[Federal Register Volume 74, Number 165 (Thursday, August 27, 2009)]
[Rules and Regulations]
[Pages 43619-43621]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E9-20726]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 23

[Docket No. CE296; Special Conditions No. 23-236-SC]


Special Conditions: Cessna Aircraft Company, Model 525C (CJ4); 
Lithium Ion Battery Installation

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions.

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SUMMARY: These special conditions are issued for the Cessna Aircraft 
Company, model 525C (CJ4) airplane. This airplane will have a novel or 
unusual design feature(s) associated with the installation of lithium 
ion (Li-ion) batteries. Cessna Aircraft Company proposes to use a 
lithium-ion main battery on the new model 525C (CJ4) commuter category 
airplane for main battery applications, and is also considering the use 
of this technology in several other auxiliary battery applications in 
this airplane. This type of battery possesses certain failure, 
operational characteristics, and maintenance requirements that differ 
significantly from that of the nickel cadmium and lead acid 
rechargeable batteries currently approved in other normal, utility, 
acrobatic, and commuter 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: August 19, 2009.

FOR FURTHER INFORMATION CONTACT: Ervin Dvorak, Aerospace Engineer, 
Standards Office (ACE-111), Small Airplane Directorate, Aircraft 
Certification Service, Federal Aviation Administration, 901 Locust, 
Room 301, Kansas City, Missouri 64106; telephone (816) 329-4123; 
facsimile (816) 329-4090.

SUPPLEMENTARY INFORMATION: 

Background

    On August 9, 2006, Cessna Aircraft Company applied for an amendment 
to Type Certificate Number A1WI to include the new model 525C (CJ4). 
The model 525C (CJ4), which is a derivative of the model 525B (CJ3) 
currently approved under Type Certificate Number A1WI, is a commuter 
category, low-winged monoplane with ``T'' tailed vertical and 
horizontal stabilizers, retractable tricycle type landing gear and twin 
turbofan engines mounted on the aircraft fuselage. The maximum takeoff 
weight is 16,950 pounds, the VMO/MMO is 305 KIAS/
M 0.77 and maximum altitude is 45,000 feet. Cessna Aircraft Company 
proposes to utilize Li-ion batteries for main battery applications, and 
is considering the use of this technology in several other auxiliary 
battery applications in this airplane.

Type Certification Basis

    Under the provisions of 14 CFR part 21, Sec.  21.101, Cessna 
Aircraft Company must show that the model 525C (CJ4) meets the 
applicable provisions of the requirements incorporated by reference in 
Type Certificate No. A1W1 or 14 CFR

[[Page 43620]]

part 23, as amended by Amendments 23-1 through 23-57 thereto. The 
regulations incorporated by reference in the type certificate are 
commonly referred to as the original type certification basis.
    In addition, the certification basis includes certain special 
conditions, and exemptions that are not relevant to these special 
conditions.
    In addition to the applicable airworthiness regulations and special 
conditions, the model 525C (CJ4) 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 and the FAA must issue a 
finding of regulatory adequacy under Sec.  611 of Public Law 92-574, 
the ``Noise Control Act of 1972.''
    If the Administrator finds that the applicable airworthiness 
regulations (i.e., 14 CFR part 23) do not contain adequate or 
appropriate safety standards for the model 525C (CJ4) because of a 
novel or unusual design feature, special conditions are prescribed 
under the provisions of Sec.  21.16.
    The FAA issues special conditions, as defined in Sec.  11.19, under 
Sec.  11.38 and they become part of the type certification basis under 
Sec.  21.101.
    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, the special conditions would also 
apply to the other model under Sec.  21.101.

Novel or Unusual Design Features

    Cessna Aircraft Company, model 525C (CJ4) will incorporate the 
following novel or unusual design features:
    Cessna Aircraft Company proposes to use lithium ion (Li-ion) 
batteries for main battery applications, and is considering the use of 
this technology in several other auxiliary battery applications on the 
Cessna Aircraft Company, model 525C (CJ4) airplane. This type of 
battery possesses certain failure and operational characteristics, and 
maintenance requirements that differ significantly from that of the 
nickel cadmium (Ni-Cd) and lead acid rechargeable batteries currently 
approved for installation in small airplanes. Current regulations in 14 
CFR part 23 do not address installation of Li-ion batteries. These 
special conditions require that all characteristics of the Li-ion 
battery and its installation that could affect safe operation of the 
Cessna Aircraft Company, model 525C (CJ4) airplane are addressed, along 
with establishing that appropriate maintenance requirements must be 
provided to ensure electrical power is available from the batteries 
when needed.

Discussion

    The applicable part 21 and part 23 airworthiness regulations 
governing the installation of batteries in general aviation airplanes, 
including part 23, Sec.  23.1353 were derived from Civil Air 
Regulations (CAR 3) as part of the recodification that established 
Federal Aviation Regulation 14 CFR part 23. The battery requirements, 
which were identified as 14 CFR part 23, Sec.  23.1353, were basically 
a rewording of the CAR requirements that did not add any substantive 
technical requirements. An increase in incidents involving battery 
fires and failures that accompanied the increased use of Ni-Cd 
batteries in airplanes resulted in rulemaking activities on the battery 
requirements for business jet and commuter category airplanes. These 
regulations were incorporated into 14 CFR part 23, Sec.  23.1353(f) and 
(g), which apply only to Ni-Cd battery installations.
    The proposed use of Li-ion batteries on the Cessna Aircraft 
Company, model 525C (CJ4) airplane has prompted the FAA to review the 
adequacy of the existing battery regulations with respect to that 
chemistry. As the result of this review, the FAA has determined that 
the existing regulations do not adequately address several failure, 
operational, and maintenance characteristics of Li-ion batteries that 
could affect safety of the battery installation and the reliability of 
the Cessna Aircraft Company, model 525C (CJ4) airplane electrical power 
supply.
    Li-ion batteries in general are significantly more susceptible to 
internal failures that can result in self-sustaining increases in 
temperature and pressure (i.e. thermal runaway) than their Ni-Cd and 
lead-acid counterparts. This is especially true for overcharging a Li-
ion, which will likely result in explosion, fire, or both. Certain 
types of Li-ion batteries pose a potential safety problem because of 
the instability and flammability of the organic electrolyte employed by 
the cells of those batteries. The severity of thermal runaway increases 
with increasing battery capacity due to the higher amount of 
electrolyte in large batteries.
    If the discharge of the cells is below a typical voltage of 3.0 
volts on some versions of Li-ion batteries, they will subsequently no 
longer accept a charge. This loss of capacity may not be detected by 
the simple voltage measurements commonly available to flight crews as a 
means of checking battery status, a problem shared with Ni-Cd 
batteries.
    Unlike Ni-Cd and lead-acid cells, some types of Li-ion cells employ 
electrolytes that are known to be flammable. This material can serve as 
a source of fuel for an external fire in the event of a breach of the 
cell container.
    The intent of these special conditions is to establish appropriate 
airworthiness standards for Li-ion battery installations in the Cessna 
Aircraft Company, model 525C (CJ4) airplane, and to ensure, as required 
by 14 CFR part 23, Sec.  23.601, that these battery installations do 
not possess hazardous or unreliable design characteristics. These 
special conditions adopt the following requirements as a means of 
addressing these concerns:
     Inclusion of those sections of 14 CFR part 23, Sec.  
23.1353 that are applicable to Li-ion batteries.
     Inclusion of the flammable fluid fire protection 
requirements of 14 CFR part 23, Sec.  23.863. In the past, this rule 
was not applied to the batteries of business jet or commuter category 
airplanes since the electrolytes utilized in lead-acid and Ni-CD 
batteries are not considered to be flammable.
     Addition of new requirements to address the potential 
hazards of overcharging and overdischarging that are unique to Li-ion 
battery designs.
    Addition of maintenance requirements to ensure that batteries used 
as spares are maintained in an appropriate state of charge (SOC).

Discussion of Comments

    Notice of proposed special conditions No. 23-09-02-SC for the 
Cessna Aircraft Company, Model 525C (CJ4) airplanes was published on 
June 4, 2009 (74 FR 26818). No comments were received, and the special 
conditions are adopted as proposed.

Applicability

    As discussed above, these special conditions are applicable to the 
Cessna model 525C (CJ4). 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.

Conclusion

    This action affects only certain novel or unusual design features 
on one model of airplane. It is not a rule of general applicability.

List of Subjects in 14 CFR Part 25

    Aircraft, Aviation safety, Reporting and recordkeeping 
requirements.


[[Page 43621]]


    The authority citation for these special conditions is as follows:

    Authority 49 U.S.C. 106(g), 40113, and 44701; 14 CFR 21.16 and 
21.17; 14 CFR 11.38 and 11.19.

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 Cessna Aircraft Company, model 525C 
(CJ4) airplanes.
    Cessna Aircraft Company, model 525C (CJ4) Li-ion battery 
installation.
    In lieu of the requirements of 14 CFR part 23, Sec.  23.1353 (a) 
through (e), Li-ion batteries and battery installations on the Cessna 
Aircraft Company, model 525C (CJ4) airplane must be designed and 
installed as follows:
    (1) Safe cell temperatures and pressures must be maintained during 
any probable charging or discharging condition, or during any failure 
of the charging or battery monitoring system not shown to be extremely 
remote. The Li-ion battery installation must be designed to preclude 
explosion or fire in the event of those failures.
    (2) Li-ion batteries must be designed to preclude the occurrence of 
self-sustaining, uncontrolled increases in temperature or pressure.
    (3) No explosive or toxic gasses emitted by any Li-ion battery in 
normal operation or as the result of any failure of the battery 
charging or monitoring system, or battery installation not shown to be 
extremely remote, may accumulate in hazardous quantities within the 
airplane.
    (4) Li-ion batteries that contain flammable fluids must comply with 
the flammable fluid fire protection requirements of 14 CFR part 23, 
Sec.  23.863(a) through (d).
    (5) No corrosive fluids or gasses that may escape from any Li-ion 
battery may damage surrounding airplane structure or adjacent essential 
equipment.
    (6) Each Li-ion battery installation must have provisions to 
prevent any hazardous effect on structure or essential systems that may 
be caused by the maximum amount of heat the battery can generate during 
a short circuit of the battery or of its individual cells.
    (7) Li-ion battery installations must have a system to control the 
charging rate of the battery automatically, 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 Li-ion battery installation whose function 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 capacity and SOC of the batteries have 
fallen below levels considered acceptable for dispatch of the airplane.
    (9) The Instructions for Continued Airworthiness (ICAW) must 
contain recommended manufacturers maintenance and inspection 
requirements to ensure that batteries, including single cells, meet a 
safety function level essential to the aircraft's continued 
airworthiness.
    (i) The ICAW must contain operating instructions and equipment 
limitations in an installation maintenance manual.
    (ii) The ICAW must contain installation procedures and limitation 
in a maintenance manual, sufficient to ensure that cells or batteries, 
when installed according to the installation procedures, still meet 
safety functional levels, essential to the aircraft's continued 
airworthiness. The limitation must identify any unique aspects of the 
installation.
    (iii) The ICAW must contain corrective maintenance procedures to 
functionally check battery capacity at manufacturers recommended 
inspection intervals.
    (iv) The ICAW must contain scheduled servicing information to 
replace batteries at manufacturers recommended replacement time.
    (v) The ICAW must contain maintenance inspection requirements to 
visually check for a battery and/or charger degradation.
    (10) The ICAW must contain requirements that batteries in a 
rotating stock (spares) that have experienced degraded charge retention 
capability or other damage due to prolonged storage must be 
functionally checked at manufacturers recommended inspection intervals 
before installation.
    (11) The System Safety Assessment process must address the software 
and complex hardware levels for the sensing, monitoring and warning 
systems, if these systems contain complex devices. The functional 
hazard assessment (FHA) for the system is required based on the 
intended functions described. The criticality of the specific functions 
will be determined by the safety assessment process for compliance with 
14 CFR part 23, Sec.  23.1309, and Advisory Circular 23.1309-1D 
contains acceptable means for accomplishing this requirement. For 
determining the failure condition, the criticality of a function will 
include the mitigating factors. The failure conditions must address the 
loss of function and improper operations.
    These special conditions are not intended to replace 14 CFR part 
23, Sec.  23.1353 in the certification basis of the Cessna Aircraft 
Company, model 525C (CJ4) airplanes. These special conditions apply 
only to Li-ion batteries and battery installations. The battery 
requirements of 14 CFR part 23, Sec.  23.1353 would remain in effect 
for batteries and battery installations on the Cessna Aircraft Company, 
model 525C (CJ4) airplane that do not use Li-ion chemistry.

    Issued in Kansas City, Missouri, on August 19, 2009.
Kim Smith,
Manager, Small Airplane Directorate, Aircraft Certification Service.
[FR Doc. E9-20726 Filed 8-26-09; 8:45 am]
BILLING CODE 4910-13-P