The FAA is adopting a new airworthiness directive (AD) for Lycoming Engines (Lycoming) model engines that have a certain connecting rod assemblies installed. This AD was prompted by several reports of connecting rod failures, which resulted in uncontained engine failure and in-flight shutdowns (IFSDs). This AD 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, this AD requires replacement of the connecting rod bushings with parts eligible for installation. The FAA is issuing this AD to address the unsafe condition on these products.
Background
The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to Lycoming model engines that have certain connecting rod assemblies installed. The NPRM published in the Federal Register on June 28, 2024 (89 FR 53911). The NPRM was prompted by several reports of connecting rod failures, which resulted in uncontained engine failure and IFSDs, and a manufacturer investigation where it was determined that affected connecting rod small end bushings may be installed on additional populations of Lycoming engines. The manufacturer also determined that degradation of the connecting rod small end bushings is detectable during oil change inspections. In the NPRM, the FAA proposed to require repetitive oil inspections for bronze metal particulates and, if found, additional inspections of the connecting rod bushings for damage ( e.g. deterioration, missing metal), proper fit, movement, and wear, and replacement if necessary. As terminating action to the connecting rod bushing inspections, the NPRM also proposed to require replacement of the connecting rod bushings with parts eligible for installation. The FAA is issuing this AD to address the unsafe condition on these products.
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