[Federal Register Volume 89, Number 95 (Wednesday, May 15, 2024)]
[Rules and Regulations]
[Pages 42341-42343]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-10611]



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 Rules and Regulations
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  Federal Register / Vol. 89, No. 95 / Wednesday, May 15, 2024 / Rules 
and Regulations  

[[Page 42341]]



DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-2023-2134; Special Conditions No. 25-845-SC]


Special Conditions: H4 Aerospace (UK) Ltd., Boeing Model 757-200 
Airplane, Non-Rechargeable Lithium Battery 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 non-rechargeable 
lithium batteries and battery systems on Boeing Model 757-200 
airplanes, as modified by H4 Aerospace (UK) Ltd (H4). Non-rechargeable 
lithium batteries are a novel or unusual design feature when compared 
to the state of technology envisioned in the airworthiness standards 
for transport category airplanes. 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 H4 on May 15, 2024. Send comments on 
or before July 1, 2024.

ADDRESSES: Send comments identified by Docket No. FAA-2023-2134 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 
Unit, AIR-626A, Technical Policy Branch, Policy and Standards Division, 
Aircraft Certification Service, Federal Aviation Administration, 2200 
South 216th Street, Des Moines, Washington 98198; telephone (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 Title 14, Code of Federal 
Regulations (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 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 proposed 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 and will consider comments filed late if it is possible to do 
so without incurring delay. The FAA may change these special conditions 
based on the comments received.

Background

    On February 26, 2020, H4 applied for a supplemental type 
certificate to install, on the Boeing 757-200 airplane, HR Smith 
emergency locator transmitter (ELT) 500-32-2Y-H that contain a non-
rechargeable lithium battery and battery system. The Boeing Model 757-
200 airplane currently approved under Type Certificate No A2NM, are 
twin-engine transport category airplanes with a maximum seating of 
capacity of 295 passengers and has a maximum takeoff weight of 255,000 
pounds.

Type Certification Basis

    Under the provisions of title 14, Code of Federal Regulations (14 
CFR) 21.101, H4 must show that the Boeing Model 757-200 airplane, as 
changed, continues to meet the applicable provisions of the regulations 
listed in Type Certificate No. A2NM or the applicable regulations in

[[Page 42342]]

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 airplane 
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 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 airplane must comply with the 
exhaust-emission requirements of 14 CFR part 34, and the noise-
certification requirements of 14 CFR part 36.

Novel or Unusual Design Feature

    The Boeing Model 757-200, MSN 25140 and MSN 24473 airplanes will 
incorporate the following novel or unusual design feature:
    The installation of an HR Smith emergency locator transmitter (ELT) 
500-32-2Y-H containing a non-rechargeable lithium battery and battery 
system.

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 that 
established 14 CFR part 25 in February 1965. This recodification 
basically reworded the CAR 4b battery requirements, which are currently 
in Sec.  25.1353(b)(1) through (4). Non-rechargeable lithium batteries 
are novel and unusual with respect to the state of technology 
considered when these requirements were codified. Non-rechargeable 
lithium batteries 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 batteries revealed unanticipated failure modes. A National 
Transportation Safety Board (NTSB) 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 emergency-locator transmitter 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 S5-2013_ET-AOP.pdf, available in the docket for these 
special conditions.
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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 
special conditions to design changes on other airplane makes and models 
applied for after this same date.
    Some known uses of rechargeable and non-rechargeable lithium 
batteries on airplanes include:
     Flight deck and avionics systems such as displays, global 
positioning systems, cockpit voice recorders, flight data recorders, 
underwater locator beacons, navigation computers, integrated avionics 
computers, satellite network and communication systems, communication 
management units, and remote-monitor electronic line-replaceable units;
     Cabin safety, entertainment, and communications equipment, 
including emergency locator transmitters, life rafts, escape slides, 
seatbelt air bags, cabin management systems, Ethernet switches, routers 
and media servers, wireless systems, internet and in-flight 
entertainment systems, satellite televisions, remotes, and handsets;
     Systems in cargo areas including door controls, sensors, 
video surveillance equipment, and security systems.
    Some known potential hazards and failure modes associated with non-
rechargeable lithium batteries are:
     Internal failures: In general, these batteries are 
significantly more susceptible to internal failures that can result in 
self-sustaining increases in temperature and pressure (i.e., thermal 
runaway) than their nickel-cadmium or lead-acid counterparts. The 
metallic lithium can ignite, resulting in a self-sustaining fire or 
explosion.
     Fast or imbalanced discharging: Fast discharging or an 
imbalanced discharge of one cell of a multi-cell battery may create an 
overheating condition that results in an uncontrollable venting 
condition, which in turn leads to a thermal event or an explosion.
     Flammability: Unlike nickel-cadmium and lead-acid 
batteries, lithium batteries use higher energy and current in an 
electrochemical system that can be configured to maximize energy 
storage of lithium. They also use liquid electrolytes that can be 
extremely flammable. The electrolyte, as well as the electrodes, can 
serve as a source of fuel for an external fire if the battery casing is 
breached. For the purpose of these special conditions, a battery and 
the battery system are referred to as a battery. A battery system 
consists of the battery and any protective, monitoring, and alerting 
circuitry or hardware inside or outside of the battery. It also 
includes vents (where necessary) and packaging.
    Special condition no. 1 of these special conditions requires that 
each individual cell within a non-rechargeable lithium battery 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 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 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 contain an 
electrolyte that is a flammable fluid.

[[Page 42343]]

    Special condition no. 5 requires that each non-rechargeable lithium 
battery 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 no. 5 addresses corrosive fluids and gases, 
special condition no. 6 addresses heat. Special condition no. 6 
requires that each non-rechargeable lithium battery 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 installations in lieu of Sec.  25.1353(b)(1) through (4) at 
Amendment 25-123 on Boeing Model 757-200 airplanes, as modified by H4 
and described in this application. 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 airplanes. Should H4 apply at a later date for a 
supplemental type certificate to modify any other model included on 
Type Certificate No. FAA STC ST00102IB 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 one model of airplane. 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), 106(g), 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 Boeing Model 757-200 airplanes, as 
modified by H4 Aerospace (UK) Ltd.
    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 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 
flightcrew if 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, 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 are referred to as a battery.


    Issued in Kansas City, Missouri, on May 7, 2024.
Patrick R. Mullen,
Manager, Technical Innovation Policy Branch, Policy and Innovation 
Division, Aircraft Certification Service.
[FR Doc. 2024-10611 Filed 5-14-24; 8:45 am]
BILLING CODE 4910-13-P