[Federal Register Volume 81, Number 224 (Monday, November 21, 2016)]
[Rules and Regulations]
[Pages 83112-83114]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2016-28013]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 23

[Docket No. FAA-2016-9001; Special Conditions No. 23-278-SC]


Special Conditions: Pilatus Aircraft, Ltd., Model PC-12, PC-12/
45, and PC-12/47 Airplanes, Lithium Batteries

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions.

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SUMMARY: These special conditions are issued for the Pilatus Aircraft, 
Ltd., Model PC-12, PC-12/45, and PC-12/47 airplanes. This airplane as 
modified by Finnoff Aviation will have a novel or unusual design 
feature associated with the installation of a rechargeable lithium 
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: These special conditions are effective November 21, 2016 and are 
applicable on November 10, 2016.

FOR FURTHER INFORMATION CONTACT: Ruth Hirt, Federal Aviation 
Administration, Programs and Procedures, ACE-114, Small Airplane 
Directorate, Aircraft Certification Service, 901 Locust; Kansas City, 
Missouri 64106; telephone (816) 329-4108; facsimile (816) 329-4090.

SUPPLEMENTARY INFORMATION:

Background

    On September 28, 2015, Finnoff Aviation applied for a supplemental 
type certificate for installation of a rechargeable lithium battery in 
the Model PC-12, PC-12/45, and PC-12/47 airplanes. The Model PC-12, PC-
12/45, and PC-12/47 airplanes are single-engine turboprop-powered 
business aircraft that can accommodate up to nine passengers with a 
take-off weight up to 10,450 pounds.
    The current regulatory requirements for part 23 airplanes do not 
contain adequate requirements for the application of rechargeable 
lithium batteries in airborne applications. This type of battery 
possesses certain failure and operational characteristics with 
maintenance requirements that differ significantly from that of the 
nickel-cadmium (Ni-Cd) and lead-acid rechargeable batteries currently 
approved in other normal, utility, acrobatic, and commuter category 
airplanes. Therefore, the FAA is issuing this special condition to 
address (1) all characteristics of the rechargeable lithium batteries 
and their installation that could affect safe operation of the modified 
Model PC-12, PC-12/45, and PC-12/47 airplanes, and (2) appropriate 
Instructions for Continued Airworthiness (ICAW) that include 
maintenance requirements to ensure the availability of electrical power 
from the batteries when needed.

Type Certification Basis

    Under the provisions of Sec.  21.101, Finnoff Aviation must show 
that the Model PC-12, PC-12/45, and PC-12/47 airplanes, as changed, 
continue to meet the applicable provisions of the regulations 
incorporated by reference in Type Certificate No. A78EU \1\ or the 
applicable regulations in effect on the date of application for the 
change.
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    \1\ http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/6BCB00B1F3CA4EF886257FED0069EF2D?OpenDocument.
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    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 PC-12, PC-12/45, and PC-12/
47 airplanes because of a novel or unusual design feature, special 
conditions are prescribed under the provisions of Sec.  21.16.
    In addition to the applicable airworthiness regulations and special 
conditions, the Model PC-12, PC-12/45, and PC-12/47 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.
    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

[[Page 83113]]

also apply to the other model under Sec.  21.101.

Novel or Unusual Design Features

    The Model PC-12, PC-12/45, and PC-12/47 airplanes will incorporate 
the following novel or unusual design features: Installation of a 
rechargeable lithium battery as the main or engine start aircraft 
battery.

