FAA Issues Directive Following Reports of In-Flight Shutdowns

The Federal Aviation Administration (FAA) has issued a new airworthiness directive (AD) affecting Lycoming engine models with specific connecting rod assemblies. This was prompted by a series of reports of con rod failures that caused uncontained engine breakdowns and in-flight shutdowns (IFSDs).

The directive mandates routine oil inspections to identify bronze metal particles, a potential indicator of connecting rod degradation. If any particles are detected, mechanics must perform additional checks on connecting rod bushings for signs of damage, misfit, movement, or excessive wear. Replacing compromised bushings with approved parts is required to prevent flight risks.

According to the FAA, around 16,000 engines on US aircraft, including popular IO-360 and O-320 models, fall under this directive. Inspections and potential bushing replacements are projected to incur significant costs, with estimates placing oil inspection expenses at approximately $235 per engine, connecting rod bushing inspections at $85, and bushing replacements at around $762 each.

For U.S. operators, the AD could result in roughly $3.76 million for oil inspections, $1.36 million for bushing inspections, and around $12.19 million for part replacements.

The manufacturer’s analysis concluded that certain connecting rod bushings installed between 2009 and 2017 were manufactured below specification, specifically in terms of outer diameter (OD). This substandard sizing leads to reduced retention in the connecting rod, allowing the bushing to shift within the rod assembly and suffer wear from piston forces. This misfit accelerates part failure, risking uncontained engine events.

The directive is set to take effect December 5, 2024. It does not specify an oil change frequency, so inspections can continue on each operator's maintenance schedule. Oil filters are typically evaluated at each oil change regardless of the AD, so it should not cause too much hassle unless anything concerning is found.

Given the significant risks posed, the FAA deems this AD essential for maintaining operational safety across affected Lycoming-powered aircraft.

FMI: www.faa.gov