2023-14471. Airworthiness Directives; General Electric Company Engines

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Supplemental notice of proposed rulemaking (SNPRM).

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: [phone].

• 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: [phone]; email: [e-mail]; 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: [phone]; email: [e-mail].

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

Action	Labor cost	Parts cost	Cost per product	Cost on U.S. operators
Visually inspect, FPI, and USI the main propeller shaft	2 work-hours × $85 per hour = $170	$0	$170	$29,920

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

Action	Labor cost	Parts cost	Cost per product
Replace the main propeller shaft	8 work-hours × $85 per hour = $680	$48,360	$49,040
Revise the ALS of the MM	1 work-hour × $85 per hour = $85	0	85

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.

§ 39.13

[Amended]

2. The FAA amends § 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:

General Electric Company: Docket No. FAA–2022–1314; Project Identifier AD–2021–00811–E.

(a) Comments Due Date

The FAA must receive comments on this airworthiness directive (AD) by August 25, 2023.

(b) Affected ADs

This AD replaces AD 2018–03–13, Amendment 39–19186 (83 FR 6125, February 13, 2018).

(c) Applicability

This AD applies 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.

(d) Subject

Joint Aircraft System Component (JASC) Code 7210, Turbine Engine Reduction Gear.

(e) Unsafe Condition

This AD was prompted by an in-flight failure of a main propeller shaft on a GE CT7–9B model engine, resulting in the loss of the propeller. The FAA is issuing this AD to prevent failure of the main propeller shaft. The unsafe condition, if not addressed, could cause in-flight loss of the propeller, loss of engine thrust control, and damage to the airplane.

(f) Compliance

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

(g) Required Actions

(1) For affected CT7–5A2, CT7–5A3, CT7–9B, CT7–9B1, and CT7–9B2 model engines, using the compliance times specified in Figure 1 to paragraph (g)(1) of this AD, perform initial and repetitive visual inspections, fluorescent penetrant inspections (FPIs), and ultrasonic inspections (USIs) of the main propeller shaft.

Figure 1 to Paragraph (g)(1)—Compliance Times for CT7–5A2, CT7–5A3, CT7–9B, CT7–9B1, and CT7–9B2 Model Engines

(2) For affected CT7–7A, CT7–7A1, CT7–9C, and CT7–9C3 model engines, using the compliance times specified in Figure 2 to paragraph (g)(2) of this AD, perform initial and repetitive visual inspections, FPIs, and USIs of the main propeller shaft.

Figure 2 to Paragraph (g)(2)—Compliance Times for CT7–7A, CT7–7A1, CT7–9C, and CT7–9C3 Model Engines

(3) Perform the visual inspections, FPIs, and USIs required by paragraphs (g)(1) and (2) of this AD as follows:

(i) Prior to performance of the inspections, clean the main propeller shaft flange using the Accomplishment Instructions, paragraph 3.B., of GE Service Bulletin (SB) CT7–TP 72–0541 R01, dated November 18, 2021 (GE SB CT7–TP 72–0541).

(ii) Visually inspect the main propeller shaft for wear, corrosion, and cracking using the Accomplishment Instructions, paragraph 3.C.(1), of GE SB CT7–TP 72–0541.

(iii) Spot-FPI the area on the main propeller shaft flange face using the Accomplishment Instructions, paragraph 3.C.(2)(a), of GE SB CT7–TP 72–0541.

(iv) USI the two dowel pin holes of the main propeller shaft using the Accomplishment Instructions, paragraph 3.C.(3)(a), of GE SB CT7–TP 72–0541.

(4) If a crack or rejectable indication is found during the initial and repetitive visual inspections, FPIs, or USIs required by paragraphs (g)(1) through (3) of this AD, before further flight, remove the main propeller shaft from service and replace it with a part eligible for installation.

(5) For all affected engines, if the main propeller shaft CSN is unknown, use the propeller gearbox (PGB) CSN. If the PGB CSN is unknown, assume the inspection threshold is exceeded.

(h) Optional Terminating Action

Accomplishing the actions in paragraphs (h)(1) through (4) of this AD, as applicable by engine model, constitutes terminating action for the inspections required by paragraphs (g)(1) through (3) of this AD.

(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 information in Figure 3 to paragraph (h)(1) of this AD.

(2) For affected CT7–9B, CT7–9B1, CT7–9B2, CT7–9C, and CT7–9C3 model engines, revise the ALS of the existing MM and the operator's existing approved maintenance program or inspection program, as applicable, by incorporating the information in Figure 4 to paragraph (h)(2) of this AD.

(3) Thereafter, except as provided in paragraph (k) of this AD, no alternative inspection times or intervals may be approved for this main propeller shaft.

(4) The optional terminating actions in paragraphs (h)(1) and (2) of this AD may be performed by the owner/operator (pilot) holding at least a private pilot certificate and must be entered into the aircraft records showing compliance with this AD 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.

(i) Definition

For the purpose of this AD, a “part eligible for installation” is a main propeller shaft that has been inspected in accordance with paragraphs (g)(1) or (2), and (3) of this AD, and there was no crack or rejectable indication.

(j) Credit for Previous Actions

You may take credit for the initial visual inspection, FPI, and USI required by paragraphs (g)(1) through (3) of this AD if you performed these initial inspections before the effective date of this AD in accordance with GE SB CT7–TP 72–0541 R00, dated September 9, 2021.

(k) Alternative Methods of Compliance (AMOCs)

(1) The Manager, AIR–520 Continued Operational Safety 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 (l) of this AD and email it to: [e-mail].

(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.

(l) Related Information

For more information about this AD, contact Sungmo Cho, Aviation Safety Engineer, FAA, 2200 South 216th Street, Des Moines, WA 98198; phone: [phone]; email: [e-mail].

(m) Material Incorporated by Reference

(1) The Director of the Federal Register approved the incorporation by reference (IBR) of the service information listed in this paragraph under 5 U.S.C. 552(a) and 1 CFR part 51.

(2) You must use this service information as applicable to do the actions required by this AD, unless the AD specifies otherwise.

(i) GE Service Bulletin CT7–TP 72–0541 R01, dated November 18, 2021.

(ii) [Reserved]

(3) For GE service information identified in this AD, contact General Electric Company, 1 Neumann Way, Cincinnati, OH 45215; phone: [phone]; email:

[e-mail]; website: ge.com.

(4) You may view this service information at 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.

(5) You may view this service information that is incorporated by reference at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, email: [e-mail], or go to: www.archives.gov/​federal-register/​cfr/​ibr-locations.html.

Issued on July 3, 2023.

Michael Linegang,

Acting Director, Compliance & Airworthiness Division, Aircraft Certification Service.