# Boeing Alert Service Bulletin 737-55A1092: No revision named

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- Document: [Boeing Alert Service Bulletin 737-55A1092](https://openairdocs.org/service-documents/boeing/737-55a1092.md)
- Title as filed: U.S. DOT/FAA - SB-737-55A1092-00
- Pages: 43
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## Text

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### Page 1

Commercial 
Airplanes
737
Service Bulletin
ALERT
Number: 737-55A1092
Original Issue: August 07, 2015
ATA System: 5510
SUBJECT: STABILIZERS - Horizontal Stabilizer - Front Spar Chord Lugs - Inspections
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.
9E991ECCN:
BOEING PROPRIETARY, CONFIDENTIAL AND/OR TRADE SECRET
Copyright © 2015 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Unpublished Work.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: August 07, 2015
737-55A1092
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3.0

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Table of Contents
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1. PLANNING INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
A. Effectivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1. Airplanes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2. Spares Affected . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
B. Concurrent Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
C. Reason . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
D. Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
E. Compliance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
F. Approval . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
G. Manpower . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
H. Weight and Balance Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
I. Electrical Load Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
J. References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
1. Existing Data: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2. Data Supplied with this Service Bulletin: . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3. Installation Drawings Used in the Preparation of this Service Bulletin: . . . . . . . . . . . 20
K. Publications Affected . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
L. Interchangeability and Intermixability of Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
M. Software Accomplishment Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2. MATERIAL INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
A. Material - Price and Availability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
B. Industry Support Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
C. Parts Necessary for Each Airplane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
1. Kits/Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2. Parts and Materials Supplied by the Operator . . . . . . . . . . . . . . . . . . . . . . . . 21
3. Parts Modified and Reidentified . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4. Parts Removed and Not Replaced . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
D. Parts Necessary to Change Spares . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
E. Special Tooling - Price and Availability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
F. Special Tooling Necessary to do this Service Bulletin . . . . . . . . . . . . . . . . . . . . . . . 21
3. ACCOMPLISHMENT INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
A. GENERAL INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
B. WORK INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
FIGURE 1: LEFT SIDE HORIZONTAL STABILIZER - FRONT SPAR CHORD LUGS - DETAILED
INSPECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
FIGURE 2: RIGHT SIDE HORIZONTAL STABILIZER - FRONT SPAR CHORD LUGS - DETAILED
INSPECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
FIGURE 3: LEFT SIDE HORIZONTAL STABILIZER - FRONT SPAR CHORD LUGS - LUG BORE DETAILED
INSPECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
FIGURE 4: RIGHT SIDE HORIZONTAL STABILIZER - FRONT SPAR CHORD LUGS - LUG BORE
DETAILED INSPECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
APPENDIX A: LOGIC DIAGRAMS FOR COMPLIANCE TASKS AND COMPLIANCE TIMES . . . . . . . 41
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Commercial 
Airplanes
737
Service Bulletin
ALERT
SummaryNumber: 737-55A1092Original Issue: August 07, 2015
ATA System: 5510
SUBJECT: STABILIZERS - Horizontal Stabilizer - Front Spar Chord Lugs - Inspections
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
Between 2004 to 2011, a total of 12 intergranular cracks were reported by in-service airplanes on outboard
horizontal stabilizer front spar chord lugs (upper and lower chord). The cracks have been found along the axis
of the front spar chord and in the lug faces, lug bores, and lug spot-face surfaces. The stabilizer front spar chords
are made from 7075-T6511 extrusion. This material is susceptible to stress corrosion in a corrosive environment
where residual machining stresses are present and where the material finish and sealant have degraded. A
single joint failure will significantly reduce the remaining fatigue life in the rear spar. A dual failure of the upper
and lower front spar joints could cause stabilizer instability, affect controllability of the airplane, and could
adversely affect the structural integrity of the airplane.
Boeing Fleet Team Digest (FTD) 737 FTD 55-06002 is related to this service bulletin.
Boeing Service Related Problem (SRP) 737-55-0036 is related to this service bulletin.
ACTION
Do a Detailed Inspection and Ultrasonic Inspection on the horizontal stabilizer front spar chord lugs and a Detailed
Inspection on the horizontal stabilizer front spar chord lug bores.
1. Repeat Detailed Inspection for corrosion and Ultrasonic Inspection for any crack.
2. Contact The Boeing Company for repair instructions and do the repair.
EFFECTIVITY
All 737-300/-400/-500 Airplane(s). Refer to Paragraph 1.A.1., Airplanes, for the list of affected airplane(s).
Export Controlled ECCN: 9E991 - BOEING
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COMPLIANCE
The Federal Aviation Administration (FAA) will possibly release an Airworthiness Directive related to this service
bulletin. The Airworthiness Directive will make the compliance tasks and times given in this service bulletin
mandatory.
Refer to Paragraph 1.E., Compliance.
INDUSTRY SUPPORT INFORMATION
Boeing warranty remedies are not available for the inspections given in this service bulletin.
MANPOWER
Refer to Paragraph 1.G., Manpower.
MATERIAL INFORMATION
None.
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BOEING SERVICE BULLETIN 737-55A1092
ALERT  ALERT
INSPECTION FOR CRACKS AND CORROSION
ON HORIZONTAL STABILIZER FRONT SPAR
CHORD LUGS
2420153
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ALERTALERT
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Commercial 
Airplanes
737
Service Bulletin
ALERT
Number: 737-55A1092
Original Issue: August 07, 2015
ATA System: 5510
SUBJECT: STABILIZERS - Horizontal Stabilizer - Front Spar Chord Lugs - Inspections
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
DESCRIPTIONCONFIGURATIONGROUP
737-300/400/500-1
Airplane Models:
737-300, 737-400, 737-500
GroupVariable Number
1PJ301 - PJ302
1PJ551 - PJ561
1PJ601 - PJ615
1PJ811
1PJ816 - PJ817
1PM381 - PM399
1PM401 - PM417
1PM541 - PM564
1PP001 - PP054
1PP101 - PP169
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GroupVariable Number
1PP181 - PP199
1PP201 - PP205
1PP221
1PP231 - PP243
1PP281 - PP286
1PP301 - PP305
1PP351 - PP353
1PP376 - PP384
1PP391 - PP393
1PP401 - PP440
1PP471 - PP475
1PP501 - PP522
1PP631 - PP634
1PP651 - PP652
1PP671 - PP699
1PP701 - PP733
1PP771 - PP779
1PP801 - PP808
1PP821 - PP827
1PP831 - PP848
1PP851 - PP852
1PP861 - PP877
1PP891 - PP899
1PP901 - PP936
1PP946 - PP948
1PP951 - PP952
1PP961 - PP967
1PP981 - PP991
1PP993
1PQ001 - PQ016
1PQ026 - PQ041
1PQ051 - PQ092
1PQ101 - PQ199
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GroupVariable Number
1PQ201 - PQ202
1PQ221 - PQ237
1PQ241 - PQ243
1PQ251 - PQ267
1PQ281 - PQ299
1PQ301 - PQ307
1PQ331 - PQ332
1PQ341 - PQ348
1PQ361 - PQ373
1PQ391 - PQ395
1PQ401 - PQ418
1PQ421
1PQ431 - PQ438
1PQ447 - PQ448
1PQ451
1PQ454
1PQ471 - PQ475
1PQ479 - PQ481
1PQ486 - PQ487
1PQ491 - PQ493
1PQ771 - PQ772
1PQ791 - PQ793
1PQ801 - PQ805
1PQ931 - PQ935
1PQ951
1PQ971 - PQ997
1PR001 - PR017
1PR021 - PR034
1PR041 - PR045
1PR061 - PR072
1PR077 - PR082
1PR091 - PR092
1PR096
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GroupVariable Number
1PR101
1PR121 - PR122
1PR131 - PR132
1PR141 - PR143
1PR161 - PR172
1PR181
1PS601 - PS631
1PS636 - PS638
1PS641 - PS644
1PS651 - PS657
1PS666 - PS669
1PS691 - PS692
1PS701 - PS706
1PS751 - PS799
1PS811
1PS836 - PS837
1PS841 - PS846
1PS851 - PS852
1PS856
1PS861 - PS863
1PS866 - PS868
1PS871 - PS874
1PS896 - PS897
1PS901 - PS941
1PS956 - PS957
1PS961 - PS963
1PS971 - PS978
1PT001 - PT015
1PT021 - PT031
1PT041 - PT064
1PT101 - PT105
1PT121 - PT138
1PT146 - PT148
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GroupVariable Number
1PT161 - PT170
1PT181 - PT188
1PT211 - PT220
1PT295
1PT301 - PT309
1PT331 - PT360
1PT381 - PT399
1PT401 - PT438
1PT501 - PT517
1PT561 - PT565
1PT581 - PT586
1PT611 - PT621
1PT641 - PT644
1PT651 - PT656
1PT671 - PT672
1PT681 - PT685
1PT701 - PT703
1PT716 - PT717
1PT721 - PT725
1PT801 - PT834
1PT851 - PT854
1PT871 - PT886
1PT901 - PT930
1PT971 - PT973
1PT981 - PT985
1PT996
1PU001 - PU025
1PU301
1PU311 - PU313
1PV001 - PV055
1PV201 - PV209
1PV226 - PV229
1PV231 - PV237
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GroupVariable Number
1PV271 - PV272
1PV281 - PV287
1PV296
1PV301 - PV302
1PV351
1PV356 - PV357
1PW001 - PW054
1PW061 - PW068
1PW072
1PW086 - PW088
1PW091 - PW094
1PW101 - PW102
1PW106
1PW111 - PW120
1PW156 - PW157
1PW161 - PW171
1PW201 - PW252
1PW261 - PW268
1PW271 - PW276
1PW278
1PW281 - PW293
1PW296
1PW301 - PW327
1PW401 - PW408
1PW411 - PW418
1PW421 - PW424
1PW431 - PW435
1PW441 - PW450
1PW461 - PW467
1PW501 - PW504
1PW511 - PW522
1PW524 - PW550
1PW556 - PW557
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GroupVariable Number
1PW561 - PW564
1PW571 - PW576
1PW591 - PW596
1PW611 - PW622
1PW631 - PW637
1PW661 - PW662
1PW681 - PW683
1PW701 - PW702
1PW711 - PW717
1PW741 - PW742
1PW761
1PW771
1PW831
1PW851 - PW856
2. Spares Affected
None.
B. Concurrent Requirements
None.
C. Reason
Between 2004 to 2011, a total of 12 intergranular cracks were reported by in-service airplanes on
outboard horizontal stabilizer front spar chord lugs (upper and lower chord). The cracks have been
found along the axis of the front spar chord and in the lug faces, lug bores, and lug spot-face surfaces.
The stabilizer front spar chords are made from 7075-T6511 extrusion. This material is susceptible to
stress corrosion in a corrosive environment where residual machining stresses are present and where
the material finish and sealant have degraded. A single joint failure will significantly reduce the remaining
fatigue life in the rear spar. A dual failure of the upper and lower front spar joints could cause stabilizer
instability, affect controllability of the airplane, and could adversely affect the structural integrity of the
airplane.
Boeing Fleet Team Digest (FTD) 737 FTD 55-06002 is related to this service bulletin.
Boeing Service Related Problem (SRP) 737-55-0036 is related to this service bulletin.
D. Description
Do a Detailed Inspection and Ultrasonic Inspection on the horizontal stabilizer front spar chord lugs
and a Detailed Inspection on the horizontal stabilizer front spar chord lug bores.
Export Controlled ECCN: 9E991 - BOEING
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1. Repeat Detailed Inspection for corrosion and Ultrasonic Inspection for any crack.
2. Contact The Boeing Company for repair instructions and do the repair.
The work in this service bulletin is done in the maintenance zone(s) given below.
Affected Maintenance Zones
ZoneModel
709, 710737-300, 737-400, 737-500
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.
A logic diagram showing compliance tasks and compliance times is included as an aid in APPENDIX
A.
Do the required actions in accordance with Paragraph 3. Accomplishment Instructions.
Table 1: INSPECT FOR CORROSION AND ANY CRACK ON THE HORIZONTAL STABILIZER FRONT
SPAR CHORD LUGS
Repeat Interval
(Not to Exceed)
Compliance TimeActionCondition
-Within 27 months
after the original is-
sue date of this
service bulletin.
Do PART 1 - HORIZON-
TAL STABILIZER -
FRONT SPAR CHORD
LUGS DETAILED AND
ULTRASONIC INSPEC-
TIONS for corrosion and
any crack.
All Airplanes
24 months.-Repeat PART 1 - HORI-
ZONTAL STABILIZER -
FRONT SPAR CHORD
LUGS DETAILED AND
ULTRASONIC INSPEC-
TIONS for corrosion and
any crack.
CONDITION 1: NO COR-
ROSION AND NO CRACK
FOUND
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Table 1: INSPECT FOR CORROSION AND ANY CRACK ON THE HORIZONTAL STABILIZER FRONT
SPAR CHORD LUGS
Repeat Interval
(Not to Exceed)
Compliance TimeActionCondition
-Before further
flight.
ACTION 1:
Contact The Boeing
Company for repair in-
structions and do the re-
pair.
CONDITION 2: ANY COR-
ROSION OR ANY CRACK
FOUND
24 months-ACTION 2:
Repeat PART 1 - HORI-
ZONTAL STABILIZER -
FRONT SPAR CHORD
LUGS DETAILED AND
ULTRASONIC INSPEC-
TIONS for corrosion and
any crack at the unre-
paired lugs.
Table 2: INSPECT FOR CORROSION ON THE HORIZONTAL STABILIZER FRONT SPAR CHORD
LUG BORES
Repeat Interval
(Not to Exceed)
Compliance TimeActionCondition
-Within 27 months
after the original is-
sue date of this
service bulletin.
Do PART 2 - HORIZON-
TAL STABILIZER -
FRONT SPAR CHORD
LUG BORES DETAILED
INSPECTION for corro-
sion.
All Airplanes
96 months.-Repeat PART 2 - HORI-
ZONTAL STABILIZER -
FRONT SPAR CHORD
LUG BORES DETAILED
INSPECTION for corro-
sion.
CONDITION 3: NO COR-
ROSION FOUND
-Before further
flight.
ACTION 1:
Contact The Boeing
Company for repair in-
structions and do the re-
pair.
CONDITION 4: ANY COR-
ROSION FOUND
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Table 2: INSPECT FOR CORROSION ON THE HORIZONTAL STABILIZER FRONT SPAR CHORD
LUG BORES
Repeat Interval
(Not to Exceed)
Compliance TimeActionCondition
96 months.-ACTION 2:
Repeat PART 2 - HORI-
ZONTAL STABILIZER -
FRONT SPAR CHORD
LUG BORES DETAILED
INSPECTION for corro-
sion at the unrepaired
lugs.
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 tables below show an estimate of the task hours necessary to do these inspections 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.
HORIZONTAL STABILIZER - FRONT SPAR CHORD LUGS DETAILED AND ULTRASONIC
INSPECTIONS WITH THE LUG BOLTS INSTALLED
Elapsed HoursTask HoursNumber of PersonsTask
0.50.51Open Access
2.02.01FIGURE 1
2.02.01FIGURE 2
0.50.51Close Access
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### Page 19

