# [Amended]
**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 Pratt & Whitney Division (PW) Model PW4074, PW4074D, PW4077, PW4077D, PW4084D, PW4090, and PW4090-3 engines. This proposed AD was prompted by an analysis of an event involving an International Aero Engines, LLC (IAE LLC) Model PW1127GA-JM engine, which experienced a high-pressure compressor (HPC) 7th-stage integrally bladed rotor (IBR-7) separation that resulted in an aborted takeoff. This proposed AD would require repetitive angle ultrasonic scan inspections (AUSIs) of the HPC 15th-stage disks, front turbine hubs, high pressure turbine (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 is proposing this AD to address the unsafe condition on these products.
**DATES:**
The FAA must receive comments on this proposed AD by July 21, 2025.
**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* under Docket No. FAA-2025-0923; 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.
*Material Incorporated by Reference:*
• For PW material identified in this proposed AD, contact PW, 400 Main Street, East Hartford, CT 06118; phone: (800) 565-0140; email: *[email protected];* website: *connect.prattwhitney.com.*
• 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.
**FOR FURTHER INFORMATION CONTACT:**
Molly Sturgis, Aviation Safety Engineer, FAA, 2200 South 216th Street, Des Moines, WA 98198; phone: (562) 627-5373; 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 the *ADDRESSES* section. Include “Docket No. FAA-2025-0923; Project Identifier AD-2024-00529-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**
On December 24, 2022, an Airbus Model A320neo airplane powered by IAE LLC Model PW1127GA-JM engines, experienced a failure of the HPC IBR-7 that resulted in an engine shutdown and aborted take-off. Following this event, the manufacturer conducted a records review of production and field-returned parts and re-evaluated their engineering analysis methodology. The new analysis found that the failure of the HPC IBR-7 was caused by a nickel powdered metal anomaly, 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. As a result, the FAA is proposing additional AUSIs for certain affected nickel powdered metal parts and removal from service of certain affected nickel powdered metal parts. Certain PW Model PW4074, PW4074D, PW4077, PW4077D, PW4084D, PW4090, and PW4090-3 engines are among the products affected by this condition. This 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.
**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 the following service information:
• PW Alert Service Bulletin (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.
• PW ASB PW4G-112-A72-368, dated June 20, 2024, which specifies procedures for performing repetitive AUSIs on affected HPT 2nd-stage 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:
| Action | Labor cost | Parts cost | Cost per | Cost on U.S. |
| --- | --- | --- | --- | --- |
| AUSI of HPC 15th-stage disk | 4 work-hours × $85 per hour = $340 | $0 | $340 | $42,160 |
| AUSI of front turbine hub | 5 work-hours × 85 per hour = 425 | 0 | 425 | 52,700 |
| AUSI of HPT 2nd-stage hub | 5 work-hours × 85 per hour = 425 | 0 | 425 | 52,700 |
| AUSI of HPT 1st-stage air seal | 5 work-hours × 85 per hour = 425 | 0 | 425 | 52,700 |
| Replace certain HPT 1st-stage air seals (6 engines) | 1 work-hours × 85 per hour = 85 | 763,000 | 763,085 | 4,578,510 |
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:
| Action | Labor cost | Parts cost | Cost per product |
| --- | --- | --- | --- |
| Replace HPC 15th-stage disk | 10 work-hours × $85 per hour = $850 | $312,000 | $312,850 |
| Replace front turbine hub | 10 work-hours × 85 per hour = 850 | 910,000 | 910,850 |
| Replace HPT 2nd-stage hub | 10 work-hours × 85 per hour = 850 | 816,000 | 816,850 |
| Replace HPT 1st-stage air seals | 10 work-hours × 85 per hour = 850 | 763,000 | 763,850 |
**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.
§ 39.13
2. The FAA amends § 39.13 by adding the following new airworthiness directive:
*Pratt & Whitney Division:* Docket No. FAA-2025-0923; Project Identifier AD-2024-00529-E.
**(a) Comments Due Date**
The FAA must receive comments on this airworthiness directive (AD) by July 21, 2025.
**(b) Affected ADs**
None.
**(c) Applicability**
This AD applies to Pratt & Whitney Division (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 engine shutdown and 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.
| Serial No. | Part No. |
| --- | --- |
| CKLBME2702 | 50L663 |
| CKLBME2703 | 50L663 |
| CKLBME2704 | 50L663 |
| CKLBME2705 | 50L663 |
| CKLBME2711 | 50L663 |
| CKLBMS8019 | 50L959 |
(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 information 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, dated June 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 purposes 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 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) 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 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.
(xii) An HPT 2nd-stage hub having P/N 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 has passed an AUSI at new part production.
**(i) 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 (j) of this AD. Information may be emailed 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.
**(j) 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: *[email protected].*
**(k) Material Incorporated by Reference**
(1) The Director of the Federal Register approved the incorporation by reference (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 the actions required by this AD, unless the AD specifies otherwise.
(i) Pratt & Whitney (PW) Alert Service Bulletin (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.
(iv) PW ASB PW4G-112-A72-368, dated June 20, 2024.
(3) For PW material identified in this AD, contact PW, 400 Main Street, East Hartford, CT 06118; phone: (800) 565-0140; email: *[email protected];* website: *connect.prattwhitney.com.*
(4) 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.
(5) 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 *[email protected].*
Issued on June 3, 2025.
Lona C. Saccomando,
Acting Deputy Director, Integrated Certificate Management Division, Aircraft Certification Service.