[Federal Register Volume 76, Number 87 (Thursday, May 5, 2011)]
[Proposed Rules]
[Pages 25648-25650]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2011-10922]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM454 Special Conditions No. 25-11-11-SC]


Special Conditions: Gulfstream Model GVI Airplane; Limit Engine 
Torque Loads for Sudden Engine Stoppage

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed special conditions.

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SUMMARY: This action proposes special conditions for the Gulfstream GVI 
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. These design features 
include

[[Page 25649]]

engine size and the potential torque load imposed by sudden engine 
stoppage. These proposed special conditions pertain to their effects on 
the structural performance of the airplane. The applicable 
airworthiness regulations do not contain adequate or appropriate safety 
standards for these design features. 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: We must receive your comments by June 20, 2011.

ADDRESSES: You must mail two copies of your comments to: Federal 
Aviation Administration, Transport Airplane Directorate, Attn: Rules 
Docket (ANM-113), Docket No. NM454, 1601 Lind Avenue SW., Renton, 
Washington 98057-3356. You may deliver two copies to the Transport 
Airplane Directorate at the above address. You must mark your comments: 
Docket No. NM454. You can inspect comments in the Rules Docket 
weekdays, except Federal holidays, between 7:30 a.m. and 4 p.m.

FOR FURTHER INFORMATION CONTACT: Carl Niedermeyer, FAA, Airframe/Cabin 
Safety Branch, ANM-115, Transport Standards Staff, Transport Airplane 
Directorate, Aircraft Certification Service, 1601 Lind Avenue SW., 
Renton, Washington 98057-3356; telephone (425) 227-2279; electronic 
mail [email protected].

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 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 special conditions. You can inspect the docket 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 preamble 
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 
these special conditions based on the comments we receive.
    If you want us to acknowledge receipt of your comments on this 
proposal, include with your comments a self-addressed, stamped postcard 
on which you have written the docket number. We will stamp the date on 
the postcard and mail it back to you.

Background

    On March 29, 2005, Gulfstream Aerospace Corporation (hereafter 
referred to as ``Gulfstream'') applied for an FAA type certificate for 
its new Gulfstream Model GVI passenger airplane. Gulfstream later 
applied for, and was granted, an extension of time for the type 
certificate, which changed the effective application date to September 
28, 2006. The Gulfstream Model GVI airplane will be an all-new, two-
engine jet transport airplane with an executive cabin interior. The 
maximum takeoff weight will be 99,600 pounds, with a maximum passenger 
count of 19 passengers.

Type Certification Basis

    Under provisions of Title 14, Code of Federal Regulations (14 CFR) 
21.17, Gulfstream must show that the Gulfstream Model GVI airplane 
(hereafter referred to as ``the GVI'') meets the applicable provisions 
of 14 CFR part 25, as amended by Amendments 25-1 through 25-119, 25-
122, and 25.124. 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 GVI because of a novel 
or unusual design feature, special conditions are prescribed under the 
provisions of 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 novel or 
unusual design features, the special conditions would also apply to the 
other model under provisions of Sec.  21.101.
    In addition to complying with the applicable airworthiness 
regulations and special conditions, the GVI 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 also issue a 
finding of regulatory adequacy pursuant to 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, in 
accordance with Sec.  11.38, and they become part of the type 
certification basis under Sec.  21.17(a)(2).

Novel or Unusual Design Features

    The GVI will have high bypass engines. Engines of this size, 
configuration, and failure modes were not envisioned when Sec.  25.361, 
which addresses loads imposed by engine seizure, was adopted in 1965. 
Worst case engine seizure events have become increasingly more severe 
with increasing engine size because of the higher inertia of the 
rotating components. The GVI engines are sufficiently different and 
novel to justify issuance of a special condition to establish 
appropriate design standards.

Discussion of Proposed Special Conditions

    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 
supporting structures should remain serviceable after a limit load 
event.
    Since 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, Aviation Rulemaking Advisory Committee (ARAC) 
has proposed a design standard for today's large engines. For the 
commonly-occurring deceleration events, the proposed standard would 
require engine mounts and structures to support maximum torques without 
detrimental permanent deformation. For the rare-but-severe engine 
seizure events such as loss of any fan, compressor, or turbine blade, 
the proposed standard would require engine mounts and structures to 
support maximum torques

[[Page 25650]]

without failure, but allows for some deformation in the structure.
    The FAA concludes that modern large engines, including those on the 
GVI, are novel and unusual compared to those envisioned when Sec.  
25.361(b)(1) was adopted and thus warrant special conditions. The 
proposed special conditions contain design criteria recommended by 
ARAC. The proposed special conditions also clarify the design criteria 
that apply to auxiliary power units.

Applicability

    As discussed above, these proposed special conditions are 
applicable to the GVI. Should Gulfstream 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 proposed special 
conditions would apply to that model as well.

Conclusion

    This action affects only certain novel or unusual design features 
of the GVI. 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 the GVI airplanes.
    In lieu of Sec.  25.361(b) the following special conditions are 
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 which could 
result in a temporary loss of power or thrust; and
    (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
    (b) Separately, 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. Any permanent deformation that results from the conditions 
specified in paragraph 3 must not prevent continued safe flight and 
landing.

    Issued in Renton, Washington, on April 20, 2011.
KC Yanamura,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 2011-10922 Filed 5-4-11; 8:45 am]
BILLING CODE 4910-13-P