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737-100/200/200C/300/400/500

AIRWORTHINESS LIMITATIONS (AWLs) AND

 CERTIFICATION MAINTENANCE REQUIREMENTS (CMRs)

D6-38278-CMR

JULY 2011

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.

COMPILED AND PUBLISHED BY:

MAINTENANCE PROGRAMS ENGINEERING

COMMERCIAL AVIATION SERVICES

BOEING COMMERCIAL AIRPLANE GROUP

A DIVISION OF THE BOEING COMPANY

SEATTLE, WASHINGTON USA

This document has EAR data with an Export Control Classification Number (ECCN) of 9E991.

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.

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TABLE OF CONTENTS

REVISIONS .................................................................................................................................................................................................................................. 9.0-5

LIST OF EFFECTIVE PAGES .....................................................................................................................................................................................................9.0-11

A. SCOPE................................................................................................................................................................................................................................... 9.0-13

B. CERTIFICATION MAINTENANCE REQUIREMENTS (CMRS) ............................................................................................................................................. 9.0-13

PAGE FORMAT: SYSTEMS MAINTENANCE PROGRAM..................................................................................................................................................... 9.0-17

CERTIFICATION MAINTENANCE REQUIREMENTS TASKS............................................................................................................................................... 9.0-18

C. FUEL SYSTEMS AIRWORTHINESS LIMITATIONS.............................................................................................................................................................. 9.0-19

PAGE FORMAT: SYSTEMS AIRWORTHINESS LIMITATIONS ............................................................................................................................................. 9.0-21

737-100, -200, -200C MAINTENANCE PLANNING DATA – AIRWORTHINESS LIMITATIONS – FUEL SYSTEMS ............................................................ 9.0-22

737-300, -400, -500 MAINTENANCE PLANNING DATA – AIRWORTHINESS LIMITATIONS – FUEL SYSTEMS............................................................... 9.0-32

D. AIRWORTHINESS LIMITATIONS – NITROGEN GENERATION SYSTEMS ........................................................................................................................ 9.0-44

AIRWORTHINESS LIMITATIONS – NITROGEN GENERATION SYSTEM TASKS............................................................................................................... 9.0-45

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REVISIONS

REVISION AND REVISION DESCRIPTION APPROVAL

FEBRUARY 2003

Original Release - Added CMR 27-CMR-01 applicable to airplanes accomplishing 

Service Bulletin 737-27-1252 (737-100/200/200C) and

737-27-1255 (737-300/400/500).

Submitted by: S. Pierini (Boeing) Approved by:

(Seattle FAA ACO)

NOVEMBER 2004

Added CMR 52-CMR-01 to perform a functional check of the flight deck door locking 

and unlocking latch bolt mechanism on the decompression panel. 

Deleted “RELATED MRBR ITEM NUMBER” column as it is no longer necessary.

Submitted by: G.Palafox(Boeing) Approved by:

MARCH 2006

Added Section “C” of Airworthiness Limitations to satisfy maintenance requirements 

introduced by 25.981 and Special Federal Aviation Regulation (SFAR) No. 88.

Submitted by: Approved by:

MAY 2006

Revised AWL Revision Process paragraphs in the Applicability column of the AWL 

tables to include -100, -200, and -200C models.

Revised the applicability of 28-AWL-05, 28-AWL-09, 28-AWL-14, 28-AWL-18, and 28-

AWL-20 by adding the -200C model.

Submitted by: Approved by:

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REVISION AND REVISION DESCRIPTION APPROVAL

SEPTEMBER 2006

Added a functional check of the center tank Fuel Boost Pump Auto Shutoff System 

Number 28-AWL-20. Applicable to 737-300/400/500 airplanes that have incorporated 

Service Bulletin 737-28A1216. 

Added a functional check of the auxiliary fuel tank Boost Pump Auto Shutoff System 

Number 28-AWL-21. Applicable to 737-300/-400 airplanes with Boeing certified 

auxiliary fuel tanks installed, that have incorporated Service Bulletin 737-28A1216.

Added a functional check of the center tank Fuel Boost Pump Auto Shutoff System 

Number 28-AWL-21. Applicable to 737100/-200 airplanes that have incorporated 

Service Bulletin 737-28A1228.

Added a functional check of the auxiliary fuel tank Boost Pump Auto Shutoff System 

Number 28-AWL-22. Applicable to 737-100/-200 airplanes with Boeing certified 

auxiliary fuel tanks installed, that have incorporated Service Bulletin 737-28A1228.

Deleted the RELATED MRBR ITEM NUMBER column information from the PAGE 

FORMAT: SYSTEMS MAINTENANCE PROGRAM page since this information does not 

apply to this table.

Revised 737-100/200 28-AWL-14 to indicate that a float assembly must be used.

Submitted by: Approved by:

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REVISION AND REVISION DESCRIPTION APPROVAL

NOVEMBER 2007

Revised Section B. paragraph on Exceptional Short-Term Extensions to clarify process 

and notification requirements.

Revised the first sentence of Section C. Airworthiness Limitations - Fuel Systems by 

adding “scheduled inspections and design limitations”, and revised the information on 

Exceptional Short-Term Extensions to clarify notification requirements.

Revised the heading in Section C to read “Page Format: Fuel Systems Airworthiness 

Limitations" instead of “Page Format: Airworthiness Limitations”.

For 737-100/200:

Revised Airworthiness Limitation (AWL) 28-AWL-19 to add Ground Fault Interrupter 

(GFI) relays to the limitation that restricts resetting of fuel pump circuit breakers.

Added new AWL 28-AWL-23, a yearly check of the Boost Pump GFI. This AWL is 

applicable to airplanes that have incorporated Service Bulletin 737-28A1212.

For 737-300/400/500:

Revised AWL 28-AWL-19 to add GFI relays to the limitation that restricts resetting of 

fuel pump circuit breakers.

Added new AWL 28-AWL-22, a yearly check of the Boost Pump GFI. This AWL is 

applicable to airplanes that have incorporated Service Bulletin 737-28A1212.

Submitted by: E. B. Lange 

(Boeing)

Approved by: Phillip Forde (FAA)

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REVISION AND REVISION DESCRIPTION APPROVAL

MARCH 2008

Revised 28-AWL-01 to remove 36000FH task interval limitation based upon 

engineering review and operator maintenance practice and removed body station and 

buttock line text and replaced with "per AMM 28-11-00".

Revised 28-AWL-03 to reflect the new maximum loop resistance values associated with 

the lightning protection of the unpressurized FQIS wire bundle installations so as to 

satisfy the Airworthiness Limitation Instructions required by SFAR 88. Also removed 

the joint resistance values and 36000FH task interval limitation based upon engineering 

review and operator maintenance practice and removed -100 from the applicability 

column since this AWL does not apply to the 737-100.

Revised 28-AWL-04 to remove -100 from the applicability column since this AWL does 

not apply to the 737-100.

Revised 28-AWL-18 by replacing both Service Bulletin (SB) 737-28A1120 and 

Airworthiness Directive (AD) 99-21-15 with superseded SB 737-28A1263 and AD 2007-

24-02. Also remove the following text "or an additional Teflon sleeve" and "Non 

jacketed wiring and double sleeves".

Submitted by: John Sabolchy 

(Boeing)

Approved by: Dorr Anderson (FAA)

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REVISION AND REVISION DESCRIPTION APPROVAL

MAY 2009

Added Section D. front matter for the Airworthiness Limitations-Nitrogen Generation 

System (NGS) requirements and also added 47-AWL-01 thru 47-AWL-05 NGS tasks. 

These items apply to the 737-400 only.

Revised 737 (12345) CMR tasks to be consistent with AMOCs since December, 2008, 

including updating CMM references such as Vendor and Cage Code.

Revised 28-AWL-02 (12345) by updating text in the task description to clarify inspection 

requirements and location.

Revised the task description of 28-AWL-03 (737-12345) by removing the statement "at 

side of body, and" to reflect the original intent of the task requirement.

Revised 28-AWL-04 (12345) by rewording text to clarify task description requirements.

Revised the Task Description for 28-AWL-05 to clarify the intent of the requirement and 

to provide the SWPM reference for installation requirements.

Revised the Task Description for 28-AWL-06 (for 737-345) to clarify the party 

responsible for repairing the Isolated Fuel Quantity Transmitter (IFQT).

Revised the task description of 28-AWL-07, and -12 (737-12345) by adding text to 

provide an alternative to the identified CMM by using the manufacture's production 

procedures. 

Revised 28-AWL-11 (737-12345) with updated Fuel Tank Penetration text per the latest 

FAA AMOC 120S-09-230.

Revised 28-AWL-17 (737-12345) resistance from "1 ohm" to "0.010 (10 milliohms)" to 

correct resistance between the pressure relief valve and the door.

Revised 28-AWL-19 (737-12345) by replacing the text "&" in the task description to "or" 

to clarify the intent of the task.

Revised 28-AWL-20 by adding vendor CMM in task description for clarification.

Added new AWL 28-AWL-23 (737-345), a yearly check to verify the continued 

functionality of the center tank fuel boost pump Power Failed On Protection System.

Added new AWL 28-AWL-24, a yearly check to verify the continued functionality of the 

center tank fuel boost pump Power Failed On Protection System.

Added new AWL 28-AWL-25 (737-12), a yearly check to verify the continued 

functionality of the auxiliary tank fuel boost pump Power Failed On Protection System.

Submitted by: John Sabolchy

 (Boeing)

Approved by: Jeffrey E. Duven

 (Seattle FAA ACO)

SIGNATURE ON FILE

8/13/2009

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REVISION AND REVISION DESCRIPTION APPROVAL

AUGUST 2010

Revised Paragraph D. Airworthiness Limitations – Nitrogen Generation System tasks 

by updating the FAA regulations corresponding to the compliance measures provided in 

the subsequent AWLs.

Revised 47-AWL-01 and 47-AWL-02 by updating the Applicability column to read 

“Airplanes that have incorporated Service Bulletin 737-47-1004 or 737-47-1007.

Revised 47-AWL-01 by updating the Task Description by adding instructions and a Note 

to clarify the procedure and parameters for the maintenance action.

Revised 47-AWL-02 by updating the Task Description to clarify the procedure and 

parameters for the maintenance action of the isolator hose and to replace "per" with 

"refer to".

Revised 47-AWL-03, 47-AWL-04, and 47-AWL-05 by updating the Applicability column 

to read "Airplanes that have incorporated Service Bulletin 737-47-1005 or 737-47-1008.

Revised 47-AWL-04 by replacing "per Boeing AMM 47-43-02" with "(refer to Boeing 

AMM 47-43-02)".

Revised 47-AWL-05 by replacing "(ref AMM ATA 47-21-00)" with "(refer to Boeing AMM 

47-43-02)".

Added 47-AWL-06, an identification of the maintenance standard for the Nitrogen 

Generation System and notice of potential future compliance requirements associated 

with decreased aircraft descent rates.

Submitted by: John Sabolchy

 (Boeing)

Approved by: Robert D. Breneman

 (Seattle FAA ACO)

SIGNATURE ON FILE

12/15/2010

JULY 2011

Revised 47-AWL-03 to incorporate NGS performance features to show compliance with 

14 CFR 26.33.

Submitted by: Mark Arnold

 (Boeing)

Approved by: Ron Landes for

 Robert D. Breneman

 (Seattle FAA ACO)

SIGNATURE ON FILE

8/10/2011

JUL 2011
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A. SCOPE

The scheduled maintenance requirements described in this section result from airplane certification activities with the U.S. Federal Aviation Administration 

(FAA). Accordingly, this FAA approved Certification Maintenance Requirements (CMRs) document is cross-referenced in the Model 737-300/400/500 

Type Certificate Data Sheet. This document satisfies the requirements of FAR 25.571, FAR 25.1529 and Advisory Circular (AC) 25-19 as the controlling 

document for all 737-100/200/200C/300/400/500 CMRs. These maintenance actions are mandatory.

B. CERTIFICATION MAINTENANCE REQUIREMENTS (CMRs)

CMR DEFINITION

As defined by AC 25-19, a CMR is a required periodic task, established during the design certification of the airplane as an operating limitation of the type 

certificate. CMRs usually result from a formal, numerical analysis conducted to show compliance with catastrophic and hazardous failure conditions. 

Additional notes concerning the definition of CMRs:

1. A CMR is intended to detect safety-significant latent (hidden) failures that would, in combination with one or more specific failures or events, result in a 

hazardous or catastrophic failure condition.

2. It is important to note that CMRs are derived from a fundamentally different analysis process than the maintenance tasks and intervals that result from 

the Maintenance Steering Group (MSG-3) Analysis associated with Maintenance Review Board (MRB) activities. MSG-3 Analysis activity produces 

maintenance tasks that are performed for safety, operational, or economic reasons, involving both preventative maintenance tasks, which are performed 

before failure occurs (and are intended to prevent failures), as well as failure-finding tasks. CMRs, on the other hand, are typically failure-finding tasks, 

and exist solely to limit the exposure to otherwise hidden failures. Nevertheless, use of potential failure-finding tasks, such as functional checks and 

inspections, may also be appropriate.

3. CMRs are designed to verify that a certain failure has or has not occurred, and do not provide any preventative maintenance function. CMRs “restart 

the failure clock to zero” for latent failures by verifying that the item has not failed, or caused repair if it has failed. Because the exposure time to a latent 

failure is a key element in the calculations used in a safety analysis performed to show compliance with FAR 25.1309, limiting the exposure time will 

have a significant effect on the resultant overall failure probability of the system. The CMR Task Interval should be designated in terms of flight hours, 

cycles, or calendar time, as appropriate.

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4. The type certification process assumes that the airplane will be maintained in a condition of airworthiness with respect to its certified or properly altered 

condition. The process described in AC 25-19 is not intended to establish normal maintenance tasks that should be defined through the MSG-3 

Analysis process. Neither is this process intended to establish CMRs for the purpose of providing supplemental margins of safety for concerns arising 

late in the type design approval process.

5. CMRs should not be confused with required structural inspection programs and are to be developed by the type certificate applicant to meet the 

inspection requirements for damage tolerance, as required by FAR 25.571 or 25.1529, Appendix H25.4 (Airworthiness Limitations section). CMRs are 

to be developed and administered separately from any structural inspection programs.

CMR TYPES

CMR Tasks are divided into two categories: One Star CMRs (*) and Two Star CMRs (**). They are defined as follows:

1. One Star CMRs (*) – The tasks and intervals specified are mandatory and cannot be changed, escalated, or deleted without the concurrence of the 

FAA Seattle ACO.

2. Two Star CMRs (**) – Task intervals may be adjusted in accordance with each operator’s approved escalation program or an approved reliability 

program in a like manner for any MRB Report task, but may not be deleted without prior Seattle FAA ACO approval.

ESCALATION OF TWO STAR CMRs (**)

All Two Star CMRs (**) can be managed and controlled the same as any MRB Report task; however, they can not be deleted from an operator’s program 

without prior Seattle FAA ACO approval. For operators with approved escalation practices or an approved reliability program, data collection and 

analytical techniques are used to make adjustments to an operator’s maintenance program. It has been demonstrated that the management of a 

maintenance program does not give rise to undue escalations; consequently, the escalation of Two Star CMR (**) intervals within an operator’s 

maintenance program will be properly managed by the operator subject to local regulatory authority approval.

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EXCEPTIONAL SHORT-TERM EXTENSIONS

Since CMR intervals are based on statistical averages and reliability rates, an exceptional short-term extension of 10% for each CMR listed in this 

document may be made without jeopardizing safety. The local regulatory authority (e.g. a Principle Maintenance Inspector) must concur with any 

exceptional short-term extensions before they take place using procedures established with the local regulatory authority in the operators’ manuals. The 

“exceptional short-term extension” process is applicable to CMR intervals. It should not be confused with the operator’s “short-term escalation” program 

for normal maintenance tasks described in the operators’ manuals and in the Flight Standards Handbook 8300.10.

The Seattle FAA ACO has accepted that these exceptional short-term extensions may be granted without consultation with that office:

1. The term “exceptional short-term extension” is defined as an increase in a CMR interval that may be needed to cover an uncontrollable or unexpected 

situation. All CMRs listed in this document have been approved with an exceptional short-term extension of 10%.

2. Repeated use of extensions, either on the same airplane or on similar airplanes in an operator’s fleet, should not be used as a substitute for good 

management practices. Exceptional short-term extensions must not be used for fleet CMR escalation.

After a CMR has experienced an exceptional short-term extension, the CMR interval will revert back to its interval listed in this document. The Seattle FAA 

ACO must approve, prior to its use, any desired extension not explicitly listed above.

This exceptional short-term extension listed above applies to airlines that fall under the United States FAA jurisdiction only. Operators who are not under 

the U.S. FAA jurisdiction should obtain interval extension approvals from their local regulatory agency.

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POST CERTIFICATION CHANGES TO CMRs

Any post certification changes to CMRs should be reviewed by the 737-100/200/200C/300/400/500 Certification Maintenance Coordination Committee 

(CMCC) and approved by the Seattle FAA ACO:

1. Since the purpose of a CMR is to limit the exposure time to a given significant latent failure as part of an engineering analysis of overall system reliability, 

instances of a CMR task repeatedly finding that no failure has occurred may not be sufficient justification for deleting the task or increasing the time 

between repetitive performances of the CMR task. In general, * CMRs are not good candidates for escalation under an operator’s reliability program. 

A * CMR task change or interval escalation can only be made if world fleet service experience indicates that certain assumptions regarding component 

failure rates made early during the engineering analysis were overly conservative, and a re-calculation of system reliability with revised failure rates of 

certain components reveals that the * CMR task or interval may be changed.

2. The introduction of a new CMR or any change to an existing CMR should be reviewed by the same process used during initial certification. It is 

important that operators be afforded the same opportunity to participate that they received during the original certification of the airplane, in order to 

allow the operators to manage their own maintenance programs.

3. In the event that later data provides sufficient basis for relaxation of a CMR (less restrictive actions to be performed), the change may be documented by 

an Seattle FAA ACO approved change to this CMR document.

4. If the requirements of an existing CMR must be increased (more restrictive actions to be performed), it will be implemented by a change to this 

CMR document and enforced by an FAA Airworthiness Directive (AD).

5. After initial aircraft certification, the only basis for adding a new CMR is in association with the certification of design changes.

6. A new CMR created as part of a design change should be part of the approved data for that change and added to this CMR document.

In the event that a CMR is revised, Boeing will document it by preparing a revision to this document that will be approved by the Seattle FAA ACO. This 

revision will then be forwarded to all 737-100/200/200C/300/400/500 operators and the Seattle FAA ACO offices.

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PAGE FORMAT: SYSTEMS MAINTENANCE PROGRAM

COLUMN EXPLANATION

CMR ITEM 

NUMBER

Each task is given a unique CMR Item Number. The first and second digits are the ATA Chapter Number.

TYPE CMR TYPE:

CMRs are categorized into one or two star CMRs based on whether or not they can be escalated by the operator without 

prior Seattle FAA ACO approval.

* Cannot be escalated or deleted without prior Seattle FAA ACO approval.

** Can be escalated based on the operator’s approved program for continued airworthiness based on continuous

 analysis and surveillance; however, these tasks cannot be deleted without prior Seattle FAA ACO approval.

TASK TASK TYPES/CATEGORIES:

LU = Lubrication

SV = Servicing

OP = Operational Check

VC = Visual Check

GV = General Visual Inspection

DI = Detailed Inspection

FC = Functional Check

RS = Restoration

DS = Discard

CMR INTERVAL Task frequencies are specified in terms of a usage parameter such as flight hours, cycles or calendar time.

APPLICABILITY

APL ENG

Applicable Airplane Model and Engine.

TASK 

DESCRIPTION

Description of the task to be performed.

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CERTIFICATION MAINTENANCE REQUIREMENTS TASKS

CMR ITEM 

NUMBER TYPE TASK

CMR

INTERVAL

APPLICABILITY

APL ENG TASK DESCRIPTION

27-CMR-01 * FC 10000 HRS NOTE ALL

Functionally check rudder main PCU Internal leakage in a loaded condition.

Applicability Note: Airplanes that have incorporated Service Bulletins 737-27-1252 

on the 737-100/-200/-200C or 737-27-1255 on the 737-300/400/500.

52-CMR-01 * FC 3,000 FH NOTE ALL

Perform a functional check of the locking and unlocking latch bolt mechanism on the 

flight deck door decompression panel.

Applicability Note: Applicable to airplanes with the Enhanced Flight Deck Security 

Door installed by the customer specific Boeing Service Bulletins.

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C. FUEL SYSTEMS AIRWORTHINESS LIMITATIONS

This section of the Airworthiness Limitations contains an FAA approved program of scheduled inspections and design limitations for operators to 

incorporate into their maintenance program for this type design to meet the new standards and assumptions introduced by § 25.981 and Special Federal 

Aviation Regulation (SFAR) No. 88. SFAR 88 - Fuel Tank System Fault Tolerance Evaluation Requirements and Title 14 Code of Federal Regulations 

§ 25.981 - Fuel Tank Ignition Prevention require maintenance instructions, and control limitations for certain fuel tank critical design configurations. 

Paragraph 2(a) of SFAR 88 requires certain design approval holders of Type Certificates (TCs) and Supplemental Type Certificates (STCs) of large 

transport airplanes to conduct a safety review of the fuel tank systems. The purpose of the safety review is to identify design features that may result in 

development of ignition sources in the fuel tank systems. Fuel System Airworthiness Limitation (AWL) items are mandatory maintenance actions required 

to ensure that unsafe conditions identified by the SFAR 88 safety review do not occur or are not introduced into the fuel tank system as a result of 

configuration changes, repairs, alterations, or deficiencies in the maintenance program throughout the operational life of the airplane. An AWL may be: an 

Airworthiness Limitation Instruction (ALI) or a Critical Design Configuration Control Limitation (CDCCL).

CDCCLs are a means of identifying certain design configuration features intended to preclude a fuel tank ignition source for the operational life of the 

airplane. CDCCLs are mandatory and cannot be changed or deleted without the approval of the Seattle FAA ACO that is responsible for the airplane 

model Type Certificate, or applicable regulatory agency. A critical fuel tank ignition source prevention feature may exist in the fuel system and its related 

installation or in systems that, if a failure condition were to develop, could interact with the fuel system in such a way that an unsafe condition would 

develop without this limitation. Strict adherence to configuration, methods, techniques, and practices as prescribed is required to ensure compliance with 

the CDCCL. Any use of parts, methods, techniques or practices not contained in the applicable CDCCL must be approved by the Seattle FAA ACO that is 

responsible for the airplane model Type Certificate, or applicable regulatory agency.

ALIs identify inspection tasks related to fuel tank ignition source prevention which must be done to maintain the design level of safety for the operational 

life of the airplane. These ALIs are mandatory and cannot be changed or deleted without the approval of the Seattle FAA ACO that is responsible for the 

airplane model Type Certificate, or applicable regulatory agency. Strict adherence to methods, techniques and practices as prescribed is required to 

ensure the ALI is complied with. Any use of methods, techniques or practices not contained in these ALIs must be approved by the Seattle FAA ACO that 

is responsible for the airplane model Type Certificate, or applicable regulatory agency.

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737-12345 AIRWORTHINESS LIMITATIONS/CERTIFICATION MAINTENANCE REQUIREMENTS

USE OF ALTERNATE TOOLS

For AWLs which require use of certain tools, use of alternate tools requires prior approval from the Seattle FAA ACO.

EXCEPTIONAL SHORT-TERM EXTENSIONS

Since AWL intervals are based on estimations of the probability of an event, an exceptional short-term extension for each fuel system AWL listed in this 

document may be made without jeopardizing safety. The local regulatory authority (e.g., a Principle Maintenance Inspector) must concur with any 

exceptional short-term extensions before they take place using procedures established with the local regulatory authority in the operators’ manuals. The 

“exceptional short-term extension” process is applicable to AWL intervals. It should not be confused with the operator’s “short-term escalation” program for 

normal maintenance tasks described in the operators’ manuals and in the Flight Standards Handbook 8300.10.

The Seattle FAA ACO has accepted that these exceptional short-term extensions may be granted without consultation with that office:

1. The term “exceptional short-term extension” is defined as an increase in a fuel system AWL interval that may be needed to cover an uncontrollable or 

unexpected situation. All AWLs listed in this section have been approved with an exceptional short-term extension of 30 days.

2. Repeated use of extensions, either on the same airplane or on similar airplanes in an operator’s fleet, should not be used as a substitute for good 

management practices. Exceptional short-term extensions must not be used for fleet AWL extensions.

After a fuel system AWL has experienced an exceptional short-term extension, the AWL interval will revert back to its interval listed in this document. The 

Seattle FAA ACO must approve, prior to its use, any desired extension not explicitly listed above. 

This exceptional short term extension listed above applies to airlines that fall under the United States FAA jurisdiction only. Operators who are not under 

the U.S. FAA jurisdiction should obtain interval extension approvals from their local regulatory agency.

REGULATORY AGENCY APPROVAL

Any deviations from the published AWLs instructions included in this document require approval from the Seattle FAA ACO. This applies to operators 

under the US FAA jurisdiction only and to airplanes registered in the US. All other operators should obtain approval form their own local regulatory agency 

for any deviations from the listed AWL instructions. 

NOV 2007
737-12345 AIRWORTHINESS LIMITATIONS/CERTIFICATION MAINTENANCE REQUIREMENTS

D6-38278-CMR

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AWL REVISION PROCESS

In the event that an AWL is revised, Boeing will prepare a revision to this document that will be approved by the Seattle FAA ACO. This revision will then 

be forwarded to all 737-100/200/200C/300/400/500 operators and the Seattle FAA ACO.

PAGE FORMAT: SYSTEMS AIRWORTHINESS LIMITATIONS

COLUMN EXPLANATION

AWL NUMBER Each task is given a unique AWL Item Number. The first and second digits are the ATA Chapter Number.

TASK ALI = Airworthiness Limitation Instruction. These tasks are inspections that should be performed at the listed intervals.

CDCCL = Critical Design Configuration Control Limitations

INTERVAL Task frequencies are specified in terms of a usage parameter such as flight hours, cycles or calendar time.

APPLICABILITY Airplane model applicability.

TASK

DESCRIPTION

Description of the task to be performed or critical design configurations aspects that cannot be changed without violating 

the intent of the design.

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737-100, -200, -200C MAINTENANCE PLANNING DATA – AIRWORTHINESS LIMITATIONS – FUEL SYSTEMS

AWL NUMBER TASK INTERVAL APPLICABILITY TASK DESCRIPTION

28-AWL-01 ALI 10 YRS

737-100/200/200C 

airplanes that have 

incorporated 

Service Bulletin 

737-28-1208

External Wires Over Center Fuel Tank

Concern: Potential for Wire Chafing and Arcing to Center Fuel Tank Upper Panel.

Perform a detailed inspection of the wire bundles routed over the center fuel tank and under the 

main deck floor boards per AMM 28-11-00 to detect damaged clamps, wire chafing, damage to 

the vapor barrier, and that the wire bundle is not in contact with surface of the center fuel tank. If 

discrepancies are found repair per the Boeing Standard Wiring Practices Manual (SWPM) 

D6-54446.

Interval Note: Threshold for interval inspection is 10 years after incorporation of Service Bulletin 

737-28-1208.

28-AWL-02 CDCCL N/A

737-100/200/200C 

airplanes that have 

incorporated 

Service Bulletin 

737-28-1208

External Wires Over Center Fuel Tank 

Concern: Potential for Wire Chafing and Arcing to Center Fuel Tank Upper Panel.

If any maintenance is performed in the area under the floor boards and over the center fuel tank, 

verify the following:

1. Maintain the existing wire bundle routing and clamping.

2. Installation of any new wire bundles must be per Boeing Standard Wiring Practices Manual,

 D6-54446.

3. Perform a detailed inspection of the wire bundles routed on main deck over the center fuel 

tank and under the main deck floor boards in the areas of the performed maintenance to detect 

damaged clamps, wire chafing, and that the wire bundle is not in contact with the surface of the 

center tank. If wiring discrepancies are found, repair per the Boeing Standard Wiring Practices 

Manual, D6-54446.

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28-AWL-03 ALI 10 YRS

737-200/200C 

airplanes that have 

incorporated 

Service Bulletin

737-28-1178

Fuel Quantity Indicating System (FQIS) – Out-Tank Wiring Lightning Shield to 

Ground Termination

Concern: Potential for Lightning induced voltages on the FQIS wiring to enter the fuel tank.

Perform the following functional check to ensure the integrity of the FQIS wiring shield to ground 

termination:

Verify the resistance of the shield to ground terminations at the spar penetration in the 

unpressurized area by making the following measurements using a Loop Resistance Tester P/N 

906-10246-2 or 906-10246-3 per Boeing AMM 20-55-54. Restore the bonds per the Boeing 

AMM if required.

Perform a loop resistance measurement where the wire bundle enters the fuel tank.

The loop resistance shall not exceed 28 milliohms for Connector D884 (Left Main Tank).

The loop resistance shall not exceed 28 milliohms for Connector D888 (Right Main Tank).

The loop resistance shall not exceed 35 milliohms for Connector D886 (Center Main Tank).

28-AWL-04 CDCCL N/A

 737-200/200C 

airplanes that have 

incorporated 

Service Bulletin

737-28-1178

Fuel Quantity Indicating System (FQIS) – Out-Tank Wiring Lightning Shield to 

Ground Termination 

Concern: Potential for Lightning induced voltages on the FQIS wiring to enter the fuel tank.

If the FQIS wire bundle or the shield on the FQIS wire bundle is repaired or replaced, verify 

the following:

1. Presence of shielded wiring.

2. The shield ground is terminated per the Boeing SWPM 20-10-15.

3. The installation is inspected per 28-AWL-03. 

737-100, -200, -200C MAINTENANCE PLANNING DATA – AIRWORTHINESS LIMITATIONS – FUEL SYSTEMS

AWL NUMBER TASK INTERVAL APPLICABILITY TASK DESCRIPTION

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28-AWL-05 CDCCL N/A All

Fuel Quantity Indicating System (FQIS) – Out-Tank Wiring Installation Separation Requirement

Concerns: Potential for hot shorts and EMI induced voltages on the FQIS wiring to enter the 

fuel tank.

For airplanes incorporating Isolated Fuel Quantity Transmitter (IFQT) Service Bulletin 737-28-

1178, the FQIS wiring is defined as the wiring between the IFQT and the fuel tank.

For airplanes not incorporating IFQT, the FQIS wiring is defined as the wiring between the 

indicators and the fuel tank.

Routing and installation of any new wiring must use wire types BMS 13-48, BMS 13-60 or 

BMS 13- 58, and not be within a 2-inch radius of the FQIS wiring. Under single failures of clamps 

or brackets, a separation greater than 1⁄2 inch must be maintained from the FQIS wiring.

This AWL is for design requirements.

The installation is per SWPM 20-10-11.

28-AWL-06 CDCCL N/A

737-100/200/200C 

airplanes that 

Service Bulletin 

737-28-1178 is not 

applicable to 

(Airplanes with 

Electronic

VTO Units)

Fuel Quantity Indicating System (FQIS) – Indicator and VTO Unit Repair

Concern: Potential for maintenance error during FQIS Indicator or Volumetric Top-Off (VTO) Unit 

repair. The design of the FQIS Indicators and the VTO Unit limits the voltage, current and power 

into the tank to preclude possible ignition source into the tank.

Repair and overhaul of FQIS Indicators and VTO must be per Goodrich (V89305) Component 

Maintenance Manual (CMM) 28-41-11 Revision 12, CMM 28-41-13 Revision 11, 28-41-23 

Revision 10, or later revisions of these CMMs that have been approved by the Seattle FAA ACO.

737-100, -200, -200C MAINTENANCE PLANNING DATA – AIRWORTHINESS LIMITATIONS – FUEL SYSTEMS

AWL NUMBER TASK INTERVAL APPLICABILITY TASK DESCRIPTION

MAY 2009
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28-AWL-07 CDCCL N/A All

Fuel Quantity Indicating System (FQIS) – Repair of In-Tank Hardware (Tank Units and 

Compensators) 

Concern: Potential for maintenance error during repair of in-tank hardware (tank units and 

compensators). Arc gaps may develop that could result in an ignition source inside the fuel tank. 

The dielectric of these components must be maintained to provide lightning protection for 

voltages that could be coupled on the FQIS wiring or onto the wiring between the IFQT and the 

fuel tank if the shield or shield ground of the wiring is compromised. 

Repair and overhaul of FQIS tank units and compensators must be per Goodrich (V89305) 

Component Maintenance Manual (CMM) 28-40-25 Revision L, CMM 28-41-05 Revision 11, CMM 

28-40-58 Revision 4, or later revisions of these CMMs that have been approved by the Seattle 

FAA ACO. The AC powered float switch on airplanes with Volumetric Top-Off (VTO) function is 

not repairable.

The manufacturer's production procedures for this component may be used as an alternate to the 

identified CMM.

28-AWL-08 CDCCL N/A All

Fuel Quantity Indicating System (FQIS) – Repair or Replacement of In-Tank Wire Harness

Concern: Potential for error during repair or replacement of in-tank wire harness. Arc gaps may 

develop that could result in an ignition source inside the fuel tank. For airplanes with IFQT this is 

a concern if the safe-side harness is compromised.

Repair and overhaul of FQIS in-tank wire harness must be per Boeing SWPM 20-14-12. 

Installation of FQIS in-tank wire harness must be per Boeing AMM 28-41-101. Wire slack 

clearance between wires and structure must be greater than 0.125 inches. Verify the following 

when installing the spar penetration receptacle:

1. The mounting area is free of primer or paint.

2. A new O-ring is installed.

3. The receptacle mounting screws are tightened to 65 to 90 pound-inches.

4. A continuous bead of sealant is applied around the entire perimeter of the internal tank

 harness connector at the spar interface.

737-100, -200, -200C MAINTENANCE PLANNING DATA – AIRWORTHINESS LIMITATIONS – FUEL SYSTEMS

AWL NUMBER TASK INTERVAL APPLICABILITY TASK DESCRIPTION

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28-AWL-09 CDCCL N/A

737-100/200/200C 

airplanes that have 

incorporated 

Service Bulletin

737-29A1096

Lightning Protection – Hydraulic Line Fuel Tank Penetration

Concern: Potential for arcing or sparking inside the tank at the interface between the bulkhead 

fitting and the spar during a lightning strike event.

The following design features must be maintained per Boeing AMM 29-11-53 if the bulkhead 

fitting is removed and replaced:

1. Verify electrical fay surface bond from bulkhead fitting to structure outside the tank is 

0.001 ohms (1 milliohm) or less,

2. Install fillet seal on the fitting to the tank wall interface outside the tank.

3. Install full bodied fillet seal encapsulating the fitting to the tank wall interface inside the tank.

4. Verify an electrostatic bonding jumper exists between the structure and the Hydraulic Heat 

Exchanger inside the tank.

5. Verify electrical bond from structure to the Hydraulic Heat Exchanger inside the tank is 

0.005 ohms (5 milliohms) or less if the bonding jumper was removed and replaced.

28-AWL-10 CDCCL N/A

737-100/200/200C 

airplanes that have 

incorporated 

Service Bulletin

737-28A1174

Lightning Protection – Engine Fuel Feed Line Tank Penetration

Concern: Potential for arcing or sparking inside the tank at the interface between the bulkhead 

fitting and the spar during a lightning strike event.

The following features must be maintained per Boeing AMM 28-22-142 if the bulkhead fitting or 

attached tubing are removed and replaced: 

1. Verify electrical fay surface bond from bulkhead fitting to structure (wing front spar, out-tank) is 

0.0005 ohms (0.5 milliohms) or less.

2. Install full-bodied fillet seal encapsulating the bulkhead fitting to the wing front spar interface 

inside and outside the tank.

3. Install full bodied fillet seal encapsulating the tubes to fitting joints interface inside and outside 

the tank.

4. Verify an electrostatic bonding jumper exists between the first tube mating with the bulkhead 

fitting, and the structure inside the tank.

5. Verify electrical bond from the structure (wing front spar, in-tank) to first tube mating with the 

bulkhead fitting is 0.010 ohms (10 milliohms) or less. 

737-100, -200, -200C MAINTENANCE PLANNING DATA – AIRWORTHINESS LIMITATIONS – FUEL SYSTEMS

AWL NUMBER TASK INTERVAL APPLICABILITY TASK DESCRIPTION

MAY 2009
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28-AWL-11 CDCCL N/A All

Lightning, Fault Current or Hot Short Protection – Fuel Tank Penetrations

Concern: Potential for arcing or sparking inside the tank at a conductive metal-to-ground 

structure interface as a result of electrical fault currents or lightning strike events due to 

insufficient bonding within the ground electrical path. 

Any alteration, design change or repair involving new penetrations of the fuel tanks (such as a 

repair with fasteners, adding a bracket, bulkhead fitting or equipment) or change to the design 

features of the existing equipment penetrations (such as fuel measuring sticks, sump drain 

valves, fueling manifold, fuel temperature sensor, and motor operated fuel shutoff valve adaptor 

plate) requires approval by the Seattle FAA ACO or an Authorized Representative (AR) of the 

Boeing Commercial Airplanes Delegated Compliance Organization (BDCO). 

However, any alteration, design change or repair involving new penetrations of the fuel tanks, 

accomplished in accordance with an FAA-approved Boeing Structural Repair Manual (SRM) or 

Boeing Service Bulletin is not subject to this requirement for additional approval.

28-AWL-12 CDCCL N/A All

AC and DC Electrical Fuel Tank Pump Maintenance

Concern: Potential for maintenance error during pump overhaul. Fuel pump designs contain 

ignition source prevention means (i.e., flame arrestor, thermal fuses, materials, leadwire retention 

means, etc.) that must be maintained if pump is overhauled. 

Repair and overhaul of fuel pumps must be per Eaton (VK2523) Component Maintenance 

Manual (CMM) 28-20-37 Revision 10, Argo-Tech (V59875) CMM 28-20-1 Revision 7, CMM 28-

20-5 Revision 6, CMM 28-20-07 Revision 1, or later revisions of these CMMs that have been 

approved by the Seattle FAA ACO.

The manufacturer's production procedures for this component may be used as an alternate to the 

identified CMM.

737-100, -200, -200C MAINTENANCE PLANNING DATA – AIRWORTHINESS LIMITATIONS – FUEL SYSTEMS

AWL NUMBER TASK INTERVAL APPLICABILITY TASK DESCRIPTION

MAY 2009
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28-AWL-13 CDCCL N/A All

AC Fuel Pump Fault Current Fay Surface Bond Installation 

Concern: Potential for fault current path through the pump housing to structure inside the tank. 

Electrical faults internal to the fuel pump motor impeller are by design routed through the motor 

impeller assembly to the bonding straps on the front face of the motor impeller assembly to 

structure outside the tank. The fay surface bond ensures that fault currents are conducted to 

structure outside the tank until the circuit breaker and/or GFI has had time to remove power from 

the pump.

The following features must be maintained during pump replacement per Boeing 

AMM-28-22-41:

1. Installation of the pump fault current faying surface bond.

2. Verify Motor Impeller bonding resistance to structure is 0.0002 ohms (0.2 milliohms) or less.

28-AWL-14 CDCCL N/A

737-200/200C 

airplanes that have 

incorporated 

Service Bulletin

737-28A1141 or 

737-28A1192

Fueling Float Switch System Installation

Concern: Potential for wire chafing and arcing to conduit inside the tank. The float switch 

assemblies in fuel tank 1 and 2 are not repairable to the initial manufactured standards. The 

center tank and Boeing auxiliary tank (if installed) Float Switch and Liner are not repairable to the 

initial manufactured standards. (Refer to Boeing AMM 28-21-71)

During float switch replacement, a new float switch assembly must be used in Tanks 1 and 2, and 

a new float switch assembly and liner system must be used for center and Boeing auxiliary fuel 

tank (if installed) as applicable. 

28-AWL-15 CDCCL N/A All

Center Fuel Tank Access Doors – Lightning Protection Bond

Concern: Potential for arcing or sparking inside the tank at the interface between the door and the 

tank structure as a result of a direct strike or conducting currents through the wing skin.

The following features must be maintained during center fuel tank access door installation per 

Boeing AMM 28-11-31: 

Verify presence of a phenolic strip positioned around the outermost periphery of the door that 

mates with the wing skin inside the tank.

Connect the bonding jumper to the door and verify the resistance between the door and structure 

is 0.010 ohms (10 milliohms) or less.

737-100, -200, -200C MAINTENANCE PLANNING DATA – AIRWORTHINESS LIMITATIONS – FUEL SYSTEMS

AWL NUMBER TASK INTERVAL APPLICABILITY TASK DESCRIPTION

MAY 2009
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28-AWL-16 CDCCL N/A All

Main Fuel Tank Access Doors – Lightning Protection Bond

Concern: Potential for arcing or sparking inside the tank at the interface between the door and the 

tank structure as a result of a direct strike or conducting currents through the wing skin.

The following features must be maintained during main (wing) fuel tank access door installation 

per Boeing AMM 28-11-11: 

Verify presence of a phenolic strip positioned around the outermost periphery of the door that 

mates with the wing skin inside the tank, and apply grease or anti-corrosion compound to both 

sides of the knitted aluminum mesh gasket. Install the prepared knitted aluminum mesh gasket 

between the outside face of the door and the wing skin to establish the electrical conductivity 

between the access door and the wing skin using the clamp ring and fasteners torqued to that 

specified in Boeing AMM 28-11-11.

Note: Not applicable to Surge Tank Access Doors with the NACA Vent Scoop and Pressure 

Relief Valve. 

28-AWL-17 CDCCL N/A All

Surge Tank Access Doors – Lightning Protection Bond

Concern: Potential for arcing or sparking inside the tank at the interface between the door and the 

tank structure as a result of a direct strike or conducting currents through the wing skin.

During surge tank access door installation, perform the following actions per Boeing 

AMM 28-11-11:

Clean the countersinks on the door. If the Pressure Relief Valve is removed and replaced, 

maintain the electrical fay surface bond between the pressure relief valve and the door 0.010 

ohms (10 milliohms) or less per Boeing AMM 28-13-41. If the Flame Arrestor is removed and 

replaced, maintain the following electrical bonds per Boeing AMM 28-13-31/401:

Verify the electrical bond from the flame arrestor to the door assembly is 0.010 ohms 

(10 milliohms) or less. If the air vent scoop of the Type II flame arrestor is removed and replaced, 

maintain the following electrical bonds per Boeing AMM 28-13-31:

Verify the electrical bond from the flame arrestor to the door assembly is 0.010 ohms 

(10 milliohms) or less.

Install door using the same part number conductive fasteners and torque to that specified in the 

Boeing AMM.

737-100, -200, -200C MAINTENANCE PLANNING DATA – AIRWORTHINESS LIMITATIONS – FUEL SYSTEMS

AWL NUMBER TASK INTERVAL APPLICABILITY TASK DESCRIPTION

MAY 2009
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28-AWL-18 CDCCL N/A

737-100/200/200C 

airplanes that have 

incorporated 

Service Bulletin

737-28A1263

Fuel Boost Pump Wires in Conduit Installation – In-Fuel Tank

Concern: Potential for the boost pump wiring to chafe and arc in the conduit and provide an 

ignition source in the fuel tank.

The boost pump wires that are in the conduits in the fuel tanks have incorporated a Teflon sleeve 

to protect from wire chafing per Service Bulletin 737-28A1263 (FAA AD 2007-24-02). The wiring 

also has a jacket to provide chafing protection.

Ensure the following condition exists when replacing pump wiring or wiring conduit:

- Jacketed wiring and a Teflon sleeve.

The Teflon sleeve is not repairable. Whenever the wiring in conduit or the conduit is removed, 

new Teflon sleeve must be installed.

28-AWL-19 CDCCL N/A All

Resetting of Tripped Fuel Pump Circuit Breakers or Ground Fault Interrupters (GFIs)

Concern: Potential for arcing or sparking inside the tank between fuel pumps and fuel pump 

housings and outside the tank between pump wiring and structure in flammable leakage zones.

Verify it is safe to reset the circuit breaker(s) or GFIs by following the applicable OEM 

troubleshooting procedures. Fault(s) that resulted in circuit breaker or GFI trip must be isolated 

and corrected prior to reset.

28-AWL-20 CDCCL N/A

737-200/200C 

airplanes that have 

incorporated 

Service Bulletin

737-28-1178

Fuel Quantity Indicating System (FQIS) – Isolated Fuel Quantity Transmitter (IFQT) 

Concern: The IFQT is designed to limit the voltage, current, and power on the FQIS fuel tank 

wiring and components to intrinsically safe levels in order to preclude the potential of an ignition 

source within the fuel tank. IFQT installed per FAA AD 99-03-04.

The IFQT is repairable only by Goodrich (89305) per their CMM 28-41-91. 

28-AWL-21 ALI 1 YR

737-100/200 

airplanes that have 

incorporated 

Service Bulletin

737-28A1228

Center Tank Fuel Boost Pump Automatic Shutoff System

Concern: Dry running the center tank fuel pumps has the potential for single failure ignition 

sources developing at the pump inlet due to either frictional heating or sparking as a result of 

FOD contacting the pump rotating elements, rotating elements contacting stationary parts, or hot 

journal bearings due to bearing contamination or failure.

The automatic shutoff system is installed and designed to limit continuous dry running condition 

to 15 seconds.

The following test is required in order to protect against latent faults:

Functionally check the center tank fuel boost pump automatic shutoff system per AMM 28-22-0.

737-100, -200, -200C MAINTENANCE PLANNING DATA – AIRWORTHINESS LIMITATIONS – FUEL SYSTEMS

AWL NUMBER TASK INTERVAL APPLICABILITY TASK DESCRIPTION

MAY 2009
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28-AWL-22 ALI 1 YR

737-100/200 

airplanes with 

Boeing certified 

Auxiliary fuel tanks 

that have 

incorporated 

Service Bulletin

737-28A1228

Auxiliary Tank Fuel Boost Pump Automatic Shutoff System

Concern: Dry running the auxiliary tank fuel pumps has the potential for single failure ignition 

sources developing at the pump inlet due to either frictional heating or sparking as a result of 

FOD contacting the pump rotating elements, rotating elements contacting stationary parts, or hot 

journal bearings due to bearing contamination or failure.

The automatic shutoff system is installed and designed to limit continuous dry running condition 

to 15 seconds.

The following test is required in order to protect against latent faults:

Functionally check the auxiliary tank fuel boost pump automatic shutoff system per 

AMM 28-22-0.

28-AWL-23 ALI 1 YR

737-100/200 

airplanes that have 

incorporated 

Service Bulletin

737-28A1212

Boost Pump Ground Fault Interrupter (GFI)

Concern: Potential for pump housing burn-through, either internal or external to the fuel tank, as a 

result of major arcing due to electrical failure (i.e., damaged electrical connector, stator windings 

or leadwire to housing/end cap shorting).

The GFI is designed to detect electrical faults and open the circuit prior to pump housing burnthrough.

The following maintenance check is required in order to ensure continued functionality of the 

GFI circuit:

Operational check the GFI of all AC fuel tank boost Pumps per AMM 28-22-41.

28-AWL-24 ALI 1 YR

737-100/200/200C 

airplanes that have 

incorporated 

Service Bulletin

737-28A1227

Center Tank Fuel Boost Pump Power Failed On Protection System

Concern: Dry running the center tank fuel pumps has the potential for single failure ignition 

sources developing at the pump inlet due to either frictional heating or sparking as a result of 

FOD contacting the pump rotating elements, rotating elements contacting stationary parts or hot 

journal bearings due to bearing contamination or failure.

The power failed on protection system is installed and designed in order to protect against a 

single failure (i.e. wiring faults or a welded fuel pump control relay) keeping power on the pump 

when the associated fuel pump control switch is positioned to OFF.

The following test is required in order to protect against latent faults:

Verify continued functionality of the center tank fuel boost pump Power Failed On Protection 

System per AMM 28-22-0.

737-100, -200, -200C MAINTENANCE PLANNING DATA – AIRWORTHINESS LIMITATIONS – FUEL SYSTEMS

AWL NUMBER TASK INTERVAL APPLICABILITY TASK DESCRIPTION

MAY 2009
D6-38278-CMR

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737-12345 AIRWORTHINESS LIMITATIONS/CERTIFICATION MAINTENANCE REQUIREMENTS

28-AWL-25 ALI 1 YR

737-200/200C 

airplanes with 

Auxiliary fuel tanks 

that have 

incorporated

Service Bulletin 

737-28A1227

Auxiliary Fuel Tank Boost Pump Power Failed On Protection System

Concern: Dry running the auxiliary tank fuel pumps has the potential for single failure ignition 

sources developing at the pump inlet due to either frictional heating or sparking as a result of 

FOD contacting the pump rotating elements, rotating elements contacting stationary parts or hot 

journal bearings due to bearing contamination or failure.

The power failed on protection system is installed and designed in order to protect against a 

single failure (i.e. wiring faults or a welded fuel pump control relay) keeping power on the pump 

when the associated fuel pump control switch is positioned to OFF.

The following test is required in order to protect against latent faults:

Verify continued functionality of the auxiliary tank fuel boost pump Power Failed On Protection 

System per AMM 28-22-0.

737-100, -200, -200C MAINTENANCE PLANNING DATA – AIRWORTHINESS LIMITATIONS – FUEL SYSTEMS

AWL NUMBER TASK INTERVAL APPLICABILITY TASK DESCRIPTION

MAY 2009
737-12345 AIRWORTHINESS LIMITATIONS/CERTIFICATION MAINTENANCE REQUIREMENTS

D6-38278-CMR

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737-300, -400, -500 MAINTENANCE PLANNING DATA – AIRWORTHINESS LIMITATIONS – FUEL SYSTEMS

AWL NUMBER TASK INTERVAL APPLICABILITY DESCRIPTION

28-AWL-01 ALI 10 YRS

737-300/400/500 

airplanes that have 

incorporated 

Service Bulletin 

737-28-1208

External Wires Over Center Fuel Tank 

Concern: Potential for Wire Chafing and Arcing to Center Fuel Tank Upper Panel.

Perform a detailed inspection of the wire bundles routed on main deck over the center fuel 

tank and under the main deck floor boards per AMM 28-11-00 to detect damaged clamps, wire 

chafing, damage to the vapor barrier, and that the wire bundle is not in contact with surface of 

the center fuel tank. If discrepancies are found, repair per the Boeing Standard Wiring 

Practices Manual, D6-54446. 

Interval Note: Threshold for initial inspection is 10 years after incorporation of Service Bulletin 

737-28-1208.

28-AWL-02 CDCCL N/A

737-300/400/500 

airplanes that have 

incorporated 

Service Bulletin 

737-28-1208

External Wires Over Center Fuel Tank 

Concern: Potential for Wire Chafing and Arcing to Center Fuel Tank Upper Panel

If any maintenance is performed in the area under the main deck floor boards and over the 

center fuel tank, verify the following:

1. Maintain the existing wire bundle routing and clamping.

2. Installation of any new wire bundles must be per Boeing Standard Wiring Practices

 Manual, D6-54446.

3. Perform a detailed inspection of the wire bundles routed on main deck over the center 

 fuel tank and under the main deck floor boards in the areas of the performed maintenance

 to detect damaged clamps, wire chafing, and that the wire bundle is not in contact with the

 surface of the center tank. If wiring discrepancies are found, repair per the Boeing

 Standard Wiring Practices Manual, D6-54446.

MAY 2009
D6-38278-CMR

BOEING PROPRIETARY - Copyright (c) - Unpublished Work - See title page for details Page 9.0-34

737-12345 AIRWORTHINESS LIMITATIONS/CERTIFICATION MAINTENANCE REQUIREMENTS

28-AWL-03 ALI 10 YRS

737-300/400/500 

airplanes that have 

incorporated 

Service Bulletins 

737-28-1175 or 

737-28-1183 or 

737-28-1186

Fuel Quantity Indicating System (FQIS) – Out-Tank Wiring Lightning Shield to 

Ground Termination

Concern: Potential for Lightning induced voltages on the FQIS wiring to enter the fuel tank.

