[Docket No. FAA-2015-0869; Directorate Identifier 2015-NE-11-AD; Amendment 

39-18296; AD 2015-21-04[ 

RlN 2120-AA64 

Airworthiness Directives; Pratt & Whitney Turbofan Engines 

AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Final rule. 

SUMMARY: We are adopting a new airworthiness directive (AD) for certain Pratt & 

Whitney (PW) PW4164, PW4168, PW4168A, PW4164-ID, PW4168-ID, PW4168A-ID, 

and PW4170 turbofan engines. This AD was prompted by crack finds in the 6th stage 

low-pressure turbine (LPT) disk. This AD requires removal of the affected 6th stage LPT 

disks. We are issuing this AD to prevent failure of the 6th stage LPT disk, which could 

lead to an uncontained disk release, 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 publication listed in this AD as of [INSERT DATE 35 DAYS AFTER DATE OF 

PUBLICATION IN THE FEDERAL REGISTER]. 

ADDRESSES: For service information identified in this AD, contact Pratt & Whitney, 

400 Main St., East Hartford, CT 061 08; phone: 860-565-8770; fax: 860-565-4503. 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, call781-238-7125. It is also available on the Internet at 

http://www.regulations.gov by searching for and locating Docket No. FAA-2015-0869. 
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: Besian Luga, Aerospace Engineer, 

Engine Certification Office, FAA, Engine & Propeller Directorate, 12 New England 

Executive Park, Burlington, MA 01803; phone: 781-238-7750; fax: 781-238-7199; email: 

besian.luga@faa.gov. 

SUPPLEMENTARY INFORMATION: 

Discussion 

We issued a notice of proposed rulemaking (NPRM) to amend 14 CFRpart 39 by 

adding an AD that would apply to all PW PW4164, PW4168, PW4168A, PW4164-1D, 

PW4168-1D, PW4168A-1D, and PW4170 turbofan engines. The NPRM published in the 

Federal Register on June 8, 2015 (80 FR 32316). The NPRM was prompted by findings 

of cracks in the 6th stage LPT disk. The NPRM proposed to require removal of the 

affected 6th stage LPT disks. We are issuing this AD to correct the unsafe condition on 

these products. 

Comments 

We gave the public the opportunity to participate in developing this AD. The 

following presents the comment received on the NPRM (80 FR 32316, June 8, 2015) and 

the FAA's response to this comment. 

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"LPT shop visit" is defined as the removal of the 6th stage disk from the LPT rotor and 

the removal of the blades from the disk." 

Conclusion 

We reviewed the relevant data, considered the comment received, and determined 

that air safety and the public interest require adopting this AD with the change described 

previously. 

Related Service Information under 1 CFR Part 51 

We reviewed PW Service Bulletin (SB) No. PW4G-100-72-252, dated November 

18, 2014. The SB provides a list ofPW 6th stage LPT disks affected by this AD. This 

service information is reasonably available because the interested parties have access to it 

through their normal course of business or see ADDRESSES for other ways to access this 

service information. 

Costs of Compliance 

We estimate that this AD affects 18 engines installed on airplanes of U.S. registry. 

We also estimate that no additional hours will be required per engine to comply with this 

AD because the engine is already disassembled in the shop when we require the part to be removed. The average labor rate is $85 per hour. We estimate that 6 engines will require 

replacement parts during an LPT shop visit, and that the prorated replacement parts cost 

will be $108,800 per engine. Based on these figures, we estimate the cost of this AD on 

U.S. operators to be $652,800. 

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authority. 

We are issuing this rulemaking under the authority described in Subtitle VII, 

Part A, Subpart III, Section 44 701: "General requirements." Under that section, Congress 

charges the FAA with promoting safe flight of civil aircraft in air connnerce 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 

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. 

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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. 

§ 39.13 [Amended] 

2. The FAA amends§ 39.13 by adding the following new airworthiness directive 

(AD): 

2015-21-04 Pratt & Whitney: Amendment 39-18296; Docket No. FAA-2015-0869; 

Directorate Identifier 2015-NE-11-AD. 

(a) Effective Date 

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

PUBLICATION IN THE FEDERAL REGISTER]. 

(b) Affected ADs 

None. 

(c) Applicability 

This AD applies to all Pratt & Whitney (PW) PW4164, PW4168, PW4168A, 

PW4164-ID, PW4168-ID, PW4168A-ID, and PW4170 turbofan engines with 6th stage 

pressure turbine (LPT) disks, part number 50N886, installed. 

(d) Unsafe Condition 

Ibis AD was prompted by crack finds in the 6th stage LPT disk. We are issuing 

this AD to prevent failure of the 6th stage LPT disk, which could lead to an uncontained 

disk release, damage to the engine, and damage to the airplane. 

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ofPW Service Bulletin No. PW4G-l 00-72-252. dated November 18. 2014. 

(f) Definition 

For the purpose of this AD, an "LPT shop visit" is defined as the removal of the 

6th stage disk from the LPT rotor and the removal of the blades from the disk. (g) Alternative Methods of Compliance (AMOCs) 

The Manager, Engine Certification Office, FAA, may approve AMOCs for this 

AD. Use the procedures found in 14 CFR 39.19 to make your request. You may email 

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

(h) Related Information 

For more information about this AD, contact Besian Luga, Aerospace Engineer, 

Engine Certification Office, FAA, Engine & Propeller Directorate, 12 New England 

Executive Park. Burlington. MA 01803; phone: 781-238-7750; fax: 781-238-7199; email: 

besian.luga@faa.gov. 

(i) Material Incorporated by Reference 

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

(IBR) of the service information listed in this paragraph under 5 U.S.C. 552(a) and I 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 [INSERT DATE 

35 DAYS AFTER DATE OF PUBLICATION IN THE FEDERAL REGISTER]. 

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400 Main St., East Hartford, CT 06108; phone: 860-565-8770; fax: 860-565-4503. 

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

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

availability of this material at the FAA, ca\1781-238-7125. 

(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, 

call202-741-6030, or go to: http://www.archives.gov/federal-register/cfr/ibrlocations.html. 

Issued in Burlington, Massachusetts, on October 9, 2015. 

Acting Directorate Manager, Engine & Propeller Directorate, 

Aircraft Certification Service. 

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