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Federal Register / Vol. 86, No. 105 / Thursday, June 3, 2021 / Proposed Rules
FAA20210447; 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:
Mark Taylor, Aviation Safety Engineer, ECO Branch, FAA, 1200 District Avenue, Burlington, MA 01803; phone:
781 2387229; fax: 781 2387199;
email: Mark.Taylor@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.
FAA20210447; Project Identifier AD
202100131E 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 this 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
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 received about this NPRM.
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 Mark Taylor, 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.

develop on other products of the same type design.

Background The FAA received reports of cracks in the HPC rotor shaft that resulted in vibration and subsequent IFSDs and UERs. The manufacturer determined that the threads on the HPC rotor shaft were not optimized for load distribution, which resulted in vibration stresses. During one occurrence, oil was released at the high-pressure turbine HPT disk bore location. The manufacturer redesigned the HPC front hub and HPC rotor shaft for increased durability and decreased vibration stress. The redesigned HPC front hub is made from nickel to help with corrosion resistance. The threads on the HPC rotor shaft were also redesigned to help distribute the load on the threads and decrease vibration stress. This condition, if not addressed, could result in release of an HPT disk, damage to the engine, and damage to the airplane.

Differences Between This Proposed AD
and the Service Information
FAAs Determination The FAA is issuing this NPRM after determining that the unsafe condition described previously is likely to exist or
Related Service Information The FAA reviewed Pratt & Whitney Service Bulletin SB PW1000GA72
00015400A930AD, Issue No. 001, dated May 7, 2021 PW1000GA72
00015400A930AD, and Pratt &
Whitney SB PW1000GA72000101
00B930AD, Issue No. 001, dated May 7, 2021 SB PW1000GA72000101
00B930AD. These SBs describe procedures for removing and replacing the HPC front hub and HPC rotor shaft.
Proposed AD Requirements in This NPRM
This proposed AD would require removal and replacement of the HPC
front hub and HPC rotor shaft.

Pratt & Whitney SB PW1000GA72
00015400A930AD and Pratt &
Whitney SB PW1000GA72000101
00B930AD provide instructions to concurrently perform the actions in Pratt & Whitney SB PW1000GA72
00015700A930AD and SB
PW1000GA7200010500B930A
D, respectively. This AD does not require performance of the actions described in Pratt & Whitney SB
PW1000GA7200015700A930A
D or SB PW1000GA7200010500B
930AD since these SBs describe ring seal replacement, which is not related to the unsafe condition addressed by this AD.
Costs of Compliance The FAA estimates that this AD, if adopted as proposed, would affect 94
engines installed on airplanes of U.S.
registry.
The FAA estimates the following costs to comply with this proposed AD:

khammond on DSKJM1Z7X2PROD with PROPOSALS

ESTIMATED COSTS
Action
Labor cost
Replace HPC front hub and HPC rotor shaft.

25.75 work-hours $85 per hour =
$2,188.75.

Authority for This Rulemaking Title 49 of the United States Code specifies the FAAs 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 Agencys authority.

VerDate Sep<11>2014

16:29 Jun 02, 2021

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Parts cost
The FAA is 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
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$120,090

Cost per product
Cost on U.S.
operators
$122,278.75

$11,494,202.50

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.

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