[Federal Register Volume 79, Number 136 (Wednesday, July 16, 2014)]
[Proposed Rules]
[Pages 41457-41459]
[FR Doc No: 2014-16645]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-2014-0434; Notice No. 25-14-08-SC]

Special Conditions: Bombardier Aerospace, Models BD-500-1A10 and
BD-500-1A11; Composite Wing and Fuel Tank Structure Post-Crash Fire
Survivability

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed special conditions.

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SUMMARY: This action proposes special conditions for the Bombardier
Aerospace, Models BD-500-1A10 and BD-500-1A11 series airplanes. These
airplanes will have novel or unusual design features when compared to
the state of technology envisioned in the airworthiness standards for
transport category airplanes. These design features are associated with
the composite materials used in the construction of the fuel tank skin
and structure, which may behave differently in a post-crash fire than
traditional aluminum construction. 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 September 2, 2014.

ADDRESSES: Send comments identified by docket number FAA-2014-0434
using any of the following methods:
     Federal eRegulations Portal: Go to http://www.regulations.gov/ and follow the online instructions for sending
your comments electronically.
     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.
     Hand Delivery or 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 8 a.m. and 5 p.m.,
Monday through Friday, except federal holidays.
     Fax: Fax comments to Docket Operations at<PHONE_NUMBER>.
    Privacy: The FAA will post all comments it receives, without
change, to http://www.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:  Alan Sinclair, FAA, Airframe and
Cabin Safety Branch, ANM-115 Transport Airplane Directorate, Aircraft
Certification Service, 1601 Lind Avenue SW., Renton, Washington 98057-
3356; telephone<PHONE_NUMBER>; facsimile<PHONE_NUMBER>.

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 will consider all comments we receive on or before the closing
date for comments. We may change these special conditions based on the
comments we receive.

Background

    On December 10, 2009, Bombardier Aerospace applied for a type
certificate for their new Models BD-500-1A10 and BD-500-1A11 series
airplanes (hereafter collectively referred to as ``CSeries''). The
CSeries airplanes are swept-wing monoplanes with an aluminum alloy
fuselage sized for 5-abreast seating. Passenger capacity is designated
as 110 for the Model BD-500-1A10 and 125 for the Model BD-500-1A11.
Maximum takeoff weight is 131,000 pounds for the Model BD-500-1A10 and
144,000 pounds for the Model BD-500-1A11.
    Conventional airplanes with aluminum skin and structure provide a
well-understood level of safety during post-crash fire scenarios with
respect to fuel tanks. This is based on service history and extensive
full-scale fire testing. The CSeries airplanes will not be fabricated
primarily with aluminum for the fuel tank structure. Instead, they will
be fabricated using predominantly composite structure and skin for the
wings and fuel tanks. Composites may or may not have the equivalent
capability of aluminum, and current regulations do not provide
objective performance requirements for wing and fuel tank structure
with respect to post-crash fire safety. Because the use of composite
structure is novel and unusual with respect to the designs envisioned
when the applicable regulations were promulgated, additional tests and
analyses substantiation will be required to show that the CSeries
airplanes will provide an acceptable level of safety with respect to
the performance of the wings and fuel tanks during an external fuel-fed
fire.

Type Certification Basis

    Under the provisions of Title 14, Code of Federal Regulations (14
CFR) 21.17, Bombardier Aerospace must show that the CSeries airplanes
meet the applicable provisions of 14 CFR part 25 as amended by
Amendments 25-1 through 25-129.
    If the Administrator finds that the applicable airworthiness
regulations (i.e., 14 CFR part 25) do not contain adequate or
appropriate safety standards for the CSeries 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 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 CSeries 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, and the FAA must issue a
finding of regulatory adequacy under Sec.  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 CSeries airplanes will incorporate the following novel or
unusual design features: The structural elements and skin of the wings
and fuel tanks will be fabricated using predominantly composite
materials rather than conventional aluminum.

Discussion

    Transport category airplanes in operation today have traditionally
been designed with aluminum materials. Conventional airplanes with
aluminum skin and structure provide a well-understood level of safety
during post-crash fires with respect to fuel tanks. Current regulations
were developed and have evolved under the assumption that wing
construction would be of aluminum materials.
    Aluminum has the following properties with respect to fuel tanks
and fuel-fed external fires:
     Aluminum is highly thermally conductive and readily
transmits the heat of a fuel-fed external fire to fuel in the tank.
This has the benefit of rapidly driving the fuel tank ullage to exceed
the upper flammability limit of fuel vapors prior to fuel tank skin
burn-through or heating of the wing upper surface above the auto-
ignition temperature, thus greatly reducing the threat of fuel tank
explosion.
     Aluminum panels at thicknesses previously used in wing
lower surfaces of large transport category airplanes have been fire
resistant as defined in 14 CFR 1.1 and AC 20-135,

Powerplant Installation and Propulsion System Component Fire Protection
Test Methods, Standards, and Criteria

     Heat absorption capacity of aluminum and fuel prevent
burn-through or wing collapse for a time interval that generally exceed
the passenger evacuation time.
    The ability of aluminum wing surfaces to withstand post-crash fire
conditions when wetted by fuel on their interior surface has been
demonstrated by tests conducted at the FAA Technical Center. Results of
these tests have verified adequate dissipation of heat across wetted
aluminum fuel tank surfaces so that localized hot spots do not occur,
thus minimizing the threat of explosion. This inherent capability of
aluminum to dissipate heat also allows the wing lower surface to retain
its load-carrying characteristics during a fuel-fed ground fire and
significantly delay wing collapse or burn-through for a time interval
that usually exceeds evacuation times. In addition, as an aluminum fuel
tank is heated with significant quantities of fuel inside, fuel vapor
accumulates in the ullage space, exceeding the upper flammability limit
relatively quickly and thus reducing the threat of a fuel tank
explosion prior to fuel tank burn-through.
    Fuel tanks constructed with composite materials may or may not have
equivalent properties. Advisory Circular (AC) 20-107B (Change 1),
Composite Aircraft Structure, section 11b, ``Fire Protection,
Flammability and Thermal Issues,'' states: ``Wing and fuselage
applications should consider the effects of composite design and
construction on the resulting passenger safety in the event of in-
flight fires or emergency landing conditions, which combine with
subsequent egress when a fuel-fed fire is possible.'' Pertinent to the
wing structure, post-crash fire passenger survivability is dependent on
the time available for passenger evacuation prior to fuel tank breach
or structural failure. Structural failure can be a result of
degradation in load-carrying capability in the upper or lower wing
surface caused by a fuel-fed ground fire and also as a result of over-
pressurization caused by ignition of fuel vapors in the fuel tank.
    For the CSeries airplanes, composite materials will be used to
fabricate the majority of wing fuel tank. Hence, the current
regulations may not be adequate for the certification of the CSeries
airplanes featuring wing fuel tanks fabricated with composite material.
Therefore, Bombardier must present additional confirmation by test and
analysis that the CSeries airplanes' design provides an acceptable
level of safety with respect to the performance of the wing fuel tanks
when exposed to the direct effects of post-crash ground fire or under-
wing fuel-fed fires.
    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.

Applicability

    As discussed above, these special conditions are applicable to the
Models BD-500-1A10 and BD-500-1A11 series airplanes. Should Bombardier
Aerospace 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 two model series of airplanes. It is not a rule of general
applicability.

List of Subjects in 14 CFR Part 25

    Aircraft, Aviation safety, Reporting and recordkeeping
requirements.

    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 Bombardier Aerospace Models BD-500-1A10 and BD-500-1A11 series
airplanes.

Composite Wing and Fuel Tank Post-Crash Fire Survivability

    1. The wing fuel tank structure must withstand an external fuel-fed
pool fire for a minimum of 5 minutes.
    2. The integrity of the wing fuel tank structure must be
demonstrated at:
     Minimum fuel load, not less than reserve fuel level;
     Maximum fuel load equal to the maximum range fuel
quantity; and
     Any other critical fuel loads.
    3. The demonstration must consider fuel tank flammability, burn-
through resistance, wing structural strength retention properties, and
auto-ignition threats from localized heating of composite structure,
fasteners, or any other feature that may produce an ignition source
during a ground fire event for the required time duration.

    Issued in Renton, Washington, on June 19, 2014.
Michael Kaszycki,
Acting Manager, Transport Airplane Directorate.
[FR Doc. 2014-16645 Filed 7-15-14; 8:45 am]
BILLING CODE 4910-13-P