[Federal Register Volume 73, Number 227 (Monday, November 24, 2008)]
[Proposed Rules]
[Pages 70926-70928]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E8-27540]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 33

[Docket No. NE129; Notice No. 33-08-01-SCI]


Special Conditions: General Electric Company GEnx-2B Model 
Turbofan Engines

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed special conditions.

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SUMMARY: This notice proposes special conditions for General Electric 
Company (GE) GEnx-2B67 and GEnx-2B69 model turbofan engines. 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 
the Administrator considers necessary to establish a level of safety 
equivalent to that established by the existing airworthiness standards 
of 14 CFR part 33.

DATES: We must receive your comments on or before December 24, 2008.

ADDRESSES: You may mail two copies of your comments to: Federal 
Aviation Administration, Aircraft Certification Service, Engine and 
Propeller Directorate, Attn: Robert McCabe, ANE-110 Standards Staff, 12 
New England Executive Park, Burlington, Massachusetts 01803-5299, Rules 
Docket No. NE129. You may deliver two copies to the Engine and 
Propeller Directorate at the above address. You must mark your 
comments: Docket No. NE 129. You may send comments via e-mail to 
[email protected]. You must use the subject ``Docket No. NE 129''. 
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: Federal Aviation Administration, 
Aircraft Certification Service, Engine and Propeller Directorate, Attn: 
Robert McCabe, ANE-1 10 Standards Staff, 12 New England Executive Park, 
Burlington, Massachusetts 01803-5299; telephone (781) 238-7138; 
facsimile (781) 238-7199; e-mail [email protected].

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 7:30 a.m. and 4 p.m., Monday through Friday, except Federal 
holidays.
    We will consider all comments we receive on or before 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 preaddressed, stamped postcard on which the docket 
number appears. We will stamp the date on the postcard and mail it back 
to you.

Background

    On February 28, 2006, the General Electric Company (GE) applied to 
the FAA to amend the GEnx model type certificate to add GEnx-2B engine 
model series. Currently, the GEnx type certificate consists of the 
GEnx-1B turbofan engine models GEnx-1B54, GEnx-1B58, GEnx-1B64, GEnx-
B67, and GEnx-1B70. GE is requesting to add the GEnx-2B67 and GEnx-2B69 
engine model series to the type certificate.
    The GEnx-2B engine model series is a close derivative of the GEnx-
1B engine models, and will utilize a significant number of common parts 
and systems. Some GEnx-2B engine model components, which differ from 
those on the GEnx-1B engine models, include a smaller diameter fan 
operating at a slightly higher speed, a lower guide vane count, fewer 
booster stages, lower bypass ratio, fewer low pressure turbine stages, 
lighter accessories gearbox, and a modified turbine rear frame. Those 
components do not introduce any unique materials, design concepts, or 
manufacturing processes.
    The GEnx-2B engine models will also incorporate fan blades 
manufactured using carbon graphite composite material, with a bonded 
metal tip cap, and metal leading and trailing edge laminates. The 
design and manufacture of these fan blades are similar to those used on 
the GE90-76B, -77B, -85B, -90B, -94B baseline engines, the GE90-110B1, 
-113B, and -115B derivative engine model series, and the GEnx-1B engine 
model series. This novel and unusual design feature results in the fan 
blades having significant differences in material property 
characteristics when compared to conventionally designed fan blades 
using only metallic materials.
    GE submitted data and analysis during the GE90 baseline and GE90-
115B derivative engine model certification programs, and again during 
the recent GEnx-JB certification program. GE was able to show that the 
likelihood of these carbon graphite composite fan blades failing below 
the inner annulus flow path line is highly improbable. GE questioned 
the appropriateness of the requirement contained in Sec.  33.94(a)(1) 
to show containment after a failure of the fan blade at the outermost 
retention feature.
    The FAA responded during the GE90 baseline by reviewing the 
historical basis for the Sec.  33.94(a)(1) test requirements, and 
determined that they are based on metallic blade characteristics and 
service history, and therefore were not appropriate for the unusual 
design features of the composite fan blade design planned for

