Airworthiness Directives; The Boeing Company Airplanes

[Federal Register Volume 90, Number 137 (Monday, July 21, 2025)]
[Rules and Regulations]
[Pages 34171-34173]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2025-13595]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2024-1880; Project Identifier AD-2023-01149-T; 
Amendment 39-23088; AD 2025-15-01]
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 all 
The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER 
series airplanes. This AD was prompted by a report of a frame web crack 
at a certain fuselage station (STA) between certain stringers common to 
the frame web notch. This AD requires repetitive inspections for cracks 
of the frames and repair of cracks. The FAA is issuing this AD to 
address the unsafe condition on these products.

DATES: This AD is effective August 25, 2025.
    The Director of the Federal Register approved the incorporation by 
reference of a certain publication listed in this AD as of August 25, 
2025.

ADDRESSES: 
    AD Docket: You may examine the AD docket at regulations.gov under 
Docket No. FAA-2024-1880; 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:
    <bullet> For Boeing material 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; website myboeingfleet.com.
    <bullet> You may view this material 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-2024-1880.

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

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 all The Boeing Company 
Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. 
The NPRM published in the Federal Register on July 2, 2024 (89 FR 
54737). The NPRM was prompted by a report of a frame web crack at 
fuselage STA 328 between stringers S-20R and S-21R on a Model 737-700 
airplane. The crack was common to the frame web notch and was 
approximately 0.85 inch long. In the NPRM, the FAA proposed to require 
repetitive detailed and high frequency eddy current (HFEC) inspections 
for cracks of the frames and repair of any cracks. The FAA is issuing 
this AD to address undetected cracks in the frame, which could lead to 
the inability of the principal structural element to sustain limit 
loads and result in the subsequent loss of structural integrity of the 
airplane.

Discussion of Final Airworthiness Directive

Comments

    The FAA received a comment from United Airlines, which supported 
the NPRM without change.
    The FAA also received comments from Aviation Partners Boeing, The 
Boeing Company (Boeing), Southwest Airlines (Southwest), and Sudan 
Civil Aviation Authority (Sudan CAA). 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 installing winglets under 
Supplemental Type Certificate (STC) ST00830SE does not affect 
accomplishment of the actions specified in the proposed AD.
    The FAA agrees. 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 Revise Stringer Range

    Boeing requested the FAA clarify the preamble with respect to the 
stringer range for each affected frame. Boeing noted that the 
Background section of the NPRM identifies the affected area as ``STA 
312, STA 328, and STA 344 from stringers S-20R to S-23R.'' Boeing 
requested that the text specify the stringer range for each frame and 
be changed to ``STA 312 (Stringers S-20R to S-23R), STA 328 (Stringers 
S-19R to S-22R), and STA 344 (Stringers S-20R to S-23R).''
    The FAA agrees that the requested change would clarify the affected 
area. However, as this information from the NPRM is not restated in 
this final rule, no change is necessary as a result of this comment.

Requests Regarding Frame Replacement

    Southwest requested the FAA change the proposed AD to allow 
replacement of a cracked frame with a new frame as an option instead of 
repairing the frame. Southwest further requested that, for frames 
replaced with a new frame, the FAA allow the compliance time to start 
from the date of the new frame installation. Southwest stated that this 
adjusted threshold is similar to the principle structural element 
replacement guidance in the FAA-approved airworthiness limitations for 
the affected model airplanes.
    The FAA acknowledges that removal and replacement with type design 
parts is possible but does not agree to include this option in 
paragraph (h)(2) of this AD or adjust the compliance time for allowing 
this replacement as a repair without complete substantiating data. 
Replacement might involve oversizing holes, replacing more than just 
the frame, or other actions that would

[[Page 34172]]

impact the appropriate compliance time, including requiring shorter 
inspection intervals. Each replacement would involve unique 
circumstances, so the FAA cannot determine whether allowing the 
compliance time to start from the date of the new frame installation 
would provide an adequate level of safety. Therefore, the FAA has not 
changed the AD in this regard. The FAA will, however, consider AMOCs in 
accordance with paragraph (i) of this AD for alternative repair actions 
or compliance time changes, provided substantiation data is submitted 
to show that an acceptable level of safety is maintained using the 
alternative actions and compliance times.

