[Federal Register Volume 90, Number 106 (Wednesday, June 4, 2025)]
[Rules and Regulations]
[Pages 23610-23612]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2025-10180]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. FAA-2025-0968; Special Conditions No. 25-879-SC]
Special Conditions: Delta Flight Products, Non-Rechargeable
Lithium Batteries and Battery System Installations
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Final special conditions; request for comments.
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SUMMARY: These special conditions are issued for a supplemental type
certificate (STC) to install non-rechargeable lithium batteries and
battery systems on certain transport-category airplanes. These
airplanes, as modified by Delta Flight Products, 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 non-rechargeable lithium batteries
and battery system installed in emergency locator transmitters (ELTs).
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 Delta Flight Products on June 4,
2025. Send comments on or before July 21, 2025.
ADDRESSES: Send comments identified by Docket No. FAA-2025-0968 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, Electrical Systems,
AIR-626A, Technical Policy Branch, Policy and Standards Division,
Aircraft Certification Service, Federal Aviation Administration, 2200 S
216th Street, Des Moines, Washington 98198; telephone and fax 206-231-
3160; email [email protected].
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.
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 December 19, 2024, Delta Flight Products applied for a
supplemental type certificate ST12026AT to install non-rechargeable
lithium batteries and battery systems in ELTs. Delta Flight Products
intends to apply this STC to multiple transport-category airplanes, and
may periodically amend this STC to expand its applicability to include
additional transport-category airplane makes and models.
Type Certification Basis
Under the provisions of title 14, Code of Federal Regulations (14
CFR) 21.101, Delta Flight Products must show that the airplanes, for
which they make application to modify by FAA STC ST12026AT, as changed,
continue to meet the applicable provisions of the regulations listed in
each airplane's respective type certificate 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
[[Page 23611]]
(i.e., 14 CFR part 25) do not contain adequate or appropriate safety
standards 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 applicant apply for a supplemental type
certificate to modify any other model included on the same type
certificate that incorporates 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 airplanes modified by STC ST12026AT must comply with
the fuel-vent and 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 airplanes listed in the FAA STC ST12026AT approved model list
(AML) will incorporate the following novel or unusual design feature:
Non-rechargeable lithium batteries and battery systems installed in
ELTs.
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 constructions. Interconnection of
these cells in battery packs introduces 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 Safety Recommendation to the FAA, dated May
22, 2014, which is available at 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 reevaluate
these energy-storage technologies.
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\1\ See Aircraft 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 no. 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 no. 2 addresses these same issues but for the entire
battery. Special condition no. 2 requires the battery to 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 condition nos. 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 no. 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 no. 5 requires that each non-rechargeable lithium
battery and battery system installation not damage the 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 no. 5 addresses corrosive fluids and gases,
special condition no. 6 addresses heat. Special condition no. 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 nos. 5 and 6
may be the same, but 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
airplane models listed on the AML of STC ST12026AT, available online at
drs.faa.gov.
All models listed in the AML must be evaluated and determined to
comply with these special conditions. Additionally, each new model
added to the AML subsequently must also be evaluated and determined to
comply with these special conditions.
Should Delta Flight Products apply for a change at a later date to
STC ST12026AT to include any other model on the AML incorporating the
same novel or unusual design feature, these special conditions would
apply to that model as well.
Should Delta Flight Products apply at a later date for another STC
to modify any other model included on the type
[[Page 23612]]
certificates of the models on the STC ST12026AT AML, to incorporate the
same novel or unusual design feature, these special conditions would
also apply to that model as well. These special conditions are not
applicable to those models for which applicable special conditions for
rechargeable lithium batteries and battery systems have already been
issued against the type certificate for that specific model.
Conclusion
This action only affects the installation of ELTs that contain non-
rechargeable lithium batteries and battery systems for airplanes listed
on the AML of STC ST12026AT. 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 airplane models listed on the
approved model list of supplemental type certificate no. ST12026AT, as
modified by Delta Flight Products.
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 the 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 the 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 the battery. It also includes vents
(where necessary) and packaging. For the purpose of these special
conditions, a battery and the battery system are referred to as a
battery.
Issued in Kansas City, Missouri, on May 30, 2025.
Patrick R. Mullen,
Manager, Technical Policy Branch, Policy and Standards Division,
Aircraft Certification Service.
[FR Doc. 2025-10180 Filed 6-3-25; 8:45 am]
BILLING CODE 4910-13-P