### Commercial **Airplane Group**  

# 747 Service Bulletin **SPECIAL ATTENTION Number: 747-34-2925**  Date: June 04, 2008 ATA System: 2732 3412 **SUBJECT:** NAVIGATION - Stall Warning System - Angle of Airflow Sensor Inspection Export of this technology is controlled under the United States Export Administration Regulations (EAR) (15 CFR 730-774). 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. 9E991 ECCN: 

## BOEING PROPRIETARY, CONFIDENTIAL, AND/OR TRADE SECRET Copyright © 2008 The Boeing Company Unpublished Work - All Rights Reserved Boeing claims copyright in each page of this document only to the extent that the page contains copyrightable subject matter.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, MD-10, MD-11, MD-80, MD-88, MD-90, and the Boeing livery are all trademarks owned by The Boeing Company; and no trademark license is granted in connection with this document unless provided in writing by Boeing.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. June 04, 2008 747-34-2925 1 of 26 2.0BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. June 04, 2008 747-34-2925 2 of 26 **BOEING SERVICE BULLETIN 747-34-2925**

BLANK PAGE**Table of Contents** Summary ..................................................... 5 1. PLANNING INFORMATION......................................... 7 A. Effectivity................................................ 7 1. Airplanes............................................. 7 2. Spares Affected . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 B. Concurrent Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 C. Reason . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 D. Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 E. Compliance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 F. Approval . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 G. Manpower . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 H. Weight and Balance Changes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 I. Electrical Load Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 J. References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 1. Existing Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 2. Data supplied with this Service Bulletin. . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 3. Installation Drawings Used in the Preparation of this Service Bulletin. . . . . . . . . . . . 19 K. Publications Affected. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 L. Interchangeability and Intermixability of Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 2. MATERIAL INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 A. Material - Price and Availability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 B. Industry Support Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 C. Parts Necessary For Each Airplane. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 1. Kits/Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 2. Parts and Materials Supplied by the Operator . . . . . . . . . . . . . . . . . . . . . . . . 21 3. Parts Modified and Reidentified. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 4. Parts Removed and Not Replaced . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 D. Parts Necessary to Change Spares. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 E. Special Tooling - Price and Availability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 F. Special Tooling Necessary to do this Service Bulletin. . . . . . . . . . . . . . . . . . . . . . . 22 3. ACCOMPLISHMENT INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 A. GENERAL INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 B. WORK INSTRUCTIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 FIGURE 1: ANGLE OF AIRFLOW SENSOR - INSPECTION . . . . . . . . . . . . . . . . . . . . . . . 26

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. June 04, 2008 747-34-2925 3 of 26 **BOEING SERVICE BULLETIN 747-34-2925**BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. June 04, 2008 747-34-2925 4 of 26 **BOEING SERVICE BULLETIN 747-34-2925**

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### Commercial **Airplane Group**  

# 747 Service Bulletin **SPECIAL ATTENTION Summary**  **Number: 747-34-2925** Date: June 04, 2008 ATA System: 2732 3412 **SUBJECT:** NAVIGATION - Stall Warning System - Angle of Airflow Sensor Inspection BOEING RECOMMENDS THAT EACH OPERATOR EXAMINE THIS SERVICE BULLETIN IMMEDIATELY. **CONCURRENT REQUIREMENTS** None. **BACKGROUND** This service bulletin gives instructions for a one-time inspection of Conrac/Ametek/Gulton Angle of Airflow (AOA) sensors with part numbers 2566A21/A30 (10-60878-3/-4) for 747-100/200/300 airplanes and part numbers 2566A40S (S233T913-2) for 747-400 airplanes. This inspection will do a check for a misalignment between the AOA sensor shaft and the sensor synchro transmitter. This misalignment is caused by a defective set screw condition.The airplane could have incorrect control column shaker activation if the inspection given in this service bulletin is not accomplished. One 747-400 operator reported a control column shaker activation on takeoff. The control column shaker activation continued while the airplane was in flight and EICAS messages ALT DISAGREE and IAS DISAGREE were displayed. The flight crew used the alternative Air Data Computer (left ADC) and the altitude and airspeed indications cancelled. After landing the right ADC was replaced. On the subsequent flight the control column shaker operated again at takeoff and the flight crew had to do a Rejected Takeoff (RTO). Troubleshooting steps found that the right AOA sensor was unserviceable. The inspection of the AOA sensor showed that the set screw connected to the synchro transmitter was not correctly attached to the AOA sensor shaft. Accomplishment of this service bulletin will stop incorrect control column shaker activation. Boeing Service Related Problem (SRP) 747-SRP-34-0114 is related to this service bulletin. Fleet Team Digest (FTD) 747 FTD 34-07001 is related to this service bulletin. **ACTION** Part 1: Do a visual inspection of the AOA sensors. If an AOA sensor is found to be a Conrac/Ametek/Gulton sensor, do Part 2 of the service bulletin. **Group 1:** Part 2: Do a test of the AOA sensor. If the AOA sensor fails to activate the control column shaker, do Part 3 of the service bulletin.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. June 04, 2008 747-34-2925 5 of 26**Group 2:** Part 2: Do a test of the AOA sensor. If the AOA sensor fails the test, replace the AOA sensor. **Group 1:** Part 3: Do an Aircraft Maintenance Manual (AMM) Operational Test of the Stall Warning System. If the AOA sensor fails to activate the control column shaker, replace the AOA sensor. **NO TE:**  New part is only necessary if the inspection and test indicate that the existing sensor must be replaced. **EFFECTIVITY** 747-100/100B/100B SUD/200B/200C/200F/300/400/400D/400F/747SP/747SR Airplanes. Refer to Paragraph 1.A., Effectivity, Airplanes for the list of affected airplanes. **COMPLIANCE** Refer to Paragraph 1.E., Compliance. **INDUSTRY SUPPORT INFORMATION** Boeing warranty remedies are not available for the inspection given in this service bulletin. **MANPOWER** Refer to Paragraph 1.G., Manpower. **MATERIAL INFORMATION** None.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. June 04, 2008 747-34-2925 6 of 26 **BOEING SERVICE BULLETIN 747-34-2925**

### Commercial **Airplane Group**  

# 747 Service Bulletin **SPECIAL ATTENTION Number: 747-34-2925**  Date: June 04, 2008 ATA System: 2732 3412 **SUBJECT:** NAVIGATION - Stall Warning System - Angle of Airflow Sensor Inspection BOEING RECOMMENDS THAT EACH OPERATOR EXAMINE THIS SERVICE BULLETIN IMMEDIATELY. **1. PLANNING INFORMATION A. Effectivity**  1. Airplanes Refer to Service Bulletin Index Document D6-30300 Part 3 for Airplane Variable Number, Line Number, and Serial Number data. This service bulletin is for the airplanes shown below.
**DESCRIPTION CONFIGURATION**  **GROUP** 747-100/200/300 airplanes that require different Angle of Airflow (AOA) sensor inspection - 1
747-400 airplanes that require different Angle of Airflow (AOA) sensor inspection - 2

Airplane Models: 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747-400, 747-400D, 747-400F, 747SP, 747SR **Group Variable Number**  1 RA001 - RA034 1 RA101 - RA115 1 RA161 - RA164 1 RA201 - RA203 1 RA216 - RA217 1 RA245 - RA246 1 RA251 - RA266

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. June 04, 2008 747-34-2925 7 of 26**Group Variable Number**  1 RA301 - RA318 1 RA351 - RA360 1 RA369 - RA373 1 RA401 - RA418 1 RA501 - RA502 1 RA521 - RA528 1 RA532 - RA548 1 RA551 - RA552 1 RA559 - RA561 1 RA581 - RA582 1 RA585 1 RA601 - RA602 1 RA631 - RA635 1 RA651 - RA652 1 RA671 - RA677 1 RA701 - RA702 1 RA721 - RA731 1 RA741 - RA745 1 RA749 - RA750 1 RA761 - RA762 1 RA781 - RA784 1 RA901 - RA916 1 RB001 - RB016 1 RB041 - RB044 1 RB071 - RB075 1 RB101 - RB102 1 RB411 - RB413 1 RB421 1 RB601 - RB607 1 RB681 - RB697 1 RB711 1 RB721 - RB723 1 RB741 - RB748

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. June 04, 2008 747-34-2925 8 of 26 **BOEING SERVICE BULLETIN 747-34-2925 Group**  **Variable Number** 1 RD001 - RD004 1 RD021 - RD022 1 RD041 - RD059 1 RD071 - RD072 1 RD081 - RD083 1 RD091 - RD092 1 RD101 - RD104 1 RD121 - RD127 1 RD131 - RD144 1 RD166 - RD167 1 RD171 - RD172 1 RD181 - RD183 1 RD201 - RD204 1 RD221 - RD227 1 RD231 - RD235 1 RD241 - RD243 1 RD251 - RD262 1 RD271 - RD272 1 RD291 - RD292 1 RD301 - RD302 1 RD311 1 RD351 - RD358 1 RD361 - RD366 1 RD381 - RD383 1 RD411 - RD414 1 RD421 - RD426 1 RD431 - RD435 1 RD441 - RD442 1 RD451 - RD456 1 RD461 1 RD471 - RD475 1 RD513 - RD519 1 RD531 - RD533

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. June 04, 2008 747-34-2925 9 of 26 **BOEING SERVICE BULLETIN 747-34-2925 Group**  **Variable Number** 1 RD551 1 RD561 1 RD571 1 RD581 - RD583 1 RD591 - RD593 1 RD601 - RD607 1 RD621 - RD623 1 RD641 - RD649 1 RD651 - RD659 1 RD661 1 RD671 1 RD681 - RD682 1 RD691 - RD692 1 RD701 - RD702 1 RD721 - RD722 1 RD741 - RD742 1 RD751 - RD755 1 RD761 1 RD771 - RD775 1 RD781 - RD783 1 RD791 - RD792 1 RE001 2 RF001 - RF006 1 RG001 - RG009 1 RG091 1 RG095 1 RG101 - RG104 1 RG121 - RG126 1 RG141 - RG142 1 RG161 - RG164 1 RG171 - RG174 1 RG191 - RG193 1 RG211 - RG213

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. June 04, 2008 747-34-2925 10 of 26 **BOEING SERVICE BULLETIN 747-34-2925 Group**  **Variable Number** 1 RG221 - RG222 1 RH101 - RH102 1 RH111 - RH112 1 RH121 - RH122 1 RJ131 - RJ133 1 RJ151 - RJ152 1 RJ301 - RJ303 1 RJ321 - RJ322 1 RJ331 - RJ333 2 RL401 - RL403 2 RL411 - RL436 2 RL451 - RL456 2 RL461 - RL462 2 RL471 - RL475 2 RL481 2 RL491 - RL492 2 RL501 - RL502 2 RL511 - RL515 2 RL521 - RL522 2 RL531 - RL533 2 RL561 - RL562 2 RL576 2 RL651 - RL655 2 RL671 - RL675 2 RL681 - RL684 2 RL751 - RL752 2 RM001 - RM007 2 RM010 - RM013 2 RM021 - RM024 2 RM026 - RM030 2 RM036 - RM045 2 RM051 - RM053 2 RM071

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. June 04, 2008 747-34-2925 11 of 26 **BOEING SERVICE BULLETIN 747-34-2925 Group**  **Variable Number** 2 RM081 - RM084 2 RM091 2 RM096 - RM097 2 RM116 - RM117 2 RM126 - RM132 2 RM136 - RM147 2 RM156 - RM158 2 RM166 - RM177 2 RM191 - RM192 2 RM231 - RM233 2 RM241 - RM246 2 RM261 - RM264 2 RM316 - RM318 2 RM331 - RM333 2 RM341 2 RM351 - RM355 2 RM366 - RM367 2 RM401 - RM403 2 RM426 2 RM431 2 RM441 - RM443 2 RM445 2 RM801 - RM803 2 RM811 - RM813 2 RM851 - RM859 2 RM861 - RM863 2 RM871 - RM899 2 RM901 - RM906 2 RM911 1 RR001 - RR005 1 RR021 - RR025 1 RR031 1 RR201 - RR206

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. June 04, 2008 747-34-2925 12 of 26 **BOEING SERVICE BULLETIN 747-34-2925 Group**  **Variable Number** 1 RR221 - RR226 1 RR261 - RR267 1 RR301 - RR310 1 RR331 - RR332 1 RR336 1 RR341 - RR345 1 RR361 - RR362 1 RR421 - RR422 1 RR431 - RR432 1 RR441 - RR442 1 RR451 1 RR501 - RR504 1 RR521 - RR522 1 RR526 1 RR531 1 RR551 - RR556 1 RR561 1 RR566 2 RR701 2 RR721 - RR724 2 RR746 - RR748 2 RR851 - RR856 2 RR861 - RR862 2 RR951 - RR952 1 RS001 - RS002 1 RS201 1 RS211 - RS212 1 RS221 - RS222 1 RS231 - RS241 1 RS251 - RS259 1 RS263 1 RS265 - RS268 1 RS271 - RS276

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. June 04, 2008 747-34-2925 13 of 26 **BOEING SERVICE BULLETIN 747-34-2925 Group**  **Variable Number** 1 RS291 - RS292 1 RS301 - RS306 1 RS311 - RS320 1 RS331 - RS333 1 RS341 - RS342 1 RS699 1 RS701 - RS703 1 RS711 - RS713 1 RS721 - RS722 1 RS741 - RS743 1 RS751 - RS752 1 RS761 - RS762 1 RS771 1 RS781 - RS782 1 RS786 2 RT001 - RT014 2 RT021 - RT022 2 RT031 - RT035 2 RT041 - RT047 2 RT061 2 RT071 - RT075 2 RT101 - RT103 2 RT121 2 RT131 - RT137 2 RT151 - RT152 2 RT161 - RT168 2 RT401 - RT412 2 RT431 - RT447 2 RT451 - RT469 2 RT471 - RT499 2 RT501 - RT535 2 RT551 - RT568 2 RT571 - RT591

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. June 04, 2008 747-34-2925 14 of 26 **BOEING SERVICE BULLETIN 747-34-2925 Group**  **Variable Number** 2 RT601 - RT657 2 RT671 - RT673 2 RT681 - RT682 2 RT691 - RT699 2 RT701 - RT704 2 RT711 - RT717 2 RT741 - RT757 2 RT776 - RT777 2 RT781 - RT784 2 RT801 - RT803 2 RT811 - RT814 2 RT831 - RT837 2 RT861 - RT864 2 RT876 - RT880 2 RT931 - RT932 2 RT945 - RT949 2 RT951 - RT955 2 RT966 - RT967 2 RU001 - RU006 2 RU016 - RU017 2 RU031 - RU032 2 RU051 - RU052 2 RU059 - RU062 2 RU081 - RU083 2 RU101 - RU102 2 RU121 - RU132 2 RU801 - RU809 2 RU831 - RU841 2. Spares Affected None. **B. Concurrent Requirements** None.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. June 04, 2008 747-34-2925 15 of 26 **BOEING SERVICE BULLETIN 747-34-2925 C. Reason**  This service bulletin gives instructions for a one-time inspection of Conrac/Ametek/Gulton Angle of Airflow (AOA) sensors with part numbers 2566A21/A30 (10-60878-3/-4) for 747-100/200/300 airplanes and part numbers 2566A40S (S233T913-2) for 747-400 airplanes. This inspection will do a check for a misalignment between the AOA sensor shaft and the sensor synchro transmitter. This misalignment is caused by a defective set screw condition. The airplane could have incorrect control column shaker activation if the inspection given in this service bulletin is not accomplished. One 747-400 operator reported a control column shaker activation on takeoff. The control column shaker activation continued while the airplane was in flight and EICAS messages ALT DISAGREE and IAS DISAGREE were displayed. The flight crew used the alternative Air Data Computer (left ADC) and the altitude and airspeed indications cancelled. After landing the right ADC was replaced. On the subsequent flight the control column shaker operated again at takeoff and the flight crew had to do a Rejected Takeoff (RTO). Troubleshooting steps found that the right AOA sensor was unserviceable. The inspection of the AOA sensor showed that the set screw connected to the synchro transmitter was not correctly attached to the AOA sensor shaft. Accomplishment of this service bulletin will stop incorrect control column shaker activation. Boeing Service Related Problem (SRP) 747-SRP-34-0114 is related to this service bulletin. Fleet Team Digest (FTD) 747 FTD 34-07001 is related to this service bulletin. **D. Description** Part 1: Do a visual inspection of the AOA sensor. If the AOA sensor is found to be a Conrac/Ametek/Gulton sensor, do Part 2 of the service bulletin. **Group 1:** Part 2: Do a test of the AOA sensor. If the AOA sensor fails to activate the control column shaker, do Part 3 of the service bulletin. **Group 2:** Part 2: Do a test of the AOA sensor. If the AOA sensor fails the test, replace the AOA sensor. **Group 1:** Part 3: Do an Aircraft Maintenance Manual (AMM) Operational Test of the Stall Warning System. If the AOA sensor fails to activate the control column shaker, replace the AOA sensor. **NO TE:**  New part is only necessary if the inspection and test indicate that the existing sensor must be replaced. **Group 1:**
**Affected Maintenance Zones Zone**  **Model** 113, 114 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747SP, 747SR

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. June 04, 2008 747-34-2925 16 of 26 **BOEING SERVICE BULLETIN 747-34-2925 Group 2:** 
**Affected Maintenance Zones Zone**  **Model** 211, 212 747-400, 747-400D, 747-400F **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. Boeing recommends that the inspection given in this service bulletin be done within 36 months after the date on this service bulletin. If an AOA check (such as Maintenance Planning Document (MPD) Task 4-27-0160 for 747-100/200/300 operators or an equivalent task for 747-400 operators associated with a 'C' check) has been accomplished within the last 15 months or if one is scheduled within the compliance time, it can take the place of the required check and the service bulletin is considered accomplished. **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. **G. Manpower** The table below shows an estimate of the task hours necessary to do this inspection for each sensor. 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.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. June 04, 2008 747-34-2925 17 of 26 **BOEING SERVICE BULLETIN 747-34-2925 PART 1**  **Elapsed Hours Task Hours**  **Number of Persons**  **Task**

0.10 0.10 1 Inspection 0.10 0.10 TOTAL FOR EACH SENSOR

**PART 2 Elapsed Hours**  **Task Hours Number of**  **Persons Task** 

0.25 0.50 2 Test 0.25 0.50 TOTAL FOR EACH SENSOR **Group 1:**
**PART 3 Elapsed Hours**  **Task Hours Number of**  **Persons Task** 

0.25 0.50 2 Test 0.25 0.50 TOTAL FOR EACH SENSOR **H. Weight and Balance Changes** None. **I. Electrical Load Data** Not changed. **J. References** 1. Existing Data a. 747-100/200/300 Maintenance Planning Data (MPD) Task 4-27-0160 a. Boeing Service Related Problem (SRP) 747-SRP-34-0114 b. 747 Fleet Team Digest (FTD) 34-07001 c. 747-100/200/300 Aircraft Maintenance Manual (AMM) 24-22-00, 27-32-00, 27-32-01, 27-51-00 d. 747-400 Aircraft Maintenance Manual (AMM) 24-22-00, 34-12-03 e. 747-100/200/300 Maintenance Planning Data (MPD) Task 4-27-0160

