DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2013-0766; Directorate Identifier 2013-NE-26-AD;
Amendment 39-18149; AD 2014-17-08R1]
RIN 2120-AA64

Airworthiness Directives; Pratt & Whitney Canada Corp. Turboprop
Engines

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: We are revising airworthiness directive (AD) 2014-17-08 for
all Pratt & Whitney Canada Corp. (P&WC) PT6A-114 and PT6A-114A
turboprop engines. AD 2014-17-08 required initial and repetitive
borescope inspections (BSIs) of compressor turbine (CT) blades, and the
removal from service of blades that fail inspection. This new AD adds
an additional single crystal CT blade, reduces the affected population,
and corrects the Credit for Previous Action paragraph. This AD was
prompted by P&WC development of an additional single crystal CT blade
that corrects the unsafe condition. We are issuing this AD to prevent
failure of CT blades, which could result in damage to the engine and
damage to the airplane.

DATES: This AD is effective June 5, 2015.
The Director of the Federal Register approved the incorporation by
reference of a certain other publications listed in this AD as of
October 8, 2014 (79 FR 52172, September 3, 2014).

ADDRESSES: For service information identified in this AD, contact Pratt
& Whitney Canada Corp., 1000 Marie-Victorin, Longueuil, Quebec, Canada,
J4G 1A1; phone: 800-268-8000; fax: 450-647-2888; Internet: www.pwc.ca.
You may view this service information at the FAA, Engine & Propeller
Directorate, 12 New England Executive Park, Burlington, MA. For
information on the availability of this material at the FAA, call 781-
238-7125. Certain service information is also available on the Internet
at http://www.regulations.gov by searching for and locating Docket No.
FAA-2013-0766.

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-2013-
0766; 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 AD, 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: Barbara Caufield, Aerospace Engineer,
Engine Certification Office, FAA, Engine & Propeller Directorate, 12
New England Executive Park, Burlington, MA 01803; phone: 781-238-7146;
fax: 781-238-7199; email: barbara.caufield@faa.gov.

SUPPLEMENTARY INFORMATION:

Discussion

We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR
part 39 to revise AD 2014-17-08, Amendment 39-17961 (79 FR 52172,
September 3, 2014), (``AD 2014-17-08''). AD 2014-17-08 applied to all
P&WC PT6A-114 and PT6A-114A turboprop engines. The NPRM published in
the Federal Register on December 1, 2014 (79 FR 71031). The NPRM was
prompted by P&WC development of an additional single crystal CT blade
that corrects the unsafe condition. The addition of this new part
number (P/N) reduces the affected population. The NPRM proposed to
retain all the requirements of AD 2014-17-08. The NPRM also proposed to
add the additional single crystal CT blade that corrects the unsafe
condition, reduce the affected population, and correct the Credit for
Previous Action paragraph. We are issuing this AD to prevent failure of
CT blades, which could result in damage to the engine and damage to the
airplane.

Comments

We gave the public the opportunity to participate in developing
this AD. The following presents the comments received on the NPRM (79
FR 71031, December 1, 2014) and the FAA's response to each comment.

Request To Clarify Disposition of Removed CT Blades

Hawkins Aero Engineering, Inc. and another commenter requested that
we state more clearly whether pre-SB (service bulletin) PT6A-72-1669 CT
blades removed as a result of this AD can be reinstalled in the same
engine, the same model engine, or a different model engine.
We disagree. Paragraph (e)(1)(iii)(B) of this AD clearly states
that to re-install removed pre-SB PT6A-72-1669 CT blades, the blades
must pass a two-blade metallurgical inspection to determine
airworthiness in accordance with paragraph 3.B., Accomplishment
Instructions, of P&WC Service Bulletin (SB) No. PT6A-72-1669, Revision
9, dated June 28, 2013. We did not change this AD.

Request To Not Mandate Installation of Single Crystal CT Blades

One commenter requested that we not mandate the installation of
single crystal CT blades because two of the P/Ns cited as replacement
blades have experienced low-time failures, indicating a design or
manufacturing flaw.
We disagree. While there have been some failures of single crystal
CT blades on a different engine model, that failure mode is well
understood and does not affect the engines that are the subject of this
AD. For the engines that are subject to this AD, single crystal blades
provide a significant improvement in durability and a significant
reduction in CT blade failures overall. We did not change this AD.

Request To Reference Two Additional SBs

One commenter requested that we reference P&WC SBs No. PT6A-72-1727
and No. PT6A-72-1749 in addition to P&WC SB No. PT6A-72-1669 because
each one of these SBs references one of the three single crystal CT
blades that can be installed as terminating action to this AD. P&WC SB
No. PT6A-72-1669 alone only references one of the three blades listed
as terminating action in paragraph (e)(2) of this AD.
We agree. We added references to the two additional SBs in
paragraph (h)(2) of this AD.

Request To Include Alternative Method of Compliance (AMOC) for
Inspections

Hawkins Aero Engineering, Inc. requested that we include in the AD
an AMOC to allow a visual inspection, accomplished by splitting the
engine at the C-flange, as an alternative method to the required
periodic borescope inspection of pre-SB PT6A-72-1669 CT blades. The
commenter states that this suggested visual method would provide easier
detection of cracks.
We disagree. This AD contains the required method for resolving the
unsafe condition. If an operator can accomplish required actions in a
better way, or a way that better suits the operator's business
processes, and the alternative method provides an acceptable level of
safety, then the operator can apply for an AMOC to use that method to
address the unsafe condition in accordance with paragraph (g)(2) of
this AD. We did not change this AD.

Request That We Address Failures in Additional Blades

Hawkins Aero Engineering, Inc. requested that we address single
crystal CT blade failures either in this or in another AD because there
have been several low-time single crystal CT blade failures in several
different PT6 engine models, some of which are single engine
installations.
We disagree. Low-time failures that occurred on engine models not
affected by this AD are due to a failure mode that is well understood.
That failure mode does not occur in the engine models that are the
subject of this AD. We did not change this AD.

Conclusion

We reviewed the relevant data, considered the comments received,
and determined that air safety and the public interest require adopting
this AD with the changes described previously. We have determined that
these minor changes:
Are consistent with the intent that was proposed in the
NPRM (79 FR 71031, December 1, 2014) for correcting the unsafe
condition; and
Do not add any additional burden upon the public than was
already proposed in NPRM (79 FR 71031, December 1, 2014).
We also determined that these changes will not increase the
economic burden on any operator or increase the scope of this AD.

Costs of Compliance

We estimate that this AD affects 300 engines installed on airplanes
of U.S. registry. We also estimate that it would take about 4 hours per
engine to perform the required inspection and 8 hours to replace the
blades. The average labor rate is $85 per hour. Required parts cost
about $59,334 per engine. Based on these figures, we estimate the cost
of this AD on U.S. operators to be $18,106,200.

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.

Regulatory Findings

We have determined that 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 removing Airworthiness Directive (AD)
2014-17-08, Amendment 39-17961 (79 FR 52172, September 3, 2014), and
adding the following new AD: