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Federal Register / Vol. 86, No. 33 / Monday, February 22, 2021 / Proposed Rules 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.
FAA20201179; Project Identifier AD
202000818E 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 Kevin M. Clark, 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 was notified by the manufacturer that a crack on the HPT
rotor stage 1 disk was found during an inspection. Subsequent investigation by the manufacturer determined that the crack on the HPT rotor stage 1 disk was caused by increased stress on the HPT
rotor stage 1 disk as a result of flangeto-flange cracking on the HPT thermal shield. This condition, if not addressed, could result in failure of the HPT rotor stage 1 disk, failure of the HPT rotor stage 2 disk, uncontained release of the HPT rotor stage 1 and stage 2 disks, damage to the engine, and damage to the airplane.
FAAs Determination The FAA is issuing this NPRM after determining that the unsafe condition
described previously is likely to exist or develop on other products of the same type design.
Related Service Information The FAA reviewed ESM 725300
High Pressure Turbine Rotor AssemblyDisassembly ESM 7253
00 from the GE CF680A Engine Manual GEK72501Rev 89, dated February 15, 2020. ESM 725300
describes procedures for the removal of the HPT thermal shield, the HPT rotor stage 1 disk, and the HPT rotor stage 2
disk.
Proposed AD Requirements in This NPRM
This proposed AD would require repetitive visual inspection and FPI of the HPT thermal shield at every piece part opportunity of the HPT rotor stage 1 disk, HPT rotor stage 2 disk, or the HPT thermal shield. Depending on the results of the inspections, this proposed AD requires the removal from service of the HPT thermal shield, HPT rotor stage 1 disk, and the HPT rotor stage 2 disk.
Costs of Compliance The FAA estimates that this AD, if adopted as proposed, would affect 1,084
engines installed on airplanes of U.S.
registry.
The FAA estimates the following costs to comply with this proposed AD:

ESTIMATED COSTS
Action
Labor cost
Parts cost
Cost per product
Cost on U.S.
operators
Perform FPI and visual inspection of HPT
thermal shield.

2 work-hours $85 per hour = $170

$0

$170

$184,280

The FAA estimates the following costs to do any necessary replacements that would be required based on the
results of the proposed inspection. The agency has no way of determining the
number of aircraft that might need these replacements.

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ON-CONDITION COSTS
Action
Labor cost
Replace HPT thermal shield
Replace HPT rotor stage 1 disk
Replace HPT rotor stage 2 disk

2 work-hours $85 per hour = $170
2 work-hours $85 per hour = $170
2 work-hours $85 per hour = $170

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:

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Aviation Programs, describes in more detail the scope of the Agencys authority.
The FAA is issuing this rulemaking under the authority described in Subtitle VII, Part A, Subpart III, Section
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Parts cost $209,600
799,700
364,600

Cost per product $209,770
799,870
364,770

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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