[Federal Register Volume 81, Number 164 (Wednesday, August 24, 2016)]
[Proposed Rules]
[Pages 57810-57812]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2016-20273]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 23

[Docket No. FAA-2016-9001; Notice No. 23-16-02-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: Notice of proposed special conditions.

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SUMMARY: This action proposes special conditions 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 proposed 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: Send your comments on or before October 11, 2016.

ADDRESSES: Send comments identified by docket number FAA-2016-9001 
using any of the following methods:
    [square] Federal eRegulations Portal: Go to http://www.regulations.gov and follow the online instructions for sending your 
comments electronically.
    [square] Mail: Send comments to Docket Operations, M-30, U.S. 
Department of Transportation (DOT), 1200 New Jersey Avenue SE., Room 
W12-140, West Building Ground Floor, Washington, DC 20590-0001.
    [square] Hand Delivery of Courier: Take comments to Docket 
Operations in Room W12-140 of the West Building Ground Floor at 1200 
New Jersey Avenue SE., Washington, DC between 9 a.m. and 5 p.m., Monday 
through Friday, except Federal holidays.
    [square] Fax: Fax comments to Docket Operations at 202-493-2251.
    Privacy: The FAA will post all comments it receives, without 
change, to http://regulations.gov, including any personal information 
the commenter provides. Using the search function of the docket Web 
site, anyone can find and read the electronic form of all comments 
received into any FAA docket, including the name of the individual 
sending the comment (or signing the comment for an association, 
business, labor union, etc.). DOT's complete Privacy Act Statement can 
be found in the Federal Register published on April 11, 2000 (65 FR 
19477-19478), as well as at http://DocketsInfo.dot.gov.
    Docket: Background documents or comments received may be read at 
http://www.regulations.gov at any time. Follow the online instructions 
for accessing the docket or go to the Docket Operations in Room W12-140 
of the West Building Ground Floor at 1200 New Jersey Avenue SE., 
Washington, DC, between 9 a.m., and 5 p.m., Monday through Friday, 
except Federal holidays.

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: 

Comments Invited

    We invite interested people to take part in this rulemaking by 
sending written comments, data, or views. The most helpful comments 
reference a specific portion of the special conditions, explain the 
reason for any recommended change, and include supporting data. We ask 
that you send us two copies of written comments.
    We will consider all comments we receive on or before the closing 
date for comments. We will consider comments filed late if it is 
possible to do so without incurring expense or delay. We may change 
these special conditions based on the comments we receive.

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, PC-12/47 airplanes. The Model PC-12, PC-12/
45, 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 lbs.
    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 proposing 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, 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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    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

[[Page 57811]]

PC-12/47 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 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.

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 feature: 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 lithium batteries. These problems include overcharging, 
over-discharging, flammability of cell components, and cell internal 
defects described in the following paragraphs:
    1. Overcharging: In general, lithium batteries are significantly 
more susceptible to internal failures that can result in self-
sustaining increases in temperature and pressure (i.e., thermal 
runaway) than the Ni-Cd or lead-acid counterparts. 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 may ignite, resulting 
in a fire or explosion. Finally, the severity of thermal runaway due to 
overcharging increases with increasing battery capacity and due to a 
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.
    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.
    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 proposed 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.

    Note 1: 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.

Applicability

    As discussed above, these 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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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.

[[Page 57812]]

List of Subjects in 14 CFR Part 23

    Aircraft, Aviation safety, Signs and symbols.

0
The authority citation for these special conditions is as follows:

    Authority: 49 U.S.C. 106(g), 40113, 44701, 44702, 44704.

The Proposed Special Conditions

0
Accordingly, the Federal Aviation Administration (FAA) proposes the 
following special conditions 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 2: 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 Denver ACO. Alternate methods of compliance other than DO-311 tests 
must be coordinated with the directorate and Denver ACO.

    Issued in Kansas City, Missouri, on August 18, 2016.
Pat Mullen,
Acting Manager, Small Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 2016-20273 Filed 8-23-16; 8:45 am]
 BILLING CODE 4910-13-P