[Federal Register Volume 79, Number 220 (Friday, November 14, 2014)]
[Proposed Rules]
[Pages 68137-68139]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2014-27019]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 33

[Docket No. FAA-2014-0637; Notice No. 33-14-02-SC]


Special Conditions: CFM International, LEAP-1A and -1C Engine 
Models; Incorporation of Woven Composite Fan Blades

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed special conditions.

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SUMMARY: This action proposes special conditions for the CFM 
International (CFM), LEAP-1A and -1C engine models. These engines will 
have a novel or unusual design feature associated with the engine fan 
blades--new woven composite fan blades. The applicable airworthiness 
regulations do not contain adequate or appropriate safety standards for 
this design feature. These proposed 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: Send your comments on or before December 29, 2014.

ADDRESSES: Send comments identified by docket number [FAA-2014-0637] 
using any of the following methods:
     Federal eRegulations Portal: Go to http://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: Docket Operations will post all comments it receives, 
without change, to http://regulations.gov, including any personal 
information the

[[Page 68138]]

commenter provides. Using the search function of the docket Web site, 
anyone can find and read the electronic form of all comments received 
into any FAA docket, including the name of the individual sending the 
comment (or signing the comment for an association, business, labor 
union, etc.). DOT's complete Privacy Act Statement can be found in the 
Federal Register published on April 11, 2000 (65 FR 19477-19478), as 
well as at http://DocketsInfo.dot.gov.
    Docket: You may read background documents or comments received at 
http://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 proposed special conditions, contact Alan Strom, ANE-111, Engine 
and Propeller Directorate, Aircraft Certification Service, 12 New 
England Executive Park, Burlington, Massachusetts, 01803-5213; 
telephone (781) 238-7143; facsimile (781) 238-7199; email 
[email protected]. For legal questions concerning this proposed rule, 
contact Vincent Bennett, ANE-7, Engine and Propeller Directorate, 
Aircraft Certification Service, 12 New England Executive Park, 
Burlington, Massachusetts, 01803-5299; telephone (781) 238-7044; 
facsimile (781) 238-7055; email [email protected].

SUPPLEMENTARY INFORMATION:

Comments Invited

    We invite interested people to participate in this rulemaking by 
submitting written comments, data, or views. The agency also invites 
comments relating to the economic, environmental, energy, or federalism 
impacts that might result from adopting the proposals in this document. 
The most helpful comments reference a specific portion of the proposed 
special conditions, explain the reason for any recommended change, and 
include supporting data. To ensure the docket does not contain 
duplicate comments, commenters should send only one copy of written 
comments, or if comments are filed electronically, commenters should 
submit only one time.
    We will file in the docket all comments it receives, as well as a 
report summarizing each substantive public contact with FAA personnel 
concerning this proposed rulemaking. Before acting on this proposal, 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.

Background

    On June 27, 2012, the FAA received the type certificate application 
for CFM's LEAP-1A and -1C turbofan engine models. The LEAP engine 
models are high-bypass-ratio engines that incorporate a novel and 
unusual design feature--new woven composite fan blades. The woven 
composite fan blades will have significant differences in material 
property characteristics when compared to conventionally designed fan 
blades using non-composite metallic materials.
    Special conditions are required to ensure that the LEAP-1A and -1C 
woven composite design fan blades account for the differences in 
material properties and failure modes relative to conventional single-
load path metallic blades. In addition, different containment 
requirements may be applied provided CFM shows 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.
    These special conditions are necessary because the applicable 
airworthiness regulations do not contain adequate or appropriate safety 
standards for the new woven composite design fan blades.

