[4910-13-P]

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

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

RIN 2120-AA64

Airworthiness Directives; Pratt & Whitney Turbofan Engines

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

SUMMARY: We propose to adopt a new airworthiness directive (AD) for all Pratt & 

Whitney (PW) PW4164, PW4168, PW4168A, PW4164-1D, PW4168-1D, PW4168A-1D,

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

stage low-pressure turbine (LPT) disk. This proposed AD would require removal of 

affected 6

th stage LPT disks. We are proposing 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: We must receive comments on this proposed AD by [INSERT DATE 60

DAYS AFTER DATE OF PUBLICATION IN THE Federal Register].

ADDRESSES: You may send comments, using the procedures found in 14 CFR 11.43 

and 11.45, by any of the following methods:

• Federal eRulemaking Portal: Go to http://www.regulations.gov. Follow the 

instructions for submitting comments.

• Fax: 202-493-2251.

• Mail: U.S. Department of Transportation, Docket Operations, M-30, West 

Building Ground Floor, Room W12-140, 1200 New Jersey Avenue SE., Washington, DC 

20590.
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• Hand Delivery: Deliver to Mail address above between 9 a.m. and 5 p.m., 

Monday through Friday, except Federal holidays.

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

400 Main St., East Hartford, CT 06108; 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, call 781-238-7125.

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-2015-0869; 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 proposed AD, the regulatory evaluation, any

comments received, and other information. The street address for the Docket Office 

(phone: 800-647-5527) is in the ADDRESSES section. Comments will be available in the 

AD docket shortly after receipt.

FOR FURTHER INFORMATION CONTACT: Katheryn Malatek, Aerospace 

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

England Executive Park, Burlington, MA 01803; phone: 781-238-7747; fax: 781-238-

7199; email: katheryn.malatek@faa.gov.

SUPPLEMENTARY INFORMATION:

Comments Invited

We invite you to send any written relevant data, views, or arguments about this 

NPRM. Send your comments to an address listed under the ADDRESSES section. 

Include “Docket No. FAA-2015-0869; Directorate Identifier 2015-NE-11-AD” at the 

beginning of your comments. We specifically invite comments on the overall regulatory, 

economic, environmental, and energy aspects of this NPRM. We will consider all 
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comments received by the closing date and may amend this NPRM because of those 

comments.

We will post all comments we receive, without change, to 

http://www.regulations.gov, including any personal information you provide. We will 

also post a report summarizing each substantive verbal contact we receive about this 

NPRM.

Discussion

We received reports of two crack finds in the front and rear knife-edge seals on 

the forward arm of the 6th stage LPT disk during a scheduled heavy maintenance shop 

visit. The suspected root cause of the cracks is residual stress introduced during knifeedge weld repair. This condition, if not corrected, could result in failure of the 6

th stage 

LPT disk, which could lead to an uncontained disk release, damage to the engine, and 

damage to the airplane.

Related Service Information under 1 CFR Part 51

We reviewed PW Service Bulletin No. PW4G-100-72-252, dated November 18, 

2014. This service information identifies and directs removal of the suspect 6th stage LPT 

disks. 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.

FAA’s Determination

We are proposing this NPRM because we evaluated all the relevant information 

and determined the unsafe condition described previously is likely to exist or develop in 

other products of the same type design.

Proposed AD Requirements

This NPRM would require removing certain serial number 6th stage LPT disks, 

part number 50N886.
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Costs of Compliance

We estimate that this proposed AD would affect 18 engines installed on airplanes 

of U.S. registry. We also estimate that no additional hours would be required per engine 

to comply with this proposed 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 of the engines will require replacement parts during an LPT shop visit, 

and that the prorated replacement parts cost would be $108,800 per engine. Based on 

these figures, we estimate the cost of this proposed AD on U.S. operators to be $652,800.

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 determined that this proposed AD would not have federalism implications 

under Executive Order 13132. This proposed AD would 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.
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For the reasons discussed above, I certify this proposed regulation:

(1) Is not a “significant regulatory action” under Executive Order 12866,

(2) Is not a “significant rule” under the 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.

The Proposed Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA 

proposes to amend 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):

Pratt & Whitney: Docket No. FAA-2015-0869; Directorate Identifier 2015-NE-11-AD.

(a) Comments Due Date

We must receive comments by [INSERT DATE 60 DAYS AFTER DATE OF 

PUBLICATION IN THE Federal Register].

(b) Affected ADs

None.
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(c) Applicability

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

PW4164-1D, PW4168-1D, PW4168A-1D, and PW4170 turbofan engines with 6

th stage 

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

(d) Unsafe Condition

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

this AD to prevent failure of the 6

th stage LPT disk, which could lead to an uncontained

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

(e) Compliance

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

At the next LPT shop visit after the effective date of this AD, remove from service 6th

stage LPT disks with serial numbers listed in the Accomplishment Instructions, Table 1, 

of PW Service Bulletin (SB) No. PW4G-100-72-252, dated November 18, 2014.

(f) Definition

For the purpose of this AD, an “LPT shop visit” is defined as maintenance which 

involves disassembly of the LPT rotor module.

(i) 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.

(j) Related Information

(1) For more information about this AD, contact Katheryn Malatek, Aerospace 

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

England Executive Park, Burlington, MA 01803; phone: 781-238-7747; fax: 781-238-

7199; email: katheryn.malatek@faa.gov.
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(2) PW SB No. PW4G-100-72-252, dated November 18, 2014, can be obtained 

from Pratt & Whitney using the contact information in paragraph (j)(3) of this proposed 

rule.

(3) For service information identified in this proposed rule, contact Pratt & 

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

4503.

(4) 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.

Issued in Burlington, Massachusetts, on May 12, 2015.

Colleen M. D’Alessandro,

Assistant Directorate Manager, Engine & Propeller Directorate,

Aircraft Certification Service.