Special Conditions: Airbus Model A350-900 Series Airplane; Composite Fuselage In-Flight Fire/Flammability Resistance, 33677-33679 [2014-13665]

Agencies

• Federal Aviation Administration
• DEPARTMENT OF TRANSPORTATION

[Federal Register Volume 79, Number 113 (Thursday, June 12, 2014)]
[Rules and Regulations]
[Pages 33677-33679]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2014-13665]


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

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-2013-0898 Special Conditions No. 25-526-SC]


Special Conditions: Airbus Model A350-900 Series Airplane; 
Composite Fuselage In-Flight Fire/Flammability Resistance

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions.

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

SUMMARY: These special conditions are issued for Airbus Model A350-900 
series airplanes. These airplanes will have a novel or unusual design 
feature associated with the in-flight fire and flammability resistance 
of the composite fuselage. Experience has shown that eliminating fire 
propagation on the surface of interior and insulating materials 
enhances survivability since the threats from an in-flight fire (e.g., 
toxic gas emission and smoke

[[Page 33678]]

obscuration) are typically by-products of a propagating fire. The 
Airbus Model A350-900 series airplanes must provide protection against 
an in-flight fire propagating along the surface of the fuselage. 
Special conditions are needed to address this design feature. 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: Effective July 14, 2014.

FOR FURTHER INFORMATION CONTACT: Jeff Gardlin, FAA, Airframe/Cabin 
Safety, ANM-115, Transport Airplane Directorate, Aircraft Certification 
Service, 1601 Lind Avenue SW., Renton, Washington, 98057-3356; 
telephone (425) 227-2136; facsimile (425) 227-1320.

SUPPLEMENTARY INFORMATION:

Background

    On August 25, 2008, Airbus applied for a type certificate for their 
new Model A350-900 series airplane. Later, Airbus requested and the FAA 
approved an extension to the application for FAA type certification to 
June 28, 2009. The Model A350-900 series has a conventional layout with 
twin wing-mounted Rolls Royce Trent engines. It features a twin aisle 
9-abreast economy class layout, and accommodates side-by-side placement 
of LD-3 containers in the cargo compartment. The basic Model A350-900 
series configuration will accommodate 315 passengers in a standard two-
class arrangement. The design cruise speed is Mach 0.85 with a Maximum 
Take-Off Weight of 602,000 lbs.
    Experience has shown that eliminating fire propagation on the 
surface of interior and insulating materials enhances survivability 
since the threats from an in-flight fire (e.g., toxic gas emission and 
smoke obscuration) are typically by-products of a propagating fire. The 
Airbus Model A350-900 series airplane must provide protection against 
an in-flight fire propagating along the surface of the fuselage.
    In the past, fatal in-flight fires have originated in inaccessible 
areas of the aircraft where the thermal/acoustic insulation located 
adjacent to the aluminium aircraft skin has been the path for flame 
propagation and fire growth. Concern over the fire performance of 
thermal/acoustic insulation was initially raised by five incidents in 
the 1990's which revealed unexpected flame spread along the insulation 
film covering material. In all cases, the ignition source was 
relatively modest and, in most cases, was electrical in origin (e.g., 
electrical short circuit, arcing caused by chafed wiring, ruptured 
ballast case). From 1972 until 2003 these materials were required to 
comply with a basic ``Bunsen burner'' requirement per Title 14 Code of 
Federal Regulations (14 CFR) 25.853(a), 25.855(d), and part 25, 
Appendix F, part I, paragraph (a)(1)(ii). These requirements prescribed 
that insulation materials must be self-extinguishing after having been 
subjected to the flame of a Bunsen burner for 12 seconds, in accordance 
with the procedures defined in part 25, Appendix F, part I, paragraph 
(b)(4). The average burn was not to exceed eight inches and the average 
flame time after removal of the flame source was not to exceed 15 
seconds. Drippings from the test specimen were not to continue to flame 
for more than an average of five seconds after falling.
    Further concern with the flammability of thermal/acoustic 
insulation was raised by the Transportation Safety Board (TSB) of 
Canada during their investigation of the fatal Swiss Air MD-11 in-
flight fire accident that occurred in September 1998 and involved 229 
fatalities. TSB investigators reported that the fatal fire appeared to 
have been confined to the area above the cockpit and forward cabin 
ceiling and involved the insulation blankets. On August 21, 2001, the 
TSB recommended that flammability standards for interior materials 
should be based on realistic ignition scenarios and prevent the use of 
materials that sustain or propagate a fire.
    In 1996, the FAA Technical Center began a program to develop new 
fire test criteria for insulation films directly relating to the 
resistance of in-flight fire propagation. The current test standard was 
evaluated as well as another small-scale test method that has been used 
by airplane manufacturers to evaluate flame propagation on thermal/
acoustic insulation materials. An inter-laboratory comparison of these 
methods revealed a number of deficiencies. Other small-scale tests 
developed by the FAA Technical Center did demonstrate that some 
insulation films would ignite and propagate flame in a confined space. 
As a result, a series of large-scale fire tests were conducted in a 
mock-up of the attic area above the passenger cabin ceiling. In a 
confined space, ignition and flame propagation may occur because of 
more extensive radiating heat and the trapping of melted film/scrim. 
Temperature (heat release) data was recorded and the degree of flame 
propagation was observed from the large-scale tests. A radiant panel 
test standard for flooring materials was a test method that provided 
good correlation to the large-scale model. The test method involved 
subjecting a material to a pilot flame while the material is heated by 
a radiant panel.
    The previously described development program resulted in a new test 
method (radiant panel test) and test criteria specifically established 
for improving the in-flight fire ignition/flame propagation of thermal/
acoustic insulation materials. A new part 25 airworthiness standard, 
Sec.  25.856, became effective in September 2003, Amendment 25-111, 
requiring that all thermal/acoustic insulation materials installed in 
the fuselage must comply to this flammability and flame propagation 
requirement. The standards are intended to ``reduce the incidence and 
severity of cabin fires, particularly those ignited in inaccessible 
areas where thermal acoustic insulation materials are typically 
installed.''

