DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2023-1886; Project Identifier AD-2023-00429-T]
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: The FAA proposes to supersede Airworthiness Directive (AD)
2009-01-02, which applies to certain Boeing Model 737-600, -700, -700C,
-800, and -900 series airplanes. AD 2009-01-02 requires an inspection
of frames between body station (BS) 360 and BS 907 to determine if
certain support brackets of the air conditioning (A/C) outlet
extrusions are installed, inspections for cracking of the frames around
the attachment holes of the subject brackets, and repair if necessary.
AD 2009-01-02 also requires installing new, improved fittings for all
support brackets of the A/C outlet extrusions between BS 360 and BS
907. Since the FAA issued AD 2009-01-02, the agency determined that
certain repairs might develop fatigue cracks that could result in the
inability of the frame to sustain limit load and therefore must be
inspected. This proposed AD would continue to require the actions
specified in AD 2009-01-02 and would also require repetitive
inspections for cracking of certain repairs and repair if necessary.
The FAA is proposing this AD to address the unsafe condition on these
products.

DATES: The FAA must receive comments on this proposed AD by November 9,
2023.

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 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.
AD Docket: You may examine the AD docket at regulations.gov under
Docket No. FAA-2023-1886; 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, any comments received, and other
information. The street address for Docket Operations is listed above.
Material Incorporated by Reference:
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; website myboeingfleet.com.
You may view this service information at the FAA,
Airworthiness Products Section, Operational Safety 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 at
regulations.gov by searching for and locating Docket No. FAA-2023-1886.

FOR FURTHER INFORMATION CONTACT: Owen F. Bley-Male, Aviation Safety
Engineer, FAA, 2200 South 216th St., Des Moines, WA 98198; phone: 206-
231-3992; email: Owen.F.Bley-Male@faa.gov.

SUPPLEMENTARY INFORMATION:

Comments Invited

The FAA invites you to send any written relevant data, views, or
arguments about this proposal. Send your comments to an address listed
under ADDRESSES. Include ``Docket No. FAA-2023-1886; Project Identifier
AD-2023-00429-T'' at the beginning of your comments. The most helpful
comments reference a specific portion of the proposal, explain the
reason for any recommended change, and include supporting data. The FAA
will consider all comments received by the closing date and may amend
the proposal because of those comments.
Except for Confidential Business Information (CBI) as described in
the following paragraph, and other
information as described in 14 CFR 11.35, the FAA will post all
comments received, without change, to regulations.gov, including any
personal information you provide. The agency will also post a report
summarizing each substantive verbal contact received about this
proposed AD.

Confidential Business Information

CBI is commercial or financial information that is both customarily
and actually treated as private by its owner. Under the Freedom of
Information Act (FOIA) (5 U.S.C. 552), CBI is exempt from public
disclosure. If your comments responsive to this NPRM contain commercial
or financial information that is customarily treated as private, that
you actually treat as private, and that is relevant or responsive to
this NPRM, it is important that you clearly designate the submitted
comments as CBI. Please mark each page of your submission containing
CBI as ``PROPIN.'' The FAA will treat such marked submissions as
confidential under the FOIA, and they will not be placed in the public
docket of this NPRM. Submissions containing CBI should be sent to Owen
F. Bley-Male, Aviation Safety Engineer, FAA, 2200 South 216th St., Des
Moines, WA 98198; phone: 206-231-3992; email: Owen.F.Bley-Male@faa.gov.
Any commentary that the FAA receives that is not specifically
designated as CBI will be placed in the public docket for this
rulemaking.

Background

The FAA issued AD 2009-01-02, Amendment 39-15780 (74 FR 4117,
January 23, 2009) (AD 2009-01-02), for certain Boeing Model 737-600, -
700, -700C, -800, and -900 series airplanes. AD 2009-01-02 was prompted
by numerous reports of multiple cracks in the frame around the
attachment holes of the support bracket of the A/C outlet extrusion. AD
2009-01-02 requires a one-time general visual inspection of frames
between BS 360 and BS 907 to determine if certain support brackets of
the A/C outlet extrusions are installed, medium- and high-frequency
eddy current inspections for cracking of the frames around the
attachment holes of the subject brackets, and repair if necessary. AD
2009-01-02 also requires installing new, improved fittings for all
support brackets of the A/C outlet extrusions between BS 360 and BS
907. AD 2009-01-02 refers to Boeing Special Attention Service Bulletin
737-25-1544, Revision 1, dated January 16, 2008, as the appropriate
source of service information for accomplishing the required actions.
The agency issued AD 2009-01-02 to prevent frame cracking, which, if
not corrected, could lead to a severed frame that, combined with
cracking of the skin lap splice above stringer 10, could result in
rapid decompression of the airplane.

Actions Since AD 2009-01-02 Was Issued

Since the FAA issued AD 2009-01-02, Boeing issued Special Attention
Service Bulletin 737-25A1544, Revision 3, dated May 16, 2016, as an
alternative method of compliance for AD 2009-01-02, which includes an
alternative to making repairs using Boeing Special Attention Service
Bulletin 737-25-1544, Revision 1, dated January 16, 2008. The FAA and
Boeing determined that the repairs done using Boeing Special Attention
Service Bulletin 737-25A1544, Revision 3, dated May 16, 2016, might
develop fatigue cracks that could result in the inability of the frame
to sustain limit load. Boeing subsequently issued Alert Service
Bulletin 737-25A1544, Revision 4, dated February 15, 2022, which added
damage tolerance inspections for certain BS 907 repairs done using
Boeing Special Attention Service Bulletin 737-25A1544, Revision 3,
dated May 16, 2016. The FAA determined that those post-repair
inspections are necessary to address the unsafe condition.

FAA's Determination

The FAA is issuing this NPRM after determining that the unsafe
condition described previously is likely to exist or develop on other
products of the same type design.

Related Service Information Under 1 CFR Part 51

The FAA reviewed Boeing Alert Service Bulletin 737-25A1544,
Revision 4, dated February 15, 2022. This service information specifies
procedures for a one-time general visual inspection of frames between
BS 360 and BS 907 to determine if certain support brackets of the A/C
outlet extrusions are installed; low-, medium- and high-frequency eddy
current inspections for cracking of the frames around the attachment
holes of the subject brackets, and repair if necessary; and
installation of new, improved fittings for all support brackets of the
A/C outlet extrusions between BS 360 and BS 907. This service
information also specifies procedures for repetitive detailed and high-
frequency eddy current inspections for cracking of certain repairs at
BS 907 and repair if necessary.
This AD also requires Boeing Special Attention Service Bulletin
737-25-1544, Revision 1, dated January 16, 2008, which the Director of
the Federal Register approved for incorporation by reference as of
February 27, 2009 (74 FR 4117, January 23, 2009).
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.

Proposed AD Requirements in This NPRM

This proposed AD would require accomplishing the actions specified
in the service information described previously, except for any
differences identified as exceptions in the regulatory text of this
proposed AD. For information on the procedures and compliance times,
see this service information at regulations.gov by searching for and
locating Docket No. FAA-2023-1886.

Costs of Compliance

The FAA estimates that this AD, if adopted as proposed, would
affect 738 airplanes of U.S. registry. The FAA estimates the following
costs to comply with this proposed AD:

Estimated Costs

The FAA has received no definitive data on which to base the cost
estimates for the on-condition repairs that would be required based on
the results of the inspections specified in this proposed AD.

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.

Regulatory Findings

The FAA has 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) Would not affect intrastate aviation in Alaska, and
(3) Would 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:

a. Removing Airworthiness Directive (AD) 2009-01-02, Amendment 39-15780
(74 FR 4117, January 23, 2009), and

b. Adding the following new AD: