DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2019-0409; Product Identifier 2019-NM-092-AD; Amendment
39-19649; AD 2019-11-03]
RIN 2120-AA64

Airworthiness Directives; The Boeing Company Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule; request for comments.

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SUMMARY: The FAA is adopting an airworthiness directive (AD) for
certain The Boeing Company Model 737-700C, -800, and -900ER series
airplanes. This AD requires a maintenance records check to determine if
any main slat track assembly has been removed, an inspection of the
main slat track assemblies for a suspect lot number or a lot number
that cannot be determined, and applicable on-condition actions. This AD
was prompted by a report that certain main slat track assemblies were
manufactured incorrectly and are affected by hydrogen embrittlement.
The FAA is issuing this AD to address the unsafe condition on these
products.

DATES: This AD is effective June 10, 2019.
The Director of the Federal Register approved the incorporation by
reference of a certain publication listed in this AD as of June 10,
2019.
The FAA must receive comments on this AD by July 25, 2019.

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 AD, 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, 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-2019-0409.

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-2019-
0409; 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 final rule, the regulatory evaluation, any comments
received, and other information. The street address for Docket
Operations is listed above. Comments will be available in the AD docket
shortly after receipt.

FOR FURTHER INFORMATION CONTACT: Greg Rutar, Aerospace Engineer,
Airframe Section, FAA, Seattle ACO Branch, 2200 South 216th St., Des
Moines, WA 98198; phone and fax: 206-231-3529; email:
Greg.Rutar@faa.gov.

SUPPLEMENTARY INFORMATION:

Discussion

The FAA has received a report from Boeing indicating that 148 main
slat track assemblies from a set of lot numbers were manufactured
incorrectly and are affected by hydrogen embrittlement. Main slat track
assemblies that are affected by hydrogen embrittlement have reduced
strength. After reviewing information within the report provided from
Boeing, the FAA determined on May 22, 2019, that this condition, if not
addressed, could result in failure of main slat track assemblies, which
could cause the slat to depart and potentially strike the airplane,
resulting in injury to airplane occupants and/or preventing continued
safe flight and landing.

Other Relevant Potential Rulemaking

The FAA has determined that the identified unsafe condition also
exists on Boeing Model 737-8 and -9 (737 MAX) airplanes. Boeing is
currently developing service information that will address the unsafe
condition for these airplanes. Once this service information is
developed, approved, and available, the FAA might consider additional
rulemaking.

Related Service Information Under 1 CFR Part 51

The FAA reviewed Boeing Alert Requirements Bulletin 737-27A1312
RB, dated June 4, 2019. This service information describes procedures
for a maintenance records check to determine if any main slat track
assembly has been removed, an inspection of the main slat track
assemblies for a suspect lot number or a lot number that cannot be
determined, sending the inspection results to Boeing, and applicable
on-condition actions. On-condition actions include replacing main slat
track assemblies having a suspect lot number, or having a lot number
that cannot be determined, with serviceable main slat track assemblies;
shipping main slat track assemblies with suspect lot numbers or with
lot numbers that cannot be determined to Boeing; and contacting Boeing
to report if any main slat track assembly has been removed. 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

The FAA is issuing this AD because the agency 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.

AD Requirements

This AD requires accomplishment of the actions identified in Boeing
Alert Requirements Bulletin 737-27A1312 RB, dated June 4, 2019,
described previously, except for any differences identified as
exceptions in the regulatory text of this AD.
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-2019-0409.

FAA's Justification and Determination of the Effective Date

An unsafe condition exists that requires the immediate adoption of
this AD without providing an opportunity for public comments prior to
adoption. The FAA has found that the risk to the flying public
justifies waiving notice and comment prior to adoption of this rule
because main slat track assemblies that are affected by hydrogen
embrittlement have reduced strength. This condition, if not addressed,
could result in failure of main slat track assemblies, which could
cause the slat to depart and potentially strike the airplane, resulting
in injury to airplane occupants and/or preventing continued safe flight
and landing. The compliance time for the required action that has been
determined to adequately address the unsafe condition is shorter than
the time necessary for the public to comment and for publication of the
final rule. Therefore, the FAA finds good cause that notice and
opportunity for prior public comment are impracticable. In addition,
for the reasons stated above, the FAA finds that good cause exists for
making this amendment effective in less than 30 days.

Regulatory Flexibility Act (RFA)

The requirements of the RFA do not apply when an agency finds good
cause pursuant to 5 U.S.C. 553 to adopt a rule without prior notice and
comment. Because the FAA has determined that it has good cause to adopt
this rule without notice and comment, RFA analysis is not required.

Comments Invited

This AD is a final rule that involves requirements affecting flight
safety and was not preceded by notice and an opportunity for public
comment. However, the FAA invites you to send any written data, views,
or arguments about this final rule. Send your comments to an address
listed under the ADDRESSES section. Include the docket number FAA-2019-
0409 and Product Identifier 2019-NM-092-AD at the beginning of your
comments. The FAA specifically invites comments on the overall
regulatory, economic, environmental, and energy aspects of this final
rule. The FAA will consider all comments received by the closing date
and may amend this final rule because of those comments.
The FAA will post all comments the agency receives, without change,
to http://www.regulations.gov, including any personal information you
provide. The FAA will also post a report summarizing each substantive
verbal contact the agency receives about this final rule.

Costs of Compliance

The FAA estimates that this AD affects 32 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 based on the results of the
inspection. The FAA has no way of determining the number of aircraft
that might need these on-condition actions:

Estimated Costs of On-Condition Costs

According to the manufacturer, some or all of the costs of this AD
may be covered under warranty, thereby reducing the cost impact on
affected individuals. The FAA does not control warranty coverage for
affected individuals. As a result, the FAA has included all available
known costs in our cost estimate.

Paperwork Reduction Act

A federal agency may not conduct or sponsor, and a person is not
required to respond to, nor shall a person be subject to penalty for
failure to comply with a collection of information subject to the
requirements of the Paperwork Reduction Act unless that collection of
information displays a current valid OMB control number. The control
number for the collection of information required by this AD is 2120-
0056. The paperwork cost associated with this AD has been detailed in
the Costs of Compliance section of this document and includes time for
reviewing instructions, as well as completing and reviewing the
collection of information. Therefore, all reporting associated with
this AD is mandatory. Comments concerning the accuracy of this burden
and suggestions for reducing the burden should be directed to the FAA
at 800 Independence Ave. SW, Washington, DC 20591. ATTN: Information
Collection Clearance Officer, AES-200.

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, and
(2) Will not affect intrastate aviation in Alaska.

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):