2026-17-08: Turbine Engine Compressor Section

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 adding the following new airworthiness directive: 2026-17-08 Pratt & Whitney Division: Amendment 39-23451; Docket No. FAA-2026-2724; Project Identifier AD-2025-01606-E. (a) Effective Date This airworthiness directive (AD) is effective October 8, 2026. (b) Affected ADs None. (c) Applicability This AD applies to all Pratt & Whitney Division (PW) Model PW4074D, PW4077D, PW4084D, PW4090, and PW4090-3 engines. (d) Subject Joint Aircraft System Component (JASC) Code 7230, Turbine Engine Compressor Section. (e) Unsafe Condition This AD was prompted by the discovery of a quality escape involving incorrect shot peening on certain high-pressure compressor (HPC) drum rotor disk assemblies. The FAA is issuing this AD to prevent failure of the HPC drum rotor disk assembly. The unsafe condition, if not addressed, could result in uncontained debris 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) Definitions For the purpose of this AD, a "part eligible for installation" is: (1) Any HPC drum rotor disk assembly having a part number (P/N) and serial number (S/N) that is not identified in paragraph (h) of this AD. (2) Any HPC drum rotor disk assembly having a P/N and S/N identified in paragraph (h)(1) of this AD that has passed the inspection required by paragraph (h)(1) of this AD. (h) Required Actions (1) For HPC drum rotor disk assemblies having P/N 50S634, and S/N CENCD26931, CENCD29577, CENCD29597, CENCD41851, or CENCD43536, as applicable, before accumulating the total life cycles since new in Table 1 of the Accomplishment Instructions of PW Alert Service Bulletin (ASB) PW4G-112-A72-373, dated September 10, 2025 (PW ASB PW4G-112-A72-373), perform a visual inspection of the HPC drum rotor disk assembly in accordance with the Accomplishment Instructions, paragraph 1.B., of PW ASB PW4G-112-A72-373. (2) If, during the inspection required by paragraph (h)(1) of this AD, evidence of incorrect shot peening is discovered, before further flight, replace the HPC drum rotor disk assembly with a part eligible for installation. (3) For the HPC drum rotor disk assembly having P/N 50S634 and S/N CENCD30975, before accumulating 9,800 total life cycles since new, remove the HPC drum rotor disk assembly from service and replace with a part eligible for installation. (4) For the HPC drum rotor disk assembly having P/N 50S634 and S/N CENCD42978, before accumulating 11,000 total life cycles since new, remove the HPC drum rotor disk assembly from service and replace with a part eligible for installation. (i) Alternative Methods of Compliance (AMOCs) 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 and email to: AMOC@faa.gov. 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: molly.a.sturgis@faa.gov. (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 do the actions required by this AD, unless the AD specifies otherwise. (i) Pratt & Whitney Division (PW) Alert Service Bulletin PW4G-112-A72-373, dated September 10, 2025. (ii) [Reserved] (3) 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. (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 fr.inspection@nara.gov. Issued on August 20, 2026. Brian Knaup, Acting Deputy Director, Integrated Certificate Management Division, Aircraft Certification Service. [FR Doc. 2026-18019 Filed 9-2-26; 8:45 am]BILLING CODE 4910-13-P