[Federal Register Volume 79, Number 5 (Wednesday, January 8, 2014)]
[Proposed Rules]
[Pages 1337-1339]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2014-00104]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. FAA-2013-0892; Notice No. 25-13-21-SC]
Special Conditions: Airbus, A350-900 Series Airplane;
Crashworthiness--Emergency Landing Conditions
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Notice of proposed special conditions.
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SUMMARY: This action proposes special conditions for the Airbus Model
A350-900 series airplanes. These airplanes will have a novel or unusual
design feature associated with crashworthiness of carbon fiber
reinforced plastic used in the construction of the fuselage. 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
[[Page 1338]]
necessary to establish a level of safety equivalent to that established
by the existing airworthiness standards.
DATES: Send your comments on or before February 24, 2014.
ADDRESSES: Send comments identified by docket number FAA-2013-0892
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 9 a.m. and 5 p.m.,
Monday through Friday, except federal holidays.
Fax: Fax comments to Docket Operations at 202-493-2251.
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: Todd Martin, FAA, Airframe/Cabin
Safety, ANM-115, Transport Airplane Directorate, Aircraft Certification
Service, 1601 Lind Avenue SW., Renton, Washington, 98057-3356;
telephone (425) 227-1178; facsimile (425) 227-1320.
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 proposed 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 may change these proposed special conditions
based on the comments we receive.
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 XWB 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. Airbus proposes the
Model A350-900 series to be certified for extended operations (ETOPS)
beyond 180 minutes at entry into service for up to a 420-minute maximum
diversion time.
Changes in the structural behavior of the Airbus Model A350-900
series airplanes compared to currently certificated designs could
degrade the survivability of Model A350-900 series occupants in crash
conditions that are within the limits of survivability for other
designs.
There is no aircraft-level survivable crash condition specified in
the airworthiness regulations, and metallic aircraft have not been
specifically designed against survivable impact conditions. However,
the structural behavior of previously certificated aircraft in a
survivable crash event and the associated limits are considered
generally acceptable. It is therefore reasonable to expect that a
design using new materials, such as the Model A350-900 series airplanes
use, should be assessed to ensure that the material meets the currently
accepted level of safety. The FAA and industry have collected a
significant amount of experimental data as well as data from crashes of
transport category airplanes that show a high occupant survival rate at
vertical descent velocities up to 30 ft/sec. Based on this information,
the FAA finds it appropriate and necessary for an assessment of the
Model A350-900 series airplanes to span a range of airplane vertical
descent speeds up to 30 ft/sec.
Type Certification Basis
Under Title 14, Code of Federal Regulations (14 CFR) 21.17, Airbus
must show that the Model A350-900 series 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 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,
under Sec. 11.38, and they become part of the type-certification basis
under Sec. 21.17(a)(2).
Novel or Unusual Design Features
The Airbus Model A350-900 series will incorporate the following
novel or unusual design feature: fuselage fabricated with a combination
of carbon fiber reinforced plastic (CFRP) and metallic structure. This
is a novel and unusual design feature for a large transport airplane.
Structure fabricated from CFRP may behave differently than metallic
structure in crash conditions because of differences in material
ductility, stiffness, failure modes, and energy absorption
characteristics. Therefore, the impact response characteristics of the
Model A350-900 series airplane must be evaluated to ensure that its
survivable crashworthiness characteristics provide at least the same
level of safety as those of a similarly sized airplane constructed from
traditionally used metallic materials.
There are no existing regulations that adequately address this
potential difference in impact response
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characteristics for what are considered survivable crash conditions.
The proposed special conditions are necessary to ensure a level of
safety equivalent to that provided by 14 CFR part 25.
Discussion
Factors in crash survivability are retention of items of mass,
maintenance of occupant emergency egress paths, maintenance of
acceptable acceleration and loads experienced by the occupants, and
maintenance of a survivable volume. To provide the same level of safety
as exists with conventional airplane construction, Airbus should show
that the Model A350-900 series airplanes have sufficient
crashworthiness capabilities under foreseeable survivable impact
events. To show this, Airbus should evaluate the impact response
characteristics of the Model A350-900 series airplane to ensure that
its crashworthiness characteristics are not significantly different
from those of a similarly sized airplane built from traditionally used
metallic materials.
In their evaluation of the Model A350-900 series airplane response
to an impact event, Airbus should demonstrate that the structural
behavior is similar to that expected from a metallic airframe of
similar size to the Model A350-900, or incorporate mitigating design
features that provide a similar level of safety.
Airbus should demonstrate either through analysis using validated
analytical tools or by direct test evidence that the crash dynamics of
the A350 fuselage structure provides a level of occupant protection
consistent with previously certificated large transport category
airplanes.
Applicability
As discussed above, these proposed 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 proposed 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 Proposed Special Conditions
Accordingly, the Federal Aviation Administration (FAA) proposes the
following special conditions as part of the type certification basis
for Airbus Model A350-900 series airplanes.
The Airbus Model A350-900 series airplanes must provide an
equivalent level of occupant safety and survivability to that provided
by previously certificated wide-body transports of similar size under
foreseeable survivable impact events for the following four criteria.
In order to demonstrate an equivalent level of occupant safety and
survivability, the applicant must demonstrate that Model A350-900
series airplanes meet the following criteria for a range of airplane
vertical descent velocities up to 30 ft/sec.
1. Retention of items of mass. The occupants, i.e., passengers,
flight attendants, and flightcrew, must be protected during the impact
event from release of seats, overhead bins, and other items of mass due
to the impact loads and resultant structural deformation of the
supporting airframe and floor structures. The applicant must show that
loads due to the impact event and resultant structural deformation of
the supporting airframe and floor structure at the interface of the
airplane structure to seats, overhead bins, and other items of mass are
comparable to those of previously certificated wide-body transports of
similar size for the range of descent velocities stated above. The
attachments of these items need not be designed for static emergency
landing loads in excess of those defined in Sec. 25.561 if impact
response characteristics of the Airbus Model A350-900 series airplanes
yield load factors at the attach points that are comparable to those
for a previously certificated wide-body transport category airplane.
2. Maintenance of acceptable acceleration and loads experienced by
the occupants. The applicant must show that the impact response
characteristics of the Airbus Model A350-900 series airplane,
specifically the vertical acceleration levels experienced at the seat/
floor interface and loads experienced by the occupants during the
impact events, are consistent with those found in Sec. 25.562(b) or
with levels expected for a previously certificated wide-body transport
category airplane for the conditions stated above.
3. Maintenance of a survivable volume. For the conditions stated
above, the applicant must show that all areas of the airplane occupied
for takeoff and landing provide a survivable volume comparable to that
of previously certificated wide-body transports of similar size during
and after the impact event. This means that structural deformation will
not result in infringement of the occupants' normal living space so
that passenger survivability will not be significantly affected.
4. Maintenance of occupant emergency egress paths. The evacuation
of occupants must be comparable to that from a previously certificated
wide-body transport of similar size. To show this, the applicant must
show that the suitability of the egress paths, as determined following
the vertical impact events, is comparable to the suitability of the
egress paths of a comparable, certificated wide-body transport, as
determined following the same vertical impact events.
Issued in Renton, Washington, on October 22, 2013.
Stephen P. Boyd,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 2014-00104 Filed 1-7-14; 8:45 am]
BILLING CODE 4910-13-P