Special Conditions: Airbus Model A380-800 Airplane, Transient Engine Failure Loads, 46104-46106 [05-15654]

Agencies

• Federal Aviation Administration
• DEPARTMENT OF TRANSPORTATION

[Federal Register Volume 70, Number 152 (Tuesday, August 9, 2005)]
[Proposed Rules]
[Pages 46104-46106]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 05-15654]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM322; Notice No. 25-05-17-SC]


Special Conditions: Airbus Model A380-800 Airplane, Transient 
Engine Failure Loads

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed special conditions.

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SUMMARY: This notice proposes special conditions for the Airbus A380-
800 airplane. This airplane will have novel or unusual design features 
when compared to the state of technology envisioned in the 
airworthiness standards for transport category airplanes. Some of these 
novel or unusual design features are associated with the high bypass 
engines used on the Model A380. For these design features, the 
applicable airworthiness regulations do not contain adequate or 
appropriate safety standards regarding transient engine failure loads. 
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. Additional special conditions will be issued 
for other novel or unusual design features of the Airbus Model A380-800 
airplane.

DATES: Comments must be received on or before September 23, 2005.

ADDRESSES: Comments on this proposal may be mailed in duplicate to: 
Federal Aviation Administration, Transport Airplane Directorate, 
Attention: Rules Docket (ANM-113), Docket No. NM322, 1601 Lind Avenue 
SW., Renton, Washington 98055-4056; or delivered in duplicate to the 
Transport Airplane Directorate at the above address. All comments must 
be marked: Docket No. NM322. Comments may be inspected in the Rules 
Docket weekdays, except Federal holidays, between 7:30 a.m. and 4 p.m.

FOR FURTHER INFORMATION CONTACT: Holly Thorson, FAA, International 
Branch, ANM-116, Transport Airplane

[[Page 46105]]

Directorate, Aircraft Certification Service, 1601 Lind Avenue SW., 
Renton, Washington 98055-4056; telephone (425) 227-1357; facsimile 
(425) 227-1149.

SUPPLEMENTARY INFORMATION:

Comments Invited

    The FAA invites interested persons to participate in this 
rulemaking by submitting 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 ask that you send us two copies of written 
comments.
    We will file in the docket all comments we receive as well as a 
report summarizing each substantive public contact with FAA personnel 
concerning these proposed special conditions. The docket is available 
for public inspection before and after the comment closing date. If you 
wish to review the docket in person, go to the address in the ADDRESSES 
section of this notice between 7:30 a.m. and 4 p.m., Monday through 
Friday, except Federal holidays.
    We will consider all comments we receive on or before the closing 
date for comments. We will consider comments filed late, if it is 
possible to do so without incurring expense or delay. We may change the 
proposed special conditions in light of the comments we receive.
    If you want the FAA to acknowledge receipt of your comments on this 
proposal, include with your comments a pre-addressed, stamped postcard 
on which the docket number appears. We will stamp the date on the 
postcard and mail it back to you.

Background

    Airbus applied for FAA certification/validation of the 
provisionally-designated Model A3XX-100 in its letter AI/L 810.0223/98, 
dated August 12, 1998, to the FAA. Application for certification by the 
Joint Aviation Authorities (JAA) of Europe had been made on January 16, 
1998, reference AI/L 810.0019/98. In its letter to the FAA, Airbus 
requested an extension to the 5-year period for type certification in 
accordance with 14 CFR 21.17(c). The request was for an extension to a 
7-year period, using the date of the initial application letter to the 
JAA as the reference date. The reason given by Airbus for the request 
for extension is related to the technical challenge, complexity, and 
the number of new and novel features on the airplane. On November 12, 
1998, the Manager, Aircraft Engineering Division, AIR-100, granted 
Airbus' request for the 7-year period, based on the date of application 
to the JAA.
    In its letter AI/LE-A 828.0040/99 Issue 3, dated July 20, 2001, 
Airbus stated that its target date for type certification of the Model 
A380-800 has been moved from May 2005, to January 2006, to match the 
delivery date of the first production airplane. In accordance with 14 
CFR 21.17(d)(2), Airbus chose a new application date of April 20, 1999, 
and requested that the 7-year certification period which had already 
been approved be continued. The part 25 certification basis for the 
Model A380-800 airplane was adjusted to reflect the new application 
date.
    The Model A380-800 airplane will be an all-new, four-engine jet 
transport airplane with a full-length double-deck, two-aisle cabin. The 
maximum takeoff weight will be 1.235 million pounds with a typical 
three-class layout of 555 passengers.

Type Certification Basis

    Under the provisions of 14 CFR 21.17, Airbus must show that the 
Model A380-800 airplane meets the applicable provisions of 14 CFR part 
25, as amended by Amendments 25-1 through 25-98. If the Administrator 
finds that the applicable airworthiness regulations do not contain 
adequate or appropriate safety standards for the Airbus A380-800 
airplane because of novel or unusual design features, special 
conditions are prescribed under the provisions of 14 CFR 21.16.
    In addition to the applicable airworthiness regulations and special 
conditions, the Airbus Model A380-800 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. In addition, the 
FAA must issue a finding of regulatory adequacy pursuant to section 611 
of Public Law 93-574, the ``Noise Control Act of 1972.''
    Special conditions, as defined in 14 CFR 11.19, are issued in 
accordance with 14 CFR 11.38 and become part of the type certification 
basis in accordance with 14 CFR 21.17(a)(2), Amendment 21-69, effective 
September 16, 1991.
    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 novel or 
unusual design feature, or should any other model already included on 
the same type certificate be modified to incorporate the same novel or 
unusual design features, the special conditions would also apply to the 
other model under the provisions of 14 CFR 21.101.

