DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2016-7270; Product Identifier 2015-NM-116-AD; Amendment
39-19025; AD 2017-18-16]
RIN 2120-AA64

Airworthiness Directives; The Boeing Company Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: We are adopting a new airworthiness directive (AD) for certain
The Boeing Company Model 737-700 and -700C series airplanes. This AD
was prompted by a report that, for certain airplanes, the nose-up pitch
trim limit and associated warning will allow the horizontal stabilizer
position to be set outside acceptable limits for a mis-trimmed takeoff
condition. This AD requires, depending on airplane configuration,
replacing certain pitch trim light plates, relocating certain position
warning horn switches, revising certain software, removing a certain
placard, and doing 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 October 16, 2017.
The Director of the Federal Register approved the incorporation by
reference of certain publications listed in this AD as of October 16,
2017.

ADDRESSES: For Aviation Partners Boeing service information identified
in this final rule, contact Aviation Partners Boeing, 2811 South 102nd
Street, Suite 200, Seattle, WA 98168; phone: 206-830-7699; fax: 206-
767-3355; email: leng@aviationpartners.com; Internet: http://www.aviationpartnersboeing.com.
For Boeing 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 Standards Branch, 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-2016-7270.

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-
7270; 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: Fnu Winarto, Aerospace Engineer,
Systems and Equipment Section, FAA, Seattle ACO Branch, 1601 Lind
Avenue SW., Renton, WA 98057-3356; phone: 425-917-6659; fax: 425-917-
6590; email: fnu.winarto@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 certain The Boeing Company
Model 737-700 and -700C series airplanes. The NPRM published in the
Federal Register on June 28, 2016 (81 FR 41894). The NPRM was prompted
by a report that, for airplanes with blended winglets, the nose-up
pitch trim limit and associated warning for the horizontal stabilizer
control system will allow the stabilizer position to be set outside
acceptable limits for a mis-trimmed takeoff condition. The NPRM
proposed to require, depending on airplane configuration, replacing the
pitch trim light plates on the flight deck control stand, relocating
the position warning horn switches of the horizontal stabilizer,
revising the software, removing the placard, and doing related
investigative and corrective actions if necessary. We are issuing this
AD to prevent a stabilizer position set outside acceptable limits for a
mis-trimmed takeoff condition. Settings outside of the appropriate
pitch trim limits could result in loss of controllability of the
airplane during takeoff.

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.

Support for the NPRM

Air Line Pilots Association, International (ALPA) stated its
support for the NPRM. United Airlines stated that it has no technical
objections with the NPRM.

Request To Use the Latest Service Information

Aviation Partners Boeing requested that the NPRM be updated to
include the latest service information, which is Aviation Partners
Boeing Service Bulletin AP737-27-002, Revision 3, dated July 19, 2016.
We agree with the commenter's request. Since the NPRM was issued,
we have reviewed Aviation Partners Boeing Service Bulletin AP737-27-
002, Revision 4, dated April 24, 2017, which provides minor changes. We
have updated this AD to refer to Aviation Partners Boeing Service
Bulletin AP737-27-002, Revision 4, dated April 24, 2017. We have also
added credit for Aviation Partners Boeing Service Bulletin AP737-27-
002, Revision 3, dated July 19, 2016.

