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PROPOSED AD GENERAL ELECTRIC COMPANY: Docket No. FAA-2021-0869; Project Identifier AD-2021-00176-E.
(a) COMMENTS DUE DATE

    The FAA must receive comments on this airworthiness directive (AD)  by
    November 22, 2021.

(b) AFFECTED ADS

    None.

(c) APPLICABILITY

    This AD applies to General Electric Company (GE) CF34-8C5, CF34-8C5B1,
    CF34-8E2, CF34-8E2A1, CF34-8E5, CF34-8E5A1, CF34-8E5A2, CF34-8E6,  and
    CF34-8E6A1  model  turbofan engines  with  an installed  high-pressure
    turbine (HPT) rotor stage 1 disk, part number (P/N) 4125T22P04, and  a
    serial number (S/N) listed in Figure 1 or Figure 2 to paragraph (c) of
    this AD.

    FIGURE 1 TO PARAGRAPH (C)  HPT ROTOR STAGE 1 DISK P/N 4125T22P04, IN-
                                STALLED ON CF34-8C5 AND CF34-8C5B1 ENGINES
    ______________________________________________________________________
                                HPT ROTOR STAGE 1 DISK S/N
    ______________________________________________________________________
                                       NCU1234C
                                       NCU0180C
                                       NCU0174C
                                       NCU0183C
                                       NCU6175C
                                       NCU6174C
                                       NCU7694C
                                       GATJ8T64
                                       NCU7065C
                                       NCU7068C
                                       NCU6173C
                                       NCU1232C
                                       NCU7698C
                                       GATJ8P5T
    ______________________________________________________________________

    FIGURE 2 TO PARAGRAPH (C)  HPT ROTOR STAGE 1 DISK P/N 4125T22P04, IN-
                                STALLED ON CF34-8E2, CF34-8E2A1, CF34-8E5,
                                CF34-8E5A1, CF34-8E5A2, CF34-8E6 AND CF34-
                                8E6A1 ENGINES                             
    ______________________________________________________________________
                                HPT ROTOR STAGE 1 DISK S/N
    ______________________________________________________________________
                                       GATJ8PJF
                                       GATJ8P5R
                                       NCU9014C
                                       NCU9654A
                                       GATJ903T
                                       NCU8314C
                                       GATJ8WK4
                                       NCU9785A
                                       NCU1233C
                                       NCU2151C
                                       NCU7070C
                                       NCU2920C
                                       NCU7692C
                                       NCU6171C
                                       GATJ8TCF
                                       GATJ8T63
                                       NCU8313C
    ______________________________________________________________________

(d) SUBJECT

    Joint Aircraft System Component (JASC) Code 7250, Turbine Section.

(e) UNSAFE CONDITION

    This  AD was  prompted  by  a report  of a  quality escape  during the
    manufacturing of an HPT rotor stage 1 disk. The FAA is issuing this AD
    to  prevent  failure  of  the  HPT  rotor  stage  1  disk.  The unsafe
    condition, if not addressed, could result in uncontained disk release,
    damage to the engine, and damage to the airplane.

(f) COMPLIANCE

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

(g) REQUIRED ACTIONS

    For all affected engines, at the next engine shop visit or before  the
    HPT rotor stage 1 disk  accumulates 7,600 cycles since new,  whichever
    occurs first after the effective date of this AD, remove the HPT rotor
    stage  1  disk from  service  and replace  with  a part  eligible  for
    installation.

(h) DEFINITIONS

    For the purpose of this AD:

(1) An "engine shop visit" is the induction of an engine into the shop for
    maintenance involving the separation  of pairs of major  mating engine
    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.

(2) A "part eligible for installation"  is  an HPT rotor stage 1 disk that
    is not listed in Figure 1 or  Figure 2 to paragraph (c) of this  AD or
    an HPT rotor stage 1 disk that has been repaired using an FAA-approved
    repair.

Note 1 to paragraph (h)(2):  Guidance for repairing the HPT  rotor stage 1
disk can be found in GE Repair Document RD # 150-1811-P1,  dated March 17,
2020.

(i) 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 paragraph
    (j)(1) of this AD. Information may be emailed to: ANE-AD-AMOC@faa.gov.

