Special Conditions: ALOFT AeroArchitects, Gulfstream Aerospace Corporation Model G-IV, GIV-X, GV, and GV-SP Airplanes; Rechargeable Lithium Batteries and Battery System Installations

[Federal Register Volume 91, Number 73 (Thursday, April 16, 2026)]
[Rules and Regulations]
[Pages 20317-20319]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2026-07483]



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Rules and Regulations
                                                Federal Register
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This section of the FEDERAL REGISTER contains regulatory documents 
having general applicability and legal effect, most of which are keyed 
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under 50 titles pursuant to 44 U.S.C. 1510.

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Federal Register / Vol. 91, No. 73 / Thursday, April 16, 2026 / Rules 
and Regulations

[[Page 20317]]



DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-2026-3490; Special Conditions No. 25-888-SC]


Special Conditions: ALOFT AeroArchitects, Gulfstream Aerospace 
Corporation Model G-IV, GIV-X, GV, and GV-SP Airplanes; 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 the Gulfstream 
Aerospace Corporation (Gulfstream) Model G-IV, GIV-X, GV, and GV-SP 
series airplanes, as modified by ALOFT AeroArchitects (ALOFT). These 
airplanes 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 a main ship 
rechargeable lithium battery. 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 ALOFT on April 16, 2026. Send 
comments on or before June 1, 2026.

ADDRESSES: Send comments identified by Docket No. FAA-2026-3490 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.
    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 23, 2026, ALOFT applied for a supplemental type 
certificate for the installation of rechargeable lithium batteries and 
battery systems in the Gulfstream Model G-IV, GIV-X, GV, and GV-SP 
series airplanes. These airplanes, approved under Type Certificate No. 
A12EA, are twin-engine transport category airplanes with a maximum 
seating capacity of 19 passengers. These airplanes have a maximum 
takeoff weight between 46,500 and 91,400 pounds, depending on the 
model.

Type Certification Basis

    Under the provisions of title 14, Code of Federal Regulations (14 
CFR) 21.101, ALOFT must show that the Gulfstream Model G-IV, GIV-X, GV, 
and GV-SP

[[Page 20318]]

series airplanes, as changed, continue to meet the applicable 
provisions of the regulations listed in Type Certificate No. A12EA 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 Gulfstream Model G-IV, GIV-X, GV, 
and GV-SP series 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 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 Gulfstream Model G-IV, GIV-X, GV, and GV-SP series 
airplanes must comply with 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 Gulfstream Model G-IV, GIV-X, GV, and GV-SP series airplanes, 
as modified by ALOFT, will incorporate the following novel or unusual 
design features:
    Installation of a main ship rechargeable lithium battery.

Discussion

    Rechargeable lithium batteries and battery systems are considered 
to be a novel or unusual design feature in transport category 
airplanes, with respect to the requirements in Sec.  25.1353. This type 
of battery has certain failure, operational, and maintenance 
characteristics that differ significantly from those of the nickel-
cadmium and lead-acid rechargeable batteries currently approved for 
installation on transport category airplanes. These 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 
introduces failure modes that require unique design considerations, 
such as provisions for thermal management.
    Special Condition 1 requires that each individual cell within a 
battery and battery system be designed to maintain safe temperatures 
and pressures. Special Condition 2 addresses these same issues but for 
the entire battery system.
    Special Condition 2 requires that the batteries and battery system 
be designed to prevent propagation of a thermal event, such as self-
sustained, uncontrolled increases in temperature or pressure from one 
cell to adjacent cells.
    Special Conditions 1 and 2 are intended to ensure that the cells 
and battery system 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 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 clarifies that the flammable-fluid fire-
protection requirements of Sec.  25.863 apply to 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. Rechargeable lithium batteries contain electrolyte that is a 
flammable fluid.
    Special Condition 5 requires each rechargeable lithium battery and 
battery system installation to 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.
    Special Condition 6 requires each rechargeable lithium battery and 
battery system installation to 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. 
The means of meeting special conditions 5 and 6 may be the same, but 
they are independent requirements addressing different hazards. Special 
Condition 5 addresses corrosive fluids and gases, whereas special 
condition 6 addresses heat.
    Special Condition 9 requires rechargeable lithium batteries and 
battery systems to have ``automatic'' means, for charge rate and 
disconnect, due to the fast acting nature of lithium battery chemical 
reactions. Manual intervention would not be timely or effective in 
mitigating the hazards associated with these batteries.
    These special conditions apply to all rechargeable lithium 
batteries and battery system installations 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. Those regulations will remain in 
effect for other battery installations on these airplanes.
    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 
Gulfstream Model G-IV, GIV-X, GV, and GV-SP series airplanes, as 
modified by ALOFT. Should ALOFT apply at a later date for a 
supplemental type certificate to modify any other model included on 
Type Certificate No. A12EA to incorporate the same novel or unusual 
design feature, these special conditions would apply to that model as 
well.

Conclusion

    This action affects only certain novel or unusual design features 
on the Gulfstream Model G-IV, GIV-X, GV, and GV-SP 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 Gulfstream Model G-IV, GIV-X, GV, and 
GV-SP series airplanes, as modified by ALOFT.
    In lieu of Title 14, Code of Federal Regulations (14 CFR) 
25.1353(b)(1) through (4) at amendment 25-123 or Sec.  25.1353(c)(1) 
through (4) at earlier amendments, each rechargeable lithium battery 
installation must:
    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, and automatically 
control

[[Page 20319]]

the charge rate of each cell to protect against adverse operating 
conditions, such as cell imbalance, back charging, overcharging, and 
overheating.
    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 monitoring and warning feature that alerts the flightcrew 
when its charge state falls below acceptable levels if its function is 
required for safe operation of the airplane.
    9. Have a means to automatically disconnect from its charging 
source in the event of an over-temperature condition, cell failure or 
battery failure.

    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 this special condition, 
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. 2026-07483 Filed 4-15-26; 8:45 am]
BILLING CODE 4910-13-P