your purchase order by one of the methods that follow:
1. Order on-line via ATA Spec 2000 or Boeing Part Page
2. Fax to (206) 662-7145
3. Mail to:
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Spares Customer Support - MC 36-65
Boeing Spares Department
P.O. Box 3707
Seattle, Washington 98124-2207 USA
B. Industry Support Information
Boeing warranty remedies are not available for the configuration changes given in this service bulletin.
C. Parts Necessary For Each Airplane
1. Kits/Parts
To get the kits/parts shown below, refer to Paragraph 2.A., Material - Price and Availability.
NOTE: One top kit and the items shown in Paragraph 2.C.2., Parts and Materials Supplied by
the Operator, are necessary for each airplane. The Top Kit is divided into Figure kits for
each installation figure shown in the table below.
Figure Kit
876321Top Kit
----11015U1854-1
111---015U1854-2
---1-1015U1854-3
--1---015U1854-4
Figure Kit
109Top Kit
--015U1854-1
--015U1854-2
--015U1854-3
11015U1854-4
Group 1, 3:
KIT 015U1854-1
NOTES
Existing Part
NumberName
Figure
New Part Number
21
QTY
MOISTURE
SHROUD BRACK-
ET
2284U1135-76
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Group 1, 3:
KIT 015U1854-1
NOTES
Existing Part
NumberName
Figure
New Part Number
21
QTY
MOISTURE
SHROUD BRACK-
ET
1284U1135-77
MOISTURE
SHROUD BRACK-
ET
1284U1135-78
MOISTURE
SHROUD BRACK-
ET
1284U1135-79
MOISTURE
SHROUD BRACK-
ET
2284U1135-80
MOISTURE
SHROUD BRACK-
ET
1284U1135-81
BOLT, PROTRUD-
ING HD
2214BACB30VT5HK4
BOLT, PROTRUD-
ING HD
55BACB30VT5HK5
BOLT28BACB30VT6K5
COLLAR,
PRELOAD
2125BACC30BH5
COLLAR10BACC30BH6
FILLER2BACF3F010G010NN
FILLER2BACF3F010J010NN
NUT, SPACER
PLATE, LIGHT
DUTY
2BACN10TL3-12
NUTPLATE4BACN10TL3-6
RIVET, UNIVER-
SAL HD
5BACR15BB4AD10C
RIVETS4BACR15BB4AD5C
RIVET, UNIVER-
SAL HD
10BACR15BB4AD7C
RIVET, BLIND2BACR15FR4E5R
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Group 1, 3:
KIT 015U1854-1
NOTES
Existing Part
NumberName
Figure
New Part Number
21
QTY
WASHER2NAS1149DN432J
Group 1, 3:
KIT 015U1854-2
NOTES
Existing Part
NumberName
Figure
New Part Number
876
QTY
LACING TAPE1015U1806-5
TYGON TUBING22015U1854-100
FLANGED
SLEEVE
2005-131384
FITTING221401-007
DRAIN SPUD AS-
SY
1284T1213-11
DRAIN SPUD AS-
SY
1284T1213-13
DRAIN SPUD AS-
SY
2284T1213-9
GROMMET169B47961-5
CLAMP, LOOP1212BACC10DK16
NUT, SPACER
PLATE
11BACN10GH3A20
NUT-SPACER
PLATE
11BACN10GH3A4
NUTPLATE11BACN10MK3-45
SPACER PLATE
NUT
1BACN10TL3A6
NUT, SPACER
PLATE
1BACN10TL3A8
RIVET18BACR15DR3PAC2
RIVET, BLIND46BACR15DR4PAC3
RIVET, BLIND46BACR15DR4PAC5
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Group 1, 3:
KIT 015U1854-2
NOTES
Existing Part
NumberName
Figure
New Part Number
876
QTY
BOLT12BACS12HN3-10
BOLT22BACS12HN3-12
BOLT23BACS12HN3-20
Screw57BACS12HN3-25
SCREW12BACS12HN3-35
SCREW34BACS12HN3-38
STRAP1119BACS38K1
CONNECTOR
RING
22CR4H
WASHER1415NAS1149D0332J
SPACERS FOR
BOLTS
11NAS43DD3-40FC
SPACERS FOR
BOLTS
44NAS43DD3-64FC
MOUNTING
PLATE
22STBP19M14
Group 2:
KIT 015U1854-3
NOTES
Existing Part
NumberName
Figure
New Part Number
31
QTY
MOISTURE
SHROUD BRACK-
ET
2284U1135-76
MOISTURE
SHROUD BRACK-
ET
1284U1135-77
MOISTURE
SHROUD BRACK-
ET
1284U1135-78
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Group 2:
KIT 015U1854-3
NOTES
Existing Part
NumberName
Figure
New Part Number
31
QTY
MOISTURE
SHROUD BRACK-
ET
1284U1135-79
MOISTURE
SHROUD BRACK-
ET
2284U1135-80
MOISTURE
SHROUD BRACK-
ET
1284U1135-81
BOLT, PROTRUD-
ING HD
2214BACB30VT5HK4
BOLT, PROTRUD-
ING HD
55BACB30VT5HK5
BOLT28BACB30VT6K5
COLLAR,
PRELOAD
2125BACC30BH5
COLLAR10BACC30BH6
FILLER2BACF3F010G010NN
FILLER2BACF3F010J010NN
NUT, SPACER
PLATE, LIGHT
DUTY
2BACN10TL3-12
NUTPLATE1BACN10TL3-6
RIVET, UNIVER-
SAL HD
5BACR15BB4AD10C
RIVETS14BACR15BB4AD5C
RIVET, UNIVER-
SAL HD
3BACR15BB4AD7C
RIVET, BLIND12BACR15FR4E5R
WASHER12NAS1149DN432J
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Group 2:
KIT 015U1854-4
NOTES
Existing Part
NumberName
Figure
New Part Number
1096
QTY
TYGON TUBING22015U1854-100
FLANGED
SLEEVE
2005-131384
FITTING221401-007
DRAIN SPUD AS-
SY
1284T1213-11
DRAIN SPUD AS-
SY
1284T1213-13
DRAIN SPUD AS-
SY
2284T1213-9
CLAMP, LOOP1014BACC10DK16
NUT, SPACER
PLATE
11BACN10GH3A20
NUT-SPACER
PLATE
11BACN10GH3A4
NUTPLATE55BACN10KJ3CD
NUTPLATE66BACN10MK3-45
SPACER PLATE
NUT
1BACN10TL3A6
NUT, SPACER
PLATE
1BACN10TL3A8
RIVET101218BACR15DR3PAC2
RIVET, BLIND1818BACR15DR4PAC3
SCREW25BACS12GU3K12
SCREW, CAP34BACS12GU3K20
SCREW, CAP57BACS12GU3K9
SCREW, HEX
HEAD
34BACS12HN3-16
STRAP1119BACS38K1
WASHER1215NAS1149D0332J
SPACERS FOR
BOLTS
66NAS43DD3-40FC
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Group 2:
KIT 015U1854-4
NOTES
Existing Part
NumberName
Figure
New Part Number
1096
QTY
MOUNTING
PLATE
33STBP19M14
2. Parts and Materials Supplied by the Operator
NotesNameQTYPart Number /
Specification
(b)ADHESIVE1 QtBMS 5-92, Any
Type
(b)SEALANT1 QtBMS 5-95, Type I,
Class B
(a)(b)CHEMICAL CONVERSION COAT-
ING
1 OzALODINE 1200
(b)PRIMER1 OzBMS 10-11
(b)(d)FIBERGLASS SHEET2BMS 8-2, Type 13,
23, 26, or 35, Any
Class, Grade A
(b)FIBERGLASS CLOTH1 RollBMS 9-3, Type H,
H-2, or H-3, Class
7
PANEL STIFFENER3284U1135-82
(b)EPOXY RESIN1 QtBMS 8-201
(a) OPTIONAL MATERIALS: Alodine 600, Alodine 1200S, Alodine 1201 (Type 2 only), Alu-
mibond 1200, Turcoat Alumigold B or 4178-6, Chromicoat L25 or Iridite 14-2 (colored
film) (meets MIL-C-5541 Class 1A), Alodine 1600 or 1660.
(b) Refer to the Qualified Products List at the end of the Boeing Material Specification (BMS)
for supplier data.
(c) Use any alodine/supplier applicable for the purpose. PARKER-AMCHEM, 32100
STEPHENS HWY, MADISON HEIGHTS, MICHIGAN 48071 (V71410), OR HENKEL
CORP., HORSHAM BUSINESS CTR., 300 WELSH RD., BLDG. 2, SUITE 1, HORSHAM,
PENNSYLVANIA 1904.
(d) Qty 2 required, 6 inch x 6 inch square.
3. Parts Modified and Reidentified
The parts shown below are changed as shown in this service bulletin. The quantity (QTY) is the
number of parts changed on each airplane.
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NotesNew Part NumberNameQTYExisting Part
Number
(a)(b)FLOOR PANEL1284U1139-19
(284U1139-23 op-
tional)
(a)(b)FLOOR PANEL1284U1139-2
(284U1139-25 op-
tional)
(a) Make the change in accordance with in this service bulletin.
(b) There is no equivalent Boeing part number for the changed part. Identify on the part that
the change done in accordance with this service bulletin was made.
4. Parts Removed and Not Replaced
None.
D. Parts Necessary to Change Spares
None.
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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### Page 37