(2) Before using any approved AMOC,  notify your appropriate principal in-
    spector, or lacking  a principal inspector,  the manager of  the local
    flight standards district office/certificate holding district office.

(j) RELATED INFORMATION

(1) For more information about this AD,  contact Scott Stevenson, Aviation
    Safety Engineer, ECO Branch, FAA, 1200 District Avenue, Burlington, MA
    01803;  phone: (781) 238-7132;  fax: (781) 238-7759;  email: Scott.M.
    Stevenson@faa.gov.

(2) For service information identified in this AD contact General Electric
    Company, 1 Neumann Way,  Cincinnati, OH 45215; phone:  (513) 552-3272;
    email:  aviation.fleetsupport@ae.ge.com;  website: https://www.ge.com.
    You  may  view  this  referenced  service  information  at  the   FAA,
    Airworthiness Products Section,  1200 District Avenue,  Burlington, MA
    01803. For  information on  the availability  of this  material at the
    FAA, call (781) 238-7759.

Issued on September 30, 2021.  Lance T. Gant, Director,  Compliance & Air-
worthiness Division, Aircraft Certification Service.

DATES: The FAA must receive comments  on this proposed AD  by November 22,
2021.
PREAMBLE 

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2021-0869; Project Identifier AD-2021-00176-E]
RIN 2120-AA64

Airworthiness Directives; General Electric Company Turbofan
Engines

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

-----------------------------------------------------------------------

SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD)
for certain General Electric Company (GE) CF34-8C and CF34-8E model
turbofan engines. This proposed AD was prompted by a report of a
quality escape during the manufacturing of a high-pressure turbine
(HPT) rotor stage 1 disk. This proposed AD would require removing the
HPT rotor stage 1 disk from service and replacing the HPT rotor stage 1
disk with a part eligible for installation. The FAA is proposing this
AD to the unsafe condition on these products.

DATES: The FAA must receive comments on this proposed AD by November
22, 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 General
Electric Company, 1 Neumann Way, Cincinnati, OH 45215; phone: (513)
552-3272; email: aviation.fleetsupport@ae.ge.com; website: https://www.ge.com.
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-2021-0869; 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: Scott Stevenson, Aviation Safety
Engineer, ECO Branch, FAA, 1200 District Avenue, Burlington, MA 01803;
phone: (781) 238-7132; fax: (781) 238-7199; email:
Scott.M.Stevenson@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. FAA-2021-0869; Project Identifier
AD-2021-00176-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 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 Scott
Stevenson, 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 GE of a quality escape that occurred during
the manufacturing of an HPT rotor stage 1 disk. The quality escape
occurred at a supplier that began production in August 2019. On
November 25, 2019, the supplier discovered tool gouges at the forward
chamfer of the air holes in an HPT rotor stage 1 disk. These gouges can
reduce the life of the HPT rotor stage 1 disk. This condition, if not
addressed, could result in uncontained disk release, damage to the
engine, and damage to the airplane.

FAA's 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 GE CF34-8C Alert Service Bulletin (ASB) 72-A0344
R01 and GE CF34-8E ASB 72-A0228 R01, both dated December 19, 2019. The
ASBs describe procedures for removing the HPT rotor stage 1 disk. The
FAA also reviewed GE Repair Document RD #150-1811-P1, dated March 17,
2020. This document describes procedures for repairing the HPT rotor
stage 1 disk.

Proposed AD Requirements in This NPRM

This proposed AD would require removing a certain HPT rotor stage 1
disk from service and replacing the HPT rotor stage 1 disk with a part
eligible for installation.

Differences Between This Proposed AD and the Service Information

The ASBs instruct operators to perform a visual inspection of the
HPT rotor stage 1 disk and re-mark the HPT rotor stage 1 disk, while
this proposed AD would not mandate visual inspection or re-marking. The
ASBs also instruct operators to perform an inspection of the removed
HPT rotor stage 1 disk and send it to an authorized service center for
repair, while this proposed AD would require removal of the HPT rotor
stage 1 disk from service and replacement with a part eligible for
installation.

Costs of Compliance

The FAA estimates that this AD, if adopted as proposed, would
affect 23 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
Remove and replace HPT rotor stage 1 disk 812 work-hours x $85 per hour = $69,020
$258,100
$327,120
$7,523,760

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 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.

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

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]

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