DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 39 

[4910-13-P] 

(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. 

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 [INSERT DATE 35 DAYS AFTER DATE OF 

PUBLICATION IN THE FEDERAL REGISTER]. 

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 781-23 8-7125. 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 

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(PIN) 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)(l)(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, ofP&WC Servic.e 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 PINs cited as replacement blades have experienced lowtime failures, indicating a design or manufacturing fl aw. 

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 

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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 

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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 ofthis 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. 

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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: 

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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. 

§ 39.13 [Amended) 

2. The FAA amends§ 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: 

2014-17-08R1 Pratt & Whitney Canada Corp.: Amendment 39-18149; Docket 

No. FAA-2013-0766; Directorate Identifier 2013-NE-26-AD. 

(a) Effective Date 

This AD is effective [INSERT DATE 35 DAYS AFTER DATE OF 

PUBLICATION IN THE FEDERAL REGISTER]. 

(b) Affected ADs 

This AD replaces AD 2014-17-08, Amendment 39-17961 (79 FR 52172, 

September 3, 2014). 

(c) Applicability 

This AD applies to all Pratt & Whitney Canada Corp. (P&WC) PT6A-114 and 

PT6A-114A turboprop engines. 

(d) Unsafe Condition 

This AD was prompted by several incidents of compressor turbine (CT) blade 

failure, causing power loss, and engine failure. We are issuing this AD to prevent failure 

of CT blades, which could lead to damage to the engine and damage to the airplane. 

(e) Compliance 

Comply with this AD within the compliance times specified, unless already done. 

(1) For engines installed with CT blades other than P&WC single crystal CT 

blades, part numbers (PINs) 3072791-01 , 3072791-02, or 3079351-01 , do the following: 

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(i) Until removed, per the requirements of this AD, borescope inspect the CT 

blade leading and trailing edges, within the following intervals, whichever occurs later: 

(A) 150 operating hours after October 8, 2014; or 

(B) 500 operating hours since new; or 

(C) 500 operating hours since last borescope inspection (BSI) ofthe CT blades; or 

(D) Before next flight after the effective date of this AD. 

(ii) Thereafter, repeat the inspection required by paragraph ( e )(1 )(i) of this AD 

every 500 flight hours time since last inspection. 

(iii) At the next hot section inspection (HSI) after the effective date of this AD, 

and each HSI thereafter, replace the complete set of CT blades with any of the following: 

(A) New CT blades; 

(B) CT blades that have passed a two-blade metallurgical inspection. Use 

paragraph 3.B., Accomplishment Instructions, of P&WC Service Bulletin (SB) No. 

PT6A-72-1669, Revision 9, dated June 28,2013, to do the inspection; or 

(C) P&WC single crystal CT blades, PIN 3072791-01 , 3072791-02, or 3079351-

01. 

(2) Replacement of the complete set of CT blades with single crystal CT blades, 

PIN 3072791-01, 3072791 -02, or 3079351-01 is terminating action for the requirements 

ofparagraph (e)(l) ofthis AD. 

(3) By October 8, 2017, replace the complete set ofCT blades with P&WC single 

crystal CT blades, PIN 3072791-01 ,3072791-02, or 3079351-01. 

(f) Credit for Previous Action 

Performance of the metallurgical examination specified in paragraph ( e )(1 )(iii)(B) 

of this AD on CT blades other than P&WC single crystal CT blades, PIN 3072791-01 , 

3072791-02, or 3079351 -01 , before the effective date ofthis AD fulfills the initial 

inspection requirements of paragraph (e)(l)(i) ofthis AD. However, you must still 

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comply with the repetitive BSI requirement of paragraph (e)(l)(ii) ofthis AD until you 

complete the mandatory terminating action of paragraph ( e )(3) of this AD. 

(g) Alternative Methods of Compliance (AMOCs) 

(1) AMOCs previously approved for AD 2014-17-08, Amendment 39-17961 (79 

FR 52172, September 3, 2014) are approved for this AD. 

(2) The Manager, Engine Certification Office, FAA, may approve AMOCs for 

this AD. Use the procedures found in 14 CFR 3 9.19 to make your request. You may 

email your request to: ANE-AD-AMOC@faa.gov. 

(h) Related Information 

(1) For more information about this AD, 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. 

(2) P&WC SB No. PT6A-72-1727, dated August 23, 2013, and SB No. PT6A-72-

1749, dated September 23, 2014, which are not incorporated by reference in this AD, can 

be obtained from P&WC using the contact information in paragraph (i)(4) of this AD. 

(i) Material Incorporated by Reference 

(1) The Director of the Federal Register approved the incorporation by reference 

(IBR) ofthe service information listed in this paragraph under 5 U.S.C. 552(a) and 1 CFR 

part 51. 

(2) You must use this service information as applicable to do the actions required 

by this AD, unless the AD specifies otherwise. 

(3) The following service information was approved for IBR on October 8, 2014 

(79 FR 52172, September 3, 2014). 

(i) Pratt & Whitney Canada Service Bulletin No. PT6A-72-1669, Revision 9, 

dated June 28, 2013 . 

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(ii) Reserved. 

(4) For P&WC service information identified in this AD, contact Pratt & Whitney 

Canada Corp., 1000 Marie-Victorin, Longueuil, Quebec, Canada, J4G 1 A 1; phone: 800-

268-8000; fax : 450-647-2888; Internet: www.pwc.ca. 

(5) You may view this service information at FAA, Engine & Propeller 

Directorate, 12 New England Executive Park, Burlington, MA. For information on the 

availability ofthis material at the FAA, call 781-238-7125. 

(6) You may view this service information at the National Archives and Records 

Administration (NARA). For information on the availability of this material at NARA, 

call 202-741-6030, or go to: http://www.archives.gov/federal-register/cfrlibrlocations.html. 

Issued in Burlington, Massachusetts, on April 17, 2015. 

a~~ Acting Directorate Manager, Engine & Propeller Directorate, 

Aircraft Certification Service. 

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