DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2018-0409; Product Identifier 2017-NM-120-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) 2017-16-
05, which applies to certain The Boeing Company Model 737-600, -700, -
700C, -800, -900, and -900ER series airplanes. AD 2017-16-05 requires a
one-time detailed visual inspection for discrepancies in the Krueger
flap bullnose attachment hardware, and related investigative and
corrective actions if necessary. Since we issued AD 2017-16-05, we
received a report of a missing no. 2 Krueger flap bullnose hinge bolt
from an airplane that was not included in the applicability of AD 2017-
16-05. This proposed AD would add airplanes and an additional
inspection to determine if any Krueger flap no. 1, 2, 3, or 4 has been
replaced, and related investigative and corrective actions. Since this
is a rotable parts issue, the applicability of this AD has been
expanded beyond the airplanes listed in the related service bulletin to
include all airplanes on which a Krueger flap bullnose may be
installed. 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-2018-0409.

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-2018-0409;
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 NPRM, the regulatory evaluation, any comments received, and other
information. The street address for Docket Operations (phone: 800-647-
5527) is in the ADDRESSES section. Comments will be available in the AD
docket shortly after receipt.

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:

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-2018-0409;
Product Identifier 2017-NM-120-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 2017-16-05, Amendment 39-18982 (82 FR 39344, August
18, 2017) ("AD 2017-16-05"), for certain The Boeing Company Model
737-600, -700, -700C, -800, -900, and -900ER series airplanes. AD 2017-
16-05 requires a one-time detailed visual inspection for discrepancies
in the Krueger flap bullnose attachment hardware, and related
investigative and corrective actions, if necessary. AD 2017-16-05
resulted from a report of a Krueger flap bullnose departing an airplane
during taxi, which caused damage to the wing structure and thrust
reverser. We issued AD 2017-16-05 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.

Actions Since AD 2017-16-05 Was Issued

Since we issued AD 2017-16-05, we have received a report of a
missing no. 2 Krueger flap bullnose hinge bolt from an airplane that
was not included in the applicability of AD 2017-16-05.

Related Service Information Under 1 CFR Part 51

We reviewed Boeing Alert Service Bulletin 737-57A1327, Revision 2,
dated July 25, 2017 ("BASB 737-57A1327, R2"). This 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; and an
inspection to determine if any Krueger flap no. 1, 2, 3, or 4 has been
replaced, 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.

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 2017-16-05, this proposed AD would retain certain
requirements of AD 2017-16-05. 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
add airplanes and an additional inspection to determine if any Krueger
flap no. 1, 2, 3, or 4 has been replaced, and applicable related
investigative and corrective actions. This proposed AD would also
require accomplishment of the actions identified as "RC" (required
for compliance) in the Accomplishment Instructions of BASB 737-57A1327,
R2, described previously, except as discussed under "Differences
Between this Proposed AD and the Service Information."

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-2018-0409.

Differences Between This Proposed AD and the Service Information

Because the affected parts identified in this NPRM are rotable
parts, we have determined that these parts could later be installed on
airplanes that were initially delivered with acceptable parts, thereby
subjecting those airplanes to the unsafe condition. Therefore, while
the effectivity of BASB 737-57A1327, R2 is limited to line numbers 1
through 6465 inclusive, the applicability of this proposed AD includes
all The Boeing Company Model 737-600, -700, -700C, -800, -900, and -
900ER series airplanes. This difference has been coordinated with
Boeing.

Costs of Compliance

We estimate that this proposed AD affects 1,814 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, some 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 and associated appliances 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)
2017-16-05, Amendment 39-18982 (82 FR 39344, August 18, 2017), and
adding the following new AD: