[Federal Register Volume 89, Number 9 (Friday, January 12, 2024)]
[Rules and Regulations]
[Pages 2126-2127]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-00484]



[[Page 2126]]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-2022-0205; Special Conditions No. 25-844-SC]


Special Conditions: Lufthansa Tecknik AG, Airbus Models A319-133 
and A321-200 Series Airplanes; Supercapacitor Systems and Installation

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions.

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SUMMARY: These special conditions are issued for the Airbus Model A319-
133 and A321-200 series airplanes. These airplanes, as modified by 
Lufthansa Tecknik AG (Lufthansa), 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 the installation of an uninterruptible power supply (UPS) 
system based on supercapacitor technology. The current 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: Effective January 12, 2024.

FOR FURTHER INFORMATION CONTACT: Daniel Poblete, Electrical Systems, 
AIR-626A, Technical Policy Branch, Policy and Standards Division, 
Aircraft Certification Service, Federal Aviation Administration, 3960 
Paramount Blvd., Suite 100, Lakewood, CA 90712-4137; telephone and fax 
(562) 627-5335; email [email protected].

SUPPLEMENTARY INFORMATION:

Background

    On February 17, 2021, Lufthansa applied for a supplemental type 
certificate for the installation of a UPS system in the Model A319-133 
and A321-200 series airplanes. The Airbus Model A319-133 and A321-200 
series airplanes are twin-engine, transport category airplanes. The 
Airbus Model A319-133 airplane has a maximum passenger seating capacity 
of 160, and a maximum takeoff weight of 154,322 pounds. The Airbus 
Model A321-200 airplane has a maximum passenger seating capacity 230, 
and a maximum takeoff weight of 213,848 pounds.

Type Certification Basis

    Under the provisions of title 14, Code of Federal Regulations (14 
CFR) 21.101, Lufthansa must show that the Model A319-133 and A321-200 
series airplanes, as changed, continue to meet the applicable 
provisions of the regulations listed in Type Certificate No. A28NM 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 Airbus Model A319-133 and A321-200 
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 Airbus Model A319-133 and A321-200 series airplanes 
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 Airbus Model A319-133 and A321-200 series airplanes will 
incorporate the following novel or unusual design features:
    This design feature for this installation of a UPS system is based 
on supercapacitor technology.

Discussion

    Currently, there are no regulatory or industry standards for 
supercapacitors and their installation on transport category airplanes. 
Supercapacitors are used to provide power to non-essential cabin 
equipment when the normal power source is interrupted for a short 
period of time. In this design, the supercapacitor UPS system will 
allow connected equipment to be provided back-up power if normal 
electrical power source is interrupted, and remain operational such as 
during power transfers as well as provide transient voltage surge 
suppression should harmful high voltage transients occur. The UPS is 
only used for systems not critical to continued safe flight and 
landing.
    Since the supercapacitor is being used as a high-capacity 
electrical storage device and functions similarly to rechargeable 
batteries, the special conditions used for lithium batteries are 
appropriate for supercapacitor installations and the hazardous 
conditions that could be presented. These special conditions are 
necessary to assist in the testing and installation of this 
supercapacitor on the aircraft.
    Special condition 1 requires that the supercapacitor installation 
be designed to preclude propagation of a thermal event, such as self-
sustained, uncontrolled increases in temperature or pressure. Special 
condition 1 is intended to ensure that the supercapacitor system is 
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 supercapacitor designer. Therefore, other 
special conditions are intended to protect the airplane and its 
occupants if other failures occur.
    Special conditions 2, 6, 8, and 9 are self-explanatory.
    Special condition 3 makes it clear that the flammable fluid fire 
protection requirements of Sec.  25.863 apply to supercapacitor 
installations. Section 25.863 is applicable to areas of the airplane 
that could be exposed to flammable fluid leakage from airplane systems. 
Supercapacitors may contain an electrolyte that is a flammable fluid.
    Special condition 4 requires that each supercapacitor installation 
not damage surrounding structure or adjacent systems, equipment, or 
electrical wiring interconnection system (EWIS) components from 
corrosive fluids or gases that may escape in such a way as to cause a 
hazardous condition.
    While special condition 4 addresses corrosive fluids and gases, 
special condition 5 addresses heat. Special condition 5 requires that 
each supercapacitor installation have provisions to prevent any 
hazardous effect on surrounding structure or adjacent systems, 
equipment, or EWIS components, caused by the maximum amount of heat the 
supercapacitor installation can generate due to any failure of the 
supercapacitor installation or any of the individual supercapacitors. 
The means of meeting special conditions 4 and 5 may be the same, but 
the requirements are independent and address different hazards.

