[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