# Boeing Alert Service Bulletin 737-27A1324: No revision named

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- Document: [Boeing Alert Service Bulletin 737-27A1324](https://openairdocs.org/service-documents/boeing/737-27a1324.md)
- Title as filed: ASB 737-27A1324
- Pages: 29
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## Text

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### Page 1

Commercial 
Airplanes
737
Service Bulletin
ALERT
Number: 737-27A1324
Original Issue: March 02, 2021
ATA System: 2732
SUBJECT: FLIGHT CONTROL - Stall Warning System - Angle of Airflow Sensor Inspection and
Replacement
Export of this technology is controlled under the United States Export Administration Regulations (EAR) (15
CFR 300-774). An export license may be required before it is used for development, production or use by foreign
persons from specific countries. The controller of this data has the individual responsibility to abide by all export
laws.
9E991ECCN:
BOEING PROPRIETARY, CONFIDENTIAL AND/OR TRADE SECRET
Copyright © 2021 Boeing.
Unpublished Work. All Rights Reserved.
Treatment of this document and its content is governed by contract with Boeing. Rights to use this document
are licensed on a per aircraft basis and such rights may not be transferable. For more information, contact The
Boeing Company.
Boeing, the Boeing signature, the Boeing symbol, 707, 717, 727, 737, 747, 757, 767, 777, 787, Dreamliner,
BBJ, DC-8, DC-9, DC-10, KC-10, KC-46, KDC-10, MD-10, MD-11, MD-80, MD-88, MD-90, P-8, Poseidon and
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2.0

### Page 2

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### Page 3

Table of Contents
S u m m a r y  ...................................................... 5
1. PLANNING INFORMATION ........................................ 9
A . E f f e c t i v i t y  ................................................ 9
1. Airplanes ............................................. 9
2 . S p a r e s  A f f e c t e d  ........................................ 1 2
B. Concurrent Requirements ...................................... 1 2
C. Reason ................................................ 1 2
D. Description .............................................. 1 3
E. Compliance .............................................. 1 4
F . A p p r o v a l  ............................................... 1 5
G. Manpower .............................................. 1 6
H. Weight and Balance Changes .................................... 1 7
I. Electrical Load Data ......................................... 1 7
J . R e f e r e n c e s  .............................................. 1 7
1. Existing Data: ......................................... 1 7
2. Data Supplied with this Service Bulletin: ........................... 1 8
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
M. Software Accomplishment Summary ................................ 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 . K i t s / P a r t s  ............................................ 1 9
2. Parts and Materials Supplied by the Operator ........................ 1 9
3. Parts Modified and Reidentified ................................ 2 1
4. Parts Removed and Not Replaced .............................. 2 1
D. Parts Necessary to Change Spares ................................. 2 2
E. Special Tooling - Price and Availability ............................... 2 2
F. Special Tooling Necessary to do this Service Bulletin ....................... 2 2
3. ACCOMPLISHMENT INSTRUCTIONS .................................. 2 3
A. GENERAL INFORMATION ..................................... 2 3
B. WORK INSTRUCTIONS ....................................... 2 4
FIGURE 1: STA 247.70 ANGLE OF AIRFLOW SENSOR - INSPECTION OF LEFT SENSOR ..... 2 6
FIGURE 2: STA 247.70 ANGLE OF AIRFLOW SENSOR - INSPECTION OF RIGHT SENSOR .... 2 8
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Commercial 
Airplanes
737
Service Bulletin
ALERT
SummaryNumber: 737-27A1324Original Issue: March 02, 2021
ATA System: 2732
SUBJECT: FLIGHT CONTROL - Stall Warning System - Angle of Airflow Sensor Inspection and
Replacement
THIS DOCUMENT 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 DOCUMENT
TO THE NEW OPERATOR. IF APPLICABLE SPARES HAVE BEEN SOLD, SEND THIS DOCUMENT TO THE
NEW OWNER.
CONCURRENT REQUIREMENTS
None.
BACKGROUND
Boeing has received reports from operators of nuisance stick shaker activation on a non 737CL model while
the airplane was accelerating to cruise speed at the top of a climb. A review of recorded flight data and weather
reports indicated that the cause of the nuisance stick shakers was that the Angle of Airflow (AOA) sensor vanes
were frozen and malfunctioned due to insufficient heat in certain AOA sensors to prevent ice build-up in the
vane pivot. This condition can be caused by heavy moisture conditions on ground leading to water entering the
AOA vane pivot and freezing prior to or during flight. Boeing has determined that the potential for vane pivot
freezing exists with certain AOA sensor part numbers used on the 737-200 model. If this service bulletin is not
done, AOA sensors can freeze and malfunction, which can result in failure of the stall warning system and
potential impact to Continued Safe Flight and Landing (CSFL).
This service bulletin gives instructions to inspect the AOA sensor(s) installed on the airplane. Also, instructions
are given to replace existing AOA sensors that have heaters that are not sufficient to prevent ice build-up in the
vane pivot. Installation of new or serviceable AOA sensor(s) prevents failure of the stall warning system and
potential impact to CSFL.
Boeing Service Related Problem (SRP) 737-100/200/300/400/500-SRP-34-0141 is related to this service bulletin.
Boeing Service Related Problem (SRP) 737-100/200/300/400/500-SRP-34-0179 is related to this service bulletin.
Boeing Fleet Team Digest (FTD) 737-100/200/300/400/500 FTD 34-15002 is related to this service bulletin.
Boeing Service Letter (SL) 737-SL-34-152-D is related to this service bulletin.
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### Page 6