Request To Revise Boeing Service Information

Southwest Airlines (SWA) requested that Boeing Alert Service
Bulletin 737-27A1306, dated September 10, 2015, be revised to reference
revised Aviation Partners Boeing service information. SWA stated that
Boeing Alert Service Bulletin 737-27A1306, dated September 10, 2015,
specifies concurrent accomplishment of Aviation Partners Boeing Service
Bulletin AP737-27-002, March 31, 2015. SWA stated that this concurrent
requirement should call for the use of Aviation Partners Boeing Service
Bulletin AP737-27-002, Revision 2, dated March 1, 2016, as stated
throughout the NPRM.
We acknowledge the commenter's request. After we issued the NPRM,
Boeing published Boeing Alert Service Bulletin 737-27A1306, Revision 1,
dated December 14, 2016, which identifies Aviation Partners Boeing
Service Bulletins ``AP737-27-002, Original Issue, Revision 1, Revision
2, or Revision 3,'' as concurrent requirements. Aviation Partners
Boeing has since published Aviation Partners Boeing Service Bulletin
AP737-27-002, Revision 4, dated April 24, 2017. We have revised
paragraph (g)(2) of this AD to refer to Boeing Alert Service Bulletin
737-27A1306, dated September 10, 2015, as revised by Boeing Alert
Service Bulletin 737-27A1306, Revision 1, dated December 14, 2016. As
we stated previously, Aviation Partners Boeing has published Aviation
Partners Boeing Service Bulletin AP737-27-002, Revision 4, dated April
24, 2017. Paragraphs (g)(1) and (g)(2) of this AD also refer to
Aviation Partners Boeing Service Bulletin AP737-27-002, Revision 4,
dated April 24, 2017.

Request To Make Service Information Available or Revise the
Applicability

Delta Air Lines (DAL) requested that we either make Aviation
Partners Boeing Service Bulletin AP737-34-005, dated July 17, 2015,
available to all operators or revise paragraph (c)(3) of the
applicability in the proposed AD to identify specifically affected
airplanes. DAL stated that, during its review of the NPRM, it was not
able to obtain a copy of Aviation Partners Boeing Service Bulletin
AP737-34-005, dated July 17, 2015. DAL commented that it requested
Aviation Partners Boeing Service Bulletin AP737-34-005, dated July 17,
2015, from Boeing and was advised that the Aviation Partners Boeing
service information was not applicable to DAL airplanes, and,
therefore, the service information would not be made available to DAL.
DAL stated that, as a result, it was unable to independently verify
that there are no DAL airplanes identified in Aviation Partners Boeing
Service Bulletin AP737-34-005, dated July 17, 2015. DAL commented that
paragraph 1.A.1., ``Aircraft Affected,'' of Aviation Partners Boeing
Service Bulletin AP737-27-002, Revision 2, dated March 1, 2016, does
identify airplanes having line numbers 384 and 3128 as affected by
Aviation Partners Boeing Service Bulletin AP737-34-005, dated July 17,
2015. DAL stated that, however, paragraph (c)(3) of the proposed AD
does not mention Aviation Partners Boeing Service Bulletin AP737-27-
002, Revision 2, dated March 1, 2016, as a method to identify
airplanes.
DAL commented that it would prefer that Aviation Partners Boeing
Service Bulletin AP737-34-005, dated July 17, 2015, be available to all
operators so that each operator can determine whether or not their
airplanes are affected. DAL also stated that if the manufacturer cannot
support this, DAL suggested that paragraph (c)(3) in the AD should
indicate that Aviation Partners Boeing Service Bulletin AP737-34-005,
dated July 17, 2015, is only applicable to airplanes having line
numbers 384 and 3128.
We partially agree with the commenter's request. We disagree with
revising the applicability of this AD. However, the service information
specified in paragraphs (c), (g), and (h) of this AD is incorporated by
reference in this AD, and it should be available to all operators, as
well as the general public, after the AD is published. We have provided
availability information for the required service information in both
the preamble and regulatory text of this AD.
We have also clarified the actions for the airplane having line
number 3128. Boeing Alert Service Bulletin 737-27A1306, dated September
10, 2015, as specified in paragraph (c)(2) of this AD, also references
line number 3128. Paragraph (g)(2) of this AD refers to Boeing Alert
Service Bulletin 737-27A1306, dated September 10, 2015, for
accomplishing actions. Paragraph (h) of this AD refers to Aviation
Partners Boeing Service Bulletin AP737-34-005, dated July 17, 2015, for
accomplishing actions. For line number 3128, the actions in paragraph
(h) of this AD should be done instead of paragraph (g)(2) of this AD.
We have revised paragraph (g)(2) of this AD to exclude line number
3128.
In addition, we have clarified the actions for airplanes identified
in paragraph (c)(2) of this AD by excluding those airplanes from
paragraph (g)(1) of this AD. Paragraph (g)(1) of this AD specifies
actions for airplanes identified in paragraph (c)(1) of this AD, which
includes airplanes that are identified in paragraph (c)(2) of this AD.
However, for airplanes identified in paragraph (c)(2) of this AD, the
actions specified in paragraph (g)(2) of this AD must be done.

Request To Exclude Certain Airplanes From the Applicability

SWA requested that any airplane modified per Supplemental Type
Certificate (STC) ST00830SE, Amendment dated April 21, 2015, dated
August 26, 2015, or subsequent be excluded from the applicability of
the proposed AD. SWA stated that it has recently incorporated STC
ST00830SE (Amendment dated April 21, 2015) on airplanes that have not
previously had blended winglets installed. SWA commented that the
Amendment dated April 21, 2015, of the STC incorporates the intent of
Aviation Partners Boeing Service Bulletin AP737-27-002. SWA stated that
it is currently incorporating STC ST00830SE, Amendment dated August 26,
2015, on airplanes that have not previously had blended winglets
installed.
We partially agree with the commenter's request. We concur with the
assertion that installation of STC ST00830SE at Amendment dated April
21, 2015, fulfills the equivalent actions specified in Aviation
Partners Boeing Service Bulletin AP737-27-002, Revision 4, dated April
24, 2017. In addition, there are later amendments that apply to Model 737-700
series airplanes that fulfill the actions specified in Aviation Partners
Boeing Service Bulletin AP737-27-002, Revision 4, dated April 24, 2017.
We have revised paragraph (c) of this AD to exclude airplanes on which
winglets are installed as specified in STC ST00830SE, Amendment dated
on or after April 21, 2015.

Request To Include Certain Line Numbers in the Applicability

SWA requested that we include certain line numbers in the
applicability of the proposed AD. SWA stated that paragraph 1.A.1.,
``Aircraft Affected,'' of Aviation Partners Boeing Service Bulletin
AP737-27-002 defines the effectivity of Group 2 airplanes as ``. . .
manufacturing line number 3100 and on . . . .'' SWA commented that it
is unclear if this modification is being incorporated on the Boeing
production line. SWA stated that, if this modification is being
incorporated on the Boeing production line, then the manufacturing line
number should be identified as the upper end of the effectivity of
Aviation Partners Boeing Service Bulletin AP737-27-002 and in the upper
end of the proposed applicability.
We agree that operators need to know which airplanes are affected.
However, we disagree with including line numbers in the applicability
of this AD, because the Aviation Partners Boeing kit configuration
identified in section 1.A.1., ``Aircraft Affected,'' of Aviation
Partners Boeing Service Bulletin AP737-27-002 clearly identifies the
airplanes that need the modification. Airplanes delivered from Boeing
with other kit configuration numbers are outside the effectivity, and
therefore, do not require the accomplishment of Aviation Partners
Boeing Service Bulletin AP737-27-002. We have not changed this AD in
this regard.

Request To Revise the Description of the Unsafe Condition

Boeing requested that we revise the unsafe condition statement
throughout the NPRM, so that it is more consistent with the description
specified in the service information. Boeing clarified that
accomplishing the proposed requirements will not prevent takeoffs with
incorrect trim settings, but rather allows for acceptable takeoff
limits at specific airplane configurations in which the stabilizer trim
has been set at a maximum mis-trim, as specified in 14 CFR part 25.
We agree to revise the unsafe condition statement as suggested by
Boeing for the reason provided. We have revised this final rule
accordingly.

