DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2023-1413; Project Identifier AD-2023-00087-T;
Amendment 39-22706; AD 2024-06-01]
RIN 2120-AA64

Airworthiness Directives; The Boeing Company Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: The FAA is adopting a new airworthiness directive (AD) for
certain The Boeing Company Model 737-600, -700, -700C, -800, -900 and -
900ER airplanes. This AD was prompted by reports of cracks in the
forward galley door cutout forward upper corner bear strap. It has been
determined that the cracks were caused by high operating stresses in
the fuselage skin door cutout corner area due to stress concentration
at the door cutout. This AD requires an inspection of the fuselage skin
and the bear strap at the forward galley door cutout forward upper
corner for existing repairs, and applicable related investigative and
corrective actions. The FAA is issuing this AD to address the unsafe
condition on these products.

DATES: This AD is effective May 22, 2024.
The Director of the Federal Register approved the incorporation by
reference of a certain publication listed in this AD as of May 22,
2024.

ADDRESSES:
AD Docket: You may examine the AD docket at regulations.gov under
Docket No. FAA-2023-1413; 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 final rule, any comments received, and other
information. The address for Docket Operations is U.S. Department of
Transportation, Docket Operations, M-30, West Building Ground Floor,
Room W12-140, 1200 New Jersey Avenue SE, Washington, DC 20590.
Material Incorporated by Reference:
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; 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 under Docket No. FAA-2023-1413.

FOR FURTHER INFORMATION CONTACT: Owen 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:

Background

The FAA 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 airplanes.
The NPRM published in the Federal Register on July 24, 2023 (88 FR
47399). The NPRM was prompted by reports of cracks in the forward
galley door cutout forward upper corner bear strap. In the NPRM, the
FAA proposed to require an inspection of the fuselage skin and the bear
strap at the forward galley door cutout forward upper corner for
existing repairs, and applicable related investigative and corrective
actions. The FAA is issuing this AD to address cracks in the fuselage
skin and bear strap, which could increase in length until the fuselage
skin and bear strap severs. If not detected and corrected, a severed
fuselage skin and bear strap may lead to the inability of the principal
structural element (PSE) to sustain limit loads and may result in rapid
decompression of the fuselage and loss of structural integrity.

Discussion of Final Airworthiness Directive

Comments

The FAA received comments from seven commenters, including Boeing,
Aviation Partners Boeing, Delta Air Lines (Delta), Southwest Airlines
(Southwest), Sun Country Airlines (SCA), Sideral Linhas Aereas
(Sideral), and United Airlines (United). The following presents the
comments received on the NPRM and the FAA's response to each comment,

Effect of Winglets on Accomplishment of the Proposed Actions

Aviation Partners Boeing stated that the installation of winglets
per Supplemental Type Certificate (STC) ST00830SE does not affect the
actions specified in the proposed AD.
The FAA concurs with the commenter. The FAA has redesignated
paragraph (c) of the proposed AD as paragraph (c)(1) of this AD 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 Clarify Related Investigative Actions

Boeing requested that the FAA revise the Related Service
Information Under 1 CFR part 51 portion of the NPRM to specify that
related investigative actions include external and internal eddy
current inspections, as well as detailed inspections, as specified in
Boeing Alert Requirements Bulletin 737-53A1407 RB, dated December 20,
2022.
The FAA agrees for the reasons provided and has revised the Related
Service Information Under 1 CFR part 51 portion of this final rule
accordingly.

Request To Allow Later-Approved Versions of a Structural Repair Manual
(SRM)

Delta, Southwest, Sideral, and United requested that the proposed
AD be revised to allow later-approved revisions of 737NG SRM 53-10-01
Repair 6. United noted that existing repairs are evaluated against
737NG SRM 53-10-01 Repair 6, dated March 10, 2020, to determine
appropriate corrective actions. Delta claimed that, as written, only
737NG SRM 53-10-01 Repair 6, dated March 10, 2020, is an approved
previous repair in the service information. Southwest, Sideral, and
United all noted that the SRM may get updated and older copies of the
SRM are not made available to technicians, which may lead to confusion
and delays. United and Sideral added that repairs made using a future
version of the SRM may not match the current version, which would
require operators to obtain an AMOC.
The FAA agrees for the reasons provided. The FAA has added
paragraph (h)(3) of this AD to include later-approved revisions of
737NG SRM 53-10-01 Repair 6, dated March 10, 2020.

