Proposed Rule2026-05843
Airworthiness Directives; The Boeing Company Airplanes
Primary source
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Published
March 26, 2026
Issuing agencies
Transportation DepartmentFederal Aviation Administration
Abstract
The FAA proposes to adopt a new airworthiness directive (AD) certain The Boeing Company Model 737-700, -700C, -800, and -900ER series airplanes. This proposed AD was prompted by a leak through the form-in-place (FiP) gasket at the engine fuel shutoff valve access panel found during a leak check. This proposed AD would require a detailed inspection of the left and right side FiP gasket at the engine fuel shutoff valve access panel, for correct sealant installation, a fluid leak test of the engine fuel shutoff valve access panels for any leak, and applicable on-condition actions. The FAA is proposing this AD to address the unsafe condition on these products.
Full Text
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<title>Federal Register, Volume 91 Issue 58 (Thursday, March 26, 2026)</title>
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[Federal Register Volume 91, Number 58 (Thursday, March 26, 2026)]
[Proposed Rules]
[Pages 14654-14657]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2026-05843]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2026-2725; Project Identifier AD-2025-00999-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 adopt a new airworthiness directive (AD)
certain The Boeing Company Model 737-700, -700C, -800, and -900ER
series airplanes. This proposed AD was prompted by a leak through the
form-in-place (FiP) gasket at the engine fuel shutoff valve access
panel found during a leak check. This proposed AD would require a
detailed inspection of the left and right side FiP gasket at the engine
[[Page 14655]]
fuel shutoff valve access panel, for correct sealant installation, a
fluid leak test of the engine fuel shutoff valve access panels for any
leak, and applicable on-condition actions. 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 May 11,
2026.
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-2026-2725; 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:
<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-2026-2725.
FOR FURTHER INFORMATION CONTACT: Erica Bayles, Aviation Safety
Engineer, FAA, 2200 South 216th St., Des Moines, WA 98198; phone: 907-
271-5844; email: <a href="/cdn-cgi/l/email-protection#7613041f151758135814170f1a13053610171758111900"><span class="__cf_email__" data-cfemail="85e0f7ece6e4abe0abe7e4fce9e0f6c5e3e4e4abe2eaf3">[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 using a method listed
under the ADDRESSES section. Include ``Docket No. FAA-2026-2725;
Project Identifier AD-2025-00999-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 Erica
Bayles, Aviation Safety Engineer, FAA, 2200 South 216th St., Des
Moines, WA 98198; phone: 907-271-5844; email: <a href="/cdn-cgi/l/email-protection#fe9b8c979d9fd09bd09c9f87929b8dbe989f9fd0999188"><span class="__cf_email__" data-cfemail="7712051e141659125915160e1b12043711161659101801">[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 a report indicating a leak through the FiP
gasket at the engine fuel shutoff valve access panel was found during a
leak check, completed as part of a non-conformance disposition for the
Boeing Company Model 737-8, 737-9, and 737-8200 airplanes. An
investigation found that the fairing requirements of the engine fuel
shutoff valve access panel caused thin regions of the FiP gasket. This
caused the manufacturer to apply non-permitted sealant after the
initial FiP gasket had cured, which resulted in an uneven sealing
surface on the engine fuel shutoff valve access panel and leak. Non-
conforming FiP gasket installations may compromise the designated
drainage provision in the wing leading edge area. This condition, if
not addressed, could result in fuel leaking onto the engine exhaust
nozzle and a consequent fire on the ground.
Boeing determined that Model 737-700, -700C, -800, and -900ER
series airplanes are also subject to the identified unsafe condition
due to design similarity of the FiP gasket. The FAA is considering
separate rulemaking for the affected Boeing Company Model 737-8, 737-9,
and 737-8200 airplanes.