Perform the following functional check to ensure the integrity of the FQIS wiring shield to 

ground termination:

Verify the resistance of the shield to ground terminations at the spar penetration in the 

unpressurized area by making the following measurements using a Loop Resistance Tester P/

N 906-10246-2 or 906-10246-3 per Boeing AMM 20-55-54.

Restore the bonds per the Boeing AMM if required.

The loop resistance shall not exceed 28 milliohms for Connector D884 (Left Main Tank).

The loop resistance shall not exceed 28 milliohms for Connector D888 (Right Main Tank).

The loop resistance shall not exceed 35 milliohms for Connector D886 (Center Main Tank).

28-AWL-04 CDCCL N/A

737-300/400/500 

airplanes that have 

incorporated 

Service Bulletins 

737-28-1175 or 

737-28-1183 or 

737-28-1186

Fuel Quantity Indicating System (FQIS) – Out-Tank Wiring Lightning Shield to 

Ground Termination 

Concern: Potential for Lightning induced voltages on the FQIS wiring to enter the fuel tank.

If the FQIS wire bundle or the shield on the FQIS wire bundle is repaired or replaced, verify 

the following:

1. Presence of shielded wiring

2. The shield ground is terminated per the Boeing SWPM 20-10-15

3. The installation is inspected per 28-AWL-03.

28-AWL-05 CDCCL N/A

737-300/400/500 

airplanes that have 

incorporated 

Service Bulletins 

737-28-1175 or 

737-28-1183 or 

737-28-1186

Fuel Quantity Indicating System (FQIS) – Out-Tank Wiring Installation Separation 

Requirement 

Concerns: Potential for hot shorts and EMI induced voltages on the IFQT safe-side wire 

harness to enter the fuel tank. The FQIS wiring is defined as the harness between the Isolated 

Fuel Quantity Transmitter (IFQT) and the fuel tank.

Routing and installation of any new wiring must use wire types BMS 13-48, BMS 13-60 or 

BMS 13-58, and not be within a 2-inch radius of the FQIS wiring. Under single failures of 

clamps or brackets, a separation greater than 1⁄2 inch must be maintained from FQIS wiring. 

This AWL is for design requirements.

The installation is per SWPM 20-10-11.

737-300, -400, -500 MAINTENANCE PLANNING DATA – AIRWORTHINESS LIMITATIONS – FUEL SYSTEMS

AWL NUMBER TASK INTERVAL APPLICABILITY DESCRIPTION

MAY 2009
737-12345 AIRWORTHINESS LIMITATIONS/CERTIFICATION MAINTENANCE REQUIREMENTS

D6-38278-CMR

BOEING PROPRIETARY - Copyright (c) - Unpublished Work - See title page for details Page 9.0-35

28-AWL-06 CDCCL N/A

737-300/400/500 

airplanes that have 

incorporated 

Service Bulletins 

737-28-1175 or 

737-28-1183 or 

737-28-1186

Fuel Quantity Indicating System (FQIS) – Isolated Fuel Quantity Transmitter (IFQT)

Concern: The IFQT is designed to limit the voltage, current, and power on the FQIS fuel tank 

wiring and components to intrinsically safe levels in order to preclude the potential of an 

ignition source within the fuel tank. IFQT installed per FAA AD 99-03-04.

The IFQT is repairable only by Goodrich (89305) per their CMM 28-41-91.

28-AWL-07 CDCCL N/A All

Fuel Quantity Indicating System (FQIS) – Repair of In-Tank Hardware (Tank Units and 

Compensators) 

Concern: Potential for maintenance error during repair of in-tank hardware (tank units and 

compensators). Arc gaps may develop that could result in an ignition source inside the fuel 

tank. The dielectric of these components must be maintained to protect from lightning 

voltages that could couple onto the FQIS wiring between the IFQT and the tank if the wire 

shield ground is compromised. 

Repair and overhaul of FQIS tank units and compensators must be per the manufacturer 

Component Maintenance Manual (CMM) 28-40-25 Revision L, 28-41-05 Revision Number 11, 

or 28-40-58 Revision Number 4 as applicable or later revisions of these CMMs that have been 

approved by the Seattle FAA ACO.

The manufacturer's production procedures for this component may be used as an alternate to 

the identified CMM.

737-300, -400, -500 MAINTENANCE PLANNING DATA – AIRWORTHINESS LIMITATIONS – FUEL SYSTEMS

AWL NUMBER TASK INTERVAL APPLICABILITY DESCRIPTION

MAY 2009
D6-38278-CMR

BOEING PROPRIETARY - Copyright (c) - Unpublished Work - See title page for details Page 9.0-36

737-12345 AIRWORTHINESS LIMITATIONS/CERTIFICATION MAINTENANCE REQUIREMENTS

28-AWL-08 CDCCL N/A All

Fuel Quantity Indicating System (FQIS) – Repair or Replacement of In-Tank Wire Harness

Concern: Potential for error during repair or replacement of in-tank wire harness. Arc gaps 

may develop that could result in an ignition source inside the fuel tank. This CDCCL is also 

required for airplanes with IFQT in case the FQIS wiring between the IFQT and the fuel tank is 

compromised.

Repair and overhaul of FQIS in-tank wire harness must be per Boeing SWPM 20-14-12. 

Installation of FQIS in-tank wire harness must be per Boeing AMM 28-41-44. During 

installation of the harness, verify the following:

For airplanes with rectangular bussing plug, tighten the mounting screws to a torque of 

65 – 90 pound-inches.

For airplanes with circular bussing plug:

- On the receptacle for the No. 1 or the No. 2 Tank, tighten the receptacle nut to a torque of 

325 – 350 pound-inches.

- On the receptacle for the center tank, tighten the receptacle nut to a torque of 

100 – 150 inch-pounds.

A thin layer of sealant is present around the joint between the receptacle and the bulkhead on 

the inside of the tank.

- Apply a continuous bead of sealant to the joint.

- Make sure the bead fully seals the joint.

Wire slack clearance between wires and structure must be greater than 0.125 inches.

737-300, -400, -500 MAINTENANCE PLANNING DATA – AIRWORTHINESS LIMITATIONS – FUEL SYSTEMS

AWL NUMBER TASK INTERVAL APPLICABILITY DESCRIPTION

MAY 2009
737-12345 AIRWORTHINESS LIMITATIONS/CERTIFICATION MAINTENANCE REQUIREMENTS

D6-38278-CMR

BOEING PROPRIETARY - Copyright (c) - Unpublished Work - See title page for details Page 9.0-37

28-AWL-09 CDCCL N/A

737-300/400/500 

airplanes that have 

incorporated 

Service Bulletin 

737-29A1096

Lightning Protection – Hydraulic Line Fuel Tank Penetration 

Concern: Potential for arcing or sparking inside the tank at the interface between the bulkhead 

fitting and the spar during a lightning strike event.

The following design features must be maintained per Boeing AMM 29-15-04. If the bulkhead 

fitting is removed and replaced:

1. Verify electrical fay surface bond from bulkhead fitting to structure outside the tank is 

0.001 ohms (1 milliohm) or less,

2. Install fillet seal on the fitting to the tank wall interface outside the tank, 

3. Install full bodied fillet seal encapsulating the fitting to the tank wall interface inside the tank, 

4. Verify an electrostatic bonding jumper exists between the structure and the Hydraulic 

Heat Exchanger inside the tank, and

5. Verify electrical bond from structure to the Hydraulic Heat Exchanger inside the tank is 

0.005 ohms (5 milliohms) or less if the bonding jumper was removed and replaced.

28-AWL-10 CDCCL N/A

737-300/400/500 

airplanes that have 

incorporated 

Service Bulletin 

737-28A1174

Lightning Protection – Engine Fuel Feed Line Tank Penetration

Concern: Potential for arcing or sparking inside the tank at the interface between the bulkhead 

fitting and the spar during a lightning strike event.

The following features must be maintained per Boeing AMM 28-22-15 if the bulkhead fitting or 

attached tubing are removed and replaced: 

1. Verify electrical fay surface bond from bulkhead fitting to structure is 0.0005 ohms

 (0.5 milliohms) or less,

2. Install full-bodied fillet seal encapsulating the fitting to the tank wall interface inside and 

outside the tank,

3. Install full-bodied fillet seal encapsulating the tubes to fitting joints interface inside and 

outside the tank, 

4. Verify an electrostatic bonding jumper exists between first tube mating with the bulkhead 

fitting and the mating tube inside the tank, and

5. Verify electrical bond from the structure (wing front spar, in-tank) to first tube mating with 

the bulkhead fitting is 0.010 ohms (10 milliohms) or less.

737-300, -400, -500 MAINTENANCE PLANNING DATA – AIRWORTHINESS LIMITATIONS – FUEL SYSTEMS

AWL NUMBER TASK INTERVAL APPLICABILITY DESCRIPTION

MAY 2009
D6-38278-CMR

BOEING PROPRIETARY - Copyright (c) - Unpublished Work - See title page for details Page 9.0-38

737-12345 AIRWORTHINESS LIMITATIONS/CERTIFICATION MAINTENANCE REQUIREMENTS

28-AWL-11 CDCCL N/A All

Lightning, Fault Current or Hot Short Protection – Fuel Tank Penetrations

Concern: Potential for arcing or sparking inside the tank at a conductive metal-to-ground 

structure interface as a result of electrical fault currents or lightning strike events due to 

insufficient bonding within the ground electrical path. 

Any alteration, design change or repair involving new penetrations of the fuel tanks (such as a 

repair with fasteners, adding a bracket, bulkhead fitting or equipment) or change to the design 

features of the existing equipment penetrations (such as fuel measuring sticks, sump drain 

valves, fueling manifold, fuel temperature sensor, and motor operated fuel shutoff valve 

adaptor plate) requires approval by the Seattle FAA ACO or an Authorized Representative 

(AR) of the Boeing Commercial Airplanes Delegated Compliance Organization (BDCO). 

However, any alteration, design change or repair involving new penetrations of the fuel tanks, 

accomplished in accordance with an FAA-approved Boeing Structural Repair Manual (SRM) or 

Boeing Service Bulletin is not subject to this requirement for additional approval.

28-AWL-12 CDCCL N/A All

AC and DC Electrical Fuel Tank Pump Maintenance

Concern: Potential for maintenance error during pump overhaul. Fuel pump designs contain 

ignition source prevention means (i.e., flame arrestor, thermal fuses, materials, leadwire 

retention means, etc.) that must be maintained if pump is overhauled. 

Repair and overhaul of Fuel Pumps must be per the manufacturer’s Component Maintenance 

Manual (CMM) Numbers 28-20-37 Revision Number 10, 28-20-1 Revision Number 7, 28-20-5 

Revision Number 6, 28-20-07 Revision Number 1, as applicable, or later revisions of these 

CMMs that have been approved by the Seattle FAA ACO.

