Bad bushings prompt Lycoming mandatory service bulletin

Lycoming issued Mandatory Service Bulletin No. 632A July 23 after receiving “isolated reports of connecting rod failures” resulting from a bushing becoming unseated from the small end of the connecting rod.  Failure of a connecting rod can lead to an uncommanded complete loss of engine power, Lycoming said.

The mandatory service bulletin calls for affected engines, and engines with “suspect” connecting rod assemblies, to be identified and quarantined within the next 10 hours of engine operation, followed by any necessary corrective action.

Lycoming said it “determined that a small number of bushings that did not conform with factory specifications may have been installed in connecting rods by a supplier,” with an additional small number of the bushings sold as spare parts.

The mandatory service bulletin lists the serial numbers of affected engines. Engines overhauled or repaired after Jan. 1, 2015, may also require inspection, as detailed in the mandatory service bulletin.

AOPA was contacted by members who have expressed concerns about the potential cost of the mandatory service bulletin’s requirements, and about the manufacturer’s guidance possibly becoming the basis for the FAA to issue an airworthiness directive (AD), said David Oord, AOPA senior director of regulatory affairs.

On Aug. 2, the association was able to convene on short notice a conference call with the FAA, Lycoming, and owners groups to work to put the problem in perspective and discuss an alternative recommendation that could mitigate the risk as well, or better, than the mandatory service bulletin, Oord said.

In a subsequent letter to the FAA, AOPA and the owners groups wrote that they were “disappointed that on the call, neither the FAA or Lycoming were willing to share any data or numbers of failures —a critical and essential element needed to better understand and quantify risk.”

The letter expressed regret that the FAA was unable, because of time constraints, to begin its review of the bushing problem by issuing an airworthiness concern sheet, “a process explored and agreed to at the FAA/Industry Engine Summit,” which AOPA believes “helps in developing a common understanding of the risk and notably quantify the number of failures or incidents that have occurred.” 

“If and when the Agency initiates a Corrective Action Review Board (CARB), we respectfully ask for it to consider the questions, concerns, and, most importantly, our recommended alternative means of compliance. If, after the CARB review and risk assessment, the risk rises above the line to warrant an Airworthiness Directive, given the short compliance time, we respectfully request that a global AMOC be approved simultaneously upon the issuance of the AD. The service bulletin’s time of compliance within the next 10 hours of engine operation will simply not afford the time needed to request and approve an AMOC after the issuance of an AD,” it said.

As discussions proceed, Lycoming has made available a set of frequently asked questions about the mandatory service bulletin on its website, noting that most of the company’s engines are not affected.

AOPA will continue to work to promote an open dialogue on the issue between all stakeholders to arrive at the most effective, cost-efficient process.