Proposed Rule2025-18833
Airworthiness Directives; The Boeing Company Airplanes
Primary source
Metadata and text below are from the Federal Register, a public-domain U.S. government work. Always verify the official published version before relying on it for any legal matter.
Published
September 29, 2025
Issuing agencies
Transportation DepartmentFederal Aviation Administration
Abstract
The FAA proposes to adopt a new airworthiness directive (AD) for all The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. This proposed AD was prompted by reports of shim installations at certain stub beam to longitudinal floor beam locations that were not installed per specifications, and an evaluation by the design approval holder indicating inadequate baseline inspections for cracking of the stub beam. This proposed AD would require repetitive inspections for any crack of the stub beam straps at certain stations and repairing any crack found. The FAA is proposing this AD to address the unsafe condition on these products.
Full Text
<html>
<head>
<title>Federal Register, Volume 90 Issue 186 (Monday, September 29, 2025)</title>
</head>
<body><pre>
[Federal Register Volume 90, Number 186 (Monday, September 29, 2025)]
[Proposed Rules]
[Pages 46535-46538]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2025-18833]
-----------------------------------------------------------------------
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2025-2548; Project Identifier AD-2024-00478-T]
RIN 2120-AA64
Airworthiness Directives; The Boeing Company Airplanes
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Notice of proposed rulemaking (NPRM).
-----------------------------------------------------------------------
SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD)
for all The Boeing Company Model 737-600, -700, -700C, -800, -900, and
-900ER series airplanes. This proposed AD was prompted by reports of
shim installations at certain stub beam to longitudinal floor beam
locations that were not installed per specifications, and an evaluation
by the design approval holder indicating inadequate baseline
inspections for cracking of the stub beam. This proposed AD would
require repetitive inspections for any crack of the stub beam straps at
certain stations and repairing any crack found. 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
13, 2025.
ADDRESSES: You may send comments, using the procedures found in 14 CFR
11.43 and 11.45, by any of the following methods:
<bullet> Federal eRulemaking Portal: Go to <a href="http://regulations.gov">regulations.gov</a>. Follow
the instructions for submitting comments.
<bullet> Fax: 202-493-2251.
<bullet> 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.
<bullet> 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 <a href="http://regulations.gov">regulations.gov</a> under
Docket No. FAA-2025-2548; or in person at
[[Page 46536]]
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:
<bullet> For Boeing material identified in this proposed 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 <a href="http://myboeingfleet.com">myboeingfleet.com</a>.
<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 <a href="http://regulations.gov">regulations.gov</a> under
Docket No. FAA-2025-2548.
FOR FURTHER INFORMATION CONTACT: Luis Cortez-Muniz, Aviation Safety
Engineer, FAA, 2200 South 216th St., Des Moines, WA 98198; phone: 206-
231-3958; email: <a href="/cdn-cgi/l/email-protection#8ee2fbe7fda0efa0ede1fcfaebf4a3e3fbe0e7f4cee8efefa0e9e1f8"><span class="__cf_email__" data-cfemail="f09c859983de91de939f8284958add9d859e998ab0969191de979f86">[email protected]</span></a>.
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 the ADDRESSES section. Include ``Docket No. FAA-2025-2548;
Project Identifier AD-2024-00478-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 this 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
<a href="http://regulations.gov">regulations.gov</a>, including any personal information you provide. The
agency will also post a report summarizing each substantive verbal
contact received about this NPRM.
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 Luis
Cortez-Muniz, Aviation Safety Engineer, FAA, 2200 South 216th St., Des
Moines, WA 98198; phone: 206-231-3958; email: <a href="/cdn-cgi/l/email-protection#abc7dec2d885ca85c8c4d9dfced186c6dec5c2d1ebcdcaca85ccc4dd"><span class="__cf_email__" data-cfemail="3b574e5248155a155854494f5e4116564e5552417b5d5a5a155c544d">[email protected]</span></a>. 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 has received reports of shim installations at the station
(STA) 559 to STA 639 stub beam to buttock line (BL) 45 longitudinal
floor beam locations that were not installed per specifications, and an
evaluation by the design approval holder indicating inadequate baseline
inspections for cracking of the stub beam. The FAA is issuing this AD
to address potential cracking in the stub beam strap. The unsafe
condition, if not addressed, could result in undetected cracks in the
stub beam strap that may grow in length and sever the strap, which
could adversely affect the structural integrity of the airplane.
