Document ID: FAA-2013-0892-0002
Agency: faa
Document Type: Rule
Title: Special Conditions: Airbus A350-900 Airplane; Crashworthiness, Emergency Landing Conditions
Posted Date: 2014-07-25T04:00Z

[Federal Register Volume 79, Number 143 (Friday, July 25, 2014)]
[Rules and Regulations]
[Pages 43237-43239]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2014-17574]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-2013-0892; Special Conditions No. 25-537-SC]

Special Conditions: Airbus A350-900 Airplane; Crashworthiness, 
Emergency Landing Conditions

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions.

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SUMMARY: These special conditions are issued for Airbus Model A350-900 
airplanes. These airplanes 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 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 Date: August 25, 2014.

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: 

Background

    On August 25, 2008, Airbus applied for a type certificate for their 
new Model A350-900 airplane. Later, Airbus requested, and the FAA 
approved, an extension to the application for FAA type certification to 
November 15, 2009. The Model A350-900 airplane 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 airplane configuration 
accommodates 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.
    Changes in the structural behavior of the Airbus Model A350-900 
airplane, compared to currently certificated designs, could degrade the 
survivability of the Model A350-900 airplane occupants in crash 
conditions that are within the limits of survivability for other 
designs.
    The airworthiness regulations specify no aircraft-level survivable 
crash condition, and metallic aircraft have not been designed 
specifically 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 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

[[Page 43238]]

assessment of the Model A350-900 airplane 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 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 airplane 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 airplane 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).

Novel or Unusual Design Features

    The Airbus Model A350-900 airplane incorporates the following novel 
or unusual design feature: A 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 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 
traditional metallic materials.
    No existing regulations adequately address this potential 
difference in impact-response characteristics for what are considered 
survivable crash conditions. The 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 
airplane has sufficient crashworthiness capabilities under foreseeable 
survivable impact events. To show this, Airbus should evaluate the 
impact-response characteristics of the Model A350-900 airplane to 
ensure that its crashworthiness characteristics are not significantly 
different from those of a similarly sized airplane built from 
traditional metallic materials.
    In their evaluation of the Model A350-900 airplane response to an 
impact event, Airbus should demonstrate that the structural behavior is 
similar to that expected from a metallic airframe of a size similar 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 Model A350-900 fuselage structure provides a level of occupant 
protection consistent with previously certificated large transport-
category airplanes.
    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. 25-13-21-SC for the 
Airbus Model A350-900 airplane was published in the Federal Register on 
January 8, 2014 (79 FR 1337). 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 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 airplane. 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

    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 airplanes.
    The Airbus Model A350-900 airplane must provide an equivalent level 
of occupant safety and survivability, to that provided by previously 
certificated wide-body transport-category airplanes of similar size, 
under foreseeable survivable impact events for the following four 
criteria. To demonstrate an equivalent level of occupant safety and 
survivability, the applicant must demonstrate that Model A350-900 
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 airplane yields load factors at the attach 
points that are comparable to those for a previously certificated wide-
body transport-category airplane.

[[Page 43239]]

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 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 transport-category airplanes 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-category airplane 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-category airplane, as 
determined following the same vertical-impact events.

    Issued in Renton, Washington, on July 9, 2014.
Jeffrey E. Duven,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 2014-17574 Filed 7-24-14; 8:45 am]
BILLING CODE 4910-13-P