[Federal Register: November 17, 2006 (Volume 71, Number 222)]
[Proposed Rules]
[Page 66888-66889]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr17no06-18]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 33
[Docket No. NE127; Notice No. 33-06-01-SC]
Special Conditions: General Electric Company GEnx Model Turbofan
Engines
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Notice of proposed special conditions.
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SUMMARY: This action proposes special conditions for General Electric
Company (GE) GEnx turbofan engine models. These engines will have a
novel or unusual design feature associated with the fan blades. The
Administrator has determined that the applicable part 33 airworthiness
regulations do not contain adequate or appropriate safety standards for
this design feature. These proposed special conditions contain the
added safety standards that the Administrator considers necessary to
establish a level of safety equivalent to that established by the
airworthiness regulations.
EFFECTIVE DATES: We must receive your comments by December 18, 2006.
ADDRESSES: You may mail two copies of your comments to: Federal
Aviation Administration, Engine and Propeller Directorate, Attn: Robert
McCabe, Rules Docket (ANE-111), Docket No. NE127, 12 New England
Executive Park, Burlington, Massachusetts 01803-5299. You may deliver
two copies to the Engine and Propeller Directorate at the above
address. You must mark your comments: Docket No. NE127. You may send
comments via email to robert.mccabe@faa.gov. You must use the subject
``Docket No. NE127''. 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: Robert McCabe, ANE-111, Rulemaking and
Policy Branch, Engine and Propeller Directorate, Aircraft Certification
Service, 12 New England Executive Park, Burlington, Massachusetts
01803-5299; telephone (781) 237-7138; facsimile (781) 238-7199; email
robert.mccabe@faa.gov.
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
about 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 9 a.m. and 5 p.m., Monday through Friday, except Federal
holidays.
We will consider all comments we receive by 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 let you know we received your comments on this
proposal, send us 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
On December 13, 2004, the General Electric Company (GE) applied to
the FAA for a new type certificate for the GEnx series engine models.
On May 24, 2005, GE submitted a revised application for a type
certificate that added models and changed the model designation
nomenclature. The turbofan engine models to be certified are GEnx-1B54,
GEnx-1B58, GEnx-1B64, GEnx-1B67, GEnx-1B70, GEnx-1B70/72, GEnx-1B70/75,
GEnx-1B72, and GEnx-1B75. For these GEnx engine models, GE plans to use
carbon graphite composite fan blades incorporating metal leading and
trailing edges that use geometry, composite structural materials, and
manufacturing methods very similar to those used for the previously
certified GE90-series engine fan blades designs.
In lieu of direct compliance to Sec. 33.94(a)(1) for the GEnx fan
blades, the FAA has proposed that GE comply with new special conditions
that retain the requirements of the original SC-33-ANE-08 created for
the GE90-76B, -77B, -85B, -90B, -94B model certification program, and
then successfully applied to the GE90-110B1, -113B, and -115B model
certification program.
These GE90 series engine model fan blades are manufactured using
carbon graphite composite material that also incorporates metal leading
and trailing edges. These unusual and novel design features result in
the fan blades having significant differences in material property
characteristics when compared to conventionally designed fan blades
using non-composite metallic materials. GE submitted data and analysis
during the GE90-76B, -77B, -85B, -90B, -94B model certification program
showing the likelihood that a composite fan blade with fail below the
inner annulus flow path line is highly improbable. GE, therefore,
questioned the appropriateness of the requirement contained in Sec.
33.94(a)(1) to show blade containment after a failure of the blade at
the outermost retention feature.
The FAA determined that the requirements of Sec. 33.94(a)(1) are
based on metallic blade characteristics and service history, and were
not appropriate for the unusual design features of the composite fan
blade design planned for the GE90-76B, -77B, -85B, -90B, -94B model
turbofan engines. The FAA determined that a more realistic blade
retention test would be achieved with a fan blade failure at the inner
annulus flow path line (the complete airfoil only) instead of the
outermost blade retention feature as currently required by Sec.
33.94(a)(1).
The FAA, therefore, issued special conditions SC-33-ANE-88 on
February 1, 1995 for the GE90-76B, -77B, -85B, -90B, -94B engine
models. These special conditions defined additional safety standards
for the carbon graphite composite fan blades that were appropriate for
the unusual design features of those fan blades and that were
determined to be necessary to establish a level of safety equivalent to
that established by the airworthiness standards of Sec. 33.94(a)(1).
The FAA later determined that these special conditions continued to be
appropriate for the amended type certificate applied to the GE90-110B1,
-113B, and -115B engine models.
The FAA also determined that the composite fan blade design and
construction presents factors other than the expected location of a
blade failure 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. Tests and analyses
[[Page 66889]]
must also show that a lightning strike on a composite fan blade will
not result in a hazardous condition to the aircraft and that the engine
will continue to meet the requirements of Sec. 33.75.