HORIZONTAL STABILIZER - FRONT SPAR CHORD LUGS DETAILED AND ULTRASONIC
INSPECTIONS WITH THE LUG BOLTS INSTALLED
Elapsed HoursTask HoursNumber of PersonsTask
55TOTAL FOR EACH AIRPLANE
HORIZONTAL STABILIZER - FRONT SPAR CHORD LUGS DETAILED INSPECTION WITH
THE LUG BOLTS REMOVED
Elapsed HoursTask HoursNumber of PersonsTask
0.50.51Open Access
4.04.01FIGURE 3
4.04.01FIGURE 4
0.50.5Close Access
9.09.0TOTAL FOR EACH AIRPLANE
H. Weight and Balance Changes
None.
I. Electrical Load Data
Not changed.
J. References
1. Existing Data:
a. Boeing Service Letter 737-SL-51-042
b. Boeing Service Related Problem (SRP) 737-55-0036
c. Standard Overhaul Practices Manual (SOPM) 20-41-05, 20-50-01
d. 737 Fleet Team Digest (FTD) 55-06002
e. 737 Non-Destructive Testing (NDT) Manual Part 4, 55-10-21
f. 737-300/400/500 Aircraft Maintenance Manual (AMM) 12-31-81, 27-41-11
2. Data Supplied with this Service Bulletin:
None.
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### Page 20

3. Installation Drawings Used in the Preparation of this Service Bulletin:
TitleDrawing Number
GAP COVER AND SEAL INSTL-HORIZONTAL STABILIZER TO
BODY
65-53746
The table above lists applicable drawings used to prepare this service bulletin. The drawings are
not necessary to make the specified changes, and are not supplied with this service bulletin. The
drawings may not be applicable to all airplane configurations or operators.
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 affects FCS. DTI requirements for the structure affected
are contained in Paragraph 1.E., Compliance of this service bulletin.
L. Interchangeability and Intermixability of Parts
Accomplishment of this service bulletin does not affect interchangeability or intermixability of parts.
M. Software Accomplishment Summary
Not affected.
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### Page 21

2.    MATERIAL INFORMATION
A. Material - Price and Availability
None.
B. Industry Support Information
Boeing warranty remedies are not available for the inspections given in this service bulletin.
C. Parts Necessary for Each Airplane
1. Kits/Parts
None.
2. Parts and Materials Supplied by the Operator
No special parts or materials are necessary to do the change in this service bulletin. But, parts
and materials in the manuals given in Paragraph 1.J., References, can be necessary. Examine
operator part and material supply to make sure all necessary parts and materials are available.
3. Parts Modified and Reidentified
None.
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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BLANK PAGE

### Page 23

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 and fasteners are in Structural Repair
Manual (SRM) Chapter 51
– Torque Values:
— Values for structural fasteners are given in 737 Structural Repair Manual,
Chapter 51.
— Values for airframe maintenance tasks are included in Chapter 20 of 737
Aircraft 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 737
Aircraft Maintenance Manual (AMM).
— Non-standard torque values for maintenance tasks are included in the
applicable installation step.
5. Use the approved fastener, process and material substitutions in accordance with
SRM Chapter 51.
6. 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.
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### Page 24

7. A Detailed Inspection is defined as: An intensive examination of a specific item,
installation, or assembly to detect damage, failure, or irregularity. Available lighting
is normally supplemented with a direct source of good lighting at an intensity deemed
appropriate. Inspection aids such as mirrors, magnifying lenses, etc. may be
necessary. Surface cleaning and elaborate procedures may be required.
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. Boeing Service Letter 737-SL-51-042, Damage Reporting and Repair Plan/Design
Guidelines, is an acceptable procedure to request information from Boeing for
additional structural repair instructions. The Service Letter describes what information
must be provided to Boeing before a structural repair can be provided.
10. Refer to APPENDIX A for logic diagram(s). Logic diagrams are provided as an aid
only. Information contained in Paragraph 1.E., Compliance is the primary source for
compliance times. Information in Paragraph 3.B., Work Instructions is the primary
source for tasks required for compliance.
11. The instructions in Paragraph 3.B., Work Instructions and the figures can include
operation of tools or test equipment. Boeing Engineering Tool Drawings, the Illustrated
Tool and Equipment Manual, and the Special Tool and Ground Handling Drawing
Index contain data on versions of the tools or test equipment that you can use. It is
permitted to use replaced tools. It is not permitted to use superseded tools.
12. 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.
13. 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.
14. This service bulletin includes functional test procedures for the systems changed by
this service bulletin. More functional tests can possibly be necessary in accordance
with standard maintenance practices because of interruption to other airplane systems.
15. Some Boeing parts are supplied in a temporary configuration. Those parts are
identified with a 'U', 'W', or 'Y' in place of the '-' (dash) in the part number. It is
permitted to install parts identified with a 'U', 'W', or 'Y' as an alternative to the '-'
(dash) part number. Boeing Drawing 005W0900 contains more data.
16. If shading is used, shaded areas in Figures are to separate the non-critical and
non-authoritative information from the critical and authoritative information.
17. Use of colors in Figures is based on guidance from the ATA e-Business Program
(ATA) iSpec 2200.
18. The compliance times for the actions in Paragraph 3.B., WORK INSTRUCTIONS
are in Paragraph 1.E., Compliance.
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19. Some steps in the Work Instructions are labeled as Required for Compliance (RC).
If this service bulletin is mandated by an Airworthiness Directive (AD), then the steps
labeled as RC, including sub-steps under an RC step and any figures identified in
an RC step, must be done to comply with the AD. An Alternative Method of
Compliance (AMOC) is required for any deviations to RC steps, including sub-steps
and identified figures Steps not labeled as RC may be deviated from using accepted
methods in accordance with the operator's maintenance or inspection program without
obtaining approval of an AMOC. This is provided that the RC steps, including
sub-steps and identified figures, can still be done as specified, and the airplane can
be put back in an airworthy condition.
20. The front spar lugs remain subject to the requirements of the Corrosion Prevention
and Control Program (CPCP). If Level 2 or 3 corrosion, as defined by the program,
is occurring, then the inspections and maintenance of these lugs must be adjusted
to the necessary degree that preempts further Level 2 or 3 corrosion development.
Fillet seal around the bushing flanges and between the bushing tails in the bore is
a primary barrier to moisture ingress and corrosion development. Damaged sealant
is an indication that corrosion is more likely to develop. It may be an indication that
the bushing has been rotating in the bore due to poor interference. Therefore, if
sealant is damaged, then we recommend, as a minimum, that the periphery of the
sealant be treated with BMS 3-38, and reapply at each follow on inspection until the
bushing is replaced and sealant is restored. In consideration of the CPCP obligations,
it is in the operator's best interest to avoid deferring sealant restoration indefinitely.
B. WORK INSTRUCTIONS
PART 1 - HORIZONTAL STABILIZER - FRONT SPAR CHORD LUGS DETAILED AND ULTRASONIC
INSPECTIONS
1. Remove and keep access panels 9119, 9120, 9219, and 9220. Refer to 737-300/400/500 AMM
12-31-81.
2. Remove and keep bracket assembly (rib) located immediately aft of the front spar chord lug
65-53746-153 or 65-53746-625 and 65-53746-154 or 65-53746-626.
3. RC - Do a Detailed Inspection with the lug bolts installed for corrosion in accordance with FIGURE
1 and FIGURE 2.
RC - Do an Ultrasonic Inspection for any crack in accordance with 737 NDT Manual Part 4,
55-10-21.
a. CONDITION 1: NO CORROSION AND NO CRACK FOUND
(1) Repeat PART 1 - HORIZONTAL STABILIZER - FRONT SPAR CHORD LUGS DETAILED
AND ULTRASONIC INSPECTIONS for corrosion and any crack.
b. CONDITION 2: ANY CORROSION OR ANY CRACK FOUND
(1) ACTION 1: Contact The Boeing Company for repair instructions and do the repair.
(2) ACTION 2: Repeat PART 1 - HORIZONTAL STABILIZER - FRONT SPAR CHORD LUGS
DETAILED AND ULTRASONIC INSPECTIONS for corrosion and any crack at the
unrepaired lugs.
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### Page 26

4. Apply BMS 3-23 Organic Corrosion Inhibiting Compound to the inspection areas described in
FIGURE 1 and FIGURE 2. Refer to SOPM 20-41-05 as an accepted procedure.
5. Install kept bracket assembly (rib) 65-53746-153 or 65-53746-625 and 65-53746-154 or
65-53746-626.
6. Install kept access panels 9119, 9120, 9219, and 9220. Refer to 737-300/400/500 AMM 12-31-81.
7. Return airplane to a serviceable condition.
PART 2 - HORIZONTAL STABILIZER - FRONT SPAR CHORD LUG BORES DETAILED INSPECTION
1. Remove and keep access panels 9119, 9120, 9219, and 9220. Refer to 737-300/400/500 AMM
12-31-81.
2. Remove and keep bracket assembly (rib) located immediately aft of the front spar chord lug
65-53746-153 or 65-53746-625 and 65-53746-154 or 65-53746-626.
3. RC - Do a Detailed Inspection with the lug bolts removed for corrosion in accordance with FIGURE
3 and FIGURE 4.
a. CONDITION 3: NO CORROSION FOUND
(1) Repeat PART 2 - HORIZONTAL STABILIZER - FRONT SPAR CHORD LUG BORES
DETAILED INSPECTION for corrosion.
b. CONDITION 4: ANY CORROSION FOUND
(1) ACTION 1: Contact The Boeing Company for repair instructions and do the repair.
(2) ACTION 2: Repeat PART 2 - HORIZONTAL STABILIZER - FRONT SPAR CHORD LUG
BORES DETAILED INSPECTION for corrosion at the unrepaired lugs.
4. Install kept bracket assembly (rib) 65-53746-153 or 65-53746-625 and 65-53746-154 or
65-53746-626.
5. Install kept access panels 9119, 9120, 9219, and 9220. Refer to 737-300/400/500 AMM 12-31-81.
6. Put the airplane back to a serviceable condition.
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### Page 27 (OCR)

BOEING SERVICE BULLETIN 737-55A1092
ALERT  ALERT
2420142
FIGURE 1: LEFT SIDE HORIZONTAL STABILIZER - FRONT SPAR CHORD LUGS - DETAILED INSPECTION
(SHEET 1 OF 3)
Original Issue: August 07, 2015
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### Page 28 (OCR)

BOEING SERVICE BULLETIN 737-55A1092
ALERT  ALERT
A
FILLET SEAL  Q
LUG BUSHING
INSPECTION AREA  CLOSURE RIB
CENTER SECTION
CLEVIS LUGS AND
ATTACHMENTS
REMOVED FOR
CLARITY
FILLET SEAL
LUG BUSHING
A-A  2420143
FIGURE 1: LEFT SIDE HORIZONTAL STABILIZER - FRONT SPAR CHORD LUGS - DETAILED INSPECTION
(SHEET 2 OF 3)
Original Issue: August 07, 2015
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### Page 29

The step numbers shown below agree with the numbers shown in the circle symbols in the figure.
MORE DATAIDENTIFICATIONNAMETASKSTEP
Do a Detailed Inspection for corro-
sion. (a)
--Inspect1
(a) Inspect forward and aft lug faces. Surface cleaning, direct lighting, mirrors, magnifying lenses, and
probing tools will be necessary. Inspect for corrosion from the inboard edge of the closure rib, all
the way to the inboard edge of the lug. In the gap between outboard lug and center section clevis,
inspect completely around the circumference of the bushing flanges, from the flange edge to the
edge of the lug.
FIGURE 1: LEFT SIDE HORIZONTAL STABILIZER - FRONT SPAR CHORD LUGS - DETAILED INSPECTION
(SHEET 3 OF 3)
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### Page 30 (OCR)

BOEING SERVICE BULLETIN 737-55A1092
ALERT  ALERT
2420144
FIGURE 2: RIGHT SIDE HORIZONTAL STABILIZER - FRONT SPAR CHORD LUGS - DETAILED INSPECTION
(SHEET 1 OF 3)
Original Issue: August 07, 2015
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### Page 31 (OCR)

BOEING SERVICE BULLETIN 737-55A1092
ALERT  ALERT
FILLET SEAL
LUG BUSHING
INSPECTION AREA
> CLOSURE RIB
CENTER SECTION
CLEVIS LUGS AND
ATTACHMENTS
REMOVED FOR
CLARITY
FILLET SEAL
LUG BUSHING
A-A  2420146
FIGURE 2: RIGHT SIDE HORIZONTAL STABILIZER - FRONT SPAR CHORD LUGS - DETAILED INSPECTION
(SHEET 2 OF 3)
Original Issue: August 07, 2015
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### Page 32

The step numbers shown below agree with the numbers shown in the circle symbols in the figure.
MORE DATAIDENTIFICATIONNAMETASKSTEP
Do a Detailed Inspection for corro-
sion. (a)
--Inspect1
(a) Inspect forward and aft lug faces. Surface cleaning, direct lighting, mirrors, magnifying lenses, and
probing tools will be necessary. Inspect for corrosion from the inboard edge of the closure rib, all
the way to the inboard edge of the lug. In the gap between outboard lug and center section clevis,
inspect completely around the circumference of the bushing flanges, from the flange edge to the
edge of the lug.
FIGURE 2: RIGHT SIDE HORIZONTAL STABILIZER - FRONT SPAR CHORD LUGS - DETAILED INSPECTION
(SHEET 3 OF 3)
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### Page 33 (OCR)

BOEING SERVICE BULLETIN 737-55A1092
ALERT  ALERT
2420147
FIGURE 3: LEFT SIDE HORIZONTAL STABILIZER - FRONT SPAR CHORD LUGS - LUG BORE DETAILED
INSPECTION
(SHEET 1 OF 4)
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### Page 34 (OCR)

BOEING SERVICE BULLETIN 737-55A1092
ALERT  ALERT
A-A  2420148
FIGURE 3: LEFT SIDE HORIZONTAL STABILIZER - FRONT SPAR CHORD LUGS - LUG BORE DETAILED
INSPECTION
(SHEET 2 OF 4)
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### Page 35 (OCR)

BOEING SERVICE BULLETIN 737-55A1092
ALERT  ALERT
BORE
2) 5) CORROSION
(TYPICAL)
HORIZONTAL STABILIZER
CENTER SECTION CLEVIS
OMITTED FOR CLARITY
B-B
2420149
FIGURE 3: LEFT SIDE HORIZONTAL STABILIZER - FRONT SPAR CHORD LUGS - LUG BORE DETAILED
INSPECTION
(SHEET 3 OF 4)
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### Page 36

