[Federal Register Volume 86, Number 76 (Thursday, April 22, 2021)]
[Proposed Rules]
[Pages 21233-21237]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-07660]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2021-0306; Project Identifier MCAI-2020-01493-E]
RIN 2120-AA64


Airworthiness Directives; Rolls-Royce Deutschland Ltd & Co KG 
(Type Certificate Previously Held by Rolls-Royce plc) Turbofan Engines

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: The FAA proposes to supersede Airworthiness Directive (AD) 
2020-15-12, which applies to certain Rolls-Royce Deutschland Ltd & Co 
KG (RRD) Trent 1000 model turbofan engines. AD 2020-15-12 requires 
initial and repetitive ultrasonic or visual inspections of the 
intermediate-pressure compressor (IPC) stage 1 rotor blade root (front 
face), IPC stage 2 rotor blade root (front and rear face), and IPC 
shaft stage 2 dovetail post (front face), and removal of any cracked 
parts from service. AD 2020-15-12 also requires an inspection after 
asymmetric power and cabin depressurization events. Since the FAA 
issued AD 2020-15-12, the manufacturer introduced IPC stage 1 and stage 
2 rotor blades in kitted sets, which terminate the need for initial and 
repetitive ultrasonic or visual inspections for certain IPC parts. This 
proposed AD would continue to require initial and repetitive ultrasonic 
or visual inspections of certain IPC parts until replacement of the IPC 
stage 1 and stage

[[Page 21234]]

2 rotor blades with redesigned IPC stage 1 and stage 2 rotor blades in 
kitted sets. 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 June 7, 
2021.

ADDRESSES: 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) 493-2251.
     Mail: U.S. Department of Transportation, Docket 
Operations, M-30, West Building Ground Floor, Room W12-140, 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 Rolls-
Royce plc, Corporate Communications, P.O. Box 31, Derby, DE24 8BJ, 
United Kingdom; phone: +44 (0)1332 242424; fax: +44 (0)1332 249936; 
email: https://www.rolls-royce.com/contact-us/civil-aerospace.aspx; 
website: https://www.rolls-royce.com/contact-us.aspx. You may view this 
service information at the FAA, Airworthiness Products Section, 
Operational Safety Branch, 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. FAA-2021-0306; 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, the 
mandatory continuing airworthiness information (MCAI), any comments 
received, and other information. The street address for Docket 
Operations is listed above.

FOR FURTHER INFORMATION CONTACT: Kevin Clark, Aviation Safety Engineer, 
ECO Branch, FAA, 1200 District Avenue, Burlington, MA 01803; phone: 
(781) 238-7088; fax: (781) 238-7199; email: [email protected].

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. FAA-2021-0306; Project Identifier 
MCAI-2020-01493-E'' 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 NPRM 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 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 Kevin 
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 issued AD 2020-15-12, Amendment 39-21175 (85 FR 45081, July 
27, 2020), (AD 2020-15-12), for certain RRD Trent 1000-A2, Trent 1000-
AE2, Trent 1000-C2, Trent 1000-CE2, Trent 1000-D2, Trent 1000-E2, Trent 
1000-G2, Trent 1000-H2, Trent 1000-J2, Trent 1000-K2, and Trent 1000-L2 
model turbofan engines. AD 2020-15-12 was prompted by IPC rotor blade 
separations resulting in engine failures. Subsequently, the 
manufacturer identified the need to add new inspections and an optional 
terminating action, amend the asymmetric power condition for engine 
inspection, and to add an inspection after a cabin depressurization 
event. AD 2020-15-12 requires initial and repetitive ultrasonic or 
visual inspections of the IPC stage 1 rotor blade root (front face), 
IPC stage 2 rotor blade root (front and rear face), and IPC shaft stage 
2 dovetail posts (front face), and removal of any cracked parts from 
service. AD 2020-15-12 also requires an inspection after asymmetric 
power and cabin depressurization events. The agency issued AD 2020-15-
12 to prevent failure of the IPC rotor blades.

