# Boeing Service Bulletin A3537: No revision named

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- Document: [Boeing Service Bulletin A3537](https://openairdocs.org/service-documents/boeing/a3537.md)
- Title as filed: U.S. DOT/FAA - Service Information
- Pages: 36
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## Text

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### Page 1

Commercial 
Airplanes
707
Service Bulletin
ALERT
Number: A3537
Original Issue: January 30, 2012
ATA System: 5410
SUBJECT: NACELLE - Inboard and Outboard Nacelle Strut Midspar Fitting - Inspection
Export of this technology is controlled under the United States Export Administration Regulations (EAR) (15
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9E991ECCN:
BOEING PROPRIETARY, CONFIDENTIAL, AND/OR TRADE SECRET
Copyright © 2012 The Boeing Company
Unpublished Work - All Rights Reserved
Boeing claims copyright in each page of this document only to the extent that the page contains copyrightable
subject matter. Boeing also claims copyright in this document as a compilation and/or collective work.
This document includes proprietary information owned by The Boeing Company and/or one or more third parties.
Treatment of the document and the information it contains is governed by contract with Boeing. For more
information, contact The Boeing Company, P.O. Box 3707, Seattle, Washington 98124.
Boeing, the Boeing signature, the Boeing symbol, 707, 717, 727, 737, 747, 757, 767, 777, 787, Dreamliner,
BBJ, DC-8, DC-9, DC-10, KC-10, KDC-10, MD-10, MD-11, MD-80, MD-88, MD-90, P-8A, Poseidon and the
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Table of Contents
Summary ...................................................... 5
1. PLANNING INFORMATION ........................................ 9
A. Effectivity ................................................ 9
1. Airplanes ............................................. 9
2. Spares Affected ........................................ 1 3
B. Concurrent Requirements ...................................... 1 3
C. Reason ................................................ 1 3
D. Description .............................................. 1 4
E. Compliance .............................................. 1 4
F. Approval ............................................... 1 6
G. Manpower .............................................. 1 7
H. Weight and Balance Changes .................................... 1 7
I. Electrical Load Data ......................................... 1 7
J. References .............................................. 1 7
1. Existing Data .......................................... 1 7
2. Data supplied with this Service Bulletin ............................ 1 7
3. Installation Drawings Used in the Preparation of this Service Bulletin ............ 1 8
K. Publications Affected ........................................ 1 8
L. Interchangeability and Intermixability of Parts ........................... 1 8
2. MATERIAL INFORMATION ........................................ 1 9
A. Material - Price and Availability ................................... 1 9
B. Industry Support Information .................................... 1 9
C. Parts Necessary For Each Airplane ................................. 1 9
1. Kits/Parts ............................................ 1 9
2. Parts and Materials Supplied by the Operator ........................ 1 9
3. Parts Modified and Reidentified ................................ 1 9
4. Parts Removed and Not Replaced .............................. 1 9
D. Parts Necessary to Change Spares ................................. 1 9
E. Special Tooling - Price and Availability ............................... 1 9
F. Special Tooling Necessary to do this Service Bulletin ....................... 1 9
3. ACCOMPLISHMENT INSTRUCTIONS .................................. 2 1
A. GENERAL INFORMATION ..................................... 2 1
B. WORK INSTRUCTIONS ....................................... 2 2
FIGURE 1: NACELLE STRUT AND SAILBOAT FAIRING DROOP STRIPE APPLICATION ...... 2 4
FIGURE 2: NACELLE STRUT DROOP .................................. 2 6
FIGURE 3: ENGINE NUMBER 2 AND ENGINE NUMBER 3 NACELLE STRUT MIDSPAR FITTING
INSPECTION .......................................... 2 8
FIGURE 4: ENGINE NUMBER 2 AND ENGINE NUMBER 3 NACELLE STRUT MIDSPAR FITTINGS HFEC
INSPECTION .......................................... 3 1
FIGURE 5: ENGINE NUMBER 2 AND ENGINE NUMBER 3 NACELLE STRUT FAIRING AND PANEL
INSTALLATION ......................................... 3 5
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Commercial 
Airplanes
707
Service Bulletin
ALERT
SummaryNumber: A3537Original Issue: January 30, 2012
ATA System: 5410
SUBJECT: NACELLE - Inboard and Outboard Nacelle Strut Midspar Fitting - Inspection
THIS BULLETIN IS SENT TO THE OPERATORS OF RECORD OF THE AIRPLANES SHOWN IN PARAGRAPH
1.A., EFFECTIVITY. IF AN AIRPLANE HAS BEEN LEASED OR SOLD, SEND THIS SERVICE BULLETIN TO
THE NEW OPERATOR. IF APPLICABLE SPARES HAVE BEEN SOLD, SEND THIS SERVICE BULLETIN TO
THE NEW OWNER.
CONCURRENT REQUIREMENTS
None.
BACKGROUND
Accomplishment of the inspections in this service bulletin will make sure that an engine number 1, 2, 3, or 4
nacelle strut has not drooped from its normal position and that the correct inboard and outboard midspar fittings
are installed on the engine number 2 and 3 nacelle struts. A drooped nacelle strut indicates that a midspar fitting
may have fractured. If an incorrect midspar fitting is installed, a fatigue crack can occur which can cause a
fracture of a midspar fitting. A fractured midspar fitting can result in a separation of the nacelle strut and engine
from the airplane in flight which could preclude safe flight.
Operators have reported more than 45 of the midspar fittings with the 0.38 inch tang transition, cracked on more
than 40 airplanes with approximately 9,900 to 63,000 flight hours. There have been several events where the
engine and nacelle strut has separated from the airplane. In one instance, the engine number 3 nacelle strut
separated from the airplane and contacted the engine number 4 nacelle strut, which also separated from the
airplane.
This service bulletin gives instructions to inspect for the correct engine number 2 and 3 nacelle strut midspar
fittings, apply a droop stripe and inspect the engine number 1, 2, 3, and 4 nacelle strut for droop.
Boeing Service Related Problem (SRP) 707-SRP-54-0105 is related to this service bulletin.
This table is provided to operators for planning purposes only. Refer to the applicable sections for more
information.
ReferenceAffectedPlanning Data
Paragraph 1.A.2., Spares AffectedNoSpares Affected
Paragraph 1.E., ComplianceYesAD Related
Paragraph 1.H., Weight and Balance ChangesNoWeight and Balance Change
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ReferenceAffectedPlanning Data
Paragraph 1.I., Electrical Load DataNoElectrical Load Changed
Paragraph 1.K., Publications AffectedNoPublications Affected
Paragraph 1.K., Publications AffectedNoAirplane Flight Operations Affected (Flight Crew
Operations Manual and/or FAA Approved Air-
plane Flight Manual)
Paragraph 2.C.1., Kits/PartsNoKits/Parts Required
Paragraph 2.C.2., Parts and Materials Supplied
by the Operator
YesOperator Supplied Material
Paragraph 2.F., Special Tooling Necessary to
do this Service Bulletin
NoSpecial Tooling Required
ACTION
Do a general visual inspection of the engine number 1, 2, 3, and 4 nacelle struts for droop below the normal
position. Make sure each nacelle strut has not drooped from its normal position. Apply a stripe to the inboard
and outboard side of the engine number 1, 2, 3, and 4 nacelle strut if it has not been previously accomplished.
If a nacelle strut is drooped below its normal position contact Boeing for further instructions and do the work as
instructed by Boeing.
Do a detailed inspection of the engine number 2 and engine number 3 nacelle strut inboard and outboard midspar
fittings to confirm the correct part is installed. If an incorrect part is found replace the part in accordance with
Boeing service bulletin 707-3183.
Do a HFEC inspection of the engine number 2 and engine number 3 nacelle strut inboard and outboard midspar
fittings, to look for cracks. If a crack indication is found contact Boeing for further instructions and do the work
as instructed by Boeing.
NOTE: You do not need to change the existing droop stripe, if the droop stripe was applied in accordance with
Boeing service bulletin 707-3377 requirements.
EFFECTIVITY
707-100, -100B, -200, -300, -300B, -300C, -400, 720, 720B Airplane(s). Refer to Paragraph 1.A.1., Airplanes,
for the list of affected airplane(s).
COMPLIANCE
The Federal Aviation Administration (FAA) will possibly release an Airworthiness Directive related to this service
bulletin. The Airworthiness Directive will make the compliance tasks and times given in this service bulletin
mandatory.
Refer to Paragraph 1.E., Compliance.
INDUSTRY SUPPORT INFORMATION
Boeing warranty remedies are not available for the inspection, and/or repair procedures given in this service
bulletin.
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MANPOWER
Elapsed HoursTotal Task HoursAirplanes
9.0018.00All Airplanes
MATERIAL INFORMATION
None.
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BOEING SERVICE BULLETIN A3537
ALERT  ALERT
NACELLE
STRUT #3  DO A GENERAL VISUAL INSPECTION OF
NACELLE  THE NACELLE STRUT TO MAKE SURE IT
STRUT #4  IS NOT DROOPED BELOW ITS NORMAL
POSITION AND APPLY STRIPE.
MAKE SURE THE NACELLE HAS NOT
DROOPED BELOW ITS NORMAL
POSITION.
→ D
NACELLE
NACELLE  STRUT #1
STRUT #2
DO A ONE TIME DETAILED INSPECTION
OF THE NUMBER 2 AND NUMBER 3
NACELLE STRUT MID SPAR FITTINGS
FOR CORRECT PART, AND HFEC
INSPECTION FOR CRACKS
2110700
Original Issue: January 30, 2012
A3537
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Commercial 
Airplanes
707
Service Bulletin
ALERT
Number: A3537
Original Issue: January 30, 2012
ATA System: 5410
SUBJECT: NACELLE - Inboard and Outboard Nacelle Strut Midspar Fitting - Inspection
THIS BULLETIN IS SENT TO THE OPERATORS OF RECORD OF THE AIRPLANES SHOWN IN PARAGRAPH
1.A., EFFECTIVITY. IF AN AIRPLANE HAS BEEN LEASED OR SOLD, SEND THIS SERVICE BULLETIN TO
THE NEW OPERATOR. IF APPLICABLE SPARES HAVE BEEN SOLD, SEND THIS SERVICE BULLETIN TO
THE NEW OWNER.
1.    PLANNING INFORMATION
A. Effectivity
1. Airplanes
This service bulletin is for the airplane(s) shown below.
Refer to Service Bulletin Index D6-1647 Part 3 for Airplane Variable Number, Line Number, and
Serial Number data.
DESCRIPTIONCONFIGURATIONGROUP
707-100, 707-100B, 707-200, 707-300, 707-300B, 707-300C,
707-400, 720, 720B Airplanes.
-1
Airplane Models:
707-100, 707-100B, 707-200, 707-300, 707-300B, 707-300C, 707-400, 720, 720B
GroupVariable Number
1B0001 - B0029
1B0101 - B0125
1B0201 - B0203
1B0301 - B0306
1B0401 - B0402
1B0501 - B0515
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GroupVariable Number
1B2001 - B2008
1B2091 - B2092
1B2101 - B2116
1B2191 - B2194
1B2199
1B2201 - B2227
1B2401 - B2403
1B2501 - B2502
1B2551 - B2553
1B2601 - B2608
100001 - 00006
100101 - 00156
100201 - 00205
100301 - 00305
100401 - 00451
100471 - 00475
100501 - 00513
100601 - 00602
100701 - 00703
102001 - 02020
102101 - 02121
102201 - 02207
102301 - 02303
102401 - 02418
104001 - 04005
104020 - 04022
104101 - 04106
104201 - 04218
104271 - 04272
104301 - 04303
105001 - 05060
105101 - 05138
105201 - 05208
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GroupVariable Number
105301 - 05312
105401
105601 - 05605
105631 - 05635
105701 - 05703
105801 - 05802
105821 - 05827
105831 - 05833
105851 - 05854
105891 - 05892
105921 - 05923
105941 - 05942
105961 - 05970
106001 - 06002
106101
106401 - 06404
106451
106461
107001 - 07017
107041 - 07059
107071 - 07081
107101 - 07109
107181
107191
107201 - 07215
107251 - 07271
107401 - 07407
107451 - 07458
107501 - 07504
107601 - 07626
107661 - 07662
107681 - 07684
107701 - 07702
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GroupVariable Number
107801 - 07821
107901 - 07907
108001 - 08008
108021
108051 - 08056
108071 - 08077
108101 - 08104
108121 - 08129
108141 - 08144
108151 - 08153
108171 - 08173
108191 - 08192
108201 - 08210
108221 - 08224
108241 - 08244
108251
108261
108271
108301 - 08320
108324 - 08330
108333
108401 - 08410
108451 - 08452
108471 - 08475
108501 - 08502
108551 - 08553
108581 - 08582
109001 - 09006
109101 - 09107
109161 - 09167
109201 - 09204
109221 - 09223
109227
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GroupVariable Number
109231 - 09232
109251
109271
109281
109286 - 09290
109411
109421
109438
109441
2. Spares Affected
None.
B. Concurrent Requirements
None.
C. Reason
Accomplishment of the inspections in this service bulletin will make sure that an engine number 1, 2,
3, or 4 nacelle strut has not drooped from its normal position and that the correct inboard and outboard
midspar fittings are installed on the engine number 2 and 3 nacelle struts. A drooped nacelle strut
indicates that a midspar fitting may have fractured. If an incorrect midspar fitting is installed, a fatigue
crack can occur which can cause a fracture of a midspar fitting. A fractured midspar fitting can result
in a separation of the nacelle strut and engine from the airplane in flight which could preclude safe
flight.
Operators have reported more than 45 of the midspar fittings with the 0.38 inch tang transition, cracked
on more than 40 airplanes with approximately 9,900 to 63,000 flight hours. There have been several
events where the engine and nacelle strut has separated from the airplane. In one instance, the engine
number 3 nacelle strut separated from the airplane and contacted the engine number 4 nacelle strut,
which also separated from the airplane.
This service bulletin gives instructions to inspect for the correct engine number 2 and 3 nacelle strut
midspar fittings, apply a droop stripe and inspect the engine number 1, 2, 3, and 4 nacelle strut for
droop.
Boeing Service Related Problem (SRP) 707-SRP-54-0105 is related to this service bulletin.
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D. Description
Do a general visual inspection of the engine number 1, 2, 3, and 4 nacelle struts for droop below the
normal position. Make sure each nacelle strut has not drooped from its normal position. Apply a stripe
to the inboard and outboard side of the engine number 1, 2, 3, and 4 nacelle strut if it has not been
previously accomplished. If a nacelle strut is drooped below its normal position contact Boeing for
further instructions and do the work as instructed by Boeing.
Do a detailed inspection of the engine number 2 and engine number 3 nacelle strut inboard and outboard
midspar fittings to confirm the correct part is installed. If an incorrect part is found replace the part in
accordance with Boeing service bulletin 707-3183.
Do a HFEC inspection of the engine number 2 and engine number 3 nacelle strut inboard and outboard
midspar fittings, to look for cracks. If a crack indication is found contact Boeing for further instructions
and do the work as instructed by Boeing.
NOTE: You do not need to change the existing droop stripe, if the droop stripe was applied in
accordance with Boeing service bulletin 707-3377 requirements.
The work in this service bulletin is done in the maintenance zone(s) given below.
Affected Maintenance Zones
ZoneModel
4-55, 4-56, 4-57, 4-58707-100, 707-100B, 707-200,
707-300, 707-300B, 707-300C,
707-400, 720, 720B
E. Compliance
The Federal Aviation Administration (FAA) will possibly release an Airworthiness Directive related to
this service bulletin. The Airworthiness Directive will make the compliance tasks and times given in this
service bulletin mandatory.
Table1: Droop Inspection of the Engine Number 1, 2, 3, and 4 Nacelle Strut, HFEC Inspection for cracks,
and Detailed Inspection for Correct Inboard and Outboard Midspar Fittings on the Engine Number 2
and 3 Nacelle Struts
Repeat Interval
(Not to Exceed)
Compliance Time (Whichever
Occurs Later)
ActionCondition
-Within 120 days after the original
issue date of this service bulletin.
Do a one time detailed
inspection on the engine
number 2 and engine
number 3 nacelle strut
midspar fittings to confirm
a 1 inch radius on the
transition area between
the fork and the lug in ac-
cordance with Paragraph
3.B., Work Instructions
Part 1.
All airplanes.
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Table1: Droop Inspection of the Engine Number 1, 2, 3, and 4 Nacelle Strut, HFEC Inspection for cracks,
and Detailed Inspection for Correct Inboard and Outboard Midspar Fittings on the Engine Number 2
and 3 Nacelle Struts
Repeat Interval
(Not to Exceed)
Compliance Time (Whichever
Occurs Later)
ActionCondition
-Before further flightInstall correct part in ac-
cordance with Boeing
service bulletin 707-3183.
Incorrect midspar fitting
part found on engine num-
ber 2 or number 3.
250 flight cycles or
12 months
whichever occurs
first.
Within 120 days
of the original is-
sue date of this
Service Bulletin.
Within 1,500
flight cycles or
48 months
whichever oc-
curs first from
the replacement
of the nacelle
strut inboard
and outboard
midspar fittings.
Do a High Frequency Ed-
dy Current (HFEC) inspec-
tion for any crack of the
visible area of the lug of
the inboard and outboard
strut midspar fittings on
engines number 2 and
number 3 in accordance
with Paragraph 3.B.,
Work Instructions Part 2.
All airplanes.
Before further flightContact Boeing for repair
instructions and do the
repair instructed by Boe-
ing.
Any crack is found in the
inboard or outboard strut
midspar fittings on engines
number 2 and number 3.
30 flight cycles.Within 120 days
after the original
issue date of
this service bul-
letin.
Within 1,500
flight cycles or
48 months,
whichever oc-
curs first, from
the replacement
of the nacelle
strut inboard
and outboard
midspar fittings.
Do a general visual in-
spection of engine num-
ber 1, 2, 3, and 4 nacelle
strut for signs of droop in
accordance with Para-
graph 3.B., Work Instruc-
tions Part 3. (c)
All airplanes.
(b)
Within 120 days
after the original
issue date of
this service bul-
letin
Within 1,500
flight cycles or
48 months,
whichever oc-
curs first, from
the replacement
of the nacelle
strut inboard
and outboard
midspar fittings.
Apply the droop stripe to
engine number 1, 2, 3,
and 4 nacelle strut in ac-
cordance with Paragraph
3.B., Work Instructions
Part 4. (a)
If the nacelle strut has not
drooped below its normal
position and no droop
stripe has been applied in
accordance with Boeing
service bulletin 707-3377.
-Before further flight.Contact Boeing for repair
instructions and do the
repair instructed by Boe-
ing.
Engine number 1, 2, 3, or
4 nacelle strut droop found.
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Table1: Droop Inspection of the Engine Number 1, 2, 3, and 4 Nacelle Strut, HFEC Inspection for cracks,
and Detailed Inspection for Correct Inboard and Outboard Midspar Fittings on the Engine Number 2
and 3 Nacelle Struts
Repeat Interval
(Not to Exceed)
Compliance Time (Whichever
Occurs Later)
ActionCondition
(a) You do not need to change the existing droop stripe, if the droop stripe is located in accordance with
Boeing service bulletin 707-3377 requirements.
(b) After both midspar fittings are replaced on a strut, start inspecting again, performing the initial inspection
within 1,500 flight cycles or 48 months, whichever occurs first, from the replacement of both of the nacelle
strut inboard and outboard midspar fittings.
(c) Checking the alignment of a droop stripe, previously applied per service bulletin 707-3377, is an acceptable
method of general visual inspection for signs of nacelle strut droop.
Boeing recommends that the general visual inspection of engine number 1, 2, 3, and 4 nacelle strut
for signs of droop given in Table 2 below, be done prior to each flight by the flight crew or ground crew.
Table 2: Preflight Droop inspection of the Engine Number 1, 2, 3, and 4 Nacelle Strut. (a)
Repeat Interval
(Not to Exceed)
Compliance TimeActionCondition
Prior to each flightPrior to the next flightDo a general visual in-
spection of engine num-
ber 1, 2, 3, and 4 nacelle
strut for signs of droop in
accordance with Para-
graph 3.B., Work Instruc-
tions Part 3. (a)
All airplanes
(a) This verification is not intended to be mandated by the FAA. It is Boeing's Intention, that this verification
will be accomplished by the flight crew or ground crew. The verification in Table 2 does not satisfy the
requirements of Table 1.
F. Approval
This service bulletin was examined by the Federal Aviation Administration (FAA). The changes specified
in this service bulletin comply with the applicable regulations and are FAA approved, as well as European
Aviation Safety Agency (EASA)/Joint Aviation Authorities (JAA) approved for all EASA/JAA approved
airplanes listed in the service bulletin effectivity. This service bulletin and its approval were based on
the airplane in its original Boeing delivery configuration or as modified by other approved Boeing
changes.
If an airplane has a non-Boeing modification or repair that affects a component or system also affected
by this service bulletin, the operator is responsible for obtaining appropriate regulatory agency approval
before incorporating this service bulletin.
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G. Manpower
The table below shows an estimate of the task hours necessary to do this inspections for each airplane.
This estimate is for direct labor only, done by an experienced crew. Adjust the estimate with operator
task hour data if necessary. The estimate does not include lost time. These are some examples of lost
time:
 Time to adjust to the workplace
 Time to schedule the work
 Time to inspect the work
 Time to cure the materials
 Time to make the parts
 Time to find the tools.
Elapsed HoursTask HoursNumber of PersonsTask
1.002.002FIGURE 1
2.004.002FIGURE 2
4.008.002FIGURE 3
2.505.002FIGURE 4
2.004.002FIGURE 5
11.5023.00TOTAL FOR EACH AIRPLANE
H. Weight and Balance Changes
None.
I. Electrical Load Data
Not applicable.
J. References
1. Existing Data
a. Boeing Service Bulletin 707-3183, 707-3377.
b. Boeing Service Related Problem (SRP) 707-SRP-54-0105.
c. Service Bulletin Index D6-1647.
d. Standard Overhaul Practices Manual (SOPM) SOPM 20-30-03, 20-41-02.
e. 707 Non Destructive testing Manual 707, 720 NDT Part 6, 51-00-00 Figure 24
f. 707 Maintenance Manual Subjects 12-3-1
2. Data supplied with this Service Bulletin
None.
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3. Installation Drawings Used in the Preparation of this Service Bulletin
None.
K. Publications Affected
None.
L. Interchangeability and Intermixability of Parts
Accomplishment of this service bulletin does not affect interchangeability or intermixability of parts.
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2.    MATERIAL INFORMATION
A. Material - Price and Availability
None.
B. Industry Support Information
Boeing warranty remedies are not available for the configuration changes inspection, and/or repair
procedures given in this service bulletin.
C. Parts Necessary For Each Airplane
1. Kits/Parts
None.
2. Parts and Materials Supplied by the Operator
NotesNameQTYPart Number /
Specification
(a)Primer4 ozBMS 10-11, Type I
(a)Enamel4 ozBMS 10-11, Type
II
(a)Corrosion Inhibiting Compound4 ozBMS 3-23 or
BMS3-35
(a) Refer to the Qualified Products List at the end of the Boeing Material Specification (BMS)
for supplier data.
3. Parts Modified and Reidentified
None.
4. Parts Removed and Not Replaced
None.
D. Parts Necessary to Change Spares
None.
E. Special Tooling - Price and Availability
None.
F. Special Tooling Necessary to do this Service Bulletin
No special tools or equipment are necessary to do the change in this service bulletin. But, maintenance
and overhaul tools in the manuals given in Paragraph 1.J., References, can be necessary. Examine
operator tool supply to make sure all necessary tools are available.
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### Page 21

3.    ACCOMPLISHMENT INSTRUCTIONS
A. GENERAL INFORMATION
CAUTION: KEEP THE WORK AREA, WIRES AND ELECTRICAL BUNDLES CLEAN OF METAL
PARTICLES OR CONTAMINATION WHEN YOU USE TOOLS. UNWANTED MATERIAL,
METAL PARTICLES OR CONTAMINATION CAUGHT IN WIRE BUNDLES CAN CAUSE
DAMAGE TO THE BUNDLES. DAMAGED WIRE BUNDLES CAN CAUSE SPARKS OR
OTHER ELECTRICAL DAMAGE.
NOTE: 1. Manual titles are referred to by acronyms. Refer to Paragraph 1.J., References, for
definition of the acronyms.
2. Obey all of the warnings and cautions given in the specified manual sections.
3. Unless shown differently, these dimensions and tolerances are used:
– Linear dimensions are in inches
– Tolerance on linear dimensions, other than rivet and bolt edge margins, is plus
or minus 0.03 inch
– Angular tolerance is plus or minus 2 degrees
4. Use the approved fastener and process material substitutions in accordance with
SRM Chapter 51.
5. A Detailed Inspection is defined as: An intensive examination of a specific item,
installation, or assembly to detect damage, failure, or irregularity. Available lighting
is normally supplemented with a direct source of good lighting at an intensity deemed
appropriate. Inspection aids such as mirrors, magnifying lenses, etc. may be
necessary. Surface cleaning and elaborate procedures may be required.
6. A General Visual Inspection is defined as: A visual examination of an interior or
exterior area, installation or assembly to detect obvious damage, failure or irregularity.
This level of inspection is made from within touching distance unless otherwise
specified. A mirror may be necessary to enhance visual access to all exposed surfaces
in the inspection area. This level of inspection is made under normally available
lighting conditions such as daylight, hangar lighting, flashlight or drop-light and may
require removal or opening of access panels or doors. Stands, ladders or platforms
may be required to gain proximity to the area being checked.
7. These work instructions refer to procedures included in other Boeing documents.
When the words "refer to" are used and the operator has an accepted alternative
procedure, the accepted alternative procedure can be used. When the words "in
accordance with" are included in the instruction, the procedure in the Boeing document
must be used.
8. Boeing Service Letter 707-SL-51-029 Damage Reporting and Repair Plan/Design
Guidelines, is an acceptable procedure to request information from Boeing for
additional structural repair instructions. The Service Letter describes what information
must be provided to Boeing before a structural repair can be provided.
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9. If it is necessary to remove more parts for access, you can remove those parts. If
you can get access without removing identified parts, it is not necessary to remove
all of the identified parts. Jacking and shoring limitations must be observed.
10. Where the work instructions include installation of a kept part, a new part with the
same part number can be installed as an alternative to the kept part.
B. WORK INSTRUCTIONS
1. PART 1 - ENGINE NUMBER 2 AND ENGINE NUMBER 3 NACELLE STRUT MIDSPAR FITTING
INSPECTION
a. Do a detailed inspection of the engine number 2 and engine number 3 nacelle strut midspar
fittings to confirm the correct part is installed in accordance with FIGURE 3.
(1) If the incorrect part is found, install the correct part in accordance with Boeing service
bulletin 707-3183.
2. PART 2 - ENGINE NUMBER 2 AND ENGINE NUMBER 3 NACELLE STRUT MIDSPAR FITTING
HFEC INSPECTION
a. Do a HFEC inspection of the engine number 2 and engine number 3 nacelle strut midspar
fittings for a crack in accordance with FIGURE 4.
(1) If any crack is found in the inboard or outboard midspar fittings, contact Boeing for repair
instructions and do the repair instructed by Boeing.
3. PART 3 - NACELLE STRUT DROOP INSPECTION
a. Do a general visual inspection of the engine number 1, 2, 3, and 4 nacelle struts to make sure
the nacelle strut has not drooped below it normal position in accordance with FIGURE 2.
NOTE: The above inspection is necessary to make sure that the strut is correctly aligned
with the trailing edge fairing. The installation of an indication stripe, on a strut that is
not aligned correctly, may not warn maintenance personnel of a fractured midspar
fitting.
(1) If a nacelle strut has drooped below it normal position, contact Boeing for repair instructions
and do the repair instructed by Boeing.
(2) Repeat the nacelle strut droop inspections at the time given in Paragraph 1.E., Compliance.
4. PART 4 - NACELLE STRUT AND SAILBOAT FAIRING DROOP STRIPE APPLICATION
a. If the nacelle strut has not drooped below its normal position and no droop stripe has been
applied in accordance with Boeing service bulletin 707-3377, apply the droop stripe to the
nacelle strut and sailboat fairing, on each side of the engine number 1, 2, 3, and 4 nacelle
strut in accordance with FIGURE 1.
NOTE: You do not need to change the existing droop stripe, if the droop stripe was applied
in accordance with Boeing service bulletin 707-3377 requirements.
5. Part 5 - CLOSE ACCESS
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a. Do the strut fairing and panel installation in accordance with FIGURE 5.
b. Put the airplane back to a serviceable condition.
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### Page 24 (OCR)

BOEING SERVICE BULLETIN А3537
ALERT  ALERT
NACELLE
STRUT #4
NACELLE
STRUT #3
= D
NACELLE
STRUT #2
VACELLE
STRUT #
NACELLE STRUT
SAILBOAT
FAIRING
2.0  2.0
ENGINE AND NACELLE
(TYPICAL)  1.0
- SKIN
3.5  JOINT
SKIN
JOINT  2110727
FIGURE 1: NACELLE STRUT AND SAILBOAT FAIRING DROOP STRIPE APPLICATION
(SHEET 1 OF 2)
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### Page 25

The step numbers shown below agree with the numbers shown in the circle symbols in the figure.
More DataQtyIdentificationNameTaskStep
(a)8-Nacelle Strut and Aft
Fairing
Clean1
(b)-BMS 10-11 TYPE IPrimerApply2
(b)-BMS 10-11 TYPE IIEnamelApply
(a) Clean and mask an area to be painted on both sides of each nacelle strut and sailboat fairing. Refer to
SOPM 20-30-03 as an accepted procedure.
(b) On both sides of each nacelle, apply a stripe of paint across the nacelle strut and the sailboat fairing. Use
a color that contrasts with the color of the part on which the paint is applied. Refer to SOPM 20-41-02 as
an accepted procedure.
FIGURE 1: NACELLE STRUT AND SAILBOAT FAIRING DROOP STRIPE APPLICATION
(SHEET 2 OF 2)
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BOEING SERVICE BULLETIN A3537
ALERT  ALERT
NACELLE
STRUT #4
NACELLE
STRUT #3
= D
NACELLE
STRUT #2
NACELLE
STRUT #1
NACELLE STRUT
SAILBOA®
-AIRING
ENGINE AND NACELLE
(TYPICAL)
- SKIN
JOINT
SKIN
JOINT  2112439
FIGURE 2: NACELLE STRUT DROOP
(SHEET 1 OF 2)
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### Page 27

The step numbers shown below agree with the numbers shown in the circle symbols in the figure.
More DataQtyIdentificationNameTaskStep
Do a general visual
inspection (a) (b)
8-Nacelle Strut and Aft
Fairing
Inspect1
(a) Look at the nacelle strut to see if it has drooped below normal position. Look at the stripe if present for
misalignment. In addition, look at the fairing straps, access panels and fairings between strut and wing
for buckles, wrinkles, cracks, elongated holes and loose or broken fasteners. Noticeable nacelle droop
or flexure damage to sheet metal may indicate that one or both midspar fittings are broken.
(b) The recommended verification, prior to each flight, does not have to be accomplished by a qualified me-
chanic.
FIGURE 2: NACELLE STRUT DROOP
(SHEET 2 OF 2)
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### Page 28 (OCR)

BOEING SERVICE BULLETIN А3537
ALERT  ALERT
NACELLE
STRUT #3
NACELLE
STRUT #2
MIDTING
2110707
FIGURE 3: ENGINE NUMBER 2 AND ENGINE NUMBER 3 NACELLE STRUT MIDSPAR FITTING INSPECTION
(SHEET 1 OF 3)
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### Page 29 (OCR)

BOEING SERVICE BULLETIN А3537
ALERT  ALERT
WEB
A-A
TYPICAL
0.38 R  1.00 R
NOMINAL  NOMINAL (3
(TYPICAL  (TYPICAL)
INCORRECT MIDSPAR FITTING  CORRECT MIDSPAR FITTING
FIGURE 3: ENGINE NUMBER 2 AND ENGINE NUMBER 3 NACELLE STRUT MIDSPAR FITTING INSPECTION
(SHEET 2 OF 3)
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### Page 30

The step numbers shown below agree with the numbers shown in the circle symbols in the figure.
More DataQtyIdentificationNameTaskStep
---Fairing StrapsRemove / Keep1
---Midspar Joint Access
Panels
Remove / Keep
---Strut-to-Wing Leading
Edge Fairings
Remove / Keep2
(a)4-Midspar FittingInspect3
(a) Do a detailed inspection of the engine number 2 and engine number 3 nacelle strut inboard and outboard
midspar fittings to make sure the correct part is installed. The correct part can be identified by a 1 inch
nominal radius on the transition area between the fork and the lug.
FIGURE 3: ENGINE NUMBER 2 AND ENGINE NUMBER 3 NACELLE STRUT MIDSPAR FITTING INSPECTION
(SHEET 3 OF 3)
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### Page 31 (OCR)

BOEING SERVICE BULLETIN А3537
ALERT  ALERT
NACELLE
STRUT #3
• D
NACELLE
STRUT #
SEE DETAIL II
NACELLE STRUT
#2 AND #3  SEE DETAIL I
2120246
FIGURE 4: ENGINE NUMBER 2 AND ENGINE NUMBER 3 NACELLE STRUT MIDSPAR FITTINGS HFEC
INSPECTION
(SHEET 1 OF 4)
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### Page 32 (OCR)