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    Special condition 7 requires that supercapacitor be disconnected or 
otherwise removed from its charging source without the need for crew 
intervention should the supercapacitor become overheated or fail in a 
manner that may create a safety hazard. This requirement applies to all 
supercapacitor installations and is not limited to those whose proper 
functioning is required for the safe operation of the airplane.
    The 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.

Discussion of Comments

    The FAA issued Notice of Proposed Special Conditions No. 25-22-02-
SC for the Airbus Model A319-133 and A321-200 series airplanes, which 
was published in the Federal Register on June 1, 2023 (88 FR 35781). 
The FAA received one comment from The Boeing Company (Boeing).
    Boeing recommended the FAA add a definition of what constitutes a 
supercapacitor and high-capacity electrical storage device and to 
include their thresholds such as capacity, voltage, and dialectic 
strength. Boeing stated that this clarification of supercapacitor 
terminology will avoid any ambiguity and confusion when applying 
special conditions and their applicability, specifically with the 
inapplicability to small capacitors that are used on various electrical 
systems used in electronics.
    The FAA acknowledges Boeing's recommendation that adding a 
definition of what constitutes a supercapacitor is important for 
clarification and to ensure these special conditions' inapplicability 
to small capacitors used in various electrical systems in aviation 
electronics. However, the FAA declines to create a definition for 
supercapacitors through special conditions. Currently, the FAA is not 
aware of an industry standard regarding the design and installation of 
supercapacitors. With no supercapacitor industry standard currently 
available, the similarity of the function of the supercapacitor closely 
relates to the rechargeable lithium batteries. Therefore, the special 
conditions used for lithium batteries are being used for this 
supercapacitor installation. The applicant and the FAA will review the 
design and installation of the supercapacitor to ensure these special 
conditions will apply only to supercapacitors used as energy storage 
devices similar to rechargeable lithium batteries.

Applicability

    As discussed above, these special conditions are applicable to the 
Airbus Model A319-133 and A321-200 series airplanes. Should Lufthansa 
apply at a later date for a change to the supplemental type certificate 
to include another model incorporating the same novel or unusual design 
feature included on Type Certificate No. A28NM, these special 
conditions would apply to that model as well.
    Under standard practice, the effective date of final special 
conditions would be 30 days after the date of publication in the 
Federal Register. However, as the certification date for the Airbus 
Model A319-133 and A321-200 series airplanes is imminent, the FAA finds 
that good cause exists to make these special conditions effective upon 
publication.

Conclusion

    This action affects only a certain novel or unusual design feature 
on Airbus Models A319-133 and A321-200 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), 106(g), 40113, 44701, 44702, 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 Airbus Model A319-133 and A321-200 
series airplanes, as modified by Lufthansa Technik AG. Each 
supercapacitor installation must:
    1. Be designed to preclude the occurrence of uncontrolled increases 
in temperature or pressure under all foreseeable operating and failure 
conditions to prevent fire and explosion.
    2. Not emit explosive or toxic gasses, in normal operation or as 
the result of its failure that may accumulate in hazardous quantities 
in any area of the airplane.
    3. Meet the requirements of Sec.  25.863.
    4. Not damage surrounding structure or adjacent systems, equipment, 
or electrical wiring interconnection system (EWIS) components from 
corrosive fluids or gases that may escape to cause a hazardous 
condition.
    5. Have provisions to prevent any hazardous effect on surrounding 
structure or adjacent systems, equipment, or EWIS components, caused by 
the maximum amount of heat it can generate during any failure including 
any individual supercapacitors.
    6. Have a means to prevent overheating or overcharging of the 
supercapacitor.
    7. Have a means to automatically disconnect it from its charging 
source in the event of an over-temperature condition or failure.
    8. Have a monitoring and alerting feature that alerts the 
flightcrew when the capacity has fallen below acceptable levels if its 
function is required for safe operation of the airplane. The flightcrew 
alerting must be in accordance with the requirements of Sec.  25.1322.
    9. Have a means to prevent insufficient charging if required for 
safe operation of the airplane.

    Note: A supercapacitor installation consists of the 
supercapacitor(s) and any protective, monitoring and alerting 
circuitry or hardware inside or outside of the supercapacitor. This 
includes EWIS components as defined by Sec.  25.1701. It also 
includes any venting or cooling system and packaging. For the 
purpose of these special conditions, a supercapacitor and the 
supercapacitor installation is referred to as a supercapacitor.


    Issued in Kansas City, Missouri, on January 8, 2024.
Patrick R. Mullen,
Manager, Technical Policy Branch, Policy and Standards Division, 
Aircraft Certification Service.
[FR Doc. 2024-00484 Filed 1-11-24; 8:45 am]
BILLING CODE 4910-13-P