### Commercial Airplane Group 

# 737 Service Bulletin

Number: 737-53A1042 

## Revision Transmittal Sheet 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

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

### Commercial Airplane Group 

# 737 Service Bulletin

Number: 737-53A1042 

## Summary 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

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

### BOEING SERVICE BULLETIN 737-53A1042

Feb 8/74 REV. 9: Jul 25/91 Summary Page 2 of 2

### 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

### 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

### 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

### 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

### 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

### 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

### 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

### 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

### 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 REV. 9: Jul 25/91 9

### 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 REV. 9: Jul 25/91 10

### 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 REV. 9: Jul 25/91 11

### 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 DateJuly 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

Feb 8/74 737-53A1042 REV. 9: Jul 25/91 13

### 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

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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.

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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.

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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

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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

PARTI

-INSPECTION
ExternalInspection 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.

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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. InternalInspection 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.

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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

PARTII

-INTERIMREPAIR

-ALLAFFECTEDAIRPLANES 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

PARTIII

-DELAMINATIONREPAIR

-GROUP1AIRPLANES 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 designatedAin 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.

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### BOEING SERVICE BULLETIN 737-53A1042

FIGURE 2. DELAMINATION REPAIR

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### BOEING SERVICE BULLETIN 737-53A1042

PARTIV

-CORROSIONREPAIR

-GROUP1AIRPLANES 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. CircumferentialStrapRepairUnderFrame 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.

CircumferentialStrapRepairBetweenFrames 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.

SkinandDoublerRepair 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 REV. 9: Jul 25/91 33

### BOEING SERVICE BULLETIN 737-53A1042

FIGURE 3. CORROSION REPAIR

Feb 8/74 737-53A1042 REV. 9: Jul 25/91 34

### 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.

Feb 8/74 737-53A1042 REV. 9: Jul 25/91 35

### 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 REV. 9: Jul 25/91 38

### Commercial Airplane Group 

# 737 Service Bulletin

Number: 737-53A1042 

## Evaluation Form Date: 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: ___________________________________________________________
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