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 ChangesYesWeight and Balance Change
Paragraph 1.I., Electrical Load DataNoElectrical Load Changed
Paragraph 1.K., Publications AffectedYesPublications 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 Parts/Material
Paragraph 2.F., Special Tooling Necessary to
do this Service Bulletin
YesSpecial Tooling Required
ACTION
Group 1, Configuration 1:
At STA 247.70 on the left and right side of the airplane, inspect the AOA sensor to determine part number. If
the AOA sensor has a swept back shape vane or has incorrect part number, replace affected AOA sensor with
correct new or serviceable AOA sensor part number. If the AOA sensor has a rectangular flag shape vane or
has a correct part number, no further action is required.
Group 1, Configuration 2:
At STA 247.70 on the left side of the airplane, inspect the AOA sensor to determine part number. If the AOA
sensor has a swept back shape vane or has incorrect part number, replace AOA sensor with correct new or
serviceable AOA sensor part number. If the AOA sensor has a rectangular flag shape vane or has a correct part
number, no further action is required.
Group 2:
Boeing endorses the FAA rules related to Limit of Validity (LOV) and recommends immediate and permanent
removal from service of any airplanes upon reaching the LOV, whether or not it is operated under FAA jurisdiction.
As such, Boeing no longer provides maintenance instructions for airplanes that have accumulated flight cycles
beyond the LOV. Airplanes in Group 2 (737-200/-200C Airplanes, line numbers 44-286 inclusive) have
accumulated flight cycles beyond the LOV of the maintenance program. 14 CFR 121.1115 and 129.115 prohibit
operation of an airplane beyond its LOV.
EFFECTIVITY
737-200 and 737-200C Airplane(s). Refer to Paragraph 1.A.1., Airplanes, for the list of affected airplane(s).
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### Page 7

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 procedures and configuration changes given in
this service bulletin.
MANPOWER
Refer to Paragraph 1.G., Manpower.
MATERIAL INFORMATION
Operator Supplied Parts/Materials.
Refer to Paragraph 2.A., Material - Price and Availability.
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### Page 8 (OCR)

BOEING SERVICE BULLETIN 737-27A1324
ALERT  ALERT
A OR B
GROUP 1 CONFIGURATION 1:
AT STA 247.70 ON THE LEFT AND RIGHT SIDE OF THE AIRPLANE
-INSPECT THE AOA SENSORS TO DETERMINE PART NUMBER.
-IF THE AOA SENSOR HAS A SWEPT BACK SHAPE VANE OR HAS INCORRECT PART NUMBER,
REPLACE AFFECTED AOA SENSOR WITH NEW OR SERVICEABLE AOA SENSOR PART NUMBER.
- IF THE AOA SENSOR HAS A RECTANGLULAR FLAG SHAPE VANE OR HAS A CORRECT PART
NUMBER, NO FURTHER ACTION IS REQUIRED,
GROUP 1 CONFIGURATION2:
AT STA 274.70 ON THE LEFT SIDE OF THE AIRPLANE
- INSPECT THE AOA SENSOR TO DETERMINE PART NUMBER
-IF TH AOA SENSOR HAS A SWEPT BACK SHAPE VANE OR INCORRECT PART NUMBER.
REPLACE AOA SENSOR WITH NEW OR SERVICEABLE AOA SENSOR PART NUMBER.
- IF THE AOA SENSOR HAS A RECTANGULAR FLAG SHAPE VANE OR HAS A CORRECT PART
NUMBER, NO FURTHER ACTION IS REQUIRED.
ANGLE OF AIRFLOW SENSOR  2956420
(RIGHT SIDE SHOWN, LEFT SIDE OPPOSITE)
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### Page 9

Commercial 
Airplanes
737
Service Bulletin
ALERT
Number: 737-27A1324
Original Issue: March 02, 2021
ATA System: 2732
SUBJECT: FLIGHT CONTROL - Stall Warning System - Angle of Airflow Sensor Inspection and
Replacement
THIS DOCUMENT 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 DOCUMENT
TO THE NEW OPERATOR. IF APPLICABLE SPARES HAVE BEEN SOLD, SEND THIS DOCUMENT TO THE
NEW OWNER.
1.    PLANNING INFORMATION
A. Effectivity
1. Airplanes
This bulletin is applicable to 737-200, 737-200C Airplane(s), line number(s) 44, 102, 126, 139,
146, 149-150, 159, 162, 166, 172, 204, 207-208, 211, 221, 225-226, 242, 245, 254, 273-276, 283,
286, 295, 298-299, 303-304, 308-309, 314, 320-321, 326, 336, 338, 344-345, 349-350, 354-356,
359, 362-363, 366, 368, 371, 384, 404, 408, 411, 415, 422, 424, 427, 436-437, 442, 447, 458,
466, 468-469, 477, 483, 485, 488-489, 501-502, 507, 511-515, 522-523, 529-532, 535, 537, 539,
541, 546, 548, 555, 557-558, 560, 563, 565, 570, 572-573, 576-577, 579, 584, 588, 595, 597-600,
603, 605, 608, 610-611, 616, 618, 620-623, 627, 629, 632, 635-636, 640-644, 650-651, 655, 658,
660-661, 668-670, 672-673, 681-682, 686, 688-689, 694, 696, 699, 701, 706-708, 712-715, 718,
720-721, 726-727, 729, 731, 734, 736, 739, 741, 744-745, 747, 749-750, 752, 754, 760, 762-765,
769, 771-772, 781, 785-786, 789, 792-793, 795, 797-799, 801, 803, 805, 807-810, 812-813, 816,
820-822, 828-829, 831, 833-837, 839, 843, 845-847, 849, 851, 854, 856, 862-863, 867-868,
870-871, 877, 880, 883, 886, 891-892, 896, 899, 901-903, 905, 907, 910, 912, 914, 916, 923-924,
927-928, 932, 936, 938, 943, 946-947, 949-951, 953-955, 960-961, 963, 965-967, 969, 975-977,
981-983, 985, 987, 989, 992, 994, 996, 998, 1008-1009, 1011-1013, 1017-1020, 1023-1024,
1028-1029, 1031, 1033, 1035-1036, 1039-1040, 1042, 1046-1047, 1049, 1053, 1056, 1058-1059,
1061-1062, 1066, 1070-1071, 1075, 1077-1078, 1081-1082, 1089, 1091, 1093, 1095, 1097, 1099,
1102, 1113, 1117, 1154, 1178, 1189, 1197, 1226, 1236, 1241, 1257, 1261-1262, 1265, 1299,
1313, 1369, 1371, 1379, 1387, 1392, 1399, 1401, 1403, 1405, 1414, 1418, 1420, 1486, 1565,
1581, 1583, 1585 in 2 Group(s). Where the effectivity is presented with hyphens between line
numbers, the airplane applicability means "through" and "inclusive", e.g. line numbers 1-9 means
line numbers 1 through 9 inclusive.
Refer to Service Bulletin Index D6-19567 Part 3 for Airplane Variable Number, Line Number, and
Serial Number data.
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### Page 10

The Variable Numbers and Group Information for the applicable airplanes is given below.
DESCRIPTIONCONFIGURATIONGROUP
Airplanes with Angle of Airflow (AOA) sensors installed.-1
Airplanes with AOA sensors installed on the left and right side of the
airplane.
1
Airplanes with an AOA sensor installed on the left side of the airplane.2
737-200/-200C Airplanes, line numbers 44-286 inclusive, beyond the
Limit of Validity (LOV)
-2
Airplane Models:
737-200, 737-200C
GroupVariable Number
2PG055
2PG057
2PG075
2PG203
2PG219
2PG308
2PG310 - PG311
2PG375
2PG651 - PG652
2PH712 - PH713
2PH731
1PJ003
1PJ007 - PJ009
2PJ032
2PJ102 - PJ103
1PJ107
1PJ111 - PJ112
1PJ114 - PJ115
1PJ117
1PJ202
GroupVariable Number
1PJ206
1PJ211
1PJ213 - PJ215
1PJ217 - PJ219
1PK029
1PK051
1PK070
1PK112
1PK144
1PK202 - PK203
1PK213
1PK215
1PK217
1PK219
1PK238 - PK240
1PK257 - PK258
1PK274
1PK282
1PK312 - PK318
1PK357 - PK358
GroupVariable Number
1PK391
1PK431
1PK451
1PK495
1PK501
1PK503
1PK511
1PK524 - PK528
1PK548
1PK552
1PK558
1PK561
1PK565
1PK593
1PK598
1PK601
1PK604 - PK606
1PK609
1PK611 - PK613
1PK615
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GroupVariable Number
1PK617
1PK623 - PK624
1PK627
1PK632
1PK635
1PK641 - PK642
1PK664
1PK666
1PK671
1PK673
1PK677
1PK715
1PK731
1PK734 - PK735
1PK739 - PK743
1PK745
1PK747
1PK749 - PK751
1PK753 - PK754
1PK759 - PK760
1PK763 - PK764
1PK771
1PK801 - PK804
1PK821 - PK823
1PK826 - PK827
1PK830
1PK872
1PK903 - PK904
1PK907 - PK913
1PK915 - PK921
1PK923
1PK928 - PK930
1PK933 - PK934
GroupVariable Number
1PK936
1PK938
1PK971
1PK973
1PL001
1PL004
1PL008
1PL010 - PL011
1PL017 - PL019
1PL023
1PL026
1PL028
1PL081
1PL103 - PL111
1PL151
1PL202
1PL401
1PL403
1PL405
1PL408
1PL410 - PL411
1PL417
1PL441
1PL456
1PL471
1PL501
1PL503
1PL505 - PL506
1PL553 - PL555
1PL558
1PL560
1PL581
1PL601 - PL603
GroupVariable Number
1PL611
1PL621 - PL625
1PL631
1PL727 - PL730
1PL732 - PL733
1PL737
1PL741
1PL745
1PL768
1PL770
1PL793
2PL803
1PM001 - PM006
1PM016 - PM017
1PM051
1PM054
1PM061
1PM065 - PM066
1PM101
1PM103
1PM106
1PM108 - PM113
1PM115 - PM116
1PM119
1PM142
1PM252
1PM281 - PM283
1PN023
1PN028
1PN030
1PN032
1PN037
1PN039
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GroupVariable Number
1PN041
1PN082
1PN086
1PN102
1PN106
1PN133
1PN135
1PN141 - PN148
1PN150 - PN151
1PN154 - PN157
1PN162
1PN401
1PN403 - PN405
1PN407 - PN410
1PN415 - PN420
1PN431 - PN432
1PN452 - PN453
1PN455
1PN472
1PN474
1PN491
GroupVariable Number
1PN493
1PN501
1PN512
1PN521
2PX701
2PY002
2PY004
2PY021
1PY022
1PY037
1PY046 - PY047
1PY056 - PY057
1PY101
1PY103
1PY131
1PY135
1PY141 - PY142
1PY151
1PY153 - PY154
1PY162
1PY166
GroupVariable Number
1PY191
1PY201
1PY241 - PY244
1PY270
1PY274 - PY275
1PY281
2PY303
2PY322
2PY345 - PY346
2PY361
1PY410
1PY422
1PY441
1PY461
1PY592 - PY595
1PY611 - PY612
1PY631
1PY671 - PY672
1PY741
--
--
2. Spares Affected
None.
B. Concurrent Requirements
None.
C. Reason
Boeing has received reports from operators of nuisance stick shaker activation on a non 737CL model
while the airplane was accelerating to cruise speed at the top of a climb. A review of recorded flight
data and weather reports indicated that the cause of the nuisance stick shakers was that the Angle of
Airflow (AOA) sensor vanes were frozen and malfunctioned due to insufficient heat in certain AOA
sensors to prevent ice build-up in the vane pivot. This condition can be caused by heavy moisture
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### Page 13

