SUPPLEMENTARY INFORMATION:

Comments Invited

The FAA invites you to send any written relevant data, views, or arguments about this proposal. Send your comments using a method listed under the ADDRESSES section. Include “Docket No. FAA-2026-11811; Project Identifier AD-2026-00667-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 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 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 Molly Sturgis, 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 AD 2026-09-02, Amendment 39-23322 (91 FR 30191, May 22, 2026) (AD 2026-09-02), for PW Model PW4074, PW4074D, PW4077, PW4077D, PW4084D, PW4090, and PW4090-3 engines. AD 2026-09-02 was prompted by an analysis of an event involving an International Aero Engines, LLC (IAE LLC) Model PW1127GA-JM engine, which experienced an HPC 7th-stage integrally bladed rotor (IBR-7) separation that resulted in an aborted takeoff. Following this event, the manufacturer analysis found that the failure of the HPC IBR-7 was caused by a nickel powdered metal anomaly, ( printed page 66013) similar in nature to an anomaly previously observed. The analysis also concluded that there is an increased risk of failure for additional nickel powdered metal parts in certain nickel powdered metal production campaigns, and these parts are susceptible to failure much earlier than previously determined. AD 2026-09-02 requires repetitive AUSIs of the HPC 15th-stage disks, front turbine hubs, HPT 1st-stage air seals, and HPT 2nd-stage hubs for crack indications, and removal from service and replacement if necessary, and for certain serial numbers, removal from service and replacement of the HPT 1st-stage air seal. The FAA issued AD 2026-09-02 to prevent failure of the HPC 15th-stage disk, front turbine hub, HPT 1st-stage air seal, and HPT 2nd-stage hub. The unsafe condition, if not addressed, could result in uncontained disk failure, release of high energy debris, damage to the engine, damage to the airplane, and possible loss of the airplane.

Actions Since AD 2026-09-02 Was Issued

Since the FAA issued AD 2026-09-02, the FAA has become aware that the manufacturer revised PW Alert Service Bulletin (ASB) PW4G-112-A72-368, dated June 20, 2024 (PW ASB PW4G-112-A72-368) to include HPT 2nd-stage hub part number (P/N) 53L402, which was not identified in PW ASB PW4G-112-A72-368 and inadvertently omitted from AD 2026-09-02. Additionally, the applicability of the optional terminating action was matched to paragraph (g)(1) of AD 2026-09-02, which is an unrelated requirement.

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.

Material Incorporated by Reference Under 1 CFR Part 51

The FAA reviewed PW ASB PW4G-112-A72-368, Revision No. 1, dated September 20, 2024, which specifies procedures for performing repetitive AUSIs on affected HPT 2nd-stage hubs.

This proposed AD would also require the following material, which the Director of the Federal Register approved for incorporation by reference as of June 26, 2026 (91 FR 30191, May 22, 2026).

• PW ASB PW4G-112-A72-365, Revision No. 1, dated June 20, 2024, which specifies procedures for performing repetitive AUSIs on affected HPC 15th-stage disks.
• PW ASB PW4G-112-A72-366, dated June 20, 2024, which specifies procedures for performing repetitive AUSIs on affected HPT 1st-stage air seals.
• PW ASB PW4G-112-A72-367, dated June 20, 2024, which specifies procedures for performing repetitive AUSIs on affected front turbine hubs.

This material is reasonably available because the interested parties have access to it through their normal course of business or by the means identified in the ADDRESSES section.

Proposed AD Requirements in This NPRM

This proposed AD would require repetitive AUSIs of the HPC 15th-stage disks, front turbine hubs, HPT 1st-stage air seals, and HPT 2nd-stage hubs for crack indications, and removal from service and replacement if necessary. This proposed AD would also require, for certain serial numbers, removal from service and replacement of the HPT 1st-stage air seal.

Costs of Compliance

The FAA estimates that this AD, if adopted as proposed, would affect 124 engines installed on airplanes of U.S. registry. The FAA estimates that 124 engines will need AUSIs of the HPC 15th-stage disk, front turbine hub, HPT 2nd-stage hub, and HPT 1st-stage air seal; and 6 engines will need replacement of the HPT 1st-stage air seals.

