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PROPOSED AD THE BOEING COMPANY: Docket No. FAA-2020-0341; Product Identifier 2020-NM-017-AD.
(a) COMMENTS DUE DATE

    The FAA must receive comments by June 22, 2020.

(b) AFFECTED ADS

    This AD affects the ADs specified  in paragraphs (b)(1) through (6) of
    this AD.

(1) AD 2008-06-03,  Amendment 39-15415  (73 FR 13081, March 12, 2008) ("AD
    2008-06-03").

(2) AD 2008-10-10 R1,  Amendment 39-16164  (75 FR 1529,  January 12, 2010)
    ("AD 2008-10-10 R1").

(3) AD 2008-17-15,  Amendment 39-15653 (73 FR 50714, August 28, 2008) ("AD
    2008-17-15").

(4) AD 2011-18-03,  Amendment 39-16785 (76 FR 53317, August 26, 2011) ("AD
    2011-18-03").

(5) AD 2013-15-17,  Amendment 39-17533 (78 FR 52838, August 27, 2013) ("AD
    2013-15-17").

(6) AD 2018-20-24, Amendment 39-19458 (83 FR 51815, October 15, 2018) ("AD
    2018-20-24").

(c) APPLICABILITY

    This  AD  applies  to  The Boeing Company  Model 737-600, -700, -700C,
    -800, -900, and -900ER series airplanes, certificated in any category,
    with an original airworthiness certificate or original export certifi-
    cate of airworthiness issued on or before December 18, 2019.

(d) SUBJECT

    Air Transport Association (ATA) of America Code 71, Powerplant.

(e) UNSAFE CONDITION

    This AD was prompted by significant changes made to the  airworthiness
    limitations (AWLs) related  to fuel tank  ignition prevention and  the
    nitrogen generation system. The FAA is issuing this AD to address  the
    development of an  ignition source inside  the fuel tanks  and also to
    prevent increasing the flammability exposure of the center fuel  tank,
    which could  lead to  fuel tank  explosion and  consequent loss of the
    airplane.

(f) COMPLIANCE

    Comply with this AD within the compliance times specified,  unless al-
    ready done.

(g) MAINTENANCE OR INSPECTION PROGRAM REVISION

    Within 60 days after the effective date of this AD,  revise the exist-
    ing maintenance or inspection  program, as applicable, to  incorporate
    the information  specified in  Section A,  including Subsections A.1.,
    A.2.,  and  A.3,  of  Boeing  737-600/700/700C/800/900/900ER   Special
    Compliance Items/Airworthiness Limitations, D626A001-9-04, dated April
    2019; except  as provided  by paragraph  (h) of  this AD.  The initial
    compliance times  for the  airworthiness limitation  instruction (ALI)
    tasks  are  within the  applicable  compliance times  specified  in in
    paragraphs (g)(1) through (14) of this AD.

(1) For AWL No. 28-AWL-01,  "External Wires Over Center Fuel Tank:" Within
    120 months after  the date of  issuance of the  original airworthiness
    certificate or  the original  export certificate  of airworthiness, or
    within 120 months  after the most  recent inspection was  performed as
    specified in AWL No. 28-AWL-01, whichever is later.

(2) For  AWL  No. 28-AWL-03,  "Fuel Quantity Indicating System  (FQIS)-Out
    Tank Wiring Lightning Shield to Ground Termination:" Within 120 months
    after the date of  issuance of the original  airworthiness certificate
    or the  original export  certificate of  airworthiness, or  within 120
    months after the most recent inspection was performed as specified  in
    AWL No. 28-AWL-03, whichever is later.

(3) For AWL No. 28-AWL-19,  "Center Tank Fuel Boost Pump Automatic Shutoff
    System:" Within 12 months after  the date of issuance of  the original
    airworthiness  certificate  or  the  original  export  certificate  of
    airworthiness, within  12 months  after accomplishment  of the actions
    specified in Boeing Service Bulletin 737-28A1206, or within 12  months
    after the most recent inspection was performed as specified in AWL No.
    28-AWL-19, whichever is latest. This  AWL does not apply to  airplanes
    that have complied with paragraph (s) of AD 2011-18-03.

