Rule2026-03615
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
February 24, 2026
Effective
February 24, 2026
Issuing agencies
Transportation DepartmentFederal Aviation Administration
Abstract
The FAA is adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-8, 737-9, and 737-8200 airplanes. This AD was prompted by reports of in-flight events of excessive cabin and flight deck temperatures that could not be controlled by the flightcrew using existing procedures. This AD requires revising the existing airplane flight manual (AFM) to provide the flightcrew with operating procedures (non-normal checklists) if a certain circuit breaker in the standby power control unit (SPCU) trips. The FAA is issuing this AD to address the unsafe condition on these products.
Full Text
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<title>Federal Register, Volume 91 Issue 36 (Tuesday, February 24, 2026)</title>
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[Federal Register Volume 91, Number 36 (Tuesday, February 24, 2026)]
[Rules and Regulations]
[Pages 8708-8720]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2026-03615]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2026-1332; Project Identifier AD-2026-00084-T;
Amendment 39-23265; AD 2026-04-05]
RIN 2120-AA64
Airworthiness Directives; The Boeing Company Airplanes
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Final rule; request for comments.
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SUMMARY: The FAA is adopting a new airworthiness directive (AD) for all
The Boeing Company Model 737-8, 737-9, and 737-8200 airplanes. This AD
was prompted by reports of in-flight events of excessive cabin and
flight deck temperatures that could not be controlled by the flightcrew
using existing procedures. This AD requires revising the existing
airplane flight manual (AFM) to provide the flightcrew with operating
procedures (non-normal checklists) if a certain circuit breaker in the
standby power control unit (SPCU) trips. The FAA is issuing this AD to
address the unsafe condition on these products.
DATES: This AD is effective February 24, 2026.
The FAA must receive comments on this AD by April 10, 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> by
searching for and locating Docket No. FAA-2026-1332; 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 street address for Docket
Operations is listed above.
FOR FURTHER INFORMATION CONTACT: Derrick Herrera, Aviation Safety
[[Page 8709]]
Engineer, FAA, 2200 South 216th St., Des Moines, WA 98198; phone: 817-
222-5140; email: <a href="/cdn-cgi/l/email-protection#e98d8c9b9b808a82c79bc7818c9b9b8c9b88a98f8888c78e869f"><span class="__cf_email__" data-cfemail="f09495828299939bde82de98958282958291b0969191de979f86">[email protected]</span></a>.
SUPPLEMENTARY INFORMATION:
Comments Invited
The FAA invites you to send any written data, views, or arguments
about this final rule. Send your comments using a method listed under
the ADDRESSES section. Include Docket No. FAA-2026-1332 and Project
Identifier AD-2026-00084-T at the beginning of your comments. The most
helpful comments reference a specific portion of the final rule,
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 final rule 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 final rule.
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 AD 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 AD, 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 AD. Submissions containing CBI should be sent to Derrick
Herrera, Aviation Safety Engineer, FAA, 2200 South 216th St., Des
Moines, WA 98198; phone: 817-222-5140; email:
<a href="/cdn-cgi/l/email-protection#781c1d0a0a111b13560a56101d0a0a1d0a19381e1919561f170e"><span class="__cf_email__" data-cfemail="593d3c2b2b303a32772b77313c2b2b3c2b38193f3838773e362f">[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 two reports of in-flight events of excessive
cabin and flight deck temperatures that could not be controlled by the
flightcrew using existing procedures. An investigation found these
events resulted from the BAT BUS SECT 2 circuit breaker (CB3062) on the
SPCU tripping. The SPCU gives automatic and manual control of the
battery and standby buses. The BAT BUS SECT 2 provides power to air
conditioning and cabin pressure functions, including the left and right
pack flow control valve solenoids (On/Off), left and right pack
overheat protection circuits, zone supply duct overheat protection
circuits, and cabin pressure manual mode control. The BAT BUS SECT 2
circuit breaker trip causes an unintended erroneous electrical ground
signal to the smart ram air door actuators (SRADAs), which in turn
causes both ram air deflector doors to extend (close), thus reducing
cooling airflow to the air conditioning heat exchangers. The reduced
airflow causes insufficient cooling of the hot bleed air, which causes
both packs to supply excessively hot air to the cabin and flight deck.
