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44656

Federal Register / Vol. 86, No. 154 / Friday, August 13, 2021 / Proposed Rules
address the unsafe condition on these products. The MCAI states:

by searching for and locating Docket No.
FAA20210662.

Proposed AD Requirements in This NPRM

The Modulated Air System MAS
optimises cooling air, extracted from the compressor, where full flow is not required at cruise conditions. It is only active during cruise. Recently, occurrences have been reported of finding high levels of wear on the seal fins on a small number of high pressure turbine triple seals, Part Number FW3448.
The effect on the secondary air system was conservatively assessed due to the resultant increased turbine cooling air leakage, which changes the cooling flow around the intermediate pressure IP turbine disc.
This condition, if not corrected, could lead to temperature increase at the IP turbine disc rim when the MAS is active, possibly resulting in IP turbine disc failure and high energy debris release, with consequent damage to, and reduced control of, the aeroplane. To address this potential unsafe condition, Rolls-Royce has issued the NMSB, providing instructions to manually lock-out deactivate the MAS control valves.
For the reason described above, this EASA AD requires to deactivate the MAS
control valves. This EASA AD also specifies that the Master Minimum Equipment List MMEL item for MAS inoperative, which has a limit of 120 days, does not apply when the system is manually deactivated.

FAAs Determination
This proposed AD would require manual deactivation of the MAS control valves. Manual deactivation of the MAS
control valves changes the engine to an approved configuration that will produce engine indicating and crew alerting system EICAS status messages that do not indicate inoperative failed equipment. Consequently, when these messages are displayed, the operators existing FAA-approved minimum equipment list MEL instructions and limitations, including the 120-day operation limitation, do not apply.

You may obtain further information by examining the MCAI in the AD
docket at https www.regulations.gov
This product has been approved by EASA and is approved for operation in the United States. Pursuant to the FAAs bilateral agreement with the European Community, EASA has notified the FAA
of the unsafe condition described in the MCAI and service information. The FAA is issuing this AD because the agency evaluated all the relevant information provided by EASA and has determined that the unsafe condition described previously is likely to exist or develop in other products of the same type design.
Related Service Information Under 1
CFR Part 51
The FAA reviewed Rolls-Royce Alert Non-Modification Service Bulletin NMSB Trent 1000 75AK642, Initial Issue, dated November 30, 2020. This service information specifies procedures for deactivating the MAS control valves.
This service information is reasonably available because the interested parties have access to it through their normal course of business or by the means identified in ADDRESSES.

Interim Action The FAA considers that this proposed AD would be an interim action. If final action is later identified, the FAA might consider additional rulemaking.
Costs of Compliance The FAA estimates that this AD, if adopted as proposed, would affect 4
engines installed on airplanes of U.S.
registry.
The FAA estimates the following costs to comply with this proposed AD:

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ESTIMATED COSTS
Action
Labor cost
Parts cost
Cost per product
Cost on U.S.
operators
Deactivate the MAS control valves

2 work-hours $85 per hour = $170

$0

$170

$680

Authority for This Rulemaking
Regulatory Findings
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.

The FAA 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.
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.

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16:19 Aug 12, 2021

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List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.

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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 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 Deutschland Ltd & Co KG Type Certificate previously held by RollsRoyce plc: Docket No. FAA20210662;
Project Identifier MCAI202100031E.
a Comments Due Date The FAA must receive comments on this airworthiness directive AD by September 27, 2021.
b Affected ADs None.

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