BOEING SERVICE BULLETIN A3537
ALERT  ALERT
1.50
, MIDSPAR FITTING
NACELLE STRUT SKIN
• ACCESS PANEL
FITTING HORIZONTAL TANGS  SEATING
0.375 R
• NACELLE STRUT SKIN
FITTING VERTICAL TANG
REMOVED MATERIAL
FWD
DETAIL I
OUTBOARD MIDSPAR FITTING
(ACCESS PANEL AND DRAG FITTING CLEVIS NOT SHOWN FOR CLARITY)
STRUT #2 SHOWN, STRUT #3 OPPOSITE
FAIRING ANGLE
0.375 R
NACELLE
ACCESS PANEL SEATING  STRUT SKIN
MIDSPAR FITTING  FITTING
1.50  HORIZONTAL TANGS
NACELLE STRUT SKIN  • FITTING VERTICAL TANG
FWD  REMOVED MATERIAL
DETAIL II
INBOARD MIDSPAR FITTING  2120416
(ACCESS PANEL AND DRAG FITTING CLEVIS NOT SHOWN FOR CLARITY)
STRUT #2 SHOWN, STRUT #3 OPPOSITE
FIGURE 4: ENGINE NUMBER 2 AND ENGINE NUMBER 3 NACELLE STRUT MIDSPAR FITTINGS HFEC
INSPECTION
(SHEET 2 OF 4)
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### Page 33 (OCR)

BOEING SERVICE BULLETIN А3537
ALERT  ALERT
- SEAL INSTALLATION
AREA OF
EXPOSED EDGE
AROUND ALL 4-  FASTENER HEADS
INSIDE
RADIUS
FWD  (FULL WIDTH)
A-A
(TYPICAL)
TOP SURFACE
(FULL WIDTH)
AREA EXPOSED
AFTER SKIN CUTOUT
OUTER
RADIUS
(FULL WIDTH)
WING FITTING
CLEVIS
FWD
(TYPICAL)  B-B  2120271
The step numbers shown below agree with the numbers shown in the circle symbols in the figure.
FIGURE 4: ENGINE NUMBER 2 AND ENGINE NUMBER 3 NACELLE STRUT MIDSPAR FITTINGS HFEC
INSPECTION
(SHEET 3 OF 4)
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### Page 34

More DataQtyIdentificationNameTaskStep
Gain additional ac-
cess for inspection.
(b) (c) (d)
--Upper Portion of Ac-
cess Panel
Cut1
This step is not re-
quired if the panels
have already been
cut.
HFEC inspect both
the inboard & out-
board Midspar Fit-
tings. (a) (e) (f)
2-Midspar FittingInspect2
(g)-BMS 3-23 OR BMS 3-
35
Corrosion Inhibiting
Compound
Apply3
(a) Perform a HFEC inspection in the areas indicated. Refer to Manual 707, 720 NDT Part 6, 51-00-00 Figure
24 as an accepted procedure.
(b) At the outboard midspar fitting, remove upper portion of access panel seating as shown in Detail I. Make
forward edge of cutout flush with aft edge of strut skin. Finish raw edges as given in operator's standard
procedure.
(c) At the inboard midspar fitting, remove upper portion of access panel seating as shown in Detail II. Make
forward edge of cutout flush with aft edge of strut skin. Also remove portion of fairing angle level with top
of existing circular cutout above fitting lug hole as shown. Finish raw edges as given in operator's standard
procedure.
(d) If nutplate rivet edge margin interferes with cutout of seating area on access panel, replace the nutplate
with one that has a corner type rivet ear.
(e) The trimming of material as shown in Details I and II is required for this inspection.
(f) Clean the indicated areas of the Midspar Fitting as required for the HFEC inspection. Refer to 707 Main-
tenance Manual Subject 12-3-1 as an accepted procedure.
(g) If no cracks are found in the midspar fittings, spray exposed areas of fittings with organic corrosion inhibitor.
FIGURE 4: ENGINE NUMBER 2 AND ENGINE NUMBER 3 NACELLE STRUT MIDSPAR FITTINGS HFEC
INSPECTION
(SHEET 4 OF 4)
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BOEING SERVICE BULLETIN А3537
ALERT  ALERT
NACELLE
STRUT #3
NACELLE
STRUT #2
2112445
FIGURE 5: ENGINE NUMBER 2 AND ENGINE NUMBER 3 NACELLE STRUT FAIRING AND PANEL
INSTALLATION
(SHEET 1 OF 2)
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### Page 36

The step numbers shown below agree with the numbers shown in the circle symbols in the figure.
More DataQtyIdentificationNameTaskStep
---Strut-to-Wing Leading
Edge Fairings
Install (Kept)1
---Midspar Joint Access
Panels
Install (Kept)2
---Fairing StrapsInstall (Kept)
FIGURE 5: ENGINE NUMBER 2 AND ENGINE NUMBER 3 NACELLE STRUT FAIRING AND PANEL
INSTALLATION
(SHEET 2 OF 2)
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