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 737-57A1359 RB,
dated October 3, 2025. This material specifies procedures for a
detailed inspection of the FiP gasket at the engine fuel shutoff valve
access panel of the left and right side wing for correct sealant
installation, a fluid leak test of the engine fuel shutoff valve access
panels for any leak, and applicable on-condition actions. On-condition
actions include replacing the FiP gasket, repairing any leaks, and
repeating the leak test until no leak is 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-2026-2725.
Differences Between This Proposed AD and the Referenced Material
Since Boeing Alert Requirements Bulletin 737-57A1359 RB, dated
October 3, 2025, was issued, the FAA has determined more airplanes are
affected by the unsafe condition. The line numbers affected are 2438
through 2598 inclusive, 2600 through 2721 inclusive, 2723 through 2813
inclusive, 2815 through 2930 inclusive, 2932
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through 3068 inclusive, 3070 through 3323 inclusive, 3325 through 3425
inclusive, 3427 through 3521 inclusive, 3523 through 3611 inclusive,
3613 through 3701 inclusive, 3703 through 3791 inclusive, and 3793
through 3833 inclusive. The FAA has added these lines numbers to the
applicability in paragraph (c) of this proposed AD.
Where Boeing Alert Requirements Bulletin 737-57A1359 RB, dated
October 3, 2025, specifies to do applicable on-condition corrective
actions if any leak is found, for this proposed AD, if any leak is
found the FiP gasket must be replaced. The FAA has added exceptions in
paragraphs (h)(2) through (4) of this proposed AD accordingly.
Costs of Compliance
The FAA estimates that this AD, if adopted as proposed, would
affect 1,030 airplanes of U.S. registry. The FAA estimates the
following costs to comply with this proposed AD:
Estimated Costs
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Cost per Cost on U.S.
Action Labor cost Parts cost product operators
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Inspection............................ 1 work-hour x $85 per $0 $85 $87,550
hour = $85.
Leak test............................. 1 work-hour x $85 per 0 85 87,550
hour = $85.
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The FAA estimates the following costs to do any necessary
replacements that would be required based on the results of the
proposed inspection. The agency has no way of determining the number of
aircraft that might need these replacements:
On-Condition Costs
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Cost per
Action Labor cost Parts cost product
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Replacement............................. 2 work-hours x $85 per Negligible................ $170
hour = $170.
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The FAA has received no definitive data on which to base the cost
estimates for the on-condition 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-2026-2725; Project Identifier AD-
2025-00999-T.
(a) Comments Due Date
The FAA must receive comments on this airworthiness directive
(AD) by May 11, 2026.
(b) Affected ADs
None.
(c) Applicability
This AD applies to The Boeing Company Model 737-700, -700C, -
800, and -900ER series airplanes, certificated in any category, as
identified in Boeing Alert Requirements Bulletin 737-57A1359 RB,
dated October 3, 2025; and airplanes having line numbers 2438
through 2598 inclusive, 2600 through 2721 inclusive, 2723 through
2813 inclusive, 2815 through 2930 inclusive, 2932 through 3068
inclusive, 3070 through 3323 inclusive, 3325 through 3425 inclusive,
3427 through 3521 inclusive, 3523 through 3611 inclusive, 3613
through 3701 inclusive, 3703 through 3791 inclusive, and 3793
through 3833 inclusive.
(d) Subject
Air Transport Association (ATA) of America Code 57, Wings.
(e) Unsafe Condition
This AD was prompted by a leak through the form-in-place (FiP)
gasket at the engine fuel shutoff valve access panel found during
[[Page 14657]]
a leak check. An investigation found that the fairing requirements
of the engine fuel shutoff valve access panel caused thin regions of
the FiP gasket, which caused non-permitted sealant to be applied
after the initial FiP gasket had cured, resulting in an uneven
sealing surface on the engine fuel shutoff valve access panel and
leak. The FAA is issuing this AD to address incorrect or missing
sealant installation. The unsafe condition, if not addressed, could
result in fuel leaking onto the engine exhaust nozzle and a possible
fire on the ground.