Discussion of Novel or Unusual Design Features

    The Model A380 will have very large high bypass ratio engines with 
110 inch diameter bypass fans, representing the latest in a trend 
toward increasing engine size. Engines of this size were not envisioned 
when Sec.  25.361'pertaining to loads imposed by engine seizure'was 
adopted in 1965. Worst case engine seizure events become increasingly 
more severe with increasing engine size because of the higher inertia 
of the rotating components.
    Section 25.361(b)(1) requires that for turbine engine 
installations, the engine mounts and the supporting structures must be 
designed to withstand a ``limit engine torque load imposed by sudden 
engine stoppage due to malfunction or structural failure.'' Limit loads 
are expected to occur about once in the lifetime of any airplane. 
Section 25.305 requires that supporting structures be able to support 
limit loads without detrimental permanent deformation, meaning that the 
supporting structures should remain serviceable after a limit load 
event.
    Since the adoption of Sec.  25.361(b)(1), the size, configuration, 
and failure modes of jet engines have changed considerably. Current 
engines are much larger and are designed with large bypass fans. In the 
event of a structural failure, these engines are capable of producing 
much higher transient loads on the engine mounts and supporting 
structures.
    As a result, modern high bypass engines are subject to certain 
rare-but-severe engine seizure events. Service history shows that such 
events occur far less frequently than limit load events. Although it is 
important for the airplane to be able to support such rare loads safely 
without failure, it is unrealistic to expect that no permanent 
deformation will occur.
    Given this situation, the Aviation Rulemaking Advisory Committee 
(ARAC) has proposed a design standard for today's large engines. For 
the commonly-occurring deceleration events, the proposed standard 
requires engine mounts and structures to support maximum torques 
without detrimental permanent deformation. For the rare-but-severe 
engine seizure events (i.e., loss of any fan, compressor, or turbine 
blade), the proposed standard requires engine mounts and structures to 
support maximum torques without failure, but

[[Page 46106]]

allows for some deformation in the structure.
    The FAA concludes that modern large engines, including those on the 
Model A380, are novel and unusual compared to those envisioned when 
Sec.  25.361(b)(1) was adopted and thus warrant a special condition. 
The proposed special condition contains design criteria as recommended 
by the ARAC.
    The ARAC proposal would revise the wording of Sec.  25.361(b), 
including Sec. Sec.  25.361(b)(1) and (b)(2), removing the language 
pertaining to structural failures and moving it to a separate 
requirement that discusses the reduced factors of safety that apply to 
these failures. The revised wording of Sec.  25.361(b) would also 
include non-substantive changes recommended by ARAC to clarify the 
existing requirement. The FAA is using this ARAC text in the proposed 
special condition, because it clarifies the supplementary conditions 
for engine torque.

Applicability

    As discussed above, these special conditions are applicable to the 
Airbus A380-800 airplane. Should Airbus apply at a later date for a 
change to the type certificate to include another model incorporating 
the same novel or unusual design features, these special conditions 
would apply to that model as well under the provisions of Sec.  
21.101(a)(1), Amendment 21-69, effective September 16, 1991.

Conclusion

    This action affects only certain novel or unusual design features 
of the Airbus A380-800 airplane. It is not a rule of general 
applicability, and it affects only the applicant which applied to the 
FAA for approval of these features on the airplane.

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, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration (FAA) proposes the 
following special conditions as part of the type certification basis 
for the Airbus A380-800 airplane.
    a. In lieu of compliance with Sec.  25.361(b), the following 
special condition applies:
    For turbine engine installations, the engine mounts, pylons, and 
adjacent supporting airframe structure must be designed to withstand 1 
g level flight loads acting simultaneously with the maximum limit 
torque loads imposed by each of the following:
    1. Sudden engine deceleration due to a malfunction which could 
result in a temporary loss of power or thrust; and
    2. The maximum acceleration of the engine.
    b. In addition to the requirements of 14 CFR part 25, the following 
special condition applies:
    1. For engine supporting structure, an ultimate loading condition 
must be considered that combines 1 g flight loads with the transient 
dynamic loads resulting from:
    (a) The loss of any fan, compressor, or turbine blade; and
    (b) Separately, where applicable to a specific engine design, any 
other engine structural failure that results in higher loads.
    2. The ultimate loads developed from the conditions specified in 
paragraph b. 1. above are to be:
    (a) multiplied by a factor of 1.0 when applied to engine mounts and 
pylons; and
    (b) multiplied by a factor of 1.25 when applied to adjacent 
supporting airframe structure.

    Issued in Renton, Washington, on August 1, 2005.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 05-15654 Filed 8-8-05; 8:45 am]
BILLING CODE 4910-13-P