[[Page 70927]]

that engine model. The FAA determined that a more realistic blade 
retention test for the novel and unusual design characteristics of 
these carbon fiber composite fan blades would be achieved with a blade 
failure at the inner annulus flow path line (the complete airfoil 
only), instead of at the outermost blade retention feature as currently 
required by Sec.  33.94(a)(1).
    The FAA also determined that the composite fan blade design and 
construction characteristics present factors, other than the expected 
location of a blade failure, which must be considered. Consequently, 
the FAA required that tests and analyses must account for the 
anticipated effects of in-service deterioration and handling damage, 
manufacturing and materials variations in, and environmental effects 
on, the composite material. The FAA also required that tests and 
analyses must show that a lightning strike on a composite fan blade 
would not result in a hazardous condition to the aircraft, and that the 
engine would continue to meet the requirements of 33.75.
    Therefore, the FAA issued special conditions SC-33-ANIE-08 on 
February 1, 1995, for the GE90-75B, 76B, and -85B baseline 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 determined that these special conditions were also 
appropriate for the derivative GE90 77B and -90B engine models, the 
GE90-94B engine model, and the GE90 -110B1, -113B, and -115B engine 
models, which were added to the TCDS in July 1996, June 2000, and July 
2003, respectively. Engine model series GE90-75B was deleted from the 
GE90 TCDS in February 1995.
    The FAA later determined that, due to the similarity of the carbon 
fiber composite fan blade design and construction methods to the GE90 
blades, these same special conditions continued to be appropriate for 
the recent GEnx-1B model series certification program. The FAA issued 
special conditions 33-006-SC on January 12, 2007, for the GEnx-1B 
engine model series, which retained the essential requirements of the 
previous GE90 engine model series special conditions. These special 
conditions were successfully applied during the GEnx-1B certification 
program.
    Due to that success, GE now proposes to use a similar approach to 
demonstrate a level of safety equivalent to that established by the 
airworthiness standards of Sec.  33.94(a)(1) for the GEnx 2B 
certification program. In lieu of direct compliance to Sec.  
33.94(a)(1) using an engine test, GE notified the FAA that it plans to 
utilize an analytical method that will be validated by data from the 
GEnx-1B Sec.  33.94(a)(1) engine test, GEnx-lB fan blade rig tests, 
GEnx-2B fan blade rig tests, and other engine and component tests as 
needed.
    Due to the similarity of the GEnx-2B model series fan blade design 
and manufacturing methods to the previously certified GE90 and GEnx-1B 
engine model series fan blades, the FAA is proposing to issue similar 
special conditions as part of the type certification basis for the 
GEnx-2B engine models in lieu of requiring direct compliance to Sec.  
33.94(a)(1) using an engine test. These special conditions define the 
additional requirements the Administrator considers necessary to 
establish a level of safety equivalent to direct compliance to the 
airworthiness standards of Sec.  33.94(a)(1).

Type Certification Basis

    14 CFR 21.17 requires GE to show the derivative GEnx-2B series 
turbofan engine models meet the requirements of the applicable 
provisions of 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-2B 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 14 CFR 21.16, and will become part of the type 
certification basis of the GEnx-2B engine in accordance with Sec.  
21.17(a)(2).
    These special conditions apply only to the GEnx-2B 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 also apply to the 
other models under the provisions of 14 CFR 21.101(a)(1).

Novel or Unusual Design Features

    The GEnx-2B engine models will incorporate carbon graphite 
composite fan blades that will contain a bonded metal tip cap, and 
metal leading and trailing edge laminates. These design features are 
considered to be novel and unusual relative to the part 33 
airworthiness standards.

Applicability

    These special conditions will apply only to the GEnx-2B series 
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 may also 
become part of the type certification basis of that engine model series 
as well.

Conclusion

    This action affects only the carbon fiber composite fan blade 
design features on the GEnx-2B 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 FAA proposes the following special conditions as 
part of the type certification basis for the derivative GEnx-2B 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 a fan blade containment test that is acceptable to the 
Administrator, 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 the engine is capable of containing damage 
without catching fire and without failure of its mounting attachments 
when operated for at least 15 seconds, unless the resulting engine 
damage induces a self shutdown that initiates within 15 seconds of the 
fan blade failure.
    (c) 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.
    (d) Using a procedure approved by the Administrator, establish an 
operating

[[Page 70928]]

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 05 of the Engine Manual 
Airworthiness Limitation Section. 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.
    (e) 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 per engine flight hour.
    (f) Substantiate by test or analysis acceptable to the 
Administrator that not only will the engine continue to meet the 
requirements of 33.75 following a lightning strike on the composite fan 
blade structure, but the lightning strike will also not cause damage to 
the fan blades that would prevent continued safe operation of the 
affected engine.
    (g) 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), (e), and (f) of these special 
conditions.
    (h) Propose fleet leader monitoring and field sampling programs for 
the GEnx-2B 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 and GEnx-1B engine model 
series monitoring programs, and must be approved by the FAA prior to 
certification of the GEnx-2B engine models.

    Issued in Burlington, Massachusetts on November 12, 2008.
Peter A. White,
Acting Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. E8-27540 Filed 11-21-08; 8:45 am]
BILLING CODE 4910-13-M