Request To Allow Applying a Certain Repair in Lieu of Obtaining
Instructions

Delta requested that the proposed AD be revised to allow applying
737NG SRM 53-10-01 Repair 6 and following the limitations of Table 3 of
Boeing Alert Requirements Bulletin 737-53A1407 RB, dated December 20,
2022, in lieu of contacting Boeing or the FAA for repair instructions
and doing that repair when an airplane is in Condition 2.1 or Condition
4.1, as specified in in Boeing Alert Requirements Bulletin 737-53A1407
RB, dated December 20, 2022. Delta stated that the service information
allows retaining 737NG SRM 53-10-01 Repair 6 if it is already applied
on an airplane and does not require removal of that repair. Delta added
that if an airplane is in an overnight or short visit, the option of
installing 737NG SRM 53-10-01 Repair 6 is faster and would only appear
to require additional inspections within 24,000 flight cycles.
The FAA disagrees with the commenter's request. Each crack
configuration found when accomplishing this AD will be unique and will
require an analysis to determine the appropriate repair and post-repair
inspection protocol. Boeing 737NG SRM 53-10-01 Repair 6 is designed for
a certain crack configuration, and therefore will not be applicable to
every crack that might be found when complying with this AD. However,
an operator may request an AMOC following the procedures in paragraph
(i) of this AD to use a different repair method.

Request for Creation of a Preventative Modification

SCA requested that a preventative modification be developed that
could terminate the repetitive inspections specified in Boeing Alert
Requirements Bulletin 737-53A1407 RB, dated December 20, 2022. SCA
added that the proposed AD affects all Boeing 737NG airplanes, but the
repair referenced in Boeing Alert Requirements Bulletin 737-53A1407 RB,
dated December 20, 2022, is only effective for a small portion of the
fleet.
The FAA disagrees with the commenter's request. After analyzing the
relevant data, the FAA has determined that the repetitive inspections
specified in the service information required by this AD are adequate
to address the unsafe condition. Additionally, the FAA infers that the
repair method the commenter referred to is 737NG SRM 53-10-01 Repair 6.
The FAA notes that the service information has conditions related to
whether or not a repair was accomplished using 737NG SRM 53-10-01
Repair 6, but requires operators to obtain and follow instructions for
new crack findings, which is a method applicable to all airplanes.

Request To Combine Actions With Another AD

SCA requested that the inspections in the proposed AD be combined
with the inspections in AD 2021-02-13, Amendment 39-21396 (86 FR 10776,
February 23, 2021) (AD 2021-02-13). The commenter stated that the
proposed AD's inspection area is in immediate proximity of the
inspection area required by AD 2021-02-13, and corrective actions for a
finding in either inspection area will affect the inspection
requirements for both the proposed AD and AD 2021-02-13. SCA claimed
this would require obtaining two AMOCs for a single finding, adding
undue complexity. The commenter also noted that, while both the
proposed AD and AD 2021-02-13 require contacting the manufacturer,
there is a strong potential for oversight regarding compliance with the
proposed AD or AD 2021-02-13. SCA stated that, at a minimum, AD 2021-
02-13 should be listed as an affected AD in paragraph (b) of the
proposed AD, since an external reinforcing repair would affect the
inspection of both the proposed AD and AD 2021-02-13.
The FAA disagrees with the commenter's request. Although the two
ADs require actions in areas that are in close proximity (AD 2021-02-13
requires inspections for cracks of the fuselage skin and bear strap at
the forward galley door between certain stations, and applicable on-
condition actions), they require different actions to address different
unsafe conditions. Therefore, combining the two ADs would not be
practical. Additionally, only ADs that are superseded or terminated by
another AD are considered ``affected'' ADs. Finally, if an operator
needs to request a repair that affects both this AD and AD 2021-02-13,
they may request a single AMOC.

Conclusion

The FAA reviewed the relevant data, considered any comments
received, and determined that air safety requires adopting this AD as
proposed. Accordingly, the FAA is issuing this AD to address the unsafe
condition on these products. Except for minor editorial changes, and
any other changes described previously, this AD is adopted as proposed
in the NPRM. None of the changes will increase the economic burden on
any operator.

Related Service Information Under 1 CFR Part 51

The FAA reviewed Boeing Alert Requirements Bulletin 737-53A1407 RB,
dated December 20, 2022. This service information specifies procedures
for an external general visual inspection of the fuselage skin at the
forward galley door cutout forward upper corner for any repair, and
applicable related investigative and corrective actions. Related
investigative actions include detailed inspections for cracking of the
fuselage skin and bear strap; and internal and external high frequency
eddy current (HFEC) and low frequency eddy current (LFEC) inspections
for cracking of the fuselage skin, bear strap, and repair parts.
Corrective actions include obtaining and following instructions for
crack repair. 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 ADDRESSES.

Costs of Compliance

The FAA estimates that this AD affects 1,938 airplanes of U.S.
registry. The FAA estimates the following costs to comply with this AD:

Estimated costs

The FAA has received no definitive data on which to base the cost
estimates for the on-condition repairs or for the alternative
inspections specified in this 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

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) Will not affect intrastate aviation in Alaska, and
(3) 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 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: