[Federal Register Volume 76, Number 180 (Friday, September 16, 2011)]
[Rules and Regulations]
[Pages 57627-57629]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2011-23718]



Federal Aviation Administration

14 CFR Part 25

[Docket No. NM462; Special Condition No. 25-444-SC]

Special Conditions: Cessna Aircraft Company Model M680 Airplane; 
Rechargeable Lithium-Ion Battery Installations

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions.


SUMMARY: These special conditions are issued for the Cessna Aircraft 
Company Model 680 airplane. This airplane will have a novel or unusual 
design feature associated with lithium-ion batteries. 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: October 17, 2011.

FOR FURTHER INFORMATION CONTACT: Nazih Khaouly, FAA, Airplane & 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-


[[Page 57628]]


    On October 3, 2006, Cessna Aircraft Company applied for a change to 
type certification (TC) T00012WI for installation of lithium-ion 
batteries in the Model 680.

Type Certification Basis

    Under the provisions of Title 14, Code of Federal Regulations (14 
CFR) 21.101, Cessna Aircraft Company must show that the Model 680, as 
changed, continues to meet the applicable provisions of the regulations 
incorporated by reference in TC T00012WI 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 TC T00012WI are as follows:
    Title 14, Code of Federal Regulations, part 25, effective February 
1, 1965, as amended by amendments 25-1 through 25-98. Refer to TC 
T00012WI, as applicable, for a complete description of the type-
certification basis for this model, including special conditions and 
exemptions that are not relevant to these special conditions.
    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 Model 680 because of a novel or 
unusual design feature, special conditions are prescribed under the 
provisions of 14 CFR 21.16.
    Special conditions are initially applicable to the model for which 
they are issued. Should the type certificate for that model be amended 
later to include any other model that incorporates the same or similar 
novel or unusual design feature, or should any other model already 
included on the same type certificate be modified 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 Model 680 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 14 CFR 21.101.

Novel or Unusual Design Features

    The Model 680 will incorporate the following novel or unusual 
design features:
    Cessna Aircraft Company proposes to use rechargeable lithium-ion 
main batteries and Auxiliary Power Unit (APU) start batteries on the 
Model 680, and is also considering the use of this lithium-battery 
technology in several other auxiliary-battery applications in these 
airplanes. This type of battery possesses certain failure and 
operational characteristics, and maintenance requirements differ 
significantly from that of the nickel-cadmium (Ni-Cd) and lead-acid 
rechargeable batteries currently approved for installation in 
transport-category airplanes. Large, high-capacity, rechargeable 
lithium batteries are a novel or unusual design feature in transport-
category airplanes, and current regulations in 14 CFR part 25 do not 
address installation of rechargeable lithium batteries.


    The current regulations governing the installation of batteries in 
transport-category airplanes were derived from Civil Air Regulation 
(CAR) 4b.625(d) as part of the re-codification of CAR 4b that 
established Federal aviation regulations, in 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 Ni-Cd batteries in small airplanes resulted in 
increased frequency of battery fires and failures, which led to 
additional rulemaking affecting 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, which govern Ni-Cd 
battery installations on transport-category airplanes.
    The proposed use of rechargeable lithium batteries for equipment 
and systems on the Model 680 airplane has prompted the FAA to review 
the adequacy of existing battery regulations. Our review indicates that 
the existing regulations do not adequately address several failure, 
operational, and maintenance characteristics of lithium batteries that 
could affect the safety and reliability of rechargeable lithium-battery 
installations on the Model 680 airplane.
    The use of lithium rechargeable batteries in applications involving 
commercial aviation has limited history. However, other users of this 
technology, ranging from wireless-telephone manufacturers to the 
electric-vehicle industry, have noted safety problems with lithium 
batteries. These problems include overcharging, over-discharging, and 
lithium-battery cell-component flammability.

1. Overcharging

    In general, lithium-ion batteries are significantly more 
susceptible than their Ni-Cd or lead-acid counterparts to internal 
failures that can result in self-sustaining increases in temperature 
and pressure (i.e., thermal runaway). This is especially true for 
overcharging, which causes heating and destabilization of the 
components of the lithium-battery cell, which can lead to the 
formation, by plating, of highly unstable metallic lithium. The 
metallic lithium can ignite, resulting in a self-sustaining fire or 
explosion. The severity of thermal runaway due to overcharging 
increases with increased battery capacity due to the higher amount of 
electrolyte in large batteries.

2. Over-Discharging

    Discharge of some versions of the lithium-battery cell, beyond a 
certain voltage (typically 2.4 volts), can cause corrosion of the 
electrodes in 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 
flight crewmembers as a means of checking battery status, a problem 
shared with Ni-Cd batteries.

3. Flammability of Cell Components

    Unlike Ni-Cd and lead-acid cells, some types of lithium-battery 
cells use flammable liquid electrolytes. The electrolyte can serve as a 
source of fuel for an external fire if the cell container is breached.
    The problems that lithium-battery users experience raise concerns 
about the use of these batteries in commercial aviation. The intent of 
these special conditions is to establish appropriate airworthiness 
standards for lithium-battery installations in the Model 680 airplane, 
and to ensure, as required by Sec. Sec.  25.601 and 25.1309, that these 
battery installations will not result in an unsafe condition.
    To address these concerns, these special conditions adopt the 
following requirements:
     Those sections of Sec.  25.1353 that are applicable to 
lithium batteries.
     The flammable-fluid fire-protection requirements of Sec.  
25.863. In the past, this rule was not applied to batteries in 
transport-category airplanes because the electrolytes in lead-acid and 
Ni-Cd batteries are not considered flammable.

[[Page 57629]]

     New requirements to address hazards of overcharging and 
over-discharging that are unique to rechargeable lithium-ion batteries.
     Section 25.1529, Instructions for Continued Airworthiness, 
must include maintenance requirements to ensure that batteries used as 
spares are maintained in an appropriate state of charge, and installed 
lithium batteries are sufficiently charged at appropriate intervals. 
These instructions must also describe proper repairs, if allowed, and 
battery part-number configuration control.
    In issuing these special conditions, the FAA requires that:
    (1) All characteristics of the lithium batteries and their 
installation that could affect safe operation of the Cessna Model 680 
airplane are addressed, and
    (2) Appropriate Instructions for Continued Airworthiness, which 
include maintenance requirements, are established to ensure the 
availability of electrical power from the batteries when needed.

Discussion of Comments

    Notice of proposed special conditions no. 25-11-15-SC for the Model 
680 airplane was published in the Federal Register on July 1, 2011 (76 
FR 41142). No comments were received, and the special conditions are 
adopted as proposed.


    As discussed above, these special conditions are applicable to the 
Model 680 airplane. Should Cessna Aircraft Company apply at a later 
date for a change to the type certificate to include another model 
incorporating the same novel or unusual design feature, the special 
conditions would apply to that model as well.


    This action affects only certain novel or unusual design features 
on the Cessna Model 680 airplane. It is not a rule of general 

List of Subjects in 14 CFR Part 25

    Aircraft, Aviation safety, Reporting and recordkeeping 

    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 part of the type-
certification basis for Cessna Aircraft Company Model 680 airplanes.
    In lieu of the requirements of Sec.  25.1353(c)(1) through (c)(4) 
at amendment 25-42, lithium-ion batteries and battery installations on 
the Cessna Model 680 airplane must be designed and installed as 
    (1) Safe lithium-ion battery-cell temperatures and pressures must 
be maintained during any charging or discharging condition, and during 
any failure of the battery-charging or battery-monitoring system not 
shown to be extremely remote. The lithium-battery installation must 
preclude explosion in the event of those failures.
    (2) Design of lithium batteries must preclude the occurrence of 
self-sustaining, uncontrolled increases in temperature or pressure.
    (3) No explosive or toxic gases emitted by any lithium battery in 
normal operation, or as the result of any failure of the battery-
charging or battery-monitoring system, or battery installation which is 
not shown to be extremely remote, may accumulate in hazardous 
quantities within the airplane.
    (4) Installations of lithium batteries must meet the requirements 
of 14 CFR 25.863(a) through (d).
    (5) No corrosive fluids or gases that may escape from any lithium 
battery 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, as determined in 
accordance with 14 CFR 25.1309(b).
    (6) Each lithium-battery installation 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) Lithium-battery installations must have a system to control 
automatically the charging rate of the battery to prevent battery 
overheating or overcharging, and
    (i) A battery-temperature-sensing and over-temperature-warning 
system with a means to automatically disconnect 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 to 
automatically disconnect the battery from its charging source in the 
event of battery failure.
    (8) Any lithium-battery installation, the function of which is 
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 (and Sec.  26.11) must contain maintenance steps to assure that 
the lithium batteries are sufficiently charged at appropriate intervals 
specified by the battery manufacturer. The instructions for continued 
airworthiness must also contain procedures to ensure the integrity of 
lithium batteries in spares storage to prevent the replacement of 
batteries, the function of which are required for safe operation of the 
airplane, with batteries that have experienced degraded charge-
retention ability or other damage due to prolonged storage at a low 
state-of-charge. Precautions should be included in the continued-
airworthiness maintenance instructions to prevent mishandling of 
lithium batteries, which could result in a short circuit or other 
unintentional damage that could result in personal injury or property 

    Note 1:  The term ``sufficiently charged'' means that the 
battery retains enough of a charge, expressed in ampere-hours, to 
ensure that the battery cells are not damaged. A battery cell may be 
damaged by reducing the battery's charge below a point where the 
battery's ability to charge and retain a full charge is reduced. 
This reduced charging and charge-retention capability would be 
greater than the reduction that may result from normal operational 

    Note 2:  These special conditions are not intended to replace 
Sec.  25.1353(c) in the certification basis of the Cessna Model 680 
airplane. These special conditions apply only to lithium-ion 
batteries and rechargeable lithium-battery-system installations. The 
requirements of Sec.  25.1353(c) remain in effect for batteries and 
battery installations on the Cessna Model 680 airplane that do not 
use lithium-ion batteries.

    Issued in Renton, Washington, on September 9, 2011.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
[FR Doc. 2011-23718 Filed 9-15-11; 8:45 am]