[Federal Register Volume 59, Number 131 (Monday, July 11, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-16678]
[[Page Unknown]]
[Federal Register: July 11, 1994]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 33
[Docket No. 94-ANE-18; Notice No. 33-08]
Special Conditions; General Electric Aircraft Engines Model(s)
GE90-75B/-85B/-76B Turbofan Engines
AGENCY: Federal Aviation Administration, DOT.
ACTION: Notice of proposed special conditions.
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SUMMARY: This document proposes special conditions for the General
Electric (GE) Aircraft Engines Model(s) GE90-75B/-85B/-76B turbofan
engines. The Federal Aviation Administration (FAA) has determined that
the requirements of Federal Aviation Regulation (FAR) 14 CFR part 33,
including the requirements of Sec. 33.94, Blade Containment and Rotor
Unbalance Test, relative to the location of fan blade fracture for the
containment test, do not contain adequate or appropriate safety
standards for the certification of the GE90-75B/-85B/-76B turbofan
engines. This finding is based on a novel or unusual design feature of
the GE90 fan blade. Therefore, this document proposes special
conditions which the Administrator finds necessary to establish a level
of safety equivalent to that established by the airworthiness standards
of part 33 of the FAR.
DATES: Comments must be submitted on or before August 25, 1994.
ADDRESSES: Comments on this proposal may be submitted in triplicate to:
Federal Aviation Administration (FAA), New England Region, Office of
the Assistant Chief Counsel, Attn: Rules Docket No. 94-ANE-18, 12 New
England Executive Park, Burlington, Massachusetts 01803-5299. Comments
must be marked: Docket No. 94-ANE-18. Comments may be inspected at this
location between 8 a.m. and 4:30 p.m., Monday through Friday, except
Federal holidays.
FOR FURTHER INFORMATION CONTACT:
Tim Mouzakis, Engine and Propeller Standards Staff, ANE-110, Engine and
Propeller Directorate, Aircraft Certification Service, FAA, New England
Region, 12 New England Executive Park, Burlington, MA 01803-5229;
telephone (617) 238-7114; fax (617) 238-7199.
SUPPLEMENTARY INFORMATION:
Comments Invited
Interested persons are invited to participate in the making of the
proposed special conditions by submitting such written data, views, or
arguments as they may desire. Communications should identify the Rules
Docket number and be submitted in triplicate to the address specified
under ADDRESSES. All communications received on or before the closing
date for comments, specified under DATES, will be considered by the
Administrator before taking action on the proposal. The proposal
contained in this notice may be changed in light of the comments
received.
Comments are specifically invited on the overall regulatory,
economic, environmental, and energy aspects of the proposed special
conditions. All comments submitted will be available in the Rules
Docket for examination by interested persons, both before and after the
closing date for comments. A report summarizing each substantive public
contact with FAA personnel concerning this proposal will be filed in
the docket.
Commenters wishing the FAA to acknowledge receipt of their comments
submitted in response to this notice must submit with those comments a
self-addressed, stamped postcard on which the following statement is
made: ``Comments to Docket No. 94-ANE-18.'' The postcard will be date
stamped and returned to the commenter.
Background
On December 16, 1991, General Electric Aircraft Engines applied for
type certification of Model(s) GE90-75B/-85B/-76B turbofan engines.
These engines incorporate a first stage fan blade manufactured using
carbon graphite composite material. This unusual design feature results
in the GE90 fan blade having significant difference in material
property characteristics when compared to conventionally designed fan
blades using non-composite materials. For example, the probability that
a composite fan blade will fail below the inner flowpath diameter is
highly improbable, making inappropriate the requirement contained in
Sec. 33.94 paragraph (a) subparagraph (1) to show blade containment
after a failure of the blade at the outermost retention feature.
The current requirements of Sec. 33.94 are based on metallic blade
characteristics and service history and are not appropriate for the
unusual design features of the composite fan blade found on the GE90
series turbofan engines. The FAA has determined that a more realistic
blade retention test will be achieved with a fan blade failure at the
inner flowpath diameter (complete airfoil) instead of the outermost
retention feature as is currently required by Sec. 33.94 paragraph (a)
subparagraph (1).