(4) For AWL No. 28-AWL-20,  "Over-Current and Arcing Protection Electrical
    Design Features Operation-Boost Pump Ground Fault Interrupter  (GFI):"
    Within  12  months  after  the  date  of  issuance  of  the   original
    airworthiness  certificate  or  the  original  export  certificate  of
    airworthiness, within  12 months  after accomplishment  of the actions
    specified in Boeing Service Bulletin 737-28A1201, or within 12  months
    after the most recent inspection was performed as specified in AWL No.
    28-AWL-20, whichever is latest. For airplanes that have complied  with
    paragraph  (g)(2)(ii)  of  AD 2011-20-07,  Amendment  39-16818  (76 FR
    60710, September 30, 2011), the operational test for left center  tank
    fuel boost pump relay R54 and right center tank fuel boost pump  relay
    R55 does not apply.

(5) For  AWL  No. 28-AWL-23,  "Center Tank Fuel Boost Pump Power Failed On
    Protection System:" Within 12 months after the date of issuance of the
    original airworthiness certificate or the original export  certificate
    of airworthiness, within 12 months after accomplishment of the actions
    specified in Boeing Service Bulletin 737-28A1248, or within 12  months
    after the most recent inspection was performed as specified in AWL No.
    28-AWL-23, whichever is latest. This  AWL does not apply to  airplanes
    that have complied with paragraph (s) of AD 2011-18-03.

(6) For AWL No. 28-AWL-24, "Spar Valve Motor Operated Valve (MOV) Actuator
    -Lightning and  Fault Current  Protection Electrical  Bond:" Within 72
    months after accomplishment of the actions specified in Boeing Service
    Bulletin  737-28A1207,  or  within 72  months  after  the most  recent
    inspection was performed as specified in AWL No. 28-AWL-24,  whichever
    is later.

(7) For  AWL  No. 28-AWL-29,  "Full Cushion Clamps and Teflon Sleeving (If
    Installed) Installed on Out-of-Tank Wire Bundles Installed on Brackets
    that are  Mounted Directly  on the  Fuel Tanks:"  For airplanes having
    line numbers (L/N) 1 through  1754 inclusive, within 120 months  after
    accomplishment of  the actions  specified in  Boeing Service  Bulletin
    737-57A1279. For airplanes having L/N 1755 and subsequent, within  120
    months  after  the  date of  issuance  of  the original  airworthiness
    certificate or  the original  export certificate  of airworthiness, or
    within 48  months after  the effective  date of  this AD, whichever is
    later.

(8) For AWL No. 28-AWL-35,  "Fuel Quantity Indicating System (FQIS)-Center
    Fuel  Tank In-Tank  Component and  Wire Harness  Protection  Features-
    -Separation from Center Tank  Internal Structure:" For airplanes  that
    have  incorporated  Boeing Service  Bulletin  737-28-1356, within  120
    months after accomplishment of the actions specified in Boeing Service
    Bulletin  737-28-1356,  or within  120  months after  the  most recent
    inspection was performed as specified in AWL No. 28-AWL-35,  whichever
    is later.

(9) For AWL No. 28-AWL-37, "Fuel Quantity Indicating System (FQIS) - Built
    in Test Equipment  (BITE) Test:" For  airplane L/Ns 6987  and 7000 and
    subsequent, within  750 flight  hours since  the date  the most recent
    BITE  test was  accomplished as  specified  in  AWL No.  28-AWL-37, or
    within 750 flight hours after the effective date of this AD, whichever
    is later.

(10) For  AWL No. 47-AWL-04,  "Nitrogen Generation System-Thermal Switch:"
     Within 22,500 flight hours after the date of issuance of the original
     airworthiness  certificate  or  the  original  export  certificate of
     airworthiness, within 22,500 flight hours after accomplishment of the
     actions specified in Boeing  Service Bulletin 737-47-1003, or  within
     22,500 flight hours after the most recent inspection was performed as
     specified in AWL No. 47-AWL-04, whichever is latest.

