preamble attached >>>
ADs updated daily at www.Tdata.com
2017-04-11 THE BOEING COMPANY:
Amendment 39-18806; Docket No. FAA-2016-5468; Directorate Identifier 2015-NM-021-AD.

(a) EFFECTIVE DATE

    This AD is effective March 29, 2017.

(b) AFFECTED ADS

    None.

(c) APPLICABILITY

(1) This AD applies to all  The Boeing Company Model 737-600, -700, -700C,
    -800, and -900 series airplanes, certificated in any category.

(2) Installation of Supplemental Type Certificate (STC) ST00830SE (http://
    rgl.faa.gov/Regulatory_and_Guidance_Library/rgstc.nsf/0/184DE9A71EC3FA
    5586257EAE00707DA6?OpenDocument&Highlight=st00830se)  does not  affect
    the ability to accomplish the actions required by this AD.  Therefore,
    for  airplanes  on  which  STC ST00830SE  is  installed,  a "change in
    product" alternative method of compliance (AMOC)  approval  request is
    not necessary to comply with the requirements of 14 CFR 39.17.

(d) SUBJECT

    Air Transport Association (ATA) of America Code 32, Landing Gear.

(e) UNSAFE CONDITION

    This AD was prompted by reports of paint deterioration on the  surface
    of the main  landing gear (MLG)  and early onset  of corrosion in  the
    trunnion bore of  the MLG outer  cylinder. We are  issuing this AD  to
    prevent stress corrosion cracking of the external surfaces of the MLG,
    which  could  result in  a  fracture of  the  MLG and  consequent  MLG
    collapse.

(f) COMPLIANCE

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

(g) INSPECTION FOR AFFECTED PART/SERIAL NUMBERS

    At  the  applicable  time  specified in  table  1  of  paragraph 1.E.,
    "Compliance,"  of  Boeing Special  Attention  Service Bulletin  737-32
    -1486, dated November 6, 2014, as revised by Boeing Special  Attention
    Service Bulletin 737-32-1486, Revision  1, dated April 1,  2015 ("SASB
    737-32-1486, R1"), except as required by paragraph (k)(1) of this  AD:
    Do the actions specified in paragraphs (g)(1) and (g)(2) of this AD in
    order to identify affected parts.

(1) Inspect  the  MLG to determine if it has any component installation or
    side strut assembly having a  part number and serial number  listed in
    Appendix D of Boeing  Special Attention Service Bulletin  737-32-1486,
    dated November 6, 2014,  as revised  by SASB  737-32-1486, R1;  except
    that the "Variable Number" column  of Appendix D is to  be disregarded
    in determining affected part and  serial numbers. An MLG that  has any
    MLG component installation or side strut assembly having a part number
    and serial  number listed  in Appendix  D of  Boeing Special Attention
    Service Bulletin 737-32-1486,  dated November 6, 2014,  as revised  by
    SASB  737-32-1486,  R1  is  an affected  part.  A  review  of airplane
    maintenance records is  acceptable in lieu  of this inspection  if the
    part number and  serial number of  the MLG component  installation and
    side strut assembly can be conclusively identified from that review.

(2) Do  a  records  review to determine if the MLG has been overhauled  by
    Messier Services Asia Pte Ltd (MS Asia) outside of the Boeing Exchange
    program from June 1, 2009, to July 31, 2013. If it is determined  that
    the MLG has been overhauled by MS Asia outside of the Boeing  Exchange
    program from June 1, 2009, to  July 31, 2013, that MLG is  an affected
    part. If from the records review it cannot be conclusively  determined
    that an overhauled  MLG was overhauled  by a maintenance,  repair, and
    overhaul (MRO)  facility other  than MS  Asia, or  if from the records
    review it cannot be conclusively determined that an MLG overhauled  by
    MS Asia was part of the Boeing Exchange Program from June 1, 2009,  to
    July 31, 2013, that MLG is an affected part.

