# Boeing Alert Service Bulletin 747-78A2166: Revision 3

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- Document: [Boeing Alert Service Bulletin 747-78A2166](https://openairdocs.org/service-documents/boeing/747-78a2166.md)
- Title as filed: U.S. DOT/FAA - SB-747-78A2166-03
- Pages: 26
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### Page 1

July 24, 1997
Revision 3 July 29, 2004 747-78A2166
BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. 1o f2 6
Commercial
Airplane
Group 747
Service Bulletin
Number: 747-78A2166
Date: July 24, 1997
Revision 3 July 29, 2004
ATA System: 7830
SUBJECT: EXHAUST (CF6-80C2 Engines) - Thrust Reverser - Thrust Reverser Control System -
Center Drive Unit (CDU) Cone Brake Integrity Test
BOEING PROPRIETARY, CONFIDENTIAL, AND/OR TRADE SECRET
Copyright © 1997 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Unpublished Work - All Rights Reserved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, BBJ, DC-8, DC-9,
DC-10, MD-10, MD-11, MD-80, MD-88, MD-90, and the red-white-and-blue 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.

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Table of Contents
July 24, 1997
Revision 3 July 29, 2004 747-78A2166
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BOEING SERVICE BULLETIN 747-78A2166
Table of Contents
R e v i s i o n T r a n s m i t t a l S h e e t .........................................5
S u m m a r y .............................................7
1 . P L A N N I N G I N F O R M A T I O N ..................................... 1 1
A . E f f e c t i v i t y ............................................ 1 1
1 . A i r p l a n e s ......................................... 1 1
2 . S p a r e s A f f e c t e d ...................................... 1 6
B . C o n c u r r e n t R e q u i r e m e n t s................................... 1 6
C . R e a s o n ............................................ 1 6
D . D e s c r i p t i o n ........................................... 1 7
E . C o m p l i a n c e ........................................... 1 7
F . A p p r o v a l............................................ 1 8
G . M a n p o w e r ........................................... 1 8
H . W e i g h t a n d B a l a n c e C h a n g e s................................. 1 8
I . E l e c t r i c a l L o a d D a t a...................................... 1 8
J . R e f e r e n c e s ........................................... 1 8
1 . E x i s t i n g D a t a : ....................................... 1 8
2. Data supplied with this Service Bulletin: . . . . . . . . . . . . . . . . . . . . . . . . . 19
3. Installation Drawings Used in the Preparation of this Service Bulletin: . . . . . . . . . . 19
K . P u b l i c a t i o n s A f f e c t e d ...................................... 1 9
L . I n t e r c h a n g e a b i l i t y a n d I n t e r m i x a b i l i t y o f P a r t s......................... 1 9
2 . M A T E R I A L I N F O R M A T I O N ..................................... 2 1
A . M a t e r i a l - P r i c e a n d A v a i l a b i l i t y ................................. 2 1
B . I n d u s t r y S u p p o r t I n f o r m a t i o n .................................. 2 1
C . P a r t s N e c e s s a r y F o r E a c h A i r p l a n e.............................. 2 1
1 . K i t s / P a r t s : ......................................... 2 1
2 . P a r t s a n d M a t e r i a l s S u p p l i e d b y t h e O p e r a t o r :...................... 2 1
3 . P a r t s M o d i f i e d a n d R e i d e n t i f i e d : ............................. 2 1
4 . P a r t s R e m o v e d a n d N o t R e p l a c e d : ............................ 2 1
D . P a r t s N e c e s s a r y t o C h a n g e S p a r e s.............................. 2 1
E . S p e c i a l T o o l i n g - P r i c e a n d A v a i l a b i l i t y ............................. 2 1
F . S p e c i a l T o o l i n g N e c e s s a r y t o d o t h i s S e r v i c e B u l l e t i n ..................... 2 1
3 . A C C O M P L I S H M E N T I N S T R U C T I O N S ............................... 2 3
A . G E N E R A L I N F O R M A T I O N .................................. 2 3
B. WORK INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
FIGURE 1: CDU MANUAL BRAKE RELEASE LEVER, LOCKOUT PLATE AND DRIVE PAD LOCATIONS
26

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Table of Contents
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BOEING SERVICE BULLETIN 747-78A2166
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Commercial
Airplane
Group 747
Service Bulletin
Number: 747-78A2166 Revision Transmittal Sheet
Date: July 24, 1997
Revision 3 July 29, 2004
ATA System: 7830
SUBJECT: EXHAUST (CF6-80C2 Engines) - Thrust Reverser - Thrust Reverser Control System -
Center Drive Unit (CDU) Cone Brake Integrity Test
This revision includes all pages of the service bulletin.
COMPLIANCE INFORMATION RELATED TO THIS REVISION
Federal Aviation Administration (FAA) Airworthiness Directive (AD) 2003-16-16, Amendment 39-13269, is
related to this service bulletin revision. AD 2003-16-16, Amendment 39-13269 supersedes AD 2000-09-03.
No airplanes were added to this service bulletin effectivity.
No more work is necessary on airplanes changed as shown in the Revision 2 of this service bulletin.
REASON FOR REVISION
This revision is sent to remove reference "767" and add reference "747/747-400" in Paragraph 3.B.1.a,
Accomplishment Instructions.
Paragraph 1.A., Effectivity, shows changes of airplane operators. Each operator should examine the Effectivity
paragraph for changes.
Vertical lines are put on the left edge of each page, except in Paragraph 1.A., Effectivity, to show the location
of important changes.
Pages with no vertical lines have no important changes.
REVISION HISTORY
Initial Release: July 24, 1997
Revision 1: October 9, 1997
Revision 2: March 15, 2001
Revision 3: July 29, 2004

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Commercial
Airplane
Group 747
Service Bulletin
Number: 747-78A2166 Summary
Date: July 24, 1997
Revision 3 July 29, 2004
ATA System: 7830
SUBJECT: EXHAUST (CF6-80C2 Engines) - Thrust Reverser - Thrust Reverser Control System -
Center Drive Unit (CDU) Cone Brake Integrity Test
CONCURRENT REQUIREMENTS
None
BACKGROUND
This inspection will make sure that the center drive unit (CDU) cone brake continues to provide holding torque
against an in-flight thrust reverser deployment.
Two operators have returned five CDU's to the vendor AlliedSignal because of low holding torque. The CDU's
had accumulated between 3,400 and 3600 flight hours. AlliedSignal is currently analyzing the returned units to
determine the cause of low holding torque.
The cone brake consists of a semi-stationary, spring loaded, friction cone and its rotating mating cone mounted
on the CDU, air motor shaft. The brake is disengaged by a pivoted lever, actuated by the translation of the
directional control valve (DCV), actuator piston. While the brake is released, it will allow free rotation of the air
motor in the direction to stow and deploy the reverser. The cone brake ensures against rotation of the CDU air
motor to deploy the reverser when it is engaged by the translation of the DCV actuation piston.
Currently, the CDU cone brake is required to be inspected at 1,000 flight hour intervals. Reducing the inspection
interval for the CDU, cone brake from 1,000 to 650 flight hours will make sure that the CDU cone brake
continues to provide holding torque against an in-flight, thrust reverser deployment.
Boeing Service Related Problem (SRP) 747-SRP-78-0036 is related to this service bulletin.
ACTION
For Group 1 airplanes that have incorporated Boeing Service Bulletin 747-78-2151 or 747-78-2144, and on
Group 2 airplanes, on each thrust reverser half, do a functional test on the Electro-Mechanical brake and CDU
cone brake to verify the holding torque. Repeat this test every 1,000 flight hours.
For Group 1 airplanes that have not incorporated Boeing Service Bulletin 747-78-2151 or 747-78-2144, on each
thrust reverser half, do a functional test on the CDU cone brake to verify the holding torque. Repeat this test
every 650 flight hours.

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BOEING SERVICE BULLETIN 747-78A2166
EFFECTIVITY
All 747/747-400 airplanes powered by CF6-80C2 engines.
COMPLIANCE
Boeing recommends the operators do this service bulletin within 650 flight hours after receipt of this service
bulletin.
For Group 1 airplanes that have not incorporated Boeing Service Bulletin 747-78-2151 or 747-78-2144, Boeing
recommends the operators repeat the CDU cone brake tests every 650 flight hours.
For Group 1 airplanes on which Boeing Service Bulletin 747-78-2151 or 747-78-2144 have been incorporated,
and on Group 2 airplanes, Boeing recommends the operators repeat the Electro-Mechanical brake and the CDU
cone brake tests every 1,000 flight hours.
Federal Aviation Administration (FAA) Airworthiness Directive (AD) 2003-16-16, Amendment 39-13269, is
related to this service bulletin. AD 2003-16-16, Amendment 39-13269 supersedes AD 2000-09-03.
INDUSTRY SUPPORT INFORMATION
Boeing warranty remedies are not available for the inspection given in this service bulletin.
MANPOWER
MATERIAL INFORMATION
None
Total Task Hours Elapsed Hours
12 6

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BOEING SERVICE BULLETIN 747-78A2166
FOR EACH THRUST REVERSER HALF:
DO A FUNCTIONAL TEST ON THE
CENTER DRIVE UNIT (CDU) CONE BRAKE
ELECTRO-MECHANICAL BRAKE
DO A FUNCTIONAL TEST ON THE
FOR EACH THRUST REVERSER HALF:
LEFT SIDE SHOWN,
RIGHT SIDE OPPOSITE
S11892

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BOEING SERVICE BULLETIN 747-78A2166
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Commercial
Airplane
Group 747
Service Bulletin
Number: 747-78A2166
Date: July 24, 1997
Revision 3 July 29, 2004
ATA System: 7830
SUBJECT: EXHAUST (CF6-80C2 Engines) - Thrust Reverser - Thrust Reverser Control System -
Center Drive Unit (CDU) Cone Brake Integrity Test
1. PLANNING INFORMATION
A. Effectivity
1. Airplanes
Note: This service bulletin is for airplanes indentified below. The effectivity list shown below is
complete for airplanes through line number 1348. However, airplanes after line number
1348 are also affected by this service bulletin.
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.
GROUP CONDITION DESCRIPTION
1 - 747-200/300/400 airplanes with CF6-80C2 engines.
1 747-200/300/400 airplanes with CF6-80C2 engines
that have been modified in accordance with Boeing
Service Bulletin 747-78-2151 or 747-78-2144 or
equivalent modification (Production Revision Record
PRR 80452-101R and -102) incorporated in
production.
2 747-200/300/400 airplanes with CF6-80C2 engines
that have not been modified in accordance with Boeing
Service Bulletin 747-78-2151 or 747-78-2144 or
equivalent modification (Production Revision Record
PRR 80452-101R and -102) incorporated in
production.
2 - 747-400 airplanes with CF6-80C2 engines production
line number 1064 through 1348.

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BOEING SERVICE BULLETIN 747-78A2166
Airplane models:
747-200B 747-300 747-400 747-400D
747-400F
IDENTIFICATION BY CUSTOMER, CUSTOMER CODE, GROUP AND VARIABLE NUMBER
AEROLINEAS ARGENTINAS (ARG)
1 RT704
AIR ATLANTA ICELANDIC (AID)
1 RS332–RS333
AIR CANADA (ACN)
1 RT701
AIR FRANCE (AFA)
1 RT071–RT075 RT121 RT591 RT711–RT716
2 RL671–RL674 RM401–RM403
AIR INDIA (AIN)
1 RS781–RS782
AIR NAMIBIA (NAM)
2 RT137
AIR NEW ZEALAND (ANZ)
1 RT703 RT932
2 RM082 RM191–RM192
AIR PULLMANTUR (PUL)
1R S 3 3 1
ALL NIPPON AIRWAYS (ANA)
1 RT751–RT755 RT776–RT777 RU831–RU840
2 RM231–RM233 RT756–RT757 RU841
AMIRI FLIGHT (ABD)
2R M 0 8 4
ASIANA AIRLINES (AAR)
1 RR746 RT131–RT134 RU032
2 RM071 RM861–RM862 RR747–RR748 RT135–RT136
ATLAS AIR (TLS)
2 RM891–RM899 RM901–RM906
BAHRAIN ROYAL FLIGHT (BHR)
2R M 4 2 6
BOEING (TBC)
1 RT021–RT022

