# Boeing Alert Service Bulletin 737-53A1042: U.S. DOT/FAA - Service Bulletin - SB-737-53-1042-09

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- Document: [Boeing Alert Service Bulletin 737-53A1042](https://openairdocs.org/service-documents/boeing/737-53a1042.md)
- Title as filed: U.S. DOT/FAA - Service Bulletin - SB-737-53-1042-09
- Pages: 43
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### Page 1

Commercial
Airplane
Group
737
Service Bulletin
Number: 737-53A1042 Revision Transmittal SheetDate: February 8,1974
Revision 9: July 25, 1991
ATA System: 5331
SUBJECT: FUSELAGE - LOWER LOBE HOT-BONDED SKIN PANEL INSPECTION, REPAIR, AND
PANEL REPLACEMENT
This revision includes all pages of the service bulletin.
SUMMARY
This revision is sent to make the kit applicability more clear, by using varable numbers in the Kit
Applicability Table.
Paragraph I.A., Effectivity, shows changes of airplane operators. Each operator should examine
the Effectivity paragraph for changes.
More work is necessary on airplanes changed by Part V of the revisions before Revision 5 of this
service bulletin. On these airplanes more work is necessary by service bulletin 737-53-1087. No
more work is necessary on airplanes changed by Part V of Revision 5 and subsequent revisions of
this service bulletin. The lower fuselage skin aft of Body Station 727 installed by this service
bulletin is examined for cracks and repaired when it is necessary.
Vertical lines are put on the left edge of each page, except in paragraph I.A., Effectivity, to show
the location of important changes.
REVISION HISTORY
Initial Release: Feburary 8, 1974
Revision 1: Feburary 4, 1977
Revision 2: March 31, 1978
Revision 3: December 4, 1981
Revision 4: November 5, 19882
Revision 5: October 5, 1984
Revision 6: August 10, 1989
Revision 7: October 19, 1989
Revision 8: July 19, 1990
Revision 9: July 25, 1991
BOEING COMMERCIAL AIRPLANE GROUP P.O. BOX 3707 SEATTLE, WASHINGTON 98124-2207

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Commercial
Airplane
Group
737
Service Bulletin
Number: 737-53A1042 SummaryDate: February 8,1974
Revision 9: July 25, 1991
ATA System: 5331
SUBJECT: FUSELAGE - LOWER LOBE HOT-BONDED SKIN PANEL INSPECTION, REPAIR, AND
PANEL REPLACEMENT
BACKGROUND
Based on a structural review of the 737 airplane,
incorporation of the modification per this service
bulletin is recommended on aging airplanes.
To date, numerous reports have been received
of lower lobe doubler to skin bond separation,
corrosion and cracks on airplanes with service
lives ranging upwards from 1400 flight hours.
The affected areas were between Stringers 26L
and 26R under the forward cargo compartment
and between Stringers 25L and 25R under the
aft cargo compartment. In the absence of
periodic inspections and repairs as described
herein, or an equivalent corrosion protection
program, corrosion, bond separation and skin
cracking could progress to an extreme situation
which might involve rapid decompression and
possible loss of the airplane.
This service bulletin is the subject of Federal
Aviation Administration (FAA) Airworthiness
Directive 82-01-09, Amendment 39-4299.
ACTION (PRR 32349 and 32355)
As recommended by the 737 Aging Fleet
Structures Working Group, accomplish the
modification per the Accomplishment
Instructions at or before the accumulation of
75,000 flight cycles or 20 years airframe age,
whichever occurs first.
Visually inspect the exterior and interior of the
affected panels and apply corrosion inhibitor at
two year intervals until the panels are replaced
with solid panels. On airplanes not inspected
internally and externally, including externally
under the wing to body fairings, per previous
issue of this bulletin within twelve months prior
to Revision 3, inspect within three months.
Panel damage exceeding specified limits should
be repaired or the panel should be replaced
before further flight.
EFFECTIVITY
Group 1: Line Numbers 001 through
399 and 401
Group 2: Line Numbers 400, 402
through 410, 412 through 418
and 432
MANPOWER
See service bulletin.
MATERIAL INFORMATION
See Paragraph I.F for applicable terms and
conditions.
BOEING COMMERCIAL AIRPLANE GROUP P.O. BOX 3707 SEATTLE, WASHINGTON 98124-2207 Summary Page 1 of 2

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BOEING SERVICE BULLETIN 737-53A1042
Feb 8/74
REV. 9: Jul 25/91 Summary Page 2 of 2

### Page 5

Commercial
Airplane
Group
737
Service Bulletin
Number: 737-53A1042
Date: February 8,1974
Revision 9: July 25, 1991
ATA System: 5331
SUBJECT: FUSELAGE - LOWER LOBE HOT-BONDED SKIN PANEL INSPECTION, REPAIR, AND
PANEL REPLACEMENT
I. PLANNING INFORMATION
A. Effectivity
1. Airplanes
Refer to Service Bulletin Index Document D6-19567, Part 3 for Airplane Variable Number, Line
Number, and Serial Number data.
Solid skin panels were installed in production in accordance with PRR 32349 and PRR 32355
on applicable airplanes other than those listed below.
Affected airplanes are divided into two groups because of differences in doubler configuration.
LISTING BY CUSTOMER, CUSTOMER CODE, GROUP AND VARIABLE NUMBER
CUSTOMER
GROUP VARIABLE NUMBER
A. L. I. (IBA)
1 PJ109
AER LINGUS (ARL)
1 PG251 PG253-PG255 PG573 PG575 PY321-PY323
AEROLINEAS ARGENTINAS (ARG)
1 PH705-PH708 PH741-PH743 PK102-PK103 PY007-PY008
AIR ALGERIE (ALG)
1 PL717-PL718 PY051-PY052
2 PL719-PL721
AIR ASIATIC LTD. (AZC)
1 PG047
Feb 8/74 737-53A1042
REV. 9: Jul 25/91 Page 1of 38

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BOEING SERVICE BULLETIN 737-53A1042
LISTING BY CUSTOMER, CUSTOMER CODE, GROUP AND VARIABLE NUMBER, (continued)
CUSTOMER
GROUP VARIABLE NUMBER
AIR LANKA, LTD. (LNK)
1 PH701 PL802
AIR MADAGASCAR (MAD)
1 PG375 PL793
AIR NEW ZEALAND, LTD. (ANZ)
1 PK047
AIR NIPPON CO., LTD. (ANK)
1 PG582
AIR ZAIRE (ZAI)
1 PX701 PY111 PY113
AIRCRAFT SUPPORT GROUP (ASG)
1 PY342 PY344
ALASKA AIRLINES (ASA)
1 PY112
ALL NIPPON AIRWAYS CO. LTD. (ANA)
1 PG578-PG581 PG583-PG586
ALOHA (ALO)
1 PG046 PG629 PG705 PY001 PY005
AMERICA WEST AIRLINES, INC. (AMW)
1 PC004 PG036 PG221 PG331 PG577 PJ102
PL801
AMERICAN AIRLINES, INC. (AAL)
1 PG204 PG271-PG276 PG278 PG351 PG403
AMMAN AVIATION CO. (MNN)
1 PG224
ANSETT NEW ZEALAND (AZE)
1 PA001 PA003-PA004 PC003
ATLANTA ICELANDIC (AID)
1 PY002 PY381
AVIATECA (AVT)
1 PG201 PG352
AVIATION SALES CO., INC. (ASC)
1 PG401-PG402 PG436 PG572 PG574 PY343
BRAATHENS S.A.F.E. (BRT)
1 PJ031 PJ072
BRANIFF AIRLINES (BNF)
1 PG034
BRITANNIA AIRWAYS, INC. (BRI)
1 PJ101 PJ103-PJ108 PL716
CAMEROON AIRLINES (CAM)
1 PY046-PY047
Feb 8/74 737-53A1042
REV. 9: Jul 25/91 2