Actions Since AD 2020-15-12 Was Issued

    Since the FAA issued AD 2020-15-12, the European Union Aviation 
Safety Agency (EASA), which is the Technical Agent for the Member 
States of the European Community, has issued EASA AD 2020-0240, dated 
November 5, 2020 (referred to after this as ``the MCAI''), to address 
the unsafe condition on these products. The MCAI states:
    Occurrences were reported on Rolls-Royce Trent 1000 `Pack C' 
engines, where some IPC Rotor 1 and Rotor 2 blades were found cracked.
    This condition, if not detected and corrected, could lead to in-
flight blade release, possibly resulting in reduced control of the 
aeroplane.
    To address this potential unsafe condition, Rolls-Royce initially 
issued Alert NMSB TRENT 1000 72-AJ814 and 72-AJ819 to provide 
inspection instructions for IPC Rotor 1 blades, and IPC Rotor 2 blades 
and IPC shaft Stage 2 dovetail posts, respectively. Rolls-Royce also 
issued NMSB TRENT 1000 72-J871 to provide rework instructions for the 
affected parts, and Alert NMSB TRENT 1000 72-AJ869 to inspect those 
post-rework parts.
    Consequently, EASA issued AD 2017-0248 to require repetitive 
inspections of the affected IPC Rotor blades and IPC shaft Stage 2 
dovetail posts and, depending on findings, removal from service of the 
engine for corrective action.
    After that [EASA] AD was issued, Rolls-Royce issued Alert NMSB 
TRENT 1000 72-AK058 to provide instructions for a one-time on-wing 
inspection. Consequently, EASA issued AD 2018-0073, retaining the 
requirements of EASA AD 2017-0248, which was superseded, to require an 
additional borescope inspection of certain engines and, depending on 
findings, removal from service of the engine for corrective action.
    After that [EASA] AD was issued, it was determined that repetitive 
borescope inspections are necessary on all engines to ensure fleet-wide

[[Page 21235]]

continued safe operation. Consequently, Rolls-Royce revised Alert NMSB 
TRENT 1000 72-AJ869, Alert NMSB TRENT 1000 72-AJ814, Alert NMSB TRENT 
1000 72-AJ819 and NMSB TRENT 1000 72-J871, and issued NMSB TRENT 1000 
72-AK060 to consolidate all inspection instructions. Consequently, EASA 
issued AD 2018-0084 (later revised), retaining the requirements of EASA 
AD 2018-0073, which was superseded, and requiring repetitive on-wing 
borescope inspections of the affected Rotor 1 parts and affected Rotor 
2 parts and, depending on findings, removal from service of the engine 
for corrective action. That AD also introduced specific requirements 
for engines installed on aeroplanes involved in ETOPS, and inspection 
following operation in asymmetric power conditions.
    Rolls-Royce then introduced NMSB Trent 1000 72-AK092 to provide 
inspections for the rear face of the Rotor 2 blades and NMSB TRENT 1000 
72-AK060 was revised (R1) accordingly. Later, Rolls-Royce developed mod 
72-J941, installing improved IPC Stage 1 and Stage 2 rotor blades, and 
issued the modification SB, providing the necessary instructions for 
in-service application. EASA issued AD 2018-0084R2 to exclude post-mod 
72-J941 engines from the Applicability and introducing the modification 
SB as terminating action for the repetitive inspections as required by 
that [EASA] AD.
    After that [EASA] AD was issued, Rolls-Royce issued NMSB TRENT 1000 
72-AK313 and revised Alert NMSB TRENT 1000 72-AJ814, 72-AJ819 and 72-
AK092 to introduce new inspections, new thresholds and new intervals, 
depending on engine configuration. These inspections are for all 
operations, ETOPS and non-ETOPS. The latest revision of the NMSB also 
amended the asymmetric power conditions for engine inspection and 
introduced cabin depressurisation as an event to trigger engine 
inspection(s). Consequently, EASA issued AD 2019-0250 to require 
introduction of the new inspections, replacing those previously imposed 
by EASA AD 2018-0084R2 (through NMSB TRENT 1000 72-AK060), and to 
remove the references to Engine Health Monitoring messages and ETOPS-
related requirements.
    Since that [EASA] AD was issued, it was discovered that the 
manufacturing distribution of the individual blade frequencies could 
differ from the assumed values during certification of the SB TRENT 
1000 72-J941, which means there may not be sufficient margin to prevent 
the blades from experiencing high vibration levels. Prompted by these 
findings, Rolls-Royce issued the modification SB to provide blade 
kitting instructions.
    You may obtain further information by examining the MCAI in the AD 
docket at https://www.regulations.gov by searching for and locating 
Docket No. FAA-2021-0306.

FAA's Determination

    This product has been approved by EASA and is approved for 
operation in the United States. Pursuant to our 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 NPRM because the agency evaluated all the relevant 
information provided by EASA and determined 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 72-AK313, Revision 1, dated August 22, 2019; 
and Rolls-Royce Alert Service Bulletin (SB) Trent 1000 72-AK430, 
Initial Issue, dated August 17, 2020. Rolls-Royce Alert NMSB Trent 1000 
72-AK313 defines the initial inspection threshold and repeat inspection 
intervals for Trent 1000 IPC stage 1 rotor blade, IPC stage 2 rotor 
blade, and IPC shaft stage 2 dovetail posts. Rolls-Royce Alert SB Trent 
1000 72-AK430 introduces the IPC stage 1 and stage 2 rotor blades in 
kitted sets and provides kitting instructions. 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.

Other Related Service Information

    The FAA reviewed Rolls-Royce Alert NMSB Trent 1000 72-AJ814, 
Revision 5, dated May 3, 2019; Rolls-Royce Alert NMSB Trent 1000 72-
AJ819, Revision 4, dated May 3, 2019; Rolls-Royce Alert NMSB Trent 1000 
72-AK092, Revision 4, dated May 3, 2019; Rolls-Royce SB Trent 1000 72-
J871, Revision 6, dated December 12, 2019; and Rolls-Royce SB Trent 
1000 72-J941, Revision 1, dated February 6, 2019.
    Rolls-Royce Alert NMSB Trent 1000 72-AJ814 describes procedures for 
performing an ultrasonic inspection (USI) of the IPC stage 1 rotor 
blades. Rolls-Royce Alert NMSB Trent 1000 72-AJ819 describes procedures 
for performing a visual borescope inspection of the IPC stage 2 rotor 
blades and IPC shaft stage 2 dovetail posts. Rolls-Royce Alert NMSB 
Trent 1000 72-AK092 describes procedures for performing a USI of the 
IPC stage 2 rotor blades. Rolls-Royce SB Trent 1000 72-J871 describes 
procedures for reworking or replacing the affected parts. Rolls-Royce 
SB Trent 1000 72-J941 describes procedures for installing the 
redesigned IPC stage 1 and stage 2 rotor blades.

Proposed AD Requirements in This NPRM

    This proposed AD would retain certain requirements of AD 2020-15-
12. This proposed AD would continue to require initial and repetitive 
ultrasonic or visual inspection of the IPC stage 1 rotor blade root 
(front face), IPC stage 2 rotor blade root (front and rear face), and 
IPC shaft stage 2 dovetail post (front face), removal of any cracked 
parts from service, and an inspection after asymmetric power and cabin 
depressurization events until the installation of the IPC stage 1 and 
stage 2 rotor blades in kitted sets. As a terminating action, this AD 
would require replacement of IPC stage 1 and stage 2 rotor blades with 
IPC stage 1 and stage 2 rotor blades in kitted sets.

Costs of Compliance

    The FAA estimates that this AD, if adopted as proposed, would 
affect 7 engines installed on airplanes of U.S. registry.
    The FAA estimates the following costs to comply with this proposed 
AD:

                                                 Estimated Costs
----------------------------------------------------------------------------------------------------------------
                                                                                     Cost per      Cost on U.S.
                Action                         Labor cost           Parts cost        product        operators
----------------------------------------------------------------------------------------------------------------
Inspect the IPC stage 1 rotor blade     20 work-hours x $85 per               $0          $1,700         $11,900
 root (Front Face).                      hour = $1,700.

