DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2017-0164; Product Identifier 2017-NE-06-AD; Amendment
39-19008; AD 2017-17-18]
RIN 2120-AA64

Airworthiness Directives; General Electric Company Turbofan
Engines

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: We are adopting a new airworthiness directive (AD) for certain
General Electric Company (GE) CF34-8 model turbofan engines. This AD
was prompted by analysis that resulted in the reduction of the life of
the affected fan blades. This AD requires inspections of the affected
fan blades until their removal. We are issuing this AD to address the
unsafe condition on these products.

DATES: This AD is effective October 6, 2017.
The Director of the Federal Register approved the incorporation by
reference of a certain publication listed in this AD as of October 6,
2017.

ADDRESSES: For service information identified in this final rule,
contact General Electric Company, GE--Aviation, Room 285, 1 Neumann
Way, Cincinnati, OH 45215, phone: 513-552-3272; fax: 513-552-3329;
email: geae.aoc@ge.com. You may view this service information at the
FAA, Engine and Propeller Standards Branch, Policy and Innovation
Division, 1200 District Avenue, Burlington, MA. For information on the
availability of this material at the FAA, call 781-238-7125. It is also
available on the internet at http://www.regulations.gov by searching
for and locating Docket No. FAA-2017-0164.

Examining the AD Docket

You may examine the AD docket on the Internet at http://www.regulations.
gov by searching for and locating Docket No. FAA-2017-
0164; or in person at the Docket Management Facility between 9 a.m. and
5 p.m., Monday through Friday, except Federal holidays. The AD docket
contains this final rule, the regulatory evaluation, any comments
received, and other information. The address for the Docket Office
(phone: 800-647-5527) is Document Management Facility, U.S. Department
of Transportation, Docket Operations, M-30, West Building
Ground Floor, Room W12-140, 1200 New Jersey Avenue SE., Washington, DC
20590.

FOR FURTHER INFORMATION CONTACT: John Frost, Aerospace Engineer, FAA,
ECO Branch, Compliance and Airworthiness Division, 1200 District
Avenue, Burlington, MA 01803; phone: 781-238-7756; fax: 781-238-7199;
email: john.frost@faa.gov.

SUPPLEMENTARY INFORMATION:

Discussion

We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR
part 39 by adding an AD that would apply to certain GE CF34-8 model
turbofan engines. The NPRM published in the Federal Register on April
14, 2017 (82 FR 17945). The NPRM was prompted by analysis that showed
that the stresses in the pinholes, in the affected fan blades, could
result in crack initiation at pinhole surfaces beyond 19,000, 19,500,
or 25,000 cycles-since-new (CSN), depending on the engine model on
which the blade is installed. The NPRM proposed to require initial and
repetitive eddy current inspections (ECIs) and removal of affected fan
blades before reaching 41,000 CSN. The NPRM also provided an option to
repair affected blades, which allows for an additional 28,000 cycles
before removal. This condition, if not corrected, could result in
failure of the fan blade, uncontained blade release, damage to the
engine, and damage to the airplane.

Comments

We gave the public the opportunity to participate in developing
this final rule. The following presents the comments received on the
NPRM and the FAA's response to each comment.
The Air Line Pilots Association expressed support for the NPRM.

Request To Rescind the AD

Republic Airlines requested that we rescind the AD action. Republic
Airlines does not feel that the failure of the blade is an
airworthiness issue that should be addressed by this AD. Republic
Airlines feels that in the event of a failed blade, the aircraft could
continue to a safe flight and landing. The failure would be evident
operationally and the crews would take the appropriate steps to return
the aircraft and its occupants safely to the closest airport.
We disagree. Based on the analysis that resulted in the reduction
of the life of the affected fan blades, the FAA determined an unsafe
condition exists based on the extremely high number of forecasted
events. We did not change this AD.

Request To Change Related Service Information

J-Air & Horizon Air requested that we mandate the use of specific
service bulletins in paragraph (g) of this AD. Paragraph (g) of this AD
does not specify an ECI procedure.
We partially agree. We disagree with mandating the use of specific
service bulletins in paragraph (g) of this AD because that would
preclude the use of other procedures that may be acceptable.
However, we added a statement to compliance paragraph (g) in this
AD indicating the GE service documents in which guidance can be found
for performing the ECI.

Request To Add Repetitive Inspections Intervals

Horizon Air requested that we provide instructions with regard to
the repetitive inspection interval requirements for fan blades that
have accumulated an unknown number of CSN.
We agree. We added paragraph (g)(4)(iii) of this AD to mandate a
repetitive inspection.

