Document ID: FAA-2013-0763-0002
Agency: faa
Document Type: Rule
Title: Special Conditions: Learjet Model 35, 35A, 36, and 36A Airplanes; Rechargeable Lithium-Ion Batteries and Battery Systems
Posted Date: 2014-01-09T05:00Z

[Federal Register Volume 79, Number 6 (Thursday, January 9, 2014)]
[Rules and Regulations]
[Pages 1591-1593]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2014-00172]

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

[[Page 1591]]

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 differ 
significantly from those of the nickel-cadmium 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 
Sec.  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 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 or similar novel or unusual design 
feature, the special conditions would also apply to the other model 
under Sec.  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 Sec.  11.38, and they become part of the type-
certification basis under Sec.  21.101.

[[Page 1592]]

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 re-codification of CAR 
4b that established 14 CFR part 25 in February 1965. The new battery 
requirements, Sec.  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 additional rulemaking affecting large transport-category airplanes 
as well as small airplanes. On September 1, 1977 and March 1, 1978, the 
FAA issued Sec.  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 lithium-ion 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 lithium-ion 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 Sec. Sec.  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 the hazards of overcharging 
and over-discharging 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.

0
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 special conditions are issued as part of 
the type-certification 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

[[Page 1593]]

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 lithium-ion batteries and battery 
systems must preclude the occurrence of self-sustaining, 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 Sec.  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 Sec.  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 Sec.  
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 battery systems, which could 
result in short-circuit 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 
Sec.  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 Sec.  
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