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. The work instructions are divided into work packages. Task Hours and Elapsed Hours
for each package are given in Paragraph 1.G., Manpower. You can do each work
package independently.
4. 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 are in 747-400 SRM Chapter 51
– Torque limits to tighten nuts and bolts are in 747-400 SRM Chapter 51
5. Use the approved fastener and process material substitutions in accordance with
747-400 SRM Chapter 51. Alternate fasteners are listed in 747-400 SRM Chapter
51.
6. 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.
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7. If the length of any fastener specified in this service bulletin does not meet the
installation standards in 747-400 SRM Chapter 51, then a fastener of the same
specification, or an approved substitute, with a length which meets the installation
standards in 747-400 SRM Chapter 51 may be used.
8. A General Visual Inspection is defined as: A visual examination of an interior or
exterior area, installation or assembly to detect obvious damage, failure or irregularity.
This level of inspection is made from within touching distance unless otherwise
specified. A mirror may be necessary to enhance visual access to all exposed surfaces
in the inspection area. This level of inspection is made under normally available
lighting conditions such as daylight, hangar lighting, flashlight or drop-light and may
require removal or opening of access panels or doors. Stands, ladders or platforms
may be required to gain proximity to the area being checked.
9. 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.
B. WORK INSTRUCTIONS
WORK PACKAGE 1: MAIN EQUIPMENT CENTER (MEC) DRIP SHIELD ALUMINUM GUTTER
REINFORCING BRACKET INSTALLATION
1. As required, remove the following electrical/electronic units from the top shelf of the MEC. Refer
to 747-400 AMM 20-11-22 as an accepted procedure.
a. Generator Control Units 1, 2, 3, and 4. Refer to 747-400 AMM 24-23-01 as an accepted
procedure.
b. Bus Control Units 1 and 2. Refer to 747-400 AMM 24-23-01 as an accepted procedure.
c. Auxiliary Generator control units 1 and 2. Refer to 747-400 AMM 24-23-05 as an accepted
procedure.
d. Hydraulic Quantity Indicator Unit. Refer to 747-400 AMM 29-33-02 as an accepted procedure.
e. Engine Vibration Monitor Units 1 & 2 and 3 & 4. Refer to 747-400 AMM 77-31-03 as an
accepted procedure.
f. Flight Management Computer. Refer to 747-400 AMM 34-61-01 as an accepted procedure.
g. Flight Control Computer. Refer to 747-400 AMM 22-11-01 as an accepted procedure.
h. Digital Interface Unit. Refer to 747-400 AMM 23-38-01 as an accepted procedure.
2. Install forward MEC drip shield aluminum gutter reinforcing brackets in accordance with Figure 1.
3. Remove cargo liner support inaccordance with Figure 18.
4. Group 1, 3:
Install aft MEC drip shield aluminum gutter reinforcing brackets in accordance with Figure 2.
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### Page 39

