```

[Federal Register Volume 80, Number 184 (Wednesday, September 23, 2015)]
[Rules and Regulations]
[Pages 57291-57293]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2015-24164]

-----------------------------------------------------------------------

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 23

[Docket No.FAA-2015-0721; Notice No. 23-269-SC]

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

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions.

-----------------------------------------------------------------------

SUMMARY: These special conditions are issued 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 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 September 23, 2015.

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.

SUPPLEMENTARY INFORMATION:

Background

    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 
engines.
    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 (1) all 
characteristics of the rechargeable lithium batteries and their 
installation that could affect safe operation of the HA-420 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.

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.
    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).
    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

    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.

Discussion

    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 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

[[Page 57292]]

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 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 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, 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.

Discussion

    Notice of proposed special conditions No. 23-15-03-SC for the Honda 
Aircraft Company, Model HA-420 airplane was published in the Federal 
Register on April 14, 2015 (80 FR 19889). No comments were received, 
and the special conditions are adopted as proposed.

Applicability

    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.
    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 Honda 
Aircraft Company HA-420 is imminent, the FAA finds that good cause 
exists to make these special conditions effective upon issuance.

Conclusion

    This action affects only certain novel or unusual design features 
on one model 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, 44701, 44702, 44704, 14 CFR 
21.16 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 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 
pressure.
    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 
airplane.
    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 
equipment.
    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 
cells.
    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

[[Page 57293]]

    (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 
installation.
    (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.

    Issued in Kansas City, Missouri, on September 14, 2015.
Mel Johnson,
Acting Manager, Small Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 2015-24164 Filed 9-22-15; 8:45 am]
 BILLING CODE 4910-13-P
```