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BOEING SERVICE BULLETIN 737-53A1042
LISTING BY CUSTOMER, CUSTOMER CODE, GROUP AND VARIABLE NUMBER, (continued)
CUSTOMER
GROUP VARIABLE NUMBER
CANADIAN AIRLINES INTERNATIONAL LTD. (CDI)
1 PG651-PG652 PK026-PK028 PL761-PL762 PL764-PL766 PY303-PY304
CARNIVAL AIR (CVL)
1 PG312 PL712
CASINO EXPRESS (CIN)
1 PG279
CONTINENTAL AIRLINES, INC. (CAL)
1 PA006-PA022 PG056 PG064 PG199 PG225 PG229
PG432-PG433 PG441-PG442 PG501-PG505 PG621-PG628 PG630 PG704
2 PL001
COPA COMPANIA PANAMENA DE AVIATION S.A. (COP)
1 PC001 PY341
CRUZEIRO DO SUL (CRU)
1 PK141-PK143
2 PK144-PK146
E G AND G (EGN)
1 PG037 PG208 PG210 PG215 PG431 PL763
EURALAIR (ERA)
1 PG026 PG028-PG029 PY004 PY006
FAR EASTERN AIR TRANSPORT (FAT)
1 PA002 PA005 PG055 PG226 PG228 PG230
FAUCETT (COMPANIA DE AVIATION S.A. (FCT)
1 PA231 PC002 PG213 PG252
GATX CAPITAL CORPORATION (GAX)
1 PA232
GOVERNMENT OF MEXICO (MXG)
1 PC005 PG223
INDIAN AIRLINES (IND)
1 PH021-PH022 PH024 PH709 PH711-PH713
IRAN ISLAMIC REPUBLIC AIRLINE (IRN)
1 PH731 PY021-PY022
IRAQI AIRWAYS (IRQ)
1 PY141-PY142
LINHAS AEREAS DE MOCAMBIQUE (LAM)
1 PH703 PY031
LUFTHANSA GERMAN AIRLINES (DLH)
1 PY345-PY346
MALAYSIAN AIRLINES SYSTEM BERHAD (MAS)
1 PL736-PL738 PL740-PL743
MARKAIR, INC. (ALK)
1 PG219
Feb 8/74 737-53A1042
REV. 9: Jul 25/91 3

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BOEING SERVICE BULLETIN 737-53A1042
LISTING BY CUSTOMER, CUSTOMER CODE, GROUP AND VARIABLE NUMBER, (continued)
CUSTOMER
GROUP VARIABLE NUMBER
NASA (NAS)
1 PA099
NIGERIA AIRWAYS, LTD. (NIA)
1 PL781-PL782
NWT AIR (NTA)
2 PY132-PY133
PAN AFRICAN EXPRESS (PFX)
1 PG211
PAN AMERICAN WORLD AIRWAYS, INC. (PAA)
1 PG020-PG021 PG043 PG048
POLARIS LEASING CO. (PLS)
1 PG202-PG203 PG205 PG207 PG216-PG218 PG220 PG222
PG438
SABA AIRLINES S. A. (SBA)
1 PG209 PG212
SABENA BELGIAN WORLD AIRLINES (SAB)
1 PK041 PK044-PK046 PY272
2 PK048 PY273
SAUDI ARABIAN AIRLINES CORP. (SVA)
1 PL726-PL730 PY036-PY037
SOCIETE D'EXPLOITATION AEROPOSTALE (ICS)
1 PY302
SOUTH AFRICAN AIRWAYS (SAA)
1 PG353-PG356
SOUTHWEST AIRLINES CO. (SWA)
1 PK091
SULTANAIR (SLR)
1 PJ001 PJ032 PL803
TACA INTERNATIONAL AIRLINES, INC. (TAC)
1 PG059 PY131
TAN SAHSA HONDURAS AIRLINES (SAH)
1 PG434 PJ071 PK081 PL711 PL758
TIME AIR SWEDEN AB (TIS)
1 PJ002-PJ003
TRANS EUROPEAN AIRWAYS (TEA)
1 PK042-PK043
TRANSAVIA AIRLINES (TAV)
1 PG074 PY101
2 PY102-PY103
TRANSPORT AERIEN TRANSREGLONAL (TTR)
1 PY003 PY301 PY361-PY362
Feb 8/74 737-53A1042
REV. 9: Jul 25/91 4

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BOEING SERVICE BULLETIN 737-53A1042
LISTING BY CUSTOMER, CUSTOMER CODE, GROUP AND VARIABLE NUMBER, (continued)
CUSTOMER
GROUP VARIABLE NUMBER
UNITED AIR LINES, INC. (UAL)
1 PG001-PG004 PG006-PG019 PG022-PG025 PG027 PG030 PG032-PG033
PG038-PG040 PG044-PG045 PG051-PG054 PG057 PG060-PG063 PG065-PG072
PG075
UNITED STATES AIR FORCE (USF)
1 PJ201-PJ219
USAIR, INC. (USA)
1 PG041-PG042 PG049 PG073 PG206 PG301-PG311 PG313-PG314
PG474 PG576
VARIG AIRLINES (VAR)
1 PK111-PK116
2 PK118-PK120
VASP (VSP)
1 PG435 PG437 PG439-PG440 PG471-PG473 PH011-PH013 PK061-PK062
PK065 PL756 PX071
2 PK066-PK067
WHIRLPOOL FINANCIAL CORP (ZZW)
1 PG214
LISTING BY VARIABLE NUMBER
GROUP 1
PA001-PA022 PA099 PA231-PA232 PC001-PC005 PG001-PG075 PG199
PG201-PG230 PG251-PG255 PG271-PG279 PG301-PG314 PG331-PG332 PG351-PG356
PG375 PG401-PG403 PG431-PG442 PG471-PG475 PG501-PG505 PG571-PG586
PG621-PG630 PG651-PG652 PG701-PG705 PH001 PH011-PH013 PH021-PH024
PH701-PH715 PH731-PH732 PH741-PH743 PJ001-PJ003 PJ031-PJ032 PJ071-PJ072
PJ101-PJ109 PJ201-PJ219 PK026-PK028 PK041-PK047 PK061-PK065 PK081
PK091 PK101-PK103 PK111-PK117 PK141-PK143 PL711-PL712 PL716-PL718
PL726-PL730 PL736-PL743 PL756 PL758 PL761-PL766 PL781-PL782
PL793 PL801-PL803 PX071 PX701 PY001-PY008 PY021-PY022
PY031 PY036-PY037 PY046-PY047 PY051-PY052 PY101 PY111-PY113
PY131 PY141-PY142 PY271-PY272 PY301-PY304 PY321-PY323 PY341-PY346
PY361-PY362 PY381
GROUP 2
PK048 PK066-PK067 PK118-PK120 PK144-PK146 PL001 PL719-PL721
PY102-PY103 PY132-PY133 PY273
2. Spares
None
Feb 8/74 737-53A1042
REV. 9: Jul 25/91 5

### Page 10

BOEING SERVICE BULLETIN 737-53A1042
B. Reason
As a result of the FAA sponsored Aging Fleet Conference, a 737 Structures Working Group with
Airline and Boeing members and FAA observers was formed to review structural service bulletin
modifications and recommend selected bulletins for incorporation on aging airplanes. This service
bulletin modification has been recommended for incorporation on aging 737 airplanes.
Periodic inspection per this service bulletin will determine the structural condition of the lower lobe
hot bonded skin panels under the forward and aft cargo compartments. Application of corrosion
inhibitor after inspection will reduce the probability of corrosion. Bond separation, corrosion and
skin cracking could progress to an extreme situation which might involve rapid decompression and
possible loss of the airplane.
The original issue of this bulletin reported doubler to body skin bond separation and corrosion on 15
airplanes that had accumulated 5000 to 10,000 flight hours. The affected areas were between
Stringers 26L and 26R under the forward cargo compartment and between Stringers 25L and 25R
under the aft cargo compartment. In most instances, the bond separation and corrosion was
located under the aft half of the forward compartment. The bulletin advised an external and internal
inspection of the affected areas on earlier production airplanes at two year intervals and application
of corrosion inhibitor after each inspection. Repairs were also provided.
Revision 1 of the bulletin was issued to provide instructions for replacing damaged lower bonded
skin panels with one piece (solid panels). The effectivity of the bulletin was also expanded to
include later production airplanes (described as Groups 2, 3 and 4 airplanes) with bonded lower
lobe panels which had various improvements incorporated in production to retard bond separation
and corrosion. Inspection per the bulletin was not required on the later airplanes but proper
maintenance of seals and application of corrosion inhibitor during maintenance was emphasized.
Revision 2 was issued to provide a single set of jacking loads and instructions suitable for
replacement of all lower lobe bonded skin panels.
Subsequent to issue of Revision 2, reports were received of lower lobe doubler to skin bond
separation, corrosion and cracks on airplanes with service lives ranging upwards from 1400 flight
hours. In addition, operators had acquired 149 solid skin panels for replacement of bonded panels.
Revision 3 was issued to change the bulletin to an "ALERT" status bulletin and extend inspection
to all airplanes with bonded lower lobe skin panels in the affected areas under the forward and aft
cargo compartments. While it is believed that the improvements incorporated in bonded panels on
later production airplanes (described as Group 2, 3 and 4 airplanes in previous issues of the
bulletin) will result in fewer instances of delamination damage, because of the possibility of such
damage, inspection per this bulletin is recommended.
Revision 4 was issued to provide panel replacement kits for seventeen of the additional airplanes
requiring inspection per Revision 3. The original kits are suitable for all other added airplanes. The
instructions for inspecting the skin under the forward fairing have been changed because of access
difficulties, and the information in Notice of Status Change 737-53A104NSC1, dated Dec 18/81 is
incorporated.
Revision 5 was issued to add new lower fuselage skin replacement kits in which skin and doublers
are sealed together upon installation. The new kits also provide protruding head fasteners for a
critical area to eliminate the countersink knife edges of the fastener holes common to the keel beam
and stringer 27 splice area.
Revision 6 was issued to provide the recommendations of the Aging Fleet 737 Structures Working
Group.
Feb 8/74 737-53A1042
REV. 9: Jul 25/91 6

