Special Conditions: Honeywell International Inc., Boeing Model 757-200, 757-200PF, 757-200CB, and 757-300 Airplanes; Non-Rechargeable Lithium Batteries and Battery System Installation

[Federal Register Volume 91, Number 73 (Thursday, April 16, 2026)]
[Rules and Regulations]
[Pages 20319-20321]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2026-07484]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-2026-3506; Special Conditions No. 25-889-SC]


Special Conditions: Honeywell International Inc., Boeing Model 
757-200, 757-200PF, 757-200CB, and 757-300 Airplanes; Non-Rechargeable 
Lithium Batteries and Battery System Installation

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions; request for comments.

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SUMMARY: These special conditions are issued for the Boeing Company 
(Boeing) 757 series airplane models 757-200, 757-200PF, 757-200CB, and 
757-300. These airplanes, as modified by Honeywell International, Inc. 
(Honeywell), will have a novel or unusual design feature when compared 
to the state of technology envisioned in the airworthiness standards 
for transport-category airplanes. This design feature is for the 
installation of non-rechargeable lithium batteries in an underwater 
locator beacon (ULB). The applicable airworthiness regulations do not 
contain adequate or appropriate safety standards for this design 
feature. These special conditions contain the additional safety 
standards that the Administrator considers necessary to establish a 
level of safety equivalent to that established by the existing 
airworthiness standards.

DATES: This action is effective on Honeywell on April 16, 2026. Send 
comments on or before June 1, 2026.

ADDRESSES: Send comments identified by Docket No. FAA-2026-3506 using 
any of the following methods:
    •  Federal eRegulations Portal: Go to www.regulations.gov and 
follow the online instructions for sending your comments 
electronically.
    •  Mail: Send comments to Docket Operations, M-30, U.S. 
Department of Transportation (DOT), 1200 New Jersey Avenue SE, Room 
W12-140, West Building Ground Floor, Washington, DC 20590-0001.
    •  Hand Delivery or Courier: Take comments to Docket 
Operations in Room W12-140 of the West Building Ground Floor at 1200 
New Jersey Avenue SE, Washington, DC, between 9 a.m. and 5 p.m., Monday 
through Friday, except Federal holidays.
    •  Fax: Fax comments to Docket Operations at 202-493-2251.
    Docket: Background documents or comments received may be read at 
www.regulations.gov at any time. Follow the online instructions for 
accessing the docket or go to Docket Operations in Room W12-140 of the 
West Building Ground Floor at 1200 New Jersey Avenue SE, Washington, 
DC, between 9 a.m. and 5 p.m., Monday through Friday, except Federal 
holidays.

FOR FURTHER INFORMATION CONTACT: Nazih Khaouly, Aircraft Systems, AIR-
626A, Technical Innovation Policy Branch, Policy and Innovation 
Division, Aircraft Certification Service, Federal Aviation 
Administration, 2200 South 216th Street, Des Moines, Washington 98198; 
telephone and fax 206-231-3160; email nazih.khaouly@faa.gov.

SUPPLEMENTARY INFORMATION: The substance of these special conditions 
has been published in the Federal Register for public comment in 
several prior instances with no substantive comments received. 
Therefore, the FAA finds, pursuant to 14 CFR 11.38(b), that new 
comments are unlikely, and notice and comment prior to this publication 
are unnecessary.

Privacy

    Except for Confidential Business Information (CBI) as described in 
the following paragraph, and other information as described in title 
14, Code of Federal Regulations (14 CFR) 11.35, the FAA will post all 
comments received without change to www.regulations.gov, including any 
personal information you provide. The FAA will also post a report 
summarizing each substantive verbal contact received about these 
special conditions.

Confidential Business Information

    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 
these special conditions contain commercial or financial information 
that is customarily treated as private, that you actually treat as 
private, and that is relevant or responsive to these special 
conditions, 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 the indicated comments will not be 
placed in the public docket of these special conditions. Send 
submissions containing CBI to the individual listed in the FOR FURTHER 
INFORMATION CONTACT section above. Comments the FAA receives, which are 
not specifically designated as CBI, will be placed in the public docket 
for these proposed special conditions.

Comments Invited

    The FAA invites interested people to take part in this rulemaking 
by sending written comments, data, or views. The most helpful comments 
reference a specific portion of the special conditions, explain the 
reason for any recommended change, and include supporting data.

[[Page 20320]]

    The FAA will consider all comments received by the closing date for 
comments. The FAA may change these special conditions based on the 
comments received.

Background

    On January 8, 2026, Honeywell applied for a supplemental type 
certificate for the installation of non-rechargeable lithium batteries 
in the ULB in the Boeing Model 757-200, 757-200PF, 757-200CB, 757-300 
series airplanes. These airplanes, approved under Type Certificate No. 
A2NM, are twin engine transport category airplanes. The Boeing Model 
757-200, 757-200PF, 757-200CB, 757-300 series airplanes have a maximum 
passenger range between 7 and 239 passengers, and a maximum takeoff 
weight range between 230,500 and 273,000 pounds, depending on model and 
configuration.

Type Certification Basis

    Under the provisions of title 14, Code of Federal Regulations (14 
CFR) 21.101, Honeywell must show that the Boeing Model 757-200, 757-
200PF, 757-200CB, 757-300 series airplanes, as changed, continue to 
meet the applicable provisions of the regulations listed in Type 
Certificate No. A2NM or the applicable regulations in effect on the 
date of application for the change, except for earlier amendments as 
agreed upon by the FAA.
    If the Administrator finds that the applicable airworthiness 
regulations (e.g., 14 CFR part 25) do not contain adequate or 
appropriate safety standards for the Boeing Model 757-200, 757-200PF, 
757-200CB, and 757-300 airplanes because of a novel or unusual design 
feature, special conditions are prescribed under the provisions of 
Sec.  21.16.
    Special conditions are initially applicable to the model for which 
they are issued. Should the Honeywell apply for a supplemental type 
certificate to modify any other model included on the same type 
certificate to incorporate the same novel or unusual design feature, 
these special conditions would also apply to the other model under 
Sec.  21.101.
    In addition to the applicable airworthiness regulations and special 
conditions, the Boeing Model 757-200, 757-200PF, 757-200CB, 757-300 
series airplanes must comply with the exhaust-emission requirements of 
14 CFR part 34, and the noise-certification requirements of 14 CFR part 
36.
    The FAA issues special conditions, as defined in 14 CFR 11.19, in 
accordance with Sec.  11.38, and they become part of the type 
certification basis under Sec.  21.101.

Novel or Unusual Design Features

    The Boeing Model 757-200, 757-200PF, 757-200CB, 757-300 series 
airplanes, as modified by Honeywell, will incorporate the following 
novel or unusual design feature:The installation of non-rechargeable 
lithium batteries in the underwater locator beacon (ULB).

Discussion

    The FAA derived the current regulations governing installation of 
batteries in transport-category airplanes from Civil Air Regulations 
(CAR) 4b.625(d), as part of the recodification of CAR 4b, which 
established 14 CFR part 25 in February 1965. This recodification 
essentially reworded the CAR 4b battery requirements, which are 
currently in Sec.  25.1353(b)(1) through (4). Non-rechargeable lithium 
batteries and battery systems are novel and unusual with respect to the 
state of technology considered when these requirements were codified. 
Non-rechargeable lithium batteries and battery systems introduce higher 
energy levels into airplane systems through new chemical compositions 
in various battery-cell sizes and construction. Interconnection of 
these cells in battery packs introduce failure modes that require 
unique design considerations, such as provisions for thermal 
management.
    In January 2013, two independent events involving rechargeable 
lithium-ion batteries revealed unanticipated failure modes. A National 
Transportation Safety Board letter to the FAA, dated May 22, 2014, 
which is available at https://www.ntsb.gov, filename A-14-032-036.pdf, 
describes these events.
    On July 12, 2013, an event involving a non-rechargeable lithium 
battery in an ELT installation demonstrated unanticipated failure 
modes. The United Kingdom's Air Accidents Investigation Branch Bulletin 
S5/2013 \1\ describes this event. These events, involving rechargeable 
and non-rechargeable lithium batteries, prompted the FAA to initiate a 
broad evaluation of these energy-storage technologies.
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    \1\ See Aircraft Accident Report 2/2015--Boeing B787-8, ET-AOP, 
12 July 2013 Ground fire at London Heathrow Airport on 12 July 2013. 
www.gov.uk/aaib-reports/aircraft-accident-report-2-2015-boeing-b787-
8-et-aop-12-july-2013.
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    On April 22, 2016, the FAA published special conditions No. 25-612-
SC in the Federal Register (81 FR 23573), applicable to Gulfstream 
Aerospace Corporation, for the Model GVI airplane. Those were the first 
special conditions the FAA issued for non-rechargeable lithium battery 
installations. In that document, the FAA explained its decision to make 
those special conditions effective on April 22, 2017, one year after 
publication in the Federal Register. In those special conditions, the 
FAA stated its intention to apply non-rechargeable lithium battery and 
battery system special conditions to design changes on other airplane 
makes and models applied for after this same date.
    Special condition 1 of these special conditions requires that each 
individual cell within a non-rechargeable lithium battery and battery 
system be designed to maintain safe temperatures and pressures. Special 
condition 2 addresses these same issues but for the entire battery. 
Special condition 2 requires the battery be designed to prevent 
propagation of a thermal event, such as self-sustained, uncontrollable 
increases in temperature or pressure from one cell to adjacent cells.
    Special conditions 1 and 2 are intended to ensure that the non-
rechargeable lithium battery and its cells are designed to eliminate 
the potential for uncontrollable failures. However, a certain number of 
failures will occur due to various factors beyond the control of the 
battery designer. Therefore, other special conditions are intended to 
protect the airplane and its occupants if failure occurs.
    Special conditions 3, 7, and 8 are self-explanatory.
    Special condition 4 makes it clear that the flammable-fluid fire-
protection requirements of Sec.  25.863 apply to non-rechargeable 
lithium battery and battery system installations. Section 25.863 is 
applicable to areas of the airplane that could be exposed to flammable-
fluid leakage from airplane systems. Non-rechargeable lithium batteries 
and battery systems contain an electrolyte that is a flammable fluid.
    Special condition 5 requires that each non-rechargeable lithium 
battery and battery system installation not damage surrounding 
structure or adjacent systems, equipment, or electrical wiring from 
corrosive fluids or gases that may escape in such a way as to cause a 
major or more severe failure condition.
    While special condition 5 addresses corrosive fluids and gases, 
special condition 6 addresses heat. Special condition 6 requires that 
each non-rechargeable lithium battery and battery system installation 
have provisions to prevent any hazardous effect on airplane structure 
or systems caused by the maximum amount of heat the battery 
installation can generate due to any failure of it or its individual 
cells. The means of meeting special conditions 5 and 6 may be the same, 
but

[[Page 20321]]

the requirements are independent and address different hazards.
    These special conditions apply to all non-rechargeable lithium 
battery and battery system installations, in lieu of Sec.  
25.1353(b)(1) through (4) at amendment 25-123. Sections 25.1353(b)(1) 
through (4) at amendment 25-123 remain in effect for other battery 
installations.
    These special conditions contain the additional safety standards 
that the Administrator considers necessary to establish a level of 
safety equivalent to that established by the existing airworthiness 
standards.

Applicability

    As discussed above, these special conditions are applicable to the 
Boeing Model 757-200, 757-200PF, 757-200CB, 757-300 series airplanes, 
as modified by Honeywell. Should Honeywell apply at a later date for a 
supplemental type certificate to modify any other model included on 
Type Certificate No. A2NM to incorporate the same novel or unusual 
design feature, these special conditions would apply to that model as 
well.

Conclusion

    This action affects only a certain novel or unusual design feature 
on the Boeing Model 757-200, 757-200PF, 757-200CB, 757-300 series 
airplanes. It is not a rule of general applicability and affects only 
the applicant who applied to the FAA for approval of these features on 
the airplane.

List of Subjects in 14 CFR Part 25

    Aircraft, Aviation safety, Reporting and recordkeeping 
requirements.

Authority Citation

    The authority citation for these special conditions is as follows:

    Authority:  49 U.S.C. 106(f), 40113, 44701, 44702, and 44704.

The Special Conditions

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the following special conditions are issued as part of 
the type certification basis for the Boeing Model 757-200, 757-200PF, 
757-200CB, 757-300 series airplanes, as modified by Honeywell.
    In lieu of Sec.  25.1353(b)(1) through (4) at amendment 25-123, or 
Sec.  25.1353(c)(1) through (4) at earlier amendments, each non-
rechargeable lithium battery and battery system installation must:
    1. Be designed to maintain safe cell temperatures and pressures, 
under all foreseeable operating conditions, to prevent fire and 
explosion.
    2. Be designed to prevent the occurrence of self-sustaining, 
uncontrollable increases in temperature or pressure.
    3. Not emit explosive or toxic gases, either in normal operation or 
as a result of its failure, that may accumulate in hazardous quantities 
within the airplane.
    4. Meet the requirements of Sec.  25.863.
    5. Not damage surrounding structure or adjacent systems, equipment, 
or electrical wiring from corrosive fluids or gases that may escape in 
such a way as to cause a major or more severe failure condition.
    6. Have provisions to prevent any hazardous effect on airplane 
structure or systems caused by the maximum amount of heat it can 
generate due to any failure of it or its individual cells.
    7. Have a failure-sensing and warning system to alert the flight 
crew, in the event its failure affects safe operation of the airplane.
    8. Have a means for the flight crew or maintenance personnel to 
determine the battery charge state if the battery's function is 
required for safe operation of the airplane.

    Note: A battery system consists of the battery, battery charger, 
and any protective monitoring and alerting circuitry or hardware 
inside or outside of the battery. It also includes vents (where 
necessary) and packaging. For the purpose of these special 
conditions, a battery and the battery system is referred to as a 
battery.


    Issued in Fort Worth, Texas, on April 13, 2026.
Jorge R. Castillo,
Manager, Technical Policy Branch, Policy and Standards Division, 
Aircraft Certification Service.
[FR Doc. 2026-07484 Filed 4-15-26; 8:45 am]
BILLING CODE 4910-13-P