Airworthiness Directives; The Boeing Company Airplanes

[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 [www.gpo.gov]
[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 regulations.gov. 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 regulations.gov 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: [email protected].

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 
regulations.gov, 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: 
[email protected]. 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
----------------------------------------------------------------------------------------------------------------
AFM Revision..........................  1 work-hour x $85 per                 $0             $85         $65,535
                                         hour = $85.
----------------------------------------------------------------------------------------------------------------

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: [email protected]. 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: [email protected]

(j) Material Incorporated by Reference

    None.
BILLING CODE 4910-13-P

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Appendix 1 of AD 2026-04-05--Cabin Temperature Hot Procedure
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Appendix 2 to AD 2026-04-05--Cabin Temperature Hot BAT BUS SECT 2 
Circuit Breaker Trips Procedure
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Appendix 3 of AD 2026-04-05--PACK Procedure
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    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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