DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2022-1314; Project Identifier AD-2021-00811-E]
RIN 2120-AA64

Airworthiness Directives; General Electric Company Engines

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Supplemental notice of proposed rulemaking (SNPRM).

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SUMMARY: The FAA is revising a notice of proposed rulemaking (NPRM)
that applied to General Electric Company (GE) Model CT7-5A2, CT7-5A3,
CT7-7A, CT7-7A1, CT7-9B, CT7-9B1, CT7-9B2, CT7-9C, and CT7-9C3 engines.
The NPRM proposed to supersede Airworthiness Directive (AD) 2018-03-13.
This action revises the NPRM by regrouping certain engine models within
the figures in the Required Actions paragraph. The FAA is proposing
this airworthiness directive to address the unsafe condition on these
products. Since these actions expand the applicability for the required
actions as proposed in the NPRM, the agency is requesting comments on
this SNPRM.

DATES: The FAA must receive comments on this SNPRM by August 25, 2023.

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 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.
AD Docket: You may examine the AD docket at regulations.gov by
searching for and locating Docket No. FAA-2022-1314; or in person at
Docket Operations between 9 a.m. and 5 p.m., Monday through Friday,
except Federal holidays. The AD docket contains the NPRM, this SNPRM,
any comments received, and other information. The street address for
Docket Operations is listed above.
Material Incorporated by Reference:
For GE service information identified in this SNPRM,
contact General Electric Company, 1 Neumann Way, Cincinnati, OH 45215;
phone: (513) 552-3272; email: aviation.fleetsupport@ae.ge.com; website:
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 (817) 222-5110.

FOR FURTHER INFORMATION CONTACT: Sungmo Cho, Aviation Safety Engineer,
FAA, 2200 South 216th Street, Des Moines, WA 98198; phone: (781) 238-
7241; email: Sungmo.D.Cho@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 the ADDRESSES section. Include ``Docket No. FAA-2022-1314;
Project Identifier AD-2021-00811-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 again revise 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
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 SNPRM 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 SNPRM, 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 SNPRM. Submissions containing CBI should
be sent to Sungmo Cho, Aviation Safety Engineer, FAA, 2200 South 216th
Street, Des Moines, WA 98198. 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 an NPRM to amend 14 CFR part 39 by adding an AD that
would apply to GE Model CT7-5A2, CT7-5A3, CT7-7A, CT7-7A1, CT7-9B, CT7-
9B1, CT7-9B2, CT7-9C, and CT7-9C3 engines. The NPRM published in the
Federal Register on November 1, 2022 (87 FR 65694) and proposed to
supersede AD 2018-03-13, Amendment 39-19186 (83 FR 6125, February 13,
2018) (AD 2018-03-13), for certain GE Model CT7-5A2, CT7-5A3, CT7-7A,
CT7-7A1, CT7-9B, CT7-9B1, CT7-9B2, CT7-9C, and CT7-9C3 engines with
main propeller shaft, part number 77581-11, installed. AD 2018-03-13
published with part number 77581-11, which was a typographical error.
The correct part number is 775801-11, however, reference to that part
number is no longer necessary for this SNPRM and is not included in the
applicability. AD 2018-03-13 was prompted by an in-flight failure of a
main propeller shaft on a GE Model CT7-9B engine, resulting in the loss
of the propeller. A manufacturer investigation determined the failure
of the main propeller shaft was caused by cracks initiating from
undiscovered corrosion in the dowel pin holes on the flange of the main
propeller shaft. After the FAA issued AD 2018-03-13, the manufacturer
detected two additional cracks on a main propeller shaft during its
ongoing investigation and subsequently published service information
that introduced reduced inspection thresholds for initial and
repetitive visual inspections, fluorescent penetrant inspections
(FPIs), and added initial and repetitive ultrasonic inspections (USIs)
of the main propeller shaft. Additionally, the manufacturer revised the
airworthiness limitations section (ALS) of the maintenance manual (MM)
to incorporate initial and repetitive USIs to inspect for cracks on the
main propeller shaft. As a result, the FAA proposed to supersede AD
2018-03-13 by issuing the NPRM. In the NPRM, the FAA proposed to
require initial and repetitive visual inspections, FPIs, and USIs of
the main propeller shaft. Depending on the results of these
inspections, the NPRM proposed to require replacement of the main
propeller shaft. As an optional terminating action to these
inspections, the NPRM proposed to require revising the ALS of the
existing MM and the operator's existing approved maintenance program or
inspection program, as applicable, to incorporate the tasks and reduced
inspection thresholds for the main propeller shaft.