Therefore, due to the close similarity of the GEnx model series fan
blade design to the previously certified GE90 model series fan blade
design, the FAA is proposing to issue similar special conditions as
part of the type certification basis for the GEnx engine models in lieu
of direct compliance to Sec. 33.94(a)(1). These special conditions
define the additional requirements that the Administrator considers
necessary to establish a level of safety equivalent to that which would
be established by direct compliance to the airworthiness standards of
Sec. 33.94(a)(1).
Type Certification Basis
Under 14 CFR 21.17, GE must show that the GEnx series turbofan
engine models meet the requirements of the applicable provisions of
Sec. 21.21 and part 33. The FAA has determined that the applicable
airworthiness regulations in part 33 do not contain adequate or
appropriate safety standards for the GEnx series turbofan engine models
because of its novel and unusual fan blade design features. Therefore,
these special conditions are prescribed under the provisions of 14 CFR
11.19 and Sec. 21.16, and will become part of the type certification
basis of the GEnx engine in accordance with 14 CFR 21.17(a)(2).
As discussed above, these special conditions apply only to the GEnx
series turbofan engine models. If the type certificate for those models
is amended later to include any other models that incorporate the same
novel or unusual design features, these special conditions would also
apply to the other models under the provisions of 14 CFR 21.101(a)(1).
Novel or Unusual Design Features
The GEnx-1B54, -1B58, -1B64, -1B67, -70B, -1B70/72, -1B70/75, -72B
and -75B engine models will incorporate the following novel or unusual
design features: fan blades to be manufactured using carbon graphite
composite material that incorporates metal leading and training edges.
Applicability
As discussed above, these special conditions apply only to the
GEnx-1B54, -1B58, -1B64, -1B67, -70B, -1B70/72, -1B70/75, -72B and -75B
turbofan engine models. If GE applies later for a change to the type
certificate to include another model incorporating the same novel or
unusual fan blade design features, these special conditions would apply
to that model as well.
Conclusion
This action affects only the carbon fiber composite fan blade
design features on the GEnx series turbofan engine models. It is not a
rule of general applicability, and it affects only the General Electric
Company which has applied to the FAA for certification of these fan
blade design features.
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. 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 GEnx series turbofan engines.
1. In lieu of the fan blade containment test with the fan blade
failing at the outermost retention groove as specified in Sec.
33.94(a)(1), complete the following requirements:
(a) Conduct an engine fan blade containment test with the fan blade
failing at the inner annulus flow path line.
(b) Substantiate by test and analyses, or other methods acceptable
to the Administrator, that a minimum material properties fan disk and
fan blade retention system can withstand without failure a centrifugal
load equal to two times the maximum load which the retention system
could experience within approved engine operating limitations. The fan
blade retention system includes the portion of the fan blade from the
inner annulus flow path line inward to the blade dovetail, the blade
retention components, and the fan disk and fan blade attachment
features.
(c) Using a procedure approved by the Administrator, establish an
operating limitation that specifies the maximum allowable number of
start-stop stress cycles for the fan blade retention systems. The life
evaluation shall include the combined effects of high cycle and low
cycle fatigue. If the operating limitation is less than 100,000 cycles,
that limitation must be specified in Chapter 5 of the Engine Manual
Airworthiness Limitation Section.
(d) Substantiate that, during the service life of the engine, the
total probability of the occurrence of a hazardous engine effect
defined in Sec. 33.75 due to an individual blade retention system
failure resulting from all possible causes will be extremely
improbable, with a cumulative calculated probability of failure of less
than 10-9 per engine flight hour.
(e) Substantiate by test or analysis that not only will the engine
continue to meet the requirements of Sec. 33.75 following a lightning
strike on the composite fan blade structure, but that the lightning
strike will also not cause damage to the fan blades that would prevent
continued safe operation of the affected engine.
(f) Account for the effects of in-service deterioration,
manufacturing variations, minimum material properties, and
environmental effects during the tests and analyses required by
paragraphs (a), (b), (c), (d), and (e) of these special conditions.
(g) Propose fleet leader monitoring and field sampling programs for
the GEnx engine fan blades that will monitor the effects of usage on
fan blade and retention system integrity. The sampling program should
use the experience gained on current GE90 engine model monitoring
programs, and must be approved by the FAA prior to certification of the
GEnx engine models.
Issued in Burlington, Massachusetts on November 7, 2006.
Francis A. Favara,
Manager, Engine and Propeller Directorate, Aircraft Certification
Service.
[FR Doc. 06-9230 Filed 11-16-06; 8:45 am]
BILLING CODE 4910-13-M