The FAA has also determined that the composite fan blade
construction presents other factors that must be considered. Tests and
analyses must account for the effects of in-service deterioration of,
manufacturing and materials variations in, and environmental effects on
the composite material. Further, tests and analyses must show that a
lightning strike on the composite fan blade will not result in a
hazardous condition to the aircraft and that the engine will meet the
requirements of Sec. 33.75. Therefore, these Special Conditions are
proposed which define the additional requirements which the
Administrator considers necessary to establish a level of safety
equivalent to that established by the Airworthiness Standards of part
33.
Type Certification Basis
Under the provisions of Sec. 21.101, General Electric Aircraft
Engines must show that the GE Model(s) GE90-75B/-85B/-76B turbofan
engines met the requirements of the applicable regulations in effect on
the date of the application. Those Federal Aviation Regulations are
Sec. 21.21, as amended through Amendment 21-68, August 10, 1990, and
part 33, as amended through Amendment 33-14, August 10, 1990.
The Administrator finds that the applicable airworthiness
regulations in part 33, as amended, do not contain adequate or
appropriate safety standards for the GE90 series turbofan engine
because of its novel or unusual design feature. Therefore, the
Administrator proposes these special conditions under the provisions of
Sec. 21.16 to establish a level of safety equivalent to that
established in the regulations.
Special conditions, as appropriate, are issued in accordance with
Sec. 11.49 of the FAR after public notice and opportunity for comment,
as required by Sec. 11.28 and Sec. 11.29(b), and become part of the
type certification basis in accordance with Sec. 21.101 paragraph (b)
subparagraph (2).
Conclusion
This action affects only GE Model(s) GE90-75B/-85B/-76B turbofan
engines. It is not a rule of general applicability and affects only the
manufacturer who applied to the FAA for approval of these engines
containing this novel or unusual design feature.
List of Subjects in 14 CFR Part 33
Air transportation, Aircraft, Aviation safety, safety.
The authority citation for these special conditions continues to
read as follows:
Authority: 49 U.S.C. App. 1354(a), 1421, 1423; 49 U.S.C. 106(g);
14 CFR 21.16, and 14 CFR 11.28.
The Proposed Special Conditions
Accordingly, the Federal Aviation Administration (FAA) proposes the
following special conditions as part of the type certification basis
for the General Electric Aircraft Engines GE90 series turbofan engines.
(a) The following must be shown by tests and analyses, or other
methods acceptable to the Administrator, that, in lieu of the fan blade
containment test with the fan blade failing at the point specified in
Sec. 33.94 paragraph (a) subparagraph (1), a fan blade containment test
with the fan blade failing at the inner flowpart diameter demonstrates:
(1) That the disk and fan blade retention system can withstand
without failure a centrifugal load equal to two times the maximum load
which the engine could experience within approved operating
limitations, and
(2) That by a procedure approved by the Administrator an operating
limitation must be established which specifies the maximum allowable
number of start-stop stress cycles for the fan blade retention system.
The fan blade retention system includes the portion of the fan blade
from the inner flowpath diameter inward to the blade dovetail, the
blade retention components, and the fan disk and fan blade attachment
features.
(b) It must be shown that the probability of fan blade retention
system failure, for any cause, during the service life of the engine to
be extremely improbable.
(c) It must be shown by test or analysis that a lightning strike on
the composite fan blade structure will not result in a hazardous
condition, and that the engine will meet the requirements of
Sec. 33.75.
(d) The tests and analyses required by (a)(1) and (a)(2) of these
special conditions must account for the effects of in-service
deterioration, manufacturing and materials variations, and
environmental effects.
Issued in Burlington, Massachusetts, on June 28, 1994.
Ronald L. Vavruska,
Acting Manager, Engine and Propeller Directorate, Aircraft
Certification Service.
[FR Doc. 94-16678 Filed 7-8-94; 8:45 am]
BILLING CODE 4910-13-M