conditions on ground leading to water entering the AOA vane pivot and freezing prior to or during flight.
Boeing has determined that the potential for vane pivot freezing exists with certain AOA sensor part
numbers used on the 737-200 model. If this service bulletin is not done, AOA sensors can freeze and
malfunction, which can result in failure of the stall warning system and potential impact to Continued
Safe Flight and Landing (CSFL).
This service bulletin gives instructions to inspect the AOA sensor(s) installed on the airplane. Also,
instructions are given to replace existing AOA sensors that have heaters that are not sufficient to prevent
ice build-up in the vane pivot. Installation of new or serviceable AOA sensor(s) prevents failure of the
stall warning system and potential impact to CSFL.
Boeing Service Related Problem (SRP) 737-100/200/300/400/500-SRP-34-0141 is related to this
service bulletin.
Boeing Service Related Problem (SRP) 737-100/200/300/400/500-SRP-34-0179 is related to this
service bulletin.
Boeing Fleet Team Digest (FTD) 737-100/200/300/400/500 FTD 34-15002 is related to this service
bulletin.
Boeing Service Letter (SL) 737-SL-34-152-D is related to this service bulletin.
D. Description
Group 1, Configuration 1:
At STA 247.70 on the left and right side of the airplane, inspect the AOA sensor to determine part
number. If the AOA sensor has a swept back shape vane or has incorrect part number, replace affected
AOA sensor with correct new or serviceable AOA sensor part number. If the AOA sensor has a
rectangular flag shape vane or has a correct part number, no further action is required.
Group 1, Configuration 2:
At STA 247.70 on the left side of the airplane, inspect the AOA sensor to determine part number. If the
AOA sensor has a swept back shape vane or has incorrect part number, replace AOA sensor with
correct new or serviceable AOA sensor part number. If the AOA sensor has a rectangular flag shape
vane or has a correct part number, no further action is required.
Group 2:
Boeing endorses the FAA rules related to Limit of Validity (LOV) and recommends immediate and
permanent removal from service of any airplanes upon reaching the LOV, whether or not it is operated
under FAA jurisdiction. As such, Boeing no longer provides maintenance instructions for airplanes that
have accumulated flight cycles beyond the LOV. Airplanes in Group 2 (737-200/-200C Airplanes, line
numbers 44-286 inclusive) have accumulated flight cycles beyond the LOV of the maintenance program.
14 CFR 121.1115 and 129.115 prohibit operation of an airplane beyond its LOV.
The work in this service bulletin is done in the maintenance zone(s) given below.
Affected Maintenance Zones
ZoneModel
2-21, 2-22737-200, 737-200C
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### Page 14

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.
When more than one OPTION is given for a CONDITION, do only one of the OPTION numbers. When
more than one ACTION is given for a CONDITION or an OPTION, do all of the ACTION numbers for
that CONDITION or OPTION.
Accomplish the required action(s), based on the applicable condition(s) in Table(s) 1 and 2, in accordance
with Paragraph 3. Accomplishment Instructions.
Group 1, Configuration 1:
Table 1: INSPECTION OF THE LEFT AND RIGHT ANGLE OF AIRFLOW SENSOR ON THE AIRPLANE
Repeat Interval
(Not to Exceed)
Compliance TimeActionCondition
-Within 24 months or
5,400 flight hours after
the Original Issue date of
this service bulletin,
whichever occurs first.
Do a General Visual Inspec-
tion (GVI) of the left and right
side AOA sensor vane
shape or inspect left and
right AOA sensor to deter-
mine part number.
All Airplanes
-Before further flight.Replace the affected Angle
of Airflow sensor with new or
serviceable part number
2566A-21 (Boeing part num-
ber 10-60878-3) or 2566A-
30 (Boeing part number 10-
60878-4).
CONDITION 1: ANY ANGLE OF
AIRFLOW SENSOR WITH A
SWEPT BACK SHAPE VANE
FOUND OR WITH PART NUM-
BER 861CAK (BOEING PART
NUMBER 10-62047-1) FOUND
--No further action is required.CONDITION 2: ANY ANGLE OF
AIRFLOW SENSOR WITH A
RECTANGULAR FLAG SHAPE
VANE FOUND OR WITH PART
NUMBER 2566A-21 OR 2566A-
30 (BOEING PART NUMBERS
10-60878-3 OR 10-60878-4)
FOUND
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### Page 15

Group 1, Configuration 2:
Table 2: INSPECTION OF THE LEFT ANGLE OF AIRFLOW SENSOR ON THE AIRPLANE
Repeat Interval
(Not to Exceed)
Compliance TimeActionCondition
-Within 24 months or
5,400 flight hours after
the Original Issue date of
this service bulletin,
whichever occurs first.
Do a General Visual Inspec-
tion (GVI) of the left side
AOA sensor vane shape or
inspect left side AOA sensor
to determine part number.
All Airplanes
-Before further flight.Replace the Angle of Airflow
sensor with new or service-
able part number 2566A-21
(Boeing part number 10-
60878-3) or 2566A-30 (Boe-
ing part number 10-60878-
4).
CONDITION 1: ANGLE OF
AIRFLOW SENSOR WITH A
SWEPT BACK SHAPE VANE
FOUND OR WITH PART NUM-
BER 861CAK (BOEING PART
NUMBER 10-62047-1) FOUND
--No further action is required.CONDITION 2: ANGLE OF
AIRFLOW SENSOR WITH A
RECTANGULAR FLAG SHAPE
VANE FOUND OR WITH PART
NUMBER 2566A-21 OR 2566A-
30 (BOEING PART NUMBERS
10-60878-3 OR 10-60878-4)
FOUND
Group 2:
Boeing endorses the FAA rules related to Limit of Validity (LOV) and recommends immediate and
permanent removal from service of any airplanes upon reaching the LOV, whether or not it is operated
under FAA jurisdiction. As such, Boeing no longer provides maintenance instructions for airplanes that
have accumulated flight cycles beyond the LOV. Airplanes in Group 2 (737-200/-200C Airplanes, line
numbers 44-286 inclusive) have accumulated flight cycles beyond the LOV of the maintenance program.
14 CFR 121.1115 and 129.115 prohibit operation of an airplane beyond its LOV.
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
Union 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 change 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
Group 1, Configuration 1:
INSPECTION OF THE LEFT AND RIGHT ANGLE OF AIRFLOW SENSOR ON THE AIRPLANE
Elapsed HoursTask HoursNumber of PersonsTask
0.100.101Open Access
0.100.101FIGURE 1
0.100.101FIGURE 2
1.001.001Remove (a)
1.001.001Install (a)
0.500.501Test (a)
0.100.101Close Access
2.902.90TOTAL FOR EACH AIRPLANE
(a) Removal, installation and test are dependent on inspection results. This esti-
mate includes the hours necessary for the removal, installation and test of
both left and right AOA sensors.
Group 1, Configuration 2:
INSPECTION OF THE LEFT ANGLE OF AIRFLOW SENSOR ON THE AIRPLANE
Elapsed HoursTask HoursNumber of PersonsTask
0.100.101Open Access
0.100.101FIGURE 1
0.500.501Remove (a)
0.500.501Install (a)
0.500.501Test (a)
0.100.101Close Access
1.801.80TOTAL FOR EACH AIRPLANE
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Group 1, Configuration 2:
INSPECTION OF THE LEFT ANGLE OF AIRFLOW SENSOR ON THE AIRPLANE
Elapsed HoursTask HoursNumber of PersonsTask
(a) Removal, installation and test are dependent on inspection results. This esti-
mate includes the hours necessary for the removal, installation and test of the
left AOA sensor.
H. Weight and Balance Changes
Change in Moment
(Pound-Inches)
Change in Weight
(Pounds)
Airplane
737-200, 737-200C
-290.9-1.4Group 1; Configuration 1; Condition 1(a)
-145.4-0.7Group 1; Configuration 2; Condition 1(a)(b)
(a) Applicable to the installation of AOA sensor part number 2566A-21.
(b) This is the weight change for the replacement of one AOA sensor. The quantity of parts
needed is dependent on the inspection results.
Change in Moment
(Pound-Inches)
Change in Weight
(Pounds)
Airplane
737-200, 737-200C
-228.6-1.1Group 1; Configuration 1; Condition 1(a)
-114.3-0.5Group 1; Configuration 2; Condition 1(a)(b)
(a) Applicable to the installation of AOA sensor part number 2566A-30.
(b) This is the weight change for the replacement of one AOA sensor. The quantity of parts
needed is dependent on the inspection results.
I. Electrical Load Data
Not applicable.
J. References
1. Existing Data:
a. Boeing Service Letter 737-SL-34-152-D
b. Boeing Service Related Problem (SRP) 737-100/200/300/400/500-SRP-34-0141,
737-100/200/300/400/500-SRP-34-0179
c. Service Bulletin Index D6-19567
d. 737-100/200/300/400/500 Fleet Team Digest (FTD) 34-15002
e. 737-100/200 Aircraft Maintenance Manual (AMM) 27-32-00, 27-32-11
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2. Data Supplied with this Service Bulletin:
None.
3. Installation Drawings Used in the Preparation of this Service Bulletin:
None.
K. Publications Affected
1. Publications:
Chapter-SectionPublication
27-32737 Aircraft Maintenance Manual - Practices
and Procedures
Equipment List737 Wiring Diagram Manual
27-30737 Illustrated Parts Catalog
2. Damage Tolerance Based Structural Inspections:
Boeing has evaluated the repairs or changes in this service bulletin for effects on Fatigue Critical
Structure (FCS) and for changes to Damage Tolerance Inspections (DTI) required in the
Maintenance Program. This service bulletin does not affect FCS, therefore DTIs are not necessary.
L. Interchangeability and Intermixability of Parts
Refer to Paragraph 2.C., Parts Necessary for Each Airplane, for interchangeability and intermixability
information.
M. Software Accomplishment Summary
Not affected.
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2.    MATERIAL INFORMATION
A. Material - Price and Availability
The operator can supply the parts and materials shown in Paragraph 2.C., 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.
B. Industry Support Information
Boeing warranty remedies are not available for the inspection procedures and configuration changes
given in this service bulletin.
C. Parts Necessary for Each Airplane
1. Kits/Parts
None.
2. Parts and Materials Supplied by the Operator
The following parts or materials are necessary to do the change in this service bulletin. Parts and
materials in the manuals given in Paragraph 1.J., References, can also be necessary. Examine
operator part and material supply to make sure all necessary parts and materials are available.
Group 1, Configuration 1:
NotesExisting Boe-
ing Part Num-
ber
Existing Sup-
plier Part
Number
NameQTYNew Boeing
Part Number
New Supplier
Part Number
(a)(b)(c)10-62047-10861CAKSENSOR - ANGLE
OF AIRFLOW
210-60878-3
OR
2566A-21 OR
2566A-30
10-60878-4
(d)66-21153-4-GASKET266-21153-4-
(d)66-21153-6-GASKET466-21153-6-
(d)66-21153-7
(66-21153-8
optional)
-FILLER RING266-21153-7
(66-21153-8
optional)
-
(e)BMS 5-95-ADHESIVE(f)BMS 5-95-
(a) The quantity shown is the maximum quantity of Angle of Airflow (AOA) sensors installed on each airplane.
The quantity of parts needed is dependent on the inspection results.
(b) You cannot use the existing part to replace the new part.
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### Page 20

Group 1, Configuration 1:
NotesExisting Boe-
ing Part Num-
ber
Existing Sup-
plier Part
Number
NameQTYNew Boeing
Part Number
New Supplier
Part Number
(c) Supplier Information:
GECAS Materials (0007), CAGE: 7421. Tel: 901-362-8600, Fax: 901-365-1482, Email: Sales@gecas.com
Aero Controls, Inc. (0062). Tel: 253-269-3100, Fax: 253-269-6700, Email: sales@aerocontrols.com
Kellstrom Aerospace (0096), CAGE: 57187. Tel: 847-233-5800, Fax: 847-233-5900, Email:
William.Braun@kellstromaerospace.com
Resources, Int'L (5018). Tel: 480-961-3600, Email: RFQ@TurboResources.com
Unical Aviation Inc. (9420). Tel: 909-348-1700, Fax: 909-869-7685, Email: sales@unical.com
Velocity Aerospace - NMB (AMSD). Tel: 214-396-9040, Email: NMBSales@VelocityAerospace.com
AvAir (AT39). Tel: 480-496-6736, Email: sales@avair.aero
OH Capital Assets, Inc. (B4XA). Tel: 704-283-5080, Fax: 704-283-5372, Email: info@ohcapitalassets.com
Dodson International Parts,Inc (3581). Tel: 785-878-8000, Fax: 785-878-8800, Email: sales@dodson.com
European Aviation Ltd / Skybus (A0V9). Tel 44 1531 633000, Email: jane.taylor@euroav.com
(d) The quantity shown is the maximum quantity of parts necessary for each airplane. A new gasket and
filler ring is necessary every time the AOA sensor is removed and installed. Refer to 737-100/200 AMM
27-32-11 for the parts necessary and quantity needed.
(e) Refer to the Qualified Products List at the end of the Boeing Material Specification (BMS) for supplier
data.
(f) Quantity as required.
Group 1, Configuration 2:
NotesExisting Boe-
ing Part Num-
ber
Existing Sup-
plier Part
Number
NameQTYNew Boeing
Part Number
New Supplier
Part Number
(a)(b)(c)10-62047-10861CAKSENSOR - ANGLE
OF AIRFLOW
110-60878-3
OR
2566A-21 OR
2566A-30
10-60878-4
(d)66-21153-4-GASKET166-21153-4-
(d)66-21153-6-GASKET266-21153-6-
(d)66-21153-7
(66-21153-8
optional)
-FILLER RING166-21153-7
(66-21153-8
optional)
-
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### Page 21

