AD Proposed for Lycoming Connecting Rod Bushings

The FAA has proposed adopting a new airworthiness directive (AD) for all Lycoming engines that have certain connecting rod assemblies installed. This proposed AD was prompted by several reports of connecting rod failures, which resulted in uncontained engine failure and in-flight shutdowns (IFSDs).

In 2017, FAA issued AD 2017-16-11, which required an inspection of connecting rods and replacement of affected connecting rod small end bushings per Lycoming Mandatory Service Bulletin (MSB) 632B dated August 4, 2017.

Since issuing the previous AD, a manufacturer investigation 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. This condition, if not corrected, could result in connecting rod failure with consequent uncontained engine failure, total engine power loss, IFSD, and possible loss of the aircraft.

This proposed AD would require 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 proposed AD would require replacement of the connecting rod bushings with parts eligible for installation. 

You can view this proposed AD here. Comments are due August 12, 2024.