(11) For AWL No. 47-AWL-06, "Nitrogen Generation System (NGS) - Cross Vent
     Check Valve:" Within 13,000 flight  hours after the date of  issuance
     of  the original  airworthiness certificate  or  the  original export
     certificate  of  airworthiness,  within  13,000  flight  hours  after
     accomplishment of  the actions  specified in  Boeing Service Bulletin
     737-47-1003,  or within  13,000 flight  hours after  the most  recent
     inspection was performed as specified in AWL No. 47-AWL-06, whichever
     is latest.

(12) For AWL No. 47-AWL-07, "Nitrogen Generation System (NGS)-Nitrogen En-
     riched Air (NEA) Distribution Ducting Integrity:" Within 6,500 flight
     hours  after  the  date of  issuance  of  the original  airworthiness
     certificate  or  the original  export  certificate of  airworthiness,
     within  6,500  flight  hours  after  accomplishment  of  the  actions
     specified in  Boeing Service  Bulletin 737-47-1003,  or within  6,500
     flight  hours  after  the most  recent  inspection  was performed  as
     specified in AWL No. 47-AWL-07, whichever is latest.

(13) For AWL No. 47-AWL-09,  "Nitrogen Generation System - Oxygen Sensor:"
     Within 18,000 flight hours after the date of issuance of the original
     airworthiness  certificate  or  the  original  export  certificate of
     airworthiness, or within  18,000 flight hours  after the most  recent
     replacement  was  performed as  specified  in AWL  No.  47-AWL-09, or
     within 12 months  after the effective  date of this  AD, whichever is
     latest.

(14) For AWL No. 28-AWL-101,  "Engine Fuel Suction Feed Operational Test:"
     Within 7,500 flight hours or 36 months, whichever occurs first, after
     the date of issuance of the original airworthiness certificate or the
     original export certificate of airworthiness; or within 7,500  flight
     hours or  36 months,  whichever occurs  first, after  the most recent
     inspection  was  performed  as  specified  in  AWL  No.   28-AWL-101;
     whichever is later.

(h) ADDITIONAL ACCEPTABLE WIRE TYPES AND SLEEVING

    As an option, when accomplishing the actions required by paragraph (g)
    of this AD, the changes specified in paragraphs (h)(1) and (2) of this
    AD are acceptable.

(1) Where AWL No. 28-AWL-05 identifies wire types BMS 13-48, BMS 13-58 and
    BMS 13-60,  the following wire types  are acceptable:  MIL-W-22759/16,
    SAE AS22759/16 (M22759/16), MIL-W-22759/32, SAE AS22759/32 (M22759/32)
    MIL-W-22759/34,   SAE  AS22759/34  (M22759/34),   MIL-W-22759/41,  SAE
    AS22759/41 (M22759/41),  MIL-W-22759/86,  SAE AS22759/86  (M22759/86),
    MIL-W-22759/87,  SAE AS22759/87 (M22759/87),  MIL-W-22759/92,  and SAE
    AS22759/92 (M22759/92);  and MIL-C-27500 and NEMA WC 27500 cables con-
    structed  from  these military  or  SAE specification  wire  types, as
    applicable.

(2) Where  AWL  No. 28-AWL-05  identifies TFE-2X Standard  wall  for  wire
    sleeving,  the following sleeving materials  are  acceptable:  Roundit
    2000NX and Varglas Type HO, HP, or HM.

(i) NO ALTERNATIVE ACTIONS,  INTERVALS,  OR  CRITICAL DESIGN CONFIGURATION
    CONTROL LIMITATIONS (CDCCLS)

    Except as  provided in  paragraph (h)  of this  AD, after the existing
    maintenance  or inspection  program has  been revised  as required  by
    paragraph (g) of this AD, no alternative actions (e.g.,  inspections),
    intervals, or CDCCLs  may be used  unless the actions,  intervals, and
    CDCCLs are approved as an  alternative method of compliance (AMOC)  in
    accordance with the procedures specified in paragraph (k) of this AD.