5. Group 2:
Install aft MEC drip shield aluminum gutter reinforcing brackets in accordance with Figure 3.
6. Install cargo liner support as given in Figure 19.
7. As required, install and test electrical/electronic rack components below. Refer to 747-400 AMM
20-11-22 as an accepted procedure.
a. Generator Control Units 1, 2, 3, and 4. Refer to 747-400 AMM 24-23-01 as an accepted
procedure.
b. Bus Control Units 1 and 2. Refer to 747-400 AMM 24-23-01 as an accepted procedure.
c. Auxiliary Generator control units 1 and 2. Refer to 747-400 AMM 24-23-05 as an accepted
procedure.
d. Hydraulic Quantity Indicator Unit. Refer to 747-400 AMM 29-33-02 as an accepted procedure.
e. Engine Vibration Monitor Units 1 & 2 and 3 & 4. Refer to 747-400 AMM 77-31-03 as an
accepted procedure.
f. Flight Management Computer. Refer to 747-400 AMM 34-61-01 as an accepted procedure.
g. Flight Control Computer. Refer to 747-400 AMM 22-11-01 as an accepted procedure.
h. Digital Interface Unit. Refer to 747-400 AMM 23-38-01 as an accepted procedure.
8. Put the airplane back to a serviceable condition.
WORK PACKAGE 2: MEC DRIP SHIELD DRAIN SYSTEM INSTALLATION
1. As required, remove the following electrical/electronic units from the top shelf of the main equipment
center. Refer to 747-400 AMM 20-11-22 as an accepted procedure.
a. Generator Control Units 1, 2, 3, and 4. Refer to 747-400 AMM 24-23-01 as an accepted
procedure.
b. Bus Control Units 1 and 2. Refer to 747-400 AMM 24-23-01 as an accepted procedure.
c. Auxiliary Generator control units 1 and 2. Refer to 747-400 AMM 24-23-05 as an accepted
procedure.
d. Hydraulic Quantity Indicator Unit. Refer to 747-400 AMM 29-33-02 as an accepted procedure.
e. Engine Vibration Monitor Units 1 & 2 and 3 & 4. Refer to 747-400 AMM 77-31-03 as an
accepted procedure.
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### Page 40

f. Flight Management Computer. Refer to 747-400 AMM 34-61-01 as an accepted procedure.
g. Flight Control Computer. Refer to 747-400 AMM 22-11-01 as an accepted procedure.
h. Digital Interface Unit. Refer to 747-400 AMM 23-38-01 as an accepted procedure.
2. Remove floor panels in accordance with Figure 4.
3. Modify floor panels in accordance with Figure 5.
4. Install flanged sleeves in accordance with Figure 6.
5. Group 2:
Install left side drain tubes in accordance with Figure 7.
6. Group 2:
Install right side drain tubes in accordance with Figure 8.
7. Group 1, 3:
Install left side drain tubes in accordance with Figure 9.
8. Group 1, 3:
Install right side drain tubes in accordance with Figure 10.
9. Install floor panels in accordance with Figure 11.
10. Seal the MEC drip shield in accordance with Figure 12.
11. As required, install and test electrical/electronic rack components below. Refer to 747-400 AMM
20-11-22 as an accepted procedure.
a. Generator Control Units 1, 2, 3, and 4. Refer to 747-400 AMM 24-23-01 as an accepted
procedure.
b. Bus Control Units 1 and 2. Refer to 747-400 AMM 24-23-01 as an accepted procedure.
c. Auxiliary Generator control units 1 and 2. Refer to 747-400 AMM 24-23-05 as an accepted
procedure.
d. Hydraulic Quantity Indicator Unit. Refer to 747-400 AMM 29-33-02 as an accepted procedure.
e. Engine Vibration Monitor Units 1 & 2 and 3 & 4. Refer to 747-400 AMM 77-31-03 as an
accepted procedure.
f. Flight Management Computer. Refer to 747-400 AMM 34-61-01 as an accepted procedure.
g. Flight Control Computer. Refer to 747-400 AMM 22-11-01 as an accepted procedure.
h. Digital Interface Unit. Refer to 747-400 AMM 23-38-01 as an accepted procedure.
12. Put the airplane back to a serviceable condition.
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### Page 41

WORK PACKAGE 3: MEC DRIP SHIELD FIBERGLASS REINFORCING OVERCOAT
1. As necessary remove the following items to gain access to the main deck floor panels between
STA 440 and STA 460 and LBL 55 and RBL 55.
a. Remove main deck galleys over the MEC. Refer to 747-400 AMM 25-31-00 as an accepted
procedure.
b. Remove main deck lavatories over the MEC. Refer to 747-400 AMM 25-40-01 as an accepted
procedure.
2. Remove main deck floor panels between STA 420 and STA 460 and LBL 55 and RBL 55. Refer
to 747-400 AMM 53-21-02 as an accepted procedure.
3. Group 3:
Remove existing MEC drip shield stiffeners in accordance with Figure 13.
4. Clean the MEC drip shield and do a general visual inspection for cracks and holes on the top
surface of the MEC drip shield in accordance with Figure 14.
a. If no cracks or holes are found, install MEC drip shield panel stiffeners in accordance with
Figure 16.
b. If any crack is found, repair the crack. Refer to 747-400 AMM 25-00-00 as an accepted
procedure.
c. If any hole is found, repair the hole in accordance with Figure 15.
5. Install MEC drip shield panel stiffeners in accordance with Figure 16.
6. Install fiberglass reinforcing overcoat to MEC drip shield in accordance with Figure 17.
7. Install main deck floor panels between STA 420 and STA 460 and LBL 55 and RBL 55. Refer to
747-400 AMM 53-21-02 as an accepted procedure.
8. As necessary install the following items between STA 440 and STA 460 and LBL 55 and RBL 55
on the main deck.
a. Install main deck galleys over the MEC. Refer to 747-400 AMM 25-31-00 as an accepted
procedure.
b. Install main deck lavatories over the MEC. Refer to 747-400 AMM 25-40-01 as an accepted
procedure.
9. Put the airplane back to a serviceable condition.
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### Page 42 (OCR)

BOEING SERVICE BULLETIN 747-25A3555
ALERT  ALERT
000
STA
460
STA
440
AND
00000  00000
1732344
FIGURE 1: FORWARD ALUMINUM GUTTER REINFORCING BRACKET INSTALLATION
(SHEET 1 OF 10)
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### Page 43 (OCR)

BOEING SERVICE BULLETIN 747-25A3555
ALERT  ALERT
SUPPORT
BRACKET
STA
440
SUPPORT
BRACKET
1732243
FIGURE 1: FORWARD ALUMINUM GUTTER REINFORCING BRACKET INSTALLATION
(SHEET 2 OF 10)
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### Page 44 (OCR)

BOEING SERVICE BULLETIN 747-25A3555
ALERT  ALERT
G  AND
1000
14 LOCATIONS  000
AND
AND
_ 1.75
→ 1.40
1732639
FIGURE 1: FORWARD ALUMINUM GUTTER REINFORCING BRACKET INSTALLATION
(SHEET 3 OF 10)
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### Page 45 (OCR)

BOEING SERVICE BULLETIN 747-25A3555
ALERT  ALERT
SHIM 11)13
10  2.15.  - 2.15
10
2.40
A-A  1732479
FIGURE 1: FORWARD ALUMINUM GUTTER REINFORCING BRACKET INSTALLATION
(SHEET 4 OF 10)
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### Page 46 (OCR)

BOEING SERVICE BULLETIN 747-25A3555
ALERT  ALERT
SUPPORT BRACKET
14 15 16
0.83
0.43
SUPPORT BRACKET
0.83
0.43
20)
K  1732376
FIGURE 1: FORWARD ALUMINUM GUTTER REINFORCING BRACKET INSTALLATION
(SHEET 5 OF 10)
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### Page 47

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 this figure.
MORE DATAQTYIDENTIFICATIONNAMETASKSTEP
Remove fasteners
inboard of BL 50
common to the for-
ward gutter and the
STA 440 floor beam
19-FASTENERSRemove1
Remove/keep any
existing equipment
from standoffs.
--EQUIPMENTRemove / Keep2
2-STAND OFFRemove
4-FASTENERSRemove
FIGURE 1: FORWARD ALUMINUM GUTTER REINFORCING BRACKET INSTALLATION
(SHEET 6 OF 10)
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BOEING SERVICE BULLETIN 747-25A3555
ALERTALERT