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BOEING SERVICE BULLETIN 737-53A1042
Revision 7 was issued to correct a typographical error in Paragraph I.F. Material - Price and
Availability. The correct delivery and unit price for Kits 65-88943-53 and -54 were listed.
Paragraph 4, in C. Description, was changed to clarify modifications required.
Revision 8 was issued to correct the applicability of Kit 65-88939-11, on Page 20, under II.A.2. The
applicability is changed from P3628-P3636, P3627 to P3628-P3630, P3637. Service bulletin partial
Revision 7 has been included.
Revision 9 is sent to make the kit applicability more clear, by using varable numbers in the Kit
Applicability Table.
C. Description
Based on a structural review of the 737 airplane, it is recommended that the modification per the
Accomplishment Instructions of this service bulletin be accomplished prior to, or upon the
accumulation of 75,000 flight cycles or 20 years, whichever occurs earliest.
Inspection for separation of the doubler to skin bond, corrosion and cracks in the lower lobe body
skin panels consists of an external and internal visual inspection between BS (Body Station) 360
and 540 and Stringers 26L and 26R, and between BS 727 and 1016 and Stringers 25L and 25R, at
two year intervals. On airplane PK067 only, solid skin panels were installed in production between
BS 360 and 540 and inspection is required only between BS 727 and 1016 and Stringers 25L and
25R.
The inspections should be scheduled into regular maintenance visits as close as possible to the
intervals specified.
Airplanes modified per revisions prior to Revision 5 of this service bulletin require additional work
per Service Bulletin 737-53-1087. Airplanes modified per Revision 5, Part V of the Accomplishment
Instructions, or later revisions do not require additional work.
On airplanes inspected internally and externally including externally under the wing to body fairings
within twelve months prior to issue of Revision 3, continue the external and internal inspections at
two year intervals.
On all other affected airplanes, do the initial external and internal inspection within three months
following receipt of Revision 3 of the bulletin. Alternatively, the initial internal inspection may be
delayed if the external inspection is done within three months, nine months and fifteen months
following receipt of Revision 3.
Following the three external inspections, do the external and internal inspection within twenty one
months after receipt of Revision 3 and repeat both inspections at two year intervals.
External inspection requires access under the wing to body fairing and should include the skin lap
joints at the edges of the affected areas. Visually inspect for skin bulges and external cracks
adjacent to fastener heads and for "dished" or missing fastener heads, indicating corrosion and
separation of the bond between the skin and internal doubler. If no such indications are found,
continue the external visual inspections at the specified intervals.
Revision 3 of the bulletin advised that inspection under the forward fairing could be done by
removing the air conditioning bay access panels and viewing the body skin through openings in the
aft end of the fairing at BS 540. Further experience indicates that such inspection may not detect
all bulges and cracks that may occur and the procedure has been changed.
Feb 8/74 737-53A1042
REV. 9: Jul 25/91 7

### Page 12

BOEING SERVICE BULLETIN 737-53A1042
Airplanes inspected externally under the forward fairing without fairing removal, per Revision 3,
require reinspection per Revision 4 within three months after receipt of Revision 4 or at the next
scheduled inspection, whichever comes first.
If external skin cracks or missing fastener heads are found, repair before further flight. If skin
bulges or "dished" fastener heads are found, inspect for skin thickness reduction caused by internal
corrosion, and cracks in the skin inner surface at the fasteners, using low frequency eddy current
inspection or operator's comparable procedure. If skin thickness loss exceeds 10%, or if cracks are
found, repair before further flight. If skin thickness loss does not exceed 10% and no cracks are
found, externally inspect the damage area as previously described at three month intervals for
corrosion progression and crack initiation.
If one or more areas of skin bulging is found, with or without "dished" fastener heads, and is within
specified limits, the low frequency eddy current inspection may be deferred if the affected area are
visually inspected at one month intervals for bulge enlargement, skin cracks and missing fastener
heads. Each bulge should not exceed 10.0 inches in length and the nearest ends of any two bulges
located along the same stringer, or the same frame, or on a stringer and an intersecting frame,
should not be closer than 24.0 inches, except any two bulges occurring at two adjacent stringers or
at two adjacent frames may be closer than 24.0 inches. If the bulge, or bulges, exceed the limits,
low frequency eddy current inspect the affected area as previously described.
Complete repair and interim repair are provided for damage found when doing the external
inspection. Complete repair requires internal access to the affected panel. Interim repair can be
done from outside the panel and requires replacement by the complete repair within one year after
installation or at the first internal inspection, whichever comes first.
Internal inspection requires removal of the cargo compartment floors, interior panels and insulation
blankets to expose the inspection areas. On Group 1 airplanes, the doubler bonded to the inner
surface of the skin was chemically milled away between frames and stringers, exposing the inner
surface of the skin. In previous issues of the bulletin the milled doubler was described as a "Waffle"
doubler. On Group 2 airplanes, no chem milling was done and consequently the skin inner surface
is not exposed.
On all affected airplanes, clean the inner surface of the internal doubler and the inner surface of the
skin, where exposed by chem milled openings in the doubler. Visually inspect for corrosion and
cracks in the inner surfaces and for missing fastener heads. Also inspect for bulges in the doubler,
indicating corrosion between the skin and doubler and bond separation.
On Group 1 airplanes, also inspect for indication of skin to doubler bond separation around the
chem milled openings in the inner doubler. Separation is often indicated by a thin black line on the
skin at the edge of the doubler opening. Check indicated area by pushing the skin outwards to
further separate the skin and doubler.
If corrosion, cracks, missing fastener heads or bond separation are found, repair per instructions
provided herein or replace panel with a solid panel. Upon completion of inspection, and any
necessary repair, apply a saturation coating of corrosion inhibitor to all interior surfaces of the
affected areas and continue inspection at the specified intervals.
For operator installing a new lower fuselage skin between BS 727 and BS 908 per Revision 5 of this
bulletin, install protruding head fasteners in the keel beam splice area per Drawing 65-88943,
supplied in support of this bulletin revision.
Accomplish the instructions specified in D6-38528 "Corrosion Prevention and Control Program"
after the skin panels are replaced per Rev. 5 (or later Revision), Part V of the Accomplishment
Instructions.
Feb 8/74 737-53A1042
REV. 9: Jul 25/91 8