[[Page 21236]]

 
Inspect the IPC stage 2 rotor blade     6 work-hours x $85 per                 0             510           3,570
 root (Front Face) and IPC shaft stage   hour = $510.
 2 dovetail post (Front Face).
Inspect the IPC stage 2 rotor blade     10 work-hours x $85 per                0             850           5,950
 root (Rear Face).                       hour = $850.
Replace all 34 IPC stage 1 rotor        280 work-hours x $85 per          52,360          76,160         533,120
 blades (mandatory terminating action).  hour = $23,800.
Replace all 49 IPC stage 2 rotor        280 work-hours x $85 per          48,755          72,555         507,885
 blades (mandatory terminating action).  hour = $23,800.
----------------------------------------------------------------------------------------------------------------

    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:

                                               On-Condition Costs
----------------------------------------------------------------------------------------------------------------
                                                                                                     Cost per
                    Action                                 Labor cost               Parts cost        product
----------------------------------------------------------------------------------------------------------------
Replace all 34 IPC stage 1 rotor blades.......  280 work-hours x $85 per hour =          $52,360         $76,160
                                                 $23,800.
Replace all 49 IPC stage 2 rotor blades.......  280 work-hours x $85 per hour =           48,755          72,555
                                                 $23,800.
Replace the IPC drum assembly.................  144 work-hours x $85 per hour =        1,370,000       1,382,240
                                                 $12,240.
----------------------------------------------------------------------------------------------------------------

Authority for This Rulemaking

    Title 49 of the United States Code specifies the FAA's 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 Agency's 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 has 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 that the 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

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

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 39--AIRWORTHINESS DIRECTIVES

0
1. The authority citation for part 39 continues to read as follows:

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


Sec.  39.13   [Amended]

0
2. The FAA amends Sec.  39.13 by:
0
a. Removing Airworthiness Directive AD 2020-15-12, Amendment 39-21175 
(85 FR 45081, July 27, 2020); and
0
b. Adding the following new airworthiness directive:

Rolls-Royce Deutschland Ltd & Co KG (Type Certificate previously 
held by Rolls-Royce plc): Docket No. FAA-2021-0306; Project 
Identifier MCAI-2020-01493-E.

(a) Comments Due Date

    The FAA must receive comments on this airworthiness directive 
(AD) action by June 7, 2021.

(b) Affected ADs

    This AD replaces AD 2020-15-12, Amendment 39-21175 (85 FR 45081, 
July 27, 2020).

(c) Applicability

    This AD applies to Rolls-Royce Deutschland Ltd & Co KG (Type 
Certificate previously held by Rolls-Royce plc) Trent 1000-A2, Trent 
1000-AE2, Trent 1000-C2, Trent 1000-CE2, Trent 1000-D2, Trent 1000-
E2, Trent 1000-G2, Trent 1000-H2, Trent 1000-J2, Trent 1000-K2, and 
Trent 1000-L2 model turbofan engines, except those that have the 
redesigned intermediate-pressure compressor (IPC) stage 1 and stage 
2 rotor blades introduced by Rolls-Royce (RR) Service Bulletin (SB) 
Trent 1000 72-J941, Initial Issue, dated December 6, 2016, or 
Revision 1, dated February 6, 2019.

(d) Subject

    Joint Aircraft System Component (JASC) Code 7230, Turbine Engine 
Compressor Section.

(e) Unsafe Condition

    This AD was prompted by IPC rotor blade separations resulting in 
engine failures. The FAA is issuing this AD to prevent failure of 
the IPC. The unsafe condition, if not addressed, could result in 
failure of one or more engines, loss of thrust control, and loss of 
the airplane.

(f) Compliance

    Comply with this AD within the compliance times specified, 
unless already done.

[[Page 21237]]

(g) Required Actions

    (1) After the effective date of this AD, before exceeding the 
initial inspection thresholds and repeat inspection intervals 
specified in Table 1 of RR Alert Non-Modification Service Bulletin 
(NMSB) Trent 1000 72-AK313, Revision 1, dated August 22, 2019 (RR 
NMSB Trent 1000 72-AK313 R1):
    (i) Perform initial ultrasonic inspections (USIs) of the IPC 
stage 1 rotor blade root (front face).
    (ii) Thereafter, perform repetitive USIs of the IPC stage 1 
rotor blade root (front face).
    (iii) Use the Accomplishment Instructions, paragraph 3.A.(1)(a) 
(on-wing) or 3.A.(2)(a) and (b) (in-shop), of RR NMSB Trent 1000 72-
AK313 R1 to perform the inspections.
    (2) After the effective date of this AD, before exceeding the 
initial inspection thresholds and repeat inspection intervals 
specified in Table 2 of RR NMSB Trent 1000 72-AK313 R1:
    (i) Perform initial visual inspections of the IPC stage 2 rotor 
blade root (front face) and IPC shaft stage 2 dovetail post (front 
face).
    (ii) Thereafter, perform repetitive visual inspections of the 
IPC stage 2 rotor blade root (front face) and IPC shaft stage 2 
dovetail post (front face).
    (iii) Use the Accomplishment Instructions, paragraph 3.B.(1)(a) 
(on-wing) or 3.B.(2)(b) (in-shop), of RR NMSB Trent 1000 72-AK313 R1 
to perform the inspections.
    (3) After the effective date of this AD, before exceeding the 
initial inspection threshold and repeat inspection intervals 
specified in Table 2 of RR NMSB Trent 1000 72-AK313 R1:
    (i) Perform initial USIs of IPC stage 2 rotor blade root (rear 
face).
    (ii) Thereafter, perform repetitive USIs of IPC stage 2 rotor 
blade root (rear face).
    (iii) Use the Accomplishment Instructions, paragraph 3.C.(1)(a) 
(on-wing) or 3.C.(2)(a) (in-shop), of RR NMSB Trent 1000 72-AK313 R1 
to perform the inspections.
    (4) After the effective date of this AD, within 5 engine flight 
cycles (FCs) after each occurrence in which any engine operates in 
asymmetric power conditions at an altitude of less than 28,000 feet, 
perform the following inspections on the engine not affected by the 
power reduction or in-flight shutdown (IFSD):
    (i) Perform initial USIs and visual inspections required by 
paragraphs (g)(1) through (3) of this AD.
    (ii) Thereafter, perform the repetitive USIs and visual 
inspections required by paragraphs (g)(1) through (3) of this AD.
    (iii) Use the service information and repetitive inspection 
thresholds required by paragraphs (g)(1)(iii), (2)(iii), and 
(3)(iii) to perform the inspections, as applicable.
    (5) After the effective date of this AD, within 5 engine FCs 
following a cabin depressurization event, perform the following 
inspections on both engines installed on the airplane:
    (i) Perform initial USIs and visual inspections required by 
paragraphs (g)(1) through (3) of this AD.
    (ii) Thereafter, perform the repetitive USIs and visual 
inspections required by paragraphs (g)(1) through (3) of this AD.
    (iii) Use the service information and repetitive inspection 
thresholds required by paragraphs (g)(1)(iii), (2)(iii), and 
(3)(iii) to perform the inspections, as applicable.
    (6) If any IPC stage 1 rotor blade root (front face), IPC stage 
2 rotor blade root (front face), or IPC stage 2 rotor blade root 
(rear face) is found cracked during any inspection required by this 
AD, replace the part with a part eligible for installation before 
further flight.
    (7) If any IPC shaft stage 2 dovetail post (front face) is found 
cracked during any inspection required by this AD, replace the IPC 
drum assembly.

(h) Mandatory Terminating Action

    At the next engine shop visit after the effective date of this 
AD, replace the IPC stage 1 and stage 2 rotor blades with redesigned 
IPC stage 1 and stage 2 rotor blades introduced by RR SB Trent 1000 
72-J941, Revision 1, dated February 6, 2019. Install the blades as 
kitted sets using the Accomplishment Instructions, paragraph 3.C. 
(In-Shop), of RR Alert SB Trent 1000 72-AK430, Initial Issue, dated 
August 17, 2020. This replacement of the IPC stage 1 and stage 2 
rotor blades as kitted sets is a terminating action for the initial 
and repetitive ultrasonic or visual inspection requirements, as 
applicable, required by paragraphs (g)(1) through (5) of this AD.