Actions Since the NPRM Was Issued

Since the FAA issued the NPRM, GE Aerospace commented on the NPRM,
stating that certain engine models were included in incorrect Figures
within the Required Actions paragraph of the NPRM, which would
attribute inaccurate inspection thresholds to those engine models.
Therefore, the FAA has revised Figures 1 and 2 in this SNPRM to include
the correct engine models. The FAA has also updated the affected engine
models listed in paragraphs (g)(1) and (g)(2) of this SNPRM to
correspond with the corrected engine models referenced in Figures 1 and
2.

Comments

The FAA received comments from GE Aerospace and two anonymous
commenters. GE Aerospace requested changes to the NPRM. The two
anonymous commenters supported the NPRM without change. The following
presents the comments received on the NPRM and the FAA's response to
each comment.

Request To Regroup Engines in Figure 1 to Paragraph (g)(1)

GE Aerospace requested that the FAA revise Figure 1 to Paragraph
(g)(1) of the NPRM to align with GE Service Bulletin (SB) CT7-TP 72-
0541 R01, dated November 18, 2021 (GE SB CT7-TP 72-0541). GE noted that
Figure 1 to Paragraph (g)(1) incorrectly grouped together CT7-5 engine
models with CT7-7 engine models. GE also noted that CT7-5 engine models
should be grouped with CT7-9B engine models, as specified GE SB CT7-TP
72-0541, which groups engine models according to aircraft type.
The FAA agrees and has revised paragraph (g)(1) and Figure 1 to
Paragraph (g)(1) of this SNPRM by removing CT7-7A and CT7-7A1 model
engines and adding CT7-9B, CT7-9B1, and CT7-9B2 model engines.

Request To Regroup Engines in Figure 2 to Paragraph (g)(2)

GE Aerospace requested that the FAA revise Figure 2 to Paragraph
(g)(2) of the NPRM to align with GE SB CT7-TP 72-0541. GE noted that
Figure 2 to Paragraph (g)(2) incorrectly grouped together CT7-9B engine
models with CT7-9C engine models. GE also noted that CT7-7 engine
models should be grouped with CT7-9C engine models, as specified in GE
SB CT7-TP 72-0541, which groups engine models according to aircraft
type.
The FAA agrees and has revised paragraph (g)(2) and Figure 2 to
Paragraph (g)(2) of this SNPRM by removing CT7-9B, CT7-9B1, and CT7-9B2
model engines and adding CT7-7A and CT7-7A1 model engines.

Request To Clarify GE Service Bulletin (SB) Citation

GE Aerospace noted that the SB revision number for GE SB CT7-TP 72-
0541 R01, dated November 18, 2021, is listed in paragraph (g)(3)(i) of
the NPRM, but is not included in the SB citation in paragraph
(g)(3)(ii) and (iii) of the NPRM. GE requested that the FAA revise the
SB citation in paragraphs (g)(3)(i), (ii), and (iii) to: ``GE SB CT7-TP
72-0541 latest revision'' because guiding operators to latest version
of SB revisions could be efficient, accessible, or beneficial.
The FAA acknowledges that the revision number for GE SB CT7-TP 72-
0541 R01, dated November 18, 2021, is not listed in paragraph
(g)(1)(ii) and (iii) of the NPRM. However, the FAA notes that the
shorthand for this SB is in paragraph (g)(1)(i) as ``GE SB CT7-TP 72-
0541.'' The FAA notes that this shorthand indicates the text in
parenthesis to be equivalent to the full citation of the SB for the
subsequent paragraphs. The FAA disagrees with adding ``latest
revision'' when referencing the service information in paragraph (g) of
this SNPRM. Future revisions of the service information have not yet
been published by the manufacturer or reviewed by the FAA. A request
for an alternative method of compliance can be submitted to the FAA if
future revisions of the service information referenced in paragraph (g)
of this SNPRM are published. Additionally, if future revisions of the
service information are published by the manufacturer and approved by
the FAA, the FAA may consider further rulemaking. The FAA did not
change this proposed AD as a result of this comment.