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.
Material Incorporated by Reference Under 1 CFR Part 51
The FAA reviewed Boeing Alert Requirements Bulletin 737-53A1404 RB,
Revision 1, dated November 29, 2023. This material specifies procedures
for repetitive ultrasonic inspections for any crack of the stub beam
straps at STA 578 and STA 597, or STA 578 and STA 601, as applicable.
This material specifies procedures for repetitive ultrasonic and open
hole eddy current inspections for any crack of the stub beam straps at
STA 616 and STA 639. 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.
Proposed AD Requirements in This NPRM
This proposed AD would require accomplishing the actions specified
in the material already described except as discussed under
``Differences Between this Proposed AD and the Referenced Material,''
and 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 material at <a href="http://regulations.gov">regulations.gov</a> under Docket
No. FAA-2025-2548.
Differences Between This Proposed AD and the Referenced Material
Boeing received reports of several crack findings from operators
after accomplishment of Boeing Alert Requirements Bulletin 737-53A1404
RB, Revision 1, dated November 29, 2023. The crack findings were
discovered prior to the inspection threshold of 34,000 total flight
cycles, which is specified in the compliance tables in Boeing Alert
Requirements Bulletin 737-53A1404 RB, Revision 1, dated November 29,
2023. Further analysis by Boeing determined that the existing
compliance times in Boeing Alert Requirements Bulletin 737-53A1404 RB,
Revision 1, dated November 29, 2023, are inadequate and would need to
be reduced. Following coordination with Boeing, the FAA is proposing to
require reduced compliance times to address the unsafe condition and
maintain safety in the fleet.
Additionally, Boeing Alert Requirements Bulletin 737-53A1404 RB,
Revision 1, dated November 29, 2023, specifies reduced compliance times
for airplanes on which Boeing Business Jet (BBJ) Lower Cabin Altitude
Supplemental Type Certificate (STC) ST01697SE has been incorporated.
This proposed AD would require using those reduced compliance times,
but the reduction would be applied to the reduced compliance times
specified in paragraphs (g)(1) through (3) of this AD, not those
specified in Boeing Alert Requirements Bulletin 737-53A1404 RB,
Revision 1, dated November 29, 2023.
Costs of Compliance
The FAA estimates that this AD, if adopted as proposed, would
affect 1,981 airplanes of U.S. registry. The FAA estimates the
following costs to comply with this proposed AD:
[[Page 46537]]
Estimated Costs
----------------------------------------------------------------------------------------------------------------
Cost on U.S.
Action Labor cost Parts cost Cost per product operators
----------------------------------------------------------------------------------------------------------------
Inspections................... Up to 166 work-hours $0 Up to $14,110 per Up to $27,951,910 per
x $85 per hour = inspection cycle. inspection cycle.
$14,110 per
inspection cycle.
----------------------------------------------------------------------------------------------------------------
The FAA has received no definitive data on which to base the cost
estimates for the repairs specified in this proposed AD.
The FAA has included all known costs in its cost estimate.
According to the manufacturer, however, some or all of the costs of
this proposed AD may be covered under warranty, thereby reducing the
cost impact on affected operators.
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 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 this 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
0
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]
0
2. The FAA amends Sec. 39.13 by adding the following new airworthiness
directive:
The Boeing Company: Docket No. FAA-2025-2548; Project Identifier AD-
2024-00478-T.
(a) Comments Due Date
The FAA must receive comments on this airworthiness directive
(AD) by November 13, 2025.
(b) Affected ADs
None.
(c) Applicability
This AD applies to all The Boeing Company Model 737-600, -700, -
700C, -800, -900, and -900ER series airplanes, certificated in any
category.
(d) Subject
Air Transport Association (ATA) of America Code 53, Fuselage.
(e) Unsafe Condition
This AD was prompted by reports of shim installations at the
station (STA) 559 to STA 639 stub beam to buttock line (BL) 45
longitudinal floor beam locations that were not installed per
specifications, and an evaluation by the design approval holder
indicating inadequate baseline inspections for cracking of the stub
beam. The FAA is issuing this AD to address potential cracking in
the stub beam strap. The unsafe condition, if not addressed, could
result in undetected cracks in the stub beam strap that may grow in
length and sever the strap, which could adversely affect the
structural integrity of the airplane.
(f) Compliance
Comply with this AD within the compliance times specified,
unless already done.