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BOEING SERVICE BULLETIN 747-78A2166
CARGOLUX AIRLINES (CLX)
1 RR701 RR721–RR722
2 RR723–RR724
CHINA AIRLINES (CHI)
2 RL411–RL425
EVA AIR (EVA)
1 RT161–RT166 RT951–RT954
2 RL401–RL403 RM116–RM117 RT167–RT168 RT955
GARUDA INDONESIA (GIA)
1 RT931 RU061–RU062
GOVERNMENT OF JAPAN (JAG)
1 RT681–RT682
JAPAN AIRLINES (JAL)
1 RT641–RT657 RT861–RT864 RT966–RT967 RU801–RU809
2 RM126–RM132 RM316–RM318
KLM - ROYAL DUTCH AIRLINES (KLM)
1 RT001–RT011 RT531–RT535
2 RL681–RL683 RM801–RM803 RT012–RT014
KUWAIT AIRWAYS (KUW)
1 RT151
LUFTHANSA GERMAN AIRLINES (DLH)
1 RT041–RT047 RT431–RT439 RT441
2 RM001–RM007 RT442–RT447
NISSHO IWAI CORPORATION (ZNY)
1 RT702
OMAN ROYAL FLIGHT (RFO)
2R M 0 1 0
PHILIPPINE AIRLINES (PAL)
1 RU051–RU052 RU059–RU060
2 RT152
POLAR AIR CARGO (PAO)
2 RL651–RL655
QANTAS (QAN)
1 RT741–RT742 RU031
2 RF001–RF006
ROYAL AIR MAROC (RAM)
1 RT717

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BOEING SERVICE BULLETIN 747-78A2166
S583 (583)
1 RD166–RD167
SAUDI ARABIAN AIRLINES (SVA)
2 RM156–RM158 RU101–RU102
SOUTH AFRICAN AIRWAYS (SAA)
2R M 0 8 1 R M 0 8 3
THAI AIRWAYS INTERNATIONAL (TII)
1 RS341–RS342 RT691–RT698
2 RM026–RM030 RM431 RT699 RT801–RT803
THE SULTAN'S FLIGHT (BWN)
1 RT440
US AIR FORCE (USF)
2R M 9 1 1
VIRGIN ATLANTIC AIRWAYS (VAA)
1 RT945–RT946
2 RM051–RM053 RM351–RM355 RT947–RT949
IDENTIFICATION BY VARIABLE NUMBER
Variable Group
RD166–RD167 1
RF001–RF006 2
RL401–RL403 2
RL411–RL425 2
RL651–RL655 2
RL671–RL674 2
RL681–RL683 2
RM001–RM007 2
RM010 2
RM026–RM030 2
RM051–RM053 2
RM071 2
RM081–RM084 2
RM116–RM117 2
RM126–RM132 2
RM156–RM158 2
RM191–RM192 2
RM231–RM233 2
RM316–RM318 2
RM351–RM355 2

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BOEING SERVICE BULLETIN 747-78A2166
RM401–RM403 2
RM426 2
RM431 2
RM801–RM803 2
RM861–RM862 2
RM891–RM899 2
RM901–RM906 2
RM911 2
RR701 1
RR721–RR722 1
RR723–RR724 2
RR746 1
RR747–RR748 2
RS331–RS333 1
RS341–RS342 1
RS781–RS782 1
RT001–RT011 1
RT012–RT014 2
RT021–RT022 1
RT041–RT047 1
RT071–RT075 1
RT121 1
RT131–RT134 1
RT135–RT137 2
RT151 1
RT152 2
RT161–RT166 1
RT167–RT168 2
RT431–RT441 1
RT442–RT447 2
RT531–RT535 1
RT591 1
RT641–RT657 1
RT681–RT682 1
RT691–RT698 1
RT699 2
RT701–RT704 1
RT711–RT717 1
RT741–RT742 1
Variable Group

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BOEING SERVICE BULLETIN 747-78A2166
2. Spares Affected
None
B. Concurrent Requirements
None
C. Reason
This inspection will make sure that the center drive unit (CDU) cone brake continues to provide holding
torque against an in-flight thrust reverser deployment.
Two operators have returned five CDU's to the vendor AlliedSignal because of low holding torque. The
CDU's had accumulated between 3,400 and 3600 flight hours. AlliedSignal is currently analyzing the
returned units to determine the cause of low holding torque.
The cone brake consists of a semi-stationary, spring loaded, friction cone and its rotating mating cone
mounted on the CDU, air motor shaft. The brake is disengaged by a pivoted lever, actuated by the
translation of the directional control valve (DCV), actuator piston. While the brake is released, it will
allow free rotation of the air motor in the direction to stow and deploy the reverser. The cone brake
ensures against rotation of the CDU air motor to deploy the reverser when it is engaged by the
translation of the DCV actuation piston.
Currently, the CDU cone brake is required to be inspected at 1,000 flight hour intervals. Reducing the
inspection interval for the CDU, cone brake from 1,000 to 650 flight hours will make sure that the CDU
cone brake continues to provide holding torque against an in-flight, thrust reverser deployment.
RT751–RT755 1
RT756–RT757 2
RT776–RT777 1
RT801–RT803 2
RT861–RT864 1
RT931–RT932 1
RT945–RT946 1
RT947–RT949 2
RT951–RT954 1
RT955 2
RT966–RT967 1
RU031–RU032 1
RU051–RU052 1
RU059–RU062 1
RU101–RU102 2
RU801–RU809 1
RU831–RU840 1
RU841 2
Variable Group

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BOEING SERVICE BULLETIN 747-78A2166
Boeing Service Related Problem (SRP) 747-SRP-78-0036 is related to this service bulletin.
Revision 1 was sent to change the inspection interval for the CDU cone brake test from 600 to 650
flight hours to coincide with operators maintenance schedule.
Revision 2 adds the inspection interval of the Electro-Mechanical brake and CDU cone brake, for
airplanes equipped with thrust reversers, that have been modified in accordance with Boeing Service
Bulletin 747-78-2151or 747-78-2144 or after the equivalent modification (Production Revision Record
PRR 80452-101R and -102) incorporated in production. Revise the service bulletin effectivity to add
Group 2 airplanes which is included all 747-400 airplanes (including future 747-400 airplanes) with
CF6-80C2 engines after production line number 1060. Also, the Industry Support Information
statement has been changed.
Revision 3 is sent to remove reference "767" and add reference "747/747-400" in Paragraph 3.B.1.a.,
Accomplishment Instructions.
D. Description
For Group 1 airplanes that have incorporated Boeing Service Bulletin 747-78-2151 or 747-78-2144
and on Group 2 airplanes, on each thrust reverser half, do a functional test on the Electro-Mechanical
brake and CDU cone brake to verify the holding torque. Repeat this test every 1,000 flight hours.
For Group 1 airplanes that have not incorporated Boeing Service Bulletin 747-78-2151 or 747-78-
2144, on each thrust reverser half, do a functional test on the CDU cone brake to verify the holding
torque. Repeat this test every 650 flight hours.
Revision 1 - No more work is necessary on airplanes changed as shown in the initial release of this
service bulletin.
Revision 2 - More work is necessary on airplanes changed as shown in the Revision 1 of this service
bulletin.
Revision 3 - No more work is necessary on airplanes changed as shown in the Revision 2 of this
service bulletin.
E. Compliance
Boeing recommends the operators do this service bulletin within 650 flight hours after receipt of this
service bulletin.
For Group 1 airplanes that have not incorporated Boeing Service Bulletin 747-78-2151 or 747-78-
2144, Boeing recommends the operators repeat CDU cone brake test every 650 flight hours.
For Group 1 airplanes on which Boeing Service Bulletin 747-78-2151 or 747-78-2144 has been
incorporated and on Group 2 airplanes, Boeing recommends the operators repeat the Electro-
Mechanical brake and CDU cone brake tests every 1,000 flight hours.
Federal Aviation Administration (FAA) Airworthiness Directive (AD) 2003-16-16, Amendment 39-
13269, is related to this service bulletin. AD 2003-16-16, Amendment 39-13269 supersedes AD 2000-
09-03.

