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# Rules and Regulations Federal Register 

### 1591

Vol. 79, No. 6

Thursday, January 9, 2014

**DEPARTMENT OF TRANSPORTATION**

**Federal Aviation Administration**

**14 CFR Part 25**

**[Docket No. FAA–2013–0763; Special Conditions No. 25–514–SC]** 

**Special Conditions: Learjet Model 35, 35A, 36, and 36A Airplanes;**  **Rechargeable Lithium-Ion Batteries and Battery Systems** 

**AGENCY :**  Federal Aviation Administration (FAA), DOT.

**ACTION :**  Final special conditions.

**SUMMARY :**  These special conditions are issued for the Learjet Model 35, 35A, 36, and 36A airplanes. These airplanes, as modified by Peregrine, 13000 E. Control Tower Road, Unit K–4, Englewood, CO, 80112, will have a novel or unusual design feature associated with rechargeable lithium-ion batteries and battery systems. These batteries have certain failure, operational, and
maintenance characteristics that differsignificantly from those of the nickelcadmium and lead-acid rechargeable batteries currently approved for installation on large 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 :**  Effective Date: February 10,

2014.

**FOR FURTHER INFORMATION CONTACT :**  Nazih Khaouly, FAA, Airplane and Flight Crew Interface Branch, ANM– 111, Transport Airplane Directorate, Aircraft Certification Service, 1601 Lind Avenue SW., Renton, Washington 98057–3356; telephone 425–227–2432;
facsimile 425–227–1149.

**SUPPLEMENTARY INFORMATION :** 
Background

On June 29, 2012, Peregrine applied for a supplemental type certificate for installing equipment that uses rechargeable lithium-ion battery systems in Learjet Model 35, 35A, 36, and 36A airplanes. The Learjet Model 35, 35A, 36, and 36A airplanes are small transport-category airplanes powered by two turbojet engines, with maximum takeoff weights of up to 18,000 pounds. These airplanes operate with a two-pilot crew and can seat up to eight passengers. The Learjet Model 35, 35A, 36, and 36A airplanes are powered by two Garrett TF731–2–2B engines, and are equipped with an emergency power supply and software-configurable

avionics.

Existing airworthiness regulations did not anticipate the use of lithium-ion batteries and battery systems on aircraft. Lithium-ion batteries and battery systems have new hazards that were not contemplated when the existing regulations were issued. In Title 14, Code of Federal Regulations (14 CFR) 25.1353, the FAA provided an
airworthiness standard for lead-acid
batteries and nickel-cadmium batteries. These special conditions provide an equivalent level of safety as that of the existing regulation. The current regulations are not adequate for rechargeable lithium-battery and battery system installations. Additional lithium-battery and battery system special conditions are required to ensure the same level of safety as set forth by the existing regulation intended for other battery technology.

Type Certification Basis

Under the provisions of 14 CFR 21.17, Peregrine must show that the Learjet Model 35, 35A, 36, and 36A airplanes, as changed, continue to meet the applicable provisions of the regulations incorporated by reference in Type Certificate No. A10CE or the applicable regulations in effect on the date of application for the change. The regulations incorporated by reference in the type certificate are commonly referred to as the ‘‘original type certification basis.’’ The regulations incorporated by reference in Type
Certificate No. A10CE are as follows: Title 14, Code of Federal Regulations part 25, effective February 1, 1965, as amended by Amendments 25–1, 25–2, 25–4, 25–7, 25–18, and § 25.571(d) of Amendment 25–10; Special Conditions set forth in FAA letter to Learjet dated March 1, 1967; Special Conditions No. 25–50–CE–6 dated April 18, 1973, and Amendment 1 dated September 18,

1973. The certification basis for Models 35A and 36A also includes Special

Conditions No. 25–72–CE–8 dated November 3, 1976, and Amendment 1 dated March 14, 1978. The certification basis for Model 35A, in addition to the basis listed above, includes Special Conditions 25–ANM–28 dated May 3, 1989. In addition, the certification basis

includes certain later amended sections of the applicable part 25 regulations that are not relevant to these special

conditions.

