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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
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