This air conditioning system malfunction could cause an uncontrollable,
excessively high temperature in the cabin and flight deck. This
condition, if not addressed, could lead to injury or incapacitation of
flightcrew and passengers, which could result in the inability to
maintain safe flight and landing. The FAA is issuing this AD to address
the unsafe condition on these products.
Explanation of Existing AFM Procedures and Procedures Required by This
AD
This AD provides flightcrew procedures for a controlled descent, an
attempt to reset the tripped BAT BUS SECT 2 circuit breaker and, if
that attempt is unsuccessful, selecting engine bleed switches OFF. This
AD includes three AFM procedures, one of which is revised (Cabin
Temperature Hot procedure) as shown in Appendix 1 of this AD, another
of which is new (Cabin Temperature Hot BAT BUS Sect 2 Circuit Breaker
Trips procedure) as shown in Appendix 2 of this AD, and the other
procedure currently exists in the quick reference handbook (QRH) but
not in the existing AFM (PACK procedure) as shown in Appendix 3.
FAA's Determination
The FAA is issuing this AD because the agency has determined the
unsafe condition described previously is likely to exist or develop in
other products of the same type design.
AD Requirements
This AD requires revising the Operating Procedures section of the
existing AFM to provide the flightcrew with non-normal checklists if
the BAT BUS SECT 2 circuit breaker in the SPCU trips.
Interim Action
The FAA considers this AD to be an interim action. An assessment of
the SPCU found that two environmental control system (ECS) circuit
breakers (C262 and C263) downstream of the SPCU may also trip. The FAA
is considering further rulemaking to provide flightcrew procedures for
addressing tripped ECS circuit breakers. Additionally, the manufacturer
is currently developing a modification to address the unsafe condition
identified in this AD. Once this modification is developed, FAA-
approved, and available, the FAA might consider additional rulemaking.
Justification for Immediate Adoption and Determination of the Effective
Date
Section 553(b) of the Administrative Procedure Act (APA) (5 U.S.C.
551 et seq.) authorizes agencies to dispense with notice and comment
procedures for rules when the agency, for ``good cause,'' finds that
those procedures are ``impracticable, unnecessary, or contrary to the
public interest.'' Under this section, an agency, upon finding good
cause, may issue a final rule without providing notice and seeking
comment prior to issuance. Further, section 553(d) of the APA
authorizes agencies to make rules effective in less than thirty days,
upon a finding of good cause.
An unsafe condition exists that requires the immediate adoption of
this AD without providing an opportunity for public comments prior to
adoption. The FAA has found that the risk to the flying public
justifies forgoing notice and comment prior to adoption of this rule
because a tripped BAT BUS SECT 2 circuit breaker, and resulting effects
on the cabin environment that cannot be controlled via normal
procedures, could lead to injury or incapacitation of flightcrew and
passengers, which could result in the inability to maintain safe flight
and landing. Additionally, the compliance time in this AD is shorter
than the time necessary for the public to comment and for publication
of the final rule. Accordingly, notice and opportunity for prior public
comment are impracticable and contrary to the public interest pursuant
to 5 U.S.C. 553(b).
In addition, the FAA finds that good cause exists pursuant to 5
U.S.C. 553(d) for making this amendment effective in less than 30 days,
for the same reasons the FAA found good cause to forgo notice and
comment.
[[Page 8710]]
Regulatory Flexibility Act
The requirements of the Regulatory Flexibility Act (RFA) do not
apply when an agency finds good cause pursuant to 5 U.S.C. 553 to adopt
a rule without prior notice and comment. Because the FAA has determined
that it has good cause to adopt this rule without notice and comment,
RFA analysis is not required.
Costs of Compliance
The FAA estimates that this AD affects 771 airplanes of U.S.
registry. The FAA estimates the following costs to comply with this AD:
Estimated Costs
----------------------------------------------------------------------------------------------------------------
Cost per Cost on U.S.