The manufacturer's production procedures for this component may be used as an alternate to 

the identified CMM.

737-300, -400, -500 MAINTENANCE PLANNING DATA – AIRWORTHINESS LIMITATIONS – FUEL SYSTEMS

AWL NUMBER TASK INTERVAL APPLICABILITY DESCRIPTION

MAY 2009
737-12345 AIRWORTHINESS LIMITATIONS/CERTIFICATION MAINTENANCE REQUIREMENTS

D6-38278-CMR

BOEING PROPRIETARY - Copyright (c) - Unpublished Work - See title page for details Page 9.0-39

28-AWL-13 CDCCL N/A All

AC Fuel Pump Fault Current Fay Surface Bond Installation 

Concern: Potential for fault current path through the pump housing to structure inside the tank. 

Electrical faults internal to the fuel pump motor impeller are by design routed through the motor 

impeller assembly to the bonding straps on the front face of the motor impeller assembly to 

structure outside the tank. The fay surface bond ensures that fault currents are conducted to 

structure outside the tank until the circuit breaker and/or GFI has had time to remove power 

from the pump.

The following features must be maintained during pump replacement per Boeing 

AMM 28-22-41:

1. Installation of the pump fault current faying surface bond.

2. Verify Motor Impeller bonding resistance to structure is 0.0002 ohms (0.2 milliohms) 

or less.

28-AWL-14 CDCCL N/A

737-300/400/500 

airplanes that have 

incorporated 

Service Bulletins 

737-28A1141 or 

737-28A1192

Fueling Float Switch System Installation

Concern: Potential for wire chafing and arcing to conduit inside the tank. The float switch 

assemblies in Fuel Tank 1 and 2 are not repairable to the initial manufactured standards. The 

center tank and Boeing auxiliary tank (if installed) Float Switch and Liner are not repairable to 

the initial manufactured standards (refer to Boeing AMM 28-21-71).

During float switch replacement, a new float switch assembly must be used in Tanks 1 and 2, 

and a new float switch and liner system must be used for center and Boeing auxiliary fuel tank 

(if installed) as applicable. 

28-AWL-15 CDCCL N/A All

Center Fuel Tank Access Doors – Lightning Protection Bond

Concern: Potential for arcing or sparking inside the tank at the interface between the door and 

the tank structure as a result of a direct strike or conducting currents through the wing skin.

The following features must be maintained during center fuel tank access door installation per 

Boeing AMM 28-11-31:

Verify presence of a phenolic strip positioned around the outermost periphery of the door that 

mates with the wing skin inside the tank.

737-300, -400, -500 MAINTENANCE PLANNING DATA – AIRWORTHINESS LIMITATIONS – FUEL SYSTEMS

AWL NUMBER TASK INTERVAL APPLICABILITY DESCRIPTION

MAY 2009
D6-38278-CMR

BOEING PROPRIETARY - Copyright (c) - Unpublished Work - See title page for details Page 9.0-40

737-12345 AIRWORTHINESS LIMITATIONS/CERTIFICATION MAINTENANCE REQUIREMENTS

28-AWL-16 CDCCL N/A All

Main Fuel Tank Access Doors – Lightning Protection Bond

Concern: Potential for arcing or sparking inside the tank at the interface between the door and 

the tank structure as a result of a direct strike or conducting currents through the wing skin.

The following features must be maintained during main (wing) fuel tank access door 

installation per Boeing AMM 28-11-11:

1. Apply anti-corrosion compound to both sides of the knitted aluminum mesh gasket, and 

install the greased aluminum mesh gasket between the clamp ring and the lower wing skin. 

Due to the countersink, the aluminum mesh will contact the access door and establish the 

electrical conductivity between the access door and the wing skin using the clamp ring and 

fasteners torqued to the value specified in Boeing AMM 28-11-11.

Note: Not applicable to Surge Tank Access Doors with the NACA Vent Scoop and 

Pressure Relief Valve. 

737-300, -400, -500 MAINTENANCE PLANNING DATA – AIRWORTHINESS LIMITATIONS – FUEL SYSTEMS

AWL NUMBER TASK INTERVAL APPLICABILITY DESCRIPTION

MAY 2009
737-12345 AIRWORTHINESS LIMITATIONS/CERTIFICATION MAINTENANCE REQUIREMENTS

D6-38278-CMR

BOEING PROPRIETARY - Copyright (c) - Unpublished Work - See title page for details Page 9.0-41

28-AWL-17 CDCCL N/A All

Surge Tank Access Doors – Lightning Protection Bond

Concern: Potential for arcing or sparking inside the tank at the interface between the door and 

the tank structure as a result of a direct strike or conducting currents through the wing skin.

During surge tank access door installation, perform the following actions per Boeing AMM 

28-11-11:

Clean the countersinks on the access door. 

If the Pressure Relief Valve is removed and replaced, maintain the electrical fay surface bond 

between the pressure relief valve and the door 0.010 ohms (10 milliohms) or less per Boeing 

AMM 28-13-41.

If the Type I Flame Arrestor is removed and replaced, verify the electrical bond from the flame 

arrestor to the door assembly is 0.010 ohms (10 milliohms) or less per Boeing AMM 28-13-31.

If the Air Vent Scoop of the Type II Flame Arrestor is removed and replaced, maintain the 

following electrical bonds per Boeing AMM 28-13-31:

1. Prepare the electrical fay surface from the upper surface of the door assembly to the lower 

surface of the air vent scoop.

2. Before the surface is sealed, verify the electrical surface bond from the door assembly to 

the air vent scoop is 0.0025 ohms (2.5 milliohms) or less.

3. After the surface is sealed, verify the electrical bond from the air vent scoop to the door 

assembly is 0.010 ohms (10 milliohms) or less.

Install the door using the same part number conductive fasteners and torque to that specified 

in the Boeing AMM.

28-AWL-18 CDCCL N/A

737-300/400/500 

airplanes that have 

incorporated 

Service Bulletin 

737-28A1263

Fuel Boost Pump Wires In Conduit Installation – In Fuel Tank

Concern: Potential for the boost pump wiring to chafe and arc in the conduit to provide an 

ignition source in the fuel tank. The boost pump wires that are in the conduits in the fuel tanks 

have incorporated a Teflon sleeve to protect from wire chafing per Boeing Service Bulletin 737-

28A1263 (FAA AD 2007-24-02). The wiring also has a jacket to provide chafing protection. 

Ensure the following condition exists when replacing pump wiring or wiring conduit:

- Jacketed wiring and a Teflon sleeve.

The Teflon sleeve is not repairable. Whenever the wiring in conduit or the conduit is removed, 

new Teflon sleeve must be installed.

737-300, -400, -500 MAINTENANCE PLANNING DATA – AIRWORTHINESS LIMITATIONS – FUEL SYSTEMS

AWL NUMBER TASK INTERVAL APPLICABILITY DESCRIPTION

MAY 2009
D6-38278-CMR

BOEING PROPRIETARY - Copyright (c) - Unpublished Work - See title page for details Page 9.0-42

737-12345 AIRWORTHINESS LIMITATIONS/CERTIFICATION MAINTENANCE REQUIREMENTS

28-AWL-19 CDCCL N/A All

Resetting of Tripped Fuel Pump Circuit Breakers or Ground Fault Interrupters (GFIs)

Concern: Potential for arcing or sparking inside the tank between fuel pumps and fuel pump 

housings and outside the tank between pump wiring and structure in flammable leakage 

zones.

Verify it is safe to reset the circuit breaker(s) or GFIs by following the applicable OEM 

troubleshooting procedures. Fault(s) that resulted in circuit breaker or GFI trip must be isolated 

and corrected prior to reset.

28-AWL-20 ALI 1 YR

737-300/400/500 

airplanes that have 

incorporated 

Service Bulletin 

737-28A1216

Center Tank Fuel Boost Pump Automatic Shutoff System

Concern: Dry running the center tank fuel pumps has the potential for single failure ignition 

sources developing at the pump inlet due to either frictional heating or sparking as a result of 

FOD contacting the pump rotating elements, rotating elements contacting stationary parts, or 

hot journal bearings due to bearing contamination or failure.

The automatic shutoff system is installed and designed to limit continuous dry running 

condition to 15 seconds.

The following test is required in order to protect against latent faults:

Functionally check the center tank fuel boost pump automatic shutoff system per 

AMM 28-22-00.

28-AWL-21 ALI 1 YR

737-300/400 

airplanes with 

Boeing certified 

auxiliary fuel tanks 

installed, that have 

incorporated 

Service Bulletin 

737-28A1216

Auxiliary Tank Fuel Boost Pump Automatic Shutoff System

Concern: Dry running the auxiliary tank fuel pumps has the potential for single failure ignition 

sources developing at the pump inlet due to either frictional heating or sparking as a result of 

FOD contacting the pump rotating elements, rotating elements contacting stationary parts, or 

hot journal bearings due to bearing contamination or failure.

The automatic shutoff system is installed and designed to limit continuous dry running 

condition to 15 seconds.

The following test is required in order to protect against latent faults:

Functionally check the auxiliary tank fuel boost pump automatic shutoff system per 

AMM 28-22-00.

737-300, -400, -500 MAINTENANCE PLANNING DATA – AIRWORTHINESS LIMITATIONS – FUEL SYSTEMS

AWL NUMBER TASK INTERVAL APPLICABILITY DESCRIPTION

MAY 2009
737-12345 AIRWORTHINESS LIMITATIONS/CERTIFICATION MAINTENANCE REQUIREMENTS

D6-38278-CMR

BOEING PROPRIETARY - Copyright (c) - Unpublished Work - See title page for details Page 9.0-43

28-AWL-22 ALI 1 YR

737-300/400/500 

airplanes that have 

incorporated 

Service Bulletin 

737-28A1212

Boost Pump Ground Fault Interrupter (GFI)

Concern: Potential for pump housing burn-through, either internal or external to the fuel tank, 

as a result of major arcing due to electrical failure (i.e., damaged electrical connector, stator 

windings or leadwire to housing/end cap shorting).

The GFI is designed to detect electrical faults and open the circuit prior to pump housing burnthrough.

The following maintenance check is required in order to ensure continued functionality of the 

GFI circuit:

Operational check the GFI of all AC Fuel Tank Boost Pumps per AMM 28-22-41.

