Lycoming’s crankshaft action has been expanded to include many four-cylinder versions, above.

Owners of Lycoming engines winced collectively in late February as they received notification that the company was asking 5100 of them to “retire” crankshafts in four-, six- and eight-cylinder engines. The fourth major crankshaft service bulletin or AD in three years had field shops scrambling to determine how many of engines would be affected and how customers would react.

Lycoming latest service bulletin—SB 569—calls for the mandatory retirement of 5100 serial-number specific crankshafts made between 1997 and 2002. Lycoming says it has found no failures in this lot of crankshafts but, nonetheless, wants owners to replace them at the first opportunity—overhaul or when the case is opened—but no later than February 21,…