(j) TERMINATING ACTION FOR CERTAIN AD REQUIREMENTS

    Accomplishment of the  revision required by  paragraph (g) of  this AD
    terminates the requirements specified in paragraphs (j)(1) through (6)
    of this AD for that airplane.

(1) The revision required by paragraphs (h) and (h)(1) of AD 2008-06-03.

(2) All requirements of AD 2008-10-10 R1.

(3) The revision required by paragraph (g) of AD 2008-17-15.

(4) The revision required by paragraph (k) of AD 2011-18-03.

(5) All requirements of AD 2013-15-17.

(6) All requirements of AD 2018-20-24.

(k) ALTERNATIVE METHODS OF COMPLIANCE (AMOCS)

(1) The  Manager,  Seattle ACO Branch,  FAA,  has the authority to approve
    AMOCs for this AD, if requested  using the procedures found in 14  CFR
    39.19. In  accordance with  14 CFR  39.19, send  your request  to your
    principal  inspector  or  local Flight  Standards District  Office, as
    appropriate. If  sending information  directly to  the manager  of the
    certification  office,  send  it  to  the  attention  of  the   person
    identified in paragraph (l)(1) of this AD. Information may be  emailed
    to: 9-ANM-Seattle-ACO-AMOC-Requests@faa.gov.

(2) Before using any approved AMOC,  notify your appropriate principal in-
    spector,  or  lacking a principal inspector,  the manager of the local
    flight standards district office/certificate holding district office.

(3) An AMOC  that  provides  an acceptable level of safety may be used for
    any repair, modification, or alteration  required by this AD if  it is
    approved by The Boeing Company Organization Designation  Authorization
    (ODA) that  has been  authorized by  the Manager,  Seattle ACO Branch,
    FAA,  to  make those  findings.  To be  approved,  the repair  method,
    modification  deviation,  or   alteration  deviation  must   meet  the
    certification  basis   of  the   airplane,  and   the  approval   must
    specifically refer to this AD.

(l) RELATED INFORMATION

(1) For more information about this AD,  contact Christopher Baker,  Aero-
    space Engineer,  Propulsion Section,  FAA,  Seattle  ACO Branch,  2200
    South 216th St.,  Des Moines, WA 98198;  phone and fax:  206-231-3556;
    email: Christopher.R.Baker@faa.gov.

(2) For  service  information  identified  in  this  AD,   contact  Boeing
    Commercial Airplanes,  Attention:  Contractual & Data Services (C&DS),
    2600 Westminster Blvd., MC 110-SK57, Seal Beach, CA 90740-5600;  tele-
    phone 562-797-1717;  internet https://www.myboeingfleet.com.  You  may
    view  this  service  information  at  the  FAA, Airworthiness Products
    Section, Operational Safety Branch, 2200 South 216th St.,  Des Moines,
    WA. For information  on the availability of this material  at the FAA,
    call 206-231-3195.

Issued on April 23, 2020. Lance T. Gant, Director, Compliance & Airworthi-
ness Division, Aircraft Certification Service.

DATES: The FAA must receive comments on this proposed AD by June 22, 2020.
PREAMBLE 

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2020-0341; Product Identifier 2020-NM-017-AD]
RIN 2120-AA64

Airworthiness Directives; The Boeing Company Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

-----------------------------------------------------------------------

SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD)
for certain The Boeing Company Model 737-600, -700, -700C, -800, -900,
and -900ER series airplanes. This proposed AD was prompted by
significant changes made to the airworthiness limitations (AWLs)
related to fuel tank ignition prevention and the nitrogen generation
system. This proposed AD would require revising the existing
maintenance or inspection program, as applicable, to incorporate the
latest revision of the AWLs. The FAA is proposing this AD to address
the unsafe condition on these products.

DATES: The FAA must receive comments on this proposed AD by June 22, 2020.

ADDRESSES: You may send comments, using the procedures found in 14 CFR
11.43 and 11.45, by any of the following methods:

Federal eRulemaking Portal: Go to https://www.regulations.gov. Follow the
instructions for submitting comments.

Fax: 202-493-2251.

Mail: U.S. Department of Transportation, Docket
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New
Jersey Avenue SE, Washington, DC 20590.

Hand Delivery: Deliver to Mail address above between 9
a.m. and 5 p.m., Monday through Friday, except Federal holidays.

For service information identified in this NPRM, contact Boeing
Commercial Airplanes, Attention: Contractual & Data Services (C&DS),
2600 Westminster Blvd., MC 110-SK57, Seal Beach, CA 90740-5600;
telephone 562-797-1717; internet https://www.myboeingfleet.com. You may
view this service information at the FAA, Airworthiness Products
Section, Operational Safety Branch, 2200 South 216th St., Des Moines,
WA. For information on the availability of this material at the FAA,
call 206-231-3195.

Examining the AD Docket

You may examine the AD docket on the internet at https://www.regulations.
gov by searching for and locating Docket No. FAA-2020-0341;
or in person at Docket Operations between 9 a.m. and 5 p.m.,
Monday through Friday, except Federal holidays. The AD docket contains
this NPRM, any comments received, and other information. The street
address for Docket Operations is listed above. Comments will be
available in the AD docket shortly after receipt.

FOR FURTHER INFORMATION CONTACT: Christopher Baker, Aerospace Engineer,
Propulsion Section, FAA, Seattle ACO Branch, 2200 South 216th St., Des
Moines, WA 98198; phone and fax: 206-231-3556; email:
Christopher.R.Baker@faa.gov.

SUPPLEMENTARY INFORMATION:

Comments Invited

The FAA invites you to send any written relevant data, views, or
arguments about this proposal. Send your comments to an address listed
under the ADDRESSES section. Include "Docket No. FAA-2020-0341;
Product Identifier 2020-NM-017-AD" at the beginning of your comments.
The FAA specifically invite comments on the overall regulatory,
economic, environmental, and energy aspects of this NPRM. The FAA will
consider all comments received by the closing date and may amend this
NPRM because of those comments.

The FAA will post all comments received, without change, to https://www.
regulations.gov, including any personal information you provide.
The FAA will also post a report summarizing each substantive verbal
contact received about this NPRM.

Discussion

The FAA has examined the underlying safety issues involved in fuel
tank explosions on several large transport airplanes, including the
adequacy of existing regulations, the service history of airplanes
subject to those regulations, and existing maintenance practices for
fuel tank systems. As a result of those findings, the FAA issued a
final rule titled "Transport Airplane Fuel Tank System Design Review,
Flammability Reduction and Maintenance and Inspection Requirements"
(66 FR 23086, May 7, 2001). In addition to new airworthiness standards
for transport airplanes and new maintenance requirements that rule
included Amendment 21-78, which established Special Federal Aviation
Regulation No. 88 ("SFAR 88") at 14 CFR part 21. Subsequently, SFAR
88 was amended by Amendment 21-82 (67 FR 57490, September 10, 2002;
corrected at 67 FR 70809, November 26, 2002), Amendment 21-83 (67 FR
72830, December 9, 2002; corrected at 68 FR 37735, June 25, 2003, to
change "21-82" to "21-83"), and Amendment 21-101 (83 FR 9162, March
5, 2018).

Among other actions, SFAR 88 requires certain type design (i.e.,
type certificate (TC) and supplemental type certificate (STC)) holders
to substantiate that their fuel tank systems can prevent ignition
sources in the fuel tanks. This requirement applies to type design
holders for large turbine-powered transport airplanes and for
subsequent modifications to those airplanes. It requires them to
perform design reviews and to develop design changes and maintenance
procedures if their designs do not meet the new fuel tank safety
standards. As explained in the preamble to the final rule published on
May 7, 2001, the FAA intended to adopt airworthiness directives to
mandate any changes found necessary to address unsafe conditions
identified as a result of these reviews.

In evaluating these design reviews, the FAA has established four
criteria intended to define the unsafe conditions associated with fuel
tank systems that require corrective actions. The percentage of
operating time during which fuel tanks are exposed to flammable
conditions is one of these criteria. The other three criteria address
the failure types under evaluation: single failures, single failures in
combination with another latent condition(s), and in-service failure
experience. For all four criteria, the evaluations included
consideration of previous actions taken that may mitigate the need for
further action.

The FAA has determined that the actions identified in this proposed
AD are necessary to reduce the potential of ignition sources inside
fuel tanks, which, in combination with flammable fuel vapors, could
result in fuel tank explosions and consequent loss of the airplane.

The FAA issued AD 2008-10-10 R1, Amendment 39-16164 (75 FR 1529,
January 12, 2010) ("AD 2008-10-10 R1") and AD 2018-20-24, Amendment
39-19458 (83 FR 51815, October 15, 2018) ("AD 2018-20-24"), which
apply to certain The Boeing Company Model 737-600, -700, -700C, -800,
and -900 series airplanes. AD 2008-10-10 R1 and AD 2018-20-24 require
incorporation of fuel system AWLs and also require an initial
inspection to phase in certain repetitive inspections, and repair if
necessary. The fuel system AWLs were developed to satisfy SFAR 88
requirements and included in the Airworthiness Limitations Section
(ALS) of the manufacturer's Instructions for Continued Airworthiness.
Since AD 2008-10-10 R1 and AD 2018-20-24 were issued, the ALS has been
significantly revised by the manufacturer to correct technical and
editorial errors and also to add new requirements. Those changes affect
the fuel system and nitrogen generation system AWLs.

The FAA proposes to adopt this new AD to require revising the
maintenance or inspection program, as applicable, to incorporate the
latest revision of the AWLs. The FAA is proposing this AD to prevent
the potential for ignition sources inside the fuel tanks and also to
prevent increasing the flammability exposure of the center fuel tank
caused by latent failures, alterations, repairs, or maintenance
actions, which could result in a fuel tank explosion and consequent
loss of an airplane.

The FAA has determined that accomplishing the revision required by
paragraph (g) of this proposed AD would terminate the following
requirements for that airplane:

All requirements of AD 2008-10-10 R1.

The revision required by paragraphs (h) and (h)(1) of AD
2008-06-03, Amendment 39-15415 (73 FR 13081, March 12, 2008).

The revision required by paragraph (g) of AD 2008-17-15,
Amendment 39-15653 (73 FR 50714, August 28, 2008).

The revision required by paragraph (k) of AD 2011-18-03,
Amendment 39-16785 (76 FR 53317, August 26, 2011).

All requirements of AD 2013-15-17, Amendment 39-17533 (78
FR 52838, August 27, 2013).

All requirements of AD 2018-20-24.

Related Service Information Under 1 CFR Part 51

The FAA reviewed Boeing 737-600/700/700C/800/900/900ER Special
Compliance Items/Airworthiness Limitations, D626A001-9-04, dated April
2019. This service information describes AWLs that include
airworthiness limitation instructions (ALIs) and critical design
configuration control limitations (CDCCLs) tasks related to fuel tank
ignition prevention and the nitrogen generation system. This service
information is reasonably available because the interested parties have
access to it through their normal course of business or by the means
identified in the ADDRESSES section.

FAA's Determination

The FAA is proposing this AD because the agency evaluated all the
relevant information and determined the unsafe condition described
previously is likely to exist or develop in other products of the same
type design.

Proposed AD Requirements

This proposed AD would require revising the existing maintenance or
inspection program, as applicable, to incorporate new or more
restrictive airworthiness limitations.

This proposed AD would require revisions to certain operator
maintenance documents to include new actions (e.g., inspections) and
CDCCLs. Compliance with these actions and CDCCLs is required by 14 CFR
91.403(c). For airplanes that have been previously modified, altered,
or repaired in the areas addressed by this proposed AD, the operator
may not be able to accomplish the actions described in the revisions.
In this situation, to comply with 14 CFR 91.403(c), the operator must
request approval for an alternative method of compliance according to
paragraph (k) of this proposed AD.