(h) REQUIREMENTS FOR AFFECTED PARTS

    If any affected  part is identified  during the inspection  or records
    review required by  paragraph (g) of  this AD: At  the applicable time
    specified  in  table  3 of  paragraph  1.E.,  "Compliance," of  Boeing
    Special  Attention  Service Bulletin  737-32-1486,  dated  November 6,
    2014,  as  revised by  SASB  737-32-1486, R1,  except  as required  by
    paragraph (k)(1) of this AD,  do detailed inspections of the  external
    surfaces of the MLG, and  do all applicable related investigative  and
    corrective  actions,  in  accordance with  Parts 1,  3, and  4 of  the
    Accomplishment  Instructions  of  Boeing  Special  Attention   Service
    Bulletin 737-32-1486, dated November 6,  2014, as revised by SASB  737
    -32-1486,  R1,  except  as required  by paragraph  (k)(2) of  this AD.
    Repeat the inspections thereafter at the applicable time specified  in
    table 3 of paragraph  1.E., "Compliance," of Boeing  Special Attention
    Service Bulletin 737-32-1486,  dated November 6,  2014, as revised  by
    SASB  737-32-1486,  R1.  All  applicable  related  investigative   and
    corrective actions must be done before further flight.

(i) ADDITIONAL ACTIONS FOR GROUPS 1 AND 2, CONFIGURATION 1 AIRPLANES

    For airplanes that are identified as Groups 1 and 2, Configuration  1,
    in  Boeing  Special  Attention  Service  Bulletin  737-32-1486,  dated
    November 6, 2014, as revised by SASB 737-32-1486, R1, and that have an
    affected  part  identified  during the  inspection  or  records review
    required by paragraph (g) of this AD: At the applicable time specified
    in table 4 of paragraph 1.E, "Compliance," of Boeing Special Attention
    Service Bulletin 737-32-1486,  dated November 6,  2014, as revised  by
    SASB 737-32-1486, R1, except as  required by paragraph (k)(1) of  this
    AD,  do  a detailed  inspection  and bushing  replacement  of the  MLG
    trunnion  bore,  and  do  all  applicable  related  investigative  and
    corrective  actions,  in  accordance with  Parts 2,  5, and  6 of  the
    Accomplishment  Instructions  of  Boeing  Special  Attention   Service
    Bulletin 737-32-1486, dated November 6,  2014, as revised by SASB  737
    -32-1486, R1, except as required by paragraph (k)(2) of this AD.

(j) TERMINATING ACTION

(1) MLG replacement  in  accordance  with Part 8 of the Accomplishment In-
    structions of  Boeing  Special Attention Service Bulletin 737-32-1486,
    dated November 6, 2014, as revised by SASB 737-32-1486, R1, terminates
    the requirements of paragraphs (g), (h),  and (i) of this AD for  that
    MLG only.

(2) MLG component replacement in accordance with Part 4 of the Accomplish-
    ment Instructions of Boeing Special Attention Service Bulletin  737-32
    -1486, dated  November 6,  2014, as  revised by  SASB 737-32-1486, R1,
    terminates  the  requirements  of paragraph  (h) of  this AD  for that
    component only.

(3) MLG outer cylinder  replacement  in  accordance  with  Part 7  of  the
    Accomplishment  Instructions  of  Boeing  Special  Attention   Service
    Bulletin 737-32-1486,  dated November 6, 2014,  as revised by SASB 737
    -32-1486, R1, terminates the requirements of paragraph (i) of this  AD
    for that component only.

(k) EXCEPTIONS TO SERVICE INFORMATION SPECIFICATIONS

(1) Where paragraph 1.E., "Compliance" of Boeing Special Attention Service
    Bulletin 737-32-1486,  dated November 6, 2014,  as revised by SASB 737
    -32-1486, R1, specifies  a compliance time  "after the original  issue
    date of this service bulletin," this AD requires compliance within the
    specified compliance time after the effective date of this AD.

(2) Although Boeing Special Attention Service Bulletin 737-32-1486,  dated
    November 6, 2014, as  revised by  SASB 737-32-1486,  R1,  specifies to
    contact Boeing for repair  instructions, and specifies that  action as
    "RC" (Required for Compliance), this AD requires repair before further
    flight  using  a method  approved  in accordance  with  the procedures
    specified in paragraph (m) of this AD.