Action Labor cost Parts cost product operators
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AFM Revision.......................... 1 work-hour x $85 per $0 $85 $65,535
hour = $85.
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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, and
(2) Will not affect intrastate aviation in Alaska.
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(g), 40113, 44701.
Sec. 39.13 [Amended]
0
2. The FAA amends Sec. 39.13 by adding the following new airworthiness
directive:
2026-04-05 The Boeing Company: Amendment 39-23265; Docket No. FAA-
2026-1332; Project Identifier AD-2026-00084-T.
(a) Effective Date
This airworthiness directive (AD) is effective February 24,
2026.
(b) Affected ADs
None.
(c) Applicability
This AD applies to all The Boeing Company Model 737-8, 737-9,
and 737-8200 airplanes, certificated in any category.
(d) Subject
Air Transport Association (ATA) of America Code 24, Electrical
Power.
(e) Unsafe Condition
This AD was prompted by reports of in-flight events of excessive
cabin and flight deck temperatures that could not be controlled by
the flightcrew using existing procedures. The FAA is issuing this AD
to address a tripped BAT BUS SECT 2 circuit breaker that could lead
to an air conditioning system malfunction causing an uncontrollable,
excessively high temperature in the cabin and flight deck. The
unsafe condition, if not addressed, could lead to injury or
incapacitation of flightcrew and passengers, which could result in
the inability to maintain safe flight and landing.
(f) Compliance
Comply with this AD within the compliance times specified,
unless already done.
(g) Revision of Existing Airplane Flight Manual (AFM)
Within 30 days after the effective date of this AD, revise the
Operating Procedures section of the existing AFM to include the
information specified in appendices 1 through 3 of this AD. This may
be done by inserting a copy of appendices 1 through 3 of this AD
into the AFM.
(h) 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 (i)
of this AD. Information may be emailed to: <a href="/cdn-cgi/l/email-protection#37767a78747751565619505841"><span class="__cf_email__" data-cfemail="7534383a36351314145b121a03">[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.
(i) Additional Information
For more information about this AD, contact Derrick Herrera,
Aviation Safety Engineer, FAA, 2200 South 216th St., Des Moines, WA
98198; phone: 817-222-5140; email: <a href="/cdn-cgi/l/email-protection#610504131308020a4f134f09041313041300210700004f060e17"><span class="__cf_email__" data-cfemail="a1c5c4d3d3c8c2ca8fd38fc9c4d3d3c4d3c0e1c7c0c08fc6ced7">[email protected]</span></a>
(j) Material Incorporated by Reference
None.
BILLING CODE 4910-13-P
[[Page 8711]]
Appendix 1 of AD 2026-04-05--Cabin Temperature Hot Procedure
[GRAPHIC] [TIFF OMITTED] TR24FE26.000
[[Page 8712]]
[GRAPHIC] [TIFF OMITTED] TR24FE26.001
[[Page 8713]]
[GRAPHIC] [TIFF OMITTED] TR24FE26.002
[[Page 8714]]
[GRAPHIC] [TIFF OMITTED] TR24FE26.003
[[Page 8715]]
Appendix 2 to AD 2026-04-05--Cabin Temperature Hot BAT BUS SECT 2
Circuit Breaker Trips Procedure
[GRAPHIC] [TIFF OMITTED] TR24FE26.004
[[Page 8716]]
[GRAPHIC] [TIFF OMITTED] TR24FE26.005
[[Page 8717]]
[GRAPHIC] [TIFF OMITTED] TR24FE26.006
[[Page 8718]]
Appendix 3 of AD 2026-04-05--PACK Procedure
[GRAPHIC] [TIFF OMITTED] TR24FE26.007
[[Page 8719]]
[GRAPHIC] [TIFF OMITTED] TR24FE26.008
[[Page 8720]]
[GRAPHIC] [TIFF OMITTED] TR24FE26.009
Issued on February 17, 2026.
Lona C. Saccomando,
Acting Deputy Director, Integrated Certificate Management Division,
Aircraft Certification Service.
[FR Doc. 2026-03615 Filed 2-20-26; 4:15 pm]
BILLING CODE 4910-13-C
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