Airworthiness Directives; Lycoming Engines

DEPARTMENT OF TRANSPORTATION <SUBAGY>Federal Aviation Administration</SUBAGY> <CFR>14 CFR Part 39</CFR> <DEPDOC>[Docket No. FAA-2025-1365; Project Identifier AD-2024-00684-E]</DEPDOC> <RIN>RIN 2120-AA64</RIN> <SUBJECT>Airworthiness Directives; Lycoming Engines</SUBJECT> <HD SOURCE="HED">AGENCY:</HD> Federal Aviation Administration (FAA), DOT. <HD SOURCE="HED">ACTION:</HD> Notice of proposed rulemaking (NPRM). <SUM> <HD SOURCE="HED">SUMMARY:</HD> The FAA proposes to supersede Airworthiness Directive (AD) 2024-21-02, which applies to Lycoming Engines (Lycoming) model engines that have certain connecting rod assemblies installed. AD 2024-21-02 requires repetitive oil inspections for bronze metal particulates and, if found, additional inspections of the connecting rod bushings for damage, proper fit, movement, and wear, and replacement if necessary. As terminating action to the connecting rod bushing inspections, AD 2024-21-02 also requires replacement of the connecting rod bushings with parts eligible for installation. Since the FAA issued AD 2024-21-02, the ship date range for potentially affected parts that may be subject to connecting rod failure has been expanded, and additional parts that are eligible for installation have been identified. This proposed AD would require the actions in AD 2024-21-02 and would require expanding the applicability. The FAA is proposing this AD to address the unsafe condition on these products. </SUM> <EFFDATE> <HD SOURCE="HED">DATES:</HD> The FAA must receive comments on this proposed AD by September 22, 2025. </EFFDATE> <HD SOURCE="HED">ADDRESSES:</HD> You may send comments, using the procedures found in 14 CFR 11.43 and 11.45, by any of the following methods: • <E T="03">Federal eRulemaking Portal:</E> Go to <E T="03">regulations.gov</E> . Follow the instructions for submitting comments. • <E T="03">Fax:</E> (202) 493-2251. • <E T="03">Mail:</E> U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue SE, Washington, DC 20590. • <E T="03">Hand Delivery:</E> Deliver to Mail address above between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. <E T="03">AD Docket:</E> You may examine the AD docket at <E T="03">regulations.gov</E> under Docket No. FAA-2025-1365; 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. <E T="03">Material Incorporated by Reference:</E> • For Lycoming material identified in this proposed AD, contact Lycoming Engines, 652 Oliver Street, Williamsport, PA 17701; phone: (800) 258-3279; website: <E T="03">lycoming.com/contact/knowledge-base/publications.</E> • 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. <FURINF> <HD SOURCE="HED">FOR FURTHER INFORMATION CONTACT:</HD> David Bergeron, Aviation Safety Engineer, FAA, 1701 Columbia Avenue, College Park, GA 30337; phone: (516) 228-7321; email: <E T="03">david.j.bergeron@faa.gov.</E> </FURINF> <SUPLINF> <HD SOURCE="HED">SUPPLEMENTARY INFORMATION:</HD> <HD SOURCE="HD1">Comments Invited</HD> 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 <E T="02">ADDRESSES</E> section. Include “Docket No. FAA-2025-1365; Project Identifier AD-2024-00684-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 <E T="03">regulations.gov</E> , including any personal information you provide. The agency will also post a report summarizing each substantive verbal contact received about this NPRM. <HD SOURCE="HD1">Confidential Business Information</HD> 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 David Bergeron, Aviation Safety Engineer, FAA, 1701 Columbia Avenue, College Park, GA 30337. Any commentary that the FAA receives which is not specifically designated as CBI will be placed in the public docket for this rulemaking. <HD SOURCE="HD1">Background</HD> The FAA issued AD 2024-21-02, Amendment 39-22869 (89 FR 86721, October 31, 2024), (AD 2024-21-02), for Lycoming model engines that have certain connecting rod assemblies installed. AD 2024-21-02 was prompted by several reports of connecting rod failures, which resulted in uncontained engine failure and in-flight shutdowns. AD 2024-21-02 requires repetitive oil inspections for bronze metal particulates and, if found, additional inspections of the connecting rod bushings for damage ( <E T="03">e.g.,</E> deterioration, missing metal), proper fit, movement, and wear, and replacement if necessary. As terminating action to the connecting rod bushing inspections, AD 2024-21-02 also required replacement of the connecting rod bushings with parts eligible for installation. The agency issued AD 2024-21-02 to prevent connecting rod failure. <HD SOURCE="HD1">Actions Since AD 2024-21-02 Was Issued</HD> Since the FAA issued AD 2024-21-02, the FAA was notified that there are Parts Manufacturer Approval (PMA) connecting rod bushings and connecting rod assemblies eligible for installation that were not included in AD 2024-21-02. Also, the manufacturer notified the FAA that the shipping date range for affected parts should be extended to include parts that were shipped between January 30, 2009, and September 9, 2021. The manufacturer also requested that credit be given to operators for the actions required in AD 2024-21-02 provided that the operators already accomplished AD 2017-16-11 and re-inspected any replacement connecting rod bushings received from Lycoming in accordance with the required actions of AD 2017-16-11. <HD SOURCE="HD1">FAA's Determination</HD> 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. <HD SOURCE="HD1">Material Incorporated by Reference Under 1 CFR Part 51</HD> The FAA reviewed Lycoming Mandatory Service Bulletin No. 630B, dated June 11, 2025, which specifies procedures for inspection of the connecting rod bushings for damage, proper fit, movement, and wear. 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 <E T="02">ADDRESSES</E> section. <HD SOURCE="HD1">Proposed AD Requirements in This NPRM</HD> This proposed AD would require all of the actions of AD 2024-21-02. This proposed AD would require repetitive oil inspections for bronze metal particulates and, if found, additional inspections of the connecting rod bushings for damage ( <E T="03">e.g.,</E> deterioration, missing metal), proper fit, movement, and wear, and replacement if necessary. As terminating action to the connecting rod bushing inspections, this proposed AD would require replacement of the connecting rod bushings with parts eligible for installation. This proposed AD would also expand the applicability by extending the shipping date range for affected parts. <HD SOURCE="HD1">Costs of Compliance</HD> The FAA estimates that this AD, if adopted as proposed, would affect 45,152 engines installed on airplanes of U.S. registry. The FAA estimates the following costs to comply with this proposed AD: <GPOTABLE COLS="5" OPTS="L2,i1" CDEF="s50,r50,12,12,12"> <TTITLE>Estimated Costs</TTITLE> <CHED H="1">Action</CHED> <CHED H="1">Labor cost</CHED> <CHED H="1">Parts cost</CHED> <CHED H="1"> Cost per product </CHED> <CHED H="1">Cost on U.S. operators</CHED> <ROW> <ENT I="01">Inspect oil</ENT> <ENT>2 work-hours × $85 per hour = $170</ENT> <ENT>$65</ENT> <ENT>$235</ENT> <ENT>$10,610,720</ENT> </ROW> <ROW> <ENT I="01">Inspect connecting rod bushings</ENT> <ENT>1 work-hour × $85 per hour = $85</ENT> <ENT>0</ENT> <ENT>85</ENT> <ENT>3,837,920</ENT> </ROW> <ROW> <ENT I="01">Replace connecting rod bushings (per bushing)</ENT> <ENT>4.5 work-hours × $85 per hour = $382</ENT> <ENT>380</ENT> <ENT>762</ENT> <ENT>34,405,824</ENT> </ROW> </GPOTABLE> <HD SOURCE="HD1">Authority for This Rulemaking</HD> 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 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Preview showing 10k of 21k characters. Full document text is stored and available for version comparison. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━