28-AWL-23 ALI 1 YR

737-300/400/500 

airplanes that have 

incorporated 

Service Bulletin 

737-28A1227

Center Tank Fuel Boost Pump Power Failed On Protection System

Concern: Dry running the center tank fuel pumps has the potential for single failure ignition 

sources developing at the pump inlet due to either frictional heating or sparking as a result of 

FOD contacting the pump rotating elements, rotating elements contacting stationary parts or 

hot journal bearings due to bearing contamination or failure.

The power failed on protection system is installed and designed in order to protect against a 

single failure (i.e. wiring faults or a welded fuel pump control relay) keeping power on the pump 

when the associated fuel pump control switch is positioned to OFF.

The following test is required in order to protect against latent faults:

Verify continued functionality of the center tank fuel boost pump Power Failed On Protection 

System per AMM 28-22-00.

28-AWL-24 ALI 1 YR

737-300/400/500 

airplanes with 

Auxiliary fuel tanks 

that have 

incorporated 

Service Bulletin 

737-28A1227

Auxiliary Fuel Tank Boost Pump Power Failed On Protection System

Concern: Dry running the auxiliary tank fuel pumps has the potential for single failure ignition 

sources developing at the pump inlet due to either frictional heating or sparking as a result of 

FOD contacting the pump rotating elements, rotating elements contacting stationary parts or 

hot journal bearings due to bearing contamination or failure.

The power failed on protection system is installed and designed in order to protect against a 

single failure (i.e. wiring faults or a welded fuel pump control relay) keeping power on the pump 

when the associated fuel pump control switch is positioned to OFF.

The following test is required in order to protect against latent faults:

Verify continued functionality of the auxiliary tank fuel boost pump Power Failed On Protection 

System per AMM 28-22-00.

737-300, -400, -500 MAINTENANCE PLANNING DATA – AIRWORTHINESS LIMITATIONS – FUEL SYSTEMS

AWL NUMBER TASK INTERVAL APPLICABILITY DESCRIPTION

MAY 2009
D6-38278-CMR

BOEING PROPRIETARY - Copyright (c) - Unpublished Work - See title page for details Page 9.0-44

737-12345 AIRWORTHINESS LIMITATIONS/CERTIFICATION MAINTENANCE REQUIREMENTS

D. AIRWORTHINESS LIMITATIONS – NITROGEN GENERATION SYSTEMS

The following list of AWLs (ALIs and CDCCLs) contains FAA approved scheduled inspections and design limitations for operators to incorporate into their maintenance 

program for this type design to meet the requirements for the introduction of Flammability Reduction Means (FRM) Nitrogen Generation System (NGS). The FAA Final 

Flammability Rule, E8-16084, requires maintenance instructions and control limitations for certain NGS critical design configurations. § 25.981 also requires AWLs to 

preclude ignition sources inside the fuel tank that may be introduced by the addition of NGS. 

E8-16084, Final Flammability Rule, Paragraph III(F), Section 7, Identification of Airworthiness Limitations: Paragraph M25.4(a) requires that if FRM is used 

to comply with Paragraph M25.1, airworthiness limitations must be identified for all maintenance or inspection tasks required to identify failures of 

components within the FRM that are needed to meet Paragraph M25.1. NGS AWLs are mandatory maintenance actions that ensure that unsafe conditions 

that arise due to NGS failures do not occur or are not introduced into the airplane as a result of configuration changes, repairs, alterations, or deficiencies 

in the NGS maintenance program throughout the operational life of the airplane.

AUG 2010
737-12345 AIRWORTHINESS LIMITATIONS/CERTIFICATION MAINTENANCE REQUIREMENTS

D6-38278-CMR

BOEING PROPRIETARY - Copyright (c) - Unpublished Work - See title page for details Page 9.0-45

AIRWORTHINESS LIMITATIONS – NITROGEN GENERATION SYSTEM TASKS

AWL

NUMBER TASK INTERVAL APPLICABILITY DESCRIPTION

47-AWL-01 CDCCL N/A

Airplanes that 

have incorporated 

Service Bulletin 

737-47-1004 or 

737-47-1007

Lightning Protection – NGS Nitrogen Enriched Air (NEA) Distribution Line Fuel Tank Penetration

Concern: Potential for arcing or sparking inside the tank at the interface between the bulkhead 

fitting and the spar during a lightning strike event.

The following must be maintained if the bulkhead fitting is removed and replaced or re-installed 

(refer to Boeing AMM 47-21-07):

1. Install the same part number bulkhead fitting.

2. Verify electrical fay surface bond from the bulkhead fitting to the rear spar structure inside

 the tank is 0.0005 ohms (0.5 milliohms) or less.

3. Install fillet seal on both the inside and outside surfaces of the rear spar around the perimeter

 of the bulkhead fitting and jam nut.

NOTE: The bulkhead fitting is a special part which has an integral flame arrestor. Any change to

 this part requires approval by the Seattle FAA ACO.

47-AWL-02 CDCCL N/A

Airplanes that 

have incorporated 

Service Bulletin 

737-47-1004 or 

737-47-1007

Lightning Protection – NGS NEA Distribution Line Fuel Tank Penetration

Concern: Potential for arcing, sparking or filament heating inside the tank at the interface between 

the dielectric isolator hose and the NEA tubing during a lightning strike event.

The NGS installation is designed to prevent lightning currents from entering the center wing fuel 

tank by adding a dielectric isolator hose in the wheel well at the rear spar bulkhead fitting in the 

NEA distribution line. The isolator hose must be maintained if the dielectric isolator hose or 

attached tubing are removed and replaced or reinstalled (refer to Boeing AMM 47-21-00 and 

AMM 47-21-07).

JUL 2011
D6-38278-CMR

BOEING PROPRIETARY - Copyright (c) - Unpublished Work - See title page for details Page 9.0-46

737-12345 AIRWORTHINESS LIMITATIONS/CERTIFICATION MAINTENANCE REQUIREMENTS

47-AWL-03 CDCCL N/A

Airplanes that 

have incorporated 

Service Bulletin 

737-47-1005 or 

737-47-1008

Nitrogen Generation System (NGS) – Flammability Exposure and Performance

Concern: Airplane alterations may impact the performance of the NGS and hence the flammability 

of the Center Wing Fuel Tank.

Background: The NGS is designed to provide the proper level of nitrogen to the center wing tank 

in order to reduce the flammability exposure by reducing the oxygen content of the ullage. The 

flammability exposure is also affected by the temperature of the fuel. The following are critical 

features of the airplane that, if altered, can negatively affect the performance of the NGS which in 

turn may increase the center fuel tank flammability exposure beyond the limits of 14 Code of 

Federal Regulations, Section 25.981 at Amendment 25-125, utilizing the equivalent level of safety 

finding described in FAA Memorandum PS05-0177-P-2.

1. Transferring air (20.9% oxygen) to the center fuel tank will dilute the nitrogen rich 

atmosphere created by the NGS in the fuel tank. Some Auxiliary Fuel Tank installations 

transfer air to the center wing tank as part of venting and fuel transfer. 

2. NGS performance depends on bleed air pressure in the bleed air cross-over manifold 

supplied by the engines.

3. Certification of the NGS depends on the inherent flammability of the center fuel tank 

without NGS installed. Center tank flammability is a direct function of fuel tank 

temperature. Any heat sources around the tank, heat sources introduced into the tank 

(such as warm fuel or new heat exchangers), or changes that would cause heat to be 

retained (such installation of blankets adjacent to tank walls) could affect fuel tank 

flammability in a negative manner.

CDCCL: Any design change that affects the vent system by adding air to the center tank, reduces 

the bleed pressure in the cross-over manifold during any phase of flight or ground operations, or 

adds any heat to the center wing fuel tank or increases heat retention of the center wing fuel tank 

is not allowed without an FAA approved analysis to show that the change, or combination of 

changes, does not affect the NGS performance per the requirements of 14 CFR Section 

25.981(b), Amendment 25-125 utilizing the equivalent level of safety finding described in FAA 

Memorandum PS05-0177-P-2

See Boeing AMM Chapter 28 for a description of the Fuel System. See Boeing AMM Chapter 47 

for a description of the NGS.

AWL

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47-AWL-04 ALI 22,500 FH

Airplanes that 

have incorporated 

Service Bulletin 

737-47-1005 or 

737-47-1008

Nitrogen Generation System – Thermal Switch Functional and Operational Check

Concern: Latent Failure of the Thermal Switch removes a layer of protection against fuel tank 

ignition by hot bleed air.

The NGS uses engine bleed air from the engine bleed system cross-over manifold to generate 

nitrogen to reduce the flammability of the center fuel tank. The NGS has features to prevent 

directly feeding hot bleed air into the fuel tank. The Thermal Switch provides a redundant backup 

to the NGS controller to protect the Air Separation Module (ASM) and prevent hot bleed air from 

entering the fuel tank. The Thermal Switch backup feature is a latent (not detected) failure and 

must be tested to maintain certification of the NGS.

Perform a functional and operational check of the Thermal Switch to ensure integrity of the 

Thermal Switch (refer to Boeing AMM 47-43-02).

47-AWL-05 ALI 14,500 FH

Airplanes that 

have incorporated 

Service Bulletin 

737-47-1005 or 

737-47-1008

Nitrogen Generation System – NEA Distribution Ducting Inspection

Concern: The NEA Distribution System ducting outside the fuel tank may fail latently allowing NEA 

to leak without reaching the fuel tank, resulting in the fuel tank not reaching required inert levels.

Inspect the NEA distribution lines from the ASM to the fuel tank rear spar for damage and leaks 

(refer to Boeing AMM ATA 47-21-00).

47-AWL-06 CDCCL N/A

Airplanes that 

have incorporated 

Service Bulletin 

737-47-1005 or 

737-47-1008

Industry Fleet Average Flammability Exposure

Concern: NGS performance is dependent on industry descent times. Industry efforts to reduce 

descent time may result in NGS performance that does not meet FAA requirements.

Fleet Average flammability exposure for the fuel tanks with flammability reduction of this airplane 

type must be maintained in accordance with 14 CFR Part 25, Appendix M. Boeing will monitor 

U.S. descent statistics and, if necessary to maintain compliance, will publish service information. 

If Boeing publishes such service information, this CDCCL requires either that operators implement 

these FAA-approved design changes or that operators implement other design changes or 

operational procedural changes approved by the Seattle FAA ACO to maintain compliance with 

14 CFR Part 25, Appendix M.

NOTE: This CDCCL does not require individual operators to monitor descent rates of their fleets.

 Boeing will monitor U.S. descent statistics and provide any needed service instructions to

 operators. To prevent increasing flammability exposure above permissible levels, this

 CDCCL requires operators to incorporate future Boeing published service instructions

 denoted to maintain compliance with this CDCCL, or other approved actions, within the

 compliance times stated in the service instructions.

AWL

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