DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2018-0708; Product Identifier 2018-NM-072-AD; Amendment
39-19652; AD 2019-11-06]
RIN 2120-AA64

Airworthiness Directives; The Boeing Company Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: The FAA is adopting a new airworthiness directive (AD) for
certain The Boeing Company Model 737-600, -700, -700C, -800, -900, and
-900ER series airplanes. This AD was prompted by reports of cracks in
the skin and a certain chord at three fastener locations common to the
drag link assembly at the chord. This AD requires repetitive
inspections of the skin under the drag link assembly for any cracks,
and applicable on-condition actions. The FAA is issuing this AD to
address the unsafe condition on these products.

DATES: This AD is effective July 17, 2019.
The Director of the Federal Register approved the incorporation by
reference of a certain publication listed in this AD as of July 17,
2019.

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 service information at the FAA, Transport Standards Branch,
2200 South 216th St., Des Moines, WA.
For information on the availability of this material at the FAA, call
206-231-3195. It is also available on the internet at http://www.regulations.gov
by searching for and locating Docket No. FAA-2018-0708.

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-2018-0708;
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 final rule, the regulatory evaluation, any comments received, and
other information. The address for Docket Operations is 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 Section, FAA, Seattle ACO Branch, 2200 South 216th St., Des
Moines, WA 98198; phone and fax: 206-231-3527; email:
alan.pohl@faa.gov.

SUPPLEMENTARY INFORMATION:

Discussion

The FAA issued a notice of proposed rulemaking (NPRM) to amend 14
CFR part 39 by adding an AD that would apply to certain The Boeing
Company Model 737-600, -700, -700C, -800, -900, and -900ER series
airplanes. The NPRM published in the Federal Register on August 14,
2018 (83 FR 40159). The NPRM was prompted by reports of cracks in the
skin and a certain chord at three fastener locations common to the drag
link assembly at the chord. The NPRM proposed to require repetitive
inspections of the skin under the drag link assembly for any cracks,
and applicable on-condition actions.

Comments

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

Support for the NPRM

American Airlines stated its support for the NPRM. United Airlines
stated that it has no technical objections to the NPRM.

Effect of Winglets on Accomplishment of the Proposed Actions

Aviation Partners Boeing (APB) stated that accomplishing the
Supplemental Type Certificate (STC) ST00830SE does not affect the
ability to accomplish the actions specified in the proposed AD.
The FAA concurs with the commenter. The FAA has redesignated
paragraph (c) of the proposed AD as paragraph (c)(1) of this AD and
added 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 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.

Request To Revise Applicability

Southwest Airlines (SWA) requested that paragraph (c) of the
proposed AD be revised to include aircraft with APB STC ST00830SE
installed, with either blended or split scimitar winglets. SWA noted
that paragraph 1.F of Boeing Alert Service Bulletin 737-53A1368, dated
February 27, 2018, addresses the approval statement that the service
information is also approved for airplanes having FAA APB STC ST00830SE
installed, not including any areas affected by the split scimitar
winglet configuration. SWA pointed out that it operates aircraft with
STC ST00830SE installed and it has determined the structure within the
STC ST00830SE area is subject to the concern addressed by the service
information.
The FAA acknowledges the commenter's request. APB has already
stated that winglets installed per STC ST00830SE do not affect the
ability to accomplish the actions required by this AD. In addition,
after the NPRM comment period closed, the FAA contacted APB as a result
of SWA's comment and received additional confirmation that STC
ST00830SE does not affect the ability to accomplish the actions of this
AD. APB stated, ``NPRM Docket FAA-2018-0708 was reviewed by APB for all
configurations of STC ST00830SE, blended and split scimitar [winglets].
The APB comment of no impact is applicable to all configurations of STC
ST00830SE.'' As stated above, the FAA has added 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 AD.

Request To Address Errors in the Service Information

Alaska Airlines (ASA), Delta Airlines (DAL), SWA, and Skymark
Airlines (SMA) pointed out multiple errors in Boeing Alert Service
Bulletin 737-53A1368, dated February 27, 2018. DAL noted two errors in
the service information that they would like to see addressed in order
to avoid non-compliance with the proposed AD and reduce confusion. ASA
echoed DAL's request to avoid non-compliance with the proposed AD by
correcting the service information and pointed out one error within the
service information, in addition to the ones noted by other commenters.
SWA noted six errors within the service information and requested
paragraph (h) of this proposed AD be revised to add exceptions to the
service information. For one error, SWA noted that the post-repair
instructions of the service information specify inspection standards
that differ from established non-destructive test standards, and SWA
requested paragraph (h) of this proposed AD be revised to include a
provision allowing a deviation from the service information. SMA stated
they have found errors in their initial review of the service
information, which Boeing has acknowledged.
SMA requested to delay the issuance of the final rule until a
revision to Boeing Alert Service Bulletin 737-53A1368 is released and
can be incorporated into the final rule. SMA argued that they are
obligated to prepare a work instruction document that corrects any
errors in the service information and this method is not preferable to
SMA for managing the accomplishment of the proposed AD.
The FAA acknowledges the commenters' concerns regarding the
information in the service information that requires clarification or
correction. In light of the critical nature of the identified unsafe
condition, the FAA does not consider it appropriate to delay this final
rule until new service information is available. In addition, the
amount of clarification needed would be overly complex for inclusion in
this AD. Therefore, the FAA has added paragraph (h)(3) to this AD,
``Exceptions to Service Information Specifications,'' to provide
operators with information regarding how to address any actions in the
service information that cannot be accomplished. The FAA has also
revised paragraph (g) of this AD to include a reference to paragraph
(h)(3) of this AD.
We anticipate that Boeing will publish a revision to Boeing Alert
Service Bulletin 737-53A1368, dated February 27, 2018, to address known
errors. The FAA will consider issuing a global AMOC to address known
errors if the new revision is not published soon after the effective
date of this AD. After the publication of the revision, the FAA will
review the revision in consideration of an AMOC to this AD, or may
consider future rulemaking action.
Regarding SWA's comment on post-repair and post-modification
inspections, those inspections will not be required by this AD, as
discussed in the response to the request below to exclude post-repair
and post-modification inspections.

Request To Exclude Post-Repair and Post-Modification Inspections

Boeing and SWA requested that the proposed AD be revised to exclude
the post-repair/post-modification inspection requirements specified in
Boeing Alert Service Bulletin 737-53A1368, dated February 27, 2018, as
AD-mandated actions. The commenters pointed to paragraph (j) of AD
2017-02-10, Amendment 39-18789 (82 FR 10258, February 10, 2017) (``AD
2017-02-10'') as an example of post-repair and post-modification
inspections that are specified in the service information but are
excepted by the AD.
Note that the service information referenced in AD 2017-02-10
identified post-repair and post-modification inspection procedures, but
the AD excepted those inspections because the inspections are
airworthiness limitations and are required by maintenance and
operational rules. Therefore, it was unnecessary to mandate them in AD
2017-02-10.
The FAA agrees with the commenters' requests for the reasons
provided. The FAA infers that SWA meant to include in its comment a
reference to Table 5 of paragraph 1.E, Compliance, of Boeing Alert
Service Bulletin 737-53A1368, dated February 27, 2018. This table is
associated with the Part 8 post-repair inspections of the
Accomplishment Instructions. The FAA has added paragraph (h)(4) to
exclude the post-repair and post-modification inspection requirements
specified in Parts 8, 9, 10, and 11 of the Accomplishment Instructions
of Boeing Alert Service Bulletin 737-53A1368, dated February 27, 2018,
as AD-mandated actions. The FAA has also revised paragraph (g) of this
AD to include a reference to paragraph (h)(4) of this AD.
In addition, Parts 8, 9, 10, and 11 of the Accomplishment
Instructions of Boeing Alert Service Bulletin 737-53A1368, dated
February 27, 2018, were incorrectly labeled as required for compliance
(RC). This will likely be corrected in a future revision to this
service bulletin.

Request To Include Optional Terminating Action

SWA requested to add a paragraph that specifies an AMOC for the
requirements of paragraph (g) of AD 2013-19-23, Amendment 39-17605 (78
FR 61173, October 3, 2013) (``AD 2013-19-23''). SWA pointed out that
the accomplishment of Part 4 or Part 5 of the Accomplishment
Instructions of Boeing Alert Service Bulletin 737-53A1368, dated
February 27, 2018, will prohibit the D626A001-9-01 inspection for
Principal Structural Element (PSE) 53-30-02-4, as required by paragraph
(g) of AD 2013-19-23.
The FAA partially agrees with the commenter's request. After the
NPRM comment period closed, the FAA queried Boeing and confirmed that
this repair should indeed be considered a method of compliance, as
suggested by SWA. The FAA has added paragraph (j) to this AD to allow
an optional terminating action for the inspections of PSE 53-30-02-4
required by the airworthiness limitations specified in paragraph (g) of
AD 2013-19-23. The optional terminating action is the accomplishment of
the actions specified in Part 4 or Part 5 of the Accomplishment
Instructions of Boeing Alert Service Bulletin 737-53A1368, dated
February 27, 2018. The FAA has also revised paragraph (b) of this AD to
reflect that this AD affects AD 2013-19-23.

Request To Add Inspection Condition of "No Crack Found''

ASA noted that Tables 1, 2, and 3 of paragraph 1.E., ``Compliance''
of Boeing Alert Service Bulletin 737-53A1368, dated February 27, 2018,
are missing Condition 1.3, which should provide instructions on how to
proceed in the case that no crack is found during the specified
inspection. ASA suggested using the same language found in Condition
2.3 of Tables 1, 2, and 3 of paragraph 1.E., ``Compliance'' of Boeing
Alert Service Bulletin 737-53A1368, dated February 27, 2018. ASA
reasoned that it requires clear and correct reference documents to
develop accurate engineering documents and avoid noncompliance with the
requirements of the AD.
The FAA agrees with the commenter's request for the reasons
provided. There should also be a Condition 1.3 in the appropriate places in the
Accomplishment Instructions as well as paragraph 1.E., Compliance.
These issues have been coordinated with Boeing, and they have indicated
that this will be addressed in a future revision to Boeing Alert
Service Bulletin 737-53A1368, dated February 27, 2018. The FAA has
added paragraph (h)(5) to this AD to provide instructions regarding how
to proceed if no crack is found upon accomplishment of Part 3 of the
Accomplishment Instructions of Boeing Alert Service Bulletin 737-
53A1368, dated February 27, 2018. The FAA has also revised paragraph
(g) of this AD to include a reference to paragraph (h)(5) of this AD.

Request To Approve AMOCs for AD 2017-02-10

ASA requested to revise the proposed AD to include AMOCs previously
approved for AD 2017-02-10. ASA pointed out that during their
accomplishment of AD 2017-02-10, they completed repairs in the same
area as specified in Boeing Alert Service Bulletin 737-53A1368, dated
February 27, 2018.
The FAA does not agree with the request to allow AMOCs previously
approved for AD 2017-02-10 to be approved for this AD. After the NPRM
comment period closed, the FAA coordinated this issue with Boeing.
Boeing indicated that different types of repairs have been encountered
during the service history of Boeing Special Attention Service Bulletin
737-53-1294, Revision 2, dated December 9, 2015, which is referred to
as the appropriate source of service information for accomplishing the
required actions specified in AD 2017-02-10. For some repairs required
by this AD, an AMOC approved for AD 2017-02-10 would also be suitable
for this AD. However, this is not the case for all types of repairs,
and therefore, all AMOCs previously approved for AD 2017-02-10 cannot
be approved for this AD. This AD has not been changed in this regard.

Request To Add Material Incorporated by Reference Paragraph

Boeing requested to add a paragraph to the proposed AD titled
``Material Incorporated by Reference,'' stating that this paragraph is
missing.
For clarification, the paragraph titled ``Material Incorporated by
Reference'' is not currently included in NPRMs, but is included in all
final rule ADs.

Conclusion

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

Related Service Information Under 1 CFR Part 51

The FAA reviewed Boeing Alert Service Bulletin 737-53A1368, dated
February 27, 2018. This service information describes procedures for an
ultrasonic inspection of the skin under the drag link assembly and
repair for any cracks; repetitive inspections for any cracks, including
ultrasonic inspections, high frequency eddy current (HFEC) inspections,
low frequency eddy current (LFEC) inspections, and detailed
inspections; and a preventive modification if no crack is found. 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

The FAA estimates that this AD affects 1,664 airplanes of U.S.
registry. The FAA estimates the following costs to comply with this AD:

Estimated Costs for Required Actions

The FAA estimates the following costs to do any necessary on-
condition actions that would be required. The FAA has no way of
determining the number of aircraft that might need these on-condition
actions:

Estimated Costs of On-Condition Actions

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.
This AD is issued in accordance with authority delegated by the
Executive Director, Aircraft Certification Service, as authorized by
FAA Order 8000.51C. In accordance with that order, issuance
of ADs is normally a function of the Compliance and Airworthiness
Division, but during this transition period, the Executive Director has
delegated the authority to issue ADs applicable to transport category
airplanes and associated appliances to the Director of the System
Oversight Division.

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) 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.

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):