(l) PARTS INSTALLATION PROHIBITION

    As  of  the effective  date  of this  AD,  no person  may  install the
    following on any airplane identified  in paragraph (c)(1) of this  AD,
    unless either the  MLG or MLG  component has first  been overhauled as
    specified in  the corrective  actions of  paragraphs (h)  and (i),  as
    applicable,  of  this  AD,  or  the  MLG  or  MLG  component  has been
    overhauled using a method  approved in accordance with  the procedures
    specified in paragraph (m) of this AD.

(1) An MLG or MLG component having a part number and serial number identi-
    fied in Appendix D of SASB 737-32-1486, R1.

(2) An MLG that was overhauled between June 1, 2009, and July 31, 2013, by
    MS Asia.

(m) ALTERNATIVE METHODS OF COMPLIANCE (AMOCS)

(1) The Manager, Seattle Aircraft Certification Office (ACO), 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 ACO, send  it to the attention  of the
    person identified  in paragraph  (n) 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 Commercial Airplanes  Organization Designation
    Authorization (ODA) that has  been authorized by the  Manager, Seattle
    ACO,  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.

(4) Except as required by paragraph (k)(2) of this AD:  For service infor-
    mation that contains steps that  are labeled as RC,  the provisions of
    paragraphs (m)(4)(i) and (m)(4)(ii) of this AD apply.

(i) The steps labeled as RC,  including substeps under an RC step  and any
    figures identified in an RC step,  must be done to comply with the AD.
    If a step or substep is  labeled "RC Exempt," then the RC  requirement
    is removed  from that  step or  substep. An  AMOC is  required for any
    deviations to RC steps, including substeps and identified figures.

(ii) Steps not labeled  as  RC may be deviated from using accepted methods
     in accordance with the  operator's maintenance or inspection  program
     without  obtaining  approval  of  an  AMOC,  provided  the  RC steps,
     including  substeps  and identified  figures,  can still  be  done as
     specified,  and  the  airplane  can  be  put  back  in  an  airworthy
     condition.

(n) RELATED INFORMATION

    For  more  information about  this  AD, contact  Alan  Pohl, Aerospace
    Engineer,  Airframe  Branch,  ANM-120S, FAA,  Seattle  ACO,  1601 Lind
    Avenue SW., Renton, WA  98057-3356; phone: 425-917-6450; fax:  425-917
    -6590; email: alan.pohl@faa.gov.

(o) MATERIAL INCORPORATED BY REFERENCE

(1) The  Director  of  the  Federal Register approved the incorporation by
    reference (IBR) of  the service information  listed in this  paragraph
    under 5 U.S.C. 552(a) and 1 CFR part 51.

(2) You must use  this service information as applicable to do the actions
    required by this AD, unless the AD specifies otherwise.

(i) Boeing Special Attention Service Bulletin 737-32-1486,  dated November
    6, 2014.

(ii) Boeing  Special Attention  Service Bulletin 737-32-1486,  Revision 1,
     dated April 1, 2015.

(3) For Boeing 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.

(4) You may view this service information at the FAA,  Transport  Airplane
    Directorate, 1601 Lind Avenue SW., Renton, WA.  For information on the
    availability of this material at the FAA, call 425-227-1221.

(5) You  may  view  this  service  information  that  is  incorporated  by
    reference  at the National Archives and Records Administration (NARA).
    For information on the availability of this material at NARA, call 202
    -741-6030, or go to: http://www.archives.gov/federal-register/cfr/ibr-
    locations.html.

Issued  in  Renton,  Washington,  on  February 8, 2017.  Michael Kaszycki,
Acting  Manager,  Transport Airplane  Directorate,  Aircraft Certification
Service.

FOR FURTHER INFORMATION CONTACT: Alan Pohl,  Aerospace Engineer,  Airframe
Branch, ANM-120S,  FAA,  Seattle Aircraft Certification Office (ACO), 1601
Lind Avenue SW., Renton, WA 98057-3356; phone: 425-917-6450; fax: 425-917-
6590; email: alan.pohl@faa.gov.
PREAMBLE 

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2016-5468; Directorate Identifier 2015-NM-021-AD;
Amendment 39-18806; AD 2017-04-11]
RIN 2120-AA64

Airworthiness Directives; The Boeing Company Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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

SUMMARY: We are adopting a new airworthiness directive (AD) all The
Boeing Company Model 737-600, -700, -700C, -800, and -900 series
airplanes. This AD was prompted by reports of paint deterioration on
the surface of the main landing gear (MLG) and the early onset of
corrosion in the trunnion bore of the MLG outer cylinder. This AD
requires identifying affected parts, repetitive external surface
detailed inspections for damage of affected parts, and related
investigative and corrective actions if necessary. For certain
airplanes, this AD also requires a detailed inspection and bushing
replacement of the trunnion bore, and related investigative and
corrective actions if necessary. We are issuing this AD to address the
unsafe condition on these products.

DATES: This AD is effective March 29, 2017.
The Director of the Federal Register approved the incorporation by
reference of certain publications listed in this AD as of March 29,
2017.

ADDRESSES: For service information identified in this final rule,
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 referenced service information
at the FAA, Transport Airplane Directorate, 1601 Lind Avenue SW.,
Renton, WA. For information on the availability of this material at the
FAA, call 425-227-1221. It is also available on the Internet at http://www.
regulations.gov by searching for and locating Docket No. FAA-2016-5468.

Examining the AD Docket

You may examine the AD docket on the Internet at http://www.regulations.gov
by searching for and locating Docket No. FAA-2016-
5468; or in person at the Docket Management Facility between 9 a.m. and
5 p.m., Monday through Friday, except Federal holidays. The AD docket
contains this AD, the regulatory evaluation, any comments received, and
other information. The address for the Docket Office (phone: 800-647-
5527) is Docket Management Facility, U.S. Department of Transportation,
Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200
New Jersey Avenue SE., Washington, DC 20590.

FOR FURTHER INFORMATION CONTACT: Alan Pohl, Aerospace Engineer,
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office
(ACO), 1601 Lind Avenue SW., Renton, WA 98057-3356; phone: 425-917-
6450; fax: 425-917-6590; email: alan.pohl@faa.gov.

SUPPLEMENTARY INFORMATION:

Discussion

We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR
part 39 by adding an AD that would apply to all The Boeing Company
Model 737-600, -700, -700C, -800, and -900 series airplanes. The NPRM
published in the Federal Register on April 12, 2016 (81 FR 21497)
(``the NPRM''). The NPRM was prompted by reports of paint deterioration
on the surface of the MLG and the early onset of corrosion in the
trunnion bore of the MLG outer cylinder. The NPRM proposed to require
identifying affected parts, repetitive external surface detailed
inspections for damage of affected parts, and related investigative and
corrective actions, if necessary. For certain airplanes, the NPRM also
proposed to require a detailed inspection and bushing replacement of
the trunnion bore, and related investigative and corrective actions, if
necessary. We are issuing this AD to prevent stress corrosion cracking
of the external surfaces of the MLG, which could result in a fracture
of the MLG and consequent MLG collapse.

Comments

We gave the public the opportunity to participate in developing
this AD. The following presents the comments received on the NPRM and
the FAA's response to each comment.

Request To Withdraw the NPRM

Messier Services Asia Pte Ltd (MS Asia) explained that this
maintenance, repair, and overhaul (MRO) facility, located in Singapore,
has disclosed to Boeing that between November 2007 and December 2011,
painting performed by MS Asia on certain landing gear legs as part of
its overhaul service for Boeing did not fully conform to Boeing
instructions and specifications. MS Asia stated that this painting
error was disclosed to Boeing for Model 737 airplane landing gears
identified in Boeing Special Attention Service Bulletin 737-32-1486,
dated November 6, 2014, as revised by Boeing Special Attention Service
Bulletin 737-32-1486, Revision 1, dated April 1, 2015 (``SASB 737-32-
1486, R1'').
MS Asia refuted and continues to refute that the painting has
generated the potential onset of corrosion discovered on the MLG. MS
Asia explained that it had the opportunity to demonstrate to Boeing the
absence of links between these two events and is willing to reiterate
its technical demonstration to the FAA. MS Asia asserted that the NPRM
makes an incorrect statement and conclusion, and is without technical
evidence that the root cause of the corrosion detected on the trunnion
bore and the associated risk of fracture is the consequence of the
incorrect paint scheme application.
MS Asia also stated that the NPRM is creating confusion when it
refers to SAFRAN Messier-Bugatti-Dowty, and that the painting issues
only affect gears overhauled by MS Asia during the period of November
2007 to December 2011. MS Asia asserted that no painting issues have
affected landing gears overhauled by the MRO entity of Messier-Bugatti-
Dowty outside the period of November 2007 to December 2011.
From these statements, we infer that MS Asia is requesting we
withdraw the NPRM. We do not agree.
Landing gear components include materials that are very sensitive
to corrosion and cracking and are not tolerant of improper maintenance.
In particular, high strength steel, once corroded, can readily develop
cracks which could then propagate very rapidly and render inspection
programs ineffectual. This is why it is imperative that protective
finishes be applied as specified.
The determination of a connection between improper finish
application and the potential onset of corrosion was made by Boeing in
Boeing Special Attention Service Bulletin 737-32-1486, dated November
6, 2014, with review and concurrence by the FAA. This connection has
also been validated by extensive fleet experience.
MS Asia provided no definitive data to substantiate its statement
that there is not such a connection between its painting (application
of unqualified primer) and corrosion. It should also be noted that this
painting was only one of several discrepancies noted that indicated
improper maintenance. There is no refutation of the finding that the
components were not overhauled in accordance with Boeing instructions
and specifications. These instructions and specifications, or their
equivalent, are in turn included in operators' maintenance programs
that are approved by the governing regulatory authority.
We are willing to review data MS Asia might wish to submit
regarding this AD. However, this issue has been determined to be a
safety issue by both Boeing and the FAA, and the FAA has also
determined that it is not appropriate to withdraw the NPRM. If a future
review of submitted data substantiates MS Asia's claim that the root
cause of the corrosion detected on the trunnion bore and the associated
risk of fracture is not the consequence of the incorrect paint scheme
application, then we may grant relief through either additional
rulemaking or a global alternative method of compliance (AMOC).
We have not revised this final rule regarding a connection between
improper finish application and the potential onset of corrosion.
We note that the dates of the discrepant overhaul specified in
paragraph (g) of this AD differ from the dates given in Boeing Special
Attention Service Bulletin 737-32-1486, dated November 6, 2014, and in
MS Asia's comments. The dates in paragraph (g) of this AD were
determined by an investigation of MS Asia's maintenance records by an
FAA inspector. After that review of maintenance records by an FAA field
office, we concur with MS Asia's statement that this improper rework is
limited to their facility in Singapore. We have revised this final rule
to refer to MS Asia instead of SAFRAN Messier-Bugatti-Dowty to avoid
confusion regarding affected parts.

Requests for Clarification Regarding the Nose Landing Gear (NLG)

Boeing and the European Aviation Safety Agency (EASA) requested
that we clarify why the NPRM did not address actions specified in the
service information for the NLG.
We agree that there is a need to clarify. The discrepant rework
described in the Boeing service information does specify the NLG as
well as the MLG. We note that in the Boeing service information,
inspections of the MLG were specified for safety and were so labeled.
However, inspections of the NLG were not determined by Boeing to be a
safety issue. Those NLG inspections were labeled as economic
inspections. This determination is consistent with the FAA's safety
determination. Issues involving potential collapse of the NLG are
evaluated on a case-by-case basis, but are typically determined not to
be safety issues. In the event of failure of the NLG, the flight crew
normally retains adequate directional control of the airplane via
differential braking, engine thrust, and/or rudder. This is not the
case for MLG collapses. We have not changed this AD in this regard.

Request To Revise Corrective Action in Paragraph (i) of the Proposed AD

Boeing requested that we include Part 7 of the Accomplishment
Instructions of Boeing Special Attention Service Bulletin 737-32-1486,
dated November 6, 2014, in the applicable investigative and corrective
actions identified in paragraph (i) of the proposed AD. Boeing stated
that the replacement of the MLG outer cylinder in accordance with Part
7 should be allowed as an option for compliance with the requirements
of paragraph (i) of the proposed AD.
We have confirmed that Boeing's requested change to paragraph (i)
of this AD is not needed since Part 7 of the Accomplishment
Instructions of Boeing Special Attention Service Bulletin 737-32-1486,
dated November 6, 2014, is already cited in paragraph (j)(3) of this AD
as terminating action for the actions required by paragraph (i) of this
AD. We have not changed this AD in this regard.

Request To Clarify "New" Part

EASA stated that the NPRM does not explicitly state that
replacement with a new part is acceptable unless the new part belongs
to ``Appendix D (wrong batch).''
We are not sure what EASA intended by the term ``new.'' This would
ordinarily indicate a brand new part obtained from the design approval
holder or authorized supplier that has never previously been placed
into service. However, we infer from EASA's statement that it intends
the term to mean a different part than what is currently installed on
the airplane. If this is the case, then this issue is already addressed
in the service information. For example, for replacement of the entire
MLG, Part 8 of the Accomplishment Instructions of Boeing Special
Attention Service Bulletin 737-32-1486, dated November 6, 2014,
specifies that such replacement be accomplished with a serviceable MLG.
By definition, the components listed in Appendix D of SASB 737-32-1486,
R1 are not serviceable. We have not changed this AD in this regard.

Requests To Clarify/Revise Overhaul Procedures and Clarify Component
Installations


SunExpress requested clarification that overhaul of affected
components/assemblies specified in the service information is
terminating action for inspections. SunExpress stated that the service
information has a note specifying to not reinstall a removed component
and/or MLG on another airplane until overhaul is completed.
United Airlines (UAL) requested that we revise paragraph (l) of the
proposed AD to allow operators to install affected parts as long as
they have been overhauled using the component maintenance manual and
Boeing Special Attention Service Bulletin 737-32-1486, dated November
6, 2014, as revised by SASB 737-32-1486, R1. UAL stated that the
wording in paragraph (l) of the proposed AD implies that all affected
serial numbers would need FAA approval for repair/overhaul.
In addition, SunExpress requested clarification as to whether each
sub-part or sub-assembly under an MLG component installation is also
affected individually. SunExpress asked if, for example, a sub-part
(e.g., inner cylinder) that was previously installed on an MLG assembly
affected by the proposed AD would be subject to the AD requirements if
it is installed on a different unaffected MLG assembly.

We partially agree with the commenters' requests. We find that the
instructions in the service information for overhaul, as specified in
the NPRM, already address the commenters' concerns. However, we agree
that additional clarification would be helpful. We have revised
paragraph (l) of this AD to specify, in part, that an MLG may not be
installed unless that MLG has been overhauled as specified in the
applicable corrective actions of paragraphs (h) and (i) of this AD, or
using a method approved in accordance with the procedures specified in
paragraph (m) of this AD.
In addition, to address SunExpress's comment concerning component
installations, we provide the following clarification. Based on
accepted maintenance practices, a part number would include all of the
components that make up that part. It is incumbent upon the operator to
either inspect or do a records review to identify those parts affected
by this AD. Any parts identified, including all components of those
parts, are affected. As stated previously, we have revised paragraph
(l) of this AD to provide clarification.

Request To Extend Proposed Compliance Time

SunExpress requested that we revise the proposed compliance time
for the MLG inspections from 24 months to 36 months to accommodate its
maintenance schedule. SunExpress pointed out that the longer compliance
time would be financially beneficial for operators.
We do not agree with SunExpress's request to extend the compliance
time. The operator provided no technical justification for revising
this compliance time. Stress corrosion cracking of the external
surfaces of the MLG is a significant safety issue, and we have
determined that the proposed inspection threshold is warranted, based
on the effectiveness of the inspection procedure and the FAA transport
airplane risk assessment.
In developing an appropriate compliance time for this AD, we
considered the safety issues as well as the recommendations of the
manufacturer, the availability of necessary parts, and the practical
aspect of accomplishing the required inspection within an interval of
time that corresponds to the normal maintenance schedules of most
affected operators. We considered the manufacturer's recommendation as
well as the time necessary to complete the rulemaking process, and
found that a 24-month initial compliance time should fall well within
the time that the majority of operators have regular maintenance visits
scheduled. In light of these factors, we have determined that the 24-
month initial compliance time, as proposed, is appropriate. We have not
changed this AD in this regard.

Effect of Winglets on Accomplishment of the Proposed Actions

Aviation Partners Boeing stated that accomplishing Supplemental
Type Certificate (STC) ST00830SE does not affect the actions specified
in the NPRM.
We concur with the commenter. We have redesignated paragraph (c) of
the proposed AD as (c)(1) and added new paragraph (c)(2) to this AD to
state that installation of STC ST00830SE does not affect the ability to
accomplish the actions required by this final rule. Therefore, for
airplanes on which STC ST00830SE is installed, a ``change in product''
AMOC approval request is not necessary to comply with the requirements
of 14 CFR 39.17.

Conclusion

We reviewed the relevant data, considered the comments received,
and determined that air safety and the public interest require adopting
this AD with the changes described previously and minor editorial
changes. We have determined that these minor changes:
Are consistent with the intent that was proposed in the
NPRM for correcting the unsafe condition; and
Do not add any additional burden upon the public than was
already proposed in the NPRM.
We also determined that these changes will not increase the
economic burden on any operator or increase the scope of this AD.

Related Service Information Under 1 CFR Part 51

We reviewed Boeing Special Attention Service Bulletin 737-32-1486,
dated November 6, 2014, as revised by SASB 737-32-1486, R1. The service
information describes procedures for identifying affected parts,
repetitive external surface detailed inspections for damage of affected
parts, and related investigative and corrective actions if necessary.
For certain airplanes, the service information describes procedures for
a detailed inspection and bushing replacement of the trunnion bore, and
related investigative and corrective actions. The service information
also describes procedures for certain airplanes for a detailed
inspection of the trunnion bore, and corrective actions. 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.

Costs of Compliance

We estimate that this AD affects 33 airplanes of U.S. registry.
We estimate the following costs to comply with this AD:

Estimated Costs

Action Labor cost Parts cost Cost per product Cost on U.S. operators
External surface detailed inspection Up to 16 work-hours x $85 per hour = $1,360 per inspection cycle. $0 $1,360 per inspection cycle. Up to $44,880 per inspection cycle
Outer cylinder assembly trunnion bore detailed inspection and bushing replacement (Groups 1-2, configuration 1). 70 work-hours x $85 per hour = $5,950 Negligible $5,950 $196,350

We estimate the following costs to do any necessary replacements
that would be required based on the results of the inspections. We have
no way of determining the number of aircraft that might need this
replacement.

On-Condition Costs

Action Labor cost Cost per product
Outer cylinder assembly replacement (if required as a result of the outer cylinder assembly trunnion bore detailed inspection). 28 work-hours x $85 per hour = $2,380 $2,380

We have received no definitive data that would enable us to provide
cost estimates for certain on-condition actions (MLG external surface
repair, MLG component replacement, outer cylinder repair, and MLG
replacement) specified in this AD.
According to the manufacturer, some of the costs of this AD may be
covered under warranty, thereby reducing the cost impact on affected
individuals. We do not control warranty coverage for affected
individuals. As a result, we have included all costs in our cost
estimate.
The previous information is based on known affected airplanes.
However, the MLG may have been overhauled outside of the Boeing
Exchange Program as specified in the ``Clarification of Affected MLGs''
section of this AD.

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.
We are 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

This AD will not have federalism implications under Executive Order
13132. This AD will 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 that this AD:
(1) Is not a ``significant regulatory action'' under Executive
Order 12866,
(2) Is not a ``significant rule'' under DOT Regulatory Policies and
Procedures (44 FR 11034, February 26, 1979),
(3) Will not affect intrastate aviation in Alaska, and
(4) 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.

Adoption of the Amendment

Accordingly, under the authority delegated to me by the
Administrator, the FAA amends 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):