Request To Add Terminating Action

Horizon Air requested that we provide a designated paragraph for
terminating action. Although paragraph (h) of this AD provides fan
blade, part number (P/N) 4114T31G01, as a repair option, the repair is
not specifically given as a means to terminate the repetitive
inspections required for fan blade, P/N 4114T15P02.
We disagree. This AD requires repetitive inspections only for fan
blade, P/N 4114T15P02. Therefore, once a fan blade is repaired to P/N
4114T31G01, a repetitive inspection is not required. We did not change
this AD.

Request To Update Service Information

Horizon Air requested that all references to GE Alert Service
Bulletin (ASB) CF34-8E SB 72-A0115, R03 be revised to R04.
We agree. We revised this AD to refer to the latest service
information revision and date.

Conclusion

We reviewed the relevant data, considered the comments received,
and determined that air safety and the public interest require adopting
this final rule with the changes described previously and minor
editorial changes. We have determined that these minor changes:
Are consistent with the intent that was proposed in the
NPRM for correcting the unsafe condition; and
Do not add any additional burden upon the public than was
already proposed in the NPRM.
We also determined that these changes will not increase the
economic burden on any operator or increase the scope of this final
rule.

Related Service Information Under 1 CFR Part 51

We reviewed GE ASB CF34-8C SB 72-A0137, Revision 5 (R05), dated
June 15, 2016. This ASB identifies an approved inspection method and
provides the procedures necessary for calculating the adjusted CSN for
the initial inspection of CF34-8C fan blades.
We also reviewed CF34-8E ASB 72-A0060, Revision 5 (R05), dated June
15, 2016. This ASB identifies an approved inspection method and
provides the procedures necessary for calculating the adjusted CSN for
the initial inspection of CF34-8E fan blades.
This service information is reasonably available because the
interested parties have access to it through their normal course of
business or by the means identified in the ADDRESSES section.

Other Related Service Information

We reviewed GE ASBs CF34-8E SB 72-A0115, R04, dated December 9,
2016; and CF34-8C SB 72-A0225, R03, dated December 9, 2016. These ASBs
describe procedures for repairing fan blade, part number (P/N)
4114T15P02 to P/N 4114T31G01, with the installation of a bushing in the
pinholes.

Costs of Compliance

We estimate that this AD affects 1,986 engines installed on
airplanes of U.S. registry.
We estimate the following costs to comply with this AD:


Estimated Costs

Authority for This Rulemaking

Title 49 of the United States Code specifies the FAA's authority to
issue rules on aviation safety. Subtitle I, section 106, describes the
authority of the FAA Administrator. Subtitle VII: Aviation Programs,
describes in more detail the scope of the Agency's authority.
We are issuing this rulemaking under the authority described in
Subtitle VII, Part A, Subpart III, Section 44701: ``General
requirements.'' Under that section, Congress charges the FAA with
promoting safe flight of civil aircraft in air commerce by prescribing
regulations for practices, methods, and procedures the Administrator
finds necessary for safety in air commerce. This regulation is within
the scope of that authority because it addresses an unsafe condition
that is likely to exist or develop on products identified in this
rulemaking action.
This AD is issued in accordance with authority delegated by the
Executive Director, Aircraft Certification Service, as authorized by
FAA Order 8000.51C. In accordance with that order, issuance of ADs is
normally a function of the Compliance and Airworthiness Division, but
during this transition period, the Executive Director has delegated the
authority to issue ADs applicable to engines, propellers, and
associated appliances to the Manager, Engine and Propeller Standards
Branch, Policy and Innovation Division.

Regulatory Findings

This AD will not have federalism implications under Executive Order
13132. This AD will not have a substantial direct effect on the States,
on the relationship between the national government and the States, or
on the distribution of power and responsibilities among the various
levels of government.
For the reasons discussed above, I certify that this AD:
(1) Is not a ``significant regulatory action'' under Executive
Order 12866,
(2) Is not a ``significant rule'' under DOT Regulatory Policies and
Procedures (44 FR 11034, February 26, 1979),
(3) Will not affect intrastate aviation in Alaska to the extent
that it justifies making a regulatory distinction, and
(4) Will not have a significant economic impact, positive or
negative, on a substantial number of small entities under the criteria
of the Regulatory Flexibility Act.

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Incorporation by
reference, Safety.

Adoption of the Amendment

Accordingly, under the authority delegated to me by the
Administrator, the FAA amends 14 CFR part 39 as follows:

PART 39--AIRWORTHINESS DIRECTIVES

1. The authority citation for part 39 continues to read as follows:

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

Sec. 39.13 [Amended]

2. The FAA amends Sec. 39.13 by adding the following new airworthiness
directive (AD):