The step numbers shown below agree with the numbers shown in the circle symbols in the figure.
MORE DATAIDENTIFICATIONNAMETASKSTEP
CAUTION: ONLY REMOVE ONE BOLT AT A TIME FOR EACH STABILIZER. IF YOU REMOVE MORE
THAN ONE BOLT AT A TIME FOR EACH STABILIZER, YOU MAY CAUSE DAMAGE TO THE HORI-
ZONTAL STABILIZER STRUCTURE OR SYSTEMS.
Refer to 737-300/400/500 AMM 27-
41-11 as an accepted procedure for
preparation and bolt removal instruc-
tions.
-Upper Lug BoltRemove1
Do a Detailed Inspection for corro-
sion.
-BoreInspect2
Refer to 737-300/400/500 AMM 27-
41-11 as an accepted procedure for
bolt installation instructions, except
install the bolt with BMS 3-38, under
bolt head, all over the bolt shank,
and all over the bushing ID. Make
sure the bolt threads are free from
BMS 3-38.
-Upper Lug BoltInstall3
CAUTION: ONLY REMOVE ONE BOLT AT A TIME FOR EACH STABILIZER. IF YOU REMOVE MORE
THAN ONE BOLT AT A TIME FOR EACH STABILIZER, YOU MAY CAUSE DAMAGE TO THE HORI-
ZONTAL STABILIZER STRUCTURE OR SYSTEMS.
Refer to 737-300/400/500 AMM 27-
41-11 as an accepted procedure for
preparation and bolt removal instruc-
tions.
-Lower Lug BoltRemove4
Do a Detailed Inspection for corro-
sion.
-BoreInspect5
Refer to 737-300/400/500 AMM 27-
41-11 as an accepted procedure for
bolt installation instructions, except
install the bolt with BMS 3-38, under
bolt head, all over the bolt shank,
and all over the bushing ID. Make
sure the bolt threads are free from
BMS 3-38.
-Lower Lug BoltInstall6
FIGURE 3: LEFT SIDE HORIZONTAL STABILIZER - FRONT SPAR CHORD LUGS - LUG BORE DETAILED
INSPECTION
(SHEET 4 OF 4)
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### Page 37 (OCR)

BOEING SERVICE BULLETIN 737-55A1092
ALERT  ALERT
2420150
FIGURE 4: RIGHT SIDE HORIZONTAL STABILIZER - FRONT SPAR CHORD LUGS - LUG BORE DETAILED
INSPECTION
(SHEET 1 OF 4)
Original Issue: August 07, 2015
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### Page 38 (OCR)

BOEING SERVICE BULLETIN 737-55A1092
ALERT  ALERT
A-A  2420151
FIGURE 4: RIGHT SIDE HORIZONTAL STABILIZER - FRONT SPAR CHORD LUGS - LUG BORE DETAILED
INSPECTION
(SHEET 2 OF 4)
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### Page 39 (OCR)

BOEING SERVICE BULLETIN 737-55A1092
ALERT  ALERT
BORE
CORROSION 2) 5)
(TYPICAL)
HORIZONTAL STABILIZER
CENTER SECTION CLEVIS
OMITTED FOR CLARITY
B-B
2420152
FIGURE 4: RIGHT SIDE HORIZONTAL STABILIZER - FRONT SPAR CHORD LUGS - LUG BORE DETAILED
INSPECTION
(SHEET 3 OF 4)
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### Page 40

The step numbers shown below agree with the numbers shown in the circle symbols in the figure.
MORE DATAIDENTIFICATIONNAMETASKSTEP
CAUTION: ONLY REMOVE ONE BOLT AT A TIME FOR EACH STABILIZER. IF YOU REMOVE MORE
THAN ONE BOLT AT A TIME FOR EACH STABILIZER, YOU MAY CAUSE DAMAGE TO THE HORI-
ZONTAL STABILIZER STRUCTURE OR SYSTEMS.
Refer to 737-300/400/500 AMM 27-
41-11 as an accepted procedure for
preparation and bolt removal instruc-
tions.
-Upper Lug BoltRemove1
Do a Detailed Inspection for corro-
sion.
-BoreInspect2
Refer to 737-300/400/500 AMM 27-
41-11 as an accepted procedure for
bolt installation instructions, except
install the bolt with BMS 3-38, under
bolt head, all over the bolt shank,
and all over the bushing ID. Make
sure the bolt threads are free from
BMS 3-38.
-Upper Lug BoltInstall3
CAUTION: ONLY REMOVE ONE BOLT AT A TIME FOR EACH STABILIZER. IF YOU REMOVE MORE
THAN ONE BOLT AT A TIME FOR EACH STABILIZER, YOU MAY CAUSE DAMAGE TO THE HORI-
ZONTAL STABILIZER STRUCTURE OR SYSTEMS.
Refer to 737-300/400/500 AMM 27-
41-11 as an accepted procedure for
preparation and bolt removal instruc-
tions.
-Lower Lug BoltRemove4
Do a Detailed Inspection for corro-
sion.
-BoreInspect5
Refer to 737-300/400/500 AMM 27-
41-11 as an accepted procedure for
bolt installation instructions, except
install the bolt with BMS 3-38, under
bolt head, all over the bolt shank,
and all over the bushing ID. Make
sure the bolt threads are free from
BMS 3-38.
-Lower Lug BoltInstall6
FIGURE 4: RIGHT SIDE HORIZONTAL STABILIZER - FRONT SPAR CHORD LUGS - LUG BORE DETAILED
INSPECTION
(SHEET 4 OF 4)
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ALERTALERT

