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Federal Register / Vol. 86, No. 194 / Tuesday, October 12, 2021 / Proposed Rules from a low-cycle fatigue crack in the dovetail slot for the blade attachment in the 3rd-stage compressor wheel, causing one 3rd-stage compressor blade to release. The crack initiated in the dovetail slot due to a sharp corner in the wheel slot geometry. The broaching process was identified as the cause of the crack and parts from this manufacturing lot required removal from service.
In response to this event and the manufacturers subsequent investigation, the FAA issued a final rule; request for comments, AD 2020
1613 85 FR 45769, July 30, 2020, requiring replacement of certain 3rdstage compressor wheels installed on RRC AE 3007A, AE 3007A1, AE
3007A1/1, AE 3007A1/2, AE 3007A1/3, AE 3007A1E, AE 3007A1P, and AE
3007A3 model turbofan engines before the 3rd-stage compressor wheels
accumulate a specified number of cycles. The actions required by AD
20201613 address engines that experienced high stresses at the 3rd stage compressor wheel location and accumulated cycles at a high rate. The FAA now proposes to require removal of certain AE 2100D3 3rd-stage compressor wheels that were produced in the same lot as the AE 3007 3rd-stage compressor wheels identified in AE
20201613, before they accumulate a specified number of cycles. This condition, if not addressed, could result in uncontained release of the 3rd-stage compressor wheel, damage to the engine, and damage to the airplane.

Related Service Information
FAAs Determination
The FAA estimates that this AD, if adopted as proposed, would affect 15
engines installed on airplanes of U.S.
registry.
The FAA estimates the following costs to comply with this proposed AD:

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.

The FAA reviewed Rolls-Royce Alert Service Bulletin ASB AE 2100D3A
72330, Engine3rd Stage Compressor Wheel Removal for Reduced Life Limit, dated June 11, 2021. The ASB specifies procedures for removal of a certain 3rdstage compressor wheel.
Proposed AD Requirements in This NPRM
This proposed AD would require replacement of a certain 3rd-stage compressor wheel before it accumulates a specified number of cycles.
Costs of Compliance
ESTIMATED COSTS
Action
Labor cost
Remove and replace 3rd-stage compressor wheel.

125 work-hours $85 per hour = $10,625

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.
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 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 The FAA determined that this proposed AD would not have federalism implications under Executive Order 13132. This proposed AD would not
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Parts cost
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 this proposed regulation:
1 Is not a significant regulatory action under Executive Order 12866, 2 Would not affect intrastate aviation in Alaska, and 3 Would 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

Cost per product
$32,844

Cost on U.S.
operators
$43,469

$652,035

PART 39AIRWORTHINESS
DIRECTIVES
1. The authority citation for part 39
continues to read as follows:

Authority: 49 U.S.C. 106g, 40113, 44701.
39.13

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

Rolls-Royce Corporation Type Certificate previously held by Allison Engine Company: Docket No. FAA20210874;
Project Identifier AD202100668E.
a Comments Due Date The FAA must receive comments on this airworthiness directive AD by November 26, 2021.

Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.

b Affected ADs
The Proposed Amendment
This AD applies to Rolls-Royce Corporation RRC AE 2100D3 model turboprop engines with a 3rd-stage compressor wheel, part number P/N
23084158, and with a serial number listed in Figure 1 to paragraph c of this AD.

Accordingly, under the authority delegated to me by the Administrator, the FAA proposes to amend 14 CFR part 39 as follows:

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None.
c Applicability
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