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###### Department of Transportation

###### Federal Aviation Administration

          - 14 CFR Part 25
          - [Docket No. FAA-2022-0277; Special Conditions No. 25-814-SC]

# AGENCY:

Federal Aviation Administration (FAA), DOT.

# ACTION:

Final special conditions; request for comments.

# SUMMARY:

These special conditions are issued for the Textron Aviation (Textron) Model 400A airplane. This airplane, as modified by Peregrine, 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 lithum 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 Peregrine on April 6, 2022. Send comments on or before May 23, 2022.

# ADDRESSES:

Send comments identified by Docket No. FAA-2022-0277 using any of the following methods:
      -  Federal eRegulations Portal:                          Go to                          https://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.                    

*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                         *https://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. Submissions containing CBI should be sent to Nazih Khaouly, Aircraft Systems, AIR-623, 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.*                         Comments the FAA receives, which are not specifically designated as CBI, will be placed in the public docket for these special conditions.                    

*Docket:*                         Background documents or comments received may be read at                         *https://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-623, 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 § 11.38(b), that new comments are unlikely, and notice and comment prior to this publication are unnecessary.                

## 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 November 30, 2021, Peregrine applied for a supplemental type certificate for the installation of a True Blue Power TB40 main ship rechargeable lithium battery in the Model 400A airplane. The Textron Model 400A airplane is a twin-engine transport category business jet, with a maxium passenger capacity of 11, and                           ( print page 19790)                        has a maximum takeoff weight of 16,300 pounds.                

## Type Certification Basis

Under the provisions of title 14, Code of Federal Regulations (14 CFR) 21.101, Peregrine must show that the Model 400A airplane, as changed, continues to meet the applicable provisions of the regulations listed in Type Certificate No. A16SW 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 Peregrine Model 400A airplane because of a novel or unusual design feature, special conditions are prescribed under the provisions of § 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 § 21.101.

In addition to the applicable airworthiness regulations and special conditions, the Textron Model 400A airplane 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 § 11.38, and they become part of the type certification basis under § 21.101.

## Novel or Unusual Design Features

The Textron Model 400A airplane will incorporate the following novel or unusual design features:

Installation of True Blue Power TB40 main ship rechargeable lithium battery.

## Discussion

Rechargeable lithium batteries are considered to be a novel or unusual design feature in transport category airplanes, with respect to the requirements in § 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 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 be designed to maintain safe temperatures and pressures. Special Condition 2 addresses these same issues but for the entire battery. Special Condition 2 requires that the battery 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 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 § 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 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 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 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 battery installations in lieu of § 25.1353(b)(1) through (4) at Amendment 25-123 or § 25.1353(c)(1) through (4) at earlier amendments. Those regulations 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 Textron Model 400A airplane. Should Peregrine apply at a later date for a supplemental type certificate to modify any other model included on Type Certificate No. A16SW 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 this feature 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 Textron Aviation Model 400A airplanes, as modified by Peregrine.

In lieu of § 25.1353(b)(1) through (4) at amendment 25-123, or § 25.1353(c)(1) through (4) at earlier amendments, each 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, and automatically control 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                           ( print page 19791)                        of its failure that may accumulate in hazardous quantities within the airplane.                

4. Meet the requirements of § 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 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 these special conditions, a battery and the battery system is referred to as a battery.

Issued in Kansas City, Missouri, on April 1, 2022.

Patrick R. Mullen,

Manager, Technical Innovation Policy Branch, Policy and Innovation Division, Aircraft Certification Service.

[FR Doc. 2022-07255 Filed 4-5-22; 8:45 am]

BILLING CODE 4910-13-P