Request To Remove Figure 3 to Paragraph (h)(1)

GE Aerospace commented that the visual inspection detailed in
Figure 3 to Paragraph (h)(1) of the NPRM was not included in the ALS of
the MM when the NPRM was published, but has since been added to the
ALS. GE stated that Figure 3 to Paragraph (h)(1) of this AD may be
eliminated, and language in paragraph (h)(1) revised to: ``(1) For
affected CT7-5A2, CT7-5A3, CT7-7A, and CT7-7A1 model engines, revise
the airworthiness limitations section (ALS) of the existing maintenance
manual (MM) and the operator's existing approved maintenance program or
inspection program, as applicable, by incorporating the manufacturer's
latest ALS of the existing MM.''
The FAA disagrees with removing Figure 3 to paragraph (h)(1) of
this SNPRM AD because it clarifies the specific tasks operators must
complete in order to comply with the SNPRM. The FAA also disagrees with
changing the language in paragraph (h)(1) to require incorporating the
manufacturer's latest ALS of the existing MM. The FAA notes that
although the ALS has been revised to include the visual inspection task
from Figure 3 to paragraph (h)(1) of this SNPRM, the ALS also presents
instructions that are not necessary for operators to complete in order
to comply with this proposed AD. The FAA did not change this proposed
AD as a result of this comment.

Request To Remove Figure 4 to Paragraph (h)(2)

GE Aerospace commented that the visual inspection detailed in
Figure 4 to Paragraph (h)(2) of the NPRM AD was not included in the ALS
when the NPRM was published, and has since been added to the ALS. GE
stated that Figure 4 to Paragraph (h)(2) of this NPRM may be
eliminated, and language in paragraph (h)(2) revised to: ``(1) For
affected CT7-5A2, CT7-5A3, CT7-7A, and CT7-7A1 model engines, revise
the `airworthiness limitations section (ALS) of the existing
maintenance manual (MM) and the operator's existing approved
maintenance program or inspection program, as applicable, by
incorporating the manufacturer's latest ALS of the existing MM.''
The FAA disagrees with removing Figure 4 to paragraph (h)(2) of
this SNPRM because it clarifies the specific tasks operators must
complete in order to comply with the proposed AD. The FAA also
disagrees with changing the language in paragraph (h)(2) to require
incorporating the manufacturer's latest ALS of the existing MM. The FAA
notes that although the ALS has been updated to include the visual
inspection task from Figure 4 to paragraph (h)(2) of this AD, the ALS
also presents superfluous instructions that are not necessary for
operators to complete in order to comply with this proposed AD. The FAA
did not change this proposed AD as a result of this comment.

FAA's Determination

The FAA is proposing this AD after determining the unsafe condition
described previously is likely to exist or develop in other products of
the same type design. Certain changes described above expand the scope
of the NPRM. As a result, it is necessary to reopen the comment period
to provide additional opportunity for the public to comment on this
SNPRM.

Related Service Information Under 1 CFR Part 51

The FAA reviewed GE Service Bulletin (SB) CT7-TP 72-0541 R01, dated
November 18, 2021 (GE SB CT7-TP 72-0541). This service information
specifies procedures for performing initial and repetitive visual
inspections, FPIs, and USIs of the main propeller shaft. 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.

Proposed AD Requirements in This SNPRM

This proposed AD would require initial and repetitive visual
inspections, FPIs, and USIs of the main propeller shaft. Depending on
the results of these inspections, this proposed AD would require
replacement of the main propeller shaft. As an optional terminating
action to these inspections, this proposed AD would require revising
the ALS of the existing MM and the operator's existing approved
maintenance program or inspection program, as applicable, to
incorporate the tasks and reduced inspection thresholds for the main
propeller shaft. An owner/operator (pilot) holding at least at least a
private pilot certificate may revise the ALS of the existing MM, and
the owner/operator must enter compliance with the applicable paragraphs
of the AD into the aircraft records in accordance with 14 CFR 43.9(a)
and 91.417(a)(2)(v). The record must be maintained as required by 14
CFR 91.417, 121.380, or 135.439. This is an exception to the FAA's
standard maintenance regulations.

Differences Between This SNPRM and the Service Information

GE SB CT7-TP 72-0541 uses the term ``ultrasonic inspection (UTI),''
while this proposed AD uses the term ``ultrasonic inspection (USI).''

Costs of Compliance

The FAA estimates that this AD, if adopted as proposed, would
affect 176 engines installed on airplanes of U.S. registry.
The FAA estimates the following costs to comply with this proposed
AD:

Estimated Costs

The FAA estimates the following costs to perform the optional
terminating action or to do any necessary replacement that would be
required based on the results of the inspections. The agency has no way
of determining the number of operators that will perform the optional
terminating action or aircraft that might need this replacement:

On-Condition Costs

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) Will not affect intrastate aviation in Alaska, and
(3) Will 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:

a. Removing Airworthiness Directive 2018-03-13, Amendment 39-19186 (83
FR 6125, February 13, 2018); and

b. Adding the following new airworthiness directive: