Special Conditions: General Electric Company GEnx Model Turbofan Engines, 66888-66889 [06-9230]

Agencies

• Federal Aviation Administration
• DEPARTMENT OF TRANSPORTATION

[Federal Register Volume 71, Number 222 (Friday, November 17, 2006)]
[Proposed Rules]
[Pages 66888-66889]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 06-9230]


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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