Type Certification Basis

    Under the provisions of Title 14, Code of Federal Regulations (14 
CFR) 21.17, CFM must show that the LEAP-1A and -1C engine models meet 
the applicable provisions of the applicable regulations in effect on 
the date of application, except as detailed in paragraphs 21.101(b) and 
(c). The FAA has determined the following certification basis for the 
LEAP-1A and -1C engine models:
    1. 14 CFR part 33, ``Airworthiness Standards: Aircraft Engines,'' 
dated February 1, 1965, with Amendments 33-1 through 33-32, dated 
September 20, 2012.
    If the FAA finds that the regulations in effect on the date of the 
application for the change do not provide adequate or appropriate 
safety standards for the LEAP-1A and -1C engine models because of a 
novel or unusual design feature, special conditions are prescribed 
under the provisions of Sec.  21.16.
    Special conditions are initially applicable to the model for which 
they are issued. Should the type certificate for that model be amended 
later to include any other model that incorporates the same or similar 
novel or unusual design feature, the special conditions would also 
apply to the other model under Sec.  21.101.
    In addition to complying with the applicable product airworthiness 
regulations and the requirements of these special conditions, the LEAP-
1A and -1C engine models must also 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 LEAP-1A and -1C engine models will incorporate the following 
novel or unusual design feature:
    The LEAP-1A and -1C engine models will incorporate woven composite 
fan blades. The woven composite fan blades will have significant 
differences in material property characteristics when compared to 
conventionally designed fan blades using non-composite metallic 
materials. Composite material design provides the capability to 
incorporate multiple load paths and/or crack arresting features that 
prevent delamination or crack propagation to blade failure during the 
life of the blade.
    The woven composite fan blades are a novel and unusual design 
feature that requires additional airworthiness standards for type 
certification of the LEAP-1A and -1C engine models.

Discussion

    The woven composite fan blades are a novel and unusual design 
feature that requires additional airworthiness standards for type 
certification of the LEAP-1A and -1C engine models. The current 
requirements of Sec.  33.94 are based on single-load path metallic fan 
blade characteristics and service history, and are not appropriate for 
the unusual design features of the woven composite fan blade found on 
the CFM LEAP series turbofan engines.
    The properties of a composite blade are highly dependent of the 
composite ply configuration, matrix material, and manufacturing 
methods. The CFM LEAP engine incorporates 3-D woven resin transfer 
molding (RTM) technology in the design and manufacture of the blade.
    It is expected that CFM will conduct the required material testing 
per Sec.  33.15

[[Page 68139]]

to determine material characteristics that include the effects of 
defects, manufacturing variations, contamination, environmental effect, 
and service damage on the material capability and blade life.
    Composite material design provides the capability to incorporate 
multiple load paths and/or crack arresting features that prevent 
delamination or crack propagation to blade failure during the life of 
the blade. The probability of failure that an appropriately designed 
composite fan blade will fail below the inner annulus flow path line 
may be highly improbable. The airworthiness regulations of 14 CFR part 
33 do not contain adequate or appropriate safety standards for an 
aircraft engine incorporating these novel or unusual design features 
i.e., woven composite fan blades, including release of the fan blade 
under Sec.  33.94(a)(1) at the inner annulus flow path line (only the 
airfoil) instead of the outermost retention feature.
    Instead of blade failure at the outermost retention groove 
currently required by Sec.  33.94(a)(1), the FAA has determined that a 
more realistic blade-out test can be achieved with a fan blade failure 
at the inner annulus flow path line i.e., releasing only the airfoil.
    Additionally, the FAA considers any change to the design, 
manufacturing, materials, or service management to the blade below the 
inner annulus flow path to be a change that could affect the blade 
integrity. Therefore, the FAA has determined that the blade be marked 
with a part and serial number, and that additional integrity 
requirements be applied to the blade below the inner annulus flow path 
line.
    These requirements maintain a level of safety equivalent to the 
level intended by the applicable airworthiness standards in effect on 
the date of application.

Applicability

    As discussed above, these special conditions are applicable to the 
LEAP-1A and -1C engine models. Should CFM apply at a later date for a 
change to the type certificate to include another model incorporating 
the same novel or unusual design feature, the special conditions would 
apply to that model as well.

Conclusion

    This action affects only the woven composite fan blade feature on 
the LEAP-1A and -1C engine models. It is not a rule of general 
applicability and applies only to CFM, who requested FAA approval of 
this engine feature.

List of Subjects in 14 CFR Part 33

    Aircraft, Engines, Aviation Safety, Reporting, and Recordkeeping.

    The authority citation for these special conditions is 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 CFM, LEAP-1A and -1C engine 
models.

1. Part 33, Requirements

    In addition to the airworthiness standards in 14 CFR part 33, 
effective February 1, 1965, with Amendments 33-1 through 33-32 
applicable to the CFM, LEAP-1A and -1C engine models:
    (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 in 
paragraphs (c)(1), (2), and (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 an individual blade retention system failure 
resulting from all possible causes, as defined in Sec.  33.75, 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 (a), (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 and fan blade 
retention system integrity.
    (i) Mark each fan blade legibly and permanently with a part number 
and a serial number.

    Issued in Burlington, Massachusetts, on November 6, 2014.
Kimberly K. Smith,
Acting Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. 2014-27019 Filed 11-13-14; 8:45 am]
BILLING CODE 4910-13-P