### Page 48

MORE DATAQTYIDENTIFICATIONNAMETASKSTEP
2-BRACKETRemove / Keep3
8-FASTENERSRemove / Keep
2-FASTENERSRemove4
4-FASTENERSRemove5
2284U1135-76MOISTURE SHROUD
BRACKET
Locate6
(a)-BMS 5-92, ANY TYPEADHESIVEApply7
2284U1135-76MOISTURE SHROUD
BRACKET
Install (New)8
Hole diameter:
0.161-0.164
14BACB30VT5HK4BOLT, PROTRUDING
HD
Install (New)9
14BACC30BH5COLLAR, PRELOADInstall (New)
(b)-BMS 5-95, TYPE I,
CLASS B
SEALANTApply
Drill hole thru STA
440 floor beam
2HOLE DIA: 0.161-0.164HOLEDrill10
Center shim over
hole location at LBL
2.15 and RBL 2.15
2BACF3F010G010NNFILLERLocate11
1284U1135-79MOISTURE SHROUD
BRACKET
Locate
(a)-BMS 5-92, ANY TYPEADHESIVEApply12
Center shim over
hole location at LBL
2.15 and RBL 2.15
2BACF3F010G010NNFILLERInstall (New)13
1284U1135-79MOISTURE SHROUD
BRACKET
Install (New)
Hole diameter:
0.161-0.164
3BACB30VT5HK5BOLT, PROTRUDING
HD
Install (New)
3BACC30BH5COLLAR, PRELOADInstall (New)
(b)-BMS 5-95, TYPE I,
CLASS B
SEALANTApply
If a short edge mar-
gin exists, use the
284U1135-108
bracket. (c)
1284U1135-78
(284U1135-108. option-
al)
MOISTURE SHROUD
BRACKET
Locate14
(a)-BMS 5-92, ANY TYPEADHESIVEApply15
FIGURE 1: FORWARD ALUMINUM GUTTER REINFORCING BRACKET INSTALLATION
(SHEET 7 OF 10)
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BOEING SERVICE BULLETIN 747-25A3555
ALERTALERT

### Page 49

MORE DATAQTYIDENTIFICATIONNAMETASKSTEP
If a short edge mar-
gin exists, use the
284U1135-108
bracket. (c)
1284U1135-78
(284U1135-108. option-
al)
MOISTURE SHROUD
BRACKET
Install (New)16
Install bolt in existing
fastener location.
Hole diameter:
0.161-0.164
1BACB30VT5HK5BOLT, PROTRUDING
HD
Install (New)17
1BACC30BH5COLLAR, PRELOADInstall (New)
(b)-BMS 5-95, TYPE I,
CLASS B
SEALANTApply
Install rivet in exist-
ing fastener location.
1BACR15FR4E5RRIVET, BLINDInstall (New)18
1NAS1149DN432JWASHERInstall (New)
(b)-BMS 5-95, TYPE I,
CLASS B
SEALANTApply
Install rivets thru
284U1135-77 mois-
ture shroud bracket,
MEC drip shield gut-
ter, and existing
support bracket in
existing fastener lo-
cation. If there is a
short edge margin,
it is acceptable for
only one fastener to
go thru the
284U1135-77 brack-
et.
2BACR15BB4AD5CRIVETSInstall (New)19
(b)-BMS 5-95, TYPE I,
CLASS B
SEALANTApply
If a short edge mar-
gin exists, use the
284U1135-107
bracket. (c)
1284U1135-77
(284U1135-107. option-
al)
MOISTURE SHROUD
BRACKET
Locate20
(a)-BMS 5-92, ANY TYPEADHESIVEApply21
If a short edge mar-
gin exists, use the
284U1135-107
bracket. (c)
1284U1135-77
(284U1135-107. option-
al)
MOISTURE SHROUD
BRACKET
Install (New)22
FIGURE 1: FORWARD ALUMINUM GUTTER REINFORCING BRACKET INSTALLATION
(SHEET 8 OF 10)
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ALERTALERT

### Page 50

MORE DATAQTYIDENTIFICATIONNAMETASKSTEP
Install bolt in existing
fastener location.
Hole diameter:
0.161-0.164
1BACB30VT5HK5BOLT, PROTRUDING
HD
Install (New)23
1BACC30BH5COLLAR, PRELOADInstall (New)
(b)-BMS 5-95, TYPE I,
CLASS B
SEALANTApply
Install rivet in exist-
ing fastener location.
1BACR15FR4E5RRIVET, BLINDInstall (New)24
1NAS1149DN432JWASHERInstall (New)
(b)-BMS 5-95, TYPE I,
CLASS B
SEALANTApply
Install rivets thru
284U1135-78 mois-
ture shroud bracket,
MEC drip shield gut-
ter, and existing
support bracket in
existing fastener lo-
cation.  If there is a
short edge margin,
it is acceptable for
only one fastener to
go thru the
284U1135-78 brack-
et.
2BACR15BB4AD5CRIVETSInstall (New)25
(b)-BMS 5-95, TYPE I,
CLASS B
SEALANTApply
2-BRACKETInstall (Kept)26
Install bolt in existing
fastener location.
Hole diameter:
0.187-0.190
8BACB30VT6K5BOLTInstall (New)27
8BACC30BH6COLLARInstall (New)
(b)-BMS 5-95, TYPE I,
CLASS B
SEALANTApply
FIGURE 1: FORWARD ALUMINUM GUTTER REINFORCING BRACKET INSTALLATION
(SHEET 9 OF 10)
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BOEING SERVICE BULLETIN 747-25A3555
ALERTALERT

