Special Conditions: General Electric Company, GE9X Engine Models; Incorporation of Composite Fan Blades, 15611-15612 [2017-06277]

Agencies

• Federal Aviation Administration
• DEPARTMENT OF TRANSPORTATION

[Federal Register Volume 82, Number 60 (Thursday, March 30, 2017)]
[Rules and Regulations]
[Pages 15611-15612]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2017-06277]



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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 33

[Docket No. FAA-2017-0171; Special Conditions No. 33-018-SC


Special Conditions: General Electric Company, GE9X Engine Models; 
Incorporation of Composite Fan Blades

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions; request for comments.

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SUMMARY: These special conditions are issued for the General Electric 
(GE) GE9X turbofan engine models. These engine models will have novel 
or unusual design features associated with composite fan blades. The 
applicable airworthiness regulations do not contain adequate or 
appropriate safety standards for these design features. These special 
conditions contain the additional safety standards that the 
Administrator considers necessary to establish a level of safety 
equivalent to that established by the existing airworthiness standards.

DATES: The effective date of these special conditions is April 14, 
2017. We must receive your comments by May 1, 2017.

ADDRESSES: Send comments identified by docket number FAA-2017-0171 
using any of the following methods:
     Federal eRegulations Portal: Go to https://www.regulations.gov and follow the online instructions for sending your 
comments electronically.
     Mail: Send comments to Docket Operations, M-30, U.S. 
Department of Transportation (DOT), 1200 New Jersey Avenue SE., Room 
W12-140, West Building Ground Floor, Washington, DC 20590-0001.
     Hand Delivery or Courier: Take comments to Docket 
Operations in Room W12-140 of the West Building Ground Floor at 1200 
New Jersey Avenue SE., Washington, DC, between 9 a.m. and 5 p.m., 
Monday through Friday, except Federal holidays.
     Fax: Fax comments to Docket Operations at 202-493-2251.
    Privacy: In accordance with 5 U.S.C. 553(c), DOT solicits comments 
from the public to better inform its rulemaking process. DOT posts 
these comments, without edit, including any personal information the 
commenter provides, to www.regulations.gov, as described in the system 
of records notice (DOT/ALL-14 FDMS), which can be reviewed at 
www.dot.gov/privacy.
    Docket: Background documents or comments received may be read at 
https://www.regulations.gov at any time. Follow the online instructions 
for accessing the docket or go to the Docket Operations in Room W12-140 
of the West Building Ground Floor at 1200 New Jersey Avenue SE., 
Washington, DC, between 9 a.m. and 5 p.m., Monday through Friday, 
except Federal holidays.

FOR FURTHER INFORMATION CONTACT: For technical questions concerning 
these special conditions, contact Jay Turnberg, Engine and Propeller 
Directorate, Aircraft Certification Service, 1200 District Avenue, 
Burlington, Massachusetts, 01803-5213; telephone (781) 238-7755; 
facsimile (781) 238-7199; email Jay.Turnberg@faa.gov.

SUPPLEMENTARY INFORMATION: The FAA has determined that notice of, and 
opportunity for prior public comment on, these special conditions is 
impracticable because these procedures would significantly delay 
issuance of the Type Certificate approval and thus, delivery of the 
affected engines.
    In addition, the substance of these special conditions has been 
subjected to the notice and comment period in several prior instances, 
and has been derived without substantive change from those previously 
issued. It is unlikely that prior public comment would result in a 
significant change from the substance contained herein. Therefore, 
because a delay would significantly affect the certification of the 
engine, which is imminent, the FAA has determined that prior public 
notice and comment are unnecessary and impracticable, and good cause 
exists for adopting these special conditions.

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 will 
consider all comments we receive by the closing date for comments. We 
may change these special conditions based on the comments we receive.

Background

    On January 29, 2016, GE applied for a type certificate for their 
new GE9X turbofan engine models. The High-Bypass-Ratio GE9X engine 
models incorporate composite fan blades, a novel or unusual design 
feature. These fan blades have significant material property 
characteristics differences from conventional, single load path, 
metallic fan blades. Additionally, they have multiple load path 
features and/or crack arresting feature capabilities that, during the 
blade life, may prevent delamination, crack propagation, and/or blade 
failure.
    Because of their novel or unusual design, these fan blades require 
additional airworthiness standards for GE9X engine type certification, 
to account for material property and failure mode differences with 
conventional fan blades. The applicable airworthiness regulations that 
exist do not contain appropriate safety standards for these new blades. 
The FAA may allow for application of different fan blade containment 
requirements, if GE demonstrates improved load path features and/or 
crack arresting feature capabilities of the new blade design, below the 
inner annulus flow path line.