The FAA estimates the following costs to comply with this proposed AD:

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 engines that might need these replacements:

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 ( printed page 66014) 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 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.

The Proposed Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA proposes to amend 14 CFR part 39 as follows:

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

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

2. The FAA amends § 39.13 by:

a. Removing Airworthiness Directive 2026-09-02, Amendment 39-23322 ( 91 FR 30191, May 22, 2026); and

b. Adding the following new airworthiness directive:

Pratt & Whitney RTX Corporation (Type Certificate Previously Held by Pratt & Whitney Division United Technologies Corporation): Docket No. FAA-2026-11811; Project Identifier AD-2026-00667-E.

(a) Comments Due Date

The FAA must receive comments on this airworthiness directive (AD) by December 3, 2026.

(b) Affected ADs

This AD replaces AD 2026-09-02, Amendment 39-23322 (91 FR 30191, May 22, 2026) (AD 2026-09-02).

(c) Applicability

This AD applies to all Pratt & Whitney RTX Corporation (PW) Model PW4074, PW4074D, PW4077, PW4077D, PW4084D, PW4090, and PW4090-3 engines.

(d) Subject

Joint Aircraft System Component (JASC) Code 7250, Turbine Section; 7230, Turbine Engine Compressor Section.

(e) Unsafe Condition

This AD was prompted by an analysis of an event involving an International Aero Engines, LLC Model PW1127GA-JM engine, which experienced a high-pressure compressor (HPC) 7th-stage integrally bladed rotor separation that resulted in an aborted takeoff. The FAA is issuing this AD to prevent failure of the HPC 15th-stage disk, front turbine hub, high-pressure turbine (HPT) 1st-stage air seal, and HPT 2nd-stage hub. The unsafe condition, if not addressed, could result in uncontained disk failure, release of high energy debris, damage to the engine, damage to the airplane, and possible loss of the airplane.

(f) Compliance

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

(g) Required Actions

(1) For HPT 1st-stage air seals with a serial number identified in table 1 to paragraph (g)(1) of this AD: At the next piece part opportunity after the effective date of this AD, remove the HPT 1st-stage air seal from service and replace with a part eligible for installation.

(2) At the next piece part opportunity after the effective date of this AD and thereafter at every piece part opportunity, perform angle ultrasonic scan inspections (AUSIs) of the HPC 15th-stage disk, front turbine hub, HPT 1st-stage air seal, and HPT 2nd-stage hub for crack indications in accordance with the applicable service material specified in paragraph (g)(2)(i) through (iv) of this AD.

(i) For HPC 15th-stage disks: Accomplishment Instructions, paragraph 4.A or 4.B., of PW Alert Service Bulletin (ASB) PW4G-112-A72-365, Revision No. 1, dated June 20, 2024.

(ii) For front turbine hubs: Accomplishment Instructions, paragraph 4.A or 4.B., of PW ASB PW4G-112-A72-367, dated June 20, 2024.

(iii) For HPT 1st-stage air seals: Accomplishment Instructions, paragraph 4.A or 4.B., of PW ASB PW4G-112-A72-366, dated June 20, 2024.

(iv) For HPT 2nd-stage hubs: Accomplishment Instructions, paragraph 4.A or 4.B., of PW ASB PW4G-112-A72-368, Revision No. 1, dated September 20, 2024.

(3) If during any inspection required by paragraph (g)(2) of this AD, any crack indication is found, before further flight, remove the part from service and replace with a part eligible for installation.

(h) Definitions

For the purpose of this AD:

(1) A “piece part opportunity” is one of the conditions specified in paragraph (h)(1)(i) through (iv).

(i) The HPC 15th-stage disk is removed from the engine and all blades are removed.

(ii) The front turbine hub is removed from the engine and all blades are removed.

(iii) The HPT 2nd-stage hub is removed from the engine and all blades are removed.

(iv) The HPT 1st-stage air seal is fully disassembled from the engine.

(2) A “part eligible for installation” is:

(i) An HPC 15th-stage disk having P/N 51S115, 51S315, 55H615, or 56H015 that has passed the angle ultrasonic scan inspection (AUSI) required by paragraph (g)(2)(i) of this AD.

(ii) An HPC 15th-stage disk having P/N 51S115 or 56H015 that has a certificate of conformance that shows compliance with Non-Destructive Inspection Procedure (NDIP)-1276.

(iii) An HPC 15th-stage disk having P/N 51S315 or 55H615 that has a certificate of conformance that shows compliance with NDIP-1289.

(iv) A front turbine hub having P/N 55L801 or 55L901 that has passed the AUSI required by paragraph (g)(2)(ii) of this AD.

(v) A front turbine hub having P/N 55L801 that has a certificate of conformance that shows compliance with NDIP-1273.

(vi) A front turbine hub having P/N 55L901 that has a certificate of conformance that shows compliance with NDIP-1288.

(vii) An HPT 1st-stage air seal having P/N 50L663 or 50L959 that has passed the AUSI required by paragraph (g)(2)(iii) of this AD.

(viii) An HPT 1st-stage air seal having P/N 50L663 that has a certificate of conformance that shows compliance with NDIP-1286.

(ix) An HPT 1st-stage air seal having P/N 50L959 that has a certificate of conformance that shows compliance with NDIP-1287.

(x) An HPT 2nd-stage hub having P/N 53L202, 53L402, or 54L802 that has passed the AUSI required by paragraph (g)(2)(iv) of this AD.

(xi) An HPT 2nd-stage hub having P/N 53L202 that has a certificate of conformance that shows compliance with NDIP-1274. ( printed page 66015)

(xii) An HPT 2nd-stage hub having P/N 53L402 or 54L802 that has a certificate of conformance that shows compliance with NDIP-1275.

(xiii) Any HPC 15th-stage disk, front turbine hub, HPT 1st-stage air seal, or HPT 2nd-stage hub that is new, zero-time, and that has an FAA Form 8130-3 from the original equipment manufacturer for new production dated July 1, 2025, or later.

(i) Optional Terminating Action—Airworthiness Limitations Section (ALS) Revision

Revising the ALS of the existing engine manual and the operator's existing approved maintenance program or inspection program, as applicable, by incorporating the information in figure 1 to paragraph (i) of this AD, constitutes terminating action for the actions required by paragraphs (g)(2) and (3) of this AD.

(j) 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 AIR-520 Continued Operational Safety Branch, send it to the attention of the person identified in paragraph (k) of this AD and email to: AMOC@faa.gov.

(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.

(k) Additional Information

For more information about this AD, contact Molly Sturgis, Aviation Safety Engineer, FAA, 2200 South 216th Street, Des Moines, WA 98198; phone: (562) 627-5373; email: molly.a.sturgis@faa.gov.

(l) Material Incorporated by Reference

(1) The Director of the Federal Register approved the incorporation by reference ( printed page 66016) (IBR) of the material listed in this paragraph under 5 U.S.C. 552(a) and 1 CFR part 51.

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

(3) The following material was approved for IBR on [DATE 35 DAYS AFTER PUBLICATION OF THE FINAL RULE].

(i) Pratt & Whitney RTX Corporation (PW) Alert Service Bulletin (ASB) PW4G-112-A72-368, Revision No. 1, dated September 20, 2024.

(ii) [Reserved]

(4) The following material was approved for IBR on June 26, 2026 (91 FR 30191, May 22, 2026).

(i) PW ASB PW4G-112-A72-365, Revision No. 1, dated June 20, 2024.

(ii) PW ASB PW4G-112-A72-366, dated June 20, 2024.

(iii) PW ASB PW4G-112-A72-367, dated June 20, 2024.

(5) For PW material identified in this AD, contact PW, 400 Main Street, East Hartford, CT 06118; phone: (800) 565-0140; email: help24@prattwhitney.com; website: connect.prattwhitney.com.

(6) You may view this material 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.

(7) You may view this material at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, visit www.archives.gov/​federal-register/​cfr/​ibr-locations or email fr.inspection@nara.gov.

91 FR 66012