Request To Expand Inspection Areas

    Sudan CAA requested that the inspection areas for each station be 
expanded beyond the stringers specified in Boeing Alert Requirements 
Bulletin 737-53A1410 RB, dated October 11, 2023. Sudan CAA stated that 
typical cracks in the frame start at the blanket pin hole, the fastener 
in the inner chord, or the frame web notch, and cracking could occur at 
adjacent areas that are not covered by the service information. Sudan 
CAA therefore concluded that the proposed AD may not address the unsafe 
condition.
    The FAA disagrees with this request. The inspection area is 
determined for each frame by the design and loading of the frame, which 
are similar, but not identical, across the three frames. This AD was 
prompted by a frame web crack at fuselage STA 328 between stringers S-
20R and S-21R. Because the load transfer is similar in adjacent areas, 
the frames at STA 312, STA 328, and STA 344 from stringers S-20R to S-
23R are also subject to the unsafe condition. Based on the fleet data 
the FAA has received, the FAA determined that the actions specified in 
the referenced service information adequately address the unsafe 
condition. Therefore, the FAA has not changed this AD as a result of 
this comment. If new information becomes available, the FAA might 
consider further rulemaking.

Request To Revise Applicability

    Boeing requested that the FAA revise the applicability to only 
include line numbers 1 through 9273. Boeing stated that line numbers 
9274 and subsequent will have a new design change in notch radius 
(0.25'' changed from 0.16'') that will mitigate the safety issue. 
Boeing further stated it will revise its service information to reflect 
this change in effectivity.
    The FAA does not agree to reduce the applicability of this AD. 
Boeing is still in the process of having the design change approved. In 
addition, once approved, the FAA will need to determine whether the 
design change adequately addresses the unsafe condition. Should the FAA 
determine the design change provides an acceptable level of safety to 
address the unsafe condition, operators may request approval of the 
design change as an AMOC using the procedures in paragraph (i) of this 
AD.

Request To Correct Typographical Error

    Sudan CAA requested a revision to note (b) of Figure 1 in Boeing 
Alert Requirements Bulletin 737-53A1410 RB, dated October 11, 2023, 
which refers to a certain structural detail that ``is inspected.'' 
Sudan CAA requested replacing ``is inspected'' with ``is to be 
inspected'' for clarification.
    The FAA does not find the requested change necessary. The FAA 
reviewed the requirements bulletin and determined that it provides 
sufficient clarity.

Conclusion

    The FAA reviewed the relevant data, considered the 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.

Material Incorporated by Reference Under 1 CFR Part 51

    The FAA reviewed Boeing Alert Requirements Bulletin 737-53A1410 RB, 
dated October 11, 2023. This material specifies procedures for 
repetitive detailed inspections of the forward and aft sides of the 
frames, and surface and open hole HFEC inspections of the frames, at 
STA 312 from S-20R to S-23R, STA 328 from S-19R to S-22R, and STA 344 
from S-20R to S-23R for cracks. This material also specifies repairing 
any crack found. This material 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.

Costs of Compliance

    The FAA estimates that this AD affects 1,583 airplanes of U.S. 
registry. The FAA estimates the following costs to comply with this AD:

                                                 Estimated Costs
----------------------------------------------------------------------------------------------------------------
                                                                                                 Cost on U.S.
              Action                    Labor cost        Parts cost      Cost per product        operators
----------------------------------------------------------------------------------------------------------------
Inspections......................  9 work-hours x $85               $0  $765 per inspection  $1,210,995 per
                                    per hour = $765                      cycle.               inspection cycle.
                                    per inspection
                                    cycle.
----------------------------------------------------------------------------------------------------------------

Estimated Costs of On-Condition Actions

    The extent of damage/cracking found during the required inspections 
could vary significantly from airplane to airplane. The FAA has no way 
of determining the type of repair or cost to repair any cracks on each 
airplane or the number of airplanes that may require repair.

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.

[[Page 34173]]

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

0
1. The authority citation for part 39 continues to read as follows:

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


Sec.  39.13  [Amended]

0
2. The FAA amends Sec.  39.13 by adding the following new airworthiness 
directive:

2025-15-01 The Boeing Company: Amendment 39-23088; Docket No. FAA-
2024-1880; Project Identifier AD-2023-01149-T.

(a) Effective Date

    This airworthiness directive (AD) is effective August 25, 2025.

(b) Affected ADs

    None.

(c) Applicability

    (1) This AD applies to all The Boeing Company Model 737-600, -
700, -700C, -800, -900, and -900ER series airplanes, certificated in 
any category.
    (2) Installation of Supplemental Type Certificate (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.

(d) Subject

    Air Transport Association (ATA) of America Code 53, Fuselage.

(e) Unsafe Condition

    This AD was prompted by a report of a frame web crack at 
fuselage station 328 between stringers S-20R and S-21R common to the 
frame web notch. The FAA is issuing this AD to address undetected 
cracks in the frame. The unsafe condition, if not addressed, could 
lead to the inability of the principal structural element to sustain 
limit loads, which could result in the subsequent loss of structural 
integrity of the airplane.

(f) Compliance

    Comply with this AD within the compliance times specified, 
unless already done.

(g) Required Actions

    Except as specified by paragraph (h) of this AD: At the 
applicable times specified in the ``Compliance'' paragraph of Boeing 
Alert Requirements Bulletin 737-53A1410 RB, dated October 11, 2023, 
do all applicable actions identified in, and in accordance with, the 
Accomplishment Instructions of Boeing Alert Requirements Bulletin 
737-53A1410 RB, dated October 11, 2023.

    Note 1 to paragraph (g):  Guidance for accomplishing the actions 
required by this AD can be found in Boeing Alert Service Bulletin 
737-53A1410, dated October 11, 2023, which is referred to in Boeing 
Alert Requirements Bulletin 737-53A1410 RB, dated October 11, 2023.

(h) Exceptions to Requirements Bulletin Specifications

    (1) Where the ``Boeing Recommended Compliance Time'' column in 
the table under the ``Compliance'' paragraph of Boeing Alert 
Requirements Bulletin 737-53A1410 RB, dated October 11, 2023, refers 
to ``the Original Issue date of Requirements Bulletin 737-53A1410 
RB,'' this AD requires using the effective date of this AD.
    (2) Where Boeing Alert Requirements Bulletin 737-53A1410 RB, 
dated October 11, 2023, specifies contacting Boeing for repair 
instructions, this AD requires doing the repair using a method 
approved in accordance with the procedures in paragraph (i) of this 
AD.

(i) Alternative Methods of Compliance (AMOCs)

    (1) The Manager, AIR-520, Continued Operational Safety Branch, 
FAA, has the authority to approve AMOCs for this AD, if requested 
using the procedures found in 14 CFR 39.19. In accordance with 14 
CFR 39.19, send your request to your principal inspector or 
responsible Flight Standards Office, as appropriate. If sending 
information directly to the manager of the certification office, 
send it to the attention of the person identified in paragraph 
(j)(1) of this AD. Information may be emailed to: [email protected].
    (2) Before using any approved AMOC, notify your appropriate 
principal inspector, or lacking a principal inspector, the manager 
of the responsible Flight Standards Office.
    (3) An AMOC that provides an acceptable level of safety may be 
used for any repair, modification, or alteration required by this AD 
if it is approved by The Boeing Company Organization Designation 
Authorization (ODA) that has been authorized by the Manager, AIR-
520, Continued Operational Safety Branch, FAA, to make those 
findings. To be approved, the repair method, modification deviation, 
or alteration deviation must meet the certification basis of the 
airplane, and the approval must specifically refer to this AD.

(j) Related Information

    (1) For more information about this AD, contact Owen Bley-Male, 
Aviation Safety Engineer, FAA, 2200 South 216th St., Des Moines, WA 
98198; phone: 206-231-3992; email: [email protected].
    (2) Material identified in this AD that is not incorporated by 
reference is available at the address specified in paragraph (k)(3) 
this AD.

(k) Material Incorporated by Reference

    (1) The Director of the Federal Register approved the 
incorporation by reference of the material listed in this paragraph 
under 5 U.S.C. 552(a) and 1 CFR part 51.
    (2) You must use this material as applicable to do the actions 
required by this AD, unless the AD specifies otherwise.
    (i) Boeing Alert Requirements Bulletin 737-53A1410 RB, dated 
October 11, 2023.
    (ii) [Reserved]
    (3) For the material 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; website myboeingfleet.com.
    (4) You may view this material 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.
    (5) You may view this material at the National Archives and 
Records Administration (NARA). For information on the availability 
of this material at NARA, visit www.archives.gov/federal-register/cfr/ibr-locations or email [email protected].

    Issued on July 16, 2025.
Peter A. White,
Deputy Director, Integrated Certificate Management Division, Aircraft 
Certification Service.
[FR Doc. 2025-13595 Filed 7-18-25; 8:45 am]
BILLING CODE 4910-13-P

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