[Federal Register Volume 80, Number 71 (Tuesday, April 14, 2015)]
[Proposed Rules]
[Pages 19889-19892]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2015-08586]



Federal Aviation Administration

14 CFR Part 23

[Docket No. FAA-2015-0721; Notice No. 23-15-03-SC]

Special Conditions: Honda Aircraft Company, Model HA-420 
HondaJet, Lithium-Ion Batteries

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed special conditions.


SUMMARY: This action proposes special conditions for the Honda Aircraft 
Company, Model HA-420 airplane. This airplane will have a novel or 
unusual design feature associated with the installation of lithium-ion 
(Li-ion) batteries. 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 May 4, 2015.

ADDRESSES: Send comments identified by docket number [FAA-2015-0721] 
using any of the following methods:
    [ssquf] Federal eRegulations Portal: Go to http://www.regulations.gov and follow the online instructions for sending your 
comments electronically.
    [ssquf] 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.
    [ssquf] 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.
    [ssquf] 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: Les Lyne, Policies & Procedures 
Branch, ACE-114, Federal Aviation Administration, Small Airplane 
Directorate, Aircraft Certification Service, 901 Locust; Kansas City, 
Missouri 64106; telephone (816) 329-4171; facsimile (816) 329-4090.


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.

[[Page 19890]]


    On October 11, 2006, Honda Aircraft Company applied for a type 
certificate for their new Model HA-420. On October 10, 2013, Honda 
Aircraft Company requested an extension with an effective application 
date of October 1, 2013. This extension changed the type certification 
basis to amendment 23-62.
    The HA-420 is a four to five passenger (depending on 
configuration), two crew, lightweight business jet with a 43,000-foot 
service ceiling and a maximum takeoff weight of 9963 pounds. The 
airplane is powered by two GE-Honda Aero Engines (GHAE) HF-120 turbofan 
    The current regulatory requirements for part 23 airplanes do not 
contain adequate requirements for the application of Li-ion batteries 
in airborne applications. 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. Therefore, the FAA is 
proposing this special condition to require that all characteristics of 
the rechargeable lithium batteries and their installation that could 
affect safe operation of the HA-420 are addressed, and appropriate 
Instructions for Continued Airworthiness which include maintenance 
requirements are established to ensure the availability of electrical 
power from the batteries when needed.

Type Certification Basis

    Under the provisions of 14 CFR 21.17, Honda Aircraft Company must 
show that the HA-420 meets the applicable provisions of part 23, as 
amended by Amendments 23-1 through 23-62 thereto.
    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 HA-420 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 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.
    In addition to the applicable airworthiness regulations and special 
conditions, the HA-420 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 section 611 of Public Law 92-574, the ``Noise 
Control Act of 1972.''
    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.  21.17(a)(2).

Novel or Unusual Design Features

    The HA-420 will incorporate the following novel or unusual design 
feature: The installation of Li-ion batteries.
    The current regulatory requirements for part 23 airplanes do not 
contain adequate requirements for the application of Li-ion batteries 
in airborne applications. 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 parts 21 and 23 airworthiness regulations governing 
the installation of batteries in general aviation airplanes, including 
Sec.  23.1353, were derived from Civil Air Regulations (CAR 3) as part 
of the recodification that established 14 CFR part 23. The battery 
requirements, which are identified in Sec.  23.1353, were 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 Nickel-Cadmium (Ni-Cad) 
batteries in aircraft resulted in rulemaking activities on the battery 
requirements for transport category airplanes. These regulations were 
incorporated into Sec.  23.1353(f) and (g), which apply only to Ni-Cad 
battery installations.
    The proposed use of Li-ion batteries on the HA-420 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 of the HA-420 airplane electrical power supply.
    The introduction of Li-ion batteries into aircraft raises some 
concern about associated battery/cell monitoring systems and how these 
may affect utilization of an otherwise ``good'' battery as an energy 
source to the electrical system when monitoring components fail. 
Associated battery/cell monitoring systems (i.e., temperature, state of 
charge, etc.) should be evaluated/tested with respect the expected 
extremes in the aircraft operating environment.
    Li-ion batteries typically have different electrical impedance 
characteristics than lead-acid or Ni-Cad batteries. Honda Aircraft 
Company needs to evaluate other components of the aircraft electrical 
system with respect to these characteristics.
    At present, there is very limited experience regarding the use of 
Li-ion rechargeable batteries in applications involving commercial 
aviation. However, other users of this technology range from wireless 
telephone manufacturers to the electric vehicle industry and have noted 
significant safety issues regarding the use of these types of 
batteries, some of which are 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 their nickel-cadmium 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 
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--a 
problem shared with nickel-cadmium batteries.
    3. Flammability of Cell Components: Unlike nickel-cadmium and lead-
acid batteries, some types of lithium batteries use liquid electrolytes 
that are flammable. The electrolyte can serve as a source of fuel for 
an external fire if

[[Page 19891]]

there is a breach of the battery container.
    These safety issues experienced by users of lithium batteries raise 
concern about the use of these batteries in commercial aviation. The 
intent of the proposed special condition is to establish appropriate 
airworthiness standards for lithium battery installations in the HA-420 
and to ensure, as required by Sec. Sec.  23.1309 and 23.601, that these 
battery installations are not hazardous or unreliable.
    Additionally, the Radio Technical Commission for Aeronautics 
(RTCA), in a joint effort with the FAA and industry, has released RTCA/
DO-311, Minimum Operational Performance Standards for Rechargeable 
Lithium Battery Systems, which gained much of its text directly from 
previous Li-ion special conditions. Honda Aircraft Company proposes to 
use DO-311 as the primary methodology for assuring the battery will 
perform its intended functions safely as installed in the HA-420 
airplane and as the basis for test and qualification of the battery. 
This Special Condition incorporates applicable portions of DO-311.


    As discussed above, these special conditions are applicable to the 
HA-420. Should Honda 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.
    Provisional certification of the HA-420 is currently scheduled for 
June 2015. The substance of these special conditions has been subject 
to the notice and public-comment procedure in several prior instances, 
specifically special conditions 23-236-SC, 23-247-SC, and 23-249-SC. 
Therefore, because a delay would significantly affect the applicant's 
both installation of the system and certification of the airplane, we 
are shortening the public-comment period to 20 days.


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

List of Subjects in 14 CFR Part 23

    Aircraft, Aviation safety, Signs and symbols.

    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

    Accordingly, the Federal Aviation Administration (FAA) proposes the 
following special conditions as part of the type certification basis 
for Honda Aircraft Company, HA-420 airplanes.

1. Lithium-Ion Battery Installation

    a. 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 applicant must design Li-ion battery installation to 
preclude explosion or fire in the event of those failures.
    b. The applicant must design the Li-ion batteries to preclude the 
occurrence of self-sustaining, uncontrolled increases in temperature or 
    c. 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 
    d. Li-ion batteries that contain flammable fluids must comply with 
the flammable fluid fire protection requirements of Sec.  23.863(a) 
through (d).
    e. No corrosive fluids or gasses that may escape from any Li-ion 
battery may damage surrounding airplane structure or adjacent essential 
    f. The applicant must provide provision for each installed Li-ion 
battery 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 
    g. Li-ion battery installations must have--
    (1) A system to control the charging rate of the battery 
automatically so as to prevent battery overheating or overcharging; or
    (2) 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
    (3) 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.
    h. 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 
flightcrew members whenever the capacity and State of Charge (SOC) of 
the batteries have fallen below levels considered acceptable for 
dispatch of the airplane.
    i. The Instructions for Continued Airworthiness (ICA) 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.
    (1) The ICA must contain operating instructions and equipment 
limitations in an installation maintenance manual.
    (2) The ICA must contain installation procedures and limitations 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 limitations must identify any unique aspects of the 
    (3) The ICA must contain corrective maintenance procedures to check 
battery capacity at manufacturers recommended inspection intervals.
    (4) The ICA must contain scheduled servicing information to replace 
batteries at manufacturers recommended replacement time.
    (5) The ICA must contain maintenance and inspection requirements to 
check visually for battery and/or charger degradation.
    j. 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.
    k. The System Safety Assessment (SSA) process should 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 Sec.  23.1309. Advisory Circular 23-1309-1C 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.

[[Page 19892]]

    Issued in Kansas City, Missouri, on April 6, 2015.
Pat Mullen,
Acting Manager, Small Airplane Directorate, Aircraft Certification 
[FR Doc. 2015-08586 Filed 4-13-15; 8:45 am]