(g) Required Inspections
At the applicable time specified in paragraphs (g)(1) through
(3) of this AD, except as required by paragraph (i) of this AD, do
all applicable inspections identified in, and in accordance with,
the Accomplishment Instructions of Boeing Alert Requirements
Bulletin 737-53A1404 RB, Revision 1, dated November 29, 2023. If no
cracking is found, repeat the inspections thereafter at intervals
not to exceed 4,000 flight cycles.
Note 1 to paragraph (g): Guidance for accomplishing the actions
required by this AD can be found in Boeing Alert Service Bulletin
737-53A1404, Revision 1, dated November 29, 2023, which is referred
to in Boeing Alert Requirements Bulletin 737-53A1404 RB, Revision 1,
dated November 29, 2023.
(1) For airplanes that have accumulated fewer than 30,000 total
flight cycles as of the effective date of this AD: Before 22,000
total flight cycles, or within 4,000 flight cycles after the
effective date of this AD, whichever occurs later.
(2) For airplanes that have accumulated 30,000 total flight
cycles or greater but fewer than 40,000 total flight cycles as of
the effective date of this AD: Within 2,000 flight cycles after the
effective date of this AD.
(3) For airplanes that have accumulated greater than 40,000
total flight cycles as of the effective date of this AD: Within
1,000 flight cycles after the effective date of this AD.
(h) Corrective Actions
If any cracking is found during any inspection required by
paragraph (g) of this AD, before further flight, repair using a
method approved in accordance with the procedures specified in
paragraph (j) of this AD.
(i) Compliance Time Exception for Certain Airplanes
For airplanes on which Boeing Business Jet (BBJ) Lower Cabin
Altitude Supplemental Type Certificate (STC) ST01697SE has been
incorporated: The flight cycle related compliance times are
different from those specified in paragraph (g) of this AD. All
initial compliance times (thresholds) specified in flight cycles
must be reduced to half of those specified in paragraphs (g)(1)
through (3) of this AD. All repeat interval compliance times
specified in flight cycles must be reduced to one-quarter of those
specified in paragraph (g) of this AD.
[[Page 46538]]
(j) 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 (k)
of this AD. Information may be emailed to: <a href="/cdn-cgi/l/email-protection#e0a1adafa3a0868181ce878f96"><span class="__cf_email__" data-cfemail="1a5b5755595a7c7b7b347d756c">[email protected]</span></a>.
(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.
(k) Related Information
(1) For more information about this AD, contact Luis Cortez-
Muniz, Aviation Safety Engineer, FAA, 2200 South 216th St., Des
Moines, WA 98198; phone: 206-231-3958; email: <a href="/cdn-cgi/l/email-protection#7b170e1208551a551814090f1e0156160e1512013b1d1a1a551c140d"><span class="__cf_email__" data-cfemail="c6aab3afb5e8a7e8a5a9b4b2a3bcebabb3a8afbc86a0a7a7e8a1a9b0">[email protected]</span></a>.
(2) Material identified in this AD that is not incorporated by
reference is available at the address specified in paragraph (l)(3)
this AD.
(l) 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 737-53A1404 RB, Revision
1, dated November 29, 2023.
(ii) [Reserved]
(3) For the 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 <a href="http://myboeingfleet.com">myboeingfleet.com</a>.
(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 <a href="http://www.archives.gov/federal-register/cfr/ibr-locations">www.archives.gov/federal-register/cfr/ibr-locations</a> or email <a href="/cdn-cgi/l/email-protection#98feeab6f1f6ebe8fdfbecf1f7f6d8f6f9eaf9b6fff7ee"><span class="__cf_email__" data-cfemail="accade82c5c2dfdcc9cfd8c5c3c2ecc2cddecd82cbc3da">[email protected]</span></a>.
Issued on September 16, 2025.
Lona C. Saccomando,
Acting Deputy Director, Integrated Certificate Management Division,
Aircraft Certification Service.
[FR Doc. 2025-18833 Filed 9-26-25; 8:45 am]
BILLING CODE 4910-13-P
</pre><script data-cfasync="false" src="/cdn-cgi/scripts/5c5dd728/cloudflare-static/email-decode.min.js"></script></body>
</html>Indexed from Federal Register on September 29, 2025.
This is legal information, not legal advice. Laws vary by jurisdiction and change frequently. Always verify current law with official sources and consult a licensed attorney in your jurisdiction for advice on your specific situation.