2026-18752: Airworthiness Directives; CFM International, S.A. Engines

Federal Register, Volume 91 Issue 176 (Monday, September 14, 2026) [Federal Register Volume 91, Number 176 (Monday, September 14, 2026)] [Proposed Rules] [Pages 58042-58046] From the Federal Register Online via the Government Publishing Office [www.gpo.gov] [FR Doc No: 2026-18752] ----------------------------------------------------------------------- DEPARTMENT OF TRANSPORTATION Federal Aviation Administration 14 CFR Part 39 [Docket No. FAA-2026-8803; Project Identifier AD-2026-00385-E] RIN 2120-AA64 Airworthiness Directives; CFM International, S.A. Engines

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 CFM International, S.A. (CFM) Model CFM56-5B, CFM56-5C, and CFM56-7B engines with a certain high-pressure turbine (HPT) inner stationary seal installed. This proposed AD was prompted by multiple reports of honeycomb separation from the surface of HPT inner stationary seals. This proposed AD would require initial and repetitive borescope inspections (BSIs) of the rotating air HPT front seal for cracks and, depending on the results, replacement with a part eligible for installation. This proposed AD would also require removal and replacement of the affected HPT inner stationary seal. This proposed AD would also require inspection of the affected HPT inner stationary seal for honeycomb separation and, depending on the results of the inspection, removal and replacement of the rotating air HPT front seal, HPT rotor blades, and No. 3 ball bearing. 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 October 29, 2026.

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-2026-8803; 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 CFM service material identified in this proposed AD, contact CFM GE Aviation Fleet Support, 1 Neumann Way, M/D Room 285, Cincinnati, OH 45125; phone: (877) 432-3272; email: [email protected]. 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

Alexei Marqueen, Aviation Safety Engineer, FAA, 2200 South 216th Street, Des Moines, WA 98198; phone: (781) 238-7178; 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 using a method listed under the ADDRESSES section. Include ``Docket No. FAA-2026-8803; Project Identifier AD-2026-00385-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 [[Page 58043]] 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 Alexei Marqueen, 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 was notified by the manufacturer of multiple reports of honeycomb separation from the surface of HPT inner stationary seals. A manufacturer investigation revealed that the affected HPT inner stationary seal may not have gone through the correct braze repair process, which could lead to a localized separation of the replaced honeycomb. This separation could affect the life of the HPT forward outer seal because missing honeycomb can induce a vibratory response in the HPT forward outer seal resulting in crack initiation in the seal teeth that propagate radially. This condition, if not addressed, could result in uncontained part release, damage to the engine, and damage to 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 material: CFM Service Bulletin (SB) SB CFM56-7B S/B 72-1096, Revision 01, dated January 21, 2026. CFM SB CFM56-5B S/B 72-1129, Revision 01, dated January 21, 2026. CFM SB CFM56-5C S/B 72-0813, Revision 01, dated June 9, 2026. This service material, differentiated by engine model, specifies procedures for performing a BSI of the rotating air HPT front seal for cracks and other damage. The FAA also reviewed the following service material: CFM SB CFM56-5C S/B 72-0811, Revision 02, dated January 19, 2026. CFM SB CFM56-7B S/B 72-1093, Revision 02, dated January 19, 2026. CFM SB CFM56-5B S/B 72-1125, Revision 02, dated January 19, 2026. This service material, differentiated by engine model, specifies procedures for inspecting the HPT inner stationary seal for honeycomb separation. 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 initial and repetitive BSIs of the rotating air HPT front seal for cracks and other damage and, depending on the results, replacement with a part eligible for installation. This proposed AD would also require removal and replacement of the affected HPT inner stationary seal. This proposed AD would also require inspection of the affected HPT inner stationary seal for honeycomb separation and, depending on the results of the inspection, removal and replacement of the rotating air HPT front seal, HPT rotor blades, and No. 3 ball bearing. Costs of Compliance The FAA estimates that this AD, if adopted as proposed, would affect 39 engines installed on airplanes of U.S. registry. The FAA estimates the following costs to comply with this proposed AD: Estimated Costs ---------------------------------------------------------------------------------------------------------------- Cost per Cost on U.S. Action Labor cost Parts cost product operators ---------------------------------------------------------------------------------------------------------------- BSI of rotating air HPT front seal.... 8 work-hours x $85 per $0 $680 $26,520 hour = $680. Replacement of HPT inner stationary 8 work-hours x $85 per 173,700 174,380 6,800,820 seal. hour = $680. Inspection of HPT inner stationary 8 work-hours x $85 per 0 680 26,520 seal. hour = $680. ---------------------------------------------------------------------------------------------------------------- The FAA estimates the following costs to do any necessary replacements that would be required based on the results of the proposed inspections. The agency has no way of determining the number of engines that might need these replacements: On-Condition Costs ---------------------------------------------------------------------------------------------------------------- Cost per Action Labor cost Parts cost product ---------------------------------------------------------------------------------------------------------------- Replacement of rotating air HPT front seal.... 8 work-hours x $85 per hour = $601,400 $602,080 $680. Replacement of HPT rotor blades (set)......... 8 work-hours x $85 per hour = 2,019,320 2,020,000 $680. Replacement of No. 3 ball bearing............. 8 work-hours x $85 per hour = 70,460 71,140 $680. ---------------------------------------------------------------------------------------------------------------- [[Page 58044]] 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 0