As we go to press in early August, Lycoming, field shops and owners were struggling to clarify a service bulletin that requires inspection and possible replacement of connecting rod bushings in hundreds of Lycoming engines. The mandatory service bulletin—SB632—was announced on July 17, just ahead of AirVenture. Two weeks later, shops tell us they are still fielding calls from worried owners trying to understand the scope of the bushing issue.
According to Lycoming, the problem came to light after a number of engine failures—Lycoming isn’t saying how many—were traced to small-end connecting rod bushings that allow too much side-to-side play between the rod and piston, causing rapid wear and catastrophic damage. Further, fields shops were returning bushings shipped through the normal supply chain to Lycoming because they fit incorrectly. Two shops we spoke to—Penn Yan Aero and G&N Aircraft—reported partial or catastrophic failures in engines they had overhauled.