Group 1, Configuration 2:
NotesExisting Boe-
ing Part Num-
ber
Existing Sup-
plier Part
Number
NameQTYNew Boeing
Part Number
New Supplier
Part Number
(e)BMS 5-95ADHESIVE(f)BMS 5-95-
(a) The quantity shown is the maximum quantity of Angle of Airflow (AOA) sensors installed on each airplane.
The quantity of parts needed is dependent on the inspection results.
(b) You cannot use the existing part to replace the new part.
(c) Supplier Information:
GECAS Materials (0007), CAGE: 7421. Tel: 901-362-8600, Fax: 901-365-1482, Email: Sales@gecas.com
Aero Controls, Inc. (0062). Tel: 253-269-3100, Fax: 253-269-6700, Email: sales@aerocontrols.com
Kellstrom Aerospace (0096), CAGE: 57187. Tel: 847-233-5800, Fax: 847-233-5900, Email:
William.Braun@kellstromaerospace.com
Resources, Int'L (5018). Tel: 480-961-3600, Email: RFQ@TurboResources.com
Unical Aviation Inc. (9420). Tel: 909-348-1700, Fax: 909-869-7685, Email: sales@unical.com
Velocity Aerospace - NMB (AMSD). Tel: 214-396-9040, Email: NMBSales@VelocityAerospace.com
AvAir (AT39). Tel: 480-496-6736, Email: sales@avair.aero
OH Capital Assets, Inc. (B4XA). Tel: 704-283-5080, Fax: 704-283-5372, Email: info@ohcapitalassets.com
Dodson International Parts,Inc (3581). Tel: 785-878-8000, Fax: 785-878-8800, Email: sales@dodson.com
European Aviation Ltd / Skybus (A0V9). Tel 44 1531 633000, Email: jane.taylor@euroav.com
(d) The quantity shown is the maximum quantity of parts necessary for each airplane. A new gasket and
filler ring is necessary every time the AOA sensor is removed and installed. Refer to 737-100/200 AMM
27-32-11 for the parts necessary and quantity needed.
(e) Refer to the Qualified Products List at the end of the Boeing Material Specification (BMS) for supplier
data.
(f) Quantity as required.
3. Parts Modified and Reidentified
None.
4. Parts Removed and Not Replaced
None.
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D. Parts Necessary to Change Spares
None.
E. Special Tooling - Price and Availability
The operator can supply the tools shown in Paragraph 2.F., Special Tooling Necessary to do this
Service Bulletin. Tool price and supply data are not given.
F. Special Tooling Necessary to do this Service Bulletin
To get the tools shown below, refer to Paragraph 2.E., Special Tooling - Price and Availability.
Maintenance and overhaul tools in the manuals shown in Paragraph 1.J., References, can also be
necessary. Examine operator tool supply to make sure all necessary tools are available.
NameTool Part Number
Portable Calibrator(a)F72786-1
Portable Calibrator(a)(b)F72786-101
Portable Calibrator(a)(b)G34002-4
Portable Calibrator(a)(b)G34002-5
Ohmmeter(a)-
(a) This tool is applicable to Step 4 in Paragraph 3.B., Work Instructions.
(b) Equivalent/Alternate Portable Calibrator to F72786-1.
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3.    ACCOMPLISHMENT INSTRUCTIONS
A. GENERAL INFORMATION
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.
CAUTION
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
– Tolerance on rivet and bolt edge margin is plus or minus 0.05 inch
– Angular tolerance is plus or minus 2 degrees
– Hole dimensions for standard solid rivets and fasteners are in Structural Repair
Manual (SRM) Chapter 51
– Torque Values:
— Values for structural fasteners are given in 737 Structural Repair Manual,
Chapter 51.
— Values for airframe maintenance tasks are included in Chapter 20 of 737
Aircraft Maintenance Manual (AMM).
— Values for electrical maintenance tasks are included in Chapter 20 of
Standard Wiring Practices Manual (SWPM).
— Non-standard torque values for maintenance tasks are included in the
applicable installation step.
4. 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.
5. 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.
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6. 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.
7. Where the work instructions include installation of a kept part, a new or serviceable
part with the same part number can be installed as an alternative to the kept part.
8. This service bulletin includes functional test procedures for the systems changed by
this service bulletin. More functional tests can possibly be necessary in accordance
with standard maintenance practices because of interruption to other airplane systems.
9. Use of colors in Figures is based on guidance from the ATA e-Business Program
(ATA) iSpec 2200.
10. When more than one OPTION is given for a CONDITION, do only one of the OPTION
numbers. When more than one ACTION is given for a CONDITION or an OPTION,
do all of the ACTION numbers for that CONDITION or OPTION.
11. The compliance times for the actions in Paragraph 3.B., WORK INSTRUCTIONS
are in Paragraph 1.E., Compliance.
12. Some steps in the Work Instructions are labeled as Required for Compliance (RC).
If this service bulletin is mandated by an Airworthiness Directive (AD), then the steps
labeled as RC, including sub-steps under an RC step and any figures identified in
an RC step, must be done to comply with the AD. If a step or sub-step is labeled
"RC Exempt," then the RC requirement is removed from that step or sub-step. An
Alternative Method of Compliance (AMOC) is required for any deviations to RC steps,
including sub-steps and identified figures. Steps not labeled as RC may be deviated
from using accepted methods in accordance with the operator's maintenance or
inspection program without obtaining approval of an AMOC. This is provided that
the RC steps, including sub-steps and identified figures, can still be done as specified,
and the airplane can be put back in an airworthy condition.
B. WORK INSTRUCTIONS
1. Get access to the Angle of Airflow (AOA) sensors at STA 247.70 on the left and right side of the
airplane.
2. Group 1, Configuration 1:
RC - Do a General Visual Inspection (GVI) of the left and right side AOA sensor vane or inspect
left and right AOA sensor to determine part number in accordance with FIGURE 1 and FIGURE
2.
a. CONDITION 1: ANY ANGLE OF AIRFLOW SENSOR WITH A SWEPT BACK SHAPE VANE
FOUND OR WITH PART NUMBER 861CAK (BOEING PART NUMBER 10-62047-1) FOUND
(1) Replace the affected Angle of Airflow sensor with new or serviceable part number
2566A-21 (Boeing part number 10-60878-3) or 2566A-30 (Boeing part number
10-60878-4). Refer to 737-100/200 AMM 27-32-11 as an accepted procedure.
b. CONDITION 2: ANY ANGLE OF AIRFLOW SENSOR WITH A RECTANGULAR FLAG SHAPE
VANE FOUND OR WITH PART NUMBER 2566A-21 OR 2566A-30 (BOEING PART NUMBERS
10-60878-3 OR 10-60878-4) FOUND
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(1) No further action is required.
3. Group 1, Configuration 2:
RC - Do a General Visual Inspection (GVI) of the left side AOA sensor vane or inspect left side
AOA sensor to determine part number in accordance with FIGURE 1.
a. CONDITION 1: ANGLE OF AIRFLOW SENSOR WITH A SWEPT BACK SHAPE VANE
FOUND OR WITH PART NUMBER 861CAK (BOEING PART NUMBER 10-62047-1) FOUND
(1) Replace the Angle of Airflow sensor with new or serviceable part number 2566A-21
(Boeing part number 10-60878-3) or 2566A-30 (Boeing part number 10-60878-4). Refer
to 737-100/200 AMM 27-32-11 as an accepted procedure.
b. CONDITION 2: ANGLE OF AIRFLOW SENSOR WITH A RECTANGULAR FLAG SHAPE
VANE FOUND OR WITH PART NUMBER 2566A-21 OR 2566A-30 (BOEING PART NUMBERS
10-60878-3 OR 10-60878-4) FOUND
(1) No further action is required.
4. Do the Test System Performance. Refer to 737-100/200 AMM 27-32-00 as an accepted procedure.
If the test is not successful, do a corrective action and repeat the test until the test passes.
5. Put the airplane back to a serviceable condition.
6. Group 2:
Boeing endorses the FAA rules related to Limit of Validity (LOV) and recommends immediate and
permanent removal from service of any airplanes upon reaching the LOV, whether or not it is
operated under FAA jurisdiction. As such, Boeing no longer provides maintenance instructions for
airplanes that have accumulated flight cycles beyond the LOV. Airplanes in Group 2 (737-200/-200C
Airplanes, line numbers 44-286 inclusive) have accumulated flight cycles beyond the LOV of the
maintenance program. 14 CFR 121.1115 and 129.115 prohibit operation of an airplane beyond
its LOV.
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The step numbers shown below agree with the numbers shown in the circle symbols in the figure. The QTY
numbers shown below are the number of parts necessary for each airplane.
More DataQtyIdentificationNameTaskStep
(a)(b)1-SENSOR - ANGLE OF
AIRFLOW
Inspect1
FIGURE 1: STA 247.70 ANGLE OF AIRFLOW SENSOR - INSPECTION OF LEFT SENSOR
(SHEET 1 OF 2)
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More DataQtyIdentificationNameTaskStep
(a) Do a General Visual Inspection (GVI) of the AOA sensor vane shape or inspect AOA sensor to determine
part number.
(b) An acceptable AOA sensor is a sensor with a rectangular flag shape vane or with part number 2566A-21
or 2566A-30 (Boeing part number 10-60878-3 or 10-60878-4).
FIGURE 1: STA 247.70 ANGLE OF AIRFLOW SENSOR - INSPECTION OF LEFT SENSOR
(SHEET 2 OF 2)
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The step numbers shown below agree with the numbers shown in the circle symbols in the figure. The QTY
numbers shown below are the number of parts necessary for each airplane.
More DataQtyIdentificationNameTaskStep
(a)(b)1-SENSOR - ANGLE OF
AIRFLOW
Inspect1
FIGURE 2: STA 247.70 ANGLE OF AIRFLOW SENSOR - INSPECTION OF RIGHT SENSOR
(SHEET 1 OF 2)
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More DataQtyIdentificationNameTaskStep
(a) Do a General Visual Inspection (GVI) of the AOA sensor vane shape or inspect AOA sensor to determine
part number.
(b) An acceptable AOA sensor is a sensor with a rectangular flag shape vane or with part number 2566A-21
or 2566A-30 (Boeing part number 10-60878-3 or 10-60878-4).
FIGURE 2: STA 247.70 ANGLE OF AIRFLOW SENSOR - INSPECTION OF RIGHT SENSOR
(SHEET 2 OF 2)
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---
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