Differences Between This Proposed AD and the Service Information

The "description" column of AWL No. 28-AWL-20 identifies certain
operational tests. However, airplanes on which the actions specified in
paragraph (g)(2)(ii) of AD 2011-20-07, Amendment 39-16818 (76 FR 60710,
September 30, 2011), have been done are not required to do the
operational test for left center tank fuel boost pump relay R54 and
right center tank fuel boost pump relay R55.

Paragraph (g) of this proposed AD would require operators to revise
their existing maintenance or inspection program by incorporating, in
part, AWL No. 28-AWL-05, "Wire Separation Requirements for New Wiring
Installed in Proximity to Wiring That Goes Into the Fuel Tanks" in
Boeing 737-600/700/700C/800/900/900ER Special Compliance Items/
Airworthiness Limitations, D626A001-9-04, dated April 2019. Paragraph
(h) of this proposed AD would allow certain changes to be made to the
requirements specified in AWL No. 28-AWL-05 as an option.

Clarification of the Service Information

The "applicability" column of AWL No. 28-AWL-19 identifies
affected airplanes. For airplanes on which the actions specified in
paragraph (s) of AD 2011-18-03 have been done, incorporation of Boeing
Service Bulletin 737-28A1206 is not required. Therefore, those
airplanes are not affected by AWL No. 28-AWL-19 and are not required to
do the functional test.

The "applicability" column of AWL No. 28-AWL-23 identifies
affected airplanes. For airplanes on which the actions specified in
paragraph (s) of AD 2011-18-03 have been done, incorporation of Boeing
Service Bulletin 737-28A1248 is not required. Therefore, those
airplanes are not affected by AWL No. 28-AWL-23 and are not required to
do the functional test.

Costs of Compliance

The FAA estimates that this proposed AD affects 2,057 airplanes of
U.S. registry. The FAA estimates the following costs to comply with
this proposed AD:

The FAA determined that revising the existing maintenance or
inspection program takes an average of 90 work-hours per operator,
although the agency recognizes that this number may vary from operator
to operator. In the past, the FAA estimated that this action takes 1
work-hour per airplane. Since operators incorporate maintenance or
inspection program changes for their affected fleet(s), the FAA
determined that a per-operator estimate is more accurate than a per-
airplane estimate. Therefore, the FAA estimates the average total cost
per operator to be $7,650 (90 work-hours x $85 per work-hour).

Authority for This Rulemaking

Title 49 of the United States Code specifies the FAA's authority to
issue rules on aviation safety. Subtitle I, section 106, describes the
authority of the FAA Administrator. Subtitle VII: Aviation Programs,
describes in more detail the scope of the Agency's authority.

The FAA is issuing this rulemaking under the authority described in
Subtitle VII, Part A, Subpart III, Section 44701: "General
requirements." Under that section, Congress charges the FAA with
promoting safe flight of civil aircraft in air commerce by prescribing
regulations for practices, methods, and procedures the Administrator
finds necessary for safety in air commerce. This regulation is within
the scope of that authority because it addresses an unsafe condition
that is likely to exist or develop on products identified in this
rulemaking action.

Regulatory Findings

The FAA determined that this proposed AD would not have federalism
implications under Executive Order 13132. This proposed AD would not
have a substantial direct effect on the States, on the relationship
between the national Government and the States, or on the distribution
of power and responsibilities among the various levels of government.

For the reasons discussed above, I certify this proposed
regulation:

(1) Is not a "significant regulatory action" under Executive
Order 12866,

(2) Will not affect intrastate aviation in Alaska, and

(3) Will not have a significant economic impact, positive or
negative, on a substantial number of small entities under the criteria
of the Regulatory Flexibility Act.

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Incorporation by
reference, Safety.

The Proposed Amendment

Accordingly, under the authority delegated to me by the
Administrator, the FAA proposes to amend 14 CFR part 39 as follows:

PART 39--AIRWORTHINESS DIRECTIVES

1. The authority citation for part 39 continues to read as follows:

Authority: 49 U.S.C. 106(g), 40113, 44701.

Sec. 39.13 [Amended]

2. The FAA amends Sec. 39.13 by adding the following new airworthiness
directive (AD):