Discussion

    Presently, there is limited experience with use of rechargeable 
lithium batteries and rechargeable lithium battery systems in 
applications involving commercial aviation. However, other users of 
this technology, ranging from personal computers, wireless telephone 
manufacturers to the electric vehicle industry, have noted safety 
problems with rechargeable lithium batteries. These problems include 
overcharging, over-discharging, flammability of cell components, cell 
internal defects, and during exposure to extreme temperatures that are 
described in the following paragraphs.
    1. Overcharging: In general, rechargeable lithium batteries are 
significantly more susceptible than their Ni-Cd or lead-acid 
counterparts to thermal runway, which is an internal failure that can 
result in self-sustaining increases in temperature and pressure. This 
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 battery 
cells 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 flight crews as a means of checking battery status, which 
is a problem shared with Ni-Cd batteries. In addition, over-discharging 
has the potential to lead to an unsafe condition (creation of dendrites 
that could result in internal short circuit during the recharging 
cycle).
    3. Flammability of Cell Components: Unlike Ni-Cd and lead-acid 
batteries, some types of lithium batteries use liquid electrolytes that 
are flammable. The electrolyte may serve as a source of fuel for an 
external fire, if there is a breach of the battery container.
    4. Cell Internal Defects: The rechargeable lithium batteries and 
rechargeable battery systems have a history of undetected cell internal 
defects. These defects may or may not be detected during normal 
operational evaluation, test, and validation. This may lead to unsafe 
conditions when operating in service.
    5. Extreme Temperatures: Exposure to an extreme temperature 
environment has the potential to create major hazards. Care must be 
taken to ensure that the lithium battery remains within the 
manufacturer's recommended specification.
    These problems experienced by users of lithium batteries raise 
concern about the use of these batteries in commercial aviation. The 
intent of the special condition is to establish appropriate 
airworthiness standards for lithium battery installations in the Model 
PC-12, PC-12/45, and PC-12/47 airplanes and to ensure, as required by 
Sec. Sec.  23.1309 and 23.601, that these battery installations are 
neither hazardous nor unreliable.
    In summary, the lithium battery installation will consider the 
following items:
    (a) The flammable fluid fire protection requirement is Sec.  
23.863. In the past, this rule was not applied to batteries of normal, 
utility, acrobatic, and commuter category airplanes since the 
electrolytes utilized in Ni-Cd and lead-acid batteries are not 
flammable.
    (b) New Instructions for Continuous Airworthiness that include 
maintenance requirements to ensure that batteries used as spares have 
been maintained in an appropriate state of charge and installed lithium 
batteries have been sufficiently charged at appropriate intervals. 
These instructions must also describe proper repairs, if allowed, and 
battery part number configuration control.
    (c) The applicant must conduct a system safety assessment for the 
failure condition classification of a failure of the battery charging 
and monitoring functionality (per Advisory Circular AC 23.1309-1E),\2\ 
and develop mitigation to preclude any adverse safety effects. 
Mitigation may include software, Airborne Electronic Hardware (AEH) or 
a combination of software and hardware, which should be developed to 
the appropriate Design Assurance Level(s) (DALs), respectively (per 
Advisory Circular AC 20-115C \3\ and Advisory Circular AC 20-152).\4\
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    \2\ http://rgl.faa.gov/Regulatory_and_Guidance_Library/
rgAdvisoryCircular.nsf/0/719e41e1d26099108625795d005d5302/$FILE/
23.1309-1E.pdf.
    \3\ http://rgl.faa.gov/Regulatory_and_Guidance_Library/
rgAdvisoryCircular.nsf/0/e35fbc0060e2159186257bbe00719fb3/$FILE/
AC20-115C.pdf.
    \4\ http://rgl.faa.gov/Regulatory_and_Guidance_Library/
rgAdvisoryCircular.nsf/0/6d4ae0bf1bde3579862570360055d119/$FILE/
AC%2020-152.pdf.
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    (d) New requirements, in the special conditions section, address 
the hazards of overcharging and over-discharging that are unique to 
lithium batteries, which should be applied to all rechargeable lithium 
battery and battery installations on the Model PC-12, PC-12/45, and PC-
12/47 airplanes in lieu of the requirements of Sec.  
23.1353(a)(b)(c)(d)(e), amendment 23-49.
    These special conditions are not intended to replace Sec.  
23.1353(a)(b)(c)(d)(e) at amendment 23-49 in the certification basis of 
Model PC-12, PC-12/45, and PC-12/47 airplanes. These special conditions 
apply only to rechargeable lithium batteries and lithium battery 
systems and their installations. The requirements of Sec.  25.1353 at 
amendment 23-49 remains in effect for batteries and battery 
installations on Model PC-12, PC-12/45, and PC-12/47 airplanes that do 
not use rechargeable lithium batteries.

Discussion of Comments

    Notice of proposed special conditions No. 23-16-02-SC for the 
Pilatus Aircraft, Ltd., Model PC-12, PC-12/45, and PC-12/47 Airplanes, 
Lithium Batteries was published in the Federal Register on August 24, 
2016 (81 FR 57810). No comments were received, and the special 
conditions are adopted as proposed.

Applicability

    The special conditions are applicable to the Model PC-12, PC-12/45, 
and PC-12/47 airplanes. Should Finnoff Aviation apply at a later date 
for a supplemental type certificate to modify any other model included 
on Type Certificate No. A78EU \5\ to incorporate the same novel or 
unusual design feature, the special conditions would apply to that 
model as well.
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    \5\ http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/6BCB00B1F3CA4EF886257FED0069EF2D?OpenDocument.
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    Under standard practice, the effective date of final special 
conditions would be 30 days after the date of publication in the 
Federal Register; however, as the certification date for the Pilatus 
Aircraft, Ltd., Model PC-12, PC-12/45, and PC-12/47 airplanes is 
imminent, the FAA finds that good cause exists to make

[[Page 83114]]

these special conditions effective upon issuance.

Conclusion

    This action affects only certain novel or unusual design features 
on one model series of 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 23

    Aircraft, Aviation safety, Signs and symbols.

Citation

    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 
21.101; and 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 Pilatus Aircraft, Ltd., Model PC-12, 
PC-12/45, and PC-12/47 airplanes modified by Finnoff Aviation.
    1. Installation of Lithium Batteries must show compliance to the 
following requirements:
    (1) Safe cell temperatures and pressures must be maintained 
during--
    i. Normal operations;
    ii. Any probable failure conditions of charging or discharging or 
battery monitoring system;
    iii. Any failure of the charging or battery monitoring system not 
shown to be extremely remote.
    (2) The rechargeable lithium battery installation must be designed 
to preclude explosion or fire in the event of (1)(ii) and (1)(iii) 
failures.
    (3) Design of the rechargeable lithium batteries must preclude the 
occurrence of self-sustaining, uncontrolled increases in temperature or 
pressure.
    (4) No explosive or toxic gasses emitted by any rechargeable 
lithium battery in normal operation or as the result of any failure of 
the battery charging system, monitoring system, or battery installation 
which is not shown to be extremely remote, may accumulate in hazardous 
quantities within the airplane.
    (5) Installations of rechargeable lithium batteries must meet the 
requirements of Sec.  23.863(a) through (d) at amendment 23-34.
    (6) No corrosive fluids or gases that may escape from any 
rechargeable lithium battery may damage surrounding structure or any 
adjacent systems, equipment, electrical wiring, or the airplane in such 
a way as to cause a major or more severe failure condition, in 
accordance with Sec.  23.1309(c) at amendment 23-62 and applicable 
regulatory guidance.
    (7) Each rechargeable lithium 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.
    (8) Rechargeable lithium battery installations must have--
    i. A system to automatically control the charging rate of the 
battery to prevent battery overheating and overcharging, or;
    ii. 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;
    iii. 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.
    (9) Any rechargeable lithium battery installation functionally 
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 (SOC) of 
the batteries has fallen below levels considered acceptable for 
dispatch of the airplane.
    (10) The Instructions for Continued Airworthiness required by Sec.  
23.1529 at amendment 23-26 must contain maintenance requirements to 
assure that the battery has been sufficiently charged at appropriate 
intervals specified by the battery manufacturer and the equipment 
manufacturer that contain the rechargeable lithium battery or 
rechargeable lithium battery system. This is required to ensure that 
lithium rechargeable batteries and lithium rechargeable battery systems 
will not degrade below specified ampere-hour levels sufficient to power 
the aircraft system. The Instructions for Continued Airworthiness must 
also contain procedures for the maintenance of replacement batteries in 
spares storage to prevent the installation of batteries that have 
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.

    Note: 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 there is 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.

    (11) In showing compliance with the proposed special conditions 
herein, paragraphs (1) through (8), and the RTCA document, Minimum 
Operational Performance Standards for Rechargeable Lithium Battery 
Systems, DO-311, may be used. The list of planned DO-311 tests should 
be documented in the certification or compliance plan and agreed to by 
the geographic ACO. Alternate methods of compliance other than DO-311 
tests must be coordinated with the directorate and geographic ACO.

    Issued in Kansas City, Missouri, on November 10, 2016.
Mel Johnson,
Acting Manager, Small Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 2016-28013 Filed 11-18-16; 8:45 am]
 BILLING CODE 4910-13-P