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F. Approval
This service bulletin was examined by the Federal Aviation Administration (FAA). The changes
specified in this service bulletin comply with the applicable Federal Aviation Regulations (FAR) and
are FAA approved. This service bulletin and the FAA approval were based on the airplane in its
original Boeing delivery configuration or as modified by other FAA 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.
This service bulletin has been approved by the FAA. In addition, the Manager of the FAA Seattle
Aircraft Certification Office approves the action inspection defined in this service bulletin as an
alternative method of compliance to the requirements of paragraph (e) and (j) of AD 2003-16-16. All
provisions of AD 2003-16-16 that are not specifically referenced in the above sentence remain fully
applicable and must be complied with.
G. Manpower
Approximately 12 man-hours and 2 persons are necessary to do this test for each airplane.
Time does not include CDU replacement.
This estimate is for direct labor only, done by an experienced crew. Adjust the estimate with operator
man-hour data if necessary. The estimate does not include lost time. These are some examples of
lost time:
— Time to adjust to the workplace
— T i m et os c h e d u l et h ew o r k
— T i m et oe x a m i n et h ew o r k
— T i m et oc u r et h em a t e r i a l s
— T i m et om a k et h ep a r t s
— Time to find the tools.
H. Weight and Balance Changes
None
I. Electrical Load Data
Not applicable
J. References
1. Existing Data:
a. Service Related Problem (SRP) 747-SRP-78-0036
b. 747/747-400 Maintenance Manual (AMM) Subject 71-11-04, 78-31-21
c. Boeing Service Bulletin 747-78A2113, "Exhaust (CF6-80C2 Engines) - Thrust Reverser -
Thrust Reverser Control System - Operational Test"

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d. Boeing Service Bulletin 747-78A2130, "Exhaust (CF6-80C2 Engines With PMC) - Thrust
Reverser - Thrust Reverser Control System - Operational Test"
e. Boeing Service Bulletin 747-78-2144, "Exhaust (CF6-80C2 PMC Engines) - Thrust
Reverser - Thrust Reverser Actuation System (TRAS) Brake Installation"
f. Boeing Service Bulletin 747-78-2151, "Exhaust (CF6-80C2 Engines) - Thrust Reverser -
Thrust Reverser Hydraulic Actuator - Synchronous Lock Installation"
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
Refer to Paragraph 2.C., Parts Necessary For Each Airplane, for interchangeability and intermixability
information.

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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 inspection given in this service bulletin.
C. Parts Necessary For Each Airplane
1. Kits/Parts:
None
2. Parts and Materials Supplied by the Operator:
Note: Part quantity dependent on test results.
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.
Part Number QTY Name Notes
126784-() 8C e n t e r D r i v e U n i t ( a )
(a) Replace this part when the sleeve translates to deploy with a torque less than 15 pound
inches.

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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. The numbered paragraphs contain the test to be accomplished at the specific interval.
2. Obey all of the warnings and cautions given in the specified manual sections.
3. Refer to Compliance Paragraph for recommendation and repeat inspection requirements.
4. For Group 1 airplanes that have not incorporated Boeing Service Bulletin 747-78-2151 or
747-78-2144, repeat CDU cone brake test every 650 flight hours.
For Group 1 airplanes on which Boeing Service Bulletin 747-78-2151 or 747-78-2144 has
been incorporated and on Group 2 airplanes, repeat the Electro-Mechanical brake and
CDU cone brake tests every 1,000 flight hours.
B. WORK INSTRUCTIONS
1. Do the functional test on both thrust reverser for the Electro-Mechanical brakes of both engines
as follows:
a. Open the engine fan cowl panels as shown in 747/747-400 Maintenance Manual Subject
71-11-04 or your own equivalent procedure.
b. Do a check of the running torque of the thrust reverser system:
(1) Manually extend the thrust reverser six inches and measure the running torque. Make
sure the torque is less than 10 pound-inches.
c. Do a check of the electro-mechanical brake holding torque:
(1) Make sure the thrust reverser translating cowl is extended at least one inch.
(2) Make sure the CDU lock handle is released.
(3) Pull down on the manual release handle on the electro-mechanical brake until the
handle fully engages the retaining clip.
Note: This will lock the electro-mechanical brake.
(4) With the manual drive lockout cover removed from the CDU, install a 1/4-inch
extension tool and dial -type torque wrench into the drive pad.
Note: You will need a 24-inch extension to provide adequate clearance for the torque

