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Proposed Rules
Federal Register Vol. 86, No. 139
Friday, July 23, 2021

This section of the FEDERAL REGISTER
contains notices to the public of the proposed issuance of rules and regulations. The purpose of these notices is to give interested persons an opportunity to participate in the rule making prior to the adoption of the final rules.

DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration 14 CFR Part 39
Docket No. FAA20210577; Project Identifier AD202100470E
RIN 2120AA64

Airworthiness Directives; Pratt &
Whitney Division Turbofan Engines Federal Aviation Administration FAA, DOT.
ACTION: Notice of proposed rulemaking NPRM.
AGENCY:

The FAA proposes to supersede Airworthiness Directive AD
20210516, which applies to certain Pratt & Whitney Division PW PW4164, PW41641D, PW4168, PW41681D, PW4168A, PW4168A1D, and PW4170
model turbofan engines. AD 202105
16 requires initial and repetitive replacements of the low-pressure turbine LPT 4th-stage air sealing ring segment assemblies with parts eligible for installation. AD 20210516 also requires initial and repetitive dimensional inspections of the LPT case for bulging and, depending on the results of the dimensional inspections, repair or replacement of the LPT case.
Since the FAA issued AD 20210516, the FAA was notified of an inadvertent omission in the LPT 4th-stage air sealing ring segment assembly part numbers.
This proposed AD would correct this omission. The FAA is proposing this AD
to address the unsafe condition on these products.
DATES: The FAA must receive comments on this proposed AD by September 7, 2021.

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SUMMARY:

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 https www.regulations.gov. Follow the instructions for submitting comments.
Fax: 202 4932251.

ADDRESSES:

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Mail: U.S. Department of Transportation, Docket Operations, M
30, West Building Ground Floor, Room W12140, 1200 New Jersey Avenue SE, Washington, DC 20590.
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 NPRM, contact Pratt & Whitney, 400 Main Street, East Hartford, CT
06118; phone: 800 5650140; email:
help24@prattwhitney.com; website:
https prattwhitney.com. You may view this service information at the Airworthiness Products Section, Operational Safety Branch, FAA, 1200
District Avenue, Burlington, MA 01803.
For information on the availability of this material at the FAA, call 781 238
7759.
Examining the AD Docket You may examine the AD docket at https www.regulations.gov by searching for and locating Docket No.
FAA20210577; or in person at Docket Operations between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD docket contains this NPRM, any comments received, and other information. The street address for Docket Operations is listed above.
FOR FURTHER INFORMATION CONTACT:
Carol Nguyen, Aviation Safety Engineer, ECO Branch, FAA, 1200 District Avenue, Burlington, MA 01803; phone:
781 2387655; fax: 781 2387199;
email: carol.nguyen@faa.gov.
SUPPLEMENTARY INFORMATION:
Comments Invited The FAA invites you to send any written relevant data, views, or arguments about this proposal. Send your comments to an address listed under ADDRESSES. Include Docket No.
FAA20210577; Project Identifier AD
202100470E at the beginning of your comments. The most helpful comments reference a specific portion of the proposal, explain the reason for any recommended change, and include supporting data. The FAA will consider all comments received by the closing date and may amend the proposal because of those comments.
Except for Confidential Business Information CBI as described in the following paragraph, and other information as described in 14 CFR

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11.35, the FAA will post all comments received, without change, to https
www.regulations.gov, including any personal information you provide. The agency will also post a report summarizing each substantive verbal contact the FAA receives about this proposed AD.
Confidential Business Information CBI is commercial or financial information that is both customarily and actually treated as private by its owner.
Under the Freedom of Information Act FOIA 5 U.S.C. 552, CBI is exempt from public disclosure. If your comments responsive to this NPRM
contain commercial or financial information that is customarily treated as private, that you actually treat as private, and that is relevant or responsive to this NPRM, it is important that you clearly designate the submitted comments as CBI. Please mark each page of your submission containing CBI
as PROPIN. The FAA will treat such marked submissions as confidential under the FOIA, and they will not be placed in the public docket of this NPRM. Submissions containing CBI
should be sent to Carol Nguyen, Aviation Safety Engineer, ECO Branch, FAA, 1200 District Avenue, Burlington, MA 01803. Any commentary that the FAA receives which is not specifically designated as CBI will be placed in the public docket for this rulemaking.
Background The FAA issued AD 20210516, Amendment 3921459 86 FR 17287, April 2, 2021, AD 20210516, for certain PW PW4164, PW41641D, PW4168, PW41681D, PW4168A, PW4168A1D, and PW4170 model turbofan engines with LPT 4th-stage air sealing ring segment assemblies, part number P/N 50N46301 or P/N
50N52601, installed. AD 20210516
was prompted by six reports from the manufacturer concerning LPT 4th-stage vane cluster assemblies leaning back and notching into rotating LPT 4th-stage blades, causing some blades to fracture and release. These incidents resulted in an aborted takeoff, air turnbacks, engine surges, high vibrations, and unplanned engine removals. The incidents were attributed to the LPT 4th-stage air sealing ring segment assemblies moving into the LPT 4th-stage blades knife edge seals, resulting in damage to the ring
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