### Page 51

MORE DATAQTYIDENTIFICATIONNAMETASKSTEP
2BACN10TL3-12NUT, SPACER PLATE,
LIGHT DUTY
Install (New)28
Install rivets in exist-
ing fastener loca-
tions.
4BACR15BB4AD10CRIVET, UNIVERSAL
HD
Install (New)
--EQUIPMENTInstall (Kept)
(b)-BMS 5-95, TYPE I,
CLASS B
SEALANTApply
(a) Apply fay surface seal between the forward gutter and the moisture shroud bracket. Ensure that entire
perimeter of moisture shroud bracket has sealant applied. Ensure that all small gaps around shims are
filled using BMS 5-92 as well. Refer to SOPM 20-50-12 as an accepted procedure.
(b) Seal the top side of fasteners with BMS 5-95. Refer to SOPM 20-50-12 as an accepted procedure.
(c) The 284U1135-107 and 284U1135-108 brackets can be fabricated using the information given in Appendix
A.
The parts shown in the table below are provided as extra parts for this figure.
MORE DATAQTYIDENTIFICATIONNAME
2BACC30BH6COLLAR
6BACC30BH5COLLAR, PRELOAD
1BACR15BB4AD10CRIVET, UNIVERSAL
HD
FIGURE 1: FORWARD ALUMINUM GUTTER REINFORCING BRACKET INSTALLATION
(SHEET 10 OF 10)
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BOEING SERVICE BULLETIN 747-25A3555
ALERTALERT

### Page 52 (OCR)

BOEING SERVICE BULLETIN 747-25A3555
ALERT  ALERT
This Figure applies only to: Group 1, 3.
STA
440
STA
460
AND C
00000  300000  1733461
FIGURE 2: AFT ALUMINUM GUTTER REINFORCING BRACKET INSTALLATION
(SHEET 1 OF 6)
Original Issue: November 04, 2009
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### Page 53 (OCR)

BOEING SERVICE BULLETIN 747-25A3555
ALERT  ALERT
FWD
1733784
FIGURE 2: AFT ALUMINUM GUTTER REINFORCING BRACKET INSTALLATION
(SHEET 2 OF 6)
Original Issue: November 04, 2009
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### Page 54 (OCR)

BOEING SERVICE BULLETIN 747-25A3555
ALERT  ALERT
21 LOCATIONS
AND
1.38  1.38
1733942
FIGURE 2: AFT ALUMINUM GUTTER REINFORCING BRACKET INSTALLATION
(SHEET 3 OF 6)
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### Page 55 (OCR)

BOEING SERVICE BULLETIN 747-25A3555
ALERT  ALERT
5) SHIM
EQUAL
EQUAL
1737592
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 this figure.
FIGURE 2: AFT ALUMINUM GUTTER REINFORCING BRACKET INSTALLATION
(SHEET 4 OF 6)
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### Page 56

MORE DATAQTYIDENTIFICATIONNAMETASKSTEP
21-FASTENERSRemove1
Remove/keep any
existing equipment
from standoffs.
--EQUIPMENTRemove / Keep2
4-STAND OFFRemove
8-FASTENERSRemove
2284U1135-80MOISTURE SHROUD
BRACKET
Install (New)3
(a)-BMS 5-92, ANY TYPEADHESIVEApply
Hole diameter:
0.161-0.164. (d)
18BACB30VT5HK4BOLT, PROTRUDING
HD
Install (New)4
18BACC30BH5COLLAR, PRELOADInstall (New)
(b)-BMS 5-95, TYPE I,
CLASS B
SEALANTApply
Center shim over
hole location at LBL
1.81 and RBL 1.81
2BACF3F010J010NNFILLERInstall (New)5
1284U1135-81MOISTURE SHROUD
BRACKET
Install (New)
(a)-BMS 5-92, ANY TYPEADHESIVEApply
Hole diameter:
0.161-0.164. (c)
3BACB30VT5HK5BOLT, PROTRUDING
HD
Install (New)6
3BACC30BH5COLLAR, PRELOADInstall (New)
(b)-BMS 5-95, TYPE I,
CLASS B
SEALANTApply
4BACN10TL3-6NUTPLATEInstall (New)7
(e)8BACR15BB4AD7CRIVET, UNIVERSAL
HD
Install (New)
--EQUIPMENTInstall (Kept)
(b)-BMS 5-95, TYPE I,
CLASS B
SEALANTApply
(a) Apply fay surface seal between the MEC drip shield and the moisture shroud bracket. Ensure that entire
perimeter of moisture shroud bracket has sealant applied. Ensure that all small gaps around shims are
filled using BMS 5-92 as well. Refer to SOPM 20-50-12 as an accepted procedure.
(b) Seal the top side of BACB30VT bolts and BACR15BB rivets with BMS 5-95. If blind fasteners are installed
as an option, install blind fasteners wet with BMS 5-95. Refer to SOPM 20-50-12 as an accepted procedure.
FIGURE 2: AFT ALUMINUM GUTTER REINFORCING BRACKET INSTALLATION
(SHEET 5 OF 6)
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BOEING SERVICE BULLETIN 747-25A3555
ALERTALERT

### Page 57

MORE DATAQTYIDENTIFICATIONNAMETASKSTEP
(c) NAS1398D5AB() or BACB30VL6TK350D blind fasteners are acceptable alternatives in this location to
allow installation without removing main deck floor panels.
(d) NAS1398D5AB() blind fasteners are acceptable alternatives in this location to allow installation without
removing main deck floor panels.
(e) NAS1398D4AB() blind fasteners are acceptable alternatives in this location to allow installation without
removing main deck floor panels.
The parts shown in the table below are provided as extra parts for this figure.
MORE DATAQTYIDENTIFICATIONNAME
2BACR15BB4AD7CRIVET, UNIVERSAL
HD
2BACB30VT5HK5BOLT, PROTRUDING
HD
4BACB30VT5HK4BOLT, PROTRUDING
HD
2BACB30VT6K5BOLT
FIGURE 2: AFT ALUMINUM GUTTER REINFORCING BRACKET INSTALLATION
(SHEET 6 OF 6)
BOEING PROPRIETARY -
Copyright © Unpublished Work - See page 1 for details.
Original Issue: November 04, 2009
747-25A3555Revision 1 July 27, 2011
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BOEING SERVICE BULLETIN 747-25A3555
ALERTALERT

### Page 58 (OCR)

BOEING SERVICE BULLETIN 747-25A3555
ALERT  ALERT
This Figure applies only to: Group 2.
STA
440
STA
460
AND
1732448
FIGURE 3: AFT ALUMINUM GUTTER REINFORCING BRACKET INSTALLATION
(SHEET 1 OF 6)
Original Issue: November 04, 2009
Revision 1 July 27, 2011  BOEING PROPRIETARY -  747-25A3555
Copyright © Unpublished Work - See page 1 for details.  58 of 141

### Page 59

FIGURE 3: AFT ALUMINUM GUTTER REINFORCING BRACKET INSTALLATION
(SHEET 2 OF 6)
BOEING PROPRIETARY -
Copyright © Unpublished Work - See page 1 for details.
Original Issue: November 04, 2009
747-25A3555Revision 1 July 27, 2011
59 of 141
BOEING SERVICE BULLETIN 747-25A3555
ALERTALERT

### Page 60 (OCR)

BOEING SERVICE BULLETIN 747-25A3555
ALERT  ALERT
9 LOCATIONS 4
AND  TEND
9 LOCATIONS 4
1.38
1.38
1733987
FIGURE 3: AFT ALUMINUM GUTTER REINFORCING BRACKET INSTALLATION
(SHEET 3 OF 6)
Original Issue: November 04, 2009
Revision 1 July 27, 2011  BOEING PROPRIETARY -  747-25A3555
Copyright © Unpublished Work - See page 1 for details.  60 of 141

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