(i) Definitions

    (1) For the purpose of this AD, an ``asymmetric power 
condition'' is the operation of the airplane at an altitude of less 
than 28,000 feet, experiencing either single engine take-off, engine 
fault (reduced power on one engine), or single engine IFSD, which 
includes execution of any non-normal checklist procedure.
    (2) For the purpose of this AD, an ``engine shop visit'' is the 
induction of an engine into the shop for maintenance involving the 
separation of pairs of major mating engine case flanges, except that 
the separation of engine flanges solely for the purposes of 
transportation without subsequent engine maintenance does not 
constitute an engine shop visit.

(j) Credit for Previous Actions

    You may take credit for the initial inspections required by 
paragraphs (g)(1) through (5) of this AD if you performed these 
inspections before the effective date of this AD using any of the 
following.
    (1) RR Alert NMSB Trent 1000 72-AJ819, Revision 3, dated April 
13, 2018, or earlier revisions;
    (2) RR Alert NMSB Trent 1000 72-AJ814, Revision 4, dated 
September 28, 2018, or earlier revisions;
    (3) RR Alert NMSB Trent 1000 72-AK313, Initial Issue, dated May 
2, 2019; or
    (4) RR Alert NMSB Trent 1000 72-AK092, Revision 3, dated 
February 28, 2019, or earlier revisions.

(k) Special Flight Permit

    Special flight permits, as described in Section 21.197 and 
Section 21.199 of the Federal Aviation Regulations (14 CFR 21.197 
and 21.199), are subject to the requirements of paragraph (k)(1) of 
this AD.
    (1) Operators who are prohibited from further flight due to a 
crack finding as a result of paragraph (g) of this AD, may perform a 
one-time non-revenue ferry flight to a location where the engine can 
be removed from service. This ferry flight must be performed without 
passengers, involve non-ETOPS operation, and consume no more than 
three FCs.
    (2) [Reserved]

(l) Alternative Methods of Compliance (AMOCs)

    (1) The Manager, ECO Branch, FAA, has the authority to approve 
AMOCs for this AD, if requested using the procedures found in 14 CFR 
39.19. In accordance with 14 CFR 39.19, send your request to your 
principal inspector or local Flight Standards District Office, as 
appropriate. If sending information directly to the manager of the 
certification office, send it to the attention of the person 
identified in Related Information. You may email your request to: 
[email protected].
    (2) Before using any approved AMOC, notify your appropriate 
principal inspector, or lacking a principal inspector, the manager 
of the local flight standards district office/certificate holding 
district office.

(m) Related Information

    (1) For more information about this AD, contact Kevin Clark, 
Aviation Safety Engineer, ECO Branch, FAA, 1200 District Avenue, 
Burlington, MA 01803; phone: (781) 238-7088; fax: (781) 238-7199; 
email: [email protected].
    (2) Refer to European Union Aviation Safety Agency (EASA) AD 
2020-0240, dated November 5, 2020, for more information. You may 
examine the EASA AD in the AD docket at https://www.regulations.gov 
by searching for and locating it in Docket No. FAA-2021-0306.
    (3) For service information identified in this AD, contact 
Rolls-Royce plc, Corporate Communications, P.O. Box 31, Derby, DE24 
8BJ, United Kingdom; phone: +44 (0)1332 242424; fax: +44 (0)1332 
249936; email: https://www.rolls-royce.com/contact-us/civil-aerospace.aspx; website: https://www.rolls-royce.com/contact-us.aspx. You may view this referenced service information at the 
FAA, Airworthiness Products Section, Operational Safety Branch, 1200 
District Avenue, Burlington, MA 01803. For information on the 
availability of this material at the FAA, call (781) 238-7759.

    Issued on April 9, 2021.
Lance T. Gant,
Director, Compliance & Airworthiness Division, Aircraft Certification 
Service.
[FR Doc. 2021-07660 Filed 4-21-21; 8:45 am]
BILLING CODE 4910-13-P