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BOEING SERVICE BULLETIN 737-53A1042
NOTES: 1. If the damaged area is more than the specified limits, write to Boeing for repair
instructions. To help Boeing send a reply, give the limits and location of the
damage. When possible, send sketches and photographs. If the damage
includes corrosion, send data on the length, width, and largest depth of clean up.
SEND TO: BOEING COMMERCIAL AIRPLANE GROUP
ATTENTION: MANAGER, AIRLINE SUPPORT
2. On all applicable airplanes, before or during the changes specified in this service
bulletin, the changes are recommended to be made as shown in these Service
Bulletins :
- 737-25-1085, "Thermal Insulation Blanket Support Installation"
- 737-53-1039, "Body Skin Lap Joint Inspection and Repair"
- 737-53-1081, "Fuselage Drainage Improvement, Section 46"
- 737-53-1087, "Fuselage Lower Lobe Skin Panel Inspection".
3. The Boeing Company offers a three day no charge low frequency eddy current
familiarization course designed for inspectors who are already familiar with high
frequency eddy current inspection. A portion of the course is devoted to corrosion
inspection and evaluation. Information regarding the course may be obtained
through the Airline Support Manager.
4. This service bulletin is listed in Boeing Document D6-38505.
D. Approval
This service bulletin was examined by the Federal Aviation Administration (FAA). The repairs and
changes specified in this service bulletin comply with the applicable Federal Aviation Regulations
(FAR) and are FAA approved.
Feb 8/74 737-53A1042
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BOEING SERVICE BULLETIN 737-53A1042
E. Manpower
The data below shows an estimate of the man-hours necessary to do this repair or replacement for
each airplane. This estimate is for direct labor only, done by an experienced crew. Adjust the
estimate with operator man-hour data if necessary. It does not include lost time such as:
- Time to adjust to the workplace
- Time to schedule the work
- Time to examine the work
- Time to cure the materials
- Time to make the parts
- Time to find the tools.
- Time to do the other service bulletins specified in Paragraph I.C., Description.
TABLE 1 Man - Hour Estimate Per Airplane
Task
Number of
Persons Man-Hours
Elapsed
Time
(Hours)
Open Access 4 12 3
Examine 2 (a) (a)
Repair 2 (a) (a)
Close Access 4 16 4
TOTAL PER AIRPLANE 28(b) 7(b)
Replace
BS360-BS540 6 792 132
BS727-BS908 6 840 140
BS908-BS1016 6 480 80
TOTAL PER AIRPLANE 2112 352
Interim Repair
Open Access 4 12 3
Repair 2 (a) (a)
Close Access 4 16 4
TOTAL FOR AIRPLANE 28(b) 7(b)
(a) Dependent on extent of inspection and repair required.
(b) In addition to inspection and repair.
Feb 8/74 737-53A1042
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BOEING SERVICE BULLETIN 737-53A1042
F. Material - Price and Availability
1. Operator Furnished
The operator can supply the parts and materials shown in Paragraph II.A.1, Parts Necessary
For Each Airplane. As an alternative, operators can purchase the parts from Boeing Spares.
This service bulletin does not show the Boeing price and supply data.
2. Available from Boeing
Boeing can supply the kits shown in Paragraph II.A.2, Parts Necessary For Each Airplane, as
shown below. Kit availability is shown in the Reorder Lead Time (ROLT). ROLT is calculated
from the date Boeing gets the purchase order.
Kit Number Name ROLT (Weeks) Unit Price
65-88939-1 Kit 47 $14,268.00
65-88939-9 Kit 47 $14,866.00
65-88939-10 Kit 47 $13,848.00
65-88939-11 Kit 47 $13,663.00
65-88939-12 Kit 47 $13,836,00
65-88939-13 Kit 43 $14,131.00
65-88939-14 Kit 43 $14,288.00
65-88939-15 Kit 43 $13,592.00
65-88939-16 Kit 39 $13,080.00
65-88939-17 Kit 43 $13,645.00
65-88939-18 Kit 43 $13,569.00
65-88939-23 Kit 49 $14,354.00
65-88939-24 Kit 44 $14,871.00
65-88939-29 Kit 53 $13,905.00
65-88939-30 Kit 53 $13,746.00
65-88939-31 Kit 44 $14,480.00
65-88939-32 Kit 53 $13,828.00
65-88942-1 Kit 44 $8,159.00
65-88942-5 Kit 44 $7,916.00
65-88942-6 Kit 44 $8,011.00
65-88943-1 Kit 44 $3,546.00
65-88943-4 Kit Inactive for Procurement
65-88943-24 Kit Inactive for Procurement
65-88943-25 Kit Inactive for Procurement
65-88943-26 Kit Inactive for Procurement
Feb 8/74 737-53A1042
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BOEING SERVICE BULLETIN 737-53A1042
Kit Number Name ROLT (Weeks) Unit Price
65-88943-27 Kit Inactive for Procurement
65-88943-31 Kit Inactive for Procurement
65-88943-32 Kit Inactive for Procurement
65-88943-42 Kit 58 $16,339.00
65-88943-43 Kit 58 $12,909.00
65-88943-44 Kit 58 $13,480.00
65-88943-45 Kit 60 $15,408.00
65-88943-46 Kit 58 $14,224.00
65-88943-47 Kit 58 $14,105.00
65-88943-48 Kit Supplemental 15 $419.00
65-88943-49 Kit Supplemental 15 $718.00
65-88943-50 Kit Supplemental 15 $621.00
65-88943-51 Kit Supplemental 15 $640.00
65-88943-52 Kit Supplemental 15 $730.00
65-88943-53 Kit Supplemental 15 $49.10
65-88943-54 Kit 58 $7,452.00
Date July 25, 1991
The kits are subject to the terms and conditions of Boeing's standard purchase order
acknowledgment. The prices and ROLT are subject to acceptance within 180 days from the date
shown above. After 180 days, new price and ROLT data is applicable. Prices are in United States
Dollars. Terms: Net 30 days.
Send purchase orders and letters about the supply data to the Director of Spares and refer to this
service bulletin number.
G. Special Tools - Price and Availability
None
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BOEING SERVICE BULLETIN 737-53A1042
H. Weight and Balance
Kit Number
Change in
Weight
(Pounds)
Change in Moment
(Pound-Inches)
Model 737-100 Airplanes
65-88942-1 +4.1 +1836
65-88942-5 +4.1 +1836
65-88942-6 +4.1 +1836
65-88943-1 +2.1 +2059
65-88943-4 +2.1 +2059
65 88943-54 +2.1 +2059
Model 737-200 Airplanes
65-88939-1 +4.8 +1979
65-88939-9 +4.8 +1979
65-88939-10 +4.8 +1979
65-88939-11 +4.8 +1979
65-88939-12 +4.8 +1979
65-88939-13 +4.8 +1979
65-88939-14 +4.8 +1979
65-88939-15 +4.8 +1979
65-88939-16 +4.8 +1979
65-88939-17 +4.8 +1979
65-88939-18 +4.8 +1979
65-88939-23 +4.8 +1979
65-88939-24 +4.8 +1979
65-88939-29 +5.0 +2160
65-88939-30 +5.0 +2160
65-88939-31 +5.0 +2160
65-88939-32 +5.0 +2160
65-88943-1 +2.1 +2102
65-88943-24 +7.0 +7310
65-88943-25 +7.0 +7310
65-88943-26 +7.0 +7310
65-88943-27 +7.0 +7310
65-88943-31 +7.0 +7310
65-88943-32 +7.0 +7310
65-88943-42 +7.0 +7310
65-88943-43 +7.0 +7310
65-88943-44 +7.0 +7310
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BOEING SERVICE BULLETIN 737-53A1042
Kit Number
Change in
Weight
(Pounds)
Change in Moment
(Pound-Inches)
65-88943-45 +7.0 +7310
65-88943-46 +7.0 +7310
65-88943-47 +7.0 +7310
I. References
1. Existing Data:
a. Engineering Change Memo PRR32198, PRR32349 and PRR32355
b. Corrosion Prevention Manual Part III, Subject 53-30-37
c. 737 Maintenance Manual Subjects 7-11-11 and 12-32-11
d. 737 Boeing Standard Overhaul Practices Manual 20-41-01
e. 737 Structural Repair Manual Subjects 51-10-2, 51-40-5, 53-30-1 and 53-30-3
f. 737 Nondestructive Test Manual Part 6 Subject 51-00-00, Figure 5
g. Boeing Service Bulletins:
o 737-25-1085 "Thermal Insulation Blanket Support Installation"
o 737-53-1039 "Body Lap Joint Inspection and Repair"
o 737-53-1081 "Fuselage - Drainage Improvement", Section 46
o 737-53-1087, "Fuselage - Lower Lobe Skin Panel Inspection"
h. Boeing Document D6-38505 "Aging Airplane Service Bulletin Structural Modification
Program - Model 737-100/-200/-200C
i. Boeing Document D6-38528 "Corrosion Prevention and Control Program"
j. FAA Airworthiness Directives 82-01-09, Amendment 39-4299, and 90-06-02, Amendment
39-6489
Feb 8/74 737-53A1042
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BOEING SERVICE BULLETIN 737-53A1042
2. This data was supplied with Revision 8 of this service bulletin:
Drawing No. Sheet DCN ADCN Title
65-88939 Pl
1
2
3
4
5
6
7
8
9
10
11
G
D
C
A
A
A
A
A
A
-
-
-
4,5
1
1
-
-
-
-
-
-
-
-
-
Kit, Panel Instl, S-26L to S-26R, Sta. 360
to Sta. 540
65-88942 Pl
1
2
3
D
A
A
A
1,2
-
1
-
Kit, Panel Instl, S-26L to S-26R, Sta. 360
to Sta. 540
65-88943 Pl
1
2
3
4
5
H
A
B
A
A
-
11,12
1
2,3,4,5
1,2,3,4,5
1,2,3,4,5,6,7
-
Kit, Skin Panel Instl, S-25L to S-25R,
Sta. 727 to Sta. 1016
3. Boeing Process Specifications referred to on drawings are not given in this service bulletin since
these procedures are frequently used as standard shop practices.
J. Publications Changed
Publication Chapter-Section
737 Structural Repair Manual 53-30
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BOEING SERVICE BULLETIN 737-53A1042
II. MATERIAL INFORMATION
A. Parts Necessary For Each Airplane
1. Parts and Materials Supplied by the Operator:
Quantity
Part Number
(Specification) Name
As Required
As Required
As Required
As Required
As Required
As Required
As Required
BACR15CE5D( )
BACR15ET7D( )
MS20470D5-( ) (c)
MS20470D6-( ) (c)
MS20470D8-( ) (c)
BMS 5-95 Class C,(a)(d)
BMS 3-23 Type I or II(b)(e)
Rivet
Rivet
Rivet
Rivet
Rivet
Sealant
Organic Corrosion Inhibiting Compound
(a) BMS 5-95 preferred, BMS 5-79 optional.
(b) Each operator should evaluate his airplane's operational environment, the corrosion inhibitor
used and the application schedule to ensure adequate corrosion protection. The use of an
organic corrosion inhibitor meeting the standard of BMS 3-23 is preferred.
(c) BACR15BB( )D( ) Optional
(d) See Boeing Standard Practices Overhaul Manual Subject 20-50-12.
(e) See Boeing Structural Repair Manual Subject 51-10-2.
Feb 8/74 737-53A1042
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BOEING SERVICE BULLETIN 737-53A1042
2. To get the kits shown below, refer to Paragraph I.F., Material - Price and Availability.
NOTE: In the following tables see drawing PL for list of parts.
65-88942 - KIT, PANEL INSTALLATION, S-26L TO S-26R STA 360 TO STA 540
(737-100 ONLY)
65-88943 - KIT, PANEL INSTALLATION, S-25L TO S-25R STA 727 TO STA 908
(737-100 and -200)
Airplane Applicability Kit Number
737-100 Airplanes
PA001-PA013 PA099 65-88942-5, 65-88943-54
and 65-88943-1
PA014-PA016 PA231-PA232 65-88942-6, 65-88943-54
and 65-88943-1
PA017-PA022 PC001-PC005 65-88942-1, 65-88943-54
and 65-88943-1
NOTE: The following table applies to 737-100 airplanes only, it lists inactive kits and
corresponding supplemental kits and superseding kits.
Inactive Kit Supplemental Kit Superseding Kit
65-88943-4 65-88943-53 65-88943-54
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BOEING SERVICE BULLETIN 737-53A1042
65-88939 - KIT, PANEL INSTALLATION, S-26L TO S-26R STA 360 TO STA 540
(737-200 ONLY)
65-88943 - KIT, PANEL INSTALLATION, S-25L TO S-25R STA 727 TO STA 908
(737-100 and -200)
Airplane Applicability Kit Number
737-200 Airplanes
PG001-PG014
PG301
PG199 PG271-PG272 65-88939-18, 65-88943-42
and 65-88943-1
PG015-PG030
PG273-PG276
PG351-PG352
PG501-PG505
PH713-PH714
PG032-PG042
PG302-PG306
PG401-PG403
PG580-PG583
PH731-PH732
PG201-PG217
PG331-PG332
PG431-PG434
PH701
PH741-PH742
65-88939-17, 65-88943-42
and 65-88943-1
PG043-PG075
PG277-PG279
PG375-PG375
PG571-PG579
PG701-PG705
PG218-PG230
PG307-PG314
PG435-PG442
PG621-PG630
PH702-PH712
PG251-PG255
PG353-PG356
PG471-PG475
PG651-PG652
65-88939-1, 65-88943-42
and 65-88943-1
PG584-PG586 PH021-PH024 PH743 65-88939-12, 65-88943-42
and 65-88943-1
PH001 PH011-PH013 65-88939-11, 65-88943-42
and 65-88943-1
PJ001-PJ002
PJ101-PJ104
PJ031-PJ032
PL801-PL803
PJ071-PJ072 65-88939-1, 65-88943-44
and 65-88943-1
PJ003
PL793-PL793
PJ105-PJ109 PK041-PK046 65-88939-12, 65-88943-45
and 65-88943-1
PJ201-PJ219 65-88939-24, 65-88943-46
and 65-88943-1
PK026-PK028
PK081
PK111-PK117
PL726-PL730
PL758
PK047
PK091
PK141-PK143
PL736-PL743
PL761-PL766
PK061-PK065
PK101-PK103
PL717-PL718
PL756
PL781-PL782
65-88939-11, 65-88943-45
and 65-88943-1
PK048 PK118-PK120 65-88939-29, 65-88943-45
and 65-88943-1
PK066
PL719-PL721
PK144-PK146 PL001 65-88939-30, 65-88943-45
and 65-88943-1
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BOEING SERVICE BULLETIN 737-53A1042
Airplane Applicability Kit Number
737-200 Airplanes (continued)
PL711-PL712 PL716 65-88939-16, 65-88943-44 and
65-88943-1
PX071
PY302-PY303
PY346
PX701
PY321-PY323
PY361-PY362
PY003-PY308
PY341-PY344
65-88939-9, 65-88943-43 and
65-88943-1
PY001-PY002 PY301 65-88939-14, 65-88943-43 and
65-88943-1
PY021 PY031 65-88939-15, 65-88943-43 and
65-88943-1
PY022
PY051-PY052
PY131
PY036-PY037
PY101
PY141-PY142
PY046-PY047
PY111-PY113
65-88939-10, 65-88943-47 and
65-88943-1
PY102-PY103 PY132-PY133 65-88939-32, 65-88943-47 and
65-88943-1
PY271-PY272 65-88939-23, 65-88943-47 and
65-88943-1
PY273 65-88939-31, 65-88943-47 and
65-88943-1
PY304 PY345 PY381 65-88939-13, 65-88943-43 and
65-88943-1
NOTE: The following table applies to 737-200 airplanes only, it lists inactive kits and
corresponding supplemental kits and superseding kits.
Inactive Kit Supplemental Kit Superseding Kit
65-88943-24 (a) 65-88943-48 65-88943-42
65-88943-25 (a) 65-88943-49 65-88943-43
65-88943-26 (a) 65-88943-50 65-88943-44
65-88943-27 (a) 65-88943-51 65-88943-45
65-88943-31 (a) 65-88943-51 65-88943-46
65-88943-32 (a) 65-88943-52 65-88943-47
(a) Existing Kits 65 88943-24, -25, -26, -27, -31, and -32 may be reworked by removing the
doublers from the applicable skin assembly, salvaging the skin by removing residual faying
surface sealant, and installing new doublers from applicable supplemental kits during
installation of skin panels on airplane. The two seal retainers and valve assemblies installed
in the region of the doublers are to be salvaged and re-installed. Supplemental kits also
include 5/16 inch diameter protruding head fasteners to be installed in keel beam splice
area.
Feb 8/74 737-53A1042
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BOEING SERVICE BULLETIN 737-53A1042
B. Parts Necessary to Modify Spares
None
C. Special Tools and Equipment
An eddy current instrument and reference standard to determine corrosion damage as described in
Boeing Nondestructive Test Manual, D6-37239, Part 6, Subject 51-00-00, Figure 5.
D. Existing Parts Accountability
None
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BOEING SERVICE BULLETIN 737-53A1042
III. ACCOMPLISHMENT INSTRUCTIONS
NOTES: 1. The paragraphs identified with letters give the general work instructions and the necessary
tests.
2. The work instructions are divided into tasks. Man-hours and elapsed time for each task
are given in Paragraph I.E., Manpower. Each task can be done independently.
3. Unless specified differently, these dimensions and tolerances are used:
- All linear dimensions are in inches
- Tolerance on linear dimensions other than rivet and bolt edge margin 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
- The hole dimensions for standard solid rivets are found in 737 Structural Repair
Manual Chapter 51
- The torque limits to tighten nuts and bolts are found in 737 Structural Repair Manual
Chapter 51
4. As recommended by the 737 Aging Fleet Structures Working Group, accomplish the
modification per this service bulletin, Part V of the Accomplishment Instructions prior to, or
upon the accumulation of 75,000 flight cycles, or 20 years airframe age, whichever occurs
first.
5. Accomplish the instructions specified in D6-38528 "Corrosion Prevention and Control
Program" after the skin panels are replaced.
6. Repairs per Parts III and IV require continued inspection and application of corrosion
inhibitor at two year intervals until panel replacement is accomplished per Part V.
7. To prevent injury to persons or damage to airplane or equipment, make sure you do the
instructions of all warning and cautions as given in the specified manual sections.
The following instructions are divided into five parts.
o Part I - Inspection
o Part II - Interim Repair
o Part III - Delamination Repair
o Part IV - Corrosion Repair
o Part V - Panel Replacement
Feb 8/74 737-53A1042
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BOEING SERVICE BULLETIN 737-53A1042
Illustration Table of Contents
Title Page
Figure 1. Skin Panel Location 27
Figure 2. Delamination Repair 29
Figure 3. Corrosion Repair 34
Figure 4. Jacking 36
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BOEING SERVICE BULLETIN 737-53A1042
PART I - INSPECTION
External Inspection
1. Remove wing to body fairings or gain access to external surface of body skin panels in area covered
by fairings.
NOTE: Access beneath the fairings may be gained by removing the fasteners in the lower portion of
the fairing up to approximately Stringer 24. The fairing can then be pried down
approximately two inches, permitting inspection along Stringer 25 and 26 with the aid of a
mirror and flashlight. If skin damage is observed, the fairing must be removed.
2. Visually inspect external surface of skin panels between BS 360 and 540 and Stringers 26L and 26R,
and between BS 727 and 1016 and Stringers 25L and 25R. Also inspect the skin lap joints at the
edges of the affected areas. Inspect for bulges in the skin, skin cracks adjacent to fastener heads,
and "dished" or missing fastener heads.
NOTE: On Group 2 airplane PK067 only, inspection is not required between BS 360 and 540 and
Stringers 26L and 26R.
3. If no bulges, cracks, "dished" or missing fastener heads are found and internal inspection is not
being done in conjunction with the external inspection, restore wing to body fairings and continue
inspection at specified intervals. If internal inspection is being done, restore fairings upon completion
of both inspections.
4. If cracks or missing fastener heads are found, repair before further flight. Part II describes an interim
repair that can be accomplished on any affected airplane to defer entry to the inner surface of the
skin panel, if internal inspection is not being done in conjunction with the external inspection. Parts
III and IV describe complete repairs for Group 1 airplanes. Contact Boeing for complete repair for
Group 2 airplanes.
5. If skin bulging is found, with or without "dished" fastener heads, measure length of each bulge and
distance between bulges. If within the following limits, reinspect per Step 6. If beyond limits, inspect
per Steps 7, 8, and 9:
(a) Each bulge should not exceed 10.0 inches in length.
(b) Nearest ends of any two bulges along the same stringer, or the same frame, or on a stringer and
an intersecting frame, should not be closer than 24.0 inches, except any two bulges within the
foregoing limits that are located on two adjacent stringers, or on two adjacent frames, are
acceptable even though the distance between the two bulges is less than 24.00 inches.
6. Visually inspect for bulge enlargement, skin cracks and missing fastener heads at one month
intervals. If bulge has enlarged beyond limits, eddy current inspect per Step 7. If skin has cracked
or fastener heads are missing, repair before further flight.
7. If skin bulges exceed limits in Step 5, inspect for skin thickness reduction caused by internal
corrosion at the affected area and for cracks in the skin inner surface at the affected fasteners. Use
low frequency eddy current inspection (Ref. Boeing Nondestructive Test Manual D6-37239, Part 6,
Subject 51-00-00, Figure 5) or operator's comparable procedure.
Feb 8/74 737-53A1042
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BOEING SERVICE BULLETIN 737-53A1042
8. If skin thickness loss exceeds 10% of normal skin thickness of 0.036 inch, or if indication of a crack is
found in the skin inner surface, repair before further flight.
9. If skin thickness loss is 10% or less, and no indication of a crack in the skin inner surface is found,
reinspect per Step 7 above, the affected area externally at three month intervals for corrosion
progression and crack initiation. If either is found, repair before further flight.
Internal Inspection
10. Remove cargo compartment floor panels, interior panels and insulation blankets to expose the inner
surfaces of the skin panels, stringers and frames between BS 360 and 540 and Stringers 26L and
26R, and between BS 727 and 1016 and Stringers 25L and 25R. Clean the inner surface of the
internal doubler on all affected airplanes and the exposed inner surface of the skin at the chem milled
openings in the doubler on Group 1 airplanes. Also remove all removable remains of any bond
adhesive from the inner surface of the skin at the chem milled openings in the doubler.
NOTE: On Group 2 airplanes PK067 only, inspection is not required between BS 360 and 540 and
Stringers 26L and 26R.
11. With the aid of a bright light, accomplish a close visual inspection of the internal surface of the
internal doubler on all affected airplanes and the exposed internal areas of the skin on Group 1
airplanes. Inspect for corrosion and cracks in the inner surfaces and for missing fastener heads.
Also inspect for bulges in the doubler, indicating corrosion between the skin and doubler and bond
separation.
12. On Group 1 airplanes, also inspect for indication of skin to doubler bond separation around the edge
of the chem milled openings in the internal doubler. Give particular attention to areas where skin
bulging and "dished" or missing fastener heads were found by the external inspection. Separation is
often indicated by a thin black line on the skin at the edge of the doubler opening. Also check
suspect area by inserting a feeler gage between the skin and doubler while pushing outwards on the
skin to further separated the skin and doubler.
13. On all affected airplanes on which skin thickness loss from corrosion was found on the inner surface
of the skin during external inspection, also inspect for doubler thickness loss and cracks on the outer
surface of the doubler in the affected area, if affected area is covered by a doubler. Use low
frequency eddy current inspection (Ref. Boeing Nondestructive Test Manual D6-37239, Part 6,
Subject 51-00-00, Figure 5) or operator's comparable procedure.
14. If corrosion is found in the internal surface of the doubler, or in the internal surface of the skin on a
Group 1 airplane where the skin is exposed, blend out the corrosion, If blendout depth does not
exceed 0.004 inch, apply chemical film treatment (Alodine or Iridite) and one coat of chemical and
solvent resistant primer and one coat of enamel. If blendout depth exceeds 0.004 inch, install a
repair similar to that shown in 737 Structural Repair Manual Subject 53-30-3.
15. On Group 1 airplanes, if skin thickness loss of 10% or less has been found in the inner surface of the
skin only, in area covered by the internal doubler, repair per Part III - Delamination Repair to extend
the external inspection of the affected area to two year intervals. If doubler thickness loss of 10% or
less in the external surface of the doubler has been found in the same location, repair per Part III and
externally inspect affected area at intervals of two years. If thickness loss in either the skin or
doubler, or both, is greater than 10%, repair per Part IV - Corrosion Repair to extend both
inspections of the affected area to two year intervals.
If corrosion between the skin and doubler, or delamination, is found on a Group 2 airplane, contact
Boeing for instructions.
16. If cracks are found by either the external or internal inspection, repair per Part IV.
Feb 8/74 737-53A1042
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BOEING SERVICE BULLETIN 737-53A1042
17. Upon completion of internal inspection, or after repair is completed, apply a saturation coating of
corrosion inhibitor BMS 3-23 to all internal surfaces of the inspection area, using an airless spray gun
operation at low pressure (45 psi) (Ref. 737 Structural Repair Manual Subject 51-10-2).
18. Restore external and internal inspection areas to normal operating configuration and continue repeat
inspection at scheduled intervals, until skins are replaced with solid panels per Part V - Skin Panel
Replacement.
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BOEING SERVICE BULLETIN 737-53A1042
PART II - INTERIM REPAIR - ALL AFFECTED AIRPLANES
If repair is required as a result of the external inspection, the following interim repair may be used to
defer the need for internal inspection and complete repair. The interim repair must be replaced by the
complete repair within one year after installation or at the first internal inspection, whichever comes first.
See Part III or Part IV for complete repair on Group 1 airplanes. Contact Boeing for complete repair
instructions on Group 2 airplanes.
1. Remove fasteners in area to be repaired but do not trim out damaged area. Using pressure
equipment such as an airless spray pump with a tubular nozzle, inject corrosion inhibitor BMS 3-23
between the skin and doubler at all fastener holes. Saturate area as thoroughly as possible.
2. Install external repair doubler over affected area per 737 Structural Repair Manual Subject 53-30-3,
picking up all existing fastener locations in the area and adding fasteners per the Structural Repair
Manual. Blind fasteners may be used at all locations.
3. Outer three rows of fasteners attaching the external doubler must be located in outer skin which has
not lost more than 10% thickness from corrosion. Skin thickness loss should be checked per Step 7
28 of Part I Inspection.
4. Repair doubler must extend from frame to frame and stringer to stringer and must not end on a bulge
in the skin.
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BOEING SERVICE BULLETIN 737-53A1042
FIGURE 1. SKIN PANEL LOCATION
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BOEING SERVICE BULLETIN 737-53A1042
PART III - DELAMINATION REPAIR - GROUP 1 AIRPLANES
