[Federal Register Volume 72, Number 15 (Wednesday, January 24, 2007)]
[Rules and Regulations]
[Pages 3042-3044]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 07-301]


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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 [email protected].

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]
BILLING CODE 4910-13-M