Type Certification Basis

    Under Title 14, Code of Federal Regulations (14 CFR) 21.17, Airbus 
must show that the Model A350-900 series airplane meets 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 Model A350-900 series because of a 
novel or unusual design feature, special conditions are prescribed 
under 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 Model A350-900 series 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 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, 
under Sec.  11.38, and they become part of the type-certification basis 
under Sec.  21.17(a)(2).

[[Page 33679]]

Novel or Unusual Design Features

    The Airbus Model A350-900 series airplane incorporates the 
following novel or unusual design features: Fuselage fabricated with 
composite materials.

Discussion

    The Airbus Model A350-900 series airplane makes extensive use of 
composite materials in the fabrication of the majority of the wing, 
fuselage skin, stringers, spars, and most other structural elements of 
all major sub-assemblies of the airplane. Despite the major change from 
aluminum to composite material for the fuselage, the Model A350-900 
series must have in-flight survivability such that the composite 
fuselage does not propagate a fire. A methodology for assessing the in-
flight fire survivability of an all-composite fuselage is therefore 
needed.
    The FAA believes that one way to assess the survivability within 
the cabin of the Model A350-900 series airplane is to conduct large-
scale tests. This large-scale test would utilize a mock-up of an Airbus 
Model A350-900 series airplane fuselage skin/structure section of 
sufficient size to assess any tendency for fire propagation. The fire 
threat used to represent the realistic ignition source in the airplane 
would consist of a 4'' x 4'' x 9'' polyurethane foam block and 10 ml of 
Heptane. This ignition source provides approximately three minutes of 
flame time and would be positioned at various points and orientations 
within the mocked up installation to impinge on those areas of the 
fuselage considered to be most crucial.
    This fire threat was established based on an assessment of a range 
of potential ignition sources, coupled with possible contamination of 
materials. The FAA considers this a severe fire threat, encompassing a 
variety of scenarios. However, should ignition or fire sources of a 
greater severity be identified, the special condition or its method of 
compliance would need to be modified in order to take the more severe 
threat into account.
    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.

Discussion of Comments

    Notice of proposed special conditions No. 25-13-33-SC for the 
Airbus Model A350-900 series airplanes was published in the Federal 
Register on November 15, 2013 (78FR68775). No comments were received, 
and the special conditions are adopted as proposed.

Applicability

    As discussed above, these special conditions apply to Airbus Model 
A350-900 series airplanes. Should Airbus apply later 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 the Airbus Model A350-900 series 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 Special Conditions

0
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 Airbus Model A350-900 series 
airplanes.

Composite Fuselage In-Flight Fire/Flammability Resistance

    In addition to the requirements of Sec.  25.853(a) governing 
material flammability, the following special condition applies:
    The Airbus Model A350 composite fuselage structure must be shown to 
be resistant to flame propagation under the fire threat used to develop 
Sec.  25.856(a). If products of combustion are observed beyond the test 
heat source, they must be evaluated and found acceptable.

    Issued in Renton, Washington, on: April 22, 2014.
Jeffrey E. Duven,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 2014-13665 Filed 6-11-14; 8:45 am]
BILLING CODE 4910-13-P