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. June 04, 2008 747-34-2925 18 of 26 **BOEING SERVICE BULLETIN 747-34-2925**2. Data supplied with this Service Bulletin None. 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.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. June 04, 2008 747-34-2925 19 of 26 **BOEING SERVICE BULLETIN 747-34-2925**BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. June 04, 2008 747-34-2925 20 of 26 **BOEING SERVICE BULLETIN 747-34-2925**

BLANK PAGE**2. MATERIAL INFORMATION A. Material - Price and Availability**  None. **B. Industry Support Information** Boeing warranty remedies are not available for the configuration changes inspection given in this service bulletin. **C. Parts Necessary For Each Airplane** 1. Kits/Parts None. 2. Parts and Materials Supplied by the Operator
**Notes Name**  **QTY Part Number /**  **Specification** (a) (b) (c) (d) Angle of Attack Sensor 1 2566A21 or 2566A30 (10-60878-3 or 10-60878-4) (a) (b) (c) (e) Angle of Attack Sensor 1 2566A40S or S233T913-2 (a) Each airplane has 2 stall warning system angle of attack sensors installed. (b) This part is only necessary if the inspection and tests indicate the existing sensor must be replaced. (c) Ametek Aerospace (V92627), 1644 Whittier Ave, Costa Mesa, California 92627-4415. (d) For 747-100/200/300 airplanes. (e) For 747-400 airplanes.
3. Parts Modified and Reidentified None. 4. Parts Removed and Not Replaced None. **D. Parts Necessary to Change Spares** None.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. June 04, 2008 747-34-2925 21 of 26 **BOEING SERVICE BULLETIN 747-34-2925 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.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. June 04, 2008 747-34-2925 22 of 26 **BOEING SERVICE BULLETIN 747-34-2925 3. ACCOMPLISHMENT INSTRUCTIONS**  **A. GENERAL INFORMATION CA** **UTION:** 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. **NO TE:**  1. The instructions identified in Paragraph 3.B., Work Instructions and the Figure(s) give the recommended sequence of steps. The sequence of steps to do this service bulletin can be changed. 2. Manual titles are referred to by acronyms. Refer to Paragraph 1.J., References, for definition of the acronyms. 3. Obey all of the warnings and cautions given in the specified manual sections. 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 ensure visual access to all surfaces in the inspection area. This level of inspection is made under normal 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 "as given in" are included in the instruction, the procedure in the Boeing document must be used. **B. WORK INSTRUCTIONS P** 

**AR T 1:** **ANGLE OF AIRFLO W (A** **O A) SENSOR**  1. Do a General Visual Inspection of the AOA sensors as given in FIGURE 1.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. June 04, 2008 747-34-2925 23 of 26 **BOEING SERVICE BULLETIN 747-34-2925**a. If an AOA sensor is a Conrac/Ametek/Gulton AOA sensor with a paddle type vane is installed, do PART 2: TEST THE STALL WARNING SYSTEM for that sensor. b. If a BF Goodrich/Rosemount AOA sensor with a swept vane is installed, no more work is necessary. **Group 1: P** 

**AR T 2:** **TEST THE ST**  **ALL W**  **ARNING SYSTEM** 1. Supply electrical power to the airplane. Refer to 747-100/200/300 AMM 24-22-00 as an accepted procedure. 2. Make sure the applicable circuit breakers for the Stall Warning System are closed. Refer to 747-100/200/300 AMM 27-32-00 as an accepted procedure. 3. At the P5 Overhead panel, move the stall warning HTR OFF-NORMAL-TEST switch to HTR OFF position. 4. Move the trailing edge flaps to the 30 detent position. Refer to 747-100/200/300 AMM 27-51-00 as an accepted procedure. **W**

**ARNING:** SUFFICIENT TIME MUST BE ALLOWED FOR SENSOR VANES TO COOL BEFORE CONTINUING TEST. VANES MAY BE HOT ENOUGH TO CAUSE BURNS. **CA UTION:**  VANES MUST NOT BE SPUN. DAMAGE TO SYNCHROS COULD OCCUR. 5. Make sure the AOA sensors are at the horizontal position. 6. Move the left AOA sensor vane trailing edge up from the zero degrees position to approximately 24 degrees (7.5 degrees position on the AOA sensor scale). 7. On the flight deck, make sure the control column shaker is activated within a tolerance of +/-1 degree. a. If the control column shaker is activated, no more work is necessary. Put the airplane back to a serviceable condition. b. If the control column shaker is not activated, do Part 3: Operational Test of the Stall Warning System. 8. If necessary, repeat steps 6. and 7. again for the right AOA sensor. **Group 1: P** 

**AR T 3:** **OPERA TIONAL** **TEST OF THE ST**  **ALL W**  **ARNING SYSTEM** 1. Do an Operational Test of the Stall Warning System. Refer to 747-100/200/300 AMM 27-32-00 as an accepted procedure.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. June 04, 2008 747-34-2925 24 of 26 **BOEING SERVICE BULLETIN 747-34-2925**a. If the AOA sensor fails to activate the control column shaker in this operational test, replace the AOA sensor. Refer to 747-100/200/300 AMM 27-32-01 as an accepted procedure. 2. Put the airplane back to a serviceable condition. **Group 2: P** 

**AR T 2:** **TEST THE ST**  **ALL W**  **ARNING SYSTEM** 1. Supply electrical power to the airplane. Refer to 747-400 AMM 24-22-00 as an accepted procedure. 2. Make sure the applicable circuit breakers for the Stall Warning System are closed. Refer to 747-400 AMM 34-12-03 as an accepted procedure. 3. Open and attach DO-NOT-CLOSE tags to the circuit breakers for the Left and Right AOA heaters. Refer to 747-400 AMM 34-12-03 as an accepted procedure. **W**

**ARNING:** DO NOT TOUCH THE AOA SENSOR WHEN THE SENSOR HEAT IS ON.YOU CAN BURN YOURSELF ON THE AOA SENSOR. 4. Attach an angular displacement tool to the AOA sensor vane to be tested. 5. Connect an ARINC 429 bus reader to the Air Data Computer (ADC) test connector (the left ADC for the left AOA sensor, the right ADC for the right AOA sensor). **NO TE:**  The "HI" pin is on the left of the "TEST ONLY" connector and the "LO" pin is on the right of the test connector. 6. Move the angular displacement tool on the AOA vane to the values given in the table that follows: **NO TE:**  Make sure the data bus reader shows the values on the table that follows in decimal format. **NO TE:**  A positive angle of attack is produced when the trailing edge of the AOA vane is above the horizontal axis.
**ADC TEST OCTAL LABEL 221, 222 and 223 OUTPUT**  **VANE POSITION** 0 Degrees +/- 0.75 0 Degrees +10 Degrees +/- 0.75 +10 Degrees -10 Degrees +/- 0.75 -10 Degrees 7. If you cannot get the values given in the table, replace the AOA sensor. Refer to 747-400 AMM 34-12-03 as an accepted procedure. 8. If necessary do steps 4. thru 7. to test the other AOA sensor. 9. Put the airplane back to a serviceable condition.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. June 04, 2008 747-34-2925 25 of 26 **BOEING SERVICE BULLETIN 747-34-2925 FIGURE 1: ANGLE OF AIRFLOW SENSOR - INSPECTION**  **(SHEET 1 OF 1)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. June 04, 2008 747-34-2925 26 of 26 **BOEING SERVICE BULLETIN 747-34-2925**