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wrench.
(5) Apply 90 pound-inches of torque to the system.
(a) The electro-mechanical brake system is working correctly if the torque is reached
before you turn the wrench 450 degrees (1-1/4 turns).
(b) If the flexshaft turns more than 450 degrees (1-1/4 turns) before you reach the
specified torque, you must replace the long flexshaft between the CDU and the
upper angle gearbox.
(c) If you do not get 90 pound-inches of torque, inspect the short flexshaft between
the upper angle gearbox and the electro-mechanical brake. If the flexshaft is
twisted, broken or otherwise damaged, replace the flexshaft and repeat (5). If you
still do not get 90 pound-inches of torque, you must replace the electro-
mechanical brake.
(6) Release the torque by turning the wrench in the position direction until you read zero
pound-inches.
(a) If the wrench does not turn to within 30 degrees of initial starting point, you must
replace the long flexshaft between the CDU and upper angle gearbox.
d. Fully retract the thrust reverser.
e. Repeat this procedure on other reverser half and on the remaining engines.
f. End the Electro-Mechanical brake check.
2. For Group 1 airplanes on which Boeing Service Bulletin 747-78-2151 or 747-78-2144 has been
incorporated and on Group 2 airplanes, repeat the Electro-Mechanical brake test at 1,000 flight
hours intervals
3. Do the functional test on both thrust reverser for the Center Drive Unit (CDU) cone brakes of all
four engines as follows:
a. Open the engine fan cowl panels as shown in 747/747-400 Maintenance Manual Subject
71-11-04 or your own equivalent procedure.
b. Pull up on the manual release handle to unlock the electro-mechanical brake (if so
equipped).
c. Pull the manual release lever on the CDU to release the cone brake. Refer to Figure 1 for
location.
Note: This will release the pre-load tension that may occur during a stow cycle.
d. Return the manual brake release lever to the locked position to engage the cone brake.
Refer to Figure 1 for location.
e. Remove the two bolts that hold the lockout plate to the CDU and remove the lockout plate.
Refer to Figure 1 for location.

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f. Install a 1/4-inch drive and a dial-type torque wrench into the CDU drive pad.
WARNING: DO NOT USE MORE THAN 100 POUND-INCHES OF TORQUE WHEN
CARRYING OUT THIS CHECK. EXCESSIVE TORQUE WILL DAMAGE THE
CDU.
g. Turn the torque wrench to try to manually extend the translating cowl until you get at least
15 pound-inches of torque.
Note: The cone brake prevents movement in the extend direction only. If you try to measure
the torque in the retract direction, you will get a false reading.
h. If the sleeve translates to deploy with a torque less than 15 pound inches, you must replace
the CDU as shown in 747/747-400 Maintenance Manual Subject 78-31-21.
i. Reinstall the lockout plate.
j. Fully retract the thrust reverser.
k. Pull down on the manual release handle on the electro-mechanical brake until the handle
fully engages the retaining clip (if so equipped).
Note: This will lock the electro-mechanical brake.
l. Repeat this procedure on other reverser half and on the remaining engines.
m. Close the engine fan cowl panels as shown in 747/747-400 Maintenance Manual Subject
71-11-04 or your own equivalent procedure.
n. End the CDU cone brake check.
4. For Group 1 airplanes that have not incorporated Boeing Service Bulletin 747-78-2151 or 747-
78-2144, repeat CDU cone brake test every 650 flight hours.
5. For Group 1 airplanes on which Boeing Service Bulletin 747-78-2151 or 747-78-2144 has been
incorporated and on Group 2 airplanes, repeat the CDU cone brake tests every 1,000 flight
hours.

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FIGURE 1: CDU MANUAL BRAKE RELEASE LEVER, LOCKOUT PLATE AND DRIVE PAD LOCATIONS
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BOEING SERVICE BULLETIN 747-78A2166
FIGURE 1: CDU MANUAL BRAKE RELEASE LEVER, LOCKOUT PLATE AND DRIVE PAD LOCATIONS
ELECTRO-MECHANICAL BRAKE
UPPER ANGLE
GEAR BOX
(LEFT SIDE SHOWN,
RIGHT SIDE TURNED 180 DEGREES)
CENTER
(CDU)
DRIVE UNIT
DRIVE PAD
PLATE AND
LOCKOUT
BRAKE RELEASE
CDU MANUAL
LEVER
CENTER DRIVE UNIT
S11864
(SHEET 1 OF 1)

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