### Page 41

Logic diagrams are provided as an aid only. Information contained in Paragraph 1.E., Compliance is the primary
source for compliance times. Information contained in Paragraph 3.B., Work Instructions is the primary source
for tasks required for compliance.
LOGIC DIAGRAM FOR PARAGRAPH 1.E. COMPLIANCE: TABLE 1: INSPECT FOR CORROSION AND
ANY CRACK ON THE HORIZONTAL STABILIZER FRONT SPAR CHORD LUGS
1. The table below gives the description for the conditions called out in the logic diagrams.
DescriptionTitle
NO CORROSION AND NO CRACK FOUNDCONDITION 1
ANY CORROSION OR ANY CRACK FOUNDCONDITION 2
NO CORROSION FOUNDCONDITION 3
ANY CORROSION FOUNDCONDITION 4
APPENDIX A:  LOGIC DIAGRAMS FOR COMPLIANCE TASKS AND COMPLIANCE TIMES
(SHEET 1 OF 3)
Export Controlled ECCN: 9E991 - BOEING
PROPRIETARY - Copyright © Unpublished
Work - See page 1 for details.
Original Issue: August 07, 2015
737-55A1092
41 of 43
BOEING SERVICE BULLETIN 737-55A1092
ALERTALERT

### Page 42 (OCR)

BOEING SERVICE BULLETIN 737-55A1092
ALERT  ALERT
COMPLIANCE TIME
WITHIN 27 MONTHS
AFTER THE ORIGINAL
ISSUE DATE OF THIS
SERVICE BULLETIN.
DO PART 1 - HORIZONTAL
STABILIZER - FRONT SPAR CHORD
LUGS DETAILED AND ULTRASONIC
INSPECTIONS FOR CORROSION
AND ANY CRACK.
CONDITION 1  CONDITION 2
BEFORE FURTHER
24 MONTHS  FLIGHT
ACTION 1:
REPEART PART 1 - HORIZONTAL  CONTACT THE BOEING
STABILIZER - FRONT SPAR CHORD  COMPANY FOR REPAIR
LUGS DETAILED AND ULTRASONIC  INSTRUCTIONS AND DO
INSPECTIONS FOR CORROSION  THE REPAIR
AND ANY CRACK.
24 MONTHS
ACTION 2:
REPEAT PART 1 - HORIZONTAL
STABILIZER - FRONT SPAR CHORD
LUGS DETAILED AND ULTRASONIC
INSPECTIONS FOR CORROSION  AND ANY CRACK AT THE  2420154
UNREPAIRED LUGS.
APPENDIX A: LOGIC DIAGRAMS FOR COMPLIANCE TASKS AND COMPLIANCE TIMES
(SHEET 2 OF 3)
Original Issue: August 07, 2015
Export Controlled ECCN: 9E991 - BOEING  PROPRIETARY - Copyright © Unpublished  737-55A1092
Work - See page 1 for details.  42 of 43

### Page 43 (OCR)

BOEING SERVICE BULLETIN 737-55A1092
ALERT  ALERT
COMPLIANCE TIME
WITHIN 27 MONTHS
AFTER THE ORIGINAL
ISSUE DATE OF THIS
SERVICE BULLETIN.
DO PART 2 - HORIZONTAL
STABILIZER - FRONT SPAR
CHORD LUG BORES DETAILED
INSPECTION FOR CORROSION.
CONDITION 3  CONDITION 4
BEFORE FURTHER
96 MONTHS FROM  FLIGHT
LAST INSPECTION
ACTION 1:
CONTACT THE BOEING
REPEART DETAILED  COMPANY FOR REPAIR
INSPECTION FOR  INSTRUCTIONS AND DO
CORROSION.  THE REPAIR.
96 MONTHS
ACTION 2:
REPEAT PART 2 - HORIZONTAL
STABILIZER - FRONT SPAR CHORD
I LUG BORES DETAILED INSPECTION
FOR CORROSION AT THE  2420155
UNREPAIRED LUGS.
APPENDIX A: LOGIC DIAGRAMS FOR COMPLIANCE TASKS AND COMPLIANCE TIMES
(SHEET 3 OF 3)
Original Issue: August 07, 2015
PROPRIETARY - Copyright © Unpublished  Export Controlled ECCN: 9E991 - BOEING  737-55A1092
Work - See page 1 for details.  43 of 43

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