The delamination repair shown in Figure 2 encompasses the repair of four basic delamination areas.
These areas are; delamination of the longitudinal strap area under a stringer, delamination of the
circumferential strap area between frames, delamination of the circumferential strap area under a
frame, and delamination of a large doubler area located between stringers and frames. The area
repairs may be used individually or in any combination as required to suit a particular situation. These
repairs should be installed per the following general instructions:
1. Remove existing fasteners designated A in the delaminated area detected during inspection, and
from the surrounding area as required to determine the true extent of the delamination. With
fasteners removed, the extent of the delaminated area is determined by separating skin and doubler
by hand until a strong bond is located. After the extremities of the delamination have been located,
remove a minimum of three additional fastener rows beyond the extremities in all directions.
NOTE: Remove fillet seal along doubler edge, if present, in all areas of confirmed or suspected
delamination to aid in determining delamination extremities.
2. Enlarge existing fastener holes or drill new fastener holes as indicated by the following symbols. See
Figure 2 for applicable fastener pattern in delamination area.
The instructions given below agree with the letter shown in the upper left corner of the fastener
symbols in the figure. A number in the lower right corner gives the grip length of the fastener.
A. Enlarge existing 5/32 inch diameter fastener hole with a No. 2 (0.221 inch diameter) drill, but do
not countersink.
Enlarge existing 3/16 inch diameter fastener hole with a size F (0.257 inch diameter) drill, but do
not countersink.
B. Locate and drill No. 21 (0.159 inch diameter) hole. Do not countersink.
3. Place aluminum foil tape, or equivalent, on the skin exterior surface over the enlarged or newly
drilled holes.
4. Carefully separate skin and doubler at doubler edge using thin non metallic wedges.
5. Using pressure equipment such as an airless paint spray pump with a tubular nozzle, inject organic
corrosion inhibiting compound under pressure between skin and doubler at doubler edge and
fastener holes. Saturate delaminated area as thoroughly as possible.
6. Remove wedges and aluminum foil tape and install the following fasteners:
The instructions given below agree with the letter shown in the upper left corner of the fastener
symbols in the figure. A number in the lower right corner gives the grip length of the fastener.
A. Install Rivet BACR15ET7D( ) where No. 2 hole was drilled.
Install Rivet MS20470D8-( ) or BACR15BB8D( ) where size F hole was drilled.
B. Install Rivet MS20470D5-( ) or BACR15BB5D( ).
7. Apply organic corrosion inhibiting compound per operator's standard procedure (Ref. 737 Structural
Repair Manual Subject 51-10-2) to internal side of skin, doubler, frames and stringers in repair area.
Feb 8/74 737-53A1042
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BOEING SERVICE BULLETIN 737-53A1042
FIGURE 2. DELAMINATION REPAIR
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BOEING SERVICE BULLETIN 737-53A1042
PART IV - CORROSION REPAIR - GROUP 1 AIRPLANES
Three basic repairs are shown in Figure 3. These repairs are for a corroded circumferential strap under
a frame, a circumferential strap between frames and corroded skin, and remaining doubler areas.
These repairs should be accomplished as follows:
NOTE: If extensive corrosion is detected, the operator may decide to replace the entire bonded skin
panel with a preferred, solid panel per Part V.
Circumferential Strap Repair Under Frame
This repair is applicable to strap areas of the doubler where corrosion damage exceeds 0.004 inch and
is located between the ends of the frame shear tie. This repair should not be used if corrosion damage
in excess of 0.004 inch in the strap extends beyond the end of the frame shear tie, or if skin corrosion
damage under the strap is in excess of 0.004 inch. For repair of corrosion beyond these limits, see
Skin and Doubler Repair. Accomplish strap repair under frame as follows:
NOTE: Delamination repair per Part III should be accomplished simultaneously with this repair in the
area adjacent to the repair.
1. Remove existing fastener designated, A.
2. Cut strap at each end of shear tie. See Figure 3. Apply chemical film treatment (Alodine or Iridite)
and one coat of chemical and solvent resistant primer (Ref. BMS 10-11, Type I) to raw edges.
3. Blend out any corrosion on skin per operator's standard procedure and apply chemical film treatment
(Alodine or Iridite), one coat of chemical and solvent resistant primer (Ref. BMS 10-11, Type I) and
one coat of gloss polyurethane enamel (Ref. BMS 10-60, Type I).
4. Fabricate repair strap from 0.040 or 0.050 inch thick clad 2024-T3 sheet per QQ-A-250/5. Fabricate
filler same width as repair strap and same length as shear tie from 0.036 inch thick clad 2024-T3
sheet per QQ-A-250/5. Apply chemical film treatment (Alodine or Iridite) and one coat of chemical
and solvent resistant primer (Ref. BMS 10-11, Type I) to strap and filler.
5. Drill the following fastener holes in repair strap, skin and filler:
The instructions given below agree with the letter shown in the upper left corner of the fastener
symbols in the figure. A number in the lower right corner gives the grip length of the fastener.
A. Drill No. 2 (0.221 inch diameter) hole if existing hole in structure is 5/32 inch diameter. Do not
countersink.
Drill a size F (0.257 inch diameter) hole if existing hole in structure is 3/16 inch diameter. Do not
countersink.
B. Locate and drill No. 21 (0.159 inch diameter) hole. Do not countersink.
6. Inject organic corrosion inhibiting compound under remaining ends of previously cut strap per Part III.
7. Remove corrosion inhibiting compound from body skin in repair area per operator's standard
procedure (Ref. 737 Structural Repair Manual Subject 51-10-2).
8. Apply sealant (BMS 5-95, Class C) to faying surfaces of repair strap, body skin, filler and shear tie
and install repair strap and filler using the following fasteners:
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BOEING SERVICE BULLETIN 737-53A1042
The instructions given below agree with the letter shown in the upper left corner of the fastener
symbols in the figure. A number in the lower right corner gives the grip length of the fastener.
A. Install Rivet BACR15ET7D( ) where No. 2 hole was drilled.
Install Rivet MS20470D8-( ) or BACR15BB8D( ) where size F hole was drilled.
B. Install Rivet MS20470D5-( ) or BACR15BB5D( ).
9. Apply corrosion inhibiting compound per operator's standard procedure (Ref. 737 Structural Repair
Manual Subject 51-10-2) to internal side of skin, frames and stringers in repair area.
10. Paint exterior of repair strap to match surrounding area.
Circumferential Strap Repair Between Frames
This repair is applicable to strap areas of the doubler located between frames and stringers where
corrosion damage in the strap exceeds 0.004 inch and is not closer than 1.5 inch from the fastener
common to the stringer. This repair should not be used if corrosion damage in excess of 0.004 inch in
the strap is closer than 1.5 inch from stringer fasteners, or if skin corrosion damage under the strap
exceeds 0.004 inch. For repair of corrosion beyond these limits, see Skin and Doubler Repair.
Accomplish strap repair between stringers and frames as follows:
NOTE: Delamination repair per Part III should be accomplished simultaneously with this repair in the
area adjacent to the repair.
1. Remove existing fastener designated, A.
2. Cut strap 1.50 inch from fasteners in stringer. See Figure 3. Apply chemical film treatment (Alodine
or Iridite) and one coat of chemical and solvent resistant primer (Ref. BMS 10-11, Type I) to raw
edges.
3. Blend out any corrosion on skin per operator's standard procedure and apply chemical film treatment
(Alodine or Iridite) and one coat of chemical and solvent resistant primer (Ref. BMS 10-11, Type I)
and one coat of gloss polyurethane enamel (Ref. BMS 10-60, Type I).
4. Fabricate repair strap from 0.040 or 0.050 inch thick clad 2024-T3 sheet per QQ-A-250/5. Apply
chemical film treatment (Alodine or Iridite) and one coat of chemical and solvent resistant primer
(Ref. BMS 10-11, Type I) to repair strap.
5. Drill the followng fastener holes in repair strap skin.
The instructions given below agree with the letter shown in the upper left corner of the fastener
symbols in the figure. A number in the lower right corner gives the grip length of the fastener.
A. Drill No. 2 (0.221 inch diameter) hole. Do not countersink.
B. Locate and drill No. 21 (0.159 inch diameter) hole. Do not countersink.
6. Inject organic corrosion inhibiting compound under remaining ends of previously cut strap per Part III.
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BOEING SERVICE BULLETIN 737-53A1042
7. Apply sealant BMS 5-95, Class C, to faying surface of skin and repair strap and install repair strap,
using the following fasteners.
The instructions given below agree with the letter shown in the upper left corner of the fastener
symbols in the figure. A number in the lower right corner gives the grip length of the fastener.
A. Install Rivet BACR15ET7D( ).
B. Install Rivet MS20470D5-( ) or BACR15BB5D( ).
8. Apply corrosion inhibiting compound per operator's procedure (Ref. 737 Structural Repair Manual
Subject 51-10-2) to internal side of skin, stringers and frames in repair area.
9. Paint exterior of repair strap to match surrounding area.
Skin and Doubler Repair
This repair is applicable to strap areas under stringers and large doubler area where corrosion damage
exceeds 0.004 inch, and to skin area with corrosion damage in excess of 0.004 inch.
NOTE: Delamination repair per Part III should be accomplished simultaneously with this repair in the
area adjacent to the repair.
1. Remove existing fastener designated, A . See Figure 3.
2. Cut away skin and doubler in corroded area. Apply chemical film treatment (Alodine or Iridite) and
one coat of chemical and solvent resistant primer (Ref. BMS 10-11, Type I) to raw edges.
3. Fabricate repair doubler and fillers as required from 0.071 inch thick clad 2024-T3 sheet per
QQ-A-250/5. Apply chemical film treatment (Alodine of Iridite) and one coat of chemical and solvent
resistant primer (Ref. BMS 10-11, Type I) to repair doubler and fillers.
NOTE: If repair doubler will cross circumferential strap area, that portion of the doubler crossing the
straps must terminate at a stringer as shown in the upper portion of the repair in Figure 3.
Alternatively, the entire doubler edge may terminate at a stringer as shown in the lower
portion of the repair.
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BOEING SERVICE BULLETIN 737-53A1042
4. Drill the following fastener holes in repair doubler fillers and existing structures:
The instructions given below agree with the letter shown in the upper left corner of the fastener
symbols in the figure. A number in the lower right corner gives the grip length of the fastener.
A. Drill No. 2 (0.221 inch diameter) hole if existing hole in structure is 5/32 inch diameter. Do not
countersink.
Drill a size F (0.257 inch diameter) hole if existing hole in structure is 3/16 inch diameter. Do not
countersink.
B. Locate and drill No. 11 (0.191 inch diameter) hole.
C. Locate and drill No. 21 (0.159 inch diameter) hole.
5. Inject organic corrosion inhibiting compound under edges of previously cut doubler per Part II.
6. Apply sealant BMS 5-95, Class C, to faying surface of repair doubler, skin, fillers, stringers and
frames after removing all traces of corrosion inhibiting compound per operator's standard procedure
(Ref. 737 Structural Repair Manual Subject 51-10-2).
7. Install repair doubler and fillers using the following fasteners:
The instructions given below agree with the letter shown in the upper left corner of the fastener
symbols in the figure. A number in the lower right corner gives the grip length of the fastener.
A. Install Rivet BACR15ET7D( ) where No. 2 hole was drilled.
Install Rivet MS20470D8-( ) or BACR15BB8D( ) where size F hole was drilled.
B. Install Rivet MS20470D6-( ) or BACR15BB6D( ).
C. Install Rivet MS20470D5-( ) or BACR15BB5D( ) or BACR15CE5D( ).
8. Apply corrosion inhibiting compound per operator's standard procedure (Ref. 737 Structural Repair
Manual Subject 51-10-2) to internal side of repair doubler, skin, stringers and frames in repair area.
9. Paint external side of repair doubler to match surrounding area.
Feb 8/74 737-53A1042
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### Page 38

