Document ID: FAA-2013-0897-0001
Agency: faa
Document Type: Proposed Rule
Title: Special Conditions: Airbus, Model A350-900 Series Airplane; Transient Engine Failure Loads
Posted Date: 2013-11-12T05:00Z

[Federal Register Volume 78, Number 218 (Tuesday, November 12, 2013)]
[Proposed Rules]
[Pages 67323-67324]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2013-26911]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-2013-0897; Notice No. 25-13-29-SC]

Special Conditions: Airbus, Model A350-900 Series Airplane; 
Transient Engine Failure Loads

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed special conditions.

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SUMMARY: This action proposes special conditions for Airbus Model A350-
900 series airplanes. These airplanes will have a novel or unusual 
design feature associated with the new generation of high bypass 
engines and the potential loads resulting from extreme engine failure 
conditions.
    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 necessary to establish a level of safety 
equivalent to that established by the existing airworthiness standards.

DATES: Send your comments on or before December 27, 2013.

ADDRESSES: Send comments identified by docket number FAA-2013-0897 
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, International 
Branch, 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 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 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. 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.
    The existing regulations are inadequate because the new, large 
bypass fan engines of the Model A350-900 series airplanes can cause 
more damage in a failure event than the previous engines. To maintain 
the level of safety envisioned by Title 14, Code of Federal Regulations 
(14 CFR) 25.61(b), more comprehensive criteria are needed for the new 
generation of high bypass engines. The more severe events resulting 
from extreme engine failure conditions would be treated as dynamic load 
conditions. The proposed special conditions would distinguish between 
the more common engine failure events and those rare events resulting 
from structural failures. The more common events would continue to be 
treated as static torque limit load conditions. The severe events would 
be considered ultimate loads, and include all transient loads 
associated with the event. An additional safety factor would be applied 
to the more critical airframe supporting structure.

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-
128.
    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 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 proposed special conditions would 
also apply to the other model under Sec.  21.101.
    In addition to the applicable airworthiness regulations and 
proposed special conditions, the Model A350-900

[[Page 67324]]

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 
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, 
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 Model A350-900 series airplane will incorporate the following 
novel or unusual design features: Engines with large, bypass fans 
capable of producing much higher failure loads than previous engines. 
The Model A350-900 will therefore require additional dynamic loads 
analyses to assess the most severe engine failure events. The loads 
resulting from these conditions would be considered as ultimate loads, 
with an additional safety factor applied to the airframe supporting 
structure.

Discussion

    The size, configuration, and failure modes of jet engines has 
changed considerably from those envisioned by Title 14 Code of Federal 
Regulations (14 CFR) 25.361(b) when the engine seizure requirement was 
first adopted. Engines have become larger and are now designed with 
large bypass fans capable of producing much higher failure loads. 
Relative to the engine configurations that existed when the rule was 
developed in 1957, the present generation of engines are sufficiently 
different and novel to justify special conditions for Model A350-900 
series airplanes. Service history has shown that the engine failure 
events that tend to cause the most severe loads are fan blade failures 
and these events occur much less frequently than the typical ``limit'' 
load condition.
    The regulatory authorities and industry developed a standardized 
requirement in the Aviation Rulemaking Advisory Committee (ARAC) forum. 
The technical aspects of this requirement have been agreed and have 
been accepted by the ARAC Loads and Dynamics Harmonization Working 
Group. The proposed special condition reflects the ARAC recommendation 
and is essentially harmonized with the corresponding EASA Certification 
Specifications (CS) 25. In addition, the ARAC recommendation includes 
corresponding advisory material that is incorporated in CS-25. This 
advisory material is considered an acceptable means of compliance to 
the proposed special conditions.

Applicability

    As discussed above, these proposed special conditions apply to the 
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 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 proposed 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.
    In lieu of Sec.  25.361(b) the following special condition is 
proposed:
    1. For turbine engine installations, the engine mounts, pylons, and 
adjacent supporting airframe structure must be designed to withstand 1g 
level flight loads acting simultaneously with the maximum limit torque 
loads imposed by each of the following:
    a. sudden engine deceleration due to a malfunction that could 
result in a temporary loss of power or thrust,
    b. the maximum acceleration of the engine.
    2. For auxiliary power unit installations, the power unit mounts 
and adjacent supporting airframe structure must be designed to 
withstand 1g level flight loads acting simultaneously with the maximum 
limit torque loads imposed by each of the following:
    a. sudden auxiliary power unit deceleration due to malfunction or 
structural failure; and
    b. the maximum acceleration of the power unit.
    3. For engine supporting structure, an ultimate loading condition 
must be considered that combines 1g flight loads with the transient 
dynamic loads resulting from:
    a. the loss of any fan, compressor, or turbine blade; and 
separately
    b. where applicable to a specific engine design, any other engine 
structural failure that results in higher loads.
    4. The ultimate loads developed from the conditions specified in 
paragraphs 3.a. and 3.b. are to be multiplied by a factor of 1.0 when 
applied to engine mounts and pylons and multiplied by a factor of 1.25 
when applied to adjacent supporting airframe structure.
    5. The airplane must be capable of continued safe flight 
considering the aerodynamic effects on controllability due to any 
permanent deformation that results from the conditions specified in 3.

    Issued in Renton, Washington, on October 22, 2013.
Stephen P. Boyd,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 2013-26911 Filed 11-8-13; 8:45 am]
BILLING CODE 4910-13-P