If the regulations incorporated by reference do not provide adequate standards regarding the change, the applicant must comply with certain regulations in effect on the date of application for the change.

If the Administrator finds that the applicable airworthiness regulations (i.e., 14 CFR part 25) do not contain adequate or appropriate safety standards for the Learjet Model 35, 35A, 36, and 36A airplanes 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 or similar novel or unusual design feature, the special conditions would also apply to the other model under § 21.101.

In addition to the applicable airworthiness regulations and special conditions, the Learjet Model 35, 35A, 36, and 36A 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 § 11.38, and they become part of the type-certification basis under § 21.101.


### 1592 Federal Register / Vol. 79, No. 6 / Thursday, January 9, 2014 / Rules and Regulations

Novel or Unusual Design Features

The Learjet Model 35, 35A, 36, and 36A airplanes will incorporate the following novel or unusual design
features: A Mid-Continent MD835–5 Emergency Power Supply that uses a rechargeable lithium-ion battery and battery system. Lithium-ion batteries and battery systems have certain failure, operational, and maintenance characteristics that differ significantly
from those of the nickel-cadmium and lead-acid rechargeable batteries. Rechargeable lithium-ion batteries and battery systems are considered to be a novel or unusual design feature in transport-category airplanes, with respect to the requirements in 14 CFR

25.1353.

Discussion

The current regulations governing installation of batteries in large transport-category airplanes were derived from Civil Air Regulations(CAR) part 4b.625(d) as part of the recodification of CAR 4b that established 14 CFR part 25 in February 1965. The new battery requirements, § 25.1353(c)(1) through (c)(4), basically reworded the CAR requirements.

Increased use of nickel-cadmium batteries in small airplanes resulted in increased incidents of battery fires and
failures which led to additionalrulemaking affecting large transportcategory airplanes as well as small airplanes. On September 1, 1977 and March 1, 1978, the FAA issued § 25.1353(c)(5) and (c)(6), respectively, governing nickel-cadmium battery installations on large transport-category airplanes.

The proposed use of lithium-ion batteries and battery systems for equipment and systems on the Learjet Model 35, 35A, 36, and 36A airplanes has prompted the FAA to review the adequacy of these existing regulations. Our review indicates that the existing regulations do not adequately address several failure, operational, and
maintenance characteristics of lithiumion batteries and battery systems that could affect the safety and reliability of the MD835–5 Emergency Power Supply
installations.

At present, commercial aviation has limited experience with use of rechargeable lithium-ion batteries and battery systems in applications involving commercial aviation. However, other users of this technology, ranging from wireless telephone
manufacturers to the electric-vehicle industry, have noted potential hazards with lithium-ion batteries and battery systems. These problems include overcharging, over-discharging, and flammability of cell components.

1. Overcharging

In general, lithium-ion batteries and battery systems 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. This condition is especially true for overcharging, which causes heating and destabilization of the components of the cell, leading to the formation (by plating) of highly unstable
metallic lithium. The metallic lithium can ignite, resulting in a self-sustaining fire or explosion. Finally, the severity of thermal runaway, due to overcharging, increases with increasing battery capacity due to the higher amount of electrolyte in large batteries.

2. Over-Discharging

Discharge of some types of lithiumion batteries and battery systems, beyond a certain voltage (typically 2.4 volts), can cause corrosion of the electrodes of the cell, resulting in loss of battery capacity that cannot be reversed by recharging. This loss of capacity may not be detected by the simple voltage measurements commonly available to flightcrews as a means of checking battery status—a problem shared with nickel-cadmium
batteries.

3. Flammability of Cell Components

Unlike nickel-cadmium and lead-acid batteries, some types of lithium-ion batteries and battery systems use liquid electrolytes that are flammable. The electrolyte can serve as a source of fuel for an external fire, if there is a breach of the battery container.

The problems lithium-ion battery and battery-system users experience raise
concern about the use of these batteries
in commercial aviation. The intent of the special conditions is to establish appropriate airworthiness standards for lithium-ion battery installations in the Learjet Model 35, 35A, 36, and 36A airplanes and to ensure, as required by §§ 25.1309 and 25.601, that these lithium-ion batteries and battery systems are not hazardous or unreliable. To address these concerns, these special conditions adopt the following requirements:

• Those sections of 14 CFR 25.1353 that are applicable to lithium-ion
batteries.

• The flammable fluid fire protection requirements of 14 CFR 25.863. In the past, this rule was not applied to batteries of transport category airplanes, since the electrolytes used in lead-acid and nickel-cadmium batteries are not
flammable.

• New requirements to address thehazards of overcharging and overdischarging that are unique to lithium
ion batteries.

• New maintenance requirements to ensure that batteries used as spares are maintained in an appropriate state of charge.

These special conditions are similar to lithium-ion batteries and battery systems special conditions adopted for numerous other aircraft, including Boeing Model 787 (72FR57842; October 11, 2007).

Discussion of Comments

Notice of proposed special conditions no. 25–13–07–SC for the Peregrine modifications to the Learjet Model 35, 35A, 36, and 36A airplanes was published in the Federal Register on October 22, 2013 (78 FR 62495). No comments were received, and the special conditions are adopted as proposed.

Applicability

As discussed above, these special conditions are applicable to the Learjet Model 35, 35A, 36, and 36A airplanes. Should Peregrine apply at a later date for a supplemental type certificate to modify any other model included on Type Certificate No. A10CE, to incorporate the same novel or unusual design feature, the special conditions would apply to that model as well.

Conclusion

This action affects only certain novel or unusual design features on the Learjet Model 35, 35A, 36, and 36A airplanes. It is not a rule of general applicability and it 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.

■ The authority citation for these special conditions is as follows:

Authority: 49 U.S.C. 106(g), 40113, 44701,

44702, 44704.

The Special Conditions

Accordingly, pursuant to the authority delegated to me by the Administrator, the following specialconditions are issued as part of the typecertification basis for the Learjet Model 35, 35A, 36, and 36A airplanes modified by Peregrine.

These special conditions require that (1) all characteristics of the rechargeable lithium-ion batteries and battery systems, and their installation, that


### 1593 Federal Register / Vol. 79, No. 6 / Thursday, January 9, 2014 / Rules and Regulations

could affect safe operation of the Learjet Model 35, 35A, 36, and 36A airplanes, are addressed, and (2) appropriate
Instructions for Continued Airworthiness, which include maintenance requirements, are established to ensure the availability of electrical power, when needed, from the
batteries.

In lieu of the requirements of 14 CFR 25.1353(b)(1) through (b)(4) at Amendment 25–113, the following special conditions apply. Rechargeable lithium-ion batteries and battery systems on Learjet Model 35, 35A, 36, and 36A airplanes must be designed and
installed as follows:

1. Safe cell temperatures and pressures must be maintained during any foreseeable charging or discharging condition, and during any failure of the charging or battery monitoring system not shown to be extremely remote. The rechargeable lithium-ion batteries and battery systems must preclude explosion in the event of those failures.

2. Design of the rechargeable lithiumion batteries and battery systems mustpreclude the occurrence of selfsustaining, uncontrolled increases in
temperature or pressure.

3. No explosive or toxic gases emitted by any rechargeable lithium-ion batteries and battery systems in normal operation, or as the result of any failure of the battery charging system, monitoring system, or battery
installation that is not shown to be extremely remote, may accumulate in hazardous quantities within the airplane.

4. Installations of rechargeable lithium-ion batteries and battery systems must meet the requirements of § 25.863(a) through (d).

5. No corrosive fluids or gases that may escape from any lithium-ion batteries and battery systems may damage surrounding structure or any adjacent systems, equipment, or electrical wiring of the airplane in such a way as to cause a major or more severe failure condition, in accordance with § 25.1309 (b) and applicable regulatory guidance.

6. Each lithium-ion battery and battery system must have provisions to prevent any hazardous effect on structure or essential systems caused by
the maximum amount of heat the battery can generate during a short circuit of the battery or of its individual
cells.

7. Rechargeable lithium-ion batteries and battery systems must have a system to automatically control the charging rate of the battery, so as to prevent battery overheating or overcharging,
and: i. A battery-temperature sensing and over-temperature warning system with a means for automatically disconnecting the battery from its charging source in the event of an over-temperature condition, or,

ii. A battery-failure sensing and warning system with a means for automatically disconnecting the battery from its charging source in the event of battery failure.

8. Any rechargeable lithium-ion batteries and battery systems, the function of which are required for safe operation of the airplane, must incorporate a monitoring and warning feature that will provide an indication to the appropriate flight crewmembers whenever the state-of-charge of the
batteries has fallen below levels considered acceptable for dispatch of the airplane.

9. The Instructions for Continued Airworthiness required by § 25.1529 must contain maintenance requirements
to assure that the lithium-ion batteries are sufficiently charged at appropriate intervals specified by the battery manufacturer and the equipment manufacturer of the rechargeable lithium-ion battery or rechargeable lithium-ion battery system. This is required to ensure that rechargeable lithium-ion batteries and battery systems will not degrade below specified ampere-hour levels sufficient to power the aircraft system, for intended applications. The Instructions
for Continued Airworthiness must also contain procedures for the maintenance of batteries in spares storage to prevent the replacement of batteries with batteries that have experienced degraded charge-retention ability or other damage due to prolonged storage at a low state of charge. Replacement
batteries must be of the same manufacturer and part number as approved by the FAA. Precautions
should be included in the Instructions
for Continued Airworthiness maintenance instructions to prevent mishandling of the rechargeable lithium-ion batteries and batterysystems, which could result in shortcircuit or other unintentional impact damage caused by dropping or other
destructive means.

Note 1: The term ‘‘sufficiently charged’’’ means that the battery will retain enough of a charge, expressed in ampere-hours, to ensure that the battery cells will not be damaged. A battery cell may be damaged by lowering the charge below a point where the battery experiences a reduction in the ability to charge and retain a full charge. This reduction would be greater than the reduction that may result from normal operational degradation. Note 2: These special conditions are not intended to replace § 25.1353(b) at

Amendment 25–113 in the certification basis for Learjet Model 35, 35A, 36, and 36A airplanes. These special conditions apply only to rechargeable lithium-ion batteries and battery systems and their installations. The requirements of § 25.1353(b) at Amendment

25–113 remain in effect for batteries and battery installations on Learjet Model 35, 35A, 36, and 36A airplanes that do not use rechargeable lithium-ion batteries.

Issued in Renton, Washington, on December 31, 2013.
Angelos Xidias,
Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.

[FR Doc. 2014–00172 Filed 1–8–14; 8:45 am]

**BILLING CODE 4910–13–P**

**ENVIRONMENTAL PROTECTION**
**AGENCY**

**40 CFR Part 52**

**[EPA–R04–OAR–2013–0440; FRL–9905–13– Region 4]** 

**Approval and Promulgation of Implementation Plans; Tennessee;**  **Bristol; 2010 Lead Base Year Emissions Inventory and Conversion**  **of Conditional Approvals for Prevention of Significant Deterioration** 

**AGENCY :**  Environmental Protection Agency (EPA).

**ACTION :**  Final rule.

**SUMMARY :**  The Environmental Protection Agency (EPA) is approving the Lead 2010 base year emissions inventory State Implementation Plan (SIP) revision submitted by the State of Tennessee, through the Tennessee Department of Environment and Conservation (TDEC) on April 11, 2013. The emissions inventory was submitted to meet the requirements of the Clean Air Act (CAA or Act) for the Bristol
2008 Lead National Ambient Air Quality Standards (NAAQS) nonattainment area (hereafter also
referred to as the ‘‘Bristol Area’’ or ‘‘Area’’). Additionally, EPA is converting conditional approvals to full approvals for Tennessee’s 1997 annual fine particulate matter (PM2.5 ) NAAQS,
2006 24-hour PM 2.5 NAAQS and 2008 8- hour ozone NAAQS infrastructure SIPs as they relate to adequate provisions prohibiting emissions that interfere with any other State’s required measures to prevent significant deterioration of its air quality. EPA conditionally approved these portions of Tennessee’s infrastructure SIPs for these NAAQS on March 6, 2013, and March 26, 2013. Tennessee has since met the obligations