Type Certification Basis

    Under the provisions of Title 14, Code of Federal Regulations (14 
CFR) 21.17, GE must show that the GE9X engine models meet the 
applicable provisions of part 33, ``Airworthiness Standards, Aircraft 
Engines,'' dated February 1, 1965, as amended by Amendments 33-1 
through 33-34, dated January 5, 2015. The FAA has determined that the 
applicable airworthiness regulations in part 33 do not contain adequate 
or appropriate safety standards for the GE9X engine models because of 
their 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 
GE9X engine models in accordance with Sec.  21.17(a)(2).
    Special conditions are initially applicable to the engine models 
for which they are issued. Should the type certificate for that engine 
model be amended later to include any other engine models that 
incorporate the same novel or unusual design features, the special 
conditions would also apply to the other engine models under Sec.  
21.101.
    In addition to complying with the applicable product airworthiness 
regulations and special conditions, the GE9X engine models must comply 
with the fuel venting and exhaust emission requirements of 14 CFR part 
34.
    The FAA issues special conditions, as defined in 14 CFR 11.19, in 
accordance with Sec.  11.38, and they become part of the type 
certification basis under Sec.  21.17(a)(2).

Novel or Unusual Design Features

    The GE9X engine models will incorporate the following novel or

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unusual design features: Composite fan blades. These fan blades will 
have significant differences in material property characteristics as 
compared to conventionally designed fan blades using non-composite 
metallic materials. Composite material designs can incorporate multiple 
load paths and/or crack arresting features that prevent delamination or 
crack propagation that could result in blade failure during the blade 
service life. These blades require additional airworthiness standards 
for type certification of the GE9X engine models.

Discussion

    As discussed in the summary section, the GE9X engine models 
incorporate composite fan blades instead of conventional, single load 
path, metallic fan blades, which is a novel or unusual design feature 
for aircraft engines. The applicable airworthiness regulations do not 
contain adequate or appropriate safety standards for this design 
feature.

Applicability

    As discussed above, these special conditions are applicable to the 
GE9X engine models. Should GE apply at a later date for a change to the 
type certificate to include another model on the same type certificate 
incorporating the same novel or unusual design features, the special 
conditions would apply to that model as well.

Conclusion

    This action affects only certain novel or unusual design features 
on GE9X engine models. It is not a rule of general applicability and 
applies only to GE, who requested FAA approval of this engine feature.

List of Subjects in 14 CFR Part 33

    Aircraft, Engines, Aviation safety, Reporting and recordkeeping 
requirements.

    The authority citation for these special conditions is as follows:

    Authority: 49 U.S.C. 106(g), 40113, 44701, 44702, 44704.

The Special Conditions

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the following special conditions are issued as part of 
the type certification basis for GE9X engine models.
    1. Special Conditions: General Electric Company, GE9X Engine 
Models; Incorporation of Composite Fan Blades. 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 instead of at the outermost 
retention groove.
    (b) Substantiate by test and analysis, or other methods acceptable 
to the FAA, that a fan disk and fan blade retention system with minimum 
material properties can withstand, without failure, a centrifugal load 
equal to two times the maximum load 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 FAA, establish an operating 
limitation that specifies the maximum allowable number of start-stop 
stress cycles for the fan blade retention system. The life evaluation 
must 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. The procedure used to establish the 
maximum allowable number of start-stop stress cycles for the fan blade 
retention system will incorporate the integrity requirements specified 
in paragraphs (c)(1), (c)(2), and (c)(3) of these special conditions 
for the fan blade retention system.
    (1) An engineering plan which establishes and maintains that the 
combinations of loads, material properties, environmental influences, 
and operating conditions, including the effects of parts influencing 
these parameters, are well known or predictable through validated 
analysis, test, or service experience.
    (2) A manufacturing plan that identifies the specific manufacturing 
constraints necessary to consistently produce the fan blade retention 
system with the attributes required by the engineering plan.
    (3) A service management plan that defines in-service processes for 
maintenance and repair of the fan blade retention system, which will 
maintain attributes consistent with those required by the engineering 
plan.
    (d) Substantiate by test and analysis, or other methods acceptable 
to the FAA, that the blade design below the inner annulus flow path 
line provides multiple load paths and/or crack arresting features that 
prevent delamination or crack propagation to blade failure during the 
life of the blade.
    (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 10-9) per engine flight hour.
    (f) 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 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 (b), (c), (d), (e), and (f) of these special conditions.
    (h) Propose fleet leader monitoring and field sampling programs 
that will monitor the effects of engine fan blade usage on fan blade 
retention system integrity. The programs must be approved by the FAA 
prior to certification of the GE9X engine models.
    (i) Mark each fan blade legibly and permanently with a part number 
and a serial number.

    Issued in Burlington, Massachusetts, on March 23, 2017.
Robert J. Ganley,
Acting Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. 2017-06277 Filed 3-29-17; 8:45 am]
BILLING CODE 4910-13-P