DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2016-9112; Product Identifier 2016-NM-091-AD; Amendment
39-18982; AD 2017-16-05]
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) for certain
The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER
series airplanes. This AD was prompted by a report of a Krueger flap
bullnose departing an airplane during taxi, which caused damage to the
wing structure and thrust reverser. This AD requires a one-time
detailed visual inspection for discrepancies in the Krueger flap
bullnose attachment hardware, 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 September 22, 2017.
The Director of the Federal Register approved the incorporation by
reference of a certain publication listed in this AD as of September
22, 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 Standards Staff, 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-2016-9112.

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-
9112; 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 Section, FAA, Seattle Aircraft Certification Office (ACO)
Branch, 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 certain The Boeing Company
Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes.
The NPRM published in the Federal Register on September 29, 2016 (81 FR
66874) (``the NPRM''). The NPRM was prompted by a report of a Krueger
flap bullnose departing an airplane during taxi, which caused damage to
the wing structure and thrust reverser. The NPRM proposed to require a one-time
detailed visual inspection for discrepancies in the Krueger flap
bullnose attachment hardware, and related investigative and corrective
actions, if necessary. We are issuing this AD to detect and correct
missing Krueger flap bullnose hardware. Such missing hardware could
result in the Krueger flap bullnose departing the airplane during
flight, which could damage empennage structure and lead to the
inability to maintain continued safe flight and landing.

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

Vincent Romano, a private citizen, and United Airlines (UAL),
stated their support for the NPRM.

Effect of Winglets on Accomplishment of the Proposed Actions

Aviation Partners Boeing stated that accomplishing the 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 NPRM as paragraph (c)(1) 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 Reference the Latest Service Information

All Nippon Airways (ANA), American Airlines (AAL), Boeing,
Jet2.com, TUIfly GmbH (HAP), UAL, and Kennedy Juma, requested revising
the NPRM to reference Boeing Alert Service Bulletin 737-57A1327,
Revision 1, dated September 28, 2016. Some commenters pointed out that
the original issue had some errors in the illustrations and needed
certain clarifications. ANA and Boeing also requested that we provide
credit for accomplishing the original issue of the service information.
We agree that this final rule should reference the latest service
information. Since we issued the NPRM, Boeing issued Boeing Alert
Service Bulletin 737-57A1327, Revision 1, dated September 28, 2016. We
have revised paragraphs (c)(1) (paragraph (c) of the proposed AD) and
(g) of this AD to reference Boeing Alert Service Bulletin 737-57A1327,
Revision 1, dated September 28, 2016, for accomplishment of the
required actions. We have also revised this AD to provide credit for
using Boeing Alert Service Bulletin 737-57A1327, dated May 20, 2016, to
accomplish the required actions before the effective date of this AD.

Request To Correct the Latest Service Information

AAL requested that Boeing Alert Service Bulletin 737-57A1327,
Revision 1, dated September 28, 2016, be corrected to address errors in
Figures 1, 2, 3, and 4. AAL stated that these errors affect the
depiction of how the clevis assembly, clevis, and bullnose hinge lug
are attached to each other, and suggested that revising the figures to
correct the errors would clarify which parts must be subject to the
detailed inspection.
We acknowledge that Figures 1, 2, 3, and 4 of Boeing Alert Service
Bulletin 737-57A1327, Revision 1, dated September 28, 2016, contain
errors in the labeling of parts in the illustrations. However, the
instructions in the tables in the figures correctly identify the parts
and actions to be accomplished. Since the instructions are correct, the
service bulletin adequately addresses the unsafe condition. We do not
revise manufacturers' service information. However, Boeing might decide
to revise Boeing Alert Service Bulletin 737-57A1327, Revision 1, dated
September 28, 2016, to correct the errors. We have not changed the AD
in this regard.

Request To Allow Alternate Replacement Procedure

AAL and Southwest Airlines (SWA) requested that we revise the NPRM
to provide an option to replace cracked or deformed bullnose hinge lugs
or clevis assemblies with bullnose hinge lugs or clevis assemblies
instead of replacement with a Krueger flap assembly, as specified in
paragraph 3.B.2.a.(1)(a)1) of Boeing Alert Service Bulletin 737-
57A1327, Revision 1, dated September 28, 2016. AAL suggested that the
replacement option could be done using certain sections of a component
maintenance manual (CMM). SWA suggested the use of Boeing production
installation drawings. Both AAL and SWA also stated that replacing only
the affected bullnose hinge lugs or clevis assemblies would also reduce
the cost of repair or replacement. SWA also stated that there is a
limited inventory of Krueger flap assemblies and that limited
inventory, combined with a 6-month compliance time could significantly
impair operators.
We understand that the suggested replacement option might reduce
the burden on operators. However, we do not agree to revise this AD to
include the suggested changes. The repairs provided by the suggested
sections of the CMM address normal wear-and-tear, and these repairs may
not be appropriate for addressing damage that might result from an
improperly attached Krueger flap. Boeing informed us that there is no
procedure in the CMM that would provide step-by-step instructions to
remove only the bullnose other than by use of the drawing system.
Engineering instructions would be needed to ensure that the remainder
of the flap assembly is serviceable and not damaged in addition to the
damaged bullnose hinge lugs or clevis assembly, and that level of
instruction would be too much detail for an AD. However, once we issue
this AD, any person may request approval of an AMOC under the
provisions of paragraph (i) of this AD. We have not changed the AD 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 AD.

Related Service Information Under 1 CFR Part 51

We reviewed Boeing Alert Service Bulletin 737-57A1327, Revision 1,
dated September 28, 2016. The service information describes procedures
for a one-time detailed visual inspection for discrepancies in the
Krueger flap bullnose attachment hardware, and related investigative
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 1,495 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 available 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):