Request To Revise the Proposed Compliance Time

ALPA requested that we reduce the proposed compliance time from
``72 months after the effective date of this AD'' to ``36 months after
the effective date of this AD.'' ALPA commented that it is of the
upmost importance to ensure the airplane is taking off in the correct
trim setting and the associated warning system has to work properly in
order to alert the flight crew of a possible misconfiguration before
takeoff.
We do not agree to reduce the compliance time for the requirements
of this AD. We agree that it is important to have the correct
configuration of the airplane for takeoff, because of the potential
unsafe conditions that incorrect configurations might pose. However,
this AD does not address that safety concern. After considering the
available information, we have determined that the compliance time, as
proposed, represents an appropriate interval of time in which the
required actions can be performed in a timely manner within the
affected fleet, while still maintaining an adequate level of safety. In
developing an appropriate compliance time, we considered the safety
implications, parts availability, and normal maintenance schedules for
timely accomplishment of the modifications. Further, we arrived at the
proposed compliance time with the manufacturer's concurrence. To reduce
the proposed compliance time would necessitate (under the provisions of
the Administrative Procedure Act) reissuing the notice, reopening the
period for public comment, considering additional comments subsequently
received, and eventually issuing a final rule. In light of this, and in
consideration of the amount of time that has already elapsed since
issuance of the original notice, we have determined that further delay
of this final rule is not appropriate. However, if additional data are
presented that would justify a shorter compliance time, we may consider
further rulemaking on this issue. We have not changed this AD in this
regard.

Request To Clarify Certain Acceptable Operator-Supplied Parts

DAL requested that we clarify the NPRM to specify whether certain
alternative lockwire part numbers (P/Ns) are acceptable alternatives to
those specified in Aviation Partners Boeing Service Bulletin AP737-27-
002. DAL stated that table 3 of Aviation Partners Boeing Service
Bulletin AP737-27-002 calls for the use of lockwire having P/N
MS20995NC20 and P/N MS20995NC32. DAL stated that review of parts
available on MyBoeingFleet Part Page shows that those part numbers are
no longer available. DAL commented that the Part Page provides
substitute P/Ns M000200850 and P/N M000320850, respectively. DAL stated
that Aviation Partners Boeing Service Bulletin AP737-27-002 includes a
note in the Accomplishment Instructions, which refers operators to
chapter 51 of the Boeing 737 Structural Repair Manual (SRM) for use of
approved fastener and process material substitutions. DAL commented
that this SRM reference does not detail any substitutes for the
lockwire. DAL stated that, lacking an approval source other than the
Boeing Part Page, an alternative method of compliance (AMOC) would be
required to use lockwire having P/N M000200850 and P/N M000320850. DAL
commented that specifying these would facilitate operator procurement
efforts and minimize potential AMOC requests.
We agree to clarify. Part Number M000200850 and P/N M000320850 are
the Boeing stock numbers, which meet the MS20995 lockwire
specifications in Aviation Partners Boeing Service Bulletin AP737-27-
002. In addition, specific lockwire part numbers are not included in
the Required for Compliance (RC) steps of Aviation Partners Boeing
Service Bulletin AP737-27-002. Therefore, we find that it is not
necessary to revise this AD to address this issue, and we have not
changed this AD in this regard.

Request To Clarify Recordkeeping Requirements

DAL requested that we exclude the explicit instruction in Note 3 of
the Accomplishment Instructions of Aviation Partners Boeing Service
Bulletin AP737-27-002, Revision 2, dated March 1, 2016, that specifies
making a recordkeeping entry in the airplane records once the service
information is completed. DAL requested that, if the exclusion of Note
3 cannot be granted in the AD, the final rule provide an allowance for
operators to use their existing recordkeeping procedures to record
completion of Aviation Partners Boeing Service Bulletin AP737-27-002,
Revision 2, dated March 1, 2016.
DAL commented that its recordkeeping process would track compliance
with a specific engineering document number used to embody a specified
service bulletin on the airplane. DAL stated that it would not
typically record service bulletin accomplishment using a phrase similar
to that given in Note 3 of the Accomplishment Instructions of Aviation
Partners Boeing Service Bulletin AP737-27-002, Revision 2, dated March
1, 2016. DAL commented that the requirement to show compliance with the
subject service information does not require such explicit
requirements. DAL stated that recording the service information exactly
as detailed in the note does not improve airplane safety, and
therefore, latitude should be given to operators regarding their method
for recording compliance with Aviation Partners Boeing Service Bulletin
AP737-27-002, Revision 2, dated March 1, 2016. DAL stated that this
will prevent the need for future AMOC requests.
We agree that operators may use their existing recordkeeping
processes to document maintenance actions performed using Aviation
Partners Boeing Service Bulletin AP737-27-002. For this AD,
recordkeeping is not a critical step that addresses the unsafe
condition. As DAL pointed out, the actions specified in Note 3 are not
called out in an RC step in the Accomplishment Instructions. We have
added paragraph (j)(2) to this AD to clarify that recordkeeping is not
required by this AD.

