[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