(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 737-57A1359 RB, dated October 3, 2025,
do all applicable actions identified in, and in accordance with, the
Accomplishment Instructions of Boeing Alert Requirements Bulletin
737-57A1359 RB, dated October 3, 2025.
Note 1 to paragraph (g): Guidance for accomplishing the actions
required by this AD can be found in Boeing Alert Service Bulletin
737-57A1359, dated October 3, 2025, which is referred to in Boeing
Alert Requirements Bulletin 737-57A1359 RB, dated October 3, 2025.
(h) Exceptions to Requirements Bulletin Specifications
(1) Where the Compliance Time columns of the tables in the
``Compliance'' paragraph of Boeing Alert Requirements Bulletin 737-
57A1359 RB, dated October 3, 2025, refer to the original issue date
of Requirements Bulletin 737-57A1359 RB, this AD requires using the
effective date of this AD.
(2) Where Table 1 and Table 2 in the Compliance and
Accomplishment Instructions paragraphs of Boeing Alert Requirements
Bulletin 737-57A1359 RB, dated October 3, 2025, specifies ``Do a
fluid leak test of the engine fuel shutoff valve access panel for
any leak. If any leak is found, do all applicable on-condition
corrective action(s) and repeat the leak test until no leak is
found'', this AD requires replacing that text with ``Do a fluid leak
test of the engine fuel shutoff valve access panel for any leak. If
any leak is found, replace the FiP gasket and repeat the leak test
until no leak is found''.
(3) Where step 4. b. of Appendix A in Boeing Alert Requirements
Bulletin 737-57A1359 RB, dated October 3, 2025, specifies ``If any
water leaks from the engine fuel shutoff valve access panel in less
than two minutes, the fluid leak test has failed'', this AD requires
replacing that text with ``If any water leaks from the engine fuel
shutoff valve access panel in less than two minutes, the fluid leak
test has failed. Replace the FiP gasket in accordance with Figure 3
and repeat the leak test until no leak is found''.
(4) Where step 4. b. of Appendix B in Boeing Alert Requirements
Bulletin 737-57A1359 RB, dated October 3, 2025, specifies ``If any
water leaks from the engine fuel shutoff valve access panel in less
than two minutes, the fluid leak test has failed'', this AD requires
replacing that text with ``If any water leaks from the engine fuel
shutoff valve access panel in less than two minutes, the fluid leak
test has failed. Replace the FiP gasket in accordance with Figure 4
and repeat the leak test until no leak is found''.
(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 Continued Operational
Safety Branch, send it to the attention of the person identified in
paragraph (j) of this AD. Information may be emailed to:
<a href="/cdn-cgi/l/email-protection#0b4a4644484b6d6a6a256c647d"><span class="__cf_email__" data-cfemail="fabbb7b5b9ba9c9b9bd49d958c">[email protected]</span></a>. Before using any approved AMOC, notify your
appropriate principal inspector, or lacking a principal inspector,
the manager of the responsible Flight Standards Office.
(2) 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) Additional Information
For more information about this AD, contact Erica Bayles,
Aviation Safety Engineer, FAA, 2200 South 216th St., Des Moines, WA
98198; phone: 907-271-5844; email: <a href="/cdn-cgi/l/email-protection#0c697e656f6d2269226e6d7560697f4c6a6d6d226b637a"><span class="__cf_email__" data-cfemail="5c392e353f3d7239723e3d2530392f1c3a3d3d723b332a">[email protected]</span></a>.
(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 737-57A1359 RB, dated
October 3, 2025.
(ii) [Reserved]
(3) 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 <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#4d2b3f6324233e3d282e392422230d232c3f2c632a223b"><span class="__cf_email__" data-cfemail="6402164a0d0a17140107100d0b0a240a0516054a030b12">[email protected]</span></a>.
Issued on March 23, 2026.
Peter A. White,
Deputy Director, Integrated Certificate Management Division, Aircraft
Certification Service.
[FR Doc. 2026-05843 Filed 3-25-26; 8:45 am]
BILLING CODE 4910-13-P
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