[Federal Register: January 24, 2007 (Volume 72, Number 15)]
[Rules and Regulations]
[Page 3042-3044]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr24ja07-5]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 33
[Docket No. NE127; Special Conditions No. 33-006-SC]
Special Conditions: General Electric Company GEnx Model Turbofan
Engines
AGENCY: Federal Aviation Administration, DOT.
ACTION: Final special conditions.
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SUMMARY: These special conditions are issued for the General Electric
Company (GE) GEnx turbofan engine models GEnx-1B54, GEnx-1B58, GEnx-
1B64, GEnx-1B67, GEnx-1B70, GEnx-1B70/72, GEnx-1B70/75, GEnx-1B72, and
GEnx-1B75. The fan blades of these engines will have novel or unusual
design features when compared to the state of technology envisioned in
the part 33 airworthiness standards. The applicable airworthiness
regulations do not contain adequate or appropriate safety standards for
these design features. These special conditions contain the added
safety standards that the Administrator considers necessary to
establish a level of safety equivalent to that established by the
existing airworthiness standards.
DATES: Effective Date: The effective date of these special conditions
is January 12, 2007.
FOR FURTHER INFORMATION CONTACT: Robert McCabe, ANE-111, Rulemaking and
Policy Branch, Engine and Propeller Directorate Standards Staff,
Aircraft Certification Service, 12 New England
[[Page 3043]]
Executive Park, Burlington, Massachusetts 01803-5299; telephone (781)
238-7138; facsimile (781) 238-7199; e-mail robert.mccabe@faa.gov.
SUPPLEMENTARY INFORMATION:
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 previously
certified GE90-series engine fan blade designs.
In lieu of direct compliance to 14 CFR section (Sec. ) 33.94(a)(1)
for the GEnx fan blades, the FAA proposed that GE comply with new
special conditions that retain the basic 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 will 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-08 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 intent of 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 has also
concluded that these same special conditions, with some additional
enhancements, continue to be appropriate for the GEnx model engines.
Type Certification Basis
Under the provisions of 14 CFR 21.17, GE must show that the GEnx
series turbofan engine models meet the requirements of applicable
provisions of part 33 in effect on the date of the application for the
type certificate. 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 21.16, and will become part of the type certification basis
for GEnx engine in accordance with Sec. 21.17(a)(2).
As discussed above, these special conditions apply only to the GEnx
series turbofan engine models GEnx-1B54, GEnx-1B58, GEnx-1B64, GEnx-
1B67, GEnx-1B70, GEnx-1B70/72, GEnx-1B70/75, GEnx-1B72, and GEnx-1B75.
If the type certificate for those models is amended later to include
any other models that incorporate the same novel or unusual fan blade
design features, these special conditions would apply to the other
models under the provisions of Sec. 21.101(a)(1).
Discussion of Novel or Unusual Design Features
The GEnx-1B54, -B58, -1B64, -1B67, -70B, -1B70/72, -1B70/75, -72B
and -75B engine models will incorporate fan blades to be manufactured
using carbon graphite composite material that incorporates metal
leading and trailing edges. The FAA has conducted that these carbon
graphite composite fan blades are novel and unusual compared to the
metallic fan blade technology envisioned in the part 33 standards and
thus warrant these special conditions.
The FAA has 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 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 models series
fan blade design to the previously certified GE90 model series fan
blade design, the FAA is issuing 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).
Discussion of Comments
Notice of Proposed Special Conditions, Docket No. NE127; Notice No.
33-06-01-SC, was published in the Federal Register on November 17, 2006
(71 FR 66888). We received no comments on the proposed special
conditions. After a careful review of the applicable data, the FAA has
determined that air safety and the public interest require the adoption
of these special conditions as proposed.
Conclusion
This action affects only the carbon fiber composite fan blade
design features on the GEnx series turbofan engine models GEnx-1B54,
GEnx-1B58, GEnx-1B64, GEnx-1B67, GEnx-1B70, GEnx-1B70/72, GEnx-1B70/75,
GEnx-1B72, and GEnx-1B75. 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.
[[Page 3044]]
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);
and 14 CFR 11.49 and 21.16.
The Special Conditions
Accordingly, the Federal Aviation Administration (FAA) issues 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 analysis, 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 system. 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 January 12, 2007.
Francis A. Favara,
Manager, Engine and Propeller Directorate, Aircraft Certification
Service.
[FR Doc. 07-301 Filed 1-23-07; 8:45 am]
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