Request To Clarify the Requirements for the Onboard Performance Tool
(OPT)

DAL requested that we clarify the requirements for incorporating
the OPT. DAL stated that Aviation Partners Boeing Service Bulletin
AP737-27-002 specifies concurrent actions recommending that users of
the OPT contact Boeing for an updated database and instructions on how
to incorporate this database into the OPT. DAL commented that it does
not use the OPT and that the proposed AD does not give any guidance
with respect to this concurrent requirement. DAL commented that the
concurrent requirement is actually written as a recommendation, which
would imply that it is not a mandatory action and that compliance is
optional.
We agree to provide clarification regarding the OPT. We infer that
DAL meant to refer to Aviation Partners Boeing Service Bulletin AP737-
34-005, as there are no concurrent actions specified in Aviation
Partners Boeing Service Bulletin AP737-27-002. The usage of the OPT, as
specified in the concurrent requirements section of Aviation Partners
Boeing Service Bulletin AP737-34-005, dated July 17, 2015, is optional
and is not a requirement of this AD. We have not changed this AD in
this regard.

Request To Use Later-Approved Software Versions

SWA requested that the proposed AD allow for the installation of
later-approved versions of the Flight Management Computer (FMC) Model
Engine Database (MEDB) and/or FMC Operational Program Software (OPS).
SWA stated that Part 4 of Aviation Partners Boeing Service Bulletin
AP737-27-002, Revision 2, dated March 1, 2016, specifies the
installation of FMC MEDB software having P/N BCG-01T-A0 with compatible
FMC OPS Versions U10.8A, U11, or U12. SWA commented that if any later
versions of FMC MEDB or FMC OPS are installed at a future date an AMOC
would be needed to stay in compliance with the AD.
We disagree with the commenter's request. This AD requires, for
certain airplanes, the actions specified in Aviation Partners Boeing
Service Bulletin AP737-27-002, Revision 4, dated April 24, 2017, which
identifies specific software that must be installed. That software must
be installed to address the identified unsafe condition. However, under
the provisions of paragraph (k) of this AD, we will consider requests
for approval of new software if sufficient data are submitted to
substantiate that the new software would provide an acceptable level of
safety. We have not changed the final rule in this regard.

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 final
rule.

Related Service Information Under 1 CFR Part 51

We reviewed the following Aviation Partners Boeing service
information.
Aviation Partners Boeing Service Bulletin AP737-27-002,
Revision 4, dated April 24, 2017. This service information describes
procedures for replacing the pitch trim light plates on the flight deck
control stand, relocating the horizontal stabilizer position warning
horn switches, and updating the software for the MEDB of the FMC.
Aviation Partners Boeing Service Bulletin AP737-34-005,
dated July 17, 2015. This service information describes procedures for
updating the software in the MEDB for the FMC and removing a certain
placard on the control stand.
We also reviewed the following Boeing service information.
Boeing Alert Service Bulletin 737-27A1306, dated September
10, 2015. This service information describes procedures for replacing
the pitch trim light plates on the flight deck control stand,
relocating the position warning horn switches of the horizontal
stabilizer, and installing new software for the MEDB for the FMC.
Boeing Alert Service Bulletin 737-27A1306, Revision 1,
dated December 14, 2016. This service information is a short form
revision that specifies changes to the concurrent requirements and the
affected publications identified in Boeing Alert Service Bulletin 737-
27A1306, dated September 10, 2015.
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 569 airplanes of U.S. registry.
We estimate the following costs to comply with this AD:

Estimated Costs

We have received no definitive data that would enable us to provide
cost estimates for the on-condition actions 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.

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.
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 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) 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):