BOEING SERVICE BULLETIN 737-53A1042
FIGURE 3. CORROSION REPAIR
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### Page 39

BOEING SERVICE BULLETIN 737-53A1042
Part V SKIN PANEL REPLACEMENT
1. Defuel the airplane per operator's standard procedure.
2. Support the airplane per Table II.
CAUTION: EXCEPT AS NOTED, OBSERVE ALL OPERATING PROCEDURES, CAUTIONS AND
LIMITATIONS OF MAINTENANCE MANUAL SUBJECT 7-11-11.
a. Jack the airplane at points "A", "B", and "C" and install stabilizer jack at point "D" per 737
Maintenance Manual Subject 7-11-11.
b. Install jacks at main gear points "F".
c. Adjust jacks symmetrically as required to obtain loads at forward and aft body jacks (points "C"
and "D") as specified in Table II.
NOTE: Loads for the wing and main gear jacks are approximate and will vary with airplane model
and weight. Use these jacks to balance the airplane while obtaining the specified loads
on the forward and aft body jacks. Loads on the main gear jacks need not be monitored
since maximum allowable loads at these points cannot be exceeded in this configuration.
3. Remove wing to body fairing, cargo compartment floor panels, cargo compartment removable
bulkheads and insulating blankets as necessary to gain access to interior and exterior surfaces of
bonded skin panel to be replaced.
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BOEING SERVICE BULLETIN 737-53A1042
TABLE 2 - Jack Loads
Jack Location Jack Loads - Pounds
A and B (Wing) 3,000 to 10,000 each (a)
C (Aft Body) 9,000 (+ or -100)
D (Fwd Body) 11,000 (+ or 100)
F (Main Gear) 10,000 to 17,000 each (a)
(a) Wing and main gear jack loads are approximate and are
to be adjusted as required to obtain specified loads at
forward and aft body jacks.
FIGURE 4. JACKING
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BOEING SERVICE BULLETIN 737-53A1042
4. Replace skin panel as follows:
NOTES: 1. If multiple skin panel replacement is required, to minimize possible misalignment it is
recommended that panels not be replaced simultaneously but that all attaching
fasteners for the first panel be installed prior to removal of the second panel.
2. The following steps supplement detailed information shown on skin panel replacement
Drawings 65-88942 for forward body of 737-100 airplanes, 65-88939 for forward body of
737-200 airplanes and 65-88943 for aft body of both 737-100 and -200 airplanes.
3. 3. Refer to Boeing Standard Overhaul Practices Manual 20-41-01 for definition of finish
codes specified on reference drawings.
a. Remove antennas, doors and cover plates, pressure relief valves, drain plugs and any other
applicable item to be salvaged from the installed panel.
b. Remove stringer splice members where specified to gain access to fasteners common to skin and
stringer.
c. Remove all fasteners attaching skin panel to structure, up to those common to the lap joints.
Exercise care to avoid damaging fastener holes.
d. Support skin panel and remove all fasteners in lap joints, and those additional designated
fasteners above the lap joints. Exercise care to avoid damaging fastener holes. Do not oversize
lapjoint holes prior to high frequency eddy current inspection. For high frequency inspection and
rework instructions at lapjoint, see Service Bulletin 737-53A1039. Separate bonded lap joints per
Structural Repair Manual Subject 51-40-5 and remove existing skin panel.
e. Drill drain holes in stringer where specified.
f. Remove loose adhesive from lap joint outer skin faying surface and remove any corrosion per
corrosion Prevention Manual, Part III, Subject 53-30-37.
g. Locate the skin panel and doubler(s) in position.
h. Drill fastener holes for attaching doubler(s) to skin and skin to body structure.
i. Mark lower edge of lap joints and boundary of area to be covered by fairing on new skin and
remove skin and doubler(s).
j. Clean doubler(s), skin and body structure (frames, stringer, etc.) faying surfaces.
k. Apply chemical film treatment (Alodine or Iridite) and one coat of epoxy primer (Ref. BMS 10-11,
Type I) to lap joint faying surfaces, area of new skin panel to be covered by fairing, if not already
primed, and all other interior bare areas.
l. Install doubler(s) on skin with faying surface sealant, BMS 5-95, Type C (preferred) or BMS 5-79,
Type B or C and field rivet in position.
m. Apply faying surface sealant BMS 5-95, Type C (preferred) or BMS 5-79, Type B or C to body
structure (frames, stringers, etc.) and to lap joint faying surfaces and install skin panel.
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BOEING SERVICE BULLETIN 737-53A1042
n. Install all fasteners common to new skin and above the lap joints.
NOTES: 1. All fasteners must be installed prior to sealant reaching the tack free condition.
2. Install all non-aluminum countersunk permanent fasteners in holes wet with sealant or
wet with epoxy primer (Ref. BMS10-11, Type I). Install all non-aluminum countersunk
removable fasteners in holes epoxy primed and allowed to dry.
3. Install all fairing attaching hardware, parts required for corrosion repair and salvaged
parts simultaneously with skin attaching fasteners.
4. Install protruding head fasteners in keel beam splice area (BS 727 + 17.0, S-27R and
S-27L) per Drawing 65-88943.
o. Reinstall any stringer splice members previously removed.
p. Drill drain holes and make any other required cutouts in the skin. Do not install drain valves or
other equipment on interior of skin at this time.
q. Restore pressure sealant as required.
r. Apply an additional coat of epoxy primer (Ref. BMS 10-11, Type I) to inner surface of new skin
panel, followed by one coat of gloss polyurethane enamel (Ref. BMS 10-60, Type I).
s. Install antennas, doors and cover plates, drain valves, pressure relief valve and any other
applicable salvaged items as specified on reference drawing.
NOTE: Check operation of door latches and adjust as necessary (Ref. Maintenance Manual
Subject 12-32-11).
5. Lower the airplane as follows:
a. Station a man at each jack location to monitor the load to ensure maximum allowable jack loads
are not exceeded.
b. Remove the jack from the forward body jack point first, remove jacks from main gears, then lower
the airplane and remove remaining jacks per operator's procedures (Ref. 737 Maintenance
Manual Subject 7-11-11).
6. Paint exterior of new panel, if and as required, to match existing color scheme.
7. Apply organic corrosion inhibiting compound to interior of new skin, stringers and frames and to
exterior of skin where covered by wing to body fairing.
8. Install insulating blankets, bulkheads, floor panels and wing to body fairing previously removed to
provide access.
Feb 8/74 737-53A1042
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### Page 43

Commercial
Airplane
Group
737
Service Bulletin
Number: 737-53A1042 Evaluation FormDate: February 8,1974
Revision 9: July 25, 1991
ATA System: 5331
Prepared By: Pat McGee
SUBJECT: FUSELAGE - LOWER LOBE HOT-BONDED SKIN PANEL INSPECTION, REPAIR, AND
PANEL REPLACEMENT
Use this evaluation form to tell us what you think of the quality of this service bulletin. We will use the
data that you give us to correct any errors in this bulletin and to improve the quality of new service
bulletins.
NOTE: Please do not use this evaluation form to tell us to make changes to your maintenance or
repair manuals. To make these changes, please use a Publication Change Request (PCR)
form.
Give the completed evaluation form to your Boeing Field Service Representative or send the evaluation
form directly to this address:
R.G. Kelsey
Manager
Service Bulletin Engineering
Boeing Commercial Airplane Group
P.O. Box 3707, Mail Stop 2L-02
Seattle, WA 98124-2207
Please give us the following data:
OPERATOR: ____________________________________ TODAY'S DATE: _______________
PREPARED BY: _________________________________ TITLE: _______________________
ORGANIZATION: _________________________________ TELEX CODE: ________________
TELEPHONE NUMBER: ___________________________________________________________
Please tell us about the quality of this service bulletin in the areas shown below:
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If you have additional comments please use the other side. Thank you for taking the time to complete
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