DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2018-0408; Product Identifier 2017-NM-146-AD]
RIN 2120-AA64

Airworthiness Directives; The Boeing Company Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: We propose to supersede Airworthiness Directive (AD) 2016-13-
16, which applies to all The Boeing Company Model 737-600, -700, -700C,
-800, -900, and -900ER series airplanes. AD 2016-13-16 requires an
inspection or records check to determine if affected horizontal
stabilizers are installed, related investigative actions, and, for
affected horizontal stabilizers, repetitive inspections for any crack
of the horizontal stabilizer rear spar upper chord, and corrective
action if necessary. Since we issued AD 2016-13-16, we have determined
that clarification of inspection areas and serial number information of
the horizontal stabilizer is necessary. Therefore, this proposed AD
would retain the requirements of AD 2016-13-16, with revised service
information that clarifies the inspection areas and serial number
information of the horizontal stabilizer. We are proposing this AD to
address the unsafe condition on these products.

DATES: We must receive comments on this proposed AD by June 29, 2018.

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

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

Fax: 202-493-2251.

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

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

For service information identified in this NPRM, contact Boeing
Commercial Airplanes, Attention: Contractual & Data Services (C&DS),
2600 Westminster Blvd., MC 110-SK57, Seal Beach, CA 90740-5600;
telephone 562-797-1717; internet https://www.myboeingfleet.com. You may
view this service information at the FAA, 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-2018-0408.

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-2018-0408;
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 NPRM, the regulatory evaluation, any comments received,
and other information. The street address for the Docket Office (phone:
800-647-5527) is in the ADDRESSES section. Comments will be available
in the AD docket shortly after receipt.

FOR FURTHER INFORMATION CONTACT: Lu Lu, Aerospace Engineer, Airframe
Section, FAA, Seattle ACO Branch, 2200 South 216th St., Des Moines, WA
98198; phone and fax: 206-231-3525; email: lu.lu@faa.gov.

SUPPLEMENTARY INFORMATION:

Comments Invited

We invite you to send any written relevant data, views, or
arguments about this proposal. Send your comments to an address listed
under the ADDRESSES section. Include "Docket No. FAA-2018-0408;
Product Identifier 2017-NM-146-AD" at the beginning of your comments.
We specifically invite comments on the overall regulatory, economic,
environmental, and energy aspects of this NPRM. We will consider all
comments received by the closing date and may amend this NPRM because
of those comments.

We will post all comments we receive, without change, to http://www.
regulations.gov, including any personal information you provide. We
will also post a report summarizing each substantive verbal contact we
receive about this proposed AD.

Discussion

We issued AD 2016-13-16, Amendment 39-18581 (81 FR 44503, July 8,
2016) ("AD 2016-13-16"), for all The Boeing Company Model 737-600,
-700, -700C, -800, -900, and -900ER series airplanes. AD 2016-13-16
requires an identification plate inspection or records check to
determine if affected horizontal stabilizers are installed, related
investigative actions, and for affected horizontal stabilizers,
repetitive inspections for any crack of the horizontal stabilizer rear
spar upper chord, and corrective action if necessary. AD 2016-13-16
resulted from reports of a manufacturing oversight, in which a supplier
omitted the required protective finish on certain bushings installed in
the rear spar upper chord on horizontal stabilizers, which could lead
to galvanic corrosion and consequent cracking of the rear spar upper
chord. We issued AD 2016-13-16 to address cracking of the rear spar
upper chord, which can result in the failure of the upper chord,
consequent departure of the horizontal stabilizer from the airplane,
and loss of control of the airplane.

Actions Since AD 2016-13-16 Was Issued

Since we issued AD 2016-13-16, it has been determined that
clarification of inspection areas and serial number information of the
horizontal stabilizer is necessary. Therefore, the service information
has been revised to clarify the inspection areas for cracking and
serial number information of the horizontal stabilizer.

Related Service Information Under 1 CFR Part 51

We reviewed Boeing Alert Service Bulletin 737-55A1097, Revision 1,
dated September 20, 2017. This service information describes procedures
for an identification plate inspection or records check to determine
whether affected horizontal stabilizers are installed, related
investigative actions, and for affected horizontal stabilizers,
repetitive high frequency eddy current (HFEC) inspections for any crack
of the horizontal stabilizer rear spar upper chord, and corrective
action. This service information is reasonably available because the
interested parties have access to it through their normal course of
business or by the means identified in the ADDRESSES section.

FAA's Determination

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

Proposed AD Requirements

Although this proposed AD does not explicitly restate the
requirements of AD 2016-13-16, this proposed AD would retain all
requirements of AD 2016-13-16. Those requirements are referenced in the
service information identified previously, which, in turn, is
referenced in paragraph (g) of this proposed AD. This proposed AD would
clarify the inspection areas and serial number information of the
horizontal stabilizer. This proposed AD would also require
accomplishment of the actions identified as "RC" (required for
compliance) in the Accomplishment Instructions of Boeing Alert Service
Bulletin 737-55A1097, Revision 1, dated September 20, 2017, described
previously.

For information on the procedures and compliance times, see this
service information at http://www.regulations.gov by searching for and
locating Docket No. FAA-2018-0408.

Costs of Compliance

We estimate that this proposed AD affects 1,748 airplanes of U.S.
registry. We estimate the following costs to comply with this proposed
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 proposed
AD.

According to the manufacturer, all of the costs of this proposed 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 proposed 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

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

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

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

(2) Is not a "significant rule" under the 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.

The Proposed Amendment

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

PART 39--AIRWORTHINESS DIRECTIVES

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

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

Sec. 39.13 [Amended]

2. The FAA amends Sec. 39.13 by removing Airworthiness Directive (AD)
2016-13-16